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For conserving sandy beaches, it is important to manage beach-sediment dynamics and preserve animals living there. Sandy beach invertebrate animals are characterized by high mobility, such as surfing clams and swimming crustaceans living in the foreshore swash environment. On the other hand, there are abundant invertebrates, such as polychaete worms and ghost crabs, living in beach sediments. In this study, we utilized geological techniques to measure the distribution range of the animals living in the sediments on sandy beaches in Japan and Australia. We also measured the population density of the crab by counting burrow openings on the beach. Because the worm and crab burrows can be preserved in strata (geological records) as trace fossils, we can reconstruct the invertebrate populations using sedimentary core samples in the near-past beach ecosystems when there were no human impacts. The reconstructed beach ecosystem can be a guide for future conservation. [ABSTRACT FROM AUTHOR]

Though there is mounting evidence that climate warming is altering trophic interactions between organisms, its effects on non-trophic interactions remain relatively undocumented. In seagrass systems, the bioturbating activity of infauna influences annual seagrass patch development by influencing seed burial depth and germination success as well as sediment properties. If bioturbation is altered by warming, consequences on seagrass may result. Here, we assessed how heatwaves alter seagrass seed burial depth and germination rates when no bioturbators (control), single bioturbators and mixtures of bioturbators of contrasting feeding activities are present. The three bioturbators manipulated were surface (top 1-2 cm of sediment) biodiffusor, the brown shrimp (Crangon crangon), the shallow (top 3–8 cm) diffusor, the common cockle, (Cerastoderma edule) and the upward (5–15 cm) conveyor, the polychaete, Cappitellidae spp. We applied two temperature treatments: (1) a present-day scenario set at the average summer temperature of seagrass habitat (17ºC); and (2) a heatwave scenario modelled on the maximum recorded temperature (26.6ºC). Under present-day conditions, seed burial was greater in the presence of bioturbators than the control where no infauna was added (42–74% vs. 33 ± 7%, respectively). Cockles had the greatest impact on seed burial amongst all the bioturbators. Under the heatwave scenario, seed burial in the mixed bioturbator treatment increased to match that of the cockle treatment. Cockles and polychaetes elevated the germination rates of buried seeds under present-day temperature, but not under the heatwave scenario. Overall, these results indicate that heatwaves have the potential both to amplify and disrupt non-trophic interactions, with implications for seagrass seed germination. [ABSTRACT FROM AUTHOR]

Introduction: As suspension-feeders, bivalves play a key role in maintaining regulatory functions of coastal ecosystems, which are linked to important ecosystem services. The functions attributed to bivalves depend on the life habits of a species (epi- or infauna) and their abundance and biomass. To properly quantify and assess these functions, detailed information the distribution, abundance and biomass at the ecosystem scale is critical. Amongst others, this requires an understanding on how environmental conditions shape special patterns in distribution. In this study we investigate this fundamental information on the Swedish west coast, an area where this information is lacking. Methods: A survey which was designed to representatively sample both epi- and infaunal bivalves from randomized locations in various habitat types was conducted. Specifically, abundance and biomass of all species were recorded in the intertidal (0-0.5 m) and the shallow subtidal zone (0.5-2 m). The sites were distributed over an offshore gradient and at two exposure levels. This sampling structure allowed to extrapolate the results to an ecosystem level though information on the areal extent of these habitats using GIS layers. Results: It was found that even though there exist a great variability among sites, in general epifaunal bivalves outweigh infaunal bivalves approximately 3 to 1. In terms of abundance, the ratio is more or less reversed and infaunal species occur in greater numbers. Most bivalves were found at an intermediate level of exposure, but due to the areal extend of the sheltered inner-archipelago this was the most important habitat for bivalve abundance and biomass. It was also found that invasive epifaunal oyster Magallana gigas and the invasive infaunal clam Ensis leei both dominated their respective groups in terms of biomass. Discussion: Though the survey was relatively small, these results serve as a valuable insight of the relative importance of epi- and infaunal bivalves in this region. This gives understanding on which species and habitats are particularly important for ecosystem functions and services related to bivalves. This also provide a starting baseline for attempts to quantify ecosystem services provided by certain species or groups of bivalves in the future. [ABSTRACT FROM AUTHOR]

Cold seeps are areas characterised by specialized biological communities that rely on chemosynthesis for their nutrition. To date, research conducted on New Zealand's Hikurangi Margin seep communities has focused on communities at 650-1200 m water depth. Here, we characterize the macrofaunal nematode communities of New Zealand cold seeps for the first time, and at deeper (> 1200 m) seep locations (Maungaroa, Glendhu and Urutī South). There were no significant difference in nematode abundance, species richness, diversity and evenness among the seep areas, which may reflect the lack of difference in most sediment variables. However, a consistent spatial pattern in nematode abundance was observed within all the seep areas on the Hikurangi Margin: abundance was highest at or near the seep centre, decreased steeply away from the centre and was low in the periphery. These spatially consistent patterns reflect the influence of methane seepage, which appears limited to the inner 150-200 m radius of each area, on nematode abundance via input of chemosynthetic food sources. We found significant differences in nematode community structure among all three areas, with most of the heterogeneity in community structure between the shallow Urutī South area and deeper Maungaroa and Glendhu areas, and differences among nematode communities of high, medium and low abundance associated with site-specific gradients in methane seepage. Within area variability in nematode community structure was mainly correlated with food availability and sediment grain size. Consistent with previous investigations of seep nematodes, we did not find evidence of seep endemics. Although deposit feeders were generally the most abundant feeding group, there were differences in the relative abundances of different feeding groups such as microvores and epigrowth feeders among the seep areas, and as a function of distance from the centre of the seep areas. Impact on seep communities from gas hydrate extraction processes may occur via reduction or potentially cessation of free-gas methane supply to the seafloor, 'sand' production at the seafloor due to the physical degradation of the substrate structure, or alteration of the structural integrity of the seafloor substrate. Any spatial management options considered for managing these impacts should reflect the differences in benthic community structure between depths and locations on the Hikurangi Margin. [ABSTRACT FROM AUTHOR]

Context: Integration of Indigenous ecological knowledge (IEK) and Traditional Owner participation in the co-design of field-sampling techniques can optimise data collection on fisheries resources, that may be under-represented when using conventional scientific knowledge (CSK) alone. Aims: To co-design an IEK-informed sampling methodology to assess counts and size–frequency distribution of an aggregated sandy shore mollusc, Donax deltoides (garlaany, pipi). Methods: We worked with Traditional Owners to co-design a sampling regime synonymous with traditional harvesting techniques. This method was then applied to an assessment of D. deltoides on the Mid North Coast, New South Wales, Australia, at Stuarts Point Beach, over 13 months from November 2021 to November 2022. Key results: This co-designed methodology differed from CSK by using non-random site selection and sampling techniques informed by cultural practice. The standardised methodology was repeatable, quantitative and successfully detected significant spatial and temporal variation in D. deltoides counts and size–frequency distribution, as well as correlations with environmental variables. Conclusions: A co-designed framework that integrates IEK can provide quantitative assessments of counts and size–frequency distributions in an exploited aggregated sandy shore mollusc. Implications: IEK and Traditional Owner participation can facilitate scientifically rigorous data collection on culturally important species, while fostering stewardship and co-management. The integration of Indigenous ecological knowledge and Traditional Owner participation in the co-design and application of field-sampling techniques can optimise data collection on important fisheries resources, especially those that may be under-represented when using conventional scientific methods alone. This co-designed research project was successful in developing a scientifically rigorous data-collection strategy for a culturally important species, while fostering stewardship and co-management. This article belongs to the collection: Science in Sea Country. [ABSTRACT FROM AUTHOR]

Species composition, abundance, ecological structure and spatial distribution of macrobenthos are considered in landscape and ecological conditions of the Astafiev and Srednyaya Bights in the eastern part of the Far Eastern Marine Biosphere State Nature Reserve. The main types of landscapes are identified on the data of landscape profiling. Granulometric composition of soils and organic matter content in the bottom sediments are analyzed. A total of 77 species are found in the macrobenthos of both bights. There are 28 species of epibenthos (similarity between bights by Jaccard index is 93 %) and 53 species of infauna (similarity 23 %), including 4 species common for both biotopes. Different ecological processes in the bottom-macrobenthos system occur in these nearby bights that affects biological diversity, abundance and structure of soft-soil benthos. Despite geomorphological similarity of the bights, the bottom environment in the Astafiev Bight is more enriched in organic matter, but taxonomic composition and abundance of infauna is poorer there. Bulk release of terrigenous matter from the eroded shore of Gamov Peninsula to this bight after rains destabilizes and jeopardizes its bottom environments and prevents formation of biologically stable, diverse and abundant benthos. In the neighbor Srednyaya Bight with a less erosive coastline, the bottom sediments are formed by marine processes mostly, so the macrobenthos on soft soils is distinguished there by great biodiversity. The epibenthos in both bights has no such differences and is represented by the most common species for Peter the Great Bay.

Cumaceans mostly inhabit marine environments, where they play a crucial role in marine food webs and actively participate in the transfer between benthic and pelagic systems. Scientific interest in these crustaceans has been increasing, but is limited to certain geographic areas, which do not include extreme environments such as hydrothermal vents.Therefore, this study aimed to report the distribution of cumaceans in shallow-water hydrothermal vents at Banderas Bay and to identify the specimens present. Three sites were selected (20°44’54.7”N, 105°28’40.6”W; 20°44’54.8”N, 105°28’40.4”W; 20°44’54.9”N, 105°28’38.4”W) and each site was divided into three zones, based on sediment temperature. Through SCUBA diving, 27 sediment cores were collected. The samples were processed and identified in the laboratory. The families Bodotriidae T. Scott, 1901; Pseudocumatidae Sars, 1878; and Diastylidae Bate, 1856; were recorded and six morphospecies were identified. This work leaves a preliminary frame of reference for future studies related to the biodiversity of cumacean in Hydrothermal vents environments.

Many indicators have been developed to assess the state of benthic communities and identify seabed habitats most at risk from bottom trawling disturbance. However, the large variety of indicators and their development and application under specific geographic areas and management contexts has made it difficult to evaluate their wider utility. We compared the complementarity/uniqueness, sensitivity, and selectivity of 18 benthic indicators to pressure of bottom trawling. Seventeen common datasets with broad regional representation covering a range of pressure gradients from bottom trawling disturbance (n = 14), eutrophication (n = 1), marine pollution (n = 1), and oxygen depletion (n = 1) were used for the comparison. The outcomes of most indicators were correlated to a certain extent with response to bottom trawling disturbance, and two complementary groups of indicators were identified: diversity‐based and biological trait‐based indicators. Trait‐based indicators that quantify the changes in relative abundance of sensitive taxa were most effective in identifying benthic community change in response to bottom trawling disturbance. None of the indicators responded to the trawling pressure gradient in all datasets, and some showed a response that were opposed to the theoretical expectation for some gradients. Indicators that showed clear responses to bottom trawling disturbance also showed clear responses in at least one other pressure gradient, suggesting those indicators are not pressure specific. These results emphasize the importance of selecting several indicators, at least one from each group (diversity and trait‐based), to capture the broader signals of change in benthic communities due to bottom trawling activities. Our systematic approach offers the basis from which scientific advisors and/or managers can select suitable combinations of indicators to arrive at a sensitive and comprehensive benthic status assessment. [ABSTRACT FROM AUTHOR]

The multifunctional catalytic hemoglobin from the terebellid polychaete Amphitrite ornata, also named dehaloperoxidase (AoDHP), utilizes the typical oxygen transport function in addition to four observed activities involved in substrate oxidation. The multifunctional ability of AoDHP is presently a rare observation, and there exists a limitation for how novel dehaloperoxidases can be identified from macrobenthic infauna. In order to discover more infaunal DHP-bearing candidates, we have devised a facilitated method for an accurate taxonomic identification that places visual and molecular taxonomic approaches in parallel. Traditional visual taxonomic species identification by the non-specialist, at least for A. ornata or even for other marine worms, is a very difficult and time-consuming task since a large diversity is present and the method is restricted to adult worm specimens. The work herein aimed to describe a method that simplifies the taxonomic identification of A. ornata in particular through the assessment of its mitochondrial cytochrome c oxidase subunit I gene by employing the DNA barcoding technique. Furthermore, whole-worm specimens of A. ornata were used to extract and purify AoDHP followed by an H2O2-dependent peroxidase activity assay evaluation against substrate 2,4,6-trichlorophenol. AoDHP isoenzyme A was also overexpressed as the recombinant protein in Escherichia coli, and its peroxidase activity parameters were compared to AoDHP from the natural source. The activity assay assessment indicated a tight correlation for all Michaelis–Menten parameters evaluated. We conclude that the method described herein exhibits a streamlined approach to identify the polychaete A. ornata, which can be adopted by the non-specialist, and the full procedure is predicted to facilitate the discovery of novel dehaloperoxidases from other marine invertebrates. [ABSTRACT FROM AUTHOR]

Background: Cumaceans mostly inhabit marine environments, where they play a crucial role in marine food webs and actively participate in the transfer between benthic and pelagic systems. Scientific interest in these crustaceans has been increasing, but is limited to certain geographic areas, which do not include extreme environments such as hydrothermal vents. New information: Therefore, this study aimed to report the distribution of cumaceans in shallow-water hydrothermal vents at Banderas Bay and to identify the specimens present. Three sites were selected (20°44'54.7"N, 105°28'40.6"W ; 20°44'54.8"N, 105°28'40.4"W ; 20°44'54.9"N, 105°28'38.4"W) and each site was divided into three zones, based on sediment temperature. Through SCUBA diving, 27 sediment cores were collected. The samples were processed and identified in the laboratory. The families Bodotriidae T. Scott, 1901; Pseudocumatidae Sars, 1878; and Diastylidae Bate, 1856; were recorded and six morphospecies were identified. This work leaves a preliminary frame of reference for future studies related to the biodiversity of cumacean in Hydrothermal vents environments. [ABSTRACT FROM AUTHOR]

Fine-grained organic-rich sediments (FGORSs) from anthropogenic impacts are a growing concern for bays and estuaries around the world. This study explores the relationships of infaunal community diversity and species abundances with FGORSs in the Indian River Lagoon and its tributaries. To examine these potential relationships, infauna was collected monthly using a Petite Ponar grab at 16 stations in the central Indian River Lagoon from October 2015 to August 2016. Abundant taxa in these sediments include polychaete worms (e.g., the polychaete Nereis succinea), mollusks (e.g., clam Parastarte triquetra), and arthropods (e.g., the tanaid Leptochelia dubia), with densities as high as 5.3 × 104 m−2 (L. dubia in July 2016). Increasing organic matter (OM) in the sediments was inversely correlated with species richness (R2 = 0.75; p-value < 0.001), densities (R2 = 0.69; p-value < 0.001), and diversity (R2 = 0.37; p-value < 0.001). Other infaunal community and population data showed similar relationships with silt–clay (%), sediment porosity, and dissolved oxygen (mg L−1). Two thresholds of OM and correlated environmental parameters are discussed: an impairment threshold at 2% OM, above which infauna decreases precipitously, and a critical threshold at 10% OM, above which infauna is generally absent. [ABSTRACT FROM AUTHOR]

The recent expansion of the aquaculture industry into the offshore marine environment is perceived to have a comparatively low environmental impact coupled with a high growth potential as a sustainable, large‐scale source of healthy protein. This study assessed changes in sediment characteristics and infauna assemblages following the development of the first large‐scale offshore longline mussel farm in the United Kingdom. By evaluating the effects of the farm on the sediment ecosystem and by studying infaunal sediment environmental parameters along a distance gradient away from the farm, the first before–after control–impact (BACI) study of an offshore shellfish farm is presented. Sediment grabs from the farm and control sites were analysed for sediment parameters (organic matter content (OM), particle size (PS), oxidation–reduction or redox potential (ORP) and trace elements) and infauna assemblages. There was no difference in sediment organic matter levels between the farm and control sites. Within the farm, the mean sediment grain size and ORP increased over time. Trace element concentrations were the lowest within farm sites compared to outside; concentrations increased with increasing distance from the farm. A total of 76 benthic macrofauna taxa were identified, with polychaetes being the dominant class. Over time, the number of taxa significantly increased within the farm while remaining relatively constant in control samples. Biodiversity metrics, including abundance and Shannon and Pielou's index, were all greater within the farm compared to control areas. Overall, measures of assemblage health were higher within the farm than outside. This study demonstrates the long‐term aquaculture–environment interactions that offshore shellfish farming can have on the seabed and its significance in terms of ecosystem services. [ABSTRACT FROM AUTHOR]

Submerged aquatic vegetation (SAV) growth can be limited by light and nutrient availability. Infauna are common inhabitants of SAV meadows. Their activity increases nutrient mobility, and they can positively affect plant growth, but we do not know their role in plant trait‐biomass production relationships. We approached this problem using a 15‐week in situ transplant experiment in the Baltic Sea with experimental additions of Macoma balthica, a sedentary bivalve, to experimental SAV communities. Experimental plant communities were tricultures with varying species composition, compiled from a pool of six different species, to create an experimental gradient of trait community weighted means that allowed us to detect changes more clearly in plant trait‐biomass production relationships in response to the M. balthica treatment. We evaluated the relationships between plant height, leaf area, maximum root length (MMRL), specific root length (SRL), and SAV biomass production, then compared M. balthica condition index (soft tissue biomass [WW, mg]/valve length [mm]) to plant community leaf tissue nutrient concentrations (N (%DW), δ15N). Community biomass production was significantly related to plant height in the control treatment, but this relationship was decoupled in the M. balthica treatment, where community biomass production was instead significantly related to MMRL and SRL. This suggested a shift in the predominant SAV growth strategy, from height‐related to root‐related community biomass production. Leaf tissue δ15N was significantly related to M. balthica condition index. The growth of one species, Potamogeton perfoliatus, was significantly inhibited by the M. balthica treatment. Our results show that infauna have an important role in the plant traits related to community biomass production, and they have the potential to shape plant community structure via selective influences on different plant species. [ABSTRACT FROM AUTHOR]

Cold seeps are areas characterised by specialized biological communities that rely on chemosynthesis for their nutrition. To date, research conducted on New Zealand’s Hikurangi Margin seep communities has focused on communities at 650-1200 m water depth. Here, we characterize the macrofaunal nematode communities of New Zealand cold seeps for the first time, and at deeper (> 1200 m) seep locations (Maungaroa, Glendhu and Urutī South). There were no significant difference in nematode abundance, species richness, diversity and evenness among the seep areas, which may reflect the lack of difference in most sediment variables. However, a consistent spatial pattern in nematode abundance was observed within all the seep areas on the Hikurangi Margin: abundance was highest at or near the seep centre, decreased steeply away from the centre and was low in the periphery. These spatially consistent patterns reflect the influence of methane seepage, which appears limited to the inner 150-200 m radius of each area, on nematode abundance via input of chemosynthetic food sources. We found significant differences in nematode community structure among all three areas, with most of the heterogeneity in community structure between the shallow Urutī South area and deeper Maungaroa and Glendhu areas, and differences among nematode communities of high, medium and low abundance associated with site-specific gradients in methane seepage. Within area variability in nematode community structure was mainly correlated with food availability and sediment grain size. Consistent with previous investigations of seep nematodes, we did not find evidence of seep endemics. Although deposit feeders were generally the most abundant feeding group, there were differences in the relative abundances of different feeding groups such as microvores and epigrowth feeders among the seep areas, and as a function of distance from the centre of the seep areas. Impact on seep communities from gas hydrate extraction processes may occur via reduction or potentially cessation of free-gas methane supply to the seafloor, ‘sand’ production at the seafloor due to the physical degradation of the substrate structure, or alteration of the structural integrity of the seafloor substrate. Any spatial management options considered for managing these impacts should reflect the differences in benthic community structure between depths and locations on the Hikurangi Margin.

Abstract Background Thyasirid bivalves are often recorded as a dominant component of macrobenthic infaunal communities in depositional environments such as fjord basins. Fjord basins comprise patchy soft-bottom habitats bounded by steep walls and sills; however, little is known how this semi-isolated nature of fjords affects benthic populations. Accordingly, data on the composition and population connectivity of thyasirids can provide valuable information on the ecology of these ecosystems. Results The species composition of thyasirid bivalves has been studied in the basins of three sub-Arctic fjords (Nordland, Northern Norway). Overall, six thyasirid species were recorded: Parathyasira equalis, Parathyasira dunbari, Mendicula ferruginosa, Genaxinus eumyarius, Thyasira sarsii, and Thyasira obsoleta. The species composition remained stable within the basins during the sampling period (2013–2020) and suggested the importance of local reproduction over advection of individuals for population dynamics. Only one species, Parathyasira equalis, was common in all fjords. We have further investigated the population genetics of this species by combining two types of genetic markers: a 579 bp fragment of the cytochrome c oxidase subunit I (COI) gene and 4043 single-nucleotide polymorphisms (SNPs) generated by genotyping-by-sequencing. The latter provided a more in-depth resolution on the population genetics of this species and revealed a weak but significant differentiation of populations within fjords, further indicating limited connectivity between basins. Conclusion Based on our findings, we conclude that limited dispersal between the basin communities results in weakly connected populations and might be an important structuring factor for macrobenthic communities.

The multifunctional catalytic hemoglobin from the terebellid polychaete Amphitrite ornata, also named dehaloperoxidase (AoDHP), utilizes the typical oxygen transport function in addition to four observed activities involved in substrate oxidation. The multifunctional ability of AoDHP is presently a rare observation, and there exists a limitation for how novel dehaloperoxidases can be identified from macrobenthic infauna. In order to discover more infaunal DHP-bearing candidates, we have devised a facilitated method for an accurate taxonomic identification that places visual and molecular taxonomic approaches in parallel. Traditional visual taxonomic species identification by the non-specialist, at least for A. ornata or even for other marine worms, is a very difficult and time-consuming task since a large diversity is present and the method is restricted to adult worm specimens. The work herein aimed to describe a method that simplifies the taxonomic identification of A. ornata in particular through the assessment of its mitochondrial cytochrome c oxidase subunit I gene by employing the DNA barcoding technique. Furthermore, whole-worm specimens of A. ornata were used to extract and purify AoDHP followed by an H2O2-dependent peroxidase activity assay evaluation against substrate 2,4,6-trichlorophenol. AoDHP isoenzyme A was also overexpressed as the recombinant protein in Escherichia coli, and its peroxidase activity parameters were compared to AoDHP from the natural source. The activity assay assessment indicated a tight correlation for all Michaelis–Menten parameters evaluated. We conclude that the method described herein exhibits a streamlined approach to identify the polychaete A. ornata, which can be adopted by the non-specialist, and the full procedure is predicted to facilitate the discovery of novel dehaloperoxidases from other marine invertebrates.

Fine-grained organic-rich sediments (FGORSs) from anthropogenic impacts are a growing concern for bays and estuaries around the world. This study explores the relationships of infaunal community diversity and species abundances with FGORSs in the Indian River Lagoon and its tributaries. To examine these potential relationships, infauna was collected monthly using a Petite Ponar grab at 16 stations in the central Indian River Lagoon from October 2015 to August 2016. Abundant taxa in these sediments include polychaete worms (e.g., the polychaete Nereis succinea), mollusks (e.g., clam Parastarte triquetra), and arthropods (e.g., the tanaid Leptochelia dubia), with densities as high as 5.3 × 104 m−2 (L. dubia in July 2016). Increasing organic matter (OM) in the sediments was inversely correlated with species richness (R2 = 0.75; p-value < 0.001), densities (R2 = 0.69; p-value < 0.001), and diversity (R2 = 0.37; p-value < 0.001). Other infaunal community and population data showed similar relationships with silt–clay (%), sediment porosity, and dissolved oxygen (mg L−1). Two thresholds of OM and correlated environmental parameters are discussed: an impairment threshold at 2% OM, above which infauna decreases precipitously, and a critical threshold at 10% OM, above which infauna is generally absent.

Extreme hypersaline environments are known to be challenging ecosystems for the survival of organisms. These extreme environments are characterized by high evaporation, resulting in a drastic reduction in the ichnological and bioturbational diversity. Moreover, such environments are poorly understood on account of limited documentation in rock records. The Great Rann of Kachchh forms an exclusive salt-encrusted geomorphic facet and is India's most extensive exposure to hypersaline deposits. The area is inundated by tidal ingress from the Arabian Sea during the monsoon, followed by an evaporative period. Moreover, tidal ingress in the Rann of Kachchh and its effect on the ecology ispoorly documented. Ichnological investigations of the hypersaline Great Rann of Kachchh revealed four recurring trace fossils, Arenicolites, Palaeophycus, Polykladichnus, and Skolithos, with annelids, and crustaceans as the most likely producers. Furthermore, the existence of their juvenile forms is indicated by the presence of small and tiny subsurface burrows. Hence, in the present research, we used ichnology to document the limit and mechanism of tidal ingress to demarcate the tidal inundation boundary up to the east of Khadir Island. We propose a hypothesis identifying the tidal inundation limit by larval recruits burrows and present an ichnological model for a hypersaline environment. [ABSTRACT FROM AUTHOR]

The <3% dissimilar Amplicon Sequence Variant (ASV) clusters of the 18S‐V4 barcode were used as species‐proxies for the evaluation of ASV composition and ASV diversity indices characterizing the hitherto poorly investigated meiofaunal communities of the south‐eastern part of the Levantine basin. Accompanied by abundance measurements, the relationships of these characteristics with sedimentary and bottom terrain parameters were interpreted. The construction of community composition profiles, namely ASVs' list and their estimated abundances, was done using our previously established procedure (Harbuzov et al., 2022, Marine Genomics 65, 100980), combining metabarcoding with sample reads normalization by the abundance of hard‐bodied meiofaunal taxa. The study province included the 54–1418 m depth range, across vertical sub‐bottom horizons ranging 0–17 cm. Oxygen, hydrogen sulfide and methane concentrations in the pore water, as well as sediment grain size spectra and sedimentary protein and carbohydrate levels, were measured, followed by an evaluation of their involvement in the shaping of the meiofaunal communities' characteristics. Community composition was generally site‐and‐horizon dependent and its abundance decreased with increasing bottom depth and across sub‐bottom horizons, typical to benthic habitats which are nourished by organic carbon from the euphotic zone. The relatively sharply inclined continental slope bottom located in the northern part of the Israeli coast was an exception. Its meiofaunal community characteristics were speculated to be affected by intensive sediment mixing and lateral transport of food from the shelf, in addition to the effect of the euphotic zone‐originated food sources. [ABSTRACT FROM AUTHOR]

