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(a) Bar chart showing the densities of the four motility classes per treatment, in ind m −2. M1: organisms living fixed in a tube; M2: sessile, but not fixed in a tube; M3: slowly moving organisms; M4: free movement through a burrow system. (b) Bar chart showing the densities in ind m −2 of the four main functional groups, based on sediment reworking activity. S: Surficial modifiers; B: biodiffusors; UC: upward conveyors; DC: downward conveyors. Error bars represent mean ± standard error; letters above the error bars indicate pairwise significant differences. The four treatments represent the thickness of the applied sediment layer (in cm).
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Human activities, among which dredging and land use change in river basins, are altering estuarine ecosystems. These activities may result in changes in sedimentary processes, affecting biodiversity of sediment macrofauna. As macrofauna controls sediment chemistry and fluxes of energy and matter between water column and sediment, changes in the str...
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Context 1
... general, changes in macrobenthic community composi- tion mirrored differential responses of specific motility and sediment reworking traits (Fig. 2, Table 3). Densities of the two groups of organisms with lowest motility were nega- tively affected by the applied treatments while densities of more motile species were not significantly different among treatments (Fig. 2a). The density of tube-building organisms (M1) decreased gradually with the thickness of the deposited sediment, whereas densities of species with limited move- ment (M2) were impaired by all sediment deposition treat- ments, irrespective of their magnitude (Fig. ...
Context 2
... general, changes in macrobenthic community composi- tion mirrored differential responses of specific motility and sediment reworking traits (Fig. 2, Table 3). Densities of the two groups of organisms with lowest motility were nega- tively affected by the applied treatments while densities of more motile species were not significantly different among treatments (Fig. 2a). The density of tube-building organisms (M1) decreased gradually with the thickness of the deposited sediment, whereas densities of species with limited move- ment (M2) were impaired by all sediment deposition treat- ments, irrespective of their magnitude (Fig. ...
Context 3
... general, changes in macrobenthic community composi- tion mirrored differential responses of specific motility and sediment reworking traits (Fig. 2, Table 3). Densities of the two groups of organisms with lowest motility were nega- tively affected by the applied treatments while densities of more motile species were not significantly different among treatments (Fig. 2a). The density of tube-building organisms (M1) decreased gradually with the thickness of the deposited sediment, whereas densities of species with limited move- ment (M2) were impaired by all sediment deposition treat- ments, irrespective of their magnitude (Fig. ...
Context 4
... sediment reworking groups were affected by the depo- sition (Fig. 2b). For surficial modifiers, all treatments showed lower densities compared to the control, and for upward con- Table 1. The three species with highest cumulative contribution (> 50 %) to the total dissimilarity between treatments * . The first column shows the treatments being compared (e.g. T0-1: a comparison between treatments T0 and ...
Context 5
... contribution Table 3. Statistical factors from two-factor blocked ANOVA tests with "Treatment" (4 levels) and "Tank" (2 levels) as factors. M1 until M4 stand for motility classes, as defined by Solan et al. (2004) (M1: living fixed in a tube; M2: sessile, but not fixed in a tube; M3: slow movement through the sediment; M4: free movement in a burrow system). Significant pairwise differences between treatments are given in the table. All results for species and functional groups are given for densities. veyors T5 was significantly lower than all other treatments (Tables 3, 4). The density of biodiffusors was only signifi- cantly reduced in T5 compared to the control (Fig. 2b). Activity of the macrofauna (bioturbation and bio- irrigation) was significantly affected by the deposition treat- ments (Table 4). Bioturbation activity was significantly higher in T1 than in all other treatments (Tables 3, 4), and was lowest in T5. While the biodiffusion coefficient D NL b reached average values in the control treatment, it rose sig- nificantly in T1 and dropped again in T2 and T5 (Fig. 3a). A similar pattern was observed for bio-irrigation, but here we only found a significant difference between T1 and T5 (Fig. ...
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... In Svalbard fjords, the variations in water turbidity and phytoplanktonic growth, highly depending on seasonal dynamic (Piquet et al. 2014;Calleja et al. 2017) have a strong influence on benthic environments, in terms of sedimentary stability (e.g., Mestdagh et al. 2018;Guilhermic et al. 2023) and organic supply (e.g., Bourgeois et al. 2016). ...
