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The invasive macroalