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Reefcrete : Reducing the environmental footprint of concrete for eco-engineering marine structures
Abstract
The ecological value of engineered marine structures can be enhanced by building-in additional habitat complexity. Pre-fabricated habitat units can be cheaply and easily cast from concrete into heterogeneous three-dimensional shapes and surface topographies, with proven ability to enhance biodiversity on artificial structures. The net ecological benefits of enhancement using concrete, however, may be compromised on account of its large environmental footprint and poor performance as substrate for many marine organisms. We carried out a pilot study to trial alternative cast-able “Reefcrete” concrete mixes, with reduced environmental footprints, for use in the marine environment. We used partial replacement of Portland cement with recycled ground granulated blast-furnace slag (GGBS), and partial replacement of coarse aggregate with hemp fibres and recycled shell material. We calculated the estimated carbon footprint of each concrete blend and deployed replicate tiles in the intertidal environment for 12 months to assess their performance as substrate for marine biodiversity. The hemp and shell concrete blends had reduced carbon footprints compared to both ordinary Portland cement based concrete and the GGBS based control concrete used in this study. At the end of the experiment, the hemp and shell blends supported significantly more live cover than the standard GGBS control blend. Taxon richness, particularly of mobile fauna, was also higher on the hemp concrete than either the shell or GGBS control. Furthermore, the overall species pool recorded on the hemp concrete was much larger. Community compositions differed significantly on the hemp tiles, compared to GGBS controls. This was largely explained by higher abundances of several taxa, including canopy-forming algae, which may have facilitated other taxa. Our findings indicate that the alternative materials trialled in this study provided substrate of equal or better habitat suitability compared to ordinary GGBS based concrete. Given the growing interest in ecological engineering of marine infrastructure, we propose there would be great benefit in further development of these alternative “Reefcrete” materials for wider application.
Supplementary resource (1)
... These materials include additives that lower the pH (e.g., ECOncrete; https://econcretetech.com) or reduce the environmental footprint of concrete (Reefcrete; Dennis et al. 2018). Other materials, such as BESE-elements (https://www.bese-products.com) ...
... Smith • Pruett MA17_Art10_Smith ARjats.cls July 4, 2024 13:47 that buffer pH for oysters may have negative effects on other taxa (Dennis et al. 2018). At scale, production of more durable substrates such as concrete has a greater environmental footprint (i.e., CO 2 production and water use) than natural substrates such as shell or rock (Dennis et al. 2018). ...
... July 4, 2024 13:47 that buffer pH for oysters may have negative effects on other taxa (Dennis et al. 2018). At scale, production of more durable substrates such as concrete has a greater environmental footprint (i.e., CO 2 production and water use) than natural substrates such as shell or rock (Dennis et al. 2018). Restoration actions that target climate change drivers should consider how these choices interact with the other logistical priorities and ES-based goals that inform restoration decision-making. ...
Oyster reef loss represents one of the most dramatic declines of a foundation species worldwide. Oysters provide valuable ecosystem services (ES), including habitat provisioning, water filtration, and shoreline protection. Since the 1990s, a global community of science and practice has organized around oyster restoration with the goal of restoring these valuable services. We highlight ES-based approaches throughout the restoration process, consider applications of emerging technologies, and review knowledge gaps about the life histories and ES provisioning of underrepresented species. Climate change will increasingly affect oyster populations, and we assess how restoration practices can adapt to these changes. Considering ES throughout the restoration process supports adaptive management. For a rapidly growing restoration practice, we highlight the importance of early community engagement, long-term monitoring, and adapting actions to local conditions to achieve desired outcomes.
... On the other hand, concrete can contain toxic metals and its cement portion can have high surface alkalinity (pH ~ 13) (Guilbeau et al., 2003; These chemical properties may also interfere with larval settlement, affect community structure and promote alkotolerant taxa, such as barnacles (Dooley et al., 1999;Guilbeau et al., 2003;Sella & Perkol-Finkel, 2015). To reduce the negative environmental effects of concrete basic surfaces, mixes using carbonated, silica-rich cements and combinations of these with Portland cement have been proposed to produce more ecologically sustainable, and pH-neutral concrete structures (Dooley et al., 1999;Guilbeau et al., 2003, Finkel & Sella, 2014Dennis et al., 2017;McManus et al., 2017;Perkol-Finkel et al., 2017). ...
... However, these units have relatively low roughness and a very low heterogeneity at diverse scales Corredor & Menendez, 2009), despite of ecological alternatives, such as modules of increased surface roughness and features such as pools, pits and crevices Coombes et al., 2015;Dyson & Yocom, 2015;Firth et al. , 2014. New concrete compositions have also been developed lately in order to increase the ecological properties of this artificial substratum (Dooley et al., 1999;Finkel & Sella, 2014;Sella & Perkol-Finkel, 2015;Dennis et al., 2017;McManus et al., 2017;Perkol-Finkel et al., 2017). Notwithstanding the fact that low-density materials such as oyster stone or other sandstones and conglomerates are not sufficiently stable for marine coastal constructions, results indicate that diversity can be increased if mixed substrata with variable roughness are included on breakwaters' surface during construction and repairs Cerrano et al., 2007;Dennis et al., 2017). ...
... New concrete compositions have also been developed lately in order to increase the ecological properties of this artificial substratum (Dooley et al., 1999;Finkel & Sella, 2014;Sella & Perkol-Finkel, 2015;Dennis et al., 2017;McManus et al., 2017;Perkol-Finkel et al., 2017). Notwithstanding the fact that low-density materials such as oyster stone or other sandstones and conglomerates are not sufficiently stable for marine coastal constructions, results indicate that diversity can be increased if mixed substrata with variable roughness are included on breakwaters' surface during construction and repairs Cerrano et al., 2007;Dennis et al., 2017). The application of ecological criteria to the abovementioned designs and materials, as well as others based on research, may help to reduce biodiversity losses and marine invasions, and, to sum up, create more ecologically sustainable structures in future marine construction. ...
Coastal ecosystems provide essential services that contribute to various human needs and environmental stability. However, these ecosystems are increasingly threatened by human activities, which have altered over 25% of global coastal surfaces, impacting species distribution, community structure, and overall ecosystem functioning.
This thesis focuses on analysing coastal development by investigating the physical and ecological impact of coastal defence structures, with a particular emphasis on the materials used. This includes a global estimation of the abundance of artificial shorelines and examining the impact of substratum type on benthic colonization, diversity, morphology, as well as the composition and structure of benthic populations and communities. This investigation encompasses intertidal and subtidal areas in exposed zones, as well as floating structures within marinas, which are known for being non-indigenous species hotspots and having high ecological footprint. In the latter case, a special focus is placed on exotic species and the effects of enclosed water bodies within marinas, which are considerably altered.
Our findings indicate that the impact of artificial structures is highly significant, covering nearly 20% of the world's coastlines, and is concentrated in geographically sensitive areas like lagoons, estuaries, bays, islands, and regions with high population densities. These ecosystems are facing substantial human-induced pressures, necessitating their immediate prioritization for protection. Additionally, both substratum type and roughness play pivotal roles in shaping communities and populations, influencing factors such as sessile community structure, limpet population morphology, and the prevalence of exotic species. Although the ecological importance of substratum type may be relatively limited in comparison to other physicochemical, geographical, and ecological variables, our results underscore the necessity of considering substratum type in the sustainable management of artificial coastal ecosystems. In general, predicting the impact of a specific structure at the time of its construction remains a complex challenge, which complicates the establishment of global eco-engineering measures. As a result, the outcomes of this thesis provide valuable insights in this field of study, potentially serving as a resource for future research and the management of projects and initiatives aimed at ecological restoration and eco-engineering.
... Furthermore, most marine constructions involve the use of concrete due to its versatility and durability (Becker et al., 2020) to withstand the harsh marine environment (e.g., extreme weather conditions, strong wave actions, and exposure to temperature fluctuations and corrosion due to high salinity of seawater). Concrete is, however, a poor substrate for biological recruitment because of its high surface alkalinity and leaching of metals over time (Dennis et al., 2018;McManus et al., 2018;Sedano et al., 2020). Studies have shown that communities on ACS are less diverse, and are typically colonized by invasive species (Ido & Shimrit, 2015). ...
... While concrete remains a popular choice in marine construction, research on environmentally-friendly construction materials for ecoengineering has predominantly focused on temperate regions. For instance, the partial replacement of cement with waste aggregates such as shells (Elavarasan et al., 2021), by-products from quarries (Chitkeshwar & Naktode, 2022), and hemp fibres (Dennis et al., 2018). In Malaysia, the production of eco-concrete materials for marine eco-engineering applications, and the associated technology, encompassing casting, moulding, and demoulding techniques, is still at an experimental stage. ...
... Concrete production significantly impacts the environment due to its use of aggregate and bindercomprising crushed stones, sand, gravel, and cement (Dennis et al., 2018). To mitigate these environmental concerns, earlier studies have introduced eco-concrete formulations integrating industrial waste materials like seashells, quarry dust, and GGBS (Dennis et al., 2018;Yee et al., 2022). ...
Poor quality habitat profiles of artificial coastal structures for biodiversity growth compared to natural shore have led researchers to utilize ecological engineering principles in creating habitat enhancement models mimicking the natural environment to help improve living conditions for marine organisms. Extensive global trials have been conducted with concrete formulations incorporating eco-friendly materials and recycled resources. However, eco-concrete production for marine environment use is still lacking in Malaysia. The technology involved in casting, moulding, and demoulding remains at the experimental stage, with unreported comparisons of different moulding materials used for casting geometrically complex habitat enhancement models. This study evaluated different casting, moulding, and demoulding techniques using locally produced eco-concrete. The main aim of this study is to determine the effect of different materials including plaster of Paris, drilling wood, expanded polystyrene, rubber foam, and vacuum forming on the mould production time, labour requirements and fabrication factors. Vacuum forming mould is highly preferred for its quick production time, less work, design uniformity, and ability to cast larger habitat enhancement models. However, the demoulding methods require improvements and further experimentation to ensure an easier demoulding process and reusability of the mould for long-term production.
... The use of crustose coralline algae yielded no lasting benefits [48]. The use of seashells was found to be beneficial by Dennis, et al. [49]; however, Potet, et al. [50] and Hanlon, et al. [51] found no significant effect. The use of hemp fibres [49] and ceramic waste [52] improved bioreceptivity, which could be attributed to the increased surface roughness caused by the aggregate. ...
... The use of seashells was found to be beneficial by Dennis, et al. [49]; however, Potet, et al. [50] and Hanlon, et al. [51] found no significant effect. The use of hemp fibres [49] and ceramic waste [52] improved bioreceptivity, which could be attributed to the increased surface roughness caused by the aggregate. ...
... Aggregate/filler Use of seashells [49] [ 50,51] Use of ceramic waste [52] Use of hemp fibres [49] Use of crustose coralline [48] Algae events. While mosses (and most other terrestrial colonising organisms) are highly droughttolerant, they do require water for the initial establishment and growth on the concrete surface. ...
Implementing nature in cities has great potential to improve urban liveability by providing ecosystem services, which can help mitigate heat stress, improve air quality, attenuate noise, and reduce rainwater runoff. However, widespread adoption of urban nature and green building typologies is still limited due to their costs, environmental impact, and space constraints. Bioreceptive concrete can form the basis of a new green building typology, where the concrete mixture is adjusted to allow for biological growth, specifically mosses, to occur on its surface. This literature review aims to give an overview of the current state of the art on bioreceptive concrete as a material in general and specifically the (potential) ecosystem services provided by the mosses growing on this bioreceptive concrete. This review shows that bioreceptivity can be achieved in concrete in several ways, including minor adjustments to standard concrete recipes. While quantitative data on the ecosystem services provided by mosses in an urban context is still limited, potential gains appear significant. The main challenges lie in the durable long-term development of mosses on the bioreceptive concrete and the valuation through quantification of the ecosystem services they provide. However, moss-receptive concrete shows promise as a new green building typology if these challenges are bridged.
... Furthermore, most marine constructions involve the use of concrete due to its versatility and durability (Becker et al., 2020) to withstand the harsh marine environment (e.g., extreme weather conditions, strong wave actions, and exposure to temperature fluctuations and corrosion due to high salinity of seawater). Concrete is, however, a poor substrate for biological recruitment because of its high surface alkalinity and leaching of metals over time (Dennis et al., 2018;McManus et al., 2018;Sedano et al., 2020). Studies have shown that communities on ACS are less diverse, and are typically colonized by invasive species (Ido & Shimrit, 2015). ...
... While concrete remains a popular choice in marine construction, research on environmentally-friendly construction materials for ecoengineering has predominantly focused on temperate regions. For instance, the partial replacement of cement with waste aggregates such as shells (Elavarasan et al., 2021), by-products from quarries (Chitkeshwar & Naktode, 2022), and hemp fibres (Dennis et al., 2018). In Malaysia, the production of eco-concrete materials for marine eco-engineering applications, and the associated technology, encompassing casting, moulding, and demoulding techniques, is still at an experimental stage. ...
... Concrete production significantly impacts the environment due to its use of aggregate and bindercomprising crushed stones, sand, gravel, and cement (Dennis et al., 2018). To mitigate these environmental concerns, earlier studies have introduced eco-concrete formulations integrating industrial waste materials like seashells, quarry dust, and GGBS (Dennis et al., 2018;Yee et al., 2022). ...
Poor quality habitat profiles of artificial coastal structures for biodiversity growth compared to natural shore have led researchers to utilize ecological engineering principles in creating habitat enhancement models mimicking the natural environment to help improve living conditions for marine organisms. Extensive global trials have been conducted with concrete formulations incorporating eco-friendly materials and recycled resources. However, eco-concrete production for marine environment use is still lacking in Malaysia. The technology involved in casting, moulding, and demoulding remains at the experimental stage, with unreported comparisons of different moulding materials used for casting geometrically complex habitat enhancement models. This study evaluated different casting, moulding, and demoulding techniques using locally produced eco-concrete. The main aim of this study is to determine the effect of different materials including plaster of Paris, drilling wood, expanded polystyrene, rubber foam, and vacuum forming on the mould production time, labour requirements and fabrication factors. Vacuum forming mould is highly preferred for its quick production time, less work, design uniformity, and ability to cast larger habitat enhancement models. However, the demoulding methods require improvements and further experimentation to ensure an easier demoulding process and reusability of the mould for long-term production.
... Despite the recognized importance of material choice, and the increasing effort into new eco-friendly materials, consistent information about how material type affects the colonizing biota on artificial structures is still lacking (but see Dodds et al., 2022). On the one hand, marked differences in epibenthos were reported when comparing different artificial materials (Brown, 2005;Dennis et al., 2018), different types of natural rocks (Canessa et al., 2019;Herbert and Hawkins, 2006) as well as natural to artificial substrates (Glasby, 2000). On the other, some studies failed to observe differences in epibenthos for similar comparisons (Caffey, 1982;Foley et al., 2014;Hsiung et al., 2020;Perkol-Finkel et al., 2012), suggesting there may be heterogeneity in the responses of marine organisms to material types (Dodds et al., 2022). ...
... Increase in situ ecological performance (Dodds et al., 2022), present work Eco-friendly concrete Reduce raw material demand (Dennis et al., 2018;McManus et al., 2018;Meyer, 2009) Eco-friendly concrete ...
... Reduce energy cost and carbon footprint (Cooke et al., 2020;Dennis et al., 2018;McManus et al., 2018) Autochthonous rocks Improve aesthetical value/ Greater consistency with cultural heritage Nordstrom, 2014) ...
... Eco-engineering has typically focused on enhancing the complexity of built structures and/or modifying materials such as concrete to be more eco-friendly (Dodds et al. 2022). For example: reducing the pH of concrete can benefit some colonists (Sella and Perkol-Finkel 2015); the inclusion of pozzolans (McManus et al. 2018), or recycled or natural materials such as hemp fibres or shells in its mix can reduce carbon emissions and landfill (Dennis et al. 2018, Dunn et al. 2019) and provide positive settlement cues for larvae (Burke 1986, Green et al. 2013, Pawlik 1992; and the replacement of aggregates with lightweight materials can pave the way for greater manipulation of structural complexity (Dunn et al. 2019). Yet, while eco-engineering studies have demonstrated positive effects of complexity and ecoblends on the species richness of at least some functional groups, few have simultaneously evaluated the relative importance of these two factors in orthogonal designs. ...
... Here, the interacting effect of complexity and concrete mixture on the colonisation of sessile biota was assessed. Based on the results of previous studies , Dennis et al. 2018, positive effects of complexity and biogenic concrete additives were predicted on the cover and species richness of colonising macrobiota, and consequently negative effects on the cover and proportionate contribution of NIS. Stronger effects were also predicted at higher tidal levels due to harsher environmental conditions and lower predation pressure. ...
... Unlike other studies (e.g. Dennis et al. 2018) there was no overarching positive effect of the inclusion of oyster shell on biodiversity and species richness. This may reflect the relatively low concentration of oyster shell used in mixtures here (50% of aggregate in this study compared to 50-100% in Dennis et al. 2018). ...
Marine artificial structures often support lower native species diversity and more non-indigenous species (NIS), but adding complex habitat and using bioreceptive materials have the potential to mitigate these impacts. Here, the interacting effects of structural complexity (flat, complex with pits) and concrete mixture (standard, or with oyster shell or vermiculite aggregate) on recruitment were assessed at two intertidal levels at an urban site. Complex tiles had less green algal cover, oyster shell mixtures had less brown (Ralfsia sp.) algal cover. At a low tidal elevation, the non-indigenous ascidian Styela plicata dominated complex tiles. Additionally, mixtures with oyster shell supported higher total cover of sessile species, and a higher cover of S. plicata. There were no effects of complexity or mixture on biofilm communities and native and NIS richness. Overall, these results suggest that habitat complexity and some bioreceptive materials may facilitate colonisation by a dominant invertebrate invader on artificial structures.
... Primary bioreceptivity is defined as the aptitude a material possesses for colonisation of biological life by virtue of the material composition and physical properties (Guillitte 1995) and, since the inception of this term, most research has focussed on lab-based studies, usually from a cultural heritage perspective with terrestrial conditions and biota (Sanmartín et al., 2021a). However, there are several studies that have looked to enhance the bioreceptivity of concrete in intertidal and subtidal settings, or to specifically attract marine organisms, by varying the binders (Perkol-Finkel and Sella 2014; Huang et al., 2016;McManus et al., 2018;Morin et al., 2018;Hayek et al., 2020;Natanzi et al., 2021;Ly et al., 2021), aggregates (Neo et al., 2009;Bedoya et al., 2014;Dennis et al., 2018;Hanlon et al., 2018;Ly et al., 2021;Potet et al., 2021) and additives used to modify its chemistry, pH (Guilbeau et al., 2003;Mos et al., 2019;Hayek et al., 2020;Hsiung et al., 2020), and surface porosity (Morin et al., 2018) and roughness (Pinheiro and Silva 2004;Neo et al., 2009;Sweat and Johnson 2013;Bedoya et al., 2014;Coombes et al., 2015;Dennis et al., 2018;Strain et al., 2018;MacArthur et al., 2019;Sedano et al., 2020). There may be some coastal settings or structures that are not appropriate for macroscale eco-engineering interventions, such as highly exposed shores, and so enhancing the bioreceptivity of the concrete material as a substrate for colonisation aims to maximise its ecological value in the absence of other habitat features. ...
... Primary bioreceptivity is defined as the aptitude a material possesses for colonisation of biological life by virtue of the material composition and physical properties (Guillitte 1995) and, since the inception of this term, most research has focussed on lab-based studies, usually from a cultural heritage perspective with terrestrial conditions and biota (Sanmartín et al., 2021a). However, there are several studies that have looked to enhance the bioreceptivity of concrete in intertidal and subtidal settings, or to specifically attract marine organisms, by varying the binders (Perkol-Finkel and Sella 2014; Huang et al., 2016;McManus et al., 2018;Morin et al., 2018;Hayek et al., 2020;Natanzi et al., 2021;Ly et al., 2021), aggregates (Neo et al., 2009;Bedoya et al., 2014;Dennis et al., 2018;Hanlon et al., 2018;Ly et al., 2021;Potet et al., 2021) and additives used to modify its chemistry, pH (Guilbeau et al., 2003;Mos et al., 2019;Hayek et al., 2020;Hsiung et al., 2020), and surface porosity (Morin et al., 2018) and roughness (Pinheiro and Silva 2004;Neo et al., 2009;Sweat and Johnson 2013;Bedoya et al., 2014;Coombes et al., 2015;Dennis et al., 2018;Strain et al., 2018;MacArthur et al., 2019;Sedano et al., 2020). There may be some coastal settings or structures that are not appropriate for macroscale eco-engineering interventions, such as highly exposed shores, and so enhancing the bioreceptivity of the concrete material as a substrate for colonisation aims to maximise its ecological value in the absence of other habitat features. ...
... Additionally, native molluscs may not have been able to detect chemical cues from a non-native oyster and so the use of non-native shellfish by-products may be redundant for native heterospecifics. Dennis et al. (2018) compared the bioreceptive performance of concretes made with different proportions of crushed whelk shell or hemp fibres to a concrete control with 10 mm coarse aggregate. The experimental tiles were deployed on the coast of Wales, UK, for 12 months and percentage cover, species richness and biomass was determined. ...
The proliferation of artificial concrete structures (ACSs) in the marine environment causes intertidal habitat loss and is a poor surrogate for natural rocky shores in terms of species richness, abundance, and community composition. As hard engineered coastlines increase, there is growing interest in how new concrete structures can facilitate improved habitat and biodiversity compared to existing concrete structures. Experiments that have substituted cement binder and aggregates in varying proportions and combinations have demonstrated that it is possible to enhance the primary bioreceptivity of concrete, either chemically or via microtopographical texture. This review synthesises key literature and identifies which concrete formulas prove most effective at enhancing bioreceptivity and those that have limited value, providing recommendations for coastal practitioners and for formulas that warrant further study. It is evident that the efficacy of chemical bioreceptivity of concrete is likely to be spatio-temporally limited (months) and enhancing surface roughness should be prioritised as a way to enhance colonisation. However, both chemical and physical methods require further investigation in within in situ marine settings for longer durations (>12 months).
... These have several applications for human activities, namely coastal protection, coastal development etc. These artificial structures represent new habitats for marine species and new approaches in eco-engineering [1][2][3][4][5][6][7] appearing to promote positive interactions between the biological compartment and the cement matrix. The cementitious materials are bio-receptive in the marine environment [8]. ...
... In order to understand the interaction between the mortar and the diatom C. closterium, the concentration of dSi, the diatoms growth and physiological parameters were measured under the four following different Conditions: The comparison of Conditions (1) and (2) aims to evaluate whether the dissolution of the mortar (measured in Condition (1)) supports the growth of diatoms (Condition (2)) and to evaluate the evolution of this interaction in time. Conditions (3) and (4) are controls for Conditions (1) and (2). Conditions (2) and (3) allow the comparison of diatom growth kinetics supported by mortar dissolution to a culture directly enriched with Si(OH) 4 . ...
... Conditions (3) and (4) are controls for Conditions (1) and (2). Conditions (2) and (3) allow the comparison of diatom growth kinetics supported by mortar dissolution to a culture directly enriched with Si(OH) 4 . Condition (4) allows the evolution of the growth of C. closterium to be evaluated under Si-deficient conditions. ...
Man-made infrastructures are wildly developed in many coastal ecosystems. Understanding and improving the positive interactions between concrete maritime infrastructures and biological components remains one of the ecological engineering challenges. The aim of this study is to evaluate the ability of a benthic diatom species, Cylindrotheca closterium (C. closterium), to use the mortar of artificial marine structure as a silicon source for their own metabolism and growth. Diatoms are the dominant class of primary producer in many ecosystems. Diatoms need to absorb dissolved silica (dSi) in the form of Si(OH)4 in order to synthesize their cell wall (the frustule). Batch cultures of C. closterium were performed under silicon limitation with or without the presence of mortar. First, the dissolution kinetics of silica from mortar in seawater were studied. Thereafter, the interaction between microalgae and dissolution kinetic properties were explored along with diatom biological parameters (Growth, biogenic silica per cell, biovolume, silicification degree and photosynthetic parameters). The dSi released by the mortar increases from the first days in the medium. Subsequently the Si(OH)4 concentration decreased when microalgae were introduced into the medium associated to a parallel increase of the biogenic silica showing that cells are able to use dSi from the mortar to elaborate their frustule. The study also identified modifications of some of morpho-functional traits of C. closterium to maintain growth under limited Si conditions. This study shows how the benthic diatom C. closterium are able to benefit and acclimate from silica input provided by immersed artificial structures.
... Given limitations surrounding use of shell substrate, a diversity of natural and artificial substrates are now being applied to oyster reef restoration (Goelz et al., 2020). These include, but are not limited to: other bivalve shells (e.g., scallop shells, surf clams), crushed limestone or rock, standard concrete (e.g., oyster castles), concrete with various additives often aimed at lowering pH or resource consumption during manufacture (e.g., Econcrete, Sella et al., 2018;Reefcrete;Dennis et al., 2018) and biodegradable products such as BESE-elements, a zigzag mesh constructed of a potato waste polymer that can be layered to produce a high surface-area structure with protective microhabitat (Herbert et al., 2018;Temmink et al., 2020). These substrates vary in material type and structural attributes, which interact with environmental factors to determine oyster reef development, growth and ecosystem service provision. ...
... The higher alkalinity of concrete (pH of 12-13) than oyster shell (pH 9) may assist in safeguarding marine organisms from increasing ocean acidification, especially during the vulnerable juvenile stages (Mos et al., 2019). However, concerns have been raised over negative impacts of a high alkalinity on the development of other oyster reef-associated organisms (Guilbeau et al., 2003;Müllauer et al., 2015;Dennis et al., 2018). The high alkalinity of concrete may also interfere with the natural process of species adapting to lower pH over time (Amaral et al., 2012;Cole et al., 2016;Gray et al., 2019). ...
... Natural materials typically used in the construction of lowlying reefs (i.e., oyster shells, crushed rock, limestone and clam shells) are generally cheap, as they do not require manufacturing, with their cost instead limited to transportation and deployment, and in some instances also extraction, sterilization (e.g., boiling or UV treatment of shell to remove parasites) and packaging (Goelz et al., 2020). Concrete and associated products such as Reefcrete and Econcrete are typically more expensive due to the manufacturing processes (Flower and Sanjayan, 2007;Marinković et al., 2010;Dennis et al., 2018), as are bespoke products such as BESE-elements that are manufactured at smaller economies of scale. ...
Globally, there is growing interest in restoring previously widespread oyster reefs to reinstate key ecosystem services such as shoreline protection, fisheries productivity and water filtration. Yet, since peak expiration of oysters in the 1800s, significant and ongoing environmental change has occurred. Estuaries and coasts are undergoing some of the highest rates of urbanization, warming and ocean acidification on the planet, necessitating novel approaches to restoration. Here, we review key design considerations for oyster reef restoration projects that maximize the probability that they will meet biological and socio-economic goals not only under present-day conditions, but into the future. This includes selection of sites, and where required, substrates and oyster species and genotypes for seeding, not only on the basis of their present and future suitability in supporting oyster survival, growth and reproduction, but also based on their match to specific goals of ecosystem service delivery. Based on this review, we provide a road map of design considerations to maximize the success of future restoration projects.
... The use of SCMs for marine and coastal structures has also been investigated, though to a lesser extent in this field, showing common SCMs such as fly ashes, ground granulated blast furnace slags (GGBFS, also referred as slags), pozzolanas and limestones. More recent studies include the partial replacement of coarse aggregate with hemp fibres and recycled shell material (Dennis et al., 2018) or the use of local materials, such as fine marine sediments dredged from ports (Achour et al., 2019) and sea sand as substitutes of fine aggregates of concrete mixes for artificial reefs (Rupasinghe et al., 2024). ...
... Recent studies include alternative materials to reduce carbon footprint of concrete production or in case of shortages of these aggregates. For example, the partial replacement of coarse aggregate with hemp fibres and recycled shells, which also enhances the biological colonization of concrete (Dennis et al., 2018). Favorable early colonization was observed in concretes containing limestone and granite aggregates (Natanzi et al., 2021). ...
In the last two decades, Eco-engineering has emerged to mitigate and compensate the environmental impacts of man-made structures while integrates benefits to society, being concrete the most widely alternative material used to natural rocks for construction of artificial coastal structures. Over the past three decades, an extensive literature has documented different supplementary cementitious materials (SCMs) to reduce CO2 emissions from Portland cement, with common SCMs used in marine and coastal structures such as fly ashes, ground granulated blast furnace slags, pozzolanas and limestones. However, there is a need to further investigate the suitability of SCMs for the construction of Low-Crested Structures (LCS) to decrease carbon footprint from concrete production and improve the bioreceptivity of concrete armor units during the breakwater lifetime. A literature review conducted in this study shows several advantages of slag cements compared to other SCMs to reduce carbon emissions and enhance biological colonization and durability of concrete submerged in seawater, identifying surface roughness as the most effective factor in design of bioreceptive concrete. This study also highlights the importance of the type and quantity of cement used in concrete mixes to reduce carbon footprint of the manufacture of concrete armor units of LCS and the implementation of long-term monitoring plans to fully understand the functioning of local communities that develop on concrete surfaces of artificial structures, and thus, to improve the integration of environmental parameters in the field of coastal engineering.
... Common materials for ARs include quarry rocks (Palmer-Zwahlen and Aseltine, 1994), rocky conglomerates (Baine, 2001;Feary et al., 2011), bivalve shells (Fabi et al., 2011), wood (Alam et al., 2020) and organic residues like banana particles waste (Mat Jusoh et al., 2018). 2 Composite materials. These are produced by combining two or more substances with varying properties, such as cement (Baine, 2001;Dennis et al., 2018), metal (Mercader et al., 2017;Scarcella et al., 2015), polymers (Omar, 1995), ceramics (Kalam et al., 2018) and fibreglass (Kheawwongjan and Kim, 2012). Cement is notably preferred for its suitability and cost-effectiveness in AR manufacturing, facilitating the creation of specific designs through casting moulds or AM. ...
... Regarding the selection of materials presented in Table 8, cementitious mortar was the most used, featuring in ten AR cases (62%); ceramics were used in 5 (31%); and geopolymers and polymers in 1 (6%). The data indicates a trend towards incorporating recycled materials (Reef Design Lab, 2018), bioresidues such as seashells (Goad, 2022;Yoris-Nobile et al., 2023), bio-based resins derived from bamboo (Schofield, 2020a) and marine cement aimed to replace Portland cement, the primary source of CO 2 emission in cement productions (Dennis et al., 2018). The aggregates include pozzolans (Meyer, 2009) (Suchin, 2018) used polylactic acid (PLA), a biodegradable plastic known for its minimal negative environmental impact, although its degradability remains under question (Tarazi et al., 2019). ...
Purpose
The purpose of this paper is to review cases of artificial reefs built through additive manufacturing (AM) technologies and analyse their ecological goals, fabrication process, materials, structural design features and implementation location to determine predominant parameters, environmental impacts, advantages, and limitations.
Design/methodology/approach
The review analysed 16 cases of artificial reefs from both temperate and tropical regions. These were categorised based on the AM process used, the mortar material used (crucial for biological applications), the structural design features and the location of implementation. These parameters are assessed to determine how effectively the designs meet the stipulated ecological goals, how AM technologies demonstrate their potential in comparison to conventional methods and the preference locations of these implementations.
Findings
The overview revealed that the dominant artificial reef implementation occurs in the Mediterranean and Atlantic Seas, both accounting for 24%. The remaining cases were in the Australian Sea (20%), the South Asia Sea (12%), the Persian Gulf and the Pacific Ocean, both with 8%, and the Indian Sea with 4% of all the cases studied. It was concluded that fused filament fabrication, binder jetting and material extrusion represent the main AM processes used to build artificial reefs. Cementitious materials, ceramics, polymers and geopolymer formulations were used, incorporating aggregates from mineral residues, biological wastes and pozzolan materials, to reduce environmental impacts, promote the circular economy and be more beneficial for marine ecosystems. The evaluation ranking assessed how well their design and materials align with their ecological goals, demonstrating that five cases were ranked with high effectiveness, ten projects with moderate effectiveness and one case with low effectiveness.
Originality/value
AM represents an innovative method for marine restoration and management. It offers a rapid prototyping technique for design validation and enables the creation of highly complex shapes for habitat diversification while incorporating a diverse range of materials to benefit environmental and marine species’ habitats.
... Concrete is the most commonly used material in artificial structures (Bhattacharyya and Deb 2022) but has a more homogenous surface (Coombes et al. 2015) and higher surface alkalinity than rock (Sella and Perkol-Finkel 2015), and also leaches metals (McManus et al. 2018). Properties of concrete are, however, easily modified through additives to the concrete mix (Dennis et al. 2018, Dhir and Dyer 1996, Dunn et al. 2019, and/or adding fine scale microtexture (mm-mm scale) and larger scale topographic complexity (cm-scale) during the manufacturing process, which can benefit colonisation of target marine biota , Coombes et al. 2015, Kosov� a et al. 2023, MacArthur et al. 2019. For example, the inclusion of pozzolans, recycled or natural materials like oyster shells in the concrete mix can provide positive settlement cues for larvae and reduce the environmental footprint of standard concrete (Anderson 1996, Dennis et al. 2018, Dunn et al. 2019. ...
... Properties of concrete are, however, easily modified through additives to the concrete mix (Dennis et al. 2018, Dhir and Dyer 1996, Dunn et al. 2019, and/or adding fine scale microtexture (mm-mm scale) and larger scale topographic complexity (cm-scale) during the manufacturing process, which can benefit colonisation of target marine biota , Coombes et al. 2015, Kosov� a et al. 2023, MacArthur et al. 2019. For example, the inclusion of pozzolans, recycled or natural materials like oyster shells in the concrete mix can provide positive settlement cues for larvae and reduce the environmental footprint of standard concrete (Anderson 1996, Dennis et al. 2018, Dunn et al. 2019. Efforts to improve the ecological value of marine infrastructure by incorporating ecological principles into their design (e.g. through the manipulation of properties of concrete) is known as ecological engineering (Bergen et al. 2001, Mitsch andJorgensen 1989), though a diverse range of terminology exists (e.g. ...
Concrete infrastructure in coastal waters is increasing. While adding complex habitat and manipulating concrete mixtures to enhance biodiversity have been studied, field investigations of sub-millimetre-scale complexity and substrate colour are lacking. Here, the interacting effects of 'colour' (white, grey, black) and 'microtexture' (smooth, 0.5 mm texture) on colonisation were assessed at three sites in Australia. In Townsville, no effects of colour or microtexture were observed. In Sydney, spirorbid polychaetes occupied more space on smooth than textured tiles, but there was no effect of microtexture on serpulid polychaetes, bryozoans and algae. In Melbourne, barnacles were more abundant on black than white tiles, while serpulid polychaetes showed opposite patterns and ascidians did not vary with treatments. These results suggest that microtexture and colour can facilitate colonisation of some taxa. The context-dependency of the results shows that inclusion of these factors into marine infrastructure designs needs to be carefully considered.
... shell, mineral, hemp fiber, coral, and crustose coralline algae rubble) or admixtures (e.g. pozzolans) that promote recruitment (Lee et al. 2009, Neo et al. 2009, Huang et al. 2016, Dennis et al. 2018, Natanzi et al. 2021. However, which materials are more or less favorable for any given community and which material traits promote recruitment is not well understood. ...
... We prepared concrete mix 1 (CM1) using city and statelevel construction specifications for bridge substructures and precast concrete, such as dock pilings. We then used the designs of environmentally friendly marine concretes to prepare concrete mix 2 (CM2; Perkol-Finkel & Sella 2014, Huang et al. 2016, Dennis et al. 2018). CM1 contained 10 % silica fume, 25 % class F fly ash, and 65 % type I/II Portland cement by mass. ...
Hard-substrate epibionts have an important role in estuaries; they improve water quality, form habitat, and influence food webs. Coastal urbanization converts natural hard substrates (e.g. oyster reefs and rocky shorelines) into artificial structures, which do not support the same hard-substrate communities. Material composition may be a driving factor behind this difference, so interest is growing in how material type can be used to create marine structures that serve an ecological role. However, this research has mainly been restricted to rocky shorelines. We address this gap by asking how material type affects hard-substrate assemblages in a sedimentary Atlantic habitat. We deployed panels of wood, PVC, and 2 different concrete mixes in Galveston Bay, TX, USA, for 3 mo. Unique communities formed on different materials, which may alter ecosystem services if scaled to large development projects. Material type had a limited effect on richness but strongly affected total cover and biomass, both of which are important metrics for ecosystem function. Across all measures, one concrete mix showed the most potential to serve a beneficial ecological role. Our findings highlight the importance of material type in the design of marine structures in sedimentary Atlantic habitats.
... However, a few researchers have recently taken this work to a new level and started introducing nutrients such as amino acids inside the concrete, which might work as an attractant for benthic organisms [12,13]. In another study, Dennis et al. [14] used hemp fiber as a partial alternative to aggregate along with a ground granulated blast furnace slag (GGBS) as a partial replacement of cement, showing higher algal concentrations and mean live covers compared with normal concrete and other concrete types without hemp fiber. Although the researchers did not mention nutrients leaching out of the concrete, a similar phenomenon to that observed by Mohamad et al. [13] could be assumed in this study, which may have resulted in higher algal growth. ...
... However, a few researchers have recently taken work to a new level and started introducing nutrients such as amino acids inside the crete, which might work as an attractant for benthic organisms [12,13]. In another st Dennis et al. [14] used hemp fiber as a partial alternative to aggregate along with a gr granulated blast furnace slag (GGBS) as a partial replacement of cement, showing h algal concentrations and mean live covers compared with normal concrete and other crete types without hemp fiber. Although the researchers did not mention nutrients l ing out of the concrete, a similar phenomenon to that observed by Mohamad et al could be assumed in this study, which may have resulted in higher algal growth. ...
Through the bokashi process, fermented leaves were incorporated as a partial alternative
to sand in concrete to produce a concrete type that could be a prospective artificial reef material. The specimens were checked in small pools where algae—Chlorella vulgaris—was added and checked for growth. The results showed that the concrete with 20% bokashi fermented leaves (BFL) by weight of cement had 40 times higher algal coverage on the surface by the end of 35 days. Concrete with 2% bokashi fermented leaves (BFL), however, tended to increase the algal coverage by only 3 times.
... This intensified storm surges together with global sea level rise will result in reduced crest freeboard of existing coastal defence infrastructures and make them more vulnerable to catastrophic flooding with extreme wave overtopping and wave runup events [5][6][7][8]. Conventional engineering approaches resulted in armouring of coastlines with hard engineered structures including seawalls and breakwaters in order to provide protection from flooding and erosion, which are becoming increasingly unsustainable due to their costly maintenance and loss of environmental biodiversity [9][10][11][12][13][14]. Concrete as a material choice has been widely favoured for building coastal defences due to its ease of casting into heterogeneous three-dimensional shapes and surface topographies [15]. However, for every 1000 kg of Portland cement, between 900 to 1100 kg of CO 2 is emitted [16]. ...
... However, for every 1000 kg of Portland cement, between 900 to 1100 kg of CO 2 is emitted [16]. Furthermore, the high surface alkalinity (pH 12-13) and leaching metals can impair settlement of marine organisms and contribute to pollution mixing in the nearshore zone [15,17]. Coastal vegetations are sustainable and can adapt to the natural ecosystem of the coastal region without intrusive behaviour [10]. ...
Increased intensity of extreme climatic events and natural hazards, combined with sea level rise due to global warming, has increased the vulnerability of nearshore and coastal regions to extreme flooding and erosion. The existing hard-engineered infrastructures for flood protection are mainly built from concrete with very high carbon emissions throughout their life cycle. In recent years, the application of nature-based solutions to tackle adverse climatic events has received attention. Nearshore vegetations such as salt marshes and mangroves have proven to attenuate incoming wave energy, thereby reducing wave runup and overtopping at coastal defences. The effectiveness of seagrass vegetation on wave runup attenuation remains less studied. The aim of this physical modelling study was to investigate the performance of prototype seagrass vegetations on wave runup reductions, for a wide range of wave conditions. Results of this study showed that the seagrass vegetation was effective in reducing wave runup on a ‘bare’ beach. It was found that the location of the vegetation patch within the surfzone and inner-surf zone can play a key role in wave energy dampening. The vegetation type, and packing density also play a significant role in determining the effectiveness of seagrass in wave energy mitigation.
... For example, ECOncrete® includes the addition of marine products including oyster shells and other environmentally sensitive technologies, reducing the environmental footprint of ARs (Walles et al. 2016;Perkol-Finkel et al. 2018;Georges et al. 2021;Vivier et al. 2021). Other initiatives include testing recycled ground granulated blast-furnace slag (GGBS), and partial replacement of coarse aggregate with hemp fibres and recycled shell material that reduced the carbon footprint and incorporated carbon storage (Dennis et al. 2018). After 12 months the hemp and shell concrete supported significantly more cover by living organisms than the standard GGBS control blend. ...
... Taxon richness, especially of mobile fauna, and the overall species pool were also higher on the hemp concrete. These alternative materials were considered to be of equal or better habitat suitability compared to ordinary GGBS based concrete (Dennis et al. 2018). ...
