Epibenthic Invertebrates Research Articles

Hierarchical modelling of epibenthic communities on the Scotian Shelf and Gulf of Maine (Atlantic Canada) in support of conservation planning

Identification of ecologically significant units at different spatial scales is essential for management of biodiversity attributes. This case study illustrates a coupled methodological approach to delineate benthic habitats and associated assemblages at different spatial scales. Two complementary analyses were employed based on the occurrences of 99 epibenthic invertebrate species in Atlantic Canada, sampled during depth-stratified random trawl sets. To identify epibenthic assemblage types, isometric feature mapping and partitioning around medoids (ISOPAM) was used in combination with a joint species distribution model (JSDM), which also produced continuous distribution surfaces across the spatial domain. ISOPAM identified nine significantly spatially coherent assemblages (biotopes) at spatial scales of hundreds of meters to hundreds of kilometers, with associated diagnostic species. Those assemblages were closely matched by eight regions of common profile using the JSDM, indicating strong environmental influences on their distributions. These smaller-scale assemblages were grouped into three biophysical units. The results from the JSDM were validated with independent data showing good congruence. This indicates that the spatial units ascribed to identified assemblages are robust and suitable for marine spatial planning and monitoring.

Local size structure and distribution of demersal fish in relation to sea pens and other benthic habitats in a deep-sea soft-bottom environment

Many fish species undergo ontogenetic habitat shifts as they grow to fulfill new biological, ecological and environmental requirements. While relationships between fishes and large hard-substrate cold-water corals (CWC) (e.g., Desmophyllum pertusum reefs) have frequently been studied, there are relatively fewer studies examining the relationships of fish with habitats specifically provided by smaller corals (e.g., sea pens) in soft-bottom environments. Despite this knowledge gap around soft-bottom corals, growing evidence of their importance has nonetheless justified their inclusion as conservation targets in numerous Marine Protected Areas (MPA), including the Canadian Laurentian Channel MPA. Here, we performed ROV and near-seabed drift-camera system surveys within the Laurentian Channel MPA in 2017 and 2018 to assess the influence of fish body size and habitat type on fish small-scale distribution in a low-relief deep-sea soft-sediment environment. We compared the local size structure of the four most abundant deep-sea demersal fish taxa of the channel (Redfish (Sebastes spp.), Witch Flounder (Glyptocephalus cynoglossus), Marlin-Spike Grenadier (Nezumia bairdii) and Longfin Hake (Phycis chesteri)) across one barren and five structural benthic habitats defined by the presence of nine dominant epibenthic invertebrates (actiniarians and CWCs). We used generalized additive models to identify biotic (benthic habitats) and abiotic (depth, bottom types) covariates of size for each taxon. We observed 15,381 fish within the 43.6-ha study area, of which 7,511 fish were measured. Juveniles represented 99% of all fish measured, with a notable increase in average fish size in 2018. While we did not find any associations between benthic habitats and fish life stages, the analysis revealed a significant increase in fish size within sea pen habitats for all four taxa. Conversely, we found a taxon-specific influence of bottom type on fish size for all taxa. In addition, Redfish and Longfin Hake size was positively correlated with depth. For deep-sea demersal fish taxa of the MPA, our results suggest that 1) sea pens provide nursery habitat for early-life stages, 2) fish undergo ontogenetic shifts in micro-habitat use and specialization, and 3) fish-habitat associations appear to be facultative rather than obligate. Through the use of in-situ video data, this study provided evidence that small and large fish do not use the same micro-habitats, and that sea pens contribute significantly to fish habitat despite providing less habitat heterogeneity than reef-forming scleractinians or large gorgonians. These results contribute to empirical understanding of fish-habitat relationships at different fish life stages and may inform fisheries management, as well as monitoring efforts in the MPA and other protected deep-sea environments.

Environmental DNA for monitoring the impact of offshore wind farms on fish and invertebrate community structures

AbstractTo reach the renewable energy targets set by the European Commission, a tenfold expansion of the installed offshore wind farms is needed. Since the construction of offshore wind farms may affect local soft‐sediment fauna, an efficient monitoring technique is needed to monitor the potential effects on the marine ecosystem. Here, we assess whether eDNA metabarcoding is a suitable alternative to monitor fish and epibenthos biodiversity in these difficult to access marine habitats. Water sampling and trawl surveys were conducted in parallel in 12 coastal and 18 offshore sites, the latter located inside and outside two offshore wind farms in the Belgian part of the North Sea. 12S eDNA metabarcoding retrieved 85.7% of the fish species caught in the beam trawls, whereas the COI eDNA metabarcoding only identified 31.4% of the epibenthic invertebrate species. Furthermore, the 12S marker resulted in an additional detection of 26 unique fish species, whereas the COI marker detected an additional 90 invertebrate species. Spatial patterns in alpha diversity recovered with eDNA metabarcoding were not significantly different from those observed with morphological determination. Significant differences were found in fish and invertebrate community structures between the coastal, transition and offshore zones as well as on the smaller wind farm scales, which agreed with the morphological beam trawl data. Indicator species found with morphological beam trawl monitoring for each of the three zones (coastal, transition, offshore) were also detected with 12S eDNA metabarcoding, and the latter method detected an additional 31 indicator species. Our findings show the need for adequate quality control of the obtained species lists and reveal that 12S eDNA metabarcoding analyses offers a useful survey tool for the monitoring of fish communities in offshore wind farms, but the used COI assay did not adequately capture the epibenthic communities as observed with beam trawl data.

Invertebrate diversity in groundwater-filled lava caves is influenced by both neutral- and niche-based processes.

Understanding which factors shape and maintain biodiversity is essential to understand how ecosystems respond to crises. Biodiversity observed in ecological communities is a result of the interaction of various factors which can be classified as either neutral- or niche-based. The importance of these processes has been debated, but many scientists believe that both processes are important. Here, we use unique ecosystems in groundwater-filled lava caves near Lake Mývatn, to examine the importance of neutral- versus niche-based factors for shaping invertebrate communities. We studied diversity in benthic and epibenthic invertebrate communities and related them to ecological variables. We hypothesized that if neutral processes are the main drivers of community structure we would not see any clear relationship between the structure of community within caves and ecological factors. If niche-based processes are important we should see clear relationships between community structure and variation in ecological variables across caves. Both communities were species poor, with low densities of invertebrates, showing the resource limited and oligotrophic nature of these systems. Unusually for Icelandic freshwater ecosystems, the benthic communities were not dominated by Chironomidae (Diptera) larvae, but rather by crustaceans, mainly Cladocera. The epibenthic communities were not shaped by environmental variables, suggesting that they may have been structured primarily by neutral processes. The benthic communities were shaped by the availability of energy, and to some extent pH, suggesting that niche-based processes were important drivers of community structure, although neutral processes may still be relevant. The results suggest that both processes are important for invertebrate communities in freshwater, and research should focus on understanding both of these processes. The ponds we studied are representative of a number of freshwater ecosystems that are extremely vulnerable for human disturbance, making it even more important to understand how their biodiversity is shaped and maintained.

Assessing the effect of onshore and offshore Wave Energy Converters on seafloor integrity combining image-based and acoustic methods

The European Atlantic Ocean offers great opportunities for the development of projects for renewable energy extraction, and the Marine Renewable Energy sector is developing different technologies for energy converters, including Wave Energy Converters. Besides, the European Commission is adopting measures and politics to increase the installed capacity of ocean energy. However, there are still uncertainties on the potential environmental effects of wave energy converters, which led regulators and stakeholders to perceive their operation as a risky activity. To overcome the non-technological barriers that could hinder the development of marine renewable energies, and improve the knowledge on the impacts on the seafloor integrity (among others), SafeWAVE project set an Environmental Research Demonstration Strategy based on the collection, processing, modelling, analysis and sharing of environmental data collected in Aguçadoura (Portugal), Armintza (Spain) and Le Croisic (France) representing different types of technology, locations and project scales. Video recordings were carried out, using Remotely Operated Vehicles, to identify the environmental impacts of the moorings on the seafloor morphology. That information was completed by side scan sonar campaigns using an Autonomous Underwater Vehicle. The video recordings were useful also to assess the attraction effect of the moorings to epibenthic invertebrates and fishes, whereas the side scan sonar provided quantitative information on the area affected by physical alteration (<1% of the total area occupied by the devices at Armintza and Le Croisic).

Potential risk to aquatic biota from aerial application of firefighting water additives

The frequency and severity of forest fires is increasing due to climate change. Consequently, there will be an increased use of forest firefighting additives, which increase the ability of water to extinguish fires and prevent reignition. Increased use will potentially result in increased exposure to aquatic ecosystems within forests. This study examined the toxicity of nine firefighting water additives that are currently on the market to three species of freshwater invertebrates that occupy different niches within freshwater ecosystems. The toxicity of the water additives varied up to three orders of magnitude. Pelagic and epibenthic invertebrates are affected at lower rates of application than endobenthic invertebrates. A field relevant application rate of three of the nine water additives tested represent a hazard to freshwater ecosystems under varies exposure scenarios represented by the depth of a theoretical water body (15–200 cm). This study highlights the importance of application buffers around water bodies and the selection of water additives that pose the lowest hazard to freshwater ecosystem, assuming that the efficacy of the additives in extinguishing fires is similar.

Winners and losers in a warming Arctic: Potential habitat gain and loss for epibenthic invertebrates of the Chukchi and Bering Seas, 2008–2100

Our goal was to examine how the epibenthic invertebrate community in the Pacific Arctic Region might be affected by continued increases in ocean temperatures. We used epibenthic invertebrate catch and bottom temperature data collected on groundfish assessment and ecosystem surveys in the Bering and Chukchi seas from 2009 to 2018 to determine the “preferred” temperature of all taxa. We grouped taxa into five clusters according to their similarity in median temperature and temperature range. We then used an ensemble of eight climate models under Representative Concentration Pathway 8.5 (RCP8.5) scenarios to project bottom temperature from present (2008) to mid-century (2050) and end of the century (2100). Based on these projections, we show how the amount and distribution of cluster-specific thermal habitat might change with ocean warming. We found that by mid-century there was a 50% decrease in thermal habitat for all clusters except for the most eurythermic cluster, and that thermal habitat contracted to the north. By the end of the century there was very little thermal habitat for all clusters, except the most eurythermic cluster, and habitat was further contracted to the north. The cold-water and stenothermic cluster, hypothesized to be the most vulnerable to ocean warming, had virtually no projected thermal habitat by the end of the century. These “losers” were primarily gastropods and the bivalve mussel Musculus sp. These taxa are some of the primary prey to the endangered Pacific walrus (Odobenus rosmarus), which is harvested as a food resource in native Alaskan communities. Bivalves are prey for commercial flatfish such as yellowfin sole (Limanda aspera) and Alaska plaice (Pleuronectes quadrituberculatus). By 2100 the most eurythermic cluster, hypothesized to be the least vulnerable to warming, had projected suitable thermal habitat throughout most of the Bering and Chukchi seas, except nearshore coastal regions. The most abundant species of these “winners” was the basketstar Gorgonocephalus cf. arcticus. The loss of thermal habitat for all but the “winners” could impact the species diversity of the Bering and Chukchi seas because the “winner” cluster accounted for only 26 taxa or 8% of all taxa observed. Although temperature is a key determinant of habitat, a full habitat and ecosystem model is needed to provide more detailed predictions. In addition, more laboratory studies of thermal acclimation potential of Arctic benthic invertebrates are needed. Our results provide the first indications that the epibenthic invertebrate community in the Bering and Chukchi seas, which supports marine mammals, seabirds and human communities, may be seriously impacted by future ocean warming.

I’m not that Shallow – Different Zooplankton Abundance but Similar Community Composition Between Habitats in the San Francisco Estuary