Arctic fjords, being transitional areas between glacier‐covered land and the ocean, are characterized by strong environmental gradients. The seasonal melting of glaciers generates strong turbidity and primary production antagonist gradients, which can affect benthic habitats. Two sampling campaigns were carried out in Kongsfjorden (Svalbard, Arctic Ocean) in May and August 2021 to investigate seasonal changes in benthic foraminifera spatial distribution and ecosystem functioning along a longitudinal transect of 10 km from the Kronebreen tidewater glacier front. Concurrently, organic matter quantity and biochemical composition, sediment grain size, and physical parameters of the water masses were investigated as possible driving factors of benthic ecosystem responses. In a previous study, three statistically determined foraminiferal biozonations (glacier proximal, medial, and distal) were observed on the basis of their species content within the closest 10 km from the glacier front, presenting similar assemblages in both seasons. Our results indicate that foraminiferal distribution at the local scale is mainly driven by physical and geochemical gradients induced by melting waters and sediment discharges from the tidewater glacier occurring during summer. Due to the climate change, the melting season is expected to last longer and increasing global temperature will much probably accelerate the melting processes. Our findings strongly support the use of foraminifera as bioindicators to monitor the effects of ongoing climate change on the benthic ecosystems of Arctic fjords and, accessorily, as proxies for reconstructing glacier front positions in the recent past.
... However, the damage to surface sediment by otter boards may be local. Studies investigating the change in the vertical distribution of sediment constituents demonstrate that an effect of trawling can be the removal of surface sediment and considerable alterations to matter concentrations and processes in this sediment surface layer (Mestdagh et al., 2018;van de Velde et al., 2018;Morys et al., 2021). In an experimental dredge-trawling activity, Published by Copernicus Publications on behalf of the European Geosciences Union. ...
... Reports on the shift in functional groups towards smaller-sized and possibly opportunistic fauna caused by bottom trawling support this (Sparks-McConkey and Watling, 2001;Hiddink et al., 2019). As demonstrated by Mestdagh et al. (2018), particle reworking, possibly as a consequence of an escape reaction, and bioirrigation may mitigate the effects of trawling. ...
In the process of reworking sediments and thus shaping biogeochemical processes, marine bottom-dwelling animals are thought to play a pivotal role in many benthic environments. Bioturbation (particle reworking) includes the downward transport of particles into the sediment as a major process and is sometimes detected as subsurface maxima (peaks) of specific particulate substances (tracers). Here, we document the fact that subsurface peaks, such as those typically attributed to biological particle transport in sediments, may equally be generated by otter boards in bottom-trawling fishery. Boards can generate tracer peaks whereby they scoop sediment from the surface, flip it over, and deposit it onto the adjacent seafloor. These peaks are indistinguishable from those generated by benthic fauna burying surface material at sediment depth. We demonstrate this for the particle tracer chlorophyll a in silty sand from the western Baltic Sea with fauna that generally do not burrow deep in a global comparison. Our inability to distinguish the driving processes generating the peaks indicates limits to our understanding of the magnitude and spatial extent of bioturbation traces in this environment. It also poses a problem for the assessment of fishery resource use and benthic processes. However, based on natural fauna abundance, behavioral information, and fishery intensity data, we identify macrofauna and not otter boards as the dominant cause of peaks at the sites investigated here.
... In particular, fine-grainedsediment deposition can lead to a decline in microhabitat quality and affect benthic ecosystems in several ways (e.g. Larson and Sundbäck, 2012;Mestdagh et al., 2018;Wood, 1997): (1) by constituting a physical barrier that disrupts the connection to the water column, thereby impeding food supply and oxygen exchange; (2) by altering the substrate's geochemical composition and thus the substrate's suitability for some taxa; and (3) by providing a highly porous, watersaturated substrate whose instability can prevent recolonization from refuge areas. ...
... Among these, the ability of organisms to quickly migrate through the sediment is crucial to the recovery of their preferential habitat at the surface or inside the sediment column. Despite several studies focused on the response of mega-and macrobenthos to physical disturbances (Bolam et al., 2011;Cottrell et al., 2016;Hendrick et al., 2016;Mestdagh et al., 2018), little is known about meioand microfauna, which represent lower steps of the trophic chain and therefore have the potential to control the ecosystem functioning through a bottom-up relationship. ...
... Some interesting observations can be pointed out. Mestdagh et al. (2018), for example, simulated a sudden deposit of about 4 cm of sediment and observed a complete recovery of different species of molluscs and crustacean within 15 d after the disturbance. No decay of abundances of certain species was observed, indicating that some macrofaunal species can deal with 4 cm depth burial without problems. ...
A microcosm experiment was designed to describe how benthic foraminifera react to fine-sediment deposits varying in frequency and intensity as they may occur regularly or occasionally in coastal benthic environments, caused by discharges from (e.g.) river flooding, tidewater glacier melting in polar regions, or diverse anthropic activities linked to harbour or watershed management. The influence of seabed burial resulting from these events on the ecology of benthic ecosystems is often overlooked, and the resilience of benthic communities is poorly known. During a 51 d long experiment, a typical northeastern Atlantic intertidal foraminiferal community, mainly represented by Ammonia confertitesta and Haynesina germanica species, was subjected to two kinds of sedimentary disturbance: (1) a one-time high-volume (OHV) deposit, i.e. sediment about 3 cm thick was added at one time at the beginning of the experiment; and (2) frequent low-volume (FLV) deposits, i.e. sediment about 0.5 cm thick was added each week for 4 weeks. The geochemical environment (e.g. dissolved oxygen penetration in the sediment, salinity, temperature, and nutrient content in the supernatant water) was monitored to follow the microcosm steady state before and during the experiment. In both disturbed microcosms, H. germanica showed a significant linear decrease in abundance during the experiment, while the total abundance of foraminifera was significantly affected only by the OHV treatment, suggesting a stronger effect of a single thick deposit on standing stocks and biodiversity compared to frequent low-volume sediment supplies. Concerning the vertical migration of foraminifera after sedimentary disturbances, the two dominant species moved upwards to the water–sediment interface with migration speeds estimated to be 0.41 and 0.47 mm h-1 respectively for A. confertitesta and H. germanica. In the FLV treatment, the resilient state was already reached within 1 d following a low-thickness burial, while in the OHV, it was achieved between 1 and 7 d after the 3 cm thick deposit. These results suggest that foraminifera can migrate rapidly after a sedimentary burial to recover their preferential life position under the new sediment–water interface, but in the case of an abrupt thick burial, several days are needed to reach a resilient state.
... Given this, keeping track of the benthic ecosystem and its resilience is essential to protect the marine ecosystem and conduct appropriate environmental management (D'Alessandro et al., 2020;Festjens et al., 2023). The macroinvertebrates are described as essential bio-indicators as they respond to differential sources of stressors, perform various forms of feeding at different trophic levels, and have tube-building and bioturbation activities thereby mediating exchanges between sediment and water column (Mestdagh et al., 2018;Kim et al., 2019;Bhowmik and Mandal, 2021). Indeed, the traditional taxonomy-based approach of monitoring has been widely implemented with the focus being on the composition of communities (Llanos et al., 2020). ...
The preservation of ecosystem functioning of coastal zones, in face of increasing environmental stressors and species extinctions, relies on the functional redundancy and inherent resilience of its inhabitants. To compare the benthic functioning and resilience of a disturbed area with a relatively less impacted area, a study was conducted in Mumbai Port and Malvan Marine Protected Area (MPA), which exhibited contrasting characteristics. The hypothesis posited that the anthropogenically influenced Mumbai port would exhibit lower functional parameters and resilience compared to Malvan. Overall, the MPA presented higher species richness and functional diversity with a greater presence of sensitive species, while Mumbai was dominated by the presence of opportunistic species, as anticipated. However, our findings demonstrated that despite varied trends in species diversity metrics, in both the coastal areas, the resemblance in benthic functioning was high due to similarity in dominant trait profiles. Surprisingly, Functional Richness was higher at Mumbai, while Functional Evenness, Divergence and Dispersion were comparable at both sites. The resilience, as quantified by Functional Redundancy, was also comparable at both areas attributable to the presence of clusters of species with similar traits and a low occurrence of rare traits. The combination of traits observed in both areas was influenced by the extant environmental conditions, as revealed by RLQ analyses. This study underscores the valuable insights provided by the application of Biological Trait Analysis (BTA) tool in deciphering the relationship between species diversity and ecosystem functioning, as well as the resilience capabilities of ecosystems subjected to varying levels of perturbation. Moreover, the incorporation of functional diversity indices yielded valuable inferences regarding ecosystems resilience, which can aid future ecosystem management strategies.
... Molecular analyses of sediment cores have proven to provide pertinent information to identify variations in land cover or to study the impacts of human usages on erosion (Ficetola et al., 2018;Giguet-Covex et al., 2014;Liang et al., 2013;Shah et al., 2019;Thomsen and Willerslev, 2015;Torti et al., 2015). Indeed, analyses of environmental DNA profiles from extracted sediments were shown to reflect land uses, as revealed by changes in micro-and macrobiodiversity and putatively to changes in ecosystem processes (Capo et al., 2022;Lohrer et al., 2006;Mestdagh et al., 2018;Straat et al., 2018). For example, analyses of core samples from lakes helped to demonstrate that human agricultural practices, and in particular the usage of herbicides, have substantial impacts on sediment transfer rates from terrestrial to aquatic zones (Giguet-Covex et al., 2019;Pansu et al., 2015;Sabatier et al., 2014). ...
Land use change and anthropogenic forcing can drastically alter the rates and patterns of sediment transport and modify biodiversity and ecosystem functions in coastal transition zones, such as the coastal ecosystems. Molecular studies of sediment extracted DNAs provide information on currently living organisms within the upper layers or buried from various periods of time, but might also provide knowledge on species dynamics, replacement and turnover. In this study, we evaluated the eukaryotic communities of a marine core that present a shift in soil erosion that was linked to glyphosate usage and correlated to chlordecone resurgence since 2000. We show differences in community composition between samples from the second half of the last century and those from the last two decades. Temporal analyses of the relative abundance, alpha diversity, and beta diversity for the two periods demonstrated different temporal dynamics depending on the considered taxonomic group. In particular, Ascomycetes showed a decrease in abundance over the most recent period associated with changes in community membership but not community structure. Two photosynthetic groups, Bacillariophyceae and Prasinophytes clade VII, showed a different pattern with an increase in abundance since the beginning of the 21st century with a decrease in diversity and evenness to form more heterogeneous communities dominated by a few abundant OTUs. Altogether, our data reveal that agricultural usages such as pesticide use can have long-term and species-dependent implications for microeukaryotic coastal communities on a tropical island.
... In particular, fine-grained sediment deposition can lead to a decline in microhabitat quality and affect benthic ecosystems in several ways (e.g. (Larson and Sundbäck, 2012;Mestdagh et al., 2018;Wood, 1997) : (1) by constituting a physical barrier that disrupts connection to the water column, thereby impeding food supply and oxygen 50 exchange ; (2) by altering substrate geochemical composition and thus substrate suitability for some taxa, (3) by providing a highly porous, water-saturated substrate which instability can prevent recolonization from refuge areas. ...
A microcosm experiment was designed to describe how benthic foraminifera react to fine sediment deposits varying in frequency and intensity, as it may occur regularly or occasionally in coastal benthic environments, caused by discharges from (e.g.) river flooding, tidewater glacier melting in polar regions or diverse anthropic activities linked to harbour or watershed management. The influence of seabed burial resulting from these events on the ecology of benthic ecosystems is often overlooked, and the resilience of benthic communities is poorly known. During a 51-day long experiment, a typical northeastern Atlantic intertidal foraminiferal community, mainly represented by Ammonia confertitesta and Haynesina germanica species, was subjected to two kinds of sedimentary disturbance: 1) one-time high volume (OHV) deposit, i.e. about 3 cm thick sediment added in one time at the beginning of the experiment; and 2) frequent low volume (FLV) deposits, i.e. about 0.5 cm added each week for 4 weeks. The geochemical environment (e.g. dissolved oxygen penetration in the sediment, salinity, temperature and nutrient content in the supernatant water) was monitored to follow the microcosm steady state before and during the experiment. In both disturbed microcosms, H. germanica showed a significant linear decrease in abundance during the experiment while the total abundance of foraminifera was significantly affected only by the OHV treatment, suggesting a stronger effect of a single thick deposit on standing stocks and biodiversity compared to frequent low sediment supplies. Concerning the vertical migration of foraminifera after sedimentary disturbances, the two dominant species moved upwards to the water- sediment interface with migration speeds estimated at 0.41 and 0.47 mm/h respectively for A. confertitesta and H. germanica. In the FLV treatment, the resilient state was already reached within the day following a low thickness burial while in the OHV it was achieved between 1 and 7 days after the 3 cm thick deposit. These results suggest that foraminifera can migrate rapidly after a sedimentary burial to recover their preferential life position under the new sediment-water interface, but in case of an abrupt thick burial, several days are needed to reach a resilient state.
... The orientation of the bed influences the exposure or shelter to waves and currents (Wilson et al., 2007) which determine disturbance of the bed and also transport of (pelagic) food to the benthic fauna. The sedimentation rate over one year is presumed to influence the survival, settling, and feeding strategy of benthic species (Mestdagh et al., 2018). The terrain parameters were derived from bathymetric maps, with a 20 × 20 m grid size, collected by the Ministry of Public works and Infrastructure in the summer of 2016 and 2017. ...
As a response to climate change and sea-level rise, new nourishment strategies for low-lying sandy coasts are developed. These interventions affect the habitat quality of coastal ecosystems for benthic communities. Unraveling the relationship between benthic fauna and their environment facilitates the design of sustainable management strategies for the coastal ecosystem. At the ebb-tidal delta of Ameland, The Netherlands, a unique dataset of 166 benthic and sediment samples is collected and allowed for an investigation of the macrobenthic fauna distribution at the spatial scale of morphological features. The benthic community at the ebb tidal delta is composed of species capable of withstanding the dynamic nature of these sandy coastal ecosystems. Despite the dynamic environment, the geomorphology of the ebb-tidal delta is reflected in the benthic species distribution. Distinct species assemblages were identified, covering a gradient of physical stress from extremely exposed to waves or currents, to relatively low energetic environments such as found on the delta plane seaward of the ebb-tidal delta terminal lobe. This gradient is reflected in the median grain size, organic matter content, and oxygenation of the sediment. A second gradient distinguishes well-sorted, mainly wave-exposed sediments from less well-sorted, mainly current-exposed sites. The functional characteristics of the benthic fauna show a clear contrast between the three most exposed, and the three most sheltered assemblages. Small, short-lived, surface deposit-feeding, highly mobile, burrowing organisms dominate in the most exposed sites, whereas with increasing shelter also larger, long-lived, filter-feeding and sessile organisms become more dominant. The functional characteristics suggest that the fauna of the most exposed sites will likely show a fast recovery of disturbance by sand nourishments. A much longer-lasting effect can be expected on sheltered parts of the ebb-tidal delta.
... A more indirect consequence from the feeding activities are the effects on the immediate, surrounding environments such as through the nutrient cycling and decomposition processes (Giblin et al. 1997;Braeckman et al. 2010Braeckman et al. , 2014Mestdagh et al. 2018). Oftentimes, many of the localized conditions are determined by the small or micro-scale processes such as advective or diffusive transport of solute and particulate matter through the sediment matrix, as well as particle interactions and biogeochemical reactions Winterwerp and van Kesteren 2004;Janssen et al. 2005;Huettel et al. 2014). ...
... Nevertheless, the alteration of habitats can affect the animal densities and/or cause behavioral changes to certain functional groups, which include key players in the sedimentary biogeochemical cycling. As a consequence, the ecosystem functions can be negatively affected (Villnäs et al. 2012;Mestdagh et al. 2018). ...
... On the one hand, tube-building worms (tubicolous) and burrowing animals can increase the sediment surface area 11 significantly enough to enhance the exchange rates with the overlying water (Forster et al. 1999;Stieglitz et al. 2000;Santos et al. 2012). However, increased deposition (e.g., elevated levels of silt and organic matter), could exclude less mobile species with a limited ability to escape burial or clogging of their feeding apparatus (Lohrer et al. 2004;Mestdagh et al. 2018). This is significant as some benthic organisms can redistribute the upper layers of sediment and enable the burial of fine material, particularly as their densities become higher (e.g., steep slope and trough) (Volkenborn et al. 2007a;Santos et al. 2012). ...
... Extreme bulk density sediments may present difficult living conditions for benthic macrofauna and affect their survival due to physiological constraints. At very low bulk densities, sediments might become so soft that animals have to expend a great amount of energy to keep their position in the sediment or unclog their feeding apparatus of small mud particles (Lohrer et al., 2006;Mestdagh et al., 2018). High bulk densities would present different challenges. ...
Benthic macrofauna are a key component of intertidal ecosystems. Their mobility and behavior determine processes like nutrient cycling and the biogeomorphic development of intertidal flats. Many physical drivers of benthic macrofauna behavior, such as sediment grain size, have been well-studied. However, little is known about how sediment bulk density (a measure of sediment compaction and water content) affects this behavior. We investigated the effect of bulk density on the burrowing rate, burrowing depth, bioturbation activity, and oxygen consumption of bivalves (Limecola balthica, Scrobicularia plana, and Cerastoderma edule) and polychaetes (Hediste diversicolor and Arenicola marina) during a 29-day mesocosm experiment. We compared four sediment treatments consisting of two sediments of differing grain size classes (sandy and muddy) with two bulk densities (compact and soft). Overall, bulk density had a strong effect on benthic macrofauna behavior. Benthic macrofauna burrowed faster and bioturbation more intensely in soft sediments with low bulk density, regardless of grain size. In addition, L. balthica burrowed deeper in low bulk density sediment. Finally, we found that larger bivalves (both C. edule and S. plana) burrowed slower in compact sediment than smaller ones. This study shows that benthic macrofauna change their behavior in subtle but important ways under different sediment bulk densities which could affect animal-sediment interactions and tidal flat biogeomorphology. We conclude that lower bulk density conditions lead to more active macrofaunal movement and sediment reworking.
... On the one hand, tube-building worms (tubicolous) and burrowing animals can increase the sediment surface area significantly enough to enhance the exchange rates with the overlying water (Forster et al., 1999;Santos et al., 2012;Stieglitz et al., 2000). However, increased deposition (e.g., elevated levels of silt and organic matter) could exclude less mobile species with a limited ability to escape burial or clogging of their feeding apparatus (Lohrer et al., 2004;Mestdagh et al., 2018). This is significant as some benthic organisms can redistribute the upper layers of sediment and enable the burial of fine material, particularly as their densities become higher (e.g., steep slope and trough) (Santos et al., 2012;Volkenborn et al., 2007). ...
Sand waves are dynamic and regular bedforms that are ubiquitous in sandy shelf seas. However, information about the ecological characteristics (e.g., benthic community structure) and their spatial variability within these habitats is very limited. To address this knowledge gap, we undertook a field campaign in summer 2017 to investigate the macrofaunal community composition of a sand wave area off Texel (Dutch part of the North Sea). Sand waves in this area were asymmetrical, with longer gentle slopes that were approximately double in length to the shorter steep slopes. The benthic distribution along the different parts of these sand waves was assessed by collecting a large number of box cores within a transect line (~1 km). We show considerable variability in the individual, biomass and taxon densities, which were all significantly higher on the steeper slopes of the sand waves. These results are consistent with the trends observed in both the abiotic parameters and video analysis that were measured in two recent studies at the same study area. Our results provide valuable insight into the small‐scale patterns of variability in asymmetrical dynamic bedform environments, where gentle slopes seem to be primarily controlled by physical forces, while steep slopes are more under biotic control.
