Ecological impacts of the expansion of offshore wind farms on trophic level species of marine food chain

The global demand for renewable energy has resulted in a rapid expansion of offshore wind farms (OWFs) and increased attention to the ecological impacts of OWFs on the marine ecosystem. Previous reviews mainly focused on the OWFs' impacts on individual species like birds, bats, or mammals. This review collected numerous field-measured data and simulated results to summarize the ecological impacts on phytoplankton, zooplankton, zoobenthos, fishes, and mammals from each trophic level and also analyze their interactions in the marine food chain. Phytoplankton and zooplankton are positively or adversely affected by the 'wave effect', 'shading effect', oxygen depletion and predation pressure, leading to a ± 10% fluctuation of primary production. Although zoobenthos are threatened transiently by habitat destruction with a reduction of around 60% in biomass in the construction stage, their abundance exhibited an over 90% increase, dominated by sessile species, due to the 'reef effect' in the operation stage. Marine fishes and mammals are to endure the interferences of noise and electromagnetic, but they are also aggregated around OWFs by the 'reef effect' and 'reserve effect'. Furthermore, the complexity of marine ecosystem would increase with a promotion of the total system biomass by 40% through trophic cascade effects strengthen and resource partitioning alternation triggered by the proliferation of filter-feeders. The suitable site selection, long-term monitoring, and life-cycle-assessment of ecological impacts of OWFs that are lacking in current literature have been described in this review, as well as the carbon emission and deposition.

Arctic puzzle: Pioneering a northern shrimp (Pandalus borealis) habitat model in Disko Bay, West Greenland

Recent advancements in spatial modelling leverage remote sensing data and statistical species-environment relationships to forecast the distribution of a specific species. Our study focuses on Disko Bay in West Greenland, recognized as a significant marine biodiversity hotspot in the region. We conducted comprehensive analyses using multiple datasets spanning from 2010 to 2019, incorporating shrimp and fish surveys, commercial shrimp fishery catches, high-resolution (25 × 25 m) multibeam bathymetry and backscatter data along with a medium-resolution (200 × 200 m) bathymetric model, measured and modelled oceanographic data, and satellite chlorophyll data. Through multivariate regression analysis, we tested the significance of various physical factors (seafloor depth, sediment class, bottom water temperature, bottom water salinity, bottom current velocity, space, and time), biological factors (chlorophyll a, Greenland halibut (Reinhardtius hippoglossoides)), and anthropogenic impact (shrimp fishery; standardized catch per unit effort) on the density of northern shrimp in the area. Our results indicate a significant association between northern shrimp density, seafloor depth, and sediment class, explaining 36 % of the variation in shrimp density. Subsequently, we developed a high-resolution (optimized) spatial linear mixed-effect model to map the distribution of northern shrimp across Disko Bay, representing the first model of its kind developed for an Arctic area. The optimal habitat for northern shrimp is characterized by medium-deep waters (approximately 150-350 m), turbulent conditions, and mixed sediments, predominantly located in the northern and southern regions of Disko Bay. Notably, the northern region hosts a relatively diverse benthic community, with northern shrimp and sponges as the primary contributors of epibenthic biomass. This novel high-resolution model significantly enhances our understanding of the physical drivers and detailed spatial patterns influencing the distribution of northern shrimp in the Arctic.

Harpacticoid copepods expand the scope and provide family-level indicators of the Deepwater Horizon oil spill deep-sea impacts

The Deepwater Horizon (DWH) blowout and oil spill began on April 20, 2010 in the northern Gulf of Mexico (NGOM) deep sea (1525 m). Previous studies documented an impacted area of deep-sea floor totaling 321 km2 and were based on taxonomy at the macrofauna family level and the meiofauna major taxonomic level. In the present study, finer taxonomic resolution of the meiofauna community was employed, specifically harpacticoid copepod family biodiversity. Severe or moderate impacts to harpacticoid family biodiversity were observed at 35 of 95 sampling stations, covering an estimated area of 2864 km2, 8.9 times greater impacted area than previously reported. Sensitive and tolerant harpacticoid families were observed in the impact zone. The present study greatly expands the understanding of DWH deep-sea impacts in 2010 and demonstrates that the harpacticoid family-level response is the most sensitive indicator (reported to date) of this oil spill pollution event.

Effects of bottom trawling and environmental factors on benthic bacteria, meiofauna and macrofauna communities and benthic ecosystem processes

Soft sediment marine benthic ecosystems comprise a diverse community of bacteria, meiofauna and macrofauna, which together support a range of ecosystem processes such as biogeochemical cycling. These ecosystems are also fishing grounds for demersal species that are often caught using bottom trawling. This fishing method can have deleterious effects on benthic communities by causing injury or mortality, and through alteration of sediment properties that in turn influence community structure. Although the impacts of bottom trawling on macrofauna are relatively well studied, less is known about the responses of meiofauna and bacteria to such disturbances, or how bottom trawling impacts benthic ecosystem processes. Quantifying trawling impacts against a background of natural environmental variability is also a challenge. To address these questions, we examined effects of bottom trawling and a range of environmental variables (e.g. water chemistry and physical and biochemical surface sediment properties) on a) bacterial, meiofaunal and macrofaunal community structure and b) benthic ecosystem processes (nutrient fluxes, extracellular enzyme activities and carbon turnover and degradation rates). We also investigated the link between the benthic macrofauna community and the same ecosystem processes. While there was a significant effect of bottom trawling intensity on macrofaunal community structure, the same was not seen for bacterial or meiofaunal community composition, which were more affected by environmental factors, such as surface sediment properties. The labile component of the surface sediment carbon pool was higher at highly trawled sites. Carbon degradation rates, extracellular enzyme activities, oxygen fluxes and some nutrient fluxes were significantly affected by trawling, but ecosystem processes were also strongly linked to the abundance of key bioturbators (Macoma balthica, Halicryptus spinulosus, Scoloplos armiger and Pontoporeia femorata). Although benthic ecosystems were affected by a combination of trawling and natural variability, disentangling these showed that the anthropogenic effects were clearest on the larger component of the community, i.e. macrofauna composition, and on ecosystem processes related to sedimentary carbon.

Changes in coastal ecosystems affected by overburden dumping from amber open-cut mining on the Sambia Peninsula (Baltic Sea)

The Sambia Peninsula (Kaliningrad region) is historically well known for its amber mining. The 2019 year was the last year of direct overburden disposal into the Baltic Sea as a part of technological amber mining process. The extremely high-suspended particulate matter concentrations during that disposal were recorded immediately after the discharge of significant volumes of pulp and reached 200 mg/L. The impact of pulp discharge had sequentially suppressed plankton communities development due to the high content of suspended solids and afterwards stimulated plankton development due to the glauconite infusion. Cladocera were the most sensitive group to the effects of suspended matter. According to the preliminary forecast, when the pulp discharge stops, the restoration of plankton communities may take from 1 to 2 seasons to 1 year for different groups. This is due to the timing of the removal of fine suspended particulate matter from sediments and the possibility of secondary entry during resuspension.

The role of habitat heterogeneity and timescales on the recovery of reef epifaunal communities affected by a massive oil spill in the tropics

From August 2019 to January 2020 the Brazilian Coast was impacted by the largest oil spill in the Tropical oceans ever since. Paiva Beach, one of the most preserved sandy beaches in the northeast tropical Brazilian coast, was among the most affected regions by the oil spill in October 2019. This area has important reef systems that harbor abundant macroalgal assemblages with very diverse epifaunal communities. The present study aims to evaluate the impacts of the 2019 oil spill on epifauna associated with the seaweed species Jania capillacea and Penicillus capitatus collected in Paiva Beach from July 2019 to October 2022, and use the interaction macroalgae/epifauna/timescale as a proxy to quantify the effects of oil spills on communities structure and recovery. The epifauna of both algae did not suffer severe changes in abundance immediately after the spill, however, the abundance of taxa like echinoderms, sea spiders (Pycnogonida) and peracarid crustaceans dropped during or soon after the event, whereas others, like sabellid worms, had strong increase in abundance, possibly related to the spill. Both phytal assemblages also had distinct temporal patterns in species diversity and abundance, the last being strongly correlated to amphipod abundance for some taxa. The epifauna of J. capillacea had a short-term tendency of decrease in taxonomic diversity, whereas the epifaunal communities of P. capitatus gained a few taxa in the months immediately after the disaster. The diversity profiles of both communities returned to pre-spill conditions a few months later, with a slower abundance recovery in J. capillacea. Local environmental characteristics like landscape heterogeneity, connectivity with other environments, and critical-species (mainly amphipods) were possibly the main buffering factors for the phytal communities after the oil spill.

Ecological interruption on food web dynamics by eutrophic water discharge from the world's longest dike at Saemangeum, Yellow Sea

The man-made sea dike has disrupted the natural link between riverine and marine ecosystems and caused eutrophication within the aquatic ecosystem. The eutrophic water discharge has also raised concerns. As a representative tidal flat with the longest dike in the world, Saemangeum has experienced the problem of eutrophication. To elucidate the discharge water effects on the benthic food web dynamics, a four-year round sampling was conducted in/outside of the Saemangeum sea dike. Stable isotope analysis was applied to benthos (a total of 54 species) and their potential diets. Water discharge tripled in period II (2021-2022) compared to the period I (2019-2020). However, there were no significant impact changes in food web structure between the two periods due to improved lake water quality in period II. A positive correlation of nutrient concentration between the inner and outer areas of the dike revealed a direct effect of the water discharge on the outer tidal flat. The water discharge altered the spatial environmental conditions and the food web structure of the outer tidal flat. High TN concentrations stimulated the biomass of microphytobenthos (MPB) near the water gates, which in turn increased MPB consumption by benthos, demonstrating the in/direct impacts of water discharge on the food web. Furthermore, filter feeders exhibited a more sensitive response to spatial organic matter distribution compared to deposit feeders in diet utilization. Overall, our novel findings on food web dynamics in a representative tidal flat with artificial structures emphasize the necessity of continuous monitoring to ensure the sustainability of coastal ecosystems.

Adding Corbicula fluminea altered the effect of plant species diversity on greenhouse gas emissions and nitrogen removal from constructed wetlands in the low-temperature season

Plant species diversity is crucial in greenhouse gas emissions and nitrogen removal from constructed wetlands (CWs). However, previous studies have overlooked the impact of benthos on cumulative greenhouse gas emissions during the low-temperature season in CWs. In this study, we established 66 vertical flow CWs with three levels of species richness (1, 2, and 4 species) and eleven species compositions. The Corbicula fluminea was added or not added at each diversity level and monitored greenhouse gas emissions and effluent nitrogen concentration. Our findings indicated that (1) in microcosms without C. fluminea, high species richness significantly increased effluent nitrogen concentrations (NO3--N, NH4+-N, and TIN), but plant species richness did not affect cumulative CH4, N2O, and CO2 emissions. The presence of Hemerocallis fulva significantly increased cumulative CO2 emissions, while the presence of Iris tectorum significantly increased effluent nitrogen (NO3--N and TIN) concentrations and cumulative N2O emissions; (2) in microcosms with C. fluminea, the lowest cumulative CH4 emissions occurred when there were two species, but plant species richness did not affect cumulative CO2 and N2O emissions. The presence of H. fulva significantly increased cumulative CH4 emissions, while the presence of Reineckea carnea significantly increased effluent nitrogen (NO3--N, NH4+- N, TIN) concentrations; (3) at the same diversity level, the addition of C. fluminea significantly increased cumulative CH4 and N2O emissions, as well as effluent nitrogen concentrations. These results demonstrate that C. fluminea alters the effect of plant species diversity on cumulative greenhouse gas emissions and nitrogen removal from CWs during the low-temperature season. We recommend using a two-species mixture to reduce greenhouse gas emissions. However, we caution against using plant compositions with H. fulva or I. tectorum for effective wastewater treatment and greenhouse gas reduction in CWs.

Decommissioning of offshore wind farms and its impact on benthic ecology

At the end of their operational life time offshore wind farms need to be decommissioned. How and to what extent the removal of the underwater structures impairs the ecosystem that developed during the operational phase of the wind farm is not known. So, decision makers face a knowledge gap, making the consideration of such ecological impacts challenging when planning decommissioning. This study evaluates how complete or partial decommissioning of foundation structure and scour protection layer impacts local epibenthic macrofauna biodiversity. We assessed three decommissioning alternatives (one for complete and two for partial removal) regarding their impact on epibenthic macrofauna species richness. The results imply that leaving the scour protection layer in situ will preserve a considerable number of species while cutting of the foundation structure above seabed will be beneficial for the fauna of such foundation structures where no scour protection is installed. These results should be taken with a grain of salt, as the current data base is rather limited. Data need to be improved substantially to allow for reliable statements and sound advice regarding the ecological impact of offshore wind farm decommissioning.

Do recreational activities affect macrofauna distribution pattern in Amazonian macrotidal sandy beaches?

Recreational activities are important source of disturbance on sandy beaches and have a negative effect on benthic communities as they alter species abundance, diversity, and/or distribution. Here, we report for the first time the effects of the recreational activities on the distribution pattern of macrobenthic communities of Amazonian sandy beaches. Sampling was performed during three consecutive months with different beach use intensity in 2017 (before, during vacation, and one month after the vacation period) on two contrasting beaches regarding disturbance (Urban: Atalaia; and Protected: Corvinas) in the intertidal zone along two equidistant transects at seven equidistant sampling stations: from the high-tide water mark to the swash zone. At each sampling station, four biological and sediment samples were randomly collected. Also, in each station, the sediment compaction was determined using a manual penetrometer. Physical sediment variables remained constant over time in both beaches, whereas differences were found in sediment compaction over the periods. Sediment compaction was considered the most important factor for the differences observed in macrobenthic community structure in the study beaches, and it was related to intensity of recreational activities. Variations in density and changes in richness between periods and sampling stations were observed in Atalaia beach. On the other hand, Corvinas beach remained the same throughout the study. Overall, three faunal zones were distinguished: upper intertidal, intermediate intertidal, and low-intertidal, whereas in the vacation period, only two faunal zones were distinguished: upper-intertidal and intermediate-low intertidal.

Seasonal benthic species composition linked to coastal defense structures (CDS) in Kuala Nerus, Terengganu, Malaysia

Background

The natural hydrodynamic process of Kuala Nerus, Terengganu, has changed since the extension of Sultan Mahmud Airport runway in 2008. Consequently, severe coastal erosion has occurred in the area, particularly during the northeast monsoon season (NEM). Numerous types of coastal defense structures (CDS) have been constructed to protect the coastline. Despite the loss of esthetic values, the effect of CDS construction on marine organisms in the area remains unknown. Hence, this study aims to assess the ecological aspects of macrobenthic compositions at the CDS area of Kuala Nerus, Terengganu, based on the differences between the southwest (SWM) and northeast (NEM) monsoon seasons.

Methods

Macrobenthos were collected from the sediment in July (SWM) and December 2021 (NEM) using the Ponar grab at 12 substations from five sampling stations.

Results

The density of macrobenthos was higher in SWM (48,190.82 ind./m2) than in NEM (24,504.83 ind./m2), with phylum Mollusca recording the highest species composition (60-99.3%). The macrobenthos species had a low to moderate level of diversity (H' = 1.4-3.1) with the species were almost evenly distributed (J' = 0.2-0.8). Windward substations exhibited coarser grain sizes (38.56%-86.84%), whereas landward substations exhibited very fine grain sizes (44.26%-86.70%). The SWM season recorded a higher organic matter content (1.6%-6.33%) than the NEM season (0.4%-3.1%). However, metal concentrations in the surface sediment were within the safe range and permissible limits for both seasons, inferring that the macrobenthos composition was unaffected.

Discussion

This study demonstrated that the CDS associated with the monsoon system has controlled the hydrodynamics and nearshore sedimentary processes in the Kuala Nerus coastal zone, thereby affecting the macrobenthos population, in terms of richness and density. The ecological and energetic effects of the coastal structures in different seasons have resulted in a more significant result, with the SWM exhibiting a higher macrobenthos composition than the NEM.

Long-term impacts on estuarine benthic assemblages (2015-2020) after a mine tailing spill in SE Brazil

The Rio Doce estuary was critically impacted in 2015 by the world's largest mining tailing spill, with still unclear long-term effects on the aquatic biota. Here we present a long-term (2015 to 2020) assessment of estuarine benthic assemblages, where we demonstrate that despite a decline in the absolute concentrations of potentially toxic elements; sediment contamination is still above pre-impact conditions. The presence of these contaminants is likely responsible for a continued low habitat quality for the benthic fauna, characterized by a reduction of 96 % of the macroinvertebrate density and persistent change in the benthic assemblage composition. Our study supports previous work indicating the long-term nature of pollution impacts in estuaries, and demonstrate that although water quality levels were quickly adequate under regulatory terms, they largely lack significance to the overall ecosystem health assessment, as they are not related to the recovery of bottom- dwelling assemblages in estuarine ecosystems.

Environmental assessment of oyster beds in the northern Arabian Gulf Coast of the United Arab Emirates

The United Arab of Emirates (UAE) hosts valuable coastal and marine biodiversity, and oysters are one of the habitants of its marine ecosystem. Oysters play an essential role in the nearshore coasts where they work as an active filter. They filter nutrients, phytoplankton, sediments, heavy metals, and toxins out of the water, which improves the water quality. This is the first study that characterizes oyster bed habitats in the UAE by analyzing water quality parameters, polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs)and heavy metals in water, sediments and oyster samples collected from five locations along the coasts of Sharjah, Ajman, and Umm al Quwain. Oyster bed areas supported a diverse assemblage of benthic life including oysters, scallops, pen shells, hard corals, and macroalgae. Mobile species in these habitats included groupers, emperors, snappers, sea snakes, among others. The phytoplankton assemblages were dominated by diatoms, dinoflagellates, and small cryptophytes. Harmful diatom Pseudonitzschia was found in all locations. No detectable concentrations of PAHs and OCPs were reported in this study, and water quality parameters were within the acceptable levels for the region. On the other hand, water quality index was reported marginal, mostly due to the presence of higher than acceptable concentrations of chromium and mercury in all sites studied. Bioconcentration factors concluded that oysters were able to bioconcentrate metals such as arsenic, cadmium, chromium, and zinc, when compared to water. No detectable concentrations of lead and mercury were reported in oysters, suggesting higher depuration rates for those metals.

Potential macroalgal expansion and blue carbon gains with northern Antarctic Peninsula glacial retreat

The West Antarctic Peninsula (WAP) is a hotspot of physical climate change, especially glacial retreat, particularly in its northern South Shetland Islands (SSI) region. Along coastlines, this process is opening up new ice-free areas, for colonization by a high biodiversity of flora and fauna. At Potter Cove, in the SSI (Isla 25 de Mayo/King George Island), Antarctica, colonization by macroalgae was studied in two newly ice-free areas, a low glacier influence area (LGI), and a high glacier influence area (HGI) differing in the presence of sediment run-off and light penetration, which are driven by levels of glacial influence. We installed artificial substrates (tiles) at 5 m depth to analyze benthic algal colonization and succession for four years (2010-2014). Photosynthetic active radiation (PAR, 400-700 nm), temperature, salinity, and turbidity were monitored at both sites in spring and summer. The turbidity and the light attenuation (K_d) were significantly lower at LGI than at HGI. All tiles were colonized by benthic algae, differing in species identity and successional patterns between areas, and with a significantly higher richness at LGI than HGI in the last year of the experiment. We scaled up a quadrat survey on the natural substrate to estimate benthic algal colonization in newly deglaciated areas across Potter Cove. Warming in recent decades has exposed much new habitat, with macroalgae making up an important part of colonist communities 'chasing' such glacier retreat. Our estimation of algal colonization in newly ice-free areas shows an expansion of ∼0.005-0.012 km² with a carbon standing stock of ∼0.2-0.4 C tons, per year. Life moving into new space in such emerging fjords has the potential to be key for new carbon sinks and export. In sustained climate change scenarios, we expect that the processes of colonization and expansion of benthic assemblages will continue and generate significant transformations in Antarctic coastal ecosystems by increasing primary production, providing new structures, food and refuge to fauna, and capturing and storing more carbon.

Impact of sand bund removal on seagrass ecosystems: A study of macrobenthic community structure and correlation with macrophytes cover and sediments

This study investigated the impacts of the removal of sand bund on the macrobenthos community structure, seagrass cover, and sediment particle size in Merambong Shoal, Malaysia. The reclamation project deposited sand bund in the middle of Merambong seagrass shoal, resulting in its division into northern (NS) and southern (SS) halves. Ecosystem changes were monitored over a 31-month period using the transect lines method. Bi-monthly samples were collected for assessment. The results revealed a substantial decline in macrobenthos densities compared to previous studies. However, after the removal of the sand bund, there was a significant increase in macrobenthos density, specifically Polychaeta and Malacostraca, at NS. Seagrass cover at NS was initially lower than SS but showed an increase after the complete removal of the sand blockage. Sediment particle analysis reported a higher silt percentage at NS, indicating greater sedimentation at NS, which was partially sheltered from wave actions.

Deep-sea benthic crustacean and annelid data from the Bering Sea

Samples of Crustacea and Annelida (Polychaeta, Sipuncula, and Hirudinea) were collected in the Bering Sea and the northwestern Pacific Ocean during scientific cruise SO-249 BERING in 2016. Biological samples were collected from 32 locations by the team on-board RV Sonne using a chain bag dredge at depths ranging between 330-5,070 m, and preserved in 96% ethanol. Specimens were morphologically identified to the lowest taxonomic level possible using a Leica M60 stereomicroscope. The generated data here comprise taxonomic information as well as annotated bathymetric and biogeographic information from a total of 78 samples (26 Crustacea, 47 Polychaeta, 4 Sipuncula, and 1 Hirudinea). The dataset was prepared following Darwin Core Biodiversity standards for FAIR data sharing based on Ocean Biodiversity Information System (OBIS) and Global Biodiversity Facility (GBIF) guidelines. The standardised digitised data were then mobilised to both OBIS and GBIF under CC BY 4.0 licence to publicly share and adopt the data. As records of these important marine taxa from bathyal and abyssal depths are sparse, especially from the deep Bering Sea, the herein generated and digitised data aid in filling existing knowledge gaps on their diversity and distribution in that region. As part of the "Biogeography of the NW Pacific deep-sea fauna and their possible future invasions into the Arctic Ocean" (BENEFICIAL) project, this dataset thus not only increases our knowledge in re-assessing and uncovering the deep-sea diversity of these taxa, but also serves policy and management sectors by providing first-hand data for global report assessments.

From collapse to the health of the aquatic ecosystem in Dasha River (2006-2021): a case study of Shenzhen city in the Guangdong-Hong Kong-Macao Greater Bay Area, China

Compared with the aquatic ecosystem destruction caused by rapid urban development, substantial ecological restoration usually requires long periods and is a challenging process. Although river ecological restoration has been successful in different regions, the relationship between biodiversity, water quality, and effective measures applicable to developing countries remains poorly understood. This study was conducted in the Dasha River in Shenzhen city, one of the fastest-growing cities in China. The rehabilitation measures were sorted out in four phases to study the impact on water quality and biodiversity. In response, three campaigns were carried out to take phytoplankton, zooplankton, and benthos samples within the last three engineering stages, in 2007, 2012, and 2021. Synchronized investigations of water quality were conducted monthly from 2006 to 2021. Our analysis showed that the biodiversity of benthos has improved in recent years, which marks a turnaround for the aquatic ecological environment. According to the Hilsenhoff family biotic index (FBI), the water quality level in the 2021 campaign was promoted to "Good" in the downstream and "Fair" in the upper and middle streams. By analyzing Pearson's correlations between response ratios of water quality parameters and the Shannon-Wiener index of phytoplankton, zooplankton, and benthos, we concluded that biodiversity is significantly related to water quality. Specifically, the biodiversity of zooplankton is associated with ammonia nitrogen (NH₃-N) (R² =  - 0.77, P < 0.05), and benthos diversity is strongly negatively correlated with NH₃-N, total nitrogen, chemical oxygen demand, and biochemical oxygen demand (R² ≥ -0.82, P < 0.01). Despite the temporary negative impact of along-river interception on aquatic organisms in the campaign of 2012, the measures quickly and effectively improved water quality, which is the foundation for biodiversity improvement in 2021. This study provides insights into relationships among biodiversity, water quality, and regulation projects and can offer a reference for selecting aquatic ecosystem restoration measures in developing areas.

Circadian (re)colonisation dynamics of macroinvertebrates in an isolated karst spring

Freshwater ecosystems, especially springs, are highly sensitive to environmental changes. They are also excellent natural laboratories because of their stable conditions, reducing the number of variables to be considered in field studies. We examined the composition, dynamics and colonisation patterns of macroinvertebrates with respect to canopy coverage and time of day in which available areas are actively colonised. We used artificial substrates that mimicked the natural habitat structure at an isolated karst spring and recovered exposed substrates every 12 h. Physico-chemical parameters of water did not differ significantly regardless of canopy cover. The most numerous representatives and the pioneering champions were larvae of Baetidae (Ephemeroptera) and Chironomidae (Diptera). Simuliidae were also among the most successful pioneering species. Most observed groups more actively colonised substrates in the closed canopy area. Oligochaeta and Gammarus fossarum were more numerous on substrates in the open canopy area. Individuals of all analysed groups showed day-night migration patterns and were more active at night. Coleoptera (Elmis sp.) were the poorest (re)colonisers among the analysed taxa.

Food web dynamics in the mangrove ecosystem of the Pearl River Estuary surrounded by megacities

Global recognition that mangroves support coastal ecosystem services has increased; however, studies on trophic dynamics in mangrove ecosystems remain limited. We seasonally analysed the δ¹³C and δ¹⁵N of 34 consumers and 5 diets to elucidate the food web dynamics in the Pearl River Estuary (PRE). Fish had a large niche space during the monsoon summer, reflecting increased trophic roles. In contrast, the small niche space of benthos over seasons reflected consistent trophic positions. Consumers mainly utilized plant-derived organic matters in the dry season and particulate organic matters in the wet season. The present study with literature reviews revealed characteristics of the PRE food web with the depleted δ¹³C and enriched δ¹⁵N, indicating a high contribution of mangrove-derived organic carbon and sewage input, particularly in the wet season. Overall, this study confirmed the seasonal and spatial trophic dynamics in mangrove forests surrounding megacities for future sustainable mangrove ecosystem management.

Microplastic load of benthic fauna in Jiaozhou Bay, China

The prevalence of microplastic pollution in the ocean has caused widespread concern. Many studies have focused on the occurrence of microplastics in the marine environment and organisms, but the fate of microplastics in the ocean is still unclear, and the factors affecting the distribution of microplastics have not yet been consistently concluded. The aims of this study were to estimate the load of microplastics in benthic organisms as a temporary storage and to analyze the factors affecting microplastic ingestion by benthic organisms. For the purpose of this study, the benthic organisms in Jiaozhou Bay, China, were collected quarterly and were divided into the following six groups: polychaetes, mollusks, crustaceans, echinoderms, fish, and others. We concluded that the microplastic abundance in the benthos in Jiaozhou Bay was 1.00 ± 0.11 items/ind. (15.5 ± 3.5 items/g). The total load of microplastics in the benthic fauna in the bay with an area of 374 km² was estimated to be 36.4 kg. On an individual basis, the fish contained significantly more microplastics than the other taxa. Furthermore, the characteristics of the microplastics in the benthic organisms were mainly fibrous, black, polyethylene, and <500 μm in size. In addition, the microplastic ingestion by benthic organisms was regulated by multiple factors, including biological characteristics and the environment. The masses of the organisms, the ambient seawater and sediment, and the spatial variations all influenced the microplastic ingestion by the organisms. The results of this study demonstrate that benthic organisms are an important storage for microplastics as they transferred through the ocean, and they provide an unbiased comparison of microplastic pollution among multiple organisms and the relevant pollution factors.

Effects of sedimentary heavy metals on meiobenthic community in tropical estuaries along eastern Arabian Sea

The central west coast of India comprises the 720 km long coastline of Maharashtra state and houses widespread industrial zones along the eastern Arabian Sea. Sediments from seven industrial-dominated estuaries along the central west coast were studied for metal enrichment and benthic assemblages to determine sediment quality status and ecological effects in these areas. The suit of geochemical indices highlighted the contamination of sediment in the estuaries concerning heavy metals. Positive correlations of Hg with Co, Zn, Ni, Cr, and Pb indicated the source similarity and effect of anthropogenic activity. non-Metric Multidimensional Scaling (n-MDS) based on meiofaunal abundance showed a cleared separation of clusters through the gradient of heavy metal concentrations. The Canonical Correspondence Analysis (CCA) results with the Monte Carlo test signified those heavy metals influenced the meiobenthic community. Heavy metals (Cr, Ni, Zn, Cd, Pb, and Hg) were the main drivers shaping the meiofaunal community with a significant (p < 0.05) reduction in taxa richness, diversity, and evenness. Dominant meiofaunal assemblages evidence the tolerance of foraminiferans and nematodes. However, these taxa were affected by decreased abundance at impacted sites compared to other fauna. In conclusion, results demonstrated that impairment occurred in the meiofaunal community in most estuaries (except AB and KK).

Spatial pH variability of coral reef flats of Kiritimati Island, Kiribati

Ocean acidification poses a threat to carbonate-dominated marine systems, such as tropical coral reefs, as it impacts the ability of organisms to calcify. For assessing the susceptibility of coral reef flats to open ocean acidification it is crucial to better understand the dynamics between the carbonate chemistry of open ocean waters flowing onto coral reef flats and the ecological and hydrodynamic processes that locally modify seawater conditions. In this study, variations in seawater pH and temperature were measured along cross-reef flat transects in high resolution (∼0.3 m) and complemented by surveys of the benthic community composition and reef flat bathymetry. Results represent a snapshot in time and suggest that reef flat hydrodynamic processes determine spatial pH modifications, with little influence of variations in benthic community composition. As mean reef flat pH largely equals ocean conditions, ocean acidification has had and will have an unhampered impact on narrow fringing reef flats.

Benthic biogeographic patterns on the deep Brazilian margin

The Brazilian continental margin (BCM) extends from the Tropical to the Subtropical Atlantic Ocean, with much of its seafloor within deep waters, supporting rich geomorphological features and under wide productivity gradients. Deep-sea biogeographic boundaries on the BCM have been limited to studies that used water mass and salinity properties of deep-water masses, partly as a result of historical under sampling and a lack of consolidation of available biological and ecological datasets. The aim of this study was to consolidate benthic assemblage datasets and test current oceanographic biogeographical deep-sea boundaries (200-5,000 m) using available faunal distributions. We retrieved over 4,000 benthic data records from open-access databases and used cluster analysis to examine assemblage distributions against the deep-sea biogeographical classification scheme from Watling et al. (2013). Starting from the assumption that vertical and horizontal distribution patterns can vary regionally, we test other schemes incorporating latitudinal and water masses stratification within the Brazilian margin. As expected, the classification scheme based on benthic biodiversity is in overall agreement with the general boundaries proposed by Watling et al. (2013). However, our analysis allowed much refinement in the former boundaries, and here we propose the use of two biogeographic realms, two provinces and seven bathyal ecoregions (200-3,500 m), and three abyssal provinces (>3,500 m) along the BCM. The main driver for these units seems to be latitudinal gradients as well as water mass characteristics such as temperature. Our study provides a significant improvement of benthic biogeographic ranges along the Brazilian continental margin allowing a more detailed recognition of its biodiversity and ecological value, and also supports the needed spatial management for industrial activities occurring in its deep waters.

High polychaete diversity in the Gulf of Guinea (West African continental margin): The influence of local and intermediate scale ecological factors on a background of regional patterns

The Tropical East Atlantic is one of the least studied areas in the world's oceans, and thus a blank spot on the map of marine studies. Shaped by dynamic currents and shifting water masses, it is a key region in discussions about marine ecology, biodiversity, and zoogeography, while facing numerous, poorly understood, and unmonitored threats associated with climate change, acidification, and pollution. Polychaete diversity was assessed along four transects along the Ghana coast, from shallow to deep bottoms and distributed along the whole upwelling marine ecoregion. Despite high sampling effort, steep species accumulation curves demonstrated the necessity of further sampling in the region. We observed zonation of fauna by depth, and a decrease in species richness from 25 m to 1000 m depth. Polychaete communities were influenced by sediment type, presence of oxygen minimum zones, and local disturbances caused by elevated barium concentrations. Similar evenness along the depth gradient reflected the importance of rare species in the community structure. Differences in phylogenetic diversity, as reflected by taxonomic distinctness, were small, which suggested high ecosystem stability. The highly variable species richness at small scale (meters) showed the importance of ecological factors giving rise to microhabitat diversity, although we also noticed intermediate scale (50-300 km) differences affecting community structure. About 44 % of the species were rare (i.e. recorded only in three or fewer samples), highlighting the level of patchiness, while one fifth was distributed on all transects, therefore along the whole upwelling ecoregion, demonstrating the influence of the regional species pool on local communities at particular stations. Our study yielded 253 species, increasing the number of polychaetes known from this region by at least 50 %. This casts doubt on previous findings regarding Atlantic bioregionalization, biodiversity estimates and endemism, which appear to have been more pronouncedly affected by sampling bias than previously thought.

Transition of an estuarine benthic meiofauna assemblage 1.7 and 2.8 years after a mining disaster

Background

Estuaries are transitional coastal ecosystems that are threatened by multiple sources of human pollution. In 2015, mining tailings from an upstream dam failure caused massive metal contamination that impacted benthic assemblages on the Brazilian Rio Doce estuary.

Methods

In this study, we investigate and compare meiofaunal assemblages with eDNA metabarcoding 1.7 years (2017) and 2.8 years (2018) after the initial contamination by mine tailings in order to evaluate the continued impact of sediment mine tailing contaminants on the structure of benthic assemblages after the disaster.

Results

The community was dominated by Arthropoda and Nematoda 1.7 yr after the impacts (42 and 29% of meiofaunal sequence reads, respectively) but after 2.8 years Arthropoda (64.8% of meiofaunal sequence reads) and Rotifera (11.8%) were the most common taxa. This continued impact on meiofaunal assemblage revealed a lower phylogenetic diversity (7.8-fold) in 2018, despite overall decrease in metal concentration (Al, Ba, Cr, As, Fe, Zn, Mn, Pb, Cd, Co) in sediments. Our data suggests that differences in benthic assemblages and loss of diversity may be influenced by contaminants in sediments of this estuary, and indicate that broad eDNA assessments are greatly useful to understand the full range of biodiversity changes in dynamic estuarine ecosystems.

Textile microfibers in wild Antarctic whelk Neobuccinum eatoni (Smith, 1875) from Terra Nova Bay (Ross Sea, Antarctica)

Antarctica has been affected directly and indirectly by human pressure for more than two centuries and recently plastic pollution has been recognized as a further potential threat for its unique biodiversity. Global long-range transport as well as local input from anthropogenic activities are potential sources of plastic pollution in both terrestrial and marine Antarctic territories. The present study evaluated the presence of microplastics in specimens of the Antarctic whelk Neobuccinum eatoni, a key species in benthic communities of the Ross Sea, one of the largest marine protected areas worldwide. To this aim, a thermo-oxidative extraction method was applied for microplastic isolation and quantification, and polymer identification was performed by manual μ-FTIR spectroscopy. Textile (semi-)synthetic or composite microfibers (length range: 0.8-5.7 mm) were found in 27.3% of whelk specimens, suggesting a low risk of bioaccumulation along Antarctic benthic food webs in the Ross Sea. Their polymer composition (of polyethylene terephthalate and cellulose-polyamide composites) matched those of outdoor technical clothing in use by the personnel of the Italian "Mario Zucchelli" station near Terra Nova Bay in the Ross Sea. Such findings indicate that sewage from base stations may act as potential local sources of textile microplastic fibers in this remote environment. More in-depth monitoring studies aiming at defining the extent of microplastic contamination related to such sources in Antarctica are encouraged.

Laboratory study of Se speciation in the sediment and oligochaete Lumbriculus variegatus from an aquatic environment

Sediments are the major sink for selenium (Se) in aquatic environments. Se speciation in sediments is crucial for its bioavailability and toxicity in benthos, but this is relatively understudied. In this study, the background levels of Se in the river sediments, fish flakes, and Lumbriculus variegatus were also detected. Then, the dynamic changes of selenium speciation and concentrations in sediments were investigated after adding selenite (Se(IV)) and seleno-L-methionine (Se-Met) in the sediments for 90 and 7 days, and the accumulation and depuration of Se(IV) and Se-Met for 7 days in the oligochaete L. variegatus were also explored. Without the presence of worms, the levels of Se(IV) in the sediments were relatively stable within 7 days but showed a decreasing trend during the 90 days of aging. In contrast, Se-Met in the sediments showed a sharp decrease within 3 days of aging. The LC₅₀-96 h values of Se(IV) and Se-Met in L. variegatus were 372.6 and 9.4 μg/g, respectively. Interestingly, the dominant Se species in Se(IV)- or Se-Met-treated L. variegatus was Se-Met, whose level was increased with time in 7 days of exposure. Se was barely depurated from L. variegatus during the 8 days of the depuration period. This study has provided indispensable data on the levels of total Se in the abiotic and biotic matrices and the biodynamics of Se in a representative benthos, which could better understand the ecological risk of Se to the freshwater benthic communities.

Data on benthic species assemblages and seafloor sediment characteristics in an offshore windfarm in the southeastern North Sea

The German Bight (North Sea) is a centre of development of offshore wind energy. In the near future, windfarms will cover a significant part (about 25%) of the German Exclusive Economic Zone. In order to understand and assess potential effects of the construction and early operational phase of offshore wind turbines on the marine environment, an extensive research programme was carried out at Germany's first offshore windfarm alpha ventus. Here, data are presented on macroinfauna and local sediment characteristics collected as part of this programme. Grab samples were taken annually in autumn in 2008 (baseline), 2009 (construction phase) and 2010 and 2011 (early operational phase). Sampling stations were located along transects between adjacent turbines inside the windfarm and in two reference areas with similar environmental conditions in terms of sediment characteristics and water depth. A total of 336 samples were taken inside the windfarm and 192 samples in the reference areas. Sediment characteristics were described in terms of grain size distribution and organic content. The infauna was taxonomically analysed and quantified in terms of abundance and biomass. One-hundred three infauna taxa were identified, mainly belonging to the polychaetes, crustaceans and bivalves, living in fine to medium sandy soft bottom in water depths ranging from -27 m to -30 m. The data can be useful in meta-analyses of renewable energies impacts. Additionally, the data can support species distribution modelling to gain a better understanding of species' requirements and habitats as a basis for spatial planning scenarios and the evaluation of the ecological status of the marine environment. Moreover, the data can serve as baseline data for future monitoring and management of nearby protected areas where environmental conditions are comparable to those of the present study area.

Microplastics alter multiple biological processes of marine benthic fauna

Marine sediments are a sink for microplastics, making seabed organisms particularly exposed. We used meta-analysis to reveal general patterns in a surge in experimental studies and to test for microplastic impact on biological processes including invertebrate feeding, survival and energetics. Using Hedge's effect size (g), which assesses the mean response of organisms exposed to microplastics compared to control groups, we found negative impacts (significant negative g values) across all life stages (overall effect size (g) = -0.57 95 % CI [-0.76, -0.38]), with embryos most strongly affected (g = -1.47 [-2.21, -0.74]). Six of seven biological process rates were negatively impacted by microplastic exposure, including development, reproduction, growth and feeding. Survival strongly decreased (g = -0.69 [-1.21, -0.17]), likely due to cumulative effects on other processes such as feeding and growth. Among feeding habits, omnivores and deposit feeders were most negatively impacted (g = -0.93 [-1.69, -0.16] and -0.92 [-1.53, -0.31], respectively). The study incorporated the first meta-analysis to contrast the effects of leachates, virgin, aged and contaminated particles. Exposure to leachates had by far the strongest negative effects (g = -0.93 [-1.35, -0.51]), showing studies of contaminants and leachates are critical to future research. Overall, our meta-analysis reveals stronger and more consistent negative impacts of microplastics on seabed invertebrates than recorded for other marine biota. Seabed invertebrates are numerous and diverse, and crucial to bottom-up processes, including nutrient remineralisation, bentho-pelagic coupling and energy transfer through the ocean food web. Marine sediments will store microplastics over long timescales. The reveal that microplastics impinge on multiple fundamental biological processes of seabed fauna implies plastic pollution could have significant and enduring effects on the functioning of the ocean.

Mercury concentration and speciation in benthic organisms from Isfjorden, Svalbard

Polar regions are an important part of the global mercury cycle and interesting study sites due to different possible mercury sources. The full understanding of mercury transformations in the Arctic is difficult because this region is the systems in transition -where the effects of the global climate change are the most prominent. Benthic organisms can be valuable bioindicators of heavy metal contamination. In July 2018, selected benthic organisms: macroalgae, brittle stars, sea urchins, gastropods, and starfish were collected in Isfjorden, Spitsbergen. Two of the sampling stations were located inside the fjord system and one at the entrance to the fjord. The results showed that the starfish were the most contaminated with mercury. Total mercury concentrations in these organisms were at least 10 times higher than in other organisms. However, they effectively deal with mercury by transporting it to hard tissue. The dominant form of mercury was the labile form.

Benthic ecosystem functioning under climate change: modelling the bioturbation potential for benthic key species in the southern North Sea

Climate change affects the marine environment on many levels with profound consequences for numerous biological, chemical, and physical processes. Benthic bioturbation is one of the most relevant and significant processes for benthic-pelagic coupling and biogeochemical fluxes in marine sediments, such as the uptake, transport, and remineralisation of organic carbon. However, only little is known about how climate change affects the distribution and intensity of benthic bioturbation of a shallow temperate shelf sea system such as the southern North Sea. In this study, we modelled and projected changes in bioturbation potential (BP_p) under a continuous global warming scenario for seven southern North Sea key bioturbators: Abra alba, Amphiura filiformis, Callianassa subterranea, Echinocardium cordatum, Goniada maculata, Nephtys hombergii, and Nucula nitidosa. Spatial changes in species bioturbation intensity are simulated for the years 2050 and 2099 based on one species distribution model per species driven by bottom temperature and salinity changes using the IPCC SRES scenario A1B. Local mean bottom temperature was projected to increase between 0.15 and 5.4 °C, while mean bottom salinity was projected to moderately decrease by 1.7. Our results show that the considered benthic species are strongly influenced by the temperature increase. Although the total BP remained rather constant in the southern North Sea, the BP_p for four out of seven species was projected to increase, mainly due to a simultaneous northward range expansion, while the BP_p in the core area of the southern North Sea declined for the same species. Bioturbation of the most important species, Amphiura filiformis and Echinocardium cordatum, showed no substantial change in the spatial distribution, but over time. The BP_p of E. cordatum remained almost constant until 2099, while the BP_p of A. filiformis decreased by 41%. The northward expansion of some species and the decline of most species in the south led to a change of relative contribution to bioturbation in the southern North Sea. These results indicate that some of the selected key bioturbators in the southern North Sea might partly compensate the decrease in bioturbation by others. But especially in the depositional areas where bioturbation plays a specifically important role for ecosystem functioning, bioturbation potential declined until 2099, which might affect the biochemical cycling in sediments of some areas of the southern North Sea.

Physiological response to seawater pH of the bivalve Abra alba, a benthic ecosystem engineer, is modulated by low pH

The presence and behaviour of bivalves can affect the functioning of seafloor sediments through the irrigation of deeper strata by feeding and respiring through siphonal channels. Here, we investigated the physiological response and consecutive impact on functioning and body condition of the white furrow shell Abra alba in three pH treatments (pH = 8.2, pH = 7.9 and pH = 7.7). Although no pH effect on survival was found, lowered respiration and calcification rates, decreased energy intake (lower absorption rate) and increased metabolic losses (increased excretion rates) occurred at pH ∼ 7.7. These physiological responses resulted in a negative Scope for Growth and a decreased condition index at this pH. This suggests that the physiological changes may not be sufficient to sustain survival in the long term, which would undoubtedly translate into consequences for ecosystem functioning.

Integrated transcriptomic and metabolomic analyses reveal mechanism underlying higher resistance of the marine oligochaete Thalassodrilides cf. briani (Clitellata: Naididae) to heavy contamination of sediments with polycyclic aromatic hydrocarbons

In some coastal areas, sediments are contaminated with various chemical compounds, causing significant threats to marine organisms. Therefore, the development of remediation techniques is important. Here, we focused on bioremediation using marine benthic animals such as aquatic oligochaetes. The oligochaete Thalassodrilides cf. briani is highly resistant to contamination of sediments with toxic chemicals. We examined whether T. cf. briani could decompose high-concentration polycyclic aromatic hydrocarbons (PAHs) in sediments. Furthermore, relevant genes expressed in T. cf. briani exposed to contaminated sediment were comprehensively examined using next-generation sequencing, and its metabolites were identified by metabolomic analysis using gas chromatography-mass spectrometry. T. cf. briani reduced the concentration of 16 PAHs in the sediment from 55,900 to 45,200 ng/g dry weight in 50 days, thereby reducing total PAH concentrations by approximately 20%. The results of transcriptomic analysis suggest that activation of a drug-metabolizing enzyme system may promote the metabolism of harmful chemical substances during excretion of chemicals from the body. According to the results of principal component analysis based on the values of 43 types of metabolomes identified by metabolomic analysis, groups were divided according to the difference in the number of exposure days. In addition, levels of glutamine, which is important for maintaining digestive tract functions, increased. This suggests that the digestive tract function promotes the metabolism and detoxification of foreign substances. Furthermore, transcriptome analysis revealed that glutamate dehydrogenase increased 1.3-fold and glutamine synthetase increased 1.7-fold, confirming the increase in glutamine. Thus, we conclude that T. cf. briani adapted to the polluted sediment by regulating its metabolism.

Long-term changes in the macrobenthic assemblages at a harbour sediment disposal site in the southern North Sea

This study focussed on the long-term, sediment-driven changes of macrobenthic assemblages in dredged harbour sediment from Rotterdam harbour disposed of in excavated sand extraction pits off the Dutch coast. Macrobenthic species and sediment grain size composition were studied in samples from two disposal sites and the surrounding environment over ten years after the cessation of disposal activities. There was a strong association between the sediment granulometry and the benthic assemblage composition. Shortly after the last discharge, the top layer of the sediments in the pits contained 20%-60% mud (particles <63 μm) and was colonised by benthic species typical for these sediments. The pit sediments and benthic assemblages contrasted strongly with the surrounding medium-coarse sediment, extremely low in mud (<0.01%). Over eight to ten years, the top layers of the disposal sites became significantly less muddy (ca. 5%-15% mud), and the benthic assemblages changed over this period from mud-favouring species dominated by annelids to species preferring fine sand with relatively low mud percentages dominated by molluscs. The two different disposal sites converged in sediment composition and benthic assemblages over the ten years of monitoring. The contrast with the medium-coarse sediments with very low mud percentages remained even after this period. The use of sand extraction pits as disposal sites for dredged harbour sediments may be seen as an economically sound beneficial use option in dredged material management, albeit with long-term ecological effects.

Impacts of wastewater treatment plants on benthic macroinvertebrate communities in summer and winter

Treated effluent from municipal wastewater treatment plants (WWTPs) is a major source of contamination that can impact population size, community structure, and biodiversity of aquatic organisms. However, because the majority of field research occurs during warmer periods of the year, the impacts of wastewater effluent on aquatic communities during winter has largely been neglected. In this study, we assessed the impacts of wastewater effluent on aquatic benthic macroinvertebrate (benthos) communities along the effluent gradients of two WWTPs discharging into Hamilton Harbour, Canada, during summer and winter using artificial substrates incubated for 8 weeks. At the larger of the two plants, benthic macroinvertebrate abundance was higher and diversity was lower at sites downstream of the outfall compared to upstream sites in both seasons. Whereas at the smaller plant, the opposite was observed, abundance increased and diversity decreased with distance from the outfall in both seasons. While the impacts of wastewater on benthic communities were largely similar between seasons, we did detect several general seasonal trends - family diversity of macroinvertebrates was lower during winter at both WWTPs and total abundance was also lower during winter, but only significantly so at the smaller WWTP. Further, benthic macroinvertebrate community composition differed significantly along the effluent gradients, with sites closest and farthest from the outfall being the most dissimilar. Our contrasting results between the WWTPs demonstrate that plants, with different treatment capabilities and effluent-receiving environments (industrial/urban versus wetland), can dictate how wastewater effluent impacts benthic macroinvertebrate communities.

In Situ Effects of a Microplastic Mixture on the Community Structure of Benthic Macroinvertebrates in a Freshwater Pond

Benthic communities contain some of the most threatened organisms in aquatic habitats due to different anthropogenic pressures. The high abundance of microplastics in sediments will continue to increase in the future, further increasing the probability of interactions between macroinvertebrates and microplastics. In the present study, a benthic community in a relatively pristine shallow pond was exposed either to an environmentally relevant high concentration of a microplastic mixture of 80 g m^-2 in the sediment, or a control sediment, without the addition of microplastics. The mixture of microplastics contained irregularly shaped polyethylene, polyvinyl chloride, and polyamide in a ratio of 50:25:25%, respectively. The in situ experiment lasted for 100 d. The total number of taxa that colonized the microcosms was 22 (17 in the control and 18 in the microplastic treatment), and the colonization was not affected by the treatment. The most dominant group within the macroinvertebrate community was the dipteran family Chironomidae, in both the control and the microplastic treatment. No significant differences in the abundance and biomass at a community level were recorded between the groups by permutational multivariate analysis of variance (F = 0.993, p = 0.456 and F = 0.344, p = 0.797, respectively). The mixture of microplastics did not influence the abundance or biomass of the functional feeding groups (F = 1.810, p = 0.137 and F = 0.377, p = 0.736, respectively). The species richness, species abundance, species biomass, Shannon's diversity index, and Simpson's index of diversity showed no statistically significant differences between the control and treatment groups. Czekanowski's quantitative similarity index indicated that 84% of the community remained unaffected after microplastic exposure. Environ Toxicol Chem 2022;41:888-895. © 2021 SETAC.

Occurrence of microfibres in wild specimens of adult sea urchin Paracentrotus lividus (Lamarck, 1816) from a coastal area of the central Mediterranean Sea

This study investigates the occurrence of anthropogenic fibres inside wild Paracentrotus lividus at a Mediterranean coastal area in 2020. From each sea urchin, the coelomic fluid was directly analysed while digestive tracts and gonads were removed, pre-treated with trypsin (0.3%) and digested with H₂O₂ (10%) before analysis. A total of 260 fibres and 1 fragment were found in 100 specimens, with an average of 2.6 items/individual. Fibres were more abundant in the digestive system, less in gonads and in the coelomic fluid, respectively. Fourier transform infrared (FTIR) analysis of representative fibres identified 67% natural (cotton-based) and 33% synthetic polymers (polyester) suggesting their origin from textiles, possibly released from laundry sewages. Overall, these results encourage further in-depth investigations on fibres accumulation and potential transfer through the trophic chain up to humans.