Wetland restoration is a key management tool for increasing food availability for at-risk fishes in the San Francisco Estuary. To characterize the benefits of restoration sites, it is critical to quantify the abundance and composition of fish food resources in and near the wetlands. Characterization of zooplankton communities is considered particularly important, but accurate analysis of zooplankton samples is time-consuming and expensive. The recently established Fish Restoration Program (FRP) Monitoring Team assessed whether data from existing long-term monitoring surveys could be used to characterize shallow-water zooplankton communities before restoration. During the springs of 2017 to 2019, the FRP collected zooplankton samples near the mouth of tidal wetland sites, or immediately outside future restoration sites, and compared them to concurrent samples collected in deep water by existing long-term monitoring surveys. We found very few differences in community composition between shallow and deep samples, though a few taxa were more abundant in shallow water. Seasonal and interannual differences in composition and abundance showed that restoration sites provide varying food resources over time. There was significantly higher total abundance of zooplankton in deep versus shallow water, which may be a result of differences in zooplankton production, migration, or fish predation. Inconsistencies in towing speed and gear type may also be driving this result, rather than true habitat differences. This study indicates that monitoring of wetland restoration sites must rely on multiple years of data collected on the site—rather than relying on adjacent open-water sampling—and should include monitoring of epiphytic and epibenthic invertebrates as well as zooplankton.

The effect of small-scale habitat features on groundfish density in deep-sea soft-bottom ecosystems

In the deep-sea, cold-water corals (CWCs) and other structure-forming fauna locally increase habitat complexity and are host to many fish species. While many studies have focused on hard-bottom CWCs, very little is known about fish associations with soft-bottom CWC habitats. To understand the small-scale linkages between fish, benthic and non-bio-structural habitats in a soft-sediment deep-sea environment, we analysed remotely operated vehicle (ROV) survey videos and recorded the occurrence of fish, invertebrate habitat-forming species and substratum along transects, in the Laurentian Channel Marine Protected Area (MPA) in the Canadian Northwest Atlantic. Almost 13,300 individual fish were recorded, of which all but 65 specimens were identified to family or lower taxonomic rank. The five numerically dominant fish taxa were Redfish (Sebastes spp.), Witch Flounder (Glyptocephalus cynoglossus), Marlin-Spike Grenadier (Nezumia bairdii), Longfin Hake (Phycis chesteri) and one Teleostei morphotype. Teleostei sp1 represents three fish genera (Sandlance (Ammodytes spp.) and two Barracudinas (Arctozenus sp. and Paralepis spp.)) morphologically difficult to differentiate on video footage. Multivariate analysis revealed four habitats based on epibenthic invertebrate densities and diversity. These were dominated by various combinations of sea anemones (Actiniaria), nephtheid soft coral, solitary cup corals (Scleractinia) and three taxa of sea pen (Pennatula spp., Kophobelemnon sp. and Anthoptilum spp.). Univariate analyses performed on dominant fish densities revealed the local influence of hard-bottom substrates and the common influence of soft-sediment micro-features for three fish taxa. All fish densities were correlated with invertebrate density, negatively for Redfish and positively for all other taxa. Our models also predicted the association of four fish taxa with one to two benthic habitats within their preferred depth range. Our results suggest that small-scale habitat heterogeneity in a low relief soft-sediment environment, provided by both physical and biological structures, has a measurable species-specific influence on fish communities. This influence was weaker than typical fish-habitat relationships found in hard-bottom systems, suggesting fish-invertebrate relationships are not obligate. Additionally, we provided evidence that Redfish continue occupying sea pen habitats months after spawning. Our study supports the necessity to continue monitoring the MPA using in-situ video systems to understand the links between fish and habitats in the Laurentian Channel.

How much city is too much city? Biodiversity and ecosystem functioning along an urban gradient at the interface of land and sea