Te Tauihu (Top of the South Island, NZ) Councils (MLDC, NLCC, TLDC) sought advice on options for activities or actions to reverse the decline in state of coastal and marine habitats to build resilience in these habitats likely to be impacted by climate change. An Envirolink medium advice grant was used to review local reasons for restoration, summarise existing relevant marine restoration techniques and identify methods or species relevant for Te Tauihu highlighting ‘shovel-ready’ projects. Shellfish restoration was considered the top priority because of the areal extent of historic degradation. Restoration of such habitats are very likely to produce additional benefits to fisheries production (shellfisheries, fishes), and contribute to reducing climate change risks (through carbon sequestration and through the greater resilience provided by healthy ecosystems). Successful restoration of shellfish and seaweeds/grasses is more likely if soft sediment habitats can also be protected from benthic disturbance and if terrestrial sediment discharge into coastal marine areas is reduced. Recent restoration successes (e.g., green-lipped mussels, saltmarsh) and increasing knowledge of climate change risks provide encouragement and impetus to continue broadening the scope and scale of marine restoration efforts in Te Tauihu.
... (Georges et al., 2021). De plus, cela permet de réduire l'empreinte environnementale du béton en réduisant la proportion de sable nécessaire à sa conception (Dennis et al., 2018) l'avantage écologique engendré par l'addition de rugosité à la surface de la dallette ; ces microhabitats ont permis au biofilm de se développer par patchs dans des conditions favorables. Le biofilm situé dans ces niches présentait un statut physiologique, une capacité de production et une efficacité photosynthétique plus élevés que sur le reste de la structure. ...
... (Shim & Singh, 1988;Losi et al., 2013;Baux et al., 2017Baux et al., , 2019 Figure 63) représente également une avancée significative pour l'évaluation de cette fonction écologique sur des habitats artificiels. L'étude des producteurs primaires associé aux récifs artificiels est encore trop peu développée (Pennesi & Danovaro, 2017;Dennis et al., 2018;Sheng et al., 2018;Tsiamis et al., 2020 Les écosystèmes productifs ne sont pas toujours associés à une biodiversité importante, la relation entre ces indicateurs varie selon les dimensions de la diversité et le niveau des contraintes externes (Brun et al., 2019). Par exemple, la diversité phylogénétique peut être importante dans les écosystèmes avec peu de contraintes externes en promouvant des stratégies complémentaires, mais sous des contraintes externes, les organismes les plus adaptés peuvent être sélectionnés et la diversité sera réduite (Zobel & Pärtel, 2008;Brun et al., 2019). ...
L’accroissement des pressions anthropiques sur les écosystèmes marins et côtiers, en particulier en Manche, provoquent des modifications des habitats, des écosystèmes et des différentes fonctions écosystémiques associées. La construction d’ouvrages maritimes et côtiers tels que les digues ou des ouvrages portuaires ainsi que l’émergence de plusieurs projets d’implantation d’éoliennes off-shore est en augmentation constante sur les côtes de la Manche française. Avec ces différents projets, la bétonisation de certains habitats devient inévitable, il est donc primordial d’évaluer leurs impacts écosystémiques, et, si possible, de les limiter. Le projet MARINEFF est né dans ce contexte, il vise à concilier développement humain et bénéfice écologique. Le développement de ces nombreuses infrastructures côtières crée de nouveaux habitats. L’objectif de ces travaux a été d’évaluer les processus de colonisation biologique à différentes échelles ainsi que certaines fonctions écologiques comme la production primaire sur différents types d’infrastructures marines en conditions contrôlées et en situation in situ dans deux sites La Rade de Cherbourg et la baie de Seine. Les mesures de fluorescence modulée (PAM) réalisées sur les différents compartiments de producteurs primaires benthiques ont permis d’évaluer la fonction de production primaire et son évolution en fonction des forçages testés ou observés. Une part importante de ce travail s’est concentrée sur l’étude du microphytobenthos de substrat dur, sa croissance, sa photobiologie en relation avec le type de substrat colonisé, sa structure de surface et l’impact de différents forçages sur ces paramètres. A une plus grande échelle, le développement des communautés benthiques a également été caractérisé sur les deux sites et sur différentes infrastructures. Des mesures de production primaire in situ associées à des mesures de biodiversité et de PAM ont permis de décrire les processus de colonisation d’infrastructures artificielles et d’évaluer leur efficacité. Ces travaux apportent une nouvelle vision à l’écologie benthique associée aux substrats durs artificiels et apportent des estimations fiables de l’impact de ces structures sur l’écosystème.
... This intensified storm surges together with global sea level rise will result in reduced crest freeboard of existing coastal defence infrastructures and make them more vulnerable to catastrophic flooding with extreme wave overtopping and wave runup events [5][6][7][8]. Conventional engineering approaches resulted in armouring of coastlines with hard engineered structures including seawalls and breakwaters in order to provide protection from flooding and erosion, which are becoming increasingly unsustainable due to their costly maintenance and loss of environmental biodiversity [9][10][11][12][13][14]. Concrete as a material choice has been widely favoured for building coastal defences due to its ease of casting into heterogeneous three-dimensional shapes and surface topographies [15]. However, for every 1000 kg of Portland cement, between 900 to 1100 kg of CO2 is emitted [16]. ...
... However, for every 1000 kg of Portland cement, between 900 to 1100 kg of CO2 is emitted [16]. Furthermore, the high surface alkalinity (pH 12-13) and leaching metals can impair settlement of marine organisms and contribute to pollution mixing in the nearshore zone [15,17]. Coastal vegetations are sustainable and can adapt to the natural ecosystem of the coastal region without intrusive behaviour [10]. ...
Increased intensity of extreme climatic events and natural hazards, combined with sea level rise due to global warming, has increased the vulnerability of nearshore and coastal regions to extreme flooding and erosion. The existing hard-engineered infrastructures for flood protection are mainly built from concrete with very high carbon emissions throughout their life cycle. In recent years, the application of nature-based solutions to tackle adverse climatic events has received attention. Nearshore vegetations such as salt marshes and mangroves have proven to attenuate incoming wave energy, thereby reducing wave runup and overtopping at coastal defences. The effectiveness of seagrass vegetation on wave runup attenuation remains less studied. The aim of this physical modelling study was to investigate the performance of prototype seagrass vegetations on wave runup reductions, for a wide range of wave conditions. Results of this study showed that the seagrass vegetation was effective at reducing wave runup. It was found that the location of the vegetation patch within the surfzone and inner-surf zone can play a key role in wave energy dampening. The vegetation type, and packing density also play a significant role in determining the effectiveness of seagrass in wave energy mitigation.
... Effects of material types on marine colonisation have been studied for many years, initially to inform the development of antifouling technologies (Cao et al., 2011). More recently, studies have focused on manipulating material composition and surface chemistry (Dennis et al., 2018;Natanzi et al., 2021;Perkol-Finkel and Sella, 2014) to develop multifunctional structures that benefit both humans and nature . Irrespective of their aim, most studies have focused on contrasting pairs or small subsets of materials at one or few locations (Chase et al., 2016;Norris, 1991). ...
... Despite records of increased density and diversity of colonising species on eco-friendly materials (Dennis et al., 2018;Perkol-Finkel and Sella, 2014), we found no significant difference in abundance of the settling community between control and eco-friendly concretes. In situ, the constant flushing of substrate surfaces may dilute concrete leachates into the surrounding water column, diminishing the effect of reduced pH (McManus et al., 2018;Schaefer et al., 2020). ...
Urbanisation of coastal areas and growth in the blue economy drive the proliferation of artificial structures in marine environments. These structures support distinct ecological communities compared to natural hard substrates, potentially reflecting differences in the materials from which they are constructed. We undertook a meta-analysis of 46 studies to compare the effects of different material types (natural or eco-friendly vs. artificial) on the colonising biota on built structures. Neither the abundance nor richness of colonists displayed consistent patterns of difference between artificial and natural substrates or between eco-friendly and standard concrete. Instead, there were differences in the abundance of organisms (but not richness) between artificial and natural materials, that varied according to material type and by functional group. When compared to biogenic materials and rock, polymer and metal supported significantly lower abundances of total benthic species (in studies assessing sessile and mobile species together), sessile invertebrates and corals (in studies assessing these groups individually). In contrast, non-indigenous species were significantly more abundant on wood than metal. Concrete supported greater abundances of the general community, including habitat-forming species, compared to wood. Our results suggest that the ecological requirements of the biological community, alongside economic, logistic and engineering factors should be considered in material selection for multifunctional marine structures that deliver both engineering and ecological (enhanced abundance and diversity) benefits.
... (Georges et al., 2021). De plus, cela permet de réduire l'empreinte environnementale du béton en réduisant la proportion de sable nécessaire à sa conception (Dennis et al., 2018) l'avantage écologique engendré par l'addition de rugosité à la surface de la dallette ; ces microhabitats ont permis au biofilm de se développer par patchs dans des conditions favorables. Le biofilm situé dans ces niches présentait un statut physiologique, une capacité de production et une efficacité photosynthétique plus élevés que sur le reste de la structure. ...
... (Shim & Singh, 1988;Losi et al., 2013;Baux et al., 2017Baux et al., , 2019 Figure 63) représente également une avancée significative pour l'évaluation de cette fonction écologique sur des habitats artificiels. L'étude des producteurs primaires associé aux récifs artificiels est encore trop peu développée (Pennesi & Danovaro, 2017;Dennis et al., 2018;Sheng et al., 2018;Tsiamis et al., 2020 Les écosystèmes productifs ne sont pas toujours associés à une biodiversité importante, la relation entre ces indicateurs varie selon les dimensions de la diversité et le niveau des contraintes externes (Brun et al., 2019). Par exemple, la diversité phylogénétique peut être importante dans les écosystèmes avec peu de contraintes externes en promouvant des stratégies complémentaires, mais sous des contraintes externes, les organismes les plus adaptés peuvent être sélectionnés et la diversité sera réduite (Zobel & Pärtel, 2008;Brun et al., 2019). ...
Increasing anthropogenic pressures on marine and coastal ecosystems, particularly in the English Channel, are causing changes in habitats, ecosystems and the various associated ecosystem functions. The construction of marine and coastal structures such as dikes as well as the emergence of several projects to install offshore wind turbines is constantly increasing on the French coasts of the English Channel. With these different projects, the artificialization of certain habitats becomes inevitable, so it is essential to assess their ecosystem impacts, and, if possible, to limit them. The MARINEFF project was born in this context, it aims to reconcile human development and ecological benefit. The development of these many coastal infrastructures can also make it possible to create new habitats. The objective of this PhD is to assess biological colonization processes at different scales as well as certain ecological functions such as the primary production on different types of marine infrastructures under controlled conditions and in situ situations on two site the Rade of Cherbourg and the Bay of Seine. Modulated fluorescence (PAM) measurements carried out on the different compartments of benthic primary producers made it possible to evaluate the primary production function and its evolution according to the forcing’s tested or observed. An important part of this PhD focused on the study of hard substrate microphytobenthos, its growth, its photobiology in relation to the type of colonized substrate, its surface structure and the impact of different forcing’s on these parameters. On a larger scale, the development of benthic communities has also been characterized for both sites and on different infrastructures. In situ primary production measurements combined with biodiversity and PAM assessment have made it possible to describe the colonization processes of artificial infrastructures and to assess their effectiveness. This work brings a new vision to the benthic ecology associated with artificial hard substrates and makes it possible to provide reliable estimates of the impact of these structures on the ecosystem.
... Given increasing concerns about environmental change, sustainability, and resilience, there is growing interest in promoting coastal NI across the globe. Ecological design principles can be integrated into marine infrastructure projects to promote cobenefits (Cameron & Blanuša, 2016;Dafforn et al., 2015;Dennis et al., 2018), but more research is needed to improve and test scientific understanding of various aspects of effectiveness of NI and to gain better insights into human perceptions and social acceptance (Evans et al., 2017(Evans et al., , 2019Morris et al., 2016Morris et al., , 2019Smith et al., 2020). Research into best practices in coastal NI should also seek a holistic approach to benefits assessment across terrestrial, freshwater, and marine domains (Lowe et al., 2022) and should take care to avoid green washing of widespread coastal development (Firth et al., 2020). ...
People often modify the shoreline to mitigate erosion and protect property from storm impacts. The 2 main approaches to modification are gray infrastructure (e.g., bulkheads and seawalls) and natural or green infrastructure (NI) (e.g., living shorelines). Gray infrastructure is still more often used for coastal protection than NI, despite having more detrimental effects on ecosystem parameters, such as biodiversity. We assessed the impact of gray infrastructure on biodiversity and whether the adoption of NI can mitigate its loss. We examined the literature to quantify the relationship of gray infrastructure and NI to biodiversity and developed a model with temporal geospatial data on ecosystem distribution and shoreline modification to project future shoreline modification for our study location, coastal Georgia (United States). We applied the literature‐derived empirical relationships of infrastructure effects on biodiversity to the shoreline modification projections to predict change in biodiversity under different NI versus gray infrastructure scenarios. For our study area, which is dominated by marshes and use of gray infrastructure, when just under half of all new coastal infrastructure was to be NI, previous losses of biodiversity from gray infrastructure could be mitigated by 2100 (net change of biodiversity of +0.14%, 95% confidence interval −0.10% to +0.39%). As biodiversity continues to decline from human impacts, it is increasingly imperative to minimize negative impacts when possible. We therefore suggest policy and the permitting process be changed to promote the adoption of NI.
... One approach to IGGI involves eco-engineering strategies, which aim to ameliorate the diversity deficit between natural reefs and artificial structure by combining ecological knowledge and engineering criteria in the construction and modification of artificial substrata (Browne and Chapman, 2011). In marine contexts, eco-engineering solutions range from the identification of alternative materials for construction (Dennis et al., 2018;Natanzi et al., 2021), to modification of surface textures (Coombes et al., 2015;Hall et al., 2018;Strain et al., 2021) and, more recently, replication of natural topographies (Evans et al., 2021). ...
... Given increasing concerns about environmental change, sustainability, and resilience, there is growing interest in promoting coastal NI across the globe. Ecological design principles can be integrated into marine infrastructure projects to promote cobenefits (Cameron & Blanuša, 2016;Dafforn et al., 2015;Dennis et al., 2018), but more research is needed to improve and test scientific understanding of various aspects of effectiveness of NI and to gain better insights into human perceptions and social acceptance (Evans et al., 2017(Evans et al., , 2019Morris et al., 2016Morris et al., , 2019Smith et al., 2020). Research into best practices in coastal NI should also seek a holistic approach to benefits assessment across terrestrial, freshwater, and marine domains (Lowe et al., 2022) and should take care to avoid green washing of widespread coastal development (Firth et al., 2020). ...
... In this regard, many studies used artificial reefs as a mitigation tool for aquaculture cages since biofouling organisms are mainly filter feeders, A. Carmona-Rodríguez et al. allowing the reduction of organic matter in the system (Angel et al., 2002;Gao et al., 2008;Aguado-Giménez et al., 2011). The main material used in artificial reefs construction is concrete, as many others have negative impacts on marine habitats, although concrete is not an exception (Müllauer et al., 2015;Dennis et al., 2018;McManus et al., 2018). As it has been seen, the electrolytic carbonated substrate not only has a higher recruitment of filter-feeder organisms, but also the ones we define as active filters. ...
Biofouling in different artificial substrata was done to determine the differences in biofouling assemblages among different substrates. However, studies on biofouling on natural substrates like electrolytic carbonated ones are lacking. These substrates have a great potential for coral reef restoration in tropical areas and for biofilter construction. Thus, this study was done to examine the colonization of sessile macrofouling in the port of Alicante (SE Spain, Western Mediterranean) on two types of substrata: electrolytic carbonated and bare steel (as control) over three months of immersion (October 2019-January 2020). The community diversity was studied through different biotic parameters and abundance of assemblages, and preference of organisms according to their status and functional group (active filter feeders). Univariate and multivariate analyses (PERMANOVA and SIMPER) were also done to examine the differences between carbonate and control substrata. The carbonated substrate had a more structured community and higher abundance, recruitment, and diversity indexes than the bare steel. Moreover, filter feeders (Porifera, Bivalvia, and Ascidiacea) were more abundant, and most of them only appeared in the carbonated substrate. These results show the potential of carbonated structures as biofilters.
... The difference in species richness between the smooth concrete tiles and the rock was not significant. This concurs with other studies testing material types (Cacabelos et al., 2016;Hartanto et al., 2022), suggesting that other factors might be more significant or affect different ecological metrices such as abundance (Dennis et al., 2018). ...
Hard coastal defences support lower biodiversity than natural rocky shores. Ecological enhancement on coastal structures can improve biodiversity by increasing habitat heterogeneity. Most studies have investigated the effect of only one type of texture on intertidal biodiversity. There is a lack of eco-engineering designs that mimic the complexity of natural rocky shores and are scalable for real world applications and commercial manufacturing. To address these gaps, we developed a novel, multiscale (mm-cm), multispecies design called BioGeo Ecotile that is scalable and readily manufacturable. The hybrid design combines previously tested eco-engineering features (pits, holes, grooves and crevices), providing habitats for a range of intertidal organisms. To test the success of the design, Ecotiles and smooth tiles were deployed on rock armour and flood walls along Edinburgh's coast, Scotland. Post-deployment, data on species presence and abundance were collected at the start and end of the second settlement season. Textured Ecotiles supported higher species richness (F3,55 = 21.18, p < 0.001) and colonisation than smooth tiles and adjacent rock armour. Ecotiles supported more mobile species, some of which (crabs) were not recorded on the other treatments. Material type (concrete vs rock) significantly affected community composition, where concrete was dominated by fucoids and rock by barnacles. In this temperate setting, the Ecotiles have enhanced biodiversity of rock armour achieving practical conservation goals. This is the first known retrofit of tiles onto rock armour in the UK. The tiles can be scaled up to whole walls or rock armour units. We demonstrate that a science-design approach can achieve ecological and engineering goals simultaneously, which can accelerate widespread implementation of eco-engineering in large-scale projects.
... Iron ions released by the structure during oxidation can be utilized by algae and provide primary productivity (Layman et al., 2016). Benefiting from the advantages of substantial biological attachment rates, stable structures, low costs, and simple moldings, the concrete material has become one of the most widely used types of artificial reefs (Dennis et al., 2018). In the 21st century, the concept of ecological concrete was proposed. ...
Artificial reefs are beneficial to restore fishery resources and increase fishery production. Meanwhile, they play a significant role in improving ocean ecology and accelerating the evolution of fishery industries. Since they are generally affected by currents, waves, and other hydrological factors, the flow field around artificial reefs and their stabilities have become a research hotspot in recent years. Research on artificial reefs is a systematic process consisting of four aspects: Firstly, the significance, the definition, the mechanism, and the present research progress were introduced for artificial reefs in detail. Secondly, the development trend of the sit-bottom artificial reef and that of the floating artificial reef were summarized, respectively. Thirdly, it was found that the combination of traditional artificial reefs and emerging ocean engineering has a great development potential in practical engineering. Finally, the existing problems related to the hydrodynamic characteristics of the artificial reefs in China were summarized, and the prospects of artificial reefs were proposed. The purpose of this study is to provide a scientific reference for the ecological and sustainable development of the large-scale construction of artificial reefs in the ocean.
... Ceramic modules with tighter surface-pore densities may reduce biofouling and/or enhance targeted species-specific settlement (Johari et al., 2010). Companies are already creating "ecologically active" concrete materials that modify composition and surface texture to support specific marine fauna and flora (Perkol-Finkel and Sella, 2014), lowers the carbon footprint of artificial habitat construction (Dennis et al., 2018), and addresses the concern of concrete waste in aquatic ecosytems (Cooke et al., 2020). One could even consider expanding and adapting this method to test biofilm or antibiofouling coatings that reduce or promote targeted biotic build-up (Tamburri et al., 2008). ...
Identifying features of biogenic (i.e., living) habitat that attract and retain organisms is a key pursuit in ecological habitat selection research. Here we present an integrative method for creating aquatic artificial habitat modules that allow the user to isolate and flexibly manipulate structural and compositional features of replicated biogenic habitats for a range of habitat selection study designs in aquatic environments: This method combines techniques from engineering (3D scanning and printing), paleontology, and visual art (moulding and casting) into a stream-lined work flow that is likely to perform on par with or better than other techniques widely used to create artificial replicas of biogenic habitats in terms of design accessibility (availability and cost of construction materials and equipment, and training requirements), scalability (durability, ease of deployment, and reproducibility), and the ecology of the artificial habitat module (degree to which structural and compositional features of the habitat elicit appropriate visual, chemosensory, and auditory cues, and impact of the structure on the surrounding environment). This method can be flexibly modified to answer a variety of questions regarding habitat selection cues, for a range of aquatic biogenic habitat types, and can be adapted for theoretical and applied contexts including cue studies and restoration planning.
... Key strategies include the introduction of micro-texture (Coombes et al., 2015), crevices and grooves (Martins et al., 2010;Borsje et al., 2011), artificial rock pools (Firth et al., 2014;Evans et al., 2015), precast habitat enhancement units and panels Browne and Chapman, 2014;Perkol-Finkel et al., 2018) and biotic complexity through seeding with habitat-forming species such as oysters and mussels (Bradford et al., 2020;Strain et al., 2020), corals (Ng et al., 2015) and canopy-forming algae (Perkol-Finkel et al., 2012). In addition, some studies have suggested the type of material (Dennis et al., 2018;McManus et al., 2018) and/or slope (Chapman and Underwood, 2011) of the habitat enhancement units and panels should be manipulated to increase their ecological benefits. Until recently, much of this research has focused on the intertidal zone of specific locations (e.g. ...
The human population is increasingly reliant on the marine environment for food, trade, tourism, transport, communication and other vital ecosystem services. These services require extensive marine infrastructure, all of which have direct or indirect ecological impacts on marine environments. The rise in global marine infrastructure has led to light, noise and chemical pollution, as well as facilitation of biological invasions. As a result, marine systems and associated species are under increased pressure from habitat loss and degradation, formation of ecological traps and increased mortality, all of which can lead to reduced resilience and consequently increased invasive species establishment. Whereas the cumulative bearings of collective human impacts on marine populations have previously been demonstrated, the multiple impacts associated with marine infrastructure have not been well explored. Here, building on ecological literature, we explore the impacts that are associated with marine infrastructure, conceptualising the notion of correlative, interactive and cumulative effects of anthropogenic activities on the marine environment. By reviewing the range of mitigation approaches that are currently available, we consider the role that eco-engineering, marine spatial planning and agent-based modelling plays in complementing the design and placement of marine structures to incorporate the existing connectivity pathways, ecological principles and complexity of the environment. Because the effect of human-induced, rapid environmental change is predicted to increase in response to the growth of the human population, this study demonstrates that the development and implementation of legislative framework, innovative technologies and nature-informed solutions are vital, preventative measures to mitigate the multiple impacts associated with marine infrastructure.
... 60 (Dyson and Yocom, 2015). Par conséquent, ces nouvelles approches (Bergen et al., 2001;Dennis et al., 2018;Firth et al., 2014Firth et al., , 2016Mitsch, 2012;Pioch et al., 2018;Strain et al., 2018) Dans ce contexte, les principaux objectifs de ce travail de recherche portent sur la capacité des micro-algues à assimiler certains nutriments provenant de la matrice cimentaire. L'autre intérêt est aussi d'étudier l'effet du biofilm sur la couche superficielle du matériau en fonction du temps en suivant l'évolution de la composition, la microstructure et la durabilité (diffusion des ions chlorure) de ce dernier. ...
Aujourd’hui, les matériaux cimenaires sont majoritairement utilisés pour la construction d’infrastructures maritimes ou de récifs artificiels. Ces derniers sont rapidement colonisés par un biofilm composé de microorganismes qui au cours du temps peut modifier sa composition et sa microstructure. Dans ce contexte, cette thèse vise à comprendre et suivre les interactions entre les micro-organismes marins et la matrice cimentaire. Les matériaux cimentaires étudiés pendant cette thèse sont le mortier et le béton. Les principaux objectifs associés portent sur la capacité des microalgues à assimiler certains nutriments provenant de la matrice cimentaire. Il en ressort que les diatomées Cylindrotheca closterium peuvent assimiler la silice dissoute provenant du mortier lorsque son milieu en est limité. Par ailleurs, celles-ci sont capables de s’acclimater à la disponibilité en silicium. Un des autres objectifs est d’étudier l’effet du biofilm sur la couche superficielle du matériau en fonction du temps. Des analyses de composition et de microstructure ont été réalisées. Des études accélérées en laboratoire et en mésocosme ont été mises enplace. Une fois immergé, des modifications de la composition du matériau cimentaire ont été observées.L’activité biologique du biofilm a provoqué une augmentation de la dissolution en profondeur de la portlandite. La formation de carbonates de calcium est rapidement observée une fois le matériau immergé en eau de mer. La forme des carbonates de calcium varie suivant que le matériau cimentaire est colonisé ou non. A long terme, la bio-colonisation joue également un rôle protecteur contre la pénétration de ces agents agressifs.
... break mangrove roots or topple coral colonies), allowing habitat structure to persist in the system. In contrast, artificial infrastructure may lack important characteristics, such as chemical cues that are important for inducing recruitment of the desired species assemblage, or contain additives that inhibit settlement (Dennis et al. 2018). Consequently, differences in communities have also been observed between foundation species and hard infrastructure, including a greater presence of non-indigenous species on hard infrastructure than on foundation species , Chapman 2003, Bulleri & Airoldi 2005, Glasby et al. 2007, Tyrrell & Byers 2007, Mineur et al. 2012, Airoldi et al. 2015. ...
Foundation species traits that structure communities are rarely experimentally examined; thus, a predictive understanding of their functions lags behind patterns of observed species associations. Red mangrove Rhizophora mangle roots form complex living habitats that
support diverse epibiont communities, making them a model system for testing links between variation in foundation species traits and associated biodiversity. Here, we compared epibiont community composition between living and non-living mangrove roots, as well as root mimics, to test how foundation species traits affect community structure. We also quantified the community structure of associated mobile invertebrates to examine their relationship with secondary foundation species (e.g. sponges, bivalves) that grow on the roots. After 14 mo of colonization and succession, substrate composition (i.e. mangrove, wood, PVC) had significant effects on community
composition, richness, and abundance of sessile epibionts and mobile invertebrates. Non-living mangrove roots were 5 times more likely to deteriorate, and consequently had the lowest epibiont richness and abundance. We found strong positive relationships between mobile invertebrate richness and the abundance, measured as biomass, and richness of sponges and bivalves, suggesting that variation among roots in secondary foundation species play an important role in
mediating mobile invertebrate community composition. This study highlights the functional role of habitat structure and how rapidly that function can be lost without biogenic maintenance. Our results indicate the importance of facilitation cascades in fostering diverse mobile invertebrate communities and highlight both advantages and limitations in using artificial structures in restoration programs.
... This aspect has been thoroughly covered in recent articles (Tables 1 and S1) and past reviews ( Figure 2). Researches mostly describe this effect by stating modifications made to increase HC such as the number of added structures (Wasserman et al., 2016), which is common in laboratory, or what kind of material was used to enrich the complexity of the environment (Dennis et al., 2018), common in in situ field studies. In controlled environments, researchers manipulate HC by transferring natural complexity generators or their models to create gradients with ad hoc established units of complexity. ...
Habitat complexity describes a wide array of spatial distribution patterns of physical structures in habitats. It affects aquatic ecosystems on multiple levels from individuals (e.g., foraging behavior) to species interactions (e.g., predation, prey selection) and entire communities (e.g., biodiversity, food web structure). We present a conceptual framework to classify these effects and use it to summarize recent advances in the field. We identify three main research gaps and limitations preventing a full synthesis of the effects of habitat complexity on aquatic communities and ecosystems. Habitat complexity is often characterized using ad hoc measures, which limits cross‐experimental comparison and meta‐analytical and modeling approaches. The effects of habitat complexity on communities and ecosystems can also involve feedback loops on lower levels of organization including the habitat complexity itself. Such ecological feedbacks can influence habitat formation and amplify or mitigate the direct effects of habitat loss and simplification or habitat restoration on populations and communities, yet are surprisingly little understood. Finally, most studies examine habitat complexity on the presence‐absence scale. This limits our ability to recognize nonlinear responses across habitat complexity gradients, which occur in many contexts in aquatic habitats. Since nonlinear responses can stabilize or destabilize population and community dynamics, we call for the use of a higher resolution of habitat complexity in future studies. We conclude that currently degraded habitats offer exciting opportunities for combining restorative efforts with research that could combine multi‐level experiments and monitoring to improve our understanding of the role of habitat complexity across aquatic ecosystems.
This article is categorized under: Water and Life > Nature of Freshwater Ecosystems
Water and Life > Conservation, Management, and Awareness
... Despite concrete mixture being a significant factor in some of the analyses only few differences between mixtures were detected, with plain concrete generally having lower abundances of the most abundant NIS, the ascidian Styela plicata, than oyster mixtures. This aligns with findings from a previous study assessing the effect of shell materials in concrete, which found greater live cover on oyster blends compared to a standard granulated blastfurnace slag control blend (Dennis et al., 2018). In contrast to the previous study, taxon richness was not affected. ...
... Likewise intertidal barnacles in the SW UK have shown no preference for washed aggregate surfaces (Coombes et al., 2015) and balanid barnacles were most abundant on the smooth C type Reef Cubes®. Future research should focus on creating grooved or rock-like textures on the surfaces of Reef Cubes® (Coombes et al., 2015;Perkol-Finkel and Sella, 2014;Potet et al., 2021) or alternative aggregate types that enhance biodiversity, potentially through alteration of the surface texture (Dennis et al., 2018). ...
Reef Cubes® are novel artificial reef units intended to enhance habitat complexity and provide hard substrate around marine man-made infrastructure. If made with Portland Cement, Reef Cubes® could create numerous negative environmental impacts, including a high carbon footprint. Alkali-activated materials (AAMs) are a collection of alternative binders associated with lower embodied emissions but alterations to concrete chemistry can affect the development of marine fouling communities. The objectives of this study were to evaluate the effect of replacing Portland Cement with an AAM binder on the development of macrofouling communities on Reef Cubes®. 25 cm sided Reef Cubes® were manufactured using three different concrete material types and deployed in the subtidal zone of Torbay, Devon, UK. The material types were an alkali activated slag concrete (Type: AAM), a cement-limestone blend (CEM-II) concrete (Type: C) and a cement-limestone blend (CEM-II) concrete with an additional micro silica pozzolan and an exposed aggregate texture (Type: CP). After 1 year of immersion the Reef Cubes® were retrieved, and fouling communities were analysed visually or scraped and weighed to gauge biomass. Univariate metrics of species richness, species diversity, total live cover, total biomass, calcareous mass and live biomass; and multivariate community compositions were compared. There were no significant differences in species richness, species diversity, total biomass, calcareous mass and live biomass between the material types. Total live cover was significantly different; with C appearing the highest, followed by AAM and CP, however pairwise comparisons were not significant. The community compositions on the AAM and C Reef Cubes® were not significantly different. Both were significantly different to the CP material type, which had a higher abundance of erect Bryozoans. The results suggest that compared to cement-based concretes, AAMs are a satisfactory substrate for the development of epibenthic communities on Reef Cubes®. There was also evidence contrary to common artificial reef practice that exposing the aggregate and incorporating a pozzolan improves biodiversity.
... between flat and control tiles that both lack complexity, the type of materials used could have contributed to this finding. Indeed, native species richness and composition have been reported to be affected by concrete type (McManus et al., 2018) and ecologically friendly material have greater biodiversity of colonising taxa (Dennis et al., 2018). Importantly, our study focused on sessile benthic communities (macroalgae and sessile invertebrates) but not mobile species. ...
Increasing human population, urbanisation, and climate change have resulted in the proliferation of hard coastal infrastructure such as seawalls and breakwaters. There is increasing impetus to create multifunctional coastal defence structures with the primary function of protecting people and property in addition to providing habitat for marine organisms through eco-engineering - a nature-based solutions approach. In this study, the independent and synergistic effects of physical complexity and seeding with native oysters in promoting diversity and abundances of sessile organisms were assessed at two locations on Penang Island, Malaysia. Concrete tiles with varying physical and biological complexity (flat, 2.5 cm ridges and crevices, and 5 cm ridges and crevices that were seeded or unseeded with oysters) were deployed and monitored over 12 months. The survival of the seeded oysters was not correlated with physical complexity. The addition of physical and biological complexity interacted to promote distinct community assemblages, but did not consistently increase the richness, diversity, or abundances of sessile organisms through time. These results indicate that complexity, whether physical or biological, is only one of many influences on biodiversity on coastal infrastructure. Eco-engineering interventions that have been reported to be effective in other regions may not work as effectively in others due to the highly dynamic conditions in coastal environment. Thus, it is important that other factors such as the local species pools, environmental setting (e.g., wave action), biological factors (e.g., predators), and anthropogenic stressors (e.g., pollution) should also be considered when designing habitat enhancements. Such factors acting individually or synergistically could potentially affect the outcomes of any planned eco-engineering interventions.
... For examples, see Perkol-Finkel and Sella (2015) and Perkol-Finkel et al. (2018) and the Fowl River Private Living Shorelines and Rich Revetments: Enhancing Hard Substrates for Ecology projects in Bridges et al. (2018) and MacArthur et al. (2020) for rock armor selection. It is also worth noting that there is a growing body of research exploring alternative, lower carbon or more ecologically suitable concrete mixes for use in coastal and marine ecoengineering (e.g., Dennis et al. [2018]). Recent experiments to test the efficacy of altering the pH of concrete to enhance ecological colonization rates have found no difference in ecological performance compared to conventional marine concrete mixes (Hsuing et al. 2020 For projects using dredged sediments for beneficial use, other factors should be considered. ...
Islands in estuaries, major river deltas, and open-coast environments reduce the severity of hazards, including erosion and flooding from wind-driven waves and extreme water levels, on the nearby habitats and shorelines. Islands may also provide critical ecosystem function for threatened and endangered species and migratory birds while providing access to recreational opportunities and navigation co-benefits. This chapter (Chapter 11) of the International Guidelines on Natural and Nature-Based Features (NNBF) for Flood Risk Management focusses on islands as NNBFs that support coastal resilience. Three types of islands are discussed—barrier islands, deltaic islands (including spits), and in-bay or in-lake islands. These islands may be new construction or, as in most cases, the restoration of island remnants. The degradation and loss of islands through combined processes such as sea-level rise, subsidence, and inadequate sediment input (e.g., upstream impoundments, navigation channels, evolving natural processes) are reducing the coastal resilience benefits of these features.
... The minimal overlap in isotopic niche for each species between natural mangrove and rock-fillet habitats could be explained by structural differences in the two habitats (Wahl, 1990) and differences in the range of autochthonous (Seitz et al., 2019) or allochthonous sources of carbon (Critchley et al., 2020;Strain et al., 2018aStrain et al., , 2018b. The porous walls of rock in rock-fillet structures introduce a novel hard substratum, which may contribute to higher habitat complexity and increased niche space (Dennis et al., 2018). Novel niches provided by rock-fillet structures are colonised by unique or new marine species (e.g. ...
There is growing demand for novel coastal protection approaches that also provide co-benefits such as enhanced biodiversity. Rock-fillets, which are used to stabilise eroding banks in estuaries, can be colonised by mangroves, and may provide habitat for estuarine fauna. However, it is unknown whether hybrid mangrove/rock-fillet habitats are functionally equivalent to natural mangroves, for estuarine fauna. To determine whether hybrid mangrove habitats are functionally equivalent to natural mangroves, we used δ¹³C and δ¹⁵N stable isotope analyses to describe the isotopic niche space and overlap of estuarine species in these two habitats across three estuaries in NSW, Australia. Using a Bayesian standard ellipse analysis of isotopic niche area, over half the 12 species observed had larger isotopic niche areas in natural mangroves compared to hybrid habitats, however there were no clear patterns for species between habitats. Natural mangroves and hybrid rock-fillet habitats were isotopically distinct for all species sampled (low proportional overlap, 0–19%) suggesting they are not, at present, wholistically functionally equivalent. Estuarine communities from the two habitat types, however, had similar isotopic niches. Hybrid communities displayed a broader range of δ¹³C values compared to natural mangroves, suggesting mangrove/rock-fillet habitats have a more diverse range of basal food sources. These findings demonstrate the potential for defence solutions to provide unique co-benefits by supporting food webs, but also that natural habitats provide unique ecosystem services that should be protected and rehabilitated where possible. Future modelling and monitoring of habitat utilisation and species performance could provide further insight into the co-benefits and trade-offs of hybrid habitats.
... The various industrial discharges and pollutants pose a serious threat to the marine life and lead to a decrease in pH. Studies have been conducted earlier with concrete/mortar in marine environment using different replacements of aggregates/binders: hemp fibres and recycled shell material (Dennis et al. 2017), coral waste with metakaolin (Wang et al. 2019), fly ash (Jiménez-Quero et al. 2011;Ramachandran et al. 2017) and silica fume (Farahani et al. 2015). ...
In the present investigation, induction furnace (IF) steel slag as coarse aggregate with 0%, 20% and 40% replaced concrete specimens of size 150 × 150 × 150 mm was prepared as an initiative to utilize iron-rich IF steel slag. The casted concrete specimens were cured for 28 days at room temperature (28 °C) in freshwater, and the obtained compressive strength is 22.5, 24.0 and 29.2 N/mm2, respectively. The blocks were then immersed in seawater under laboratory condition for 28 days, and variation in pH was monitored at regular intervals. The composition and mineralogical phases [quartz (SiO2), iscorite (Fe7SiO10), hematite (ε-Fe2O3) and almandine (Fe3Al2Si3O10)] present in IF steel slag were identified using XRF and XRD analysis, respectively. Surface morphology and elemental composition were studied using FESEM with EDAX analysis for before and after immersion of concrete blocks in seawater. Structural bonding of concrete blocks before and after immersion was studied using FTIR analysis. Compressive strength of concrete specimens after the immersion in seawater was evaluated and compared with before immersion in seawater. This initiative will be a major support for induction furnace steel industries via economic benefits. Utilization of iron-rich IF steel slag in marine concrete can be a vital candidate for the betterment of marine ecosystem via primary production of marine resources.Graphical abstract
... Multiple studies in temperate regions show that concrete marine infrastructure not only exhibits a different community composition than their surrounding natural reefs (Glasby et al., 2007;Bulleri and Chapman 2010;Airoldi et al., 2015), but also harbors a higher number of non-indigenous species (Glasby et al., 2007;Airoldi et al., 2015). This is often attributed to the high initial surface pH of concrete, which would favor alkali-resistant species over others during early succession (Dooley et al., 1999;Guilbeau et al., 2003;Dennis et al., 2018). However, a systematic comparison showed that pH is no main driver of benthic abundance, species richness or species composition (Hsiung et al., 2020), indicating that other factors affect community development on concrete structures. ...
p>Caribbean coral reefs are in decline and the deployment of artificial reefs, structures on the sea bottom that mimic one or more characteristics of a natural reef, is increasingly often considered to sustain ecosystem services. Independent of their specific purposes, it is essential that artificial reefs do not negatively affect the already stressed surrounding habitat. To evaluate the ecological effects of artificial reefs in the Caribbean, an analysis was performed on 212 artificial reefs that were deployed in the Greater Caribbean between 1960 and 2018, based on cases documented in grey (n = 158) and scientific (n = 54) literature. Depending on the availability of data, reef type and purpose were linked to ecological effects and fisheries management practices around the artificial reefs. The three most common purposes to deploy artificial reefs were to create new dive sites (41%), to perform research (22%) and to support ecosystem restoration (18%), mainly by stimulating diversity. Ship wrecks (44%), reef balls</p
In pursuit of a more sustainable construction material with the potential to improve bioreceptivity in marine environments, this study investigates the feasibility of incorporating three industrial residues—steel sludge (“Conox”), mytilid mussel shells, and wheat straw fibers—as partial substitutes for cement and sand. The research focuses on evaluating the physical and mechanical properties of mortar and concrete mixtures containing these residues, both individually and in combination. Additionally, it assesses the metal leaching potential of concrete incorporating Conox sludges into the environment. The results show that mixture containing 10% Conox sludges as a sand substitute exhibit the highest mechanical strength but also increased porosity, water absorption, and chloride ion diffusion. The addition of mussel shells and straw fibers generally reduced mechanical properties and increased porosity in mortars, though a 20% mussel shell substitution maintained mechanical strength and chloride ion diffusion in the concrete. The combination of mussel shells with Conox sludges allowed the concrete to retain its mechanical properties, although it also increased porosity and chloride ion penetration, which may limit its use where impermeability is key. However, this increased porosity could benefit coastal erosion control structures like breakwaters and revetments, and sea walls. Moreover, metal leaching from concrete incorporating Conox sludges remained within established safety limits. Despite these challenges, the materials show promise for non-structural applications or projects where sustainability is prioritized. Our research lays the foundation and opens new possibilities for future investigations that innovate in the combination of industrial wastes, aiming to create more sustainable construction materials with a reduced impact on biodiversity.
Artificial structures are widespread features of coastal environments, but are poor surrogates of natural rocky shores because they generally support depauperate assemblages with reduced population sizes. This has generated significant interest in eco-engineering solutions, including retrofitting seawalls with artificial rockpools to increase water retention and provide microhabitats. Although these have proven effective at individual sites, widespread uptake is contingent on evidence of consistent benefits across a range of contexts. In this study, Vertipools™ were retrofitted on eight seawalls in different environmental contexts (urban v rural and estuarine v marine) along the Irish Sea coastline and were monitored regularly for two years. Seaweed colonisation proceeded in a manner similar to patterns described for natural and artificial intertidal systems in general, consisting of early dominance by ephemeral species followed by the appearance and eventual establishment of perennial habitat-formers. After 24 months, species richness did not differ between contexts, but differed between sites. The units supported populations of large habitat-forming seaweeds at all sites. Productivity and community respiration of the colonising communities differed between sites by up to 0.5 mg O2 L−1 min−1, but not across environmental contexts. This study demonstrates that bolt-on rockpools attract similar levels of biotic colonisation and functioning in a variety of temperate environmental contexts, and could be considered for widespread implementation as an eco-engineering solution.
Coastal zones provide about 70% of the world’s ecosystem services. However, more than 25% of these habitats have been modified by human activity at both land and sea. At the intertidal eco-tonal zone, habitat modification is equally severe, as almost 20% of the world’s shoreline is now artificial. Coastal defense structures are more abundant in areas where the ecosystem richness, diversity and productivity are higher, such as coastal lagoons, estuaries and bays. As these degrad-ed areas are under high human pressure, their protection should be prioritized. Coastal infrastruc-ture, particularly those enclosing highly modified water bodies, such as ports and marinas, are hubs for pollution and human activities, such as trade and leisure. These have become a serious threat to marine coastal communities, due to habitat degradation and disease spread, and ecolog-ical-engineering interventions are now an imperative to integrate urban with nature and improve life and ecosystem quality for coastal settlements.
A greener and more sustainable option is proposed to shift the construction paradigm of high embedded carbon values in concrete and the frequency of repairs when it cracks. Using low-carbon concrete with a bacterial self-healing agent can reduce the embedded carbon value while adding value to the structure. This paper aims to evaluate the interaction of a bacterial self-healing agent on the mechanical properties of low-carbon concrete, specifically 50% Ground Granulated Blast-furnace Slag (GGBS) as an Ordinary Portland Cement (OPC) replacement. A range of tests is conducted to test the evolution of mechanical properties throughout the early stages of curing for 7, 14, and 28 days. Such tests included the evaluation of compression, flexural, tensile splitting strength and dynamic elastic modulus. The results of the experiments demonstrate that early stages of GGBS mixes exhibit lower compressive capacity throughout the 28-day mark but also indicate their potential to increase sharply and surpass the control mix values after 28 days. The self-healing agent interacts slightly with the GGBS mixes, further reducing the mechanical properties in the early curing stages. However, GGBS mixes increase sharply after the 28-day mark, with the added benefit of further reducing carbon emissions by extending design life and durability. In theory, the newly developed concrete can seal cracks up to 0.3 mm (up to 0.8 mm if using the maximum dosage) but seal wider cracks from laboratory results. These changes imply that using GGBS as a replacement for OPC is viable for structures that do not require high compressive values in the early curing stages but after the 28-day mark while reducing the carbon emission values substantially, in this case, 40%, or up to 50% if using a self-healing agent. This low-carbon concrete is thus a sustainable and resilient material, especially for retrofitting existing reinforced concrete infrastructure.
Increasing frequency of extreme weather events, driven by climate change, coupled with growing population densities, have contributed to an increasing demand for coastal structures to protect and stabilize shorelines. Concrete seawalls are a common category of coastal protection structures, designed with the primary objectives of absorbing wave action, preventing coastline erosion, and alleviating flooding. Much research has been carried out on improving concrete seawall performance. This work is a review of the current state-of-the-art in concrete seawalls focusing on design aspects including wave loading and innovative seawall designs, ecological considerations, and durability performance. Different conventional seawalls and their advantages and disadvantages are reviewed. Wave loads on seawalls have received significant attention; and multiple approaches for the quantification for the different types of loads are presented. However, wave load quantification remains a challenging task, especially for novel designs, and performance under load for such designs must be quantified through testing in wave tanks. Drawing inspiration from natural shorelines, modification of surface complexity at a multitude of scales can improve the otherwise poor ecological performance of seawalls. Ecological performance can also be improved by the incorporation of natural materials or structures in seawalls although the exact influence of concrete and other material chemistry on benthic diversity is unclear. The corrosion of the steel is a major durability concern, and the use of non-corrosive reinforcement can increase seawall durability toward corrosion. Other durability concerns include alkali silica reaction and sulfate attack, which can be mitigated through proper mixture design, including through the use of supplementary cementitious materials. Examples of innovative seawall designs and systems which have the capability to outperform conventional seawalls are discussed. Advances in structural design, ecological engineering, and infrastructure materials science will drive the development of multi-functional seawalls which are sustainable, durable, and resilient.
Increasing frequency of extreme weather events, driven by climate change, has resulted in an increasing demand for coastal structures to protect and stabilize shorelines. Concrete seawalls are a common category of coastal protection structures, designed with the primary objectives of absorbing wave action, preventing coastline erosion, and alleviating flooding. Much research has been carried out on improving the seawall performance. This work is a review of the current state-of-the-art in concrete seawalls focusing on design aspects including wave loading and innovative seawall designs, ecological considerations, and durability aspects. Wave loads on seawalls have received significant attention; however, their quantification remains a challenging task especially for novel designs. Drawing inspiration from natural shorelines, modification of surface complexity at a multitude of scales can improve the otherwise poor ecological performance of seawalls. The corrosion of the steel is a major durability concern, and the use of non-corrosive reinforcement can increase seawall durability towards corrosion. Examples of innovative seawall designs and systems which have the capability to outperform conventional seawalls are discussed. Advances in structural design, ecological engineering, and infrastructure materials science will drive the development of multi-functional seawalls which are sustainable, durable, and resilient.
Natural coastlines are being replaced by artificial structures (pilings, pontoons, breakwaters), with negative environmental impacts, particularly in marinas. Ropes seeded with mussels (Mytilus galloprovincialis) were added to artificial structures in a marina, using aquaculture techniques, to reduce the colonisation of invasive taxa. After 6-months, droplines beneath pontoons had the highest seeded mussel survival and growth, richness of native and invasive taxa, and proportion of invasive to native taxa, compared with the other interventions. Mussel ropes on the intertidal structures (pilings and breakwaters) supported higher biomass of native taxa, whereas mussel ropes on subtidal structures (pontoons and breakwaters) had reduced biomass of invasive taxa, relative to the unseeded ropes. Droplines had the greater biomass of mussels, while mussel ropes placed under pontoons, and in subtidal gabion baskets limited the biomass but not the diversity of invasive species. Further study is required to determine whether these interventions can be upscaled to improve both the native biodiversity and functioning of marinas.
On one of the breakwaters at the sea side at IJmuiden (the Netherlands) concrete slabs, measuring 75 cm x 50 cm, with 6 sections of 25 cm x 25 cm with each a different geometric structure or texture were tested for algal and macrofaunal colonization on, in terms of wave exposure, a low dynamic (south east exposed) and high dynamic location (south west exposed). The slabs were mounted on large concrete blocks of 22 to 45 metric ton embedded in asphalt both horizontally and vertically in the high, mid and low intertidal zone. The succession of the hard substrate communities that developed on the slabs were monitored from 2008 till 2010. Green seaweeds developed rapidly on sections with fine and coarse texture compared to smooth texture (control). In the low intertidal zone of the low dynamic location geometric structures positively influenced the settlement of Blue mussels. Hole structures were (during ebb tide) important for periwinkles. In 2009 concrete slabs measuring 60 cm x 60 cm, with 4 sections of 30 cm x 30 cm with respectively vertical grooves, holes, artificial rock structure and a smooth texture were mounted vertically just above the mean low water level on mooring poles in a small polyhaline harbour in the port of Rotterdam. There was no difference between settlement of algae and macrozoöbenthos on each of the sections. Percentages of coverage were extremely low. It was concluded that the differences in succession on the slabs at IJmuiden and Rotterdam were the result of dissimilarities in abiotic conditions. The vertical position of the slabs, the absence of waves and an 4-5 hours long low water period at Rotterdam hampered the settlement of algae and macrofauna.
Significance
Kelp forests support diverse and productive ecological communities throughout temperate and arctic regions worldwide, providing numerous ecosystem services to humans. Literature suggests that kelp forests are increasingly threatened by a variety of human impacts, including climate change, overfishing, and direct harvest. We provide the first globally comprehensive analysis of kelp forest change over the past 50 y, identifying a high degree of variation in the magnitude and direction of change across the geographic range of kelps. These results suggest region-specific responses to global change, with local drivers playing an important role in driving patterns of kelp abundance. Increased monitoring aimed at understanding regional kelp forest dynamics is likely to prove most effective for the adaptive management of these important ecosystems.
In coastal habitats artificial structures typically support lower biodiversity and can support greater numbers of non-native and opportunistic species than natural rocky reefs. Eco-engineering experiments are typically trialed to succeed; but arguably as much is learnt from failure than from success. Our goal was to trial a generic, cost effective, eco-engineering technique that could be incorporated into rock armouring anywhere in the world. Artificial rock pools were created from manipulated concrete between boulders on the exposed and sheltered sides of a causeway. Experimental treatments were installed in locations where they were expected to fail and compared to controls installed in locations in which they were expected to succeed. Control pools were created lower on the structure where they were immersed on every tidal cycle; experimental pools were created above mean high water spring tide which were only immersed on spring tides. We hypothesised that lower and exposed pools would support significantly higher taxon and functional diversity than upper and sheltered pools. The concrete pools survived the severe winter storms of 2013/14. After 12 months, non-destructive sampling revealed significantly higher mean taxon and functional richness in lower pools than upper pools on the exposed side only. After 24 months the sheltered pools had become inundated with sediments, thus failing to function as rock pools as intended. Destructive sampling on the exposed side revealed significantly higher mean functional richness in lower than upper pools. However, a surprisingly high number of taxa colonised the upper pools leading to no significant difference in mean taxon richness among shore heights. A high number of rare taxa in the lower pools led to total taxon richness being almost twice that of upper pools. These findings highlight that even when expected to fail concrete pools supported diverse assemblages, thus representing an affordable, replicable means of enhancing biodiversity on a variety of artificial structures.
The present review provides a framework within which the impact of dredging on biological resources that live on the sea bed ("Benthic" communities) can be understood, and places in perspective some of the recent studies that have been carried out in relation to aggregates dredging in European coastal waters. The impact of dredging works on fisheries and fish themselves, and on their spawning grounds is outside the scope of this review. We have, however, shown that empirical models for shelf waters such as the North Sea indicate that as much as 30% of total fisheries yield to man is derived from benthic resources, and that these become an increasingly important component of the food web in near-shore waters where primary production by seaweeds (macrophytes) and seagrasses living on the sea bed largely replaces that by the phytoplankton in the water column. Because dredging works are mainly carried out in near-shore coastal deposits, and these are the ones where benthic production processes are of importance in supporting demersal fish production, our review concentrates on the nature of benthic communities, their sensitivity to disturbance by dredging and land reclamation works, and on the recovery times that are likely to be required for the re-establishment of community structure following cessation of dredging or spoils disposal. Essentially, the impact of dredging activities mainly relates to the physical removal of substratum and associated organisms from the sea bed along the path of the dredge head, and partly on the impact of subsequent deposition of material rejected by screening and overspill from the hopper. Because sediment disturbance by wave action is limited to depths of less than 30 m, it follows that pits and furrows from dredging activities are likely to be persistent features of the sea bed except in shallow waters where sands are mobile. Recent studies using Acoustic Doppler Current Profiling (ADCP) techniques suggest that the initial sedimentation of material discharged during outwash from dredgers does not, as had been widely assumed, disperse according to the Gaussian diffusion principles used in most simulation models, but behaves more like a density current where particles are held together during the initial phase of the sedimentation process. As a result, the principal area likely to be affected by sediment deposition is mainly confined to a zone of a few hundred metres from the discharge chute. Our review suggests that marine communities conform with well established principles of ecological succession, and that these allow some realistic predictions on the likely recovery of benthic communities following cessation of dredging. In general, communities living in fine mobile deposits, such as occur in estuaries, are characterized by large populations of a restricted variety of species that are well adapted to rapid recolonization of deposits that are subject to frequent disturbance. Recolonization of dredged deposits is initially by these "opportunistic" species and the community is subsequently supplemented by an increased species variety of long-lived and slow-growing "equilibrium" species that characterize stable undisturbed deposits such as coarse gravels and reefs. Rates of recovery reported in the literature suggest that a recovery time of 6-8 months is characteristic of many estuarine muds where frequent disturbance of the deposits precludes the establishment of long-lived components. In contrast, the community of sands and gravels may take 2-3 yr to establish, depending on the proportion of sand and level of environmental disturbance by waves and currents, and may take even longer where rare slow-growing components were present in the community prior to dredging. As the deposits get coarser along a gradient of environmental stability, estimates of 5-10 yr are probably realistic for development of the complex biological associations between the slow-growing components of equilibrium communities characteristic of reef structures. Most recent studies show, however, that biological community composition is not controlled by any one, or a combination of, simple granulometric properties of the sediments such as particle size distribution. It is considered more likely that biological community composition is controlled by an array of environmental variables, many of them reflecting an interaction between particle mobility at the sediment water interface and complex associations of chemical and biological factors operating over long time periods. Such interactions are not easily measured or analyzed, but the results suggest that the time course of recovery of an equilibrium community characteristic of undisturbed deposits is controlled partly by the process of compaction and stabilisation that occurs following deposition. Biological community composition thus reflects changes in sediment composition, but is also in equilibrium with seabed disturbance from tidal currents and wave action, both of which show spatial variations and interactions with water depth. The processes associated with compaction and stability of seabed deposits may, therefore, largely control the establishment of long-lived components of equilibrium communities and account for the dominance of opportunistic species in the initial stages of colonization in unconsolidated deposits of recently sedimented material after the cessation of dredging.
Kelp forests represent some of the most productive and diverse habitats on Earth. Understanding drivers of ecological patterns at large spatial scales is critical for effective management and conservation of marine habitats. We surveyed kelp forests dominated by Laminaria hyperborea (Gunnerus) Foslie 1884 across 9° latitude and >1000 km of coastline and measured a number of physical parameters at multiple scales to link ecological structure and standing stock of carbon with environmental variables. Kelp density, biomass, morphology and age were generally greater in exposed sites within regions, highlighting the importance of wave exposure in structuring L. hyperborea populations. At the regional scale, wave-exposed kelp canopies in the cooler regions (the north and west of Scotland) were greater in biomass, height and age than in warmer regions (southwest Wales and England). The range and maximal values of estimated standing stock of carbon contained within kelp forests was greater than in historical studies, suggesting that this ecosystem property may have been previously undervalued. Kelp canopy density was positively correlated with large-scale wave fetch and fine-scale water motion, whereas kelp canopy biomass and the standing stock of carbon were positively correlated with large-scale wave fetch and light levels and negatively correlated with temperature. As light availability and summer temperature were important drivers of kelp forest biomass, effective management of human activities that may affect coastal water quality is necessary to maintain ecosystem functioning, while increased temperatures related to anthropogenic climate change may impact the structure of kelp forests and the ecosystem services they provide.
Coastal defences are proliferating in response to anticipated climate change and there is increasing need for ecologically sensitive design in their construction. Typically, these structures support lower biodiversity than natural rocky shores. Although several studies have tested habitat enhancement interventions that incorporate novel water-retaining features into coastal defences, there remains a need for additional long-term, fully replicated trials to identify alternative cost-effective designs. We created artificial rock pools of two depths (12 cm, 5 cm) by drill-coring into a shore-parallel intertidal granite breakwater, to investigate their potential as an intervention for delivering ecological enhancement. After 18 months the artificial rock pools supported greater species richness than adjacent granite rock surfaces on the breakwater, and similar species richness to natural rock pools on nearby rocky shores. Community composition was, however, different between artificial and natural pools. The depth of artificial rock pools did not affect richness or community structure. Although the novel habitats did not support the same communities as natural rock pools, they clearly provided important habitat for several species that were otherwise absent at mid-shore height on the breakwater. These findings reveal the potential of drill-cored rock pools as an affordable and easily replicated means of enhancing biodiversity on a variety of coastal defence structures, both at the design stage and retrospectively.
The mid-zone rocky intertidal community at protected and semiprotected areas in New England is characterized by a few, relatively small-bodied herbivore species. The effects of gastropod herbivores, primarily Littorina littorea, on secondary succession in the community were studied. These periwinkles preferentially consume early successional, ephemeral algae such as Ulva lactuca, Enteromorpha spp. and Porphyra spp. If not grazed, these early stages inhibit the appearance of a later successional species, Fucus vesiculosus. The effect of the herbivores on succession is to speed up the early successional sequence by releasing Fucus from inhibition by ephemeral species. Periwinkles will readily graze small Fucus germlings and can prevent their successful establishment on smooth rock surfaces, but substratum microtopography created by small crevices or pits or barnacles provides spatial refuges for small germlings. These plants quickly grow to a size at which they are less susceptible to periwinkle grazing. Although the periwinkles harm young Fucus, they benefit older plants by grazing epiphytes from the blades.-from Author
The large quantities of seashells produced in the North-West of France and the depletion of quarries motivates the research of new sources of aggregates. This article examines the influence of incorporating crushed queen scallop shells on ordinary concretes in order to assess the feasibility of reusing marine by products in the form of aggregates. For this purpose four different concrete mixes were produced, one of them used as reference with natural aggregates and the others prepared with 20, 40 and 60 % of crushed queen scallop shells replacing the natural aggregates. Concretes were characterized at fresh state by its workability, the air content and the density, and at hardened state by the mechanical and durability properties. The incorporation of crushed queen scallops causes an increase of the entrapped air of concrete, a reduction of the mechanical properties and an increase of the concrete porosity facilitating the transport of fluids and chloride ions in concrete.
This paper presents results from a year-long experimental study, evaluating the performance of ecologically active concrete matrices and designs for coastal and marine construction. Results indicate that slight modifications of concrete composition and surface texture can improve the capabilities of concrete based coastal and marine infrastructure (CMI) to support enhanced marine fauna and flora, and provide valuable ecosystem services alongside with economic advantages such as elevated water quality, increased operational life span, structural stability, and absorption of hydrodynamic forces.
On one of the breakwaters at the sea side at IJmuiden (the Netherlands) concrete slabs, measuring 75 cm x 50 cm, with 6 sections of 25 cm x 25 cm with each a different geometric structure or texture were tested for algal and macrofaunal colonization on, in terms of wave exposure, a low dynamic (south east exposed) and high dynamic location (south west exposed). The slabs were mounted on large concrete blocks of 22 to 45 metric ton embedded in asphalt both horizontally and vertically in the high, mid and low intertidal zone. The succession of the hard substrate communities that developed on the slabs were monitored from 2008 till 2010. Green seaweeds developed rapidly on sections with fine and coarse texture compared to smooth texture (control). In the low intertidal zone of the low dynamic location geometric structures positively influenced the settlement of Blue mussels. Hole structures were (during ebb tide) important for periwinkles.
In 2009 concrete slabs measuring 60 cm x 60 cm, with 4 sections of 30 cm x 30 cm with respectively vertical grooves, holes, artificial rock structure and a smooth texture were mounted vertically just above the mean low water level on mooring poles in a small polyhaline harbour in the port of Rotterdam. There was no difference between settlement of algae and macrozoöbenthos on each of the sections. Percentages of coverage were extremely low.
It was concluded that the differences in succession on the slabs at IJmuiden and Rotterdam were the result of dissimilarities in abiotic conditions. The vertical position of the slabs, the absence of waves and an 4-5 hours long low water period at Rotterdam hampered the settlement of algae and macrofauna.
This paper reports on an experimental study of the fracture energy of concrete reinforced with natural fibres of hemp, elephant grass, and wheat straw. Concrete specimens containing 0.19% of fibres by weight and of 40 mm of length were uniaxially tested with the wedge splitting test (WST) method. The addition of fibres was found to improve the fracture toughness of plane concrete. The most distinctive increase in the fracture energy has been observed by hemp reinforced concrete, up to 70%, when comparing with non reinforced concrete, whereas for straw and elephant grass reinforced concrete this increase was moderate, up to 2% and 5%, respectively. The beneficial effect of hemp fibres is believed to be the result of the fibre’s high tensile strength and the fibre’s fineness, resulting in a better bonding between fibres and concrete matrix. The presence of fibres in concrete decreased minimally the tensile strength of concrete, for 4%, 7%, and 8% for hemp, straw and elephant grass reinforced specimens, respectively.
Estuarine shorelines have been degraded since humans arrived in the coastal zone. In recent history, a major cause of habitat degradation has been the armoring of shorelines with vertical walls to protect property from erosive wave energy; however, a lack of practical alternatives that maintain or enhance ecological function has limited the options of waterfront residents and coastal zone managers. We experimentally investigated the habitat value of two configurations of submerged breakwaters constructed along an eroding shoreline in northwest Mobile Bay, AL (USA). Breakwaters comprised of bagged oyster shell or Reef Ball™ concrete domes were built by a community-based restoration effort. Post-deployment monitoring found that: bagged oyster breakwaters supported much higher densities of live ribbed mussels than Reef Ball breakwaters; both breakwater configurations supported increased species richness of juvenile and smaller fishes compared to controls; and that larger fishes did not appear to be affected by breakwater presence. Our study demonstrates that ecologically degraded shorelines can be augmented with small-scale breakwaters at reasonable cost and that these complex structures can serve as habitat for filter-feeding bivalves, mobile invertebrates, and young fishes. Understanding the degree to which these structures mitigate erosive wave energy and protect uplands will require a longer time frame than our 2-year-long study.
Over 80% of the money allocated to protect coastlines from climatic change is spent
building new seawalls or increasing the stability, height and length of existing seawalls. Although
this protects important infrastructure, it has serious consequences for intertidal biodiversity,
because walls are built and maintained according to engineering and financial criteria, despite
the fact that they are known to adversely affect intertidal biodiversity. We tested the predictability
and reliability of adding pots, designed to simulate rockpools, to seawalls as an artificial habitat to
mitigate against loss of intertidal species. Two sizes of concrete pots were attached at mid- and
highshore tidal levels to sandstone seawalls at 2 locations in Sydney Harbour, Australia. After
7 mo, pots increased intertidal biodiversity on the seawalls by adding additional species. They also
supported greater covers and densities of algae and many invertebrates compared with established
assemblages on the seawalls. The size of the pot, its height on the wall and its location
affected the assemblages that developed, with greater abundances and diversity of organisms in
shallower pots and those at midshore levels. Although there were slight differences between locations
for some taxa, these results show an easy cost-effective method that authorities can use to try
to mitigate the adverse effects on intertidal assemblages of armouring shorelines with featureless,
vertical walls.
Depletion of natural resources is a common phenomenon in developing countries like India due to rapid urbanization and Industrialization involving construction of Infrastructure and other amenities. In view of this, people have started searching for suitable other viable alternative materials for concrete so that the existing natural resources could be preserved to the possible extent, for the future generation. In this process, different industrial waste materials such as fly ash, blast furnace slag, quarry dust, tile waste, brick bats, broken glass waste, waste aggregate from demolition of structures, ceramic insulator waste, etc. have been tried as a viable substitute material to the conventional materials in concrete and has also been succeeded. This paper describes the studies conducted on strength characteristics of concrete made with utilizing waste materials viz: ceramic tiles, ceramic insulator waste, and broken glass pieces. A total number of 24cubes, 24 cylinders and 24 beams were cast and tested for compressive strength, splitting tensile strength and flexural strength using industrial wastes and the results presented. It was found that, the concrete made of waste ceramic tile aggregate produced more strength in compression, split tensile and flexure than ceramic insulator scrap and broken glass material. This paper recommends that waste ceramic tiles can be used as an alternate construction material to coarse aggregate in concrete.
This paper reports on the possibility of using natural renewable materials (hemp fibers and wood cellulose) in the preparation of lightweight composites. The reduction of carbon dioxide production during the manufacture of cement is one of the major aims of the building industry. Therefore, the effect of using different binding agents in combination with hemp slices in composites was examined. Conventional binders (such as hydrated lime and cement) in hemp concrete were replaced by alternative materials such as MgO and zeolite. The experimental examination of selected mechanical properties indicated that using zeolite as a cement replacement does not appear to create mechanically stronger hemp concrete. On the other hand, the magnesium oxide-cement system, based on optimally milled magnesium oxide, appears to be a suitable replacement for cement in lightweight composites, which could lead to new environmental products such as non-load bearing building materials. Wood cellulose is another very interesting material as a possible reinforcement in cement; it is a biodegradable, renewable, inexpensive, readily available natural resource, and it contributes to the reduction of greenhouse gases.
To evaluate the practical application of waste oyster shells (WOS) as controlled low-strength materials (CLSM), using a reference sample and four fine aggregate replacement 5%, 10%, 15% and 20% WOS sand, and the cement was replaced by 20% fly ash of the materials were tested. The hardened properties and the durability are tested and other various engineering properties are investigated. The experimental results demonstrate that there was no significant reduction in the compressive strength up to 20% of dosages of WOS sand instead of sand, and a proper amount of fly ash material and WOS sand for the replacement of the fine aggregate in cement mortar fills material pores, reduces the absorption rate. WOS sand can be resources of pure calcareous materials and effective in replacement of sand, indicating appropriate application of oyster shells, it is feasible to use in CLSM.
The paper reports on tests performed on sustainable “green” concrete using industrial hemp fibers. The incorporation of hemp in concrete would save on natural resources. The demand for hemp would be a major incentive to farmers to benefit from the social impact. In the experimental program, tests’ results on standard specimens for flexure, compression, splitting tensile, modulus of elasticity, thermal conductivity, density, and slump are presented. Results indicate that the use of industrial hemp fibers led to a reduction in coarse aggregate quantity without affecting the flexural performance of concrete, in addition to a significant enhancement in ductility of load–deflection behavior.
Benthic diatoms are a major component of biofilms that form on surfaces submerged in marine environments. Roughness of the underlying substratum affects the settlement of both diatoms and subsequent macrofouling colonizers. This study reports the effects of roughness on estuarine diatom communities established in situ in the Indian River Lagoon, FL, USA. Natural communities were established on acrylic panels with a range of surface roughnesses. Smoother substrata exhibited higher cell density, species richness, and diversity. Twenty-three of 58 species were found either exclusively or more abundantly on the smooth surfaces compared to one or both roughened treatments. The results suggest a greater ability of benthic diatoms to recruit and colonize smooth surfaces, which is probably explained by a higher degree of contact between the cells and the surface.
The response of epilithic microphytobenthos to in situ nutrient enrichments was studied in the Kiel Fjord, Western Baltic Sea. For this purpose an experimental setup with continuous nutrient supply was designed and installed. Experiments followed the colonization of artificial substrates and the responses of benthic algae to different concentrations and combinations of nitrogen and phosphate. They revealed nitrogen limitation of epilithic microflora from late spring to autumn, such that there was higher biovolume with increasing nitrogen concentrations. Diatoms became dominant in all experiments except one in which the rhodophyte Ceramium strictum prevailed. Species composition was altered by nutrient treatments; one to several species were highly favoured by nutrient enrichment. Consequently, diversity was negatively correlated with final yield. These findings support the hypothesis that competition is an important factor structuring microphytobenthic communities.
The effects of climate change and an expanding human population are driving the need for the expansion of coastal and marine infrastructure (CMI), the development of which is introducing hard substrate into the marine environment on a previously unseen scale. Whilst the majority of previous research has focussed on how physical features affect intertidal macrobiotic communities, this study considered the effects of differences in the chemical composition of concrete on subtidal biofilm and macrobiotic communities. Two commonly used cement replacements, pulverised fly ash (PFA) and ground granulated blast-furnace slag (GGBS), were used in a combination of proportions to assess how concrete tiles with differing surface chemistries affect development of early successional stages of marine biofouling communities. Controlled leaching experiments showed that although total metal leaching varied considerably between tile type, tiles containing GGBS resulted in statistically lower amounts of metal released compared with tiles containing PFA. Concrete treatment had no effect on the percentage cover or richness of diatoms, but there were significant increases in both over the duration of the experiment. Concrete treatments containing GGBS had a lower richness of native macro-fouling species compared to the control, but there was no significant difference in non-native species richness among treatments. Results suggest that different components can be used to alter the surface chemistry of concrete to further enhance the ecological value of CMI more than physical features can achieve alone.