Intensive temporal and spatial sampling of benthic infauna have rarely been analysed to improve impact assessment or conservation planning. An impact assessment started in the late 1980s in Jervis Bay (Australia) provided a spatially, temporally and taxonomically comprehensive benthic invertebrate dataset. While the proposed development did not eventuate, the area was later declared a multi‐zone marine park.We specifically used the polychaete data which included nine sampling times (February 1989 to June 1991) in seagrass and unvegetated sediments across multiple sites to identify ecological patterns that could inform current and future conservation management and impact assessment.The polychaete assemblage was diverse with 171 species, many of them rare (40% < 10 individuals). Variation was greatest at small spatial scales (metres) for abundances and diversity, and there was substantial spatio‐temporal variation due to inconsistent site differences. Most species occurred in both unvegetated and seagrass sediments, though several were more abundant or restricted to one habitat (39% and 3% only found in unvegetated or seagrass, respectively), or showed bathymetric differences in abundances (e.g., Eunice cultrifera and Lumbrineris cf. latrelli).The current marine park zoning representatively covered polychaete biodiversity, as all sites were generally similar in terms of abundances and species richness. It also representatively covered seagrass and unvegetated sediments and the bathymetric range of the embayment. These findings reinforce the utility of using habitats as surrogates to representatively zone for biological diversity.The high levels of spatial and spatio‐temporal variation in abundances and diversity only allowed detection of environmental impacts with >70% effect sizes even if numerous sites and times were sampled (i.e., > seven sites and > eight times). This suggests that most univariate measures for polychaetes would only be useful to detect enormous effects, and effective impact assessment might require more sophisticated multivariate approaches. [ABSTRACT FROM AUTHOR]

Introduction: Ecosystem engineers play a pivotal role in shaping habitats through their activities and presence. In shallow Baltic waters, seagrasses, patch-forming mussels, and infaunal clams modify soft bottom habitats, impacting benthic community structure. While the individual effects of these ecosystem engineers are well studied, interactions among co-occurring engineers are poorly understood. Methods: We conducted a mesocosm experiment to assess the independent and combined impacts of seagrass (Zostera marina), epifaunal mussels (Mytilus spp.), and infaunal clams (Macoma balthica) on invertebrate colonization in soft sediments. Results: Our findings reveal significant engineer-driven alterations in macrofaunal community structure. Combined engineer effects diverged from individual impacts, indicating potential synergies or antagonisms in sediment (re) colonization. Notably, a higher number of engineer species positively affected the diversity of settled macrofauna, with the lowest macrofaunal abundance and biomass but the highest Shannon diversity found in the presence of all three engineers. Discussion: Results suggest that seagrass, mussels, and clams influence benthos through larval settlement and sediment biogeochemistry, providing insights into the distinct roles of habitat-forming organisms in shaping the benthic communities in coastal ecosystems of the Baltic Sea. [ABSTRACT FROM AUTHOR]

Interest in deep-sea mining for polymetallic nodules as an alternative source to onshore mines for various high-technology metals has risen in recent years, as demands and costs have increased. The need for studies to assess its short- and long-term consequences on polymetallic nodule ecosystems is therefore also increasingly prescient. Recent image-based expedition studies have described the temporal impacts on epi-/megafauna seafloor communities across these ecosystems at particular points in time. However, these studies have failed to capture information on large infauna within the sediments or give information on potential transient and temporally limited users of these areas, such as mobile surface deposit feeders or fauna responding to bloom events or food fall depositions. This study uses data from the Peru Basin polymetallic nodule province, where the seafloor was previously disturbed with a plough harrow in 1989 and with an epibenthic sled (EBS) in 2015, to simulate two contrasting possible impact forms of mining disturbance. To try and address the shortfall on information on transient epifauna and infauna use of these various disturbed and undisturbed areas of nodule-rich seafloor, images collected 6 months after the 2015 disturbance event were inspected and all Lebensspuren, ‘traces of life’, were characterized by type (epi- or infauna tracemakers, as well as forming fauna species where possible), along with whether they occurred on undisturbed seafloor or regions disturbed in 1989 or 2015. The results show that epi- and endobenthic Lebensspuren were at least 50% less abundant across both the ploughed and EBS disturbed seafloors. This indicates that even 26 years after disturbance, sediment use by fauna may remain depressed across these areas. [ABSTRACT FROM AUTHOR]

The correction notice in the journal "Frontiers in Marine Science" addresses an error in Figure 4 of the article "Estimating and scaling-up biomass and abundance of epi- and infaunal bivalves in a Swedish archipelago region." The corrected figure is provided, and the authors assure that this error does not impact the scientific conclusions of the study. The article has been updated to reflect the correction. [Extracted from the article]

The species composition and the structure of the macrophytobenthos, macrozoobenthos, and bottom sediments of Taman Bay are studied. This inlet is inhabited by seagrass Zosteramarina L. which forms vast underwater meadows here. Samples were collected in 2008–2009, before the ongoing rise of salinity in the Sea of Azov. Three main biotopes with different bottom sediment composition (sands, sands with shells, and silts) were identified. They were inhabited by four main macrobenthic biocenoses (unvegetated near-shore biocenosis, mosaic macrophyte vegetation outside the surf zone, pure eelgrass's meadows belt, and the communities, dominated by the mobile macrozoobenthos species with low abundance of macrophytes occupying the central part of the bay). The main environmental factor associated with this distribution of the vegetation was the silt content (grain size <0.001 mm). The spatial structure of the macrozoobenthos correlated with the projective cover of Z. marina. Possible reasons for the revealed pattern in the distribution of communities are discussed. [ABSTRACT FROM AUTHOR]

The deep sea (>200m depth) off South Africa is largely unexplored, with most benthic macrofauna samples limited to depths shallower than 100m. The benthic infaunal diversity of the Agulhas Bank shelf edge has not yet been studied. We analysed seven grab samples that were opportunistically collected along the shelf edge at depths of 290-533 m. A total of 136 macrofauna items representing 75 species were identified, and the first species list of the infauna of the shelf edge was compiled, Polychaetes comprised 48% of total abundance, and the sites had an average similarity of 7% based on species abundance, Spearman rank correlation showed that depth and sediment particle size are important environmental drivers of community abundance and biomass variation on the shelf edge, Habitat heterogeneity is likely high along the Agulhas Bank shelf edge, Greater sampling effort in habitats for which data are scarce provides crucial information for offshore biodiversity assessment and management [ABSTRACT FROM AUTHOR]

Low inflows cause predominantly hypersaline conditions in Baffin Bay, TX (USA), which are inhospitable for oysters, the dominant reef-builder in other northern Gulf of Mexico estuaries. Instead, extensive biogenic reefs contain dense aggregations of the ubiquitous tube-building serpulid worm, Hydroides dianthus. The distribution and size of these reefs have declined over the last several decades. Although serpulid reef habitats have increased in conservation importance, there is a need for ecological knowledge to inform resource management and habitat restoration planning. This study examined spatial and temporal recruitment patterns of serpulid worms and other encrusting species over an 18-month-long period, using recruitment tiles, and live serpulid reef as a reference. Recruitment of H. dianthus occurs year-round; however, the greatest recruitment occurs between September and December. No consistent differences in serpulid recruitment were detected among locations within Baffin Bay, which could be because salinity and temperature were similar among locations, and/or because sampling replication was low. H. dianthus cover was greater on the lower surface of horizontally oriented recruitment tiles (28% cover), whereas Amphibalanus eburneus (barnacle) cover dominated the upper surface of tiles (34% cover). Furthermore, there is no evidence that predation by megafauna (> 1 cm) is hindering serpulid recruitment. There is sufficient larval supply of H. dianthus to suggest that the restoration of serpulid reefs can be successful by providing additional substrate with appropriate microhabitat complexity. Study findings can be used to support planning and successful implementation of serpulid reef restoration. [ABSTRACT FROM AUTHOR]

This study investigates an account on the diversity and abundance of benthic infauna of Chettuva mangrove in Kerala. Marine benthic infaunal species are an important factor in marine ecosystems and play a chief ecological function in the mangrove ecosystem. This research article gives an overview of infaunal diversity associated with eight sites of Chettuva mangrove. The present study revealed that infaunal species are significantly moderate within this mangrove ecosystem.

Marine sublittoral sandbanks are essential offshore feeding grounds for larger crustaceans, fish and seabirds. In the southern North Sea, sandbanks are characterized by considerable natural sediment dynamics and are subject to chronic bottom trawling. However, except for the Dogger Bank, sandbanks in the southeastern North Sea have been only poorly investigated until now. We used an extensive, multi-annual dataset covering ongoing national monitoring programmes, environmental impact assessments, and basic research studies to analyse benthic communities on sublittoral sandbanks, evaluating their ecological value against the backdrop of similar seafloor habitats in this region. The analysis revealed complex spatial structuring of sandy seafloor habitats of the southeastern North Sea. Different infauna clusters were identified and could be specified by their composition of characteristic species. The sandbanks shared common structural features in their infauna community composition although they were not necessarily characterized by particularly high biodiversity compared to other sandy habitats. A close association of one of the main bioturbators in the southern North Sea, the sea urchin Echinocardium cordatum, with sandbanks was detected, which may promote the sediment-bound biogeochemical activity in this particular seafloor habitat. This would corroborate the status of sandbanks as sites of high ecological value calling for consideration in marine conservation. [ABSTRACT FROM AUTHOR]

Infaunal organisms mix sediments through burrowing, ingestion and egestion, enhancing fluxes of nutrients and oxygen, yet the mechanisms underlying bioturbation remain unresolved. Burrows are extended through muddy sediments by fracture, and we hypothesize that the cohesive properties of sediments play an important but unexplored role in resisting bioturbation. Specifically, we suggest that crack branching, tortuosity, and microcracking are important in freeing particles from the cohesive matrix, and that the sediment properties that affect these processes are important predictors of bioturbation. We use finite element modeling and simplified, mechanics‐based models to explore the relative importance of sediment mechanical properties and worm behaviors in determining crack propagation paths. Our results show that crack propagation direction depends on variability in fracture toughness, and that applying more force to one side of the burrow wall, simulating "steering" behavior, has surprisingly little effect on crack propagation direction. Burrowers instead steer by choosing among crack branches. Paths created by burrowing worms in natural sediments are mostly straight with some crack branching, consistent with modeling results. Crack branching also requires sufficient stored elastic energy to drive two cracks, and worms can exert larger forces resulting in more stored energy in stiffer sediments. This implies that more crack branching and consequently more particle mixing occurs in heterogeneous sediments with low fracture toughness relative to stiffness. Whether sediments with greater potential for crack branching also experience higher bioturbation remains to be tested, but these results indicate that material properties of sediments may be important in resisting or facilitating bioturbation. Plain Language Summary: Worms and other animals living in the sea floor mix sediments, helping to break down organic material and regenerate nutrients. Physical processes like mixing occur when a driving force, here the burrowing and feeding by animals, exceeds a resisting force. In muds, the resisting force comes from the sticky organic material that holds the mineral grains together. Animals extend burrows through muds by fracturing this organic matrix to create new burrow space. We modeled crack propagation through materials that differed in their fracture resistance and compared our results to paths made by worms in natural muds. Worms can't easily steer their burrows by pushing on one side of the burrow wall; instead they create crack branches and then choose a branch to follow to change direction. Crack branching requires variability in the resistance to fracture on small scales, and more crack branching occurs when muds are stiff and crumbly rather than soft and squooshy. Burrowing worms compact sediments on small scales as they move. These changes may improve their habitat by making burrowing easier, a process called ecosystem engineering. Key Points: Crack branching and microcracking that occur when burrows are extended through sediments by fracture contribute to sediment bioturbationWorms can't steer burrows when extending them by fracture; instead they use crack branching to change directionHeterogeneity in fracture toughness drives crack branching; more heterogeneous, compact sediments have lower resistance to bioturbation [ABSTRACT FROM AUTHOR]

Seagrass meadows and their associated biodiverse assemblages have declined globally due to environmental and anthropogenic stressors. Restoration of these critical habitats has the potential to reverse coastal biodiversity loss. Here, we tested the role of patch size (which can affect recruitment, food availability, and/or predation) in driving faunal colonization in an eelgrass (Zostera marina) restoration trial in Sweden. Eelgrass shoots were transplanted in plots with different configurations (continuous vs. checkerboard patterns with three patch sizes), and we followed invertebrate colonization (biodiversity and functional diversity) during the first two growing seasons. We found rapid faunal colonization following the transplantation of eelgrass shoots in all plots with invertebrate densities reaching 50–80% of the reference meadow after only one growing season (3 months). After two growing seasons (15 months), the faunal density, biodiversity, and functional diversity were similar to the reference meadow, despite eelgrass density and biomass still being lower than the reference meadow. Biodiversity, functional diversity, and community structure were similar among the different planted plots, that is, there was no indication that patch size influenced faunal colonization. We therefore consider that smaller patches embedded within larger restoration plots can be as effective for promoting biodiversity as continuous patches, with reduced costs and fewer shoots required. We also noted high natural variability between years both in the reference meadow and planted plots, showing the dynamic nature of seagrass ecosystems, and the importance of a well‐planned monitoring scheme that considers the reference area and restored area within the same temporal scale. [ABSTRACT FROM AUTHOR]

Infaunal invertebrate communities are structured by various factors, including predation, resource availability, and environmental conditions. Given that these invertebrates live within sediment, it is not surprising that sediment properties play a critical role in many infaunal behaviours. When models explaining spatial and temporal variation in infaunal community composition are constructed using physical, biophysical, environmental, and sediment properties (salinity, detrital cover, elevation, particle size distribution, organic and water content, redox conditions, and penetrability), a considerable portion of the variation in the data is typically unaccounted for. This suggests that we do not fully understand all the variables that influence infaunal invertebrate communities. One suite of under-explored variables is the elemental composition/concentration of the sediments themselves. As such, we evaluated if sediment geochemistry improved model performance of the spatial variation in infaunal invertebrate communities on three intertidal mudflats in northern British Columbia, Canada. We observed that models including geochemistry data outperformed models that only included physical, biophysical, and environmental properties. Our results, therefore, suggest that some of the observed, and previously unaccounted for spatial variation in infaunal community composition may be a product of variation in sediment geochemistry. As such, sediment geochemistry should be accounted for when studying infaunal communities and assessing human impacts upon intertidal systems. [ABSTRACT FROM AUTHOR]

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The current study seeks to identify possible anthropogenic and/or natural environmental stressors that may account for the long-term decline of ecosystem health in Lavaca Bay, Texas, USA. The Formosa Plastics Corporation instituted monitoring of an industrial discharge into the bay with 16 fixed point stations and quarterly sampling from 1993 to 2020. Comprehensive measurements included organic and inorganic solutes in surface water, porewater and sediment, sediment content, plankton, nekton, and infaunal benthos. All parameter trends changed over time due to climate, freshwater inflow events, and/or seasonal changes. Biological community structure and sediment changed with distance from the discharge site. Dominance characterized community structure because three to four taxa comprised > 70% of individuals for nekton (trawl and gill net), phytoplankton, zooplankton, and ichthyoplankton samples. Sediment became sandier over time (48 to 75%) and away from the discharge. Surface water and porewater at reference (R) stations and stations near the discharge site had similar hydrographical and biological trends over time, indicating no long-term impact due to the discharge. However, 99.9% of 424,671 measurements of organic contaminants were non-detectable because the methods were insensitive to ambient concentrations. Thus, it is still not known if contaminants play a role in the long-term decline of ecosystem health in Lavaca Bay. Furthermore, only four R stations were sampled and were all 3810 m from the discharge site, so it is possible that trends in R stations do not represent the natural background. Future studies should include more R stations and lower detection limits for contaminants. [ABSTRACT FROM AUTHOR]

This study investigates an account on the diversity and abundance of benthic infauna of Chettuva mangrove in Kerala. Marine benthic infaunal species are an important factor in marine ecosystems and play a chief ecological function in the mangrove ecosystem. This research article gives an overview of infaunal diversity associated with eight sites of Chettuva mangrove. The present study revealed that infaunal species are significantly moderate within this mangrove ecosystem. [ABSTRACT FROM AUTHOR]

Since the last decades, previous long-term Wadden Sea studies revealed significant changes in the abundance, biomass and spatial distribution of characteristic macrofauna communities in response to environmental changes and anthropogenic stressors. In this study, we performed statistical community analysis for the East-Frisian Wadden Sea (EFWS, southern North Sea) on two reference datasets across a period with severe climatic and environmental changes (1980s-2018). Therefore, historical macrofauna data from the Quantitative Sensitivity Mapping (1980s, SENSI 1) were reanalyzed and compared with data from the Synoptic Intertidal Benthic Survey (SIBES/SENSI 3) collected in 2018. Our results revealed significant quantitative and spatial changes in the characteristic macrofauna communities between the 1980s and 2018, most likely in response to de-eutrophication and sea level rise mediated habitat changes. Since the 1980s, the total number of taxa remained relatively stable (1980s: 90, 2018: 81), but the total abundance decreased by ca. -31% and the total biomass decreased by ca. -45%, particularly in the eastern regions of the study site probably due to de-eutrophication processes. Thereby, the mean abundances/m2 of ≥ -80% (1980s-2018) in the EFWS of several dominant species decreased: e.g. the gastropod Peringia ulvae, the polychaete Lanice conchilega and the bivalve Mya arenaria. In contrast, the mean abundance/m2 of one dominant species increased by ≥ +80% (1980s-2018): the invasive bivalve Ensis leei. The mean biomass [g/m2] of three dominant species decreased by ≥ -80% (1980s-2018): P. ulvae, L. conchilega and the amphipod Corophium volutator. In contrast, the mean biomass [g/m2] of one dominant species increased by ≥ +75% (1980s-2018): the polychaete Arenicola marina. In the western part of the EFWS, not only higher abundances of A. marina, but also of L. conchilega and P. ulvae were found in 2018, caused i.a. by sea level rise mediated decreasing mud contents and sand accretion on tidal flats. At the community level, the Oligochaeta/Heteromastus community increased in spatial distribution in the western EFWS in 2018 in the vicinity of increasing mussel/oyster beds.

IntroductionAs suspension-feeders, bivalves play a key role in maintaining regulatory functions of coastal ecosystems, which are linked to important ecosystem services. The functions attributed to bivalves depend on the life habits of a species (epi- or infauna) and their abundance and biomass. To properly quantify and assess these functions, detailed information the distribution, abundance and biomass at the ecosystem scale is critical. Amongst others, this requires an understanding on how environmental conditions shape special patterns in distribution. In this study we investigate this fundamental information on the Swedish west coast, an area where this information is lacking.MethodsA survey which was designed to representatively sample both epi- and infaunal bivalves from randomized locations in various habitat types was conducted. Specifically, abundance and biomass of all species were recorded in the intertidal (0-0.5 m) and the shallow subtidal zone (0.5-2 m). The sites were distributed over an offshore gradient and at two exposure levels. This sampling structure allowed to extrapolate the results to an ecosystem level though information on the areal extent of these habitats using GIS layers.ResultsIt was found that even though there exist a great variability among sites, in general epifaunal bivalves outweigh infaunal bivalves approximately 3 to 1. In terms of abundance, the ratio is more or less reversed and infaunal species occur in greater numbers. Most bivalves were found at an intermediate level of exposure, but due to the areal extend of the sheltered inner-archipelago this was the most important habitat for bivalve abundance and biomass. It was also found that invasive epifaunal oyster Magallana gigas and the invasive infaunal clam Ensis leei both dominated their respective groups in terms of biomass.DiscussionThough the survey was relatively small, these results serve as a valuable insight of the relative importance of epi- and infaunal bivalves in this region. This gives understanding on which species and habitats are particularly important for ecosystem functions and services related to bivalves. This also provide a starting baseline for attempts to quantify ecosystem services provided by certain species or groups of bivalves in the future.

Simple Summary: Most of the world is ocean, and most of the ocean bottom is mud or sand. Understanding the ecology of sedimentary habitats is therefore important for understanding marine ecosystems writ large. Marine sediments are typically occupied by burrowing and tube-building animals that physically structure the habitat. In coastal sediments, an especially widespread example is the annelid worm Diopatra, which builds large tubes up to 2 m deep and 1 cm in diameter. These tubes have extensive physical effects on other organisms in the habitat, including commercially important fish and crustaceans. Diopatra are currently being impacted by climate change, species invasions, and (in some areas) the bait-digging industry. In this article, I review what we know about Diopatra ecology with an eye to identifying major open questions and future threats facing this important architect of coastal marine systems. A well-known example of marine ecosystem engineering is the annelid genus Diopatra, which builds large tubes in coastal sediments worldwide. Early studies of Diopatra were among the first to recognize the importance of facilitation in ecology, and Diopatra has become a key marine soft-sediment application of the ecosystem engineering concept. Here, I review our current knowledge of Diopatra ecology, including its natural history, ecosystem engineering effects, and trophic relationships. I particularly explore how human activities are influencing Diopatra in terms of climate change, bait fishing, and species invasions. Most of what we know about Diopatra ecology comes from focal studies of a few species in a few well-known regions. Further evaluating how our current understanding applies to other species and/or other regions will help to refine and deepen our understanding of structure and function in marine systems. [ABSTRACT FROM AUTHOR]

The green macroalga Caulerpa filiformis has been spreading on shallow soft sediment habitats along the Peruvian coast, colonizing previously unvegetated sediments to create monospecific meadows. We examined the nature of the impact of C. filiformis meadows on the density, taxonomic richness and assemblage structure of epifaunal and infaunal benthic macroinvertebrates. Specifically, we tested whether the spread of C. filiformis has resulted in different macroinvertebrate assemblages than those formed by the dominant native macroalgae (i.e., Rhodymenia spp.) and unvegetated sediments. Surveys were undertaken in two bays in each of two locations, in central and southern Peru, during winter 2017 and summer 2018. In general, our results show that macroinvertebrate assemblages were similar across all three habitats, although there were some differences, related to location and time, but with no clear patterns observed. Taxonomic richness and density was generally higher in the vegetated habitats than the unvegetated habitat, and where there were differences between the two vegetated habitats there was no consistent pattern of which habitat supported the highest richness or density. Given invading C. filiformis is primarily colonizing unvegetated habitats it would appear that this species is creating a new niche which supports similar assemblages, but higher taxonomic richness and density than unvegetated habitats. While our study suggests that C. filiformis is having a limited ecological impact we recommend that actions be put in place to limit the spread of this invasive species at the same time as increasing monitoring of the ecological impacts of this species as lags in the ecological impacts of invasive species are common. [ABSTRACT FROM AUTHOR]

Elucidating factors ("drivers") that influence succession after disturbance can explain ecological phenomena, including why communities vary spatiotemporally. To gain insight on drivers related to habitat availability, species availability, and species performance during succession, we conducted two field experiments on infaunal communities in intertidal mudflats, one on each of the Atlantic and Pacific coasts of Canada, that had disturbances of different type, size, and frequency. Related to habitat availability drivers, we observed that disturbance type and size, which differed between experiments, did not change end patterns of succession; however, disturbance frequency, directly assessed in one experiment, did. Dispersal of species from surrounding mudflat and water column (species availability) was the primary driver of succession, whereas local interactions between species after colonization (species performance drivers) did not have a detectable effect. We suggested that ample space and resources diffused competition and predation effects, and so species replacements did not occur in our systems, resulting in a lack of "traditional" successional dynamics as observed in other ecosystems. Our findings that community composition in intertidal mudflats is strongly influenced by species availability on two different coasts suggest that this driver may be key to variation in intertidal mudflat communities elsewhere. [ABSTRACT FROM AUTHOR]

The rapid reorganization of global biodiversity has triggered an intense research effort to understand its consequences for ecosystem functioning. However, efforts to monitor biodiversity change and evaluate the outcomes for ecosystem states and processes are currently poorly aligned. While most monitoring programs evaluate ecosystem status by reporting measures of taxonomic diversity, it is not the number of species but rather the exhibited traits of these species that regulate function. Trait-based approaches assume that trait diversity and variability relate to changes in functions across environmental gradients, but this relationship remains to be explored for most marine benthic ecosystems. Using macrozoobenthic communities from the Dutch Wadden Sea as a model, we compiled information on traits related to animal-sediment relationships. This trait information was then combined with species’ abundance data from a 19 years-long database to calculate different taxonomic and functional metrics that reflect macrozoobenthic diversity, function, and community structure. Finally, we compared how these taxonomic and functional metrics change along with sediment texture gradients. Our analyses showed that the structure of macrozoobenthic communities and various diversity metrics all changed with sediment gradients. The observed changes in the communities’ species composition were associated with directional shifts in the relative presence of specific functional traits with increasing sediment grain size, from communities dominated by small body size, deposit-feeding, and short life span to communities characterized by large to medium body size, suspension-feeding, and long life span. We observed limited functional redundancy and high sensitivity of functional trait-based measures to changes in the community composition along sediment gradients. Our findings suggest that a trait-based approach provides valuable information about the ecological function of marine macrozoobenthic species complementary to traditional biodiversity measures (e.g., species richness, Simpson diversity, etc.). Hence, these measures may be used to characterize changes in ecosystem functioning in time and space using traditional monitoring datasets.

Abstract Elucidating factors (“drivers”) that influence succession after disturbance can explain ecological phenomena, including why communities vary spatiotemporally. To gain insight on drivers related to habitat availability, species availability, and species performance during succession, we conducted two field experiments on infaunal communities in intertidal mudflats, one on each of the Atlantic and Pacific coasts of Canada, that had disturbances of different type, size, and frequency. Related to habitat availability drivers, we observed that disturbance type and size, which differed between experiments, did not change end patterns of succession; however, disturbance frequency, directly assessed in one experiment, did. Dispersal of species from surrounding mudflat and water column (species availability) was the primary driver of succession, whereas local interactions between species after colonization (species performance drivers) did not have a detectable effect. We suggested that ample space and resources diffused competition and predation effects, and so species replacements did not occur in our systems, resulting in a lack of “traditional” successional dynamics as observed in other ecosystems. Our findings that community composition in intertidal mudflats is strongly influenced by species availability on two different coasts suggest that this driver may be key to variation in intertidal mudflat communities elsewhere.

Horse flies of the species Tabanus nigrovittatus and Tabanus acutus are native to coastal marshlands. Their larvae are apex invertebrate predators, and their development is dependent on the food web in the marsh sediment. Surveillance of T. nigrovittatus after the 2010 Deepwater Horizon Oil Spill in the Gulf of Mexico showed population crashes of adult flies in southeast Louisiana marshes near oil landfall, but not in southwest Louisiana where oil did not reach. Sediment collection in 2011 from Louisiana marshes showed a near‐complete absence of larvae in the southeast yet high numbers in the southwest. We hypothesized that oil contamination destroyed critical components of the larval food web and/or residual toxicity led to larval death. We used 18S rRNA gene metagenomics to identify components of the food web in larval guts and sediment from southeast and southwest Louisiana marshes. Sediment oil contamination, biochemistry, and toxicity could not explain the lack of larvae in the southeast, because oiling at our high‐tide mark sites was low at the time of the study and toxicity was independent of sediment biochemistry. Hexapods were the main food web components in tabanid larval guts. Abundance of stink bug, vinegar fly, and mosquito species in the sediment was positively associated with the presence of larvae. However, these taxa were enriched in southeastern (near oil) versus southwestern (unoiled reference) sediment, and thus, lack of major food web components due to oiling could not explain lack of larva in the east. We conclude that the immediate crash in adult populations in oiled regions was the main cause for the absence of larvae the following year. While most saltmarsh arthropod groups had rebounded within a year after the oil spill, recovery of saltmarsh horse flies was ongoing for 5 years. [ABSTRACT FROM AUTHOR]