A huge proportion of the world’s population resides in urban areas along the coast. As cities expand, the ability of coastal ecosystems to provide the benefits people derive from nature, ranging from food from fisheries to coastal defense to maritime transportation and beyond, is in question. While it is well understood that coastal development changes ecosystems, quantitative insights about how terrestrial urbanization fundamentally alters ecosystem structure and function in adjacent freshwater and downstream coastal marine habitats remain rare, though a general expectation is that impacts of terrestrial urbanization will attenuate from land to freshwater to coastal marine habitats. Empirical assessments of these phenomena are especially important for species that rely on freshwater and coastal marine habitats at multiple points in their life cycles, including endangered and threatened Pacific salmon (Oncorhynchus spp.). We investigated associations between landscape-scale urbanization and ecosystem structure (biodiversity of epibenthic invertebrate taxa) and function (benthic net primary productivity and decomposition) in freshwater and coastal marine habitats across six pairs of more and less urbanized, coastal watersheds in Puget Sound, WA, USA, using principal components analysis, analysis of covariance, and Mantel tests. Greater upland urbanization was associated with greater reductions in freshwater biodiversity, measured as the density and evenness of epibenthic invertebrate families. In contrast and surprisingly, however, coastal marine biodiversity (measured as the density and evenness of epibenthic invertebrate families) tended to be higher at more urbanized sites, suggesting the potential role of low to moderate levels of urbanization-related disturbance in determining coastal marine biodiversity patterns. We found no statistical association between urbanization and freshwater and coastal marine ecosystem functions, estimated from changes in accumulated algal biomass on tiles (benthic net primary productivity) and loss of biomass from litter bags (decomposition). In addition, there was no evidence that changes in ecosystem structure and function with urbanization were more severe in freshwater than coastal marine habitats, as might be expected if the land-sea boundary diminished effects of landscape-scale urbanization. Our results suggest that the effects of urbanization can be complex and that attention to terrestrial, freshwater, and coastal marine systems in concert will produce more effective, ecosystem-based management.

Invertebrate metal accumulation and toxicity from sediments affected by the Mount Polley mine disaster.

On August 4, 2014, a tailings dam failed at the Mount Polley copper and gold mine near Likely, British Columbia, Canada, releasing approximately 25 M m[Formula: see text] of contaminated water and solid tailings material into Polley and Quesnel lakes. Water, sediment, freshwater scuds (Hyalella azteca), and mayfly larvae (Ephemeroptera) were collected during the summer of 2018 from Polley Lake, affected and unaffected sites in Quesnel Lake, and both mine-contaminated and clean far-field sites as references. Analytical results indicated that invertebrates from sites affected by the tailings breach had elevated metal concentrations relative to those from non-affected or reference sites. We conducted a controlled laboratory exposure to determine if laboratory-reared Hyalella azteca metal concentrations were related to field-collected water or sediments from the same sites as the field study. Half of the replicates prevented amphipods from directly contacting sediments (water-only exposure), while the other half allowed them direct access (sediment and water exposure). Whole-body Cu concentration was highest in Hyalella exposed to substrate from the most contaminated sites as well as in treatments where they were allowed direct access to sediments. Hyalella having direct access to metal-contaminated sediments showed reduced survival and growth relative to those in reference or control treatments. These results suggest that metals from the fine sediments associated with the Mount Polley mine disaster are bioavailable and potentially toxic to epibenthic invertebrates, even several years after the initial breach.

Natural history collections recapitulate 200 years of faunal change.

Changing species assemblages represent major challenges to ecosystems around the world. Retracing these changes is limited by our knowledge of past biodiversity. Natural history collections represent archives of biodiversity and are therefore an unparalleled source to study biodiversity changes. In the present study, we tested the value of natural history collections for reconstructing changes in the abundance and presence of species over time. In total, we scrutinized 17 080 quality-checked records for 242 epibenthic invertebrate species from the North and Baltic Seas collected throughout the last 200 years. Our approaches identified eight previously reported species introductions, 10 range expansions, six of which are new to science, as well as the long-term decline of 51 marine invertebrate species. The cross-validation of our results with published accounts of endangered species and neozoa of the area confirmed the results for two of the approaches for 49 to 55% of the identified species, and contradicted our results for 9 to 10%. The results based on relative record trends were less validated. We conclude that, with the proper approaches, natural history collections are an unmatched resource for recovering early species introductions and declines.

Small invertebrates in bivalve-cultivated and unmodified habitats of nearshore ecosystems

Many nearshore ecosystems are modified by aquaculture, including bivalve culture to produce food and restore extirpated populations. Small invertebrates in nearshore ecosystems support fundamental ecological processes, but the effects of bivalve culture on invertebrates are incompletely understood. Here, we compared invertebrate assemblages from multiple studies of bivalve-cultivated and unmodified nearshore habitats along the US west coast. In general, unmodified eelgrass and nearby off-bottom culture habitats with eelgrass present were inhabited by a greater abundance, richness, and diversity of epibenthic invertebrates than bottom culture and bare (mud, sand) habitats that both lacked eelgrass. Findings of individual studies suggested: minor differences in epibenthic invertebrate assemblages associated with various aquaculture practices; restoring native oysters to mudflats did not detectably alter epibenthic invertebrate abundances; epibenthic invertebrates were more abundant on shell hash introduced to mudflats than unmodified mudflats; and benthic invertebrates were less abundant, rich, and diverse in habitats cultured on bottom by Manila clams. Considering the range of these patterns, there appears to be potential for coastal communities to restore extirpated bivalve populations or develop bivalve culture practices that meet objectives to grow food while maintaining nearshore ecosystems’ fundamental processes supported by robust invertebrate assemblages.

Using biological traits to get insights into the bentho-demersal community sensitivity to trawling in the Celtic Sea

Abstract Coastal marine ecosystems are under many pressures, including bottom trawling, which is the most widespread human activity that directly affects seabed habitats. Therefore, it is of great importance to characterize the impacts of bottom trawling on bentho-demersal communities, which can be done through the study of indicators sensitive to trawling pressure. Using a functional indicator applied to 54 underwater video transects, we mapped the sensitivity to trawling of epibenthic invertebrates and fish communities in the Celtic Sea. We determined the relative influence of environmental and fishing variables on sensitivity and traits distribution. Our results suggest that community sensitivity to trawling is mainly driven by a spatial gradient of depth and primary productivity that separates the area into two main regions: a shallow, productive area, with low sensitivity and a higher abundance of swimming and crawling organisms, and a deeper, less productive area, with higher sensitivity due to a higher abundance of fixed, filter-feeding organisms. Fishing intensity also drives the sensitivity of communities confirming that they have already been shaped by a long history of mixed fisheries. The methodology used here provides a valuable monitoring tool and could be used to predict communities’ response to changes in fishing intensity and climate change.

Seasonal dispersal of gammaridean amphipods away from Sargassum beds in relation to macroalgal host defoliation

Epibenthic invertebrate assemblages in macroalgal beds generally show remarkable seasonal fluctuations in abundance and species composition, reflecting macroalgal host growth and defoliation. Notably, they often drastically decrease during macroalgal host defoliation. Though this reduction has been explained in terms of dispersal away from the macroalgal bed in relation to macroalgal host defoliation, this hypothesis has not previously been experimentally detailed. We conducted a field experiment using an imitation of Sargassum that was set 1 m away from a Sargassum yezoense bed to examine whether the epibenthic gammarids disperse away from the Sargassum bed as a result of Sargassum defoliation. The imitations were replaced monthly throughout the Sargassum defoliation season; subsequently, gammarids associated with the imitation (assumed as migrants from the Sargassum beds) as well as the gammarids that occurred in the Sargassum bed were investigated. Seasonal patterns of gammarid abundance in the Sargassum bed and their dispersal to the imitations were found to be quite different among gammarid species. In particular, 2 dominant gammarids, the suspension-feeding Jassa morinoi and Podocerus sp., drastically decreased in the Sargassum bed and coincidently increased in the imitations during the Sargassum defoliation season, indicating their defoliation-associated dispersal from the Sargassum bed. This is the first field experimental study demonstrating the defoliation-associated dispersal of epibenthic invertebrates in macroalgal beds. The dispersal is likely caused by a reduction of habitat space and quality due to thalli defoliation. Since many macroalgae show seasonal growth and defoliation, the concept of defoliation-associated dispersal is potentially applicable to various macroalgal species.

Effects of age, maturity stage, sex and seasonality on the feeding strategies of the diamond stingray (Hypanus dipterurus) in the southern Gulf of California

The diet of the diamond stingray (Hypanus dipterurus) was quantified based on individuals collected monthly from October 2013 to December 2015 on Espiritu Santo Island in the Bahía de La Paz, México. Of the 473 stomachs analysed, 211 (44.6%) contained food. Analysis of the prey-specific index of relative importance indicated that the diet of H. dipterurus was based on infaunal and epibenthic invertebrates, especially the bivalve Solemya spp. (42.2%) and the stomatopod Nannosquilla raymanningi (7.7%). Statistical analyses of the diet considering sex, age, maturity stage and interactions between sex, age and season indicated that older females consumed more polychaetes in the cold (November–April) season and that younger females consumed more stomatopods and bivalves in the warm (May–October) season. The feeding strategy of the species is specialised on three prey categories (bivalves, polychaetes and stomatopods), with low trophic niche breadth values. The calculated trophic level indicated that the diamond stingray is a secondary consumer and mesopredator. We conclude that the diamond stingray does not maintain a redundant trophic function with sympatric elasmobranchs in the study area, and is therefore likely a key prey density-regulator functioning to link energy derived from lower to upper trophic levels within the southern Gulf of California.

Marine epibenthic functional diversity on Flemish Cap (north‐west Atlantic)—Identifying trait responses to the environment and mapping ecosystem functions

AbstractAimTo characterize the functional diversity and selected ecological functions of marine epibenthic invertebrate communities at the ecosystem scale and to evaluate the relative contributions of environmental filtering, including bottom‐contact fishing, and competitive interactions to benthic community assembly.LocationFlemish Cap, an ecosystem production unit and fishing bank in the high seas of the north‐west Atlantic Ocean.MethodsThrough the use of Hierarchical Modelling of Species Communities (HMSC), we have explored seven community response traits to the environment applied to 105 epibenthic species and evaluated the influence of such traits on the community assembly processes. Assumed bioturbation, nutrient cycling and habitat provision functions, linked to individual or a combination of biological traits, were mapped using random forest modelling.ResultsFunctional richness within benthic communities reached an asymptote for trawl sets with roughly more than 30 species. Assemblages on top of the Flemish Cap (<500 m depth) were characterized by higher biomass of small‐ and medium‐sized species with short life spans, whereas large species with longer life spans and broadcast spawners were dominant in the deeper assemblages (500–1,500 m depth). The amount of variation explained by the species’ responses to the covariates mediated by the traits was relatively high (25%) indicating their relevance to community assembly. Community‐weighted mean trait values changed with depth and physical oceanographic variables, indicating that environmental filtering was occurring. Interspecific interactions, as inferred from the random effect at the sample level, accounted for 16.3% of the variance in the model, while fishing effort explained only 5.2% of the variance but conferred strong negative impacts for most species.Main conclusionsOur results suggest that while bottom‐contact fishing impacts have an effect on functional diversity, changes to the physical oceanography of the system are likely to have more profound impacts. The maps of benthic functioning can aid assessments of ecosystem impacts of fishing.

Effect of algal phenology on seasonal dynamics of gammarid assemblages: differences between canopy and understory strata in a Sargassum yezoense bed

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 634:63-76 (2020) - DOI: https://doi.org/10.3354/meps13194 Effect of algal phenology on seasonal dynamics of gammarid assemblages: differences between canopy and understory strata in a Sargassum yezoense bed Masafumi Kodama1,*, Tomohiko Kawamura1, Kenta Nakamoto1, Naoya Ohtsuchi1, Jun Hayakawa1, Takayuki Kanki1, Takashi Kitagawa1, Yoshiro Watanabe2 1International Coastal Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo, Akahama, Otsuchi, Iwate 028-1102, Japan 2Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8564, Japan *Corresponding author: mkodama@aori.u-tokyo.ac.jp ABSTRACT: Macroalgal beds can be vertically differentiated into canopy and understory strata, and each can exhibit different phenology in algal biomass and morphology. Thus, for epibenthic invertebrates, macroalgal beds provide both vertically and seasonally heterogenous habitats, and epibenthic assemblages can be predicted to show different patterns of seasonal dynamics reflecting the different effects of algal phenology between the canopy and understory. We described and compared the seasonal dynamics of gammarid assemblages and algal phenology in the canopy and understory of a Sargassum bed in Otsuchi Bay, Japan. Gammarid assemblages showed distinctly different seasonal dynamics in abundance and species composition between the 2 habitats. In the canopy, gammarid abundance peaked in July, which was mainly explained by fluctuations in abundance of the dominant tube-dwelling filter-feeder Jassa morinoi. In the understory, gammarid abundance peaked in August-September, clearly later than in the canopy, and was also dominated by tube-dwelling filter-feeders, but different species such as Monocorophium uenoi and Gammaropsis japonicus. These differences in assemblage dynamics of gammarids can be explained by the Sargassum defoliation in late summer, resulting in decreased habitat space and complexity for gammarids in the canopy. In the understory, however, Sargassum defoliation increased the amount of detrital deposition, providing food sources and additional habitat for gammarids. This study demonstrates that algal phenology can have strong but different effects on epibenthic invertebrates inhabiting canopy and understory strata. KEY WORDS: Gammarid · Sargassum beds · Assemblage dynamics · Algal phenology · Habitat heterogeneity · Canopy · Understory Full text in pdf format Supplementary material PreviousNextCite this article as: Kodama M, Kawamura T, Nakamoto K, Ohtsuchi N and others (2020) Effect of algal phenology on seasonal dynamics of gammarid assemblages: differences between canopy and understory strata in a Sargassum yezoense bed. Mar Ecol Prog Ser 634:63-76. https://doi.org/10.3354/meps13194 Export citation Mail this link - Contents Mailing Lists - RSS Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 634. Online publication date: January 23, 2020 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2020 Inter-Research.

Multiple factors contribute to the spatially variable and dramatic decline of an invasive snail in an estuary where it was long-established and phenomenally abundant

Boom-bust dynamics of invasive species have long intrigued scientists and managers alike, but quantification of such dynamics, let alone their causes, is rare. We documented the decline of a previously prolific invasive mudsnail, Batillaria attramentaria, at Elkhorn Slough estuary in central California, USA. The mudsnail was the most abundant epibenthic invertebrate in the estuary, maintaining very high densities for many decades before declining heterogeneously throughout the estuary over the past decade, decreasing in density by three orders of magnitude at some sites. We used field and laboratory experiments to test several possible mechanisms for its demise. We show that the crab Pachygrapsus crassipes can prey heavily on Batillaria. We detected high dissolution rates of Batillaria shells, and we measured greater predation rates on tethered snails with dissolved versus intact shells. Warm water temperatures and high water levels coincided with the period of most dramatic Batillaria declines (2013–2015). Localized water impoundments appear to buffer environmental drivers of the decline because Batillaria remained abundant at sites with artificial tidal restriction, while the population crashed at one site after full tidal exchange was restored. We also investigated trematode parasite prevalence and molluscicide applications to the surrounding watershed as possible causes of mudsnail declines, but they had little explanatory power. Our findings illustrate the potential for population crashes even for long-established introduced species at pest levels of abundance, and demonstrate that such declines can exhibit spatial heterogeneity. Both of these results highlight the value of investigating population dynamics of invaders across multiple temporal and spatial scales.

Secondary contacts and genetic admixture shape colonization by an amphiatlantic epibenthic invertebrate.

Research on the genetics of invasive species often focuses on patterns of genetic diversity and population structure within the introduced range. However, a growing body of literature is demonstrating the need to study how native genotypes affect both ecological and evolutionary mechanisms within the introduced range. Here, we used genotyping‐by‐sequencing to study both native and introduced ranges of the amphiatlantic marine invertebrate Ciona intestinalis. A previous study using microsatellites analysed samples collected along the Swedish west coast and showed the presence of genetically distinct lineages in deep and shallow waters. Using 1,653 single nucleotide polymorphisms (SNPs) from newly collected samples (285 individuals), we first confirmed the presence of this depth‐defined genomic divergence along the Swedish coast. We then used approximate Bayesian computation to infer the historical relationship among sites from the North Sea, the English Channel and the northwest Atlantic and found evidence of ancestral divergence between individuals from deep waters off Sweden and individuals from the English Channel. This divergence was followed by a secondary contact that led to a genetic admixture between the ancestral populations (i.e., deep Sweden and English Channel), which originated the genotypes found in shallow Sweden. We then revealed that the colonization of C. intestinalis in the northwest Atlantic was as a result of an admixture between shallow Sweden and the English Channel genotypes across the introduced range. Our results showed the presence of both past and recent genetic admixture events that together may have promoted the successful colonizations of C. intestinalis. Our study suggests that secondary contacts potentially reshape the evolutionary trajectories of invasive species through the promotion of intraspecific hybridization and by altering both colonization patterns and their ecological effects in the introduced range.