Climate regime shifts and biodiversity redistribution in the Bay of Biscay

Global ocean warming, wave extreme events, and accelerating sea-level rise are challenges that coastal communities must address to anticipate damages in coming decades. The objective of this study is to undertake a time-series analysis of climate change (CC) indicators within the Bay of Biscay, including the Basque coast. We used an integrated and flexible methodology, based on Generalized Additive Mixed Models, to detect trends on 19 indicators (including marine physics, chemistry, atmosphere, hydrology, geomorphology, biodiversity, and commercial species). The results of 87 long-term time series analysed (~512,000 observations), in the last four decades, indicate four groups of climate regime shifts: 1) A gradual shift associated with CC starting in the 1980s, with a warming of the sea surface down to 100 m depth in the bay (0.10-0.25 °C per decade), increase in air temperature and insolation. This warming may have impacted on benthic community redistribution in the Basque coast, favouring warm-water species relative to cold-water species. Weight at age for anchovy and sardine decreased in the last two decades. 2) Deepening of the winter mixed layer depth in the south-eastern bay that probably led to increases in nutrients, surface oxygen, and chlorophyll concentration. Current increases on chlorophyll and zooplankton (i.e., copepods) biomass are contrary to those expected under CC scenarios in the region. 3) Sea-level rise (1.5-3.5 cm per decade since 1990s), associated with CC. 4) Increase of extreme wave height events of 16.8 cm per decade in the south-eastern bay, probably related to stormy conditions in the last decade, with impacts on beach erosion. Estimating accurate rates of sea warming, sea-level rise, extreme events, and foreseeing the future pathways of marine productivity, are key to define the best adaptation measures to minimize negative CC impacts in the region.

Climate change scenarios of increased CO2 and temperature affect a coral reef peracarid (Crustacea) community

The effects of applying scenarios of increasing CO₂ and temperature, using a mesocosm experiment, on the structure of a macrofaunal coral reef peracarid community were investigated for the first time. Samples were taken from artificial substrate units (ASUs), colonized by macrofauna from the coral reef subtidal zone of Serrambi beach (Brazil). In the laboratory, the ASUs were exposed to a Control (Ctrl) treatment and three climate change Scenarios (Sc) (increase of T° of 0.6, 2, and 3 °C, and pH drop of 0.1, 0.3, and 0.7 units for Sc I, II and III respectively), and were collected after 15 and 29 days of exposure. Our results showed that the effect of different temperature and acidity levels under experimental climate change scenarios significantly impacted density, diversity and community structure. Major differences were observed when applying Sc II and III. Peracarida also showed a reduction in specimen number when comparing both exposure times. Overall, Amphipoda, Tanaidacea and Isopoda communities all displayed a reduction in the number of individuals for both scenarios and exposure time factors, while Cumacea responded negatively in all scenarios, suggesting that these individuals were more sensitive to the experimental conditions. Dissimilarities were greatest between the Ctrl and Sc III, particularly after 29 days. Two species, Elasmopus longipropodus (Amphipoda) and Chondrochelia dubia (Tanaidacea), greatly contributed to these dissimilarities. This study demonstrates that even an intermediate level of increasing ocean temperature and acidification will negatively impact the structure of the Peracarida macrofaunal community on coral reefs. Also demonstrates that different species of Peracarida exhibit divergent response patterns, highlighting the specific responses of these taxa to the impacts of environmental stressors. These outcomes highlight the importance of studying the effects of climate change on benthic peracarids, especially because they incubate their eggs. This characteristic can reduce migration potential and thereby reduces the individual's ability to disperse in response to a changing environment.

Quantification of blue carbon pathways contributing to negative feedback on climate change following glacier retreat in West Antarctic fjords

Global warming is causing significant losses of marine ice around the polar regions. In Antarctica, the retreat of tidewater glaciers is opening up novel, low-energy habitats (fjords) that have the potential to provide a negative feedback loop to climate change. These fjords are being colonized by organisms on and within the sediment and act as a sink for particulate matter. So far, blue carbon potential in Antarctic habitats has mainly been estimated using epifaunal megazoobenthos (although some studies have also considered macrozoobenthos). We investigated two further pathways of carbon storage and potential sequestration by measuring the concentration of carbon of infaunal macrozoobenthos and total organic carbon (TOC) deposited in the sediment. We took samples along a temporal gradient since time of last glacier ice cover (1-1000 years) at three fjords along the West Antarctic Peninsula. We tested the hypothesis that seabed carbon standing stock would be mainly driven by time since last glacier covered. However, results showed this to be much more complex. Infauna were highly variable over this temporal gradient and showed similar total mass of carbon standing stock per m² as literature estimates of Antarctic epifauna. TOC mass in the sediment, however, was an order of magnitude greater than stocks of infaunal and epifaunal carbon and increased with time since last ice cover. Thus, blue carbon stocks and recent gains around Antarctica are likely much higher than previously estimated as is their negative feedback on climate change.

Habitat heterogeneity: A confounding factor for the effect of pollutants on macrobenthic community in coastal waters

Discrepancies were found between Ecological Status of sediments evaluated though the analysis of macrobenthic community and chemical analyses along a heavily trafficked and contaminated maritime seaway in Tyrrhenian Sea. Chemical analyses showed some sites highly contaminated by PAHs and metals with values exceeding thresholds for Good Chemical status and representing potential toxicological risk for benthic animals. Conversely, macrobenthic communities were highly rich and diverse, with Ecological Status (through M-AMBI) Good and High at each site. Sampling depth, total organic carbon, and total nitrogen were the major factors influencing biotic indices (AMBI, M-AMBI, S, H), even if concentrations of PAHs and metals (V, As, and Fe) contributed in explaining a part of indices variability. Habitat heterogeneity of sampled sites is likely acting as a confounding factor for two reasons: (1) high variability of environmental parameters leads to high richness and diversity, to which M-AMBI is sensitive, and (2) environmental parameters explained part of the variability of indices, together with contaminants. Our results suggested the importance of considering natural variability as a fundamental step of environmental impact assessment, for the correct interpretation of biotic indices.

Environmental DNA metabarcoding for monitoring metazoan biodiversity in Antarctic nearshore ecosystems

Antarctic benthic ecosystems support high biodiversity but their characterization is limited to a few well-studied areas, due to the extreme environment and remoteness making access and sampling difficult. Our aim was to compare water and sediment as sources of environmental DNA (eDNA) to better characterise Antarctic benthic communities and further develop practical approaches for DNA-based biodiversity assessment in remote environments. We used a cytochrome c oxidase subunit I (COI) metabarcoding approach to characterise metazoan communities in 26 nearshore sites across 12 locations in the Vestfold Hills (East Antarctica) based on DNA extracted from either sediment cores or filtered seawater. We detected a total of 99 metazoan species from 12 phyla across 26 sites, with similar numbers of species detected in sediment and water eDNA samples. However, significantly different communities were detected in the two sample types at sites where both were collected (i.e., where paired samples were available). For example, nematodes and echinoderms were more likely to be detected exclusively in sediment and water eDNA samples, respectively. eDNA from water and sediment core samples are complementary sample types, with epifauna more likely to be detected in water column samples and infauna in sediment. More reference DNA sequences are needed for infauna/meiofauna to increase the proportion of sequences and number of taxa that can be identified. Developing a better understanding of the temporal and spatial dynamics of eDNA at low temperatures would also aid interpretation of eDNA signals from polar environments. Our results provide a preliminary scan of benthic metazoan communities in the Vestfold Hills, with additional markers required to provide a comprehensive biodiversity survey. However, our study demonstrates the choice of sample type for eDNA studies of benthic ecosystems (sediment, water or both) needs to be carefully considered in light of the research or monitoring question of interest.

Abundance data of benthic peracarid crustaceans from the South Atlantic and Southern Ocean

Peracarid data were collected in the Southern Ocean and South Atlantic Ocean. Sampling was performed during nine different expeditions on board of RRS James Clark Ross and RV Polarstern, using epibenthic sledges (EBS) at depth ranging between 160–6348 m at 109 locations. The correlation between environmental variables and peracarid abundance was investigated. Abundance data comprise a total of 128570 peracarids (52366 were amphipods, 28516 were cumaceans, 36142 isopods, 5676 mysidaceans and 5870 were tanaidaceans). The presented data are useful to investigate the composition and abundance patterns of peracarid orders at a wide depth range and spatial scale in the Southern Ocean. They can also be reused to compare their abundance with that of other taxa in broader ecological surveys.

Benthic fauna contribute to microplastic sequestration in coastal sediments

Microplastics are ubiquitous in the marine environment, however, the mechanisms governing their uptake by, and burial within, seabed habitats are poorly understood. In this study, microplastic burial and its impact on fauna-mediated sedimentary processes was quantified at three coastal sites, and the potential contribution of burrowing faunal communities to this process assessed via functional trait diversity analysis of field data. In addition, laboratory exposures were used to assess whether sediment-processing undertaken by the brittlestar Amphiura filiformis, a key species in the sampled area, could explain the burial of microplastic fibres. Field observations confirmed broad-scale burial of microplastics across the coastal seabed, consistent across sites and seasons, with microplastic sequestration linked to benthic-pelagic exchange pathways, driven by burrowing fauna. Brittlestars were observed to bury and line their burrow walls with microfibres during experiments, and their burial activity was also modified following exposure to nylon fibres, relative to controls. Collectively, these results indicate that biodiverse and functionally important seabed habitats act as microplastic sinks, with burrowing fauna contributing to this process via well-known benthic-pelagic pathways, the rates of which are modified by plastic exposure.

Downslope migration of free-living corals (Scleractinia: Fungiidae) in typhoon-exposed reef habitats at Okinawa, Japan

Offshore Onna Village, Okinawa Island, Japan, there is a large and densely covered coral assemblage of free-living mushroom corals (Scleractinia: Fungiidae) on a reef slope at depths from 20 m to 32 m, covering an area of approximately 350 × 40 m². From previous research, it is known that migration distances of mushroom corals may depend on coral shapes, coral sizes, substrate, and bottom inclination. However, until now there have been no published examples of regular Fungiidae movement and behavior from typhoon-exposed coastlines, such as those in the western Pacific Ocean. Our surveys across three years offshore Onna Village show that mushroom corals always move in down-slope direction from shallow to deeper reef zones. The results indicated that mushroom corals migrated faster in autumn than in other seasons, and that oval-elongate fungiids, and particularly those with a smooth underside, migrated more quickly than species with other shapes. Surprisingly, we observed a negative relationship between the presence of typhoons and migration rates. We also observed active migration by fungiid individuals to escape situations in which they were threatened to become overgrown by Acropora corals, or when they needed to escape from burial underneath coral debris.

Persistent domoic acid in marine sediments and benthic infauna along the coast of Southern California

Blooms of the diatom genus Pseudo-nitzschia occur annually in the Southern California Bight (SCB), and domoic acid (DA) associated with these events can contaminate fisheries, presenting both human and wildlife health risks. Recent studies have suggested that marine sediments may act as a reservoir for DA, extending the risk of food web contamination long after water column blooms have ended. In this study, we conducted a regional assessment of the extent and magnitude of DA in the benthic environment, and monthly observations of sediments and benthic infauna at multiple stations over a 16-month period. DA was widespread in continental shelf sediments of the SCB. The toxin was detected in 54% of all shelf habitats sampled. Detectable concentrations ranged from 0.11 ng/g to 1.36 ng/g. DA was consistently detected in benthic infauna tissues over the monthly timeseries, while the DA concentrations in sediments during the same period were commonly below detection or at low concentrations. The presence of DA in the benthic environment did not always have an apparent water column source, raising the possibility of lateral transport, retention/preservation in sediments or undetected blooms in subsurface waters. In most cases, DA was detected in tissues but not in the co-located surface sediments. Coarse taxonomic sorting of the infauna revealed that the accumulation of DA varied among taxa. We observed that DA was widespread among lower trophic level organisms in this study, potentially acting as a persistent source of DA to higher trophic levels in the benthos.

Taxonomic and functional diversity of benthic macrofauna associated with rhodolith beds in SE Brazil

Rhodoliths are free-living and morphologically diverse marine calcareous algae commonly distributed over the continental shelf seafloor. They increase the seabed structural complexity and are of potential value as feeding and reproductive grounds for a myriad of marine fauna. The higher structural seabed complexity within rhodolith beds may also increase benthic diversity by creating microhabitats, but this relationship has been rarely explored within rhodolith beds worldwide. Here we compared benthic macrofaunal (>500 µm) structure on rhodolith beds (nodule epifauna) and within unconsolidated sediments (sediment infauna) under high and low-density beds to test whether rhodolith bed density and nodule morphology influenced macrofaunal assemblages. We observed that macrofaunal density on nodules (2538 ± 288.7 ind·m-2) was 15-fold higher when compared to sediments under those beds (166 ± 38.8 ind·m-2). Rhodolith bed density was positively related to macrofaunal density, composition, and functional diversity on the rhodoliths. Low-density beds (61 ± 27.1 nodules·m-2) with discoid-shape nodules were dominated by peracarid crustaceans whereas high-density beds (204 ± 18.7 nodules·m-2) with spheroidal nodules were dominated by Annelid polychaetes. The sediment macrofauna was also positively influenced by the density of rhodolith nodules, which increased sediment carbonate and organic quality (protein and lipids) under high-density beds. Macrofaunal functional diversity was generally higher on rhodoliths, with low similarity (low nestedness) and high taxa turnover between macrofaunal assemblages of rhodoliths and sediments. These findings indicate that rhodolith beds provide an unique habitat for benthic macrofaunal communities, with exclusive functional and taxonomic richness that are likely not typical in the unconsolidated sediment below these beds in SE Brazil. This study highlights the importance of protecting rhodolith beds from multiple sources of anthropogenic disturbance and exploration on continental shelves.

Impacts of bottom trawling on benthic biogeochemistry in muddy sediments: Removal of surface sediment using an experimental field study

Experimental benthic dredging was conducted in an unfished, muddy area in the Baltic Proper to mimic the impact of trawling by removing surface sediment, with a focus on benthic biogeochemical processes. Sediment cores were taken on the track and compared to undisturbed controls. Benthic fluxes were immediately affected and an upward shift in pore water DIC profiles was detected. The time needed for the sediment to readjust to a new biogeochemical state seemed to be nutrient-specific. Sediment properties (profiles of chlorophyll, organic carbon and water content) were found to change significantly. Macrofauna was removed completely by the dredge pointing out the potential loss of highly valuable functions that are associated with them. In the Baltic Sea, in areas which were previously the most heavily fished, the frequency of trawling may have left little time for readjustment and potentially kept the seabed in a permanent state of transient biogeochemical cycling.

Long-term response of marine benthic fauna to thin-layer capping with powdered activated carbon in the Grenland fjords, Norway

The Grenland fjords in Norway have a long history of contamination by large emissions of dioxins and mercury. As a possible sediment remediation method in situ, thin-layer capping with powdered activated carbon (AC) mixed with clay was applied at two test sites at 30 m and 95 m depth in the Grenland fjords. This study presents long-term effects of the AC treatment on the benthic community structure, i.e. nine years after capping. Capping with AC significantly reduced the number of species, their abundance and biomass at the two test sites, compared to uncapped reference sites. At the more shallow site, the dominant brittle star species Amphiura filiformis disappeared shortly after capping and did not re-establish nine years after capping. At the deeper site, the AC treatment also caused long-lasting negative effects on the benthic community, but some recovery was observed after nine years. Ecological indices used to assess environmental status did not capture the impaired benthic communities caused by the capping. The present study is the first documentation of negative effects of powdered AC on marine benthic communities on a decadal scale. Our results show that the benefits of reduced contaminant bioavailability from capping with AC should be carefully weighed against the cost of long-term detrimental effects on the benthic community. More research is needed to develop a thin-layer capping material that is efficient at sequestering contaminants without being harmful to benthic species.

Benthic macroinvertebrate community response to environmental changes over seven decades in an urbanized estuary in the northeastern United States

Narragansett Bay is representative of New England, USA urbanized estuaries, with colonization in the early 17th century, and development into industrial and transportation centers in the late 18th and early 20th century. Increasing nationwide population and lack of infrastructure maintenance led to environmental degradation, and then eventual improvement after implementation of contaminant control and sewage treatment starting in the 1970s. Benthic macroinvertebrate community structure was expected to respond to these environmental changes. This study assembled data sets from the 1950s through 2010s to examine whether quantitative aggregate patterns in the benthic community corresponded qualitatively to stressors and management actions in the watershed. In Greenwich Bay and Providence River, patterns of benthic response corresponded to the decline and then improvement in sewage treatment at the Fields Point wastewater treatment plant. In Mount Hope Bay, the benthos corresponded to changes in bay fish populations due to thermal discharge from the Brayton Point power plant. The benthos of the Upper West Passage corresponded to climatic changes that caused regime shifts in the plankton and fish communities. Future work will examine the effects of further environmental improvements in the face of continued climatic changes and population growth.