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The role of seagrasses in coastal protection in a changing climate
Abstract
The contribution of seagrasses to coastal protection is examined through the review of the most relevant existing knowledge. Seagrasses are the largest submerged aquatic vegetation ecosystem protected in Europe and it is worth examining their contribution to coastal protection. The review performed highlights incident energy flux, density, standing biomass and plant stiffness as the main physical and biological factors influencing the efficiency of the protection provided by seagrasses. The main conclusion achieved is that seagrass meadows cannot protect shorelines in every location and/or scenario. The optimal conditions for enhancing the protection supplied might be achieved in shallow waters and low wave energy environments, with high interaction surface, at the vertical and horizontal dimension, between water flow and seagrasses. Likewise, the most favorable protection might be provided by large, long living and slow growing seagrass species, with biomass being largely independent of seasonal fluctuations and with the maximum standing biomass reached under the highest hydrodynamic forcings. It is shown that seawater warming, increasing storms and sea level rise, together with the increasing population and anthropogenic threats in the coastal area may lead to rates of change too fast to allow seagrasses to adapt and keep their coastal defense service. Finally, to amend the decline of seagrasses and consequent coastal protection loss, different artificial and natural adaptation measures are provided.
... Such structures pose maintenance costs that are impractical and therefore there is a demand for low-cost, resilient and sustainable solutions (Morris et al., 2018). Various forms of ecosystems in coastal environments (Kirwan and Megonigal, 2013;Rodriguez et al., 2014) such as seagrass meadows, salt marshes, dunes, biogenic reefs, etc. have a high capacity to protect the coasts against flooding and eroding via hydrodynamic energy dissipation, owing to the characteristics of the submerged vegetation and its associated structural complexities (Temmerman et al., 2013;Hanley et al., 2014;Ondiviela et al., 2014;Boudouresque et al., 2021;Da Ros et al., 2021). Contrary to the "hard" engineering structures, nearshore vegetated ecosystems can amplify the soil elevation and soil vertical acceleration on account of biomass accumulation from below the ground and particle trapping via the water column (Duarte et al., 2013;Potouroglou et al., 2017). ...
... Today, many studies support the application of NBS to overcome the limitations associated with purely rigid engineering structures, also named gray solutions (Nesshöver et al., 2017). Ondiviela et al. (2014) examined the contribution of seagrass to coastal protection through a review of the most relevant existing knowledge. While the main conclusion achieved is that seagrass meadows cannot protect shorelines in every location/scenario, it concludes that the role of seagrass in coastal protection should be actively included, and not be overlooked in coastal planning. ...
... Over the past few decades, numerous field and laboratory studies have been performed to determine the effects of vegetation on wave attenuation (Maza et al., 2013;Ondiviela et al., 2014;James et al., 2021). A 40 % reduction in wave heights during storm events, revealing the capacity of a dense seagrass meadow was reported by Ondiviela et al. (2014). ...
Worldwide, climate change adaptation in coastal areas is a growing challenge. The most common solutions such as seawalls and breakwaters are expensive and often lead to unexpected disastrous effects on the neighboring unprotected areas. In recent years, this awareness has guided coastal managers to adopt alternative solutions with lower environmental impact to protect coastal areas, defined as Nature-Based Solutions (NBSs). NBS are quite popular around the world but are often analyzed and implemented individually at pilot sites. This contribution analyzes the effectiveness of two NBS to mitigate coastal impacts (coastal flooding and erosion) under three historical storms along the Emilia-Romagna coasts and the induced improvements due to their potential integration. Through numerical simulations with XBeach, this study demonstrated that the presence of seagrass meadows of Zostera marina produces an average attenuation of 32 % of the storm peak with a maximum attenuation of 89 % in incoming wave height. Seagrass also mitigates flooded areas and maximum inundation depths by 37 % and 58 % respectively. The artificial dune leads to higher mitigation in terms of inundation of the lagoon (up to 75 %), also avoiding any morphological variations behind it. Seagrass has also been shown to be able to reduce beach erosion volumes up to 55 %. The synergic effect of the two NBS improves the capacity to mitigate both inundation (with a benefit of up to 77 % for flooded area attenuation with respect to cases without any defenses) and coastal erosion. Results of the study suggest that the two NBS will work together to produce co-benefits in terms of preservation of their efficiency, development of habitats for organisms and vegetation species, and thereby offering an important social value in terms of possible tourism, recreation and research.
... Seagrasses are defined as "ecosystem engineers" (Madsen et al., 2001;Denny, 2021) and include coastal ecosystems, which belong to a decidedly productive sector that provides crucial benefits (Orth et al., 2006;UNEP (United Nations Environment Programme), 2020;Young et al., 2021) such as biodiversity, nutrient cycling, etc. Seagrass meadows play a significant role in protecting coastal regions (Duarte et al., 2013;Ondiviela et al., 2014;Effrosynidis et al., 2018;Ondiviela et al., 2020) from associated flooding, erosion and storm surges. Seagrass landscapes are low-energy environments, with sediment deposition capacity (Gacia and Duarte, 2001;Ganthy et al., 2015), and which enable the resuspension of sediments (Amos et al., 2004;Widdows et al., 2008;Potouroglou et al., 2017;Zhu et al., 2021). ...
... In European coastal waters, in addition to Posidonia oceanica, there are three native species of seagrass: Cymodocea nodosa, Zostera noltii, and Zostera marina (Procaccini et al., 2003;Ondiviela et al., 2014;de los Santos et al., 2019;Oprandi et al., 2020). Zostera marina is an abundant species in the North Sea, and in the Baltic Sea. ...
... Zostera noltii is found on the coasts of Norway, the Black Sea, the Mediterranean Sea and produces dense meadows on the muddy sands in the intertidal regions. They have small and narrow leaves (2-5), which are 0.5-2 mm wide and 5-25 cm long; with many shoots on each rhizome (Borum et al., 2004;Ondiviela et al., 2014). Cymodocea nodosa is a warm water species widespread in the Mediterranean, on the African coast (to the north) and in the Canary Islands. ...
In this paper we demonstrate a novel framework for assessing nature-based solutions (NBSs) in coastal zones using a new suite of numerical models that provide a virtual “replica” of the natural environment. We design experiments that use a Digital Twin strategy to establish the wave, sea level and current attenuation due to seagrass NBSs.
This Digital Twin modelling framework allows us to answer “what if” scenario questions such as: (i) are indigenous seagrass meadows able to reduce the energy of storm surges, and if so how? (ii) what are the best seagrass types and their landscaping for optimal wave and current attenuation? An important result of the study is to show that the landscaping of seagrasses is an important design choice and that seagrass does not directly attenuate the sea level but the current amplitudes. This framework reveals the link between seagrass NBS and the components of the disruptive potential of storm surges (waves and sea level) and opens up new avenues for future studies.
... To verify this protective role of seagrass beds on beaches by attenuating hydrodynamics, a number of laboratory experiments were carried out (Anderson and Smith, 201 ;Augustin et al., 2009;Koftis et al., 2013;Lara et al., 2016;Manca et al., 2012;Maza et al., 201 ). These studies focused on the wave energy attenuation achieved due to the presence of plants. ...
... The surrogate was constituted by 2 pairs of leaves of 60 cm and 0 cm long each, all of them of 8 mm width mimicking an adult P Oceanica seagrass. These values are in the range of natural P Oceanica (Gacia and uarte, 2001;Ondiviela et al., 201 ;Ruiz et al., 201 ) who reported leaf lengths of up to 1 m and widths of up to 1 cm, grouped in clumps of up to 6 or leaves. This configuration is also in accordance with the experiments made by Manca et al., (2012). ...
... The values obtained in this work confirm what various authors ( uarte et al., 2013;Fonseca et al., 1982;Gacia and uarte, 2001;Koch et al., 2006;Ondiviela et al., 201 ) observed regarding seagrass beds and coastal protection. Carrying out tests with a low seagrass density (less than 300 stem m 2 ) in a common submergence ratio for this type of ecosystem (0.32), attenuation of wave heights can be generated, which could have a substantial impact on sedimentary dynamics, producing less erosion on the shoreline when higher waves are present. ...
New flume experiments with surrogate seagrass meadows are presented. The experiments included the creation of a full-scale and realistic Posidonia Oceanica model to evaluate the effect over wave attenuation, sediment transport and shoreline erosion. A hydrodynamic and morphodynamic comparison between cases with seagrass and without seagrass for two wave energy conditions was performed. Meadow density and submergence ratio were constant for tests under irregular waves. The wave height reduction, bar crest location, total sediment transport and shoreline position were used to evaluate the coastal protection efficiency of the meadow. The measured wave heights suffered a reduction due to the presence of the seagrass. These reductions were persistent in the area located between the onshore edge of the meadow and the depth of closure, being of greater magnitude in the more energetic case. All tests showed the development of a bar and the migration of the crest offshore over time. However, the dissipation of the incoming wave energy on the meadow made the bar crest stay closer to the shoreline and consequently generated a lower freeboard. In addition, the bar migration rate was reduced by the simulated meadow effect, in particular in the lower energetic case. A sediment volume significantly smaller was transported offshore when the seagrass meadow was present in both wave conditions. Additionally, in the higher energy case, a smaller shoreline retreat was observed when the meadow was present.
... Experiments have indicated that Posidonia oceanica meadows are effective at reducing wave energy, especially under low wave energy conditions and small wave amplitudes (Manca et al., 2012). Ondiviela et al., 2014 discuss the optimal conditions for enhancing protection by seagrass, such as shallow waters, low wave energy environments, with high interaction surface. They also compare native European seagrass species, among them Zostera marina and Zostera noltei (or Zostera noltii). ...
... Some authors state that Zostera noltei may reach very high densities in the Mediterranean area, over 20,000 stems/m 2 (Curiel et al., 1996;Ondiviela et al., 2014). For the Zostera noltei meadow in their study area on the Isle of Wight, Paul and Amos, 2011 discuss stem density values around 4600 stems/m 2 in summer and 600 stems/m 2 in winter. ...
The presence of seagrass along the Romanian coast is currently seen as an important component of the marine ecosystem. Moreover, seagrass meadows play an additional wave energy dissipation role that has also to be considered among other ecosystem services. Assessing the impact of a seagrass meadow on the local hydrodynamics is needed to present an integrated protection and adaption plan for discussion with local stakeholders and coastal managers. The impact on wave heights of a possible seagrass meadow, located in front of the barrier beach at the Mangalia marsh on the southern Romanian coast, has been analysed using numerical modelling. Several seagrass configurations have been studied, for low and average wave conditions from various directions. The same waves were used after adding a vegetation mask to the analysed domain, to simulate the presence of a seagrass meadow. The results of the numerical simulations were extracted in several output points, located along three transects crossing the vegetation mask. They show the most significant reduction in the calculated wave energy density during a year of 16.6%, occurring within the seagrass meadow. Our results suggest that, for the southern Romanian coast, seagrass could be introduced in coastal protection plans as an additional measure for wave attenuation.
... sand fences; Khalil andLee 2006, Bocamazo et al. 2011). Despite never having been explicitly tested as an NbS for coastal protection, there is ample evidence of seagrass meadows' effects on wave, current and sediment dynamics (Koch et al. 2006, Ondiviela et al. 2014 and references therein). Although several articles illustrate the efficiency and feasibility of different coastal NbS in different areas, seagrass restoration is largely absent from the coastal protection literature and to date, no seagrass restoration projects have been carried out specifically targeted for coastal protection purposes (Narayan et al. 2016, Paul 2018). ...
... The absence of seagrass restoration projects targeted for coastal protection is probably not due to a lack of evidence on the hydrodynamic functions such as modulating flow velocities (van Rooijen et al. 2018), attenuating waves (Bradley andHouser 2009, Reidenbach andThomas 2018) and stabilizing and accreting sediment (Bos et al. 2007) that seagrass meadows provide (summarized in Koch et al. 2006, Ondiviela et al. 2014. Rather, it could be because newly planted seagrass shoots are very sensitive to high levels of wave exposure and sediment movement and are unlikely to provide significant coastal protection in exposed areas or in the event of a major storm (Paling et al. 2003, van Keulen andBorowitzka 2003). ...
Coastal protection has evolved from focusing on hard solutions such as breakwaters and groynes to include soft or nature‐based solutions (NbS). NbS have been proposed as cost‐effective means to offer long‐term coastal protection and at the same time strengthen coastal resilience and biodiversity. However, projects utilizing NbS for coastal protection have often focused on a single solution and the evidence of improved biodiversity remain equivocal. In this paper, we review solutions traditionally used for disparate purposes – namely beach nourishment and the establishment of vascular plants such as seagrass and dune grass. The main incentives behind large‐scale beach nourishment projects are often the cost‐effectiveness, multifunctionality and dynamic shoreline protection whereas the focus of vegetation restoration has typically been on recreating important habitats and not specifically as a coastal protection measure. Based on previous studies and an on‐going large‐scale coastal adaptation project in southern Sweden, we investigate the feasibility of combining these seemingly dichotomous management strategies to yield a viable physical defense and at the same time strengthen coastal biodiversity and ecosystem multifunctionality. Given the urgency in combatting biodiversity loss and adapting to a changing climate, management interventions for coastal protection should explicitly incorporate ecological values into every coastal protection measure and seek innovative, integrated approaches that consider both geomorphological and ecological values and the possible complementarity between the two.
... Our interest in coastal protection lies not in the seagrass meadow itself but in the morphodynamic response of the adjacent shoreline to the presence of the seagrass meadow, which has not been quantified empirically in the literature. In some cases, seagrass presence or absence will not affect erosion (Ondiviela et al., 2014). For example, in the shallow beaches on the Adelaide Coast, South Australia, seagrass helps to maintain the beach width in everyday wave conditions but has little effect during extreme weather events (Fotheringham, 2002). ...
... These differences may be attributed to the highly variable and nonlinear spatial and temporal processes (Koch et al., 2009;Barbier et al., 2008) of seagrass-induced wave attenuation. This high variability impedes the use of existing data for predicting wave attenuation in different sets of wave and vegetation conditions (Ondiviela et al., 2014;Ruiz-Frau et al., 2017). ...
Coastal ecosystems, such as seagrass meadows, have been heralded as a nature-based solution for coastal protection. However, the functions of seagrass meadows, including wave attenuation and sediment stabilisation, have typically been measured offshore and do not directly translate to coastal protection at the shoreline. In contrast, the protective effects of conventional submerged structures, such as breakwaters and artificial reefs, on adjacent shorelines have been well described and are predictable. Importantly, these artificial structures often cause erosion in adjacent areas. This study examines how seagrass may affect shoreline morphodynamics by making inferences from existing knowledge of conventional submerged structures. Both conventional submerged structures and seagrass meadows affect wave height and direction, yet this effect on longshore sediment transport has only been considered within the context of coastal defence structures. From the conventional literature on submerged structures, it is known that a constant rate of longshore sediment transport will result in a constant shoreline shape. Therefore, a change in the rate of longshore sediment transport, or gradient, generates changes in the shoreline shape and, hence, the shoreline morphodynamics. We propose that seagrass also has spatially heterogeneous effects on shoreline morphodynamics, with protection occurring in some locations and downstream erosion likely in others. Empirical and modelling research is required to test this hypothesis. In the meantime, this review suggests contexts under which seagrass may affect shoreline morphodynamics and provide shoreline protection. This research bridges the gaps in knowledge across marine ecology, physical oceanography and coastal engineering to overcome some of the challenges of interdisciplinary coastal science.
... In the Mediterranean Sea, rocky hard-bottom communities and commonly identified biodiversity hotspots such as seagrass meadows are declining primarily due to environmental pressures 5,6,19,20 . Meadows formed by Posidonia oceanica seagrass rank amongst the most valuable coastal ecosystems worldwide as they provide a range of goods and ecosystem services 21,22 , e.g., they exhibit high biodiversity, function as ecosystem engineers, and can act as natural coastal protection barriers 23 . P. oceanica meadows consist of the rhizome layer (often up to several m thick) 24 and the leaf canopy. ...
... Similar to coral reefs or mangrove forests, seagrass meadows can persist for several millennia 75 , which exceeds the currently estimated lifespan of P. crispa formations (i.e., decades) 30 . The evolved size and physical structure of seagrass meadows can result in a dissipation of wave energy on multiple levels (reviewed in ref. 23 ) and reduce coastal damage and erosion. Wave energy is a key limiting factor defining the upper physical boundary that shapes the bathymetric spatial distribution for P. oceanica meadows 76 . ...
Many coastal ecosystems, such as coral reefs and seagrass meadows, currently experience overgrowth by fleshy algae due to the interplay of local and global stressors. This is usually accompanied by strong decreases in habitat complexity and biodiversity. Recently, persistent, mat-forming fleshy red algae, previously described for the Black Sea and several Atlantic locations, have also been observed in the Mediterranean. These several centimetre high mats may displace seagrass meadows and invertebrate communities, potentially causing a substantial loss of associated biodiversity. We show that the sessile invertebrate biodiversity in these red algae mats is high and exceeds that of neighbouring seagrass meadows. Comparative biodiversity indices were similar to or higher than those recently described for calcifying green algae habitats and biodiversity hotspots like coral reefs or mangrove forests. Our findings suggest that fleshy red algae mats can act as alternative habitats and temporary sessile invertebrate biodiversity reservoirs in times of environmental change.
... Seagrasses are important globally spread coastal ecosystems which provide essential ecosystem services (Short et al., 2007). These services include habitat for fish, carbon sequestration (Barbier et al., 2011;Fourqurean et al., 2012) and reduction of hydrodynamic energy (Ondiviela et al., 2014). Despite these known services, almost a third of seagrass cover has been destroyed mostly due to human activity since records started during the late 19th century (Waycott et al., 2009). ...
... A density of N = 400 shoots m −2 was chosen, which results in a frontal area per canopy volume a = 1.92 m −1 (Nepf, 2011). The chosen shoot density and stem length is akin to those found in nature for strap-like seagrasses such as Zostera marina (e.g., Ondiviela et al., 2014). Albeit not biodegradable, PA was chosen based on target mechanical properties of ASG used for restoration, which may potentially be used in the field (Bouma et al., 2005). ...
Our new article goes deeper into a proposed approach for seagrass restoration, namely, the use of artificial seagrass mats. These mats need to be anchored to the seabed, but the forces on the anchors are not known and have not been investigated in any similar way. We, therefore, test the anchor forces on mats laid on the seabed with and without artificial seagrass and analyze the forces that occur depending on differing hydrodynamic conditions.
The article is Open Access and can be freely downloaded following the DOI link above!
... Being primary producers, they are the base of food webs, providing food, oxygen, and refuge to other organisms and communities (Almanza and Buschmann, 2013;Vásquez et al., 2014) and therefore they are responsible for biodiversity support (Skjermo et al., 2014). Moreover, seaweeds contribute to the coastal defense, change the environment by modifying light, sedimentation rates and reduce the hydrodynamic energy from waves and protect tidal areas from erosion (Reisewitz et al., 2006;Leclerc et al., 2013;Smale et al., 2013;Ondiviela et al., 2014;Bertocci et al., 2015). ...
... Seagrass meadows are essential components of softbottom coastal ecosystems worldwide. Seagrasses are important primary producers (Larkum et al. 2006) and their meadows contribute to coastline protection (Ondiviela et al. 2014), sediment stabilization (Newell and Koch 2004), the cycling of nutrients (McGlathery et al. 2007) and carbon sequestration (Mazarrasa et al. 2015). Moreover, they provide habitat and shelter for numerous marine species and thereby are known as important hotspots of biodiversity (Hyman et al. 2019). ...
... Fish species display a distinct preference for particular seagrasses characterised by different architecture 39 and shifts in seagrass species composition can lead to changes in the abundance and diversity of fish and other macrofauna such as crabs and shrimp 40 . Stiffness, biomass, density, leaf length and morphology all influence the coastal protection value of seagrasses, with large, long living, slow growing seagrass species affording the greatest protection 41 . Species composition is a known contributor to variability in carbon stocks 42 with larger bodied species generally associated with higher sedimentary organic carbon stocks. ...
Report cards that are designed to monitor environmental trends have the potential to provide a powerful communication tool because they are easy to understand and accessible to the general public, scientists, managers and policy makers. Given this functionality, they are increasingly popular in marine ecosystem reporting. We describe a report card method for seagrass that incorporates spatial and temporal variability in three metrics—meadow area, species and biomass—developed using long-term (greater than 10 years) monitoring data. This framework summarises large amounts of spatially and temporally complex data to give a numeric score that provides reliable comparisons of seagrass condition in both persistent and naturally variable meadows. We provide an example of how this is applied to seagrass meadows in an industrial port in the Great Barrier Reef World Heritage Area of north-eastern Australia.
... The value of seagrass, that is qualitative or quantitative, economic, ecological or existence, is indisputable [1, 14,15]. In a tropical and sub-tropical context and indeed on a global scale, seagrass plays a major role in food security [16], coastal protection [17], provision of habitat and food for charismatic and endangered species such as dugongs and sea turtles, as well as climate change mitigation through carbon sequestration and storage [1] and provision of livelihoods for coastal communities [18]. However, those critical habitats are threatened by several land-and ocean-based threats, and climate change drivers [19,20]. ...
The onset of a major seagrass initiative in West Africa enabled important seagrass discoveries in several countries, in one of the least documented seagrass regions in the world. Four seagrass species occur in western Africa, Cymodocea nodosa, Halodule wrightii, Ruppia maritima and Zostera noltei. An area of about 62,108 ha of seagrasses was documented in the studied region comprising seven countries: Mauritania, Senegal, The Gambia, Guinea Bissau, Guinea, Sierra Leone and Cabo Verde. Extensive meadows of Zostera noltei were recorded for the first time at Saloum Delta, Senegal, which represents the new southernmost distribution limit of this species. This paper also describes the seagrass morphology for some study areas and explores the main stressors to seagrasses as well as conservation initiatives to protect these newly documented meadows in West Africa. The produced information and maps serve as a starting point for researchers and managers to monitor temporal and spatial changes in the meadows’ extent, health and condition as an efficient management tool.
... Seagrass meadows protect coastal areas from erosion due to their ability to trap fine sediments and their impact on dynamics and resuspension of sediment (Van Katwijk et al., 2010). The optimal utilization is in shallow waters with low wave conditions (Ondiviela et al., 2014). A study in Tun Mustapha Park, Malaysia, found that seagrasses in Karakit, Banggi Island, help reduce erosion by trapping sediments (Saleh* and Jolis, 2018). ...
... There are three mechanisms by which Posidonia meadows contribute directly to the protection of the coast by decreasing the intensity of incoming energy: (1) energy dissipation due to wave breaking, (2) energy dissipation due to friction, and (3) energy reflection in the offshore direction (Duarte et al., 2013;Koch et al., 2006). Several initiatives have been developed proposing ecological mitigation actions using seagrasses, particularly Posidonia, to reduce the risk of flooding and erosion (Ondiviela et al., 2014). The total coastline of the central part of Gulf of Gabes is about 250 km from Djerba Island to Ras Thyna (Fig. 2). ...
In the early XXth century, the Gulf of Gabes in SE Tunisia used to host the most extended Posidonia oceanica seagrass beds in the Mediterranean basin and was a highly productive hotspot of benthic species. Since the 70's, >500 million t of wet toxic phosphogypsum discharges from a fertilizer industrial complex have led to the gradual loss of ∼90 % of its initial surface. This drastic shrinkage is accompanied by significant value losses originated from the direct and indirect-use services of which the most important ones are small scale fisheries and carbon storage function. Using market valuations of a number of services we estimate economic losses at 105 million € in 2014 (∼915€/ha), i.e., around 115 % of the added value of the gabesian fertilizer factories for the same year. Value losses should increase in the near future in relation with the COP26 agreements which boosted the open carbon credit market. Without actions to reduce negative production externalities caused by the fertilizer industry in the Gulf of Gabes it would not be possible to recover Posidonia ecosystems in this region leading to further economic, ecologic, and cultural losses.
... Seagrass canopies can decrease the flow of water, thereby promoting sediment deposition and limiting sediment resuspension (Gacia and Duarte 2001;Koch et al. 2006). The capacity of seagrass meadows to buffer hydrodynamic energy is higher in larger species compared to smaller ones (Ondiviela et al. 2014; Barcelona et al. 2021). In addition, large and persistent species develop larger below ground biomass and more refractory tissues than small and deciduous species, enhancing the role that seagrass meadows play as long-term carbon sinks (Trevathan-Tackett et al. 2017). ...
Seagrass meadows composed of larger species are assumed to store larger sediment organic carbon (Corg) stocks, storing more Corg in their tissues and larger leaves promoting greater burial of seagrass and non‐seagrass Corg. However, the influence of species composition on sediment Corg stocks remains poorly understood mainly from challenges in isolating it from confounding factors. We assessed Corg stocks in seagrass biomass and sediment of four species compositions in a tropical Caribbean meadow. We hypothesized that larger species would lead to higher sediment Corg stocks, within a limited geomorphic setting and time frame. Seagrass biomass and surficial and sediment profiles were collected to measure seagrass morphometrics, δ13C and δ15N, dry bulk density, Corg and inorganic carbon (Cinorg) stocks, and grain size. Seagrass biomass Corg stocks ranged from 0.04 to 3.7 Mg ha−1, with higher biomass Corg stocks in compositions with larger species. Surficial sediment Corg and Cinorg stocks (to 1.5 cm) averaged 2.6 ± 0.6 Mg Corg ha−1 and 68.8 ± 14.6 Mg Cinorg ha−1, respectively, and did not vary among species compositions. Isotopic analyses revealed a ~ 50% contribution of seagrasses to surficial sediment Corg in compositions with larger species, compared to a contribution of ~ 35% for those of smaller species. This study provides novel blue carbon data from an understudied region and contributes to understanding the role of seagrass species composition on sediment carbon storage.
... Coastal vegetated ecosystems, including seagrass meadows, mangroves, and saltmarshes, play a vital role in sustaining marine biodiversity fisheries (Perkins-Visser, Wolcott & Wolcott, 1996;Verweij et al., 2008;Jänes et al., 2020). In addition, coastal vegetated systems are expected to play an increasingly important role in mitigating the impacts of climate change over the next decades, due their well-documented contributions to coastal protection (Ondiviela et al., 2014) and carbon sequestration (Fourqurean et al., 2012;Githaiga et al., 2017;Hilmi et al., 2021). Seagrass meadows, in particular, are known to be excellent carbon traps, especially in sediment, sequestering up to 30× more carbon than rainforest areas of similar size, and are estimated to contain between 4.2 and 8.4 PG carbon on a planetary scale (Fourqurean et al., 2012). ...
Worldwide seagrass populations are in decline, calling for urgent measures in their conservation. Glyphosate is the most widely used herbicide globally, leading to increasing concern about its ecological impact, yet little is known about the prevalence or impact of glyphosate on seagrasses. In this study, we investigated the effect of sublethal glyphosate exposure on the endangered seagrass, Zostera capensis , to identify effects on growth, photosynthetic pigments and leaf morphology as measures of seagrass fitness. Seagrasses were exposed to a single dose of a commercial glyphosate formulation—ranging between 250 to 2,200 µg/L. After three weeks, the median leaf area decreased by up to 27%, with reductions of up to 31% in above ground biomass ( p < 0.05). Photosynthetic pigment concentration showed no significant difference between groups. The observed effects on biomass and leaf area were seen at glyphosate levels below the regulatory limits set for surface water by several countries and may negatively affect the long-term resilience of this ecosystem engineer to additional stressors, such as those associated with climate change and anthropogenic pollution. As such, glyphosates and other herbicides that are washed into estuarine and marine ecosystems, pose a significant threat to the persistence of seagrasses and are important factors to consider in seagrass conservation, management and restoration efforts.
... Le praterie possono inoltre garantire protezione alle coste, fattore che, a seguito del cambiamento climatico, diventa di vitale importanza per contrastare l'innalzamento del livello del mare e la maggior frequenza di eventi estremi, come inondazioni o tempeste; questa capacità è ancora più importante in paesi insulari con altezza media sul livello del mare inferiore ad 1 m (Borsje et al., 2011;Duarte, Losada, et al., 2013;Koch et al., 2009). La protezione della linea di costa è il risultato della sinergia tra la capacità di riduzione dell'energia idrodinamica e la stabilizzazione del sedimento (Ondiviela et al., 2014) operata dalla prateria. L'energia idrodinamica, o idrodinamismo, viene ridotta tramite tre processi principali: ...
Monitoraggio temporale dell’espansione della prateria di fanerogame presente sull’isola di Magoodhoo, Maldive. Il monitoraggio è durato 5 anni e i dati sono stati ottenuti tramite sorvoli effettuati da drone. I dati sono stati successivamente elaborati tramite tecniche fotogrammetriche e algoritmi OBIA (Object Based Image Analysis) così da ottenere modelli tridimensionali dell’area di studio sui quali è stata riconosciuta e misurata l’estensione della prateria. Il riconoscimento e le misure sono state effettuate utilizzando eCognition e ArcMap. Inoltre è stato possibile attraverso valori tabulati stimare la quantità di anidride carbonica “Assorbita” dalla prateria nei diversi anni.
... Changes in carbon concentrations within the tissues, which play a key role in mitigating anthropogenic CO 2 emissions under the current climate change scenario, may ultimately affect carbon storage capacity (Armitage and Fourqurean, 2016). The disproportional carbon concentrations may eventually cause a biomass imbalance, changing the above-ground:belowground ratio, which is involved in sediment stabilization and oxygenation of the sediments (Ondiviela et al., 2014). In contrast, increasing carbon reserves in the rhizome is related to the energy supply under stressful events, therefore, providing seagrass with a potential advantage to cope with eventual local stressors such as light deprivation or physical disturbances caused by anchoring or bivalve harvesting (Jiang et al., 2010). ...
Understanding species-specific trait responses under future global change scenarios is of importance when doing conservation efforts and to make informed decisions within management projects. The combined and single effects of seawater acidification and warmer average temperature were investigated by means of the trait responses of Cymodocea serrulata, a tropical seagrass, under experimental conditions. After a 35-days exposure period, biochemical, morphological and photo-physiological trait responses were measured. Overall, biochemical traits mildly responded under the individual exposure of high temperature and increasing pCO2 values. The response of C. serrulata was limited to a decrease in %C and an increase in the sucrose content in the rhizome under the high temperature treatment, 32°C. This suggests that this temperature was lower than the maximum tolerance limit for this species. Increasing pCO2 levels increased %C in the rhizome, and also showed a significant increase in leaf δ 13C values. The effects of all treatments were sub-lethal, however, small changes in their traits could affect the ecosystem services they provide. Particularly, changes in tissue carbon concentrations may affect carbon storage capacity, one key ecosystem service. The simultaneous study of different types of trait responses contribute to establish a holistic framework of seagrass ecosystem health under climate change.
... From the sub-to the supralittoral, sandy habitats are important in preventing coastal erosion and flooding, but their value may be enhanced by the many biological processes that complement or even increase their role in coastal defense. For example, in addition to their role in nourishing other sandy systems, shallow, sub-tidal sands also support seagrass beds, a habitat increasingly recognized as important for coastal protection due to their ability to stabilize and accumulate sediment, and attenuate and dissipate waves (Christianen et al. 2013;Ondiviela et al. 2014). ...
... Seagrasses are monocotyledonous flowering plants habituating the submerged areas of coastal waters. They provide a wide range of ecosystem services to coastal communities, including coastal protection (Ondiviela et al., 2014;Christianen et al., 2013), storage of sedimentary carbon (Mateo et al., 2006), pathogen reduction (Lamb et al., 2017) and the provision of nursery grounds for many species that support fisheries (Heck et al., 1997;Nordlund et al., 2018). Despite their important ecological and socio-economic values, seagrasses are being lost at an annual rate of 7% worldwide due to global natural and anthropogenic threats, and by nearly 20% in the Tropical Indo-Pacific and Temperate Southern Oceans (Dunic et al., 2021). ...
Although seagrass restorations have been conducted at many regions globally, restorations in high-energy wave environments are less explored. With accelerating losses of seagrass meadows, we also lose valuable ecosystem-based adaptations and ecosystem services, where the Western Indian Ocean is not an exception. The coast of Tanzania has only a few island shelters, creating an open exposed coast with a long wind fetch, generating strong wave exposure on the coastline. Still, seagrass meadows are present but have similar to global trends declined due to e.g. warmer ocean temperatures, coastal developments and destructive fishing methods. In view of the above challenges, there is a strong need for restoring seagrass meadows along the coast of Tanzania and the western Indian Ocean at large. However, restoration studies in the WIO are scarce and generally lacking in Tanzania. Studies elsewhere have shown that the success of a seagrass restoration varies significantly among trials and is to a large extent subject to the choice of planting technique. Thus, in order to initiate a best practice for seagrass restoration in the Western Indian Ocean Region, for high-energy wave intertidal environments, we contrasted two restoration techniques, the plug and the sprig method. We further explored different anchoring techniques and how various physical environmental factors influenced the growth and survival rates of seagrass shoots and rhizomes. We found that Syringodium isoetifolium transplants survived poorly using the sprig method, while the plug method demonstrated a much higher survival rate: 33.3% for the 7 cm corer, and 66.7% for the 10 cm corer. The study also revealed a strong effect of water depth, where survival and growth parameters decreased with increased water depth. Finally, the study found a number of significant correlations, both positive and negative, between growth parameters and measured environmental factors – and revealed that most of the measured environmental parameters were influenced by the local weather conditions and the monsoon seasonal cycling. The study illustrates that the restoration technique is strongly related to restoration success, providing clear guidance for future seagrass restorations in high-energy coasts in the Western Indian Ocean.
... E. acoroides was selected because the species is large, long living and slow growing seagrass species and hence provide most protection (Ondiviela et al., 2014). Shoots of E. ...
The erosion of the small island coast is a topic that is of concern throughout the world because it can cause huge losses of coastal land (residential), habitat, and the island. Traditional methods of coastal protection using hard structures such as wave breaker, groins, and revetments/seawall are currently recognized as not environment-friendly and costly. Coastal protection systems can benefit from ecosystem engineers like seagrass (marine submerged vegetation). Seagrasses are able to significantly influence the hydrodynamic environment by reducing current velocity, dissipating wave energy and stabilizing the sediment, and hence they are very potential to be use as a natural and sustainable coastal protection. In this study, a large, long living and slow growing seagrass species (Enhalus acoroides) transplantation experiment was conducted at two stations with different level of wave exposure in an eroding small island coast to assess the feasibility of using seagrass beds for coastal protection. Vegetative shoots (sprigs) of E. acoroides were collected from a healthy donor bed located nearby the plantation site, and planted into unvegetated areas. Test-transplant survival was assessed every month. The survival rates of transplants were lower in the east side of the island. The difference in
survival rates of transplanted seagrass due to difference in wave exposure of two transplanting stations is discussed.
... Marine seagrasses has been gaining wide attention due to their ability to grow in brackish waters and the ease of effluent treatment in sea or seashores . Seagrasses also provides a large number of valuable services to the environment like coastal defense, carbon sequestration, and food sources and habitat for different organisms (Luisetti et al., 2013;Ondiviela et al., 2014). The earliest in-situ evidence revealed microplastics binding to seagrasses via encrustation, to macrophyteassociated epibionts, as well as to the mucus layer (Seng et al., 2020). ...
Microplastics have been identified as an emerging pollutant due to their irrefutable prevalence in air, soil, and particularly, the aquatic ecosystem. Wastewater treatment plants (WWTPs) are seen as the last line of defense which creates a barrier between microplastics and the environment. These microplastics are discharged in large quantities into aquatic bodies due to their insufficient containment during water treatment. As a result, WWTPs are regarded as point sources of microplastics release into the environment. Assessing the prevalence and behavior of microplastics in WWTPs is therefore critical for their control. The removal efficiency of microplastics was 65 %, 0.2–14 %, and 0.2–2 % after the successful primary, secondary and tertiary treatment phases in WWTPs. In this review, other than conventional treatment methods, advanced treatment methods have also been discussed in this review. For the removal of microplastics in the size range 20–190 μm, advanced treatment methods like membrane bioreactors, rapid sand filtration, electrocoagulation and photocatalytic degradation was found to be effective and these methods helps in increasing the removal efficiency to >99 %. Bioremediation based approaches has found that sea grasses, lugworm and blue mussels has the ability to mitigate microplastics by acting as a natural trap to the microplastics pollutants and could act as candidate species for possible incorporation in WWTPs. Also, there is a need for controlling the use and unchecked release of microplastics into the environment through laws and regulations.
... Seagrass meadows generally present a higher biodiversity than the surrounding unvegetated marine areas (e.g., Brasier, 1975;Hirst and Attrill, 2008;Barnes and Barnes, 2012). They provide indisputable ecosystem benefits and services (Sanchez-Vidal et al., 2021), including water quality improvement (de los Santos et al., 2020), carbon dioxide sequestration (Deyanova et al., 2017), stabilization of the seafloor, coastal protection and sediment production (Gacia et al., 2003;Ondiviela et al., 2014), and climate change mitigation (Duarte et al., 2013). With the term "seagrass meadows", we identify large stretches of shelf environment (up to 100s m 2 ) dominated by marine angiosperms (e.g., Posidonia spp., Cymodocea spp.) (Reich et al., 2015b). ...
This paper analyses and describes the benthic foraminiferal associations within the Pleistocene deposits of the Stirone River (Emilia-Romagna, Italy), with the purpose of testing foraminifera as Indirect Palaeo-Seagrass Indicators (IPSIs). Our analyses focused on two different biofacies: a Thalassinoides biofacies, characterised by an oligotypic biotic assemblage and a Pinna biofacies representing an infralittoral soft bottom colonised by marine phanerogams and characterized by high biodiversity. To strengthen the analyses, we have compared the Stirone foraminiferal association with the one of Fauglia (Tuscany, Italy), in which a well-preserved, early Pleistocene, fossil Posidonia meadow, is present. The aim of this work is to provide qualitative and quantitative parameters that can be used to recognize past vegetated environments, where fossil seagrass are no longer present. Considering the influence of ecological constraints and diagenetic processes on the foraminiferal assemblages, several indexes such as the Index EP , the modified FORAM index (FI'), the "long vs. short lifespan index" (I LS), and the K/R EXT (keeled/rounded morphotypes) have been calculated and a morphotype-based analysis has been provided. Among the tested indexes, the latter proved to be the most reliable IPSI, in association with the presence of morphotype A*, permanently attached, encrusting foraminifera and the abundance of Rosalinidae.
... Seagrass meadows protect coastal areas from erosion due to their ability to trap fine sediments and their impact on dynamics and resuspension of sediment (Van Katwijk et al., 2010). The optimal utilization is in shallow waters with low wave conditions (Ondiviela et al., 2014). A study in Tun Mustapha Park, Malaysia, found that seagrasses in Karakit, Banggi Island, help reduce erosion by trapping sediments (Saleh* and Jolis, 2018). ...
Southeast Asia is an area of rich marine biodiversity providing a host of ecosystem services that contribute to the well-being of coastal communities and beyond. Sustainable management of ecosystems and the services they provide requires a good understanding
of their underlying ecological functions and processes. This understanding can be gained through the rigorous assessment of studies identifying and quantifying ecological functions and ecosystem services.
The aims of this study were to review the ecosystem services provided by marine and coastal habitats in Southeast Asia. The ecosystem service potential was scored for each habitat. The review was focused on nine key marine and coastal habitats, identified across four case study sites in Southeast Asia, contributing 18 marine relevant ecosystem services. The approach comprised a literature review supplemented with observations from experts from the case study areas. The four case study sites consist of three Man and Biosphere Reserves in Southeast Asia: Palawan in the Philippines, Cu Lao Cham- Hoi An in Viet Nam, Take-Bonerate Kepulauan Selayar in Indonesia, and a recently gazetted marine protected area, the Tun Mustapha Marine Park in Malaysia.
The nine key habitats (eight benthic and one pelagic) covered in this review, identified as highly relevant for most case study sites, were mangrove forests, coral reefs, seagrass meadows, sand, mud, rock, coarse substratum, pelagic and modified habitats. Further division of these habitats into sub-habitats on the basis of biological type and substrate type was used to capture data on differential provision of ecosystem services within the broad habitat types.
... For preventing erosion rate, marine habitats seagrass meadows such as P. oceanica and Cymodocea nodosa, as well as coralligenous bioconstructions, play a major role. The attenuation effect of P. oceanica on the hydrodynamics is related to the wave height attenuation, wave energy decay and reduction in the sediment transport in wave-current [47][48][49]. Flow indicator (F) accounted for the extent of maintenance and improvement required to provide protection [50]. The seagrass meadows extension was used to assess the "Regulation of chemical composition of atmosphere and oceans" ES. ...
The paper focuses on the integrated environmental accounting model called “eValue” developed for protected areas and applied in the re-search programme coordinated by the Italian Ministry of Environment aiming to implement an environmental accounting system for the Italian Marine Protected Areas (MPAs). eValue aimed to calculate the economic value of Protected Areas adopting a Cost-Benefit Analysis approach. Financial accounting based on costs and revenues was integrated with environmental accounting, which reflected not only environmental costs but also environmental revenues, i.e. environmental benefits. Environ-mental costs assessed the impacts related to human activities in the MPA and environmental benefits assessed ecosystem services. The overall annual flow account accounted for costs and benefits, both economic and environmental, and the difference represented the value produced (or consumed) by the MPA. The eValue model was applied in the Tremiti Islands MPA. eValue demonstrated that the annual benefits-costs ratio reaches 2.1. In addition, the ratio between the net benefit and the public funding is 5.0 completely covering the amount of public transfers and thus summarizing the overall value for money of the MPA. Finally, the outcomes of the project are functional to the Mapping and Assessment of Ecosystem Services initiative carried out by the European Union.
... For preventing erosion rate, marine habitats seagrass meadows such as P. oceanica and Cymodocea nodosa, as well as coralligenous bioconstructions, play a major role. The attenuation effect of P. oceanica on the hydrodynamics is related to the wave height attenuation, wave energy decay and reduction in the sediment transport in wave-current [47][48][49]. Flow indicator (F) accounted for the extent of maintenance and improvement required to provide protection [50]. meadows extension was used to assess the "Regulation of chemical composition of atmosphere and oceans" ES. ...
The article focuses on the integrated environmental accounting model called 'eValue', developed for protected areas and applied in the research programme coordinated by the Italian Ministry of the Environment and aimed at implementing an environmental accounting system for Ital-ian Marine Protected Areas (MPAs). eValue adopts a cost-benefit analysis approach. Financial accounting based on costs and revenues is integrated with environmental accounting, which reflects environmental costs and environmental revenues, i.e., environmental benefits. The environmental costs assess the impacts related to human activities in the MPA expressed by calculating the carbon footprint and the environmental benefits of the marine ecosystem services calculated by applying monetary valuation techniques. The values thus estimated flow into the annual flow account, where the value produced (or consumed) by the MPA is estimated by difference. The eValue model was applied to the Porto Cesareo MPA (Italy). eValue showed that the annual benefit-cost ratio reaches a value of 3.4. Furthermore, the ratio of net benefit to public funding is 3.7, completely covering the number of public transfers and thus summarizing the MPA overall value for money.
... So izjemnega pomena, saj nudijo bivalne niše, hrano in zavetje pred plenilci mnogim pomembnim organizmom v lagunskih in morskih ekosistemih [3]. Ta zelo produktivna okolja zelo pomembna za dobrobit človeka [4], [5], saj zagotavljajo številne ekosistemske storitve, kot so umirjanje delovanja valov s posledično zaščito obale pred erozijo, [6], stabilizacija sedimentov [7], [8], urejanje ciklov hranil in sekvestracija ogljika [9], čiščenje morske vode [10] ter predstavljajo sistem za izobraževanje in raziskave [11]. Ob tem so to kritična območja za mnoge vrste tarčnih morskih organizmov z vidika ribištva, še posebej kot zatočišča ribjih mladic [12]. ...
V obdobju digitalne preobrazbe družbe na pomenu pridobivajo tudi informacijske tehnologije. Sem sodijo geografski informacijski sistemi, ki povezujejo lokacijske podatke z vsemi vrstami opisnih informacij, in s tem zagotavljajo osnovo za kartiranje in prostorsko analizo. Slednja se dandanes uporablja tako v znanosti kot v industriji. S pomočjo tovrstne analize lažje razumemo pretekle in sedanje prostorske vzorce, ki so posledica interakcije naravnih in družbenih razmer. Na podlagi zaznanih trendov lahko nato celo ocenjujemo, kakšen bo nadaljnji prostorski razvoj. Prav zmožnost objektivnega napovedovanja je ena izmed ključnih lastnosti, ki dodatno poveča uporabnost prostorskih analiz z vidika vrednotenja posledic podnebne ali bolje okoljske krize. Prav to dejstvo je povod za nastanek monografije z naslovom Primeri prostorskih analiz vplivov podnebnih sprememb. Monografija je razdeljena na tri poglavja. Prvo obravnava urbana okolja in se dotakne problematike vse pogostejšega toplotnega stresa kot posledice pojava mestnega toplotnega otoka (MTO) in toplejše atmosfere zaradi (antropogeno pospešenih) podnebnih sprememb. Drugo poglavje monografije obravnava vplive podnebnih sprememb na izbrane habitate kulturne krajine, bodisi v intenzivni ali ekstenzivni kmetijski rabi. V tretjem poglavju pa se vsebinsko premaknemo iz kopenskih na obmorska in morska okolja.
... The loss of this biodiversity support function subsequently impacts the provision of fisheries, water purification, and coastal protection services [7]. Seagrass meadows are an important coastal habitat that provides numerous ecosystem services [8][9][10], not least in the tropical Indo-Pacific region, which boasts the highest seagrass diversity [11], despite a trending decline in extent [12]. In this region, seagrass meadows are threatened by local stressors including, but not limited to, overfishing, seaweed farming, gleaning, and coastal development [13][14][15][16][17][18][19]. ...
It is widely recognized that humanity is currently facing multiple planetary crises, including the widespread loss of biodiversity and a rapidly changing climate. The impacts of these crises are often far reaching and threaten food security (SDG goal two: zero hunger). Small-scale fisheries are estimated to provide livelihoods for over one hundred million people and sustenance for approximately one billion people but face a plethora of threats and challenges linked to planetary crises. In this multi-country assessment (150 coastal villages across five countries within the Indo-Pacific), household interviews revealed how seagrass meadows are important to small-scale fisheries, particularly as a place to find and collect a reliable source of food. Interviews also revealed that habitat loss and the over-exploitation of these resources are placing people and their food security at risk. This study exposed how dynamic local ecological knowledge can be, uncovering personal opinions and responsibilities that result in the hybridization of knowledge. Here, we demonstrate the importance of using local ecological knowledge to incorporate shared values into management but also highlight that an integrated approach, pairing local and conventional scientific knowledge, is needed urgently if we are to meet the needs of people while simultaneously conserving biodiversity.
... Coastal biogenic habitats play a key role in enhancing biodiversity (Lefcheck et al., 2019;Sievers et al., 2019) along with providing a wide range of ecosystem services such as coastal protection (Ondiviela et al., 2014), water filtration (Hendriks et al., 2010), carbon sequestration (Luisetti et al., 2013;Bertram et al., 2021), acting as nursery and feeding areas (Lefcheck et al., 2019;Terrados and Borum, 2004) and recreation (Quevedo et al., 2020). Thus, the impact of plastic pollution may indirectly affect global economies and human well-being through the disruption of such ecosystem services (Pendleton et al., 2012;Mehvar et al., 2018). ...
Our understanding of how anthropogenic stressors such as climate change and plastic pollution interact with biodiversity is being widened to include diversity below the species level, i.e., intraspecific variation. The emerging appreciation of the key ecological importance of intraspecific diversity and its potential loss in the Anthropocene, further highlights the need to assess the relative importance of intraspecific versus interspecific diversity. One such issue is whether a species responds as a homogenous whole to plastic pollution. Using manipulative field transplant experiments and laboratory-controlled hydrodynamic simulations, we assessed the relative effects of intraspecific and interspecific diversity on microplastic trapping in coastal biogenic habitats dominated by two key bioengineers, the brown intertidal macroalgae Fucus vesiculosus and F. guiryi. At the individual level, northern morphotypes of F. guiryi trapped more microplastics than southern individuals, and F. vesiculosus trapped more microplastics than F. guiryi. Canopy density varied among species, however, leading to reversed patterns of microplastic accumulation, with F. guiryi canopies accumulating more microplastics than those of F. vesiculosus, while no differences were observed between the canopies of F. guiryi morphotypes. We emphasize the importance of assessing the effects of intraspecific variation which, along with other crucial factors such as canopy density, flow velocity and polymer composition, modulates the extent of microplastic accumulation in coastal biogenic habitats. Our findings indicate that a realistic estimation of plastic accumulation in biogenic habitats requires an understanding of within- and between-species traits at both the individual and population levels.
... Mangroves have many ecological, social, and economic advantages. Mangroves provide a good ecosystem, enhance coastal accretion, cause a considerable wave damping, and decrease flow velocities regarding high tides or flooding [14]. The wave attenuation phenomenon by the porous media can be described as two events: friction and diffusion. ...
In this paper, we investigate wave attenuation caused by mangroves as a porous media.
A 1-D mathematical model is derived by modifying the shallow water equations (SWEs). Two
approaches are used to involve the existing of mangrove: friction term and diffusion term. The
model will be solved analytically using the separation of variables method and numerically using a
staggered finite volume method. From both methods, wave transmission coefficient will be obtained
and used to observe the damping effect induced by the porous media. Several comparisons are
shown to examine the accuracy and robustness of the derived numerical scheme. The results show
that the friction coefficient, diffusion coefficient and vegetation’s length have a significant effect on
the transmission coefficient. Moreover, numerical observation is extended to a 2-D SWEs, where we
conduct a numerical simulation over a real bathymetry profile. The results from the 2-D numerical
scheme will be validated using the data obtained from the field measurement which took place in
Demak, Central Java, Indonesia. The results from this research will be beneficial to determine the
characteristics of porous structures used for coastal protection.
... For preventing erosion rate, marine habitats seagrass meadows such as P. oceanica and Cymodocea nodosa, as well as coralligenous bioconstructions, play a major role. The attenuation effect of P. oceanica on the hydrodynamics is related to the wave height attenuation, wave energy decay and reduction in the sediment transport in wave-current [47][48][49]. Flow indicator (F) accounted for the extent of maintenance and improvement required to provide protection [50]. The seagrass meadows extension was used to assess the "Regulation of chemical composition of atmosphere and oceans" ES. ...
The article focuses on the integrated environmental accounting model called 'eValue', developed for protected areas and applied in the research programme coordinated by the Italian Ministry of the Environment and aimed at implementing an environmental accounting system for Italian Marine Protected Areas (MPAs). eValue adopts a cost-benefit analysis approach. Financial accounting based on costs and revenues is integrated with environmental accounting, which reflects environmental costs and environmental revenues, i.e. environmental benefits. The environ-mental costs assess the impacts related to human activities in the MPA expressed by calculating the carbon footprint and the environmental benefits of the marine ecosystem services calculated by applying monetary valuation techniques. The values thus estimated flow into the annual flow account, where the value produced (or consumed) by the MPA is estimated by difference. The eValue model was applied to the Porto Cesareo MPA (Italy). eValue showed that the annual benefit-cost ratio reaches a value of 3.4. Furthermore, the ratio of net benefit to public funding is 3.7, completely covering the amount of public transfers and thus summarizing the MPA overall value for money.
... (2020), 2020). Physically, seagrasses provide critical developmental habitat that supports multiple fisheries (Blandon & Zu Ermgassen, 2014;Unsworth, Nordlund, & Cullen-Unsworth, 2019 and references therein), as well as provide a buffer for coastal erosion (Ondiviela et al., 2014). Chemical cycling in seagrass meadows also influences climate change mitigation and adaptation (Duarte, Losada, Hendriks, Mazarrasa, & Marbà, 2013). ...
Seagrasses are experiencing fragmentation and regression globally; thus, protection and recovery of meadows are a preservation priority. However, conservation actions must consider inherent regional conditions, since certain coastal areas are not suitable for the settlement of extensive meadows. Likewise, small oceanic archipelagos are not always able to fulfil the habitat requirements of seagrass habitats but can harbour small patches that in turn provide unique research opportunities. In this study, we focused on the seagrass Cymodocea nodosa in the archipelago of Madeira (NE Atlantic Ocean). Here we compile historical and contemporary records of this species along with characterization of associated communities (fish and invertebrates). A bionomic map with potentially suitable areas for the establishment and settlement of this species is also included. Lastly, we highlight coastal management and restoration actions and future research directions to preserve this species in Madeira Island.
... NbS leverage the hazard mitigation properties of natural ecosystems. In coastal environments, ecosystems such as dunes, seagrass meadows, saltmarshes and biogenic reefs (e.g., oyster reefs) are able to protect coastal areas from erosion and flooding by dissipating the hydrodynamic energy through their submerged canopies or structural complexity (Gedan et al., 2011;Temmerman et al., 2013;Hanley et al., 2014;Ondiviela et al., 2014). Unlike "hard" engineering structures, coastal vegetated ecosystems and biogenic reefs can self-adapt to sea level rise through different mechanisms. ...
Momentum for sustainable and climate resilience solutions for coastal protection are growing globally given the pressing need to prevent further loss of biodiversity and ecosystems while meeting the climate change adaptation and mitigation goals. Nature-Based Solutions (NbS) represent an opportunity to align environmental and resilience goals, at a time of strained budgets in a global context and when short-term needs may run counter to long-term goals. In Europe, NbS fit the mandates of major EU environmental and climate change policies by restoring biodiversity and enhancing climate-resilience and carbon sequestration. Previous studies have compiled scientific evidence about hydro-meteorological hazards for the use of NbS. However, their implementation at scale is still lacking. As the knowledge and experience with NbS for adaptation to natural hazards and climate change increases, it becomes more important to draw lessons learned and insights for replicating and scaling up NbS, especially in coastal areas where their implementation is still limited compared to other environments. This study analyzed NbS case studies across European coastal and estuarine areas to draw key lessons, understand better the current status of implementation, and identify key challenges and gaps. From a total of 59 NbS case studies associated with flooding, erosion and biodiversity loss, results show an increase in NbS implementation since 1990s, but most rapidly between 2005 and 2015. Most of the case studies are hybrid solutions employing wetlands, predominantly located in the United Kingdom (UK) and the Netherlands. Funding of NbS is largely from public sources, and rarely come from a single or a private source. Three-quarters of the case studies reported monitoring activities, but more than half did not disclose quantitative results related to effectiveness against flooding and/or erosion. The need to improve coastal defenses was indicated as the main motivation for NbS implementation over traditional structures, while sustainability was the most mentioned additional reason. Although a variety of co-benefits and lessons learned was identified, clearer descriptions and enhanced details of such information are required. There is a need for tools and strategies to expand knowledge sharing of lessons learned to enable further replication of successful cases in other areas.
... Posidonia oceanica (L.) Delile, 1813 is an endemic seagrass of the Mediterranean Sea, where it plays key ecological roles and provides multiple ecosystem services (Vizzini, 2009;Campagne et al., 2014;Ondiviela et al., 2014). A large volume of seagrass biomass is seasonally detached from living plants by autumn and winter storms and reaches the coast where it may accumulate forming accumulations that vary from ephemeral and scattered small piles to much more compact structures up to several metres high (Goḿez-Pujol et al., 2013;Boudouresque et al., 2016) that are known as banquette (Boudouresque and Meinesz, 1982;de Grissac, 1984). ...
Beach wracks are temporary accumulations of vegetal detritus that can be found along coastlines all over the world. Although beach wracks are often perceived as a nuisance for beach users, they play a crucial ecological role in carbon and nutrient connectivity across ecosystem boundaries, especially when they reach a relevant size, as in the case of the wedge-shaped seagrass accumulations called banquette. In this study, three-dimensional mapping of a giant Posidonia oceanica banquette was carried out for the first time using high-resolution UAV photogrammetry combined with field sampling and compositional and chemical analysis. The combined approach allowed a reliable estimation of the amount and spatial distribution of both vegetal biomass and sedimentary mass, as well as of total carbon, nitrogen and phosphorus content, revealing that i) banquette act as a sediment trap and represent hot spots of seagrass biomass and carbon accumulation; ii) banquette thickness, rather than the distance from the sea, influences the spatial distribution of all variables. Moreover, high-resolution digital elevation models (DEM) revealed discontinuous patterns in detritus accumulation resulting in an unknown banquette type here termed “Multiple Mega-Ridge banquette” (MMR banquette). On the one hand, this study highlighted the high potential of the UAV approach in very accurately 3D mapping and monitoring of these structures, with relevant implications for ecosystem service estimation and coastal zone management. On the other hand, it opened new questions about the role played by temporary beach wracks and, in particular, by P. oceanica banquette in the blue carbon exchange across land-ocean boundaries.
... La protección que ofrecen los humedales costeros ante oleajes extremos, aumento de nivel del mar por efectos meteorológicos, o erosión costera es uno de los servicios ecosistémicos que se estudia a nivel mundial desde el punto de vista analítico-numérico [3], [5]- [7], mediante ensayos de laboratorio [8]- [10] y campañas de campo [11]- [14]. No obstante, en Costa Rica, a pesar de ser un país con aproximadamente 1 500 km de costa y gran cantidad de población ubicada en ella, la investigación relacionada a protección costera es relativamente poca. ...
Costa Rica cuenta con aproximadamente 1 500 km de costa, en los cuales se localizan humedales que ofrecen una gran variedad de servicios ecosistémicos, entre ellos la protección costera. La cuantificación de este servicio requiere investigación en estos humedales, siendo necesario tener un inventario que ofrezca tanto su localización como sus características físicas y las de su entorno. Este tipo de inventario no existe específicamente para los humedales costeros del país, por lo que el objetivo de este trabajo es generar la primera versión de un inventario de humedales que ofrecen protección costera en Costa Rica. Se tomó como base el Inventario Nacional de Humedales (INH) y una cartografía de manglares del año 2005. Los humedales costeros no incluidos en esas fuentes fueron identificados con un procedimiento semiautomático, analizando índices de vegetación derivados de imágenes del satélite Sentinel 2 y una delimitación manual basada en ortofotos del año 2017. El nuevo inventario consiste de 464 humedales costeros, de los cuales 180 son zonas nuevas no incluidas en el INH. A estas se les incluyó la información contenida en el INH, de forma que ambas fuentes de información sean compatibles. Unido a esto se caracterizaron, en los 464 humedales, algunas condiciones naturales y antrópicas que podrían afectar posibles investigaciones relacionadas a la protección costera. El resultado es una base de datos geográfica, accesible a todo público, con la localización y caracterización general de los humedales, que podría usarse en investigaciones tanto de protección costera como del ámbito costero en general.
... Seagrasses are the unique group of flowering plants adapted to exist fully submerged in the sea and provide high-value ecosystem services, including water quality improvement, sediment accumulation and stabilization, carbon storage and sequestration, enhanced biodiversity, important nursery grounds and feeding areas, and fisheries production (Costanza et al., 1997;Kaldy, 2006;Orth et al., 2006a;Polte and Asmus, 2006;Short et al., 2007;Fourqurean et al., 2012;Ondiviela et al., 2014;Lamb et al., 2017;Thorhaug et al., 2017;Nordlund et al., 2018;Zhang et al., 2020). However, they have been disappearing rapidly worldwide because of natural and anthropogenic influences, with an estimated annual decline rate of 7% globally since 1990 (Waycott et al., 2009;Balestri et al., 2016;Pereda-Briones et al., 2018;Li et al., 2021). ...
This study firstly quantified the responses of seeds of Zostera marina to different planting times (22 September, 5 October, 23 October, 7 November and 20 November in 2015) through a field seed-planting experiment over a two year period. The suitable seed planting time required by the seeds of Z. marina was evaluated. The seedling establishment rate of Z. marina subjected to different planting times ranged from 7% to 55%, with the higher values attained on the treatments of 22 September and 5 October. New plant patches from seed were fully developed and well maintained on the planting time of 22 September, 5 October and 23 October after 2 years following planting. The shoot density under the three treatments ranged from 62 shoots per replicate to 72 shoots per replicate with an average of 67 shoots per replicate in September 2017. According to the propagation assessment and growth analysis, we found that the planting time from mid-September to mid-October may be the optimal time to plant seeds of Z. marina in our experimental site. Our results demonstrate that seed planting time has an important effect on the effectiveness of eelgrass restoration and provide data that could prove helpful in the development of successful eelgrass restoration.
... Most seagrasses are found in subtidal zones and only some species, in the genera Zostera, Phyllospadix and Halophila, can survive in intertidal zones (Hemminga & Duarte, 2000). They play an important role in supporting fisheries production, coastal protection, sediment stabilization and climate change mitigation (Ondiviela et al., 2014;Orth et al., 2006;Unsworth et al., 2019). Seagrass has a total CO 2 net primary production of 102 ± 30 Tg C/year, of which 25.8 ± 6.0 Tg C is sequestered (Table 1). ...
The atmosphere concentration of CO2 is steadily increasing and causing climate change. To achieve the Paris 1.5 or 2 oC target, negative emissions technologies must be deployed in addition to reducing carbon emissions. The ocean is a large carbon sink but the potential of marine primary producers to contribute to carbon neutrality remains unclear. Here we review the alterations to carbon capture and sequestration of marine primary producers (including traditional ‘blue carbon’ plants, microalgae, and macroalgae) in the Anthropocene, and, for the first time, assess and compare the potential of various marine primary producers to carbon neutrality and climate change mitigation via biogeoengineering approaches. The contributions of marine primary producers to carbon sequestration have been decreasing in the Anthropocene due to the decrease in biomass driven by direct anthropogenic activities and climate change. The potential of blue carbon plants (mangroves, saltmarshes, and seagrasses) is limited by the available areas for their revegetation. Microalgae appear to have a large potential due to their ubiquity but how to enhance their carbon sequestration efficiency is very complex and uncertain. On the other hand, macroalgae can play an essential role in mitigating climate change through extensive offshore cultivation due to higher carbon sequestration capacity and substantial available areas. This approach seems both technically and economically feasible due to the development of offshore aquaculture and a well‐established market for macroalgal products. Synthesis and applications. This paper provides new insights and suggests promising directions for utilizing marine primary producers to achieve the Paris temperature target. We propose that macroalgae cultivation can play an essential role in attaining carbon neutrality and climate change mitigation, although its ecological impacts need to be assessed further.
... Estuaries are recognised as regions that house some of the most productive ecosystems, sustaining a high biodiversity and complex trophic webs (McLusky and Elliott, 2004;De La Lanza Espino and Verdugo, 1998), providing habitats for many commercially important organisms (Nagelkerken et al., 2008;Cattrijsse and Hampel, 2006), stabilizing coastal sediments (Christianen et al., 2013;Friedrichs and Perry, 2001), protecting coastal regions against bad weather (Möller et al., 2014;Ondiviela et al., 2014), as well as storing large quantities of carbon ("Blue Carbon"), mainly in its sediments (Macreadie et al., 2017;Alongi, 2014). By capturing and preserving/burying significant quantities of carbon for extended periods of time, estuarine ecosystems play an important role in climate regulation, helping offset anthropogenic emissions of CO 2 and mitigating global warming (Rosentreter et al., 2018;Murdiyarso et al., 2015). ...
Plastic bags are among the most discarded waste items as they are generally only used once and are often improperly eliminated and transported by rivers and estuaries to the ocean. We developed an experimental design to mimic the effect of plastic bag deposition in a tropical estuary and investigated its short-term impact on benthic community structure. We observed a significant influence of the presence of plastic bags on the abundance, richness and diversity of benthic fauna after an eight-week exposure period. Plastic bags acted as a barrier and interfered in processes that occur at the water-sediment interface, such as organic matter and silt-clay deposition. Our results indicate that plastic bags, in addition to directly affecting benthic fauna, may alter processes such as carbon burying, known as “blue carbon”, thus making its storage in the sediment more difficult.
Seagrass canopies are important components of the world’s coastal environments providing critical ecological services. Nearshore hydrodynamics, i.e., waves and currents, are essential in controlling the ecological processes across coastal environments. Seagrass meadows can impose more complex hydrodynamics processes by attenuating sea-swell waves and decreasing the impact of nearshore mean water level rise due to wave setup and Infragravity (IG) waves. Consequently, the seagrasses dissipate waves and reduce flows allowing sediments to settle and accrete the shorelines. However, despite their significant roles, knowledge of hydrodynamics in the Indonesian seagrass ecosystems is relatively limited compared to other coastal ecosystems such as sandy beaches, mangroves, and coral reefs. This review highlights the dynamics of waves and currents, and their interaction with sediment transport and ecological processes, including biogeochemical and dispersal processes on the seagrass ecosystem contributing to the existing seagrass research in Indonesia. The associated literature is collected from scientific databases such as Scopus and Google Scholar that range between 1965 and 2021. The result showed that most of the research on hydrodynamic in seagrass ecosystems was carried out in temperate zones. Until recently, there have been limited publications discussing the interaction between the Indonesian (tropical) seagrass ecosystem and hydrodynamics parameters, even though the region has abundant seagrass species. Moreover, Indonesia is strongly influenced by various atmospheric-oceanic forcing, including the Asian monsoon affecting the dynamic of the coastal area with seagrass ecosystems. At a canopy scale, the correlation between the nearshore (tropical) hydrodynamics and ecological processes in the system is yet to be explored. Considering the potential benefit of seagrasses to coastal ecosystems, developing future research in hydrodynamics across the ecosystem is critical to overcoming the knowledge gaps in Indonesia. The knowledge gained could support the Indonesian seagrass ecosystem services and their resilience to potential hazards and climate change.
The article covers field experiments carried out to demonstrate the time needed for the seagrass to recover after disturbance (imitation of anthropogenic impact). Centered on showing the evolution (increase) of seagrass shoot density after a quantified period (time series over a year) where the pressure to seagrass is halted. Our results indicated that once such anthropogenic impacts are halted, Zostera capensis restore itself after 12 months of impact exclusion. Halting of pressure would resemble a total ban or reduction of anthropogenic impact of digging and revolving of seagrass; action carried out by communities, aiming to collect clams and other shellfish. This data covers also variation in sediments and epiphytes.
Additional data is provided on the seagrass restoration methodology that was added to the above-mentioned experiment. The IUCN Red listed Vulnerable seagrass species, Zostera capensis was tested using the plug method (a sediment-based methodology). Two size plugs, made of PVC tube, were tested: 4.5 cm and 7.5 cm diameter size, over a 12-month period (measurements carried out on four occasions). The 7.5 PVC tube experiment revealed a higher survival rate and is therefore a more suitable method for future Z. capensis restoration in impacted areas. The results from this study will further guide the appropriate management to build the best practice in seagrasses meadows restoration and awareness. It is clear from this study that a combination of both impact exclusions and active restoration is bound for best results of seagrass management actions.
Vegetated coastal ecosystems such as saltmarshes, mangroves and seagrass beds are increasingly promoted as sustainable storm and flood defense solutions by reducing wave energy. Yet, there is still intense debate on the ability of root mats to mitigate erosion, with some studies arguing that the direct contribution of roots in preventing sediment erosion is minor, while others consider them of major importance. Here, we hypothesize that the contrasting findings on the role of seagrass root mats in preventing erosion may stem from differences in sediment type. To test this idea, we investigate how root mats of seagrass, that thrive in both sandy and muddy sediments, mitigate wave-induced cliff erosion using seagrass in manipulative flume experiments. Results demonstrate that roots are very effective in reducing cliff erosion rates in sandy sediments. Cliff erosion rates were reduced up to 70% in sandy sediment with high seagrass root biomass. In contrast, cliff erosion rates in cohesive muddy sediments were low and unaffected by seagrass roots. This highlights the important role of seagrass roots in erosion mitigation, which has been overlooked compared to the role of canopies which has received more attention. We suggest that management strategies should be developed to enhance the stabilization of sandy sediment, such as i) using species with high belowground biomass, ii) use pioneer fast growing species and iii) applying temporary stabilising measures.
This report reviews large protective coastal infrastructure in intertidal and nearshore zones, including trained river entrances, armoured harbours, and groynes. This review finds support for a sustainable, more holistic concept of coastal management, where
interdisciplinary groups (e.g. asset owners, engineers, scientists, stakeholders, and community groups) work together to ensure that coastal areas are safe for communities, without compromising social, cultural and environmental values. Case studies from New South Wales within Australia and around the world give examples of where coastal protection infrastructure has either been modified with ecological engineering techniques or adopted approaches to facilitate multiple uses and add social, cultural and economic value to maximise sustainable outcomes.
The surrounding waters of Tulehu Village are coastal areas with ecosystems such as seagrass, adjacent to marine natural resources (mangroves, macroalgae, fish, mollusks, etc.). Seagrass in the coastal waters of Tulehu has spread widely, but information about seagrass communities in these waters is limited. This research was conducted to describe the species composition, density, frequency of occurrence, percentage of coverage, importance value, biomass, and distribution of pattern of seagrass in the area. The method used is the quadratic linear transect method. The results of the study showed that there are four seagrass species Cymodocea rotundata, Halodule pinifolia, Halophila ovalis, and Thalassia hemprichii. The highest values of density, frequency of occurrence, percentage of coverage, importance value, and biomass were found for H. pinifolia. The lowest values for density, percentage of coverage, and biomass were found for H. ovalis, while T. hemprichii had the lowest values for frequency of occurrence and importance. Spatial distribution based on density, percentage of coverage and biomass have the values of >10 stands m-2 , >40% and >200 g m-2 , respectively.
Horticultural and ornamental plants have been utilized by mankind for various purposes, have become commercially important, and contribute to a country’s economy. To cater to the increasing demands, these plants are propagated by different ex vitro and in vitro methods. Stem cutting-based propagation by the development of adventitious roots is one of the most common methods of propagation for these plants. Adventitious root formation refers to the development of roots from aerial sections of the plant. Prominent crops like carnation, rose, chrysanths, apple, grapes, berries, etc. are propagated through these types of roots. This approach has the advantages of being simple, quick, and provides clones of the mother plant. Adventitious root production is controlled by a number of endogenous and exogenous elements, including the genotype of the plant, hormone levels, water and nutrition availability, seasonal fluctuations, temperature, light, rooting media, making it a complicated process. To enable large-scale proliferation of important plant species, the mechanism of adventitious root production and the cumulative influence of different conditions must be understood. This chapter collated necessary information on adventitious root formation in ornamentally and horticulturally important plant species, which can be implemented to improve plant propagation through cuttings.
Nature-Based Solutions (NbS), a concept introduced in the late 2000s, has developed rapidly during the last years and is now frequently appearing in a broad spectrum of policies developed within the European Union. Its role in marine policies and research programmes is however still limited, but is likely to increase as NbS are adopted as key terminology in both biodiversity strategies and the EU taxonomy for sustainable financing. This will enhance the need for scientific advisory institutions to provide evidence-based advice on potential impacts of various combinations of marine NbS. To facilitate a critical debate about the prospects and pitfalls related to the operationalisation of marine NbS in an EU context, this paper provides an analysis of core definitions, potential categories of marine NBS and a suite of case studies. Coastal waters, shelf and open oceans present multiple options for testing new and scaling up known NbS, which could support both environmental restoration simultaneously with addressing multiple societal challenges, paving the way for a new level of ecosystem-based management. However, as the acceptance of NbS types will depend on ecosystem state and thus history, it will be a significant task to consistently communicate why some solutions may count as a NbS in some areas, while not in others. To conclude, the paper therefore raises a set of research priorities and policy advice aimed at ensuring the successful advice and deployment of marine NBS in support of multiple societal goals.
The shoreline is often at the interface of a combination of physical, ecological, and socio-economic forcing agents. Monitoring the shoreline changes across time is crucial to understand the causes of its evolution and put in place management measures. The analysis of aerial photographs from 1950 to 2016 at Mayotte Island (Indian Ocean) showed that the shoreline urbanisation is still low (6%) compared to the worldwide trend. However, a faster increase happened recently (from 3% in 1989 to 6% in 2016) owing to a strong demographic growth and socio-economic development. A multidisciplinary index was developed to assess the vulnerability of four study sites – Bandrélé, M’tsamboro, N’gouja, and Sakouli – (representative sites of beaches with fringing reefs throughout Mayotte with varying levels of urbanisation). The vulnerability of Bandrélé was lower than that of the other sites due to the presence of a mangrove at the back of the beach which plays a key role of buffer between the land and sea. M’tsamboro was the site with the highest anthropogenic pressure and highest vulnerability. Overall, as most of the shoreline is still natural at Mayotte, a sound management advice would be to put in place conservation measures to preserve natural coastal habitats, such as beaches, mangroves, seagrass beds, and coral reefs. The multidisciplinary vulnerability index developed in this study can be a useful tool to help coastal managers in the decision-making and prioritisation of actions to undertake on the shore.
The seabed in coastal regions is often covered by a dense submerged canopy formed by benthic organisms. The in-canopy flow is of great interest to coastal researchers. In this study, a semi-analytical model is proposed for the in-canopy current profile under the influence of coexisting waves. The current is driven by a mean shear stress at the canopy top and a mean streamwise pressure gradient. Wave–current interaction arises from the mean canopy drag, which is described by the conventional quadratic law. An algebraic eddy viscosity model, which accounts for the turbulence generated by a canopy-scale vortex and stem-scale wake, is proposed. The model is calibrated against unidirectional flume experiments, and is subsequently validated against a wave–current flume experiment. It is found that the mean canopy drag experienced by the current can be significantly amplified by a co-existing wave-driven oscillatory flow. Under the same current driving force, the current in wave–current flow is reduced from that in a pure-current flow. The reduction increases with canopy density and wave strength. For a wave and current at an angle, veering of the current velocity vector is suggested by the model, which makes the mean canopy drag align with the driving force of the current.
Seagrass meadows support complex species assemblages and provide ecosystem services with a multitude of socio-economic benefits. However, they are sensitive to anthropogenic pressures such as coastal development, agricultural run-off, and overfishing. The increasing prevalence of marine heatwaves (MHWs) due to climate change poses an additional and growing threat. In this study, we apply the environmental sensitivity mapping approach MESA (Mapping Environmentally Sensitive Assets) to explore the potential consequences of MHWs on the ecosystem services that Posidonia oceanica provides to coastal communities. Under the intermediate climate change scenario Representative Concentration Pathway 4.5, Mediterranean marine heatwaves will be severe by 2050, and will very likely increase mortality of P. oceanica. However, the societal risk of seagrass loss is not evenly distributed across the Mediterranean. The spatial distribution of socio-economic implications of seagrass loss is highlighted through two case studies on seagrass-dependent fisheries and coastal hazards. Coastal communities in Tunisia and Libya show very high sensitivity to a loss of fisheries due to a combination of increasingly intense and frequent MHWs, coupled with high proportions of regional seagrass-dependent fisheries catch. The coastlines of Italy, Tunisia, and Cyprus are shown to potentially be highly sensitive to loss of seagrass due to high levels of coastal hazards, and seagrass meadows susceptible to MHW-induced degradation. These coastlines are likely to suffer from reduced coastal protection services provided by intact seagrass meadows. We demonstrate the implications of MHWs for ecosystem service provision to coastal communities in the Mediterranean and the need for policy instruments to help mitigate and adapt to its effect. We also highlight the potential for environmental sensitivity mapping to help support policymakers with rapid screening tools to prioritize resources more effectively to areas where in-depth local planning is needed.
Ocean Acidification (OA), due to rising atmospheric CO2, can affect the seagrass holobiont by changing the plant's ecophysiology and the composition and functioning of its epiphytic community. However, our knowledge of the role of epiphytes in the productivity of the seagrass holobiont in response to environmental changes is still very limited. CO2 vents off Ischia Island (Italy) naturally reduce seawater pH, allowing to investigate the adaptation of the seagrass Posidonia oceanica L. (Delile) to OA. Here, we analyzed the percent cover of different epiphytic groups and the epiphytic biomass of P. oceanica leaves, collected inside (pH 6.9–7.9) and outside (pH 8.1–8.2) the CO2 vents. We estimated the contribution of epiphytes to net primary production (NPP) and respiration (R) of leaf sections collected from the vent and ambient pH sites in laboratory incubations. Additionally, we quantified net community production (NCP) and community respiration (CR) of seagrass communities in situ at vent and ambient pH sites using benthic chambers. Leaves at ambient pH sites had a 25% higher total epiphytic cover with encrusting red algae (32%) dominating the community, while leaves at vent pH sites were dominated by hydrozoans (21%). Leaf sections with and without epiphytes from the vent pH site produced and respired significantly more oxygen than leaf sections from the ambient pH site, showing an average increase of 47 ± 21% (mean ± SE) in NPP and 50 ± 4% in R, respectively. Epiphytes contributed little to the increase in R; however, their contribution to NPP was important (56 ± 6% of the total flux). The increase in productivity of seagrass leaves adapted to OA was only marginally reflected by the results from the in situ benthic chambers, underlining the complexity of the seagrass community response to naturally occurring OA conditions.
The increasing rate of global climate change seen in this century, and predicted to accelerate into the next, will significantly impact the Earth's oceans. In this review, we examine previously published seagrass research through a lens of global climate change in order to consider the potential effects on the world's seagrasses. A primary effect of increased global temperature on seagrasses will be the alteration of growth rates and other physiological functions of the plants themselves. The distribution of seagrasses will shift as a result of increased temperature stress and changes in the patterns of sexual reproduction. Indirect temperature effects may include plant community changes as a result of increased eutrophication and changes in the frequency and intensity of extreme weather events. The direct effects of sea level rise on the coastal oceans will be to increase water depths, change tidal variation (both mean tide level and tidal prism), alter water movement, and increase seawater intrusion into estuaries and rivers. A major impact of all these changes on seagrasses and tidal freshwater plants will be a redistribution of existing habitats. The intrusion of ocean water into formerly fresh or brackish water areas will directly affect estuarine plant distribution by changing conditions at specific locations, causing some plants to relocate in order to stay within their tolerance zones and allowing others to expand their distribution inland. Distribution changes will result from the effects of salinity change on seed germination, propagule formation, photosynthesis, growth and biomass. Also, some plant communities may decline or be eliminated as a result of increased disease activity under more highly saline conditions. Increased water depth, which reduces the amount of light reaching existing seagrass beds, will directly reduce plant productivity where plants are light limited. Likewise, increases in water motion and tidal circulation will decrease the amount of light reaching the plants by increasing turbidity or by stimulating the growth of epiphytes. Increasing atmospheric carbon dioxide will directly elevate the amount of CO2 in coastal waters. In areas where seagrasses are carbon limited, this may increase primary production, although whether this increase will be sustained with long-term CO2 enrichment is uncertain. The impact of increases in CO2 will vary with species and environmental circumstances, but will likely include species distribution by altering the competition between seagrass species as well as between seagrass and algal populations. The reaction of seagrasses to UV-B radiation may range from inhibition of photosynthetic activity, as seen for terrestrial plants and marine algae, to the increased metabolic cost of producing UV-B blocking compounds within plant tissue. The effects of UV-B radiation will likely be greatest in the tropics and in southern oceans. There is every reason to believe that, as with the predicted terrestrial effects of global climate change, impacts to seagrasses will be great. The changes that will occur in seagrass communities are difficult to predict; our assessment clearly points out the need for research directed toward the impact of global climate change on seagrasses.
Marine vegetated habitats (seagrasses, salt-marshes, macroalgae and
mangroves) occupy 0.2% of the ocean surface, but contribute 50% of
carbon burial in marine sediments. Their canopies dissipate wave energy
and high burial rates raise the seafloor, buffering the impacts of
rising sea level and wave action that are associated with climate
change. The loss of a third of the global cover of these ecosystems
involves a loss of CO2 sinks and the emission of 1 Pg
CO2 annually. The conservation, restoration and use of
vegetated coastal habitats in eco-engineering solutions for coastal
protection provide a promising strategy, delivering significant capacity
for climate change mitigation and adaption.
Ecosystem engineers are organisms that directly or indirectly modulate the availability of resources to other species, by causing physical state changes in biotic or abiotic materials. In so doing they modify, maintain and create habitats. Autogenic engineers (e.g. corals, or trees) change the environment via their own physical structures (i.e. their living and dead tissues). Allogenic engineers (e.g. woodpeckers, beavers) change the environment by transforming living or non-living materials from one physical state to another, via mechanical or other means. The direct provision of resources to other species, in the form of living or dead tissues is not engineering. Organisms act as engineers when they modulate the supply of a resource or resources other than themselves. We recognise and define five types of engineering and provide examples. Humans are allogenic engineers par excellence, and also mimic the behaviour of autogenic engineers, for example by constructing glasshouses. We explore related concepts including the notions of extended phenotypes and keystone species. Some (but not all) products of ecosystem engineering are extended phenotypes. Many (perhaps most) impacts of keystone species include not only trophic effects, but also engineers and engineering. Engineers differ in their impacts. The biggest effects are attributable to species with large per capita impacts, living at high densities, over large areas for a long time, giving rise to structures that persist for millennia and that modulate many resource flows (e.g. mima mounds created by fossorial rodents). The ephemeral nests constructed by small, passerine birds lie at the opposite end of this continuum. We provide a tentative research agenda for an exploration of the phenomenon of organisms as ecosystem engineers, and suggest that all habitats on earth support, and are influenced by, ecosystem engineers.
Aquatic vegetation controls the mean and turbulent flow structure in channels and coastal regions and thus impacts the fate and transport of sediment and contaminants. Experiments in an open-channel flume with model vegetation were used to better understand how vegetation impacts flow. In particular, this study describes the transition between submerged and emergent regimes based on three aspects of canopy flow: mean momentum, turbulence, and exchange dynamics. The observations suggest that flow within an aquatic canopy may be divided into two regions. In the upper canopy, called the ``vertical exchange zone'', vertical turbulent exchange with the overlying water is dynamically significant to the momentum balance and turbulence; and turbulence produced by mean shear at the top of the canopy is important. The lower canopy is called the ``longitudinal exchange zone'' because it communicates with surrounding water predominantly through longitudinal advection. In this region turbulence is generated locally by the canopy elements, and the momentum budget is a simple balance of vegetative drag and pressure gradient. In emergent canopies, only a longitudinal exchange zone is present. When the canopy becomes submerged, a vertical exchange zone appears at the top of the canopy and deepens into the canopy as the depth of submergence increases.
The spatial and temporal variability of the extreme significant wave height (SWH) in the ocean is presented. The study has been performed using a highly reliable dataset from several satellite altimeter missions, which provide a good worldwide coverage for the period 1992 onwards. A nonstationary extreme value analysis, which models seasonality and interannual variations, has been applied to characterize the extreme SWH. The interannual variability is explained through variations in the atmosphere and ocean systems, represented by different climate indices, allowing a quantitative contribution of the climate]related patterns. Results demonstrate the strong relationship between the interannual variability of extreme SWH and different ocean and atmosphere variations. A contribution of the AO and NAO indices in the North Atlantic ocean (e.g., every positive unit of the AO explains up to 70 cm of extreme wave height south of Iceland), the NINO3 in the Pacific (every negative unit of NINO3 explains up to 60 cm of extreme wave height in the Drake Passage), the SAM in the Southern ocean and the DMI in the Indian ocean reveal these climate patterns as the most relevant in the interannual extreme wave climate.
A quasi-global sea level data set from tide gauges has been used to investigate extreme sea level events and their spatial and temporal variabilities. Modern methods based on a nonstationary extreme value analysis have been applied to the maxima of the total elevations and surges for the period of 1970 and onward. A subset of the data was used to study changes over the 20th century. The analyses demonstrate the magnitude and timing of the seasonal cycle of extreme sea level occurrence, the magnitude of long-term trends in extreme sea levels, the evidence for perigean and nodal astronomical tidal components in the extremes, and the relationship of the interannual variability in high water levels to other ocean and atmosphere variations as represented by climate indices. The subtraction from the extreme sea levels of the corresponding annual median sea level results in a reduction in the magnitude of trends at most stations, leading to the conclusion that much of the change in the extremes is due to change in the mean values.
The main objectives of this flume study were to (1) quantify density dependent effects of the short-leaf seagrass Zostera nolti on hydrodynamics and sediment resuspension from a sandy bed, and (2) measure the erodability of 2 contrasting sediments (sandy and muddy) and the extent to which this is modified by the presence of 2 seagrass species, Z. noltii (sandy) and Z. marina (muddy). Field measurements of near-bed tidal currents, turbulence and suspended particulate matter at 2 different Z. noltii locations (low energy [sheltered] and higher energy [exposed] environments) were interpreted in the context of the flume results. Skimming flow above the high density bed of Z. noltii was accompanied by a 40 % reduction in near-bed flow, but this was offset by a 2-fold increase in turbulent kinetic energy (TKE) and bed shear stress (tau(0)). Despite this increase in tau(0) there was an increase in sediment stabilisation with increasing seagrass density (10-fold increase in critical bed shear stress for erosion [tau(e)] from 0.1 [bare sediment] to 1.0 Pa at the highest shoot density). This was largely explained by the increased microphytobenthos abundance (reflected in the higher chlorophyll a and carbohydrate contents) and a lower density of the grazer and bio-destabiliser Hydrobia ulvae. In contrast, the muddy site was more easily eroded (10-fold higher), with Z marina having little effect on sediment erodability (bare: tau(e) = 0.05 Pa; Z. marina: tau(e) = 0.07 Pa). This higher erodability was due to differences in hydrodynamics and the physical/biological properties of the sediment.
A site-selection model for eelgrass Zostera marina L. ecosystem restoration was developed in the northeastern US to select optimal areas for transplanting eelgrass. The site-selection model synthesizes available historic and literature-based information, reference data, and simple field measurements to identify and prioritize locations for large-scale eelgrass transplantation. Model development was based on the physical and biological characteristics associated with the most successful transplant sites in a mitigation project for the New Hampshire Port Authority. The site-selection process is divided into 3 phases: (1) the first phase uses available environmental information to formulate a preliminary transplant suitability index (PTSI) for pre-screening and eliminating unsuitable sites; (2) the second phase involves field measurements of light availability and bioturbation as well as survival and growth of test transplants at priority sites identified by the PTSI; (3) a transplant suitability index (TSI) score is calculated for each site based on the PTSI and the results of field assessments. The TSI is a multiplicative index that eliminates sites which receive ratings of zero and gives high scores to those sites with the greatest potential for successful transplantation. We applied the TSI post hoc to the New Hampshire Port Project's eelgrass transplant sites, and subsequently the site-selection model was used in an eelgrass restoration project in New Bedford Harbor, Massachusetts. After 2 yr of transplanting, the New Bedford Harbor effort has resulted in success at 62% of the sites planted using the site-selection model.
Fine-scale spatial effects of a seagrass meadow on suspended particle transport were assessed from current speeds, orbital wave velocities, turbulent Reynolds stress, in situ particle concentrations, and sedimentation rates for a horizontal grid in a coastal seagrass (Posidonia oceanica) meadow at 2 depths and during low- and high-energy periods. For the low-energy period, the vertical reduction of the total kinetic energy, from 100 cm to approximate to 10 cm above the bottom, was larger in the meadow (up to 95 %) than over the sand (35 to 75 %). Velocity maps suggest that a recirculating flow formed in the meadow with a higher Reynolds stress at the edge of the meadow. Near the bed, concentrations of small particles (< 10 mum diameter) were, lower inside the meadow than over barren sand, while concentrations of large particles (> 10 mum) were lower over the barren sand. For the period of stronger current and wave activity following a storm, nearbed turbulence and orbital wave velocity were elevated, though still lower inside the meadow than over the sand. For this high energy period, particle concentrations increased over the whole study area, but were still lowest deep inside the meadow. Overall, the horizontal spatial distribution of plants in the study area had a profound effect on the flow field and on vertical transport, even during the high-energy period, The reduced nearbed turbulence and lower sedimentation rate below the canopy confirms it as a calm zone with lower mixing compared to unvegetated areas.
The response of Cymodocea nodosa (Ucria) Aschers. seedlings to experimental burial and erosion was examined to test the extent of coupling between fluctuations in sediment depth and seagrass growth. Shoot survivorship declined with erosion and with increasing burial depth, relative to the controls. Seagrass growth response, described by changes in internodal and leaf sheath length, the rate of appearance of new leaves, and shoot vertical growth showed a bell-shaped response to fluctuations in sediment depth. Shoot internodal and leaf sheath length, the rate of appearance of new leaves, and vertical growth all increased with sediment depth from minimal values under erosion to maximal values at burial of <7 cm. These results demonstrate that C. nodosa seedlings tolerate burial <7 cm, and that burial stimulates the growth of surviving seedlings. Examination of this growth response for C. nodosa and other seagrass species, which allows quantification of tolerable changes in sediment depth, may provide useful information for conservation of seagrass populations.
While the ability of subaquatic vegetation to attenuate wave energy is well recognized in general, there is a paucity of data from the field to describe the rate and mechanisms of wave decay, particularly with respect to the relative motion of the vegetation. The purpose of this study was to quantify the attenuation of incident wave height through a seagrass meadow and characterize the blade movement under oscillatory flow under the low-energy conditions characteristic of fetch-limited and sheltered environments. The horizontal motion of the seagrass blades and the velocity just above the seagrass canopy were measured using a digital video camera and an acoustic Doppler velicometer (ADV) respectively in order to refine the estimates of the drag coefficient based on the relative velocity. Significant wave heights (H s) were observed to increase by ~0.02 m (~20%) through the first 5 m of the seagrass bed but subsequently decrease exponentially over the remainder of the bed. The exponential decay coefficient varied in response to the Reynolds number calculated using blade width (as the length scale) and the oscillatory velocity measured immediately above the canopy. The ability of the seagrass to attenuate wave energy decreases as incident wave heights increase and conditions become more turbulent. Estimates of the time-averaged canopy height and the calculated hydraulic roughness suggest that, as the oscillatory velocity increases, the seagrass becomes fully extended and leans in the direction of flow for a longer part of the wave cycle. The relationship between the drag coefficient and the Reynolds number further suggests that the vegetation is swaying (going with the flow) at low-energy conditions but becomes increasingly rigid as oscillatory velocities increase over the limited range of the conditions observed (200 < Re < 800). In addition to the changing behavior of the seagrass motion, the attenuation was not uniform with wave frequency, and waves at a secondary frequency of 0.38 Hz (2.6 s) appeared to be unaffected by the seagrass. Cospectral analysis between the oscillatory and blade velocity suggests that the seagrass was moving in phase with the current at the (lower) secondary frequency and out of phase at the (higher) peak frequency. In this respect, seagrass is not only an attenuator of wave energy but also serves as a low-pass filter; higher frequencies in the spectra tend to be more attenuated.
1. We report the effects of a marine plant canopy on flow in the coastal environment. In addition to reducing the magnitude of the ambient flow, a Zostera marina canopy was observed to undulate under unidirectional flow. Spectral analyses of the velocity fluctuations in the canopy revealed a fundamental frequency of approximately 0.125-0.156 Hz. 2. These fluctuations were not caused by ambient flow conditions but rather by the hydroelasticity of the plants ('monami'). 3. Flow within the canopy can be, therefore, considered a function of plant movement rather than ambient conditions. Calculations incorporating these observations and the resistance of the canopy indicate that eddy viscosity is between 10(-5) and 10(-4) m2 s-1. 4. Mixing within Z. marina canopies is reduced and more like the deep ocean than the coastal environment. This reduced level of mixing has considerable implications for the productivity and physiology of marine macrophytes.
Seagrass meadows play an important role in the trapping and binding of particles in coastal sediments. Yet seagrass may also contribute to sediment production directly, through the deposition of detritus and also the deposition of the associated mineral particles. This study aims at estimating the contribution of different seagrass species growing across an extensive range of deposition to inorganic (carbonate and non-carbonate) and organic sediment production. Total daily deposition measured with sediment traps varied from 18.8 (±2.0)gDWm−2d−1 in Silaqui (Philippines) to 681.1 (±102)gDWm−2d−1 in Bay Tien (Vietnam). These measurements correspond to a single sampling event and represent sedimentation conditions during the dry season in SE-Asia coastal areas. Enhalus acoroides was the most common species in the seagrass meadows visited and, together with Thalassia hemprichii, was present at sites from low to very high deposition. Halodule uninervis and Cymodocea species were present in sites from low to medium deposition. The mineral load in seagrass leaves increased with age, and was high in E. acoroides because it had the largest and long-lived leaves (up to 417mg calcium carbonate per leaf and 507mg non-carbonate minerals per leaf) and low in H. uninervis with short-lived leaves (4mg calcium carbonate per leaf and 2mg non-carbonate minerals per leaf). In SE-Asia seagrass meadows non-carbonate minerals accumulate at slower rates than the production of calcium carbonate by the epiphytic community, consequently the final loads supported by fully grown leaves were, as average, lower than calcium carbonate loads. Our results show that organic and inorganic production of the seagrasses in SE-Asia represents a small contribution (maximum of 15%) of the materials sedimented on a daily base by the water column during the sampling period. The contribution of the carbonate fraction can be locally significant (i.e. 34% in Silaqui) in areas where the depositional flux is low, but is minor (
A parabolic model for calculating the combined refraction/diffraction of monochromatic linear waves is developed, including a term which allows for the dissipation of wave energy. The coefficient of the dissipation term is related to a number of dissipative models. Wave calculations are performed for a localized area of dissipation, based on a friction model for a spatial distribution of rigid vertical cylinders. The region of localized dissipation creates a shadow region of low wave energy, which may have important implications for the response of neighboring shore lines.
Effects of global warming on marine ecosystems are far less understood than they are in terrestrial environments. Macrophyte-based coastal ecosystems are particularly vulnerable to global warming, because they often lack species redun- dancy. We tested whether summer heat waves have negative effects on an ecologically important eco- system engineer, the eelgrass Zostera marina L., and whether high genotypic diversity may provide re- silience in the face of climatic extremes. In a meso- cosm experiment, we manipulated genotypic diver- sity of eelgrass patches fully crossed with water temperature (control vs. temperature stress) over 5 mo. We found a strong negative effect of warming and a positive effect of genotypic diversity on shoot densities of eelgrass. These results suggest that eel- grass meadows and associated ecosystem services will be negatively affected by predicted increases in summer temperature extremes. Genotypic diver- sity may provide critical response diversity for main- taining seagrass ecosystem functioning, and for adaptation to environmental change.
One of the most frequently quoted ecosystem services of seagrass meadows is their value for coastal protection. Many studies emphasize the role of above-ground shoots in attenuating waves, enhancing sedimentation and preventing erosion. This raises the question if short-leaved, low density (grazed) seagrass meadows with most of their biomass in belowground tissues can also stabilize sediments. We examined this by combining manipulative field experiments and wave measurements along a typical tropical reef flat where green turtles intensively graze upon the seagrass canopy. We experimentally manipulated wave energy and grazing intensity along a transect perpendicular to the beach, and compared sediment bed level change between vegetated and experimentally created bare plots at three distances from the beach. Our experiments showed that i) even the short-leaved, low-biomass and heavily-grazed seagrass vegetation reduced wave-induced sediment erosion up to threefold, and ii) that erosion was a function of location along the vegetated reef flat. Where other studies stress the importance of the seagrass canopy for shoreline protection, our study on open, low-biomass and heavily grazed seagrass beds strongly suggests that belowground biomass also has a major effect on the immobilization of sediment. These results imply that, compared to shallow unvegetated nearshore reef flats, the presence of a short, low-biomass seagrass meadow maintains a higher bed level, attenuating waves before reaching the beach and hence lowering beach erosion rates. We propose that the sole use of aboveground biomass as a proxy for valuing coastal protection services should be reconsidered.
Interactions between organisms are a major determinant of the distribution and abundance of species. Ecology textbooks (e.g., Ricklefs 1984, Krebs 1985, Begon et al. 1990) summarise these important interactions as intra- and interspecific competition for abiotic and biotic resources, predation, parasitism and mutualism. Conspicuously lacking from the list of key processes in most text books is the role that many organisms play in the creation, modification and maintenance of habitats. These activities do not involve direct trophic interactions between species, but they are nevertheless important and common. The ecological literature is rich in examples of habitat modification by organisms, some of which have been extensively studied (e.g. Thayer 1979, Naiman et al. 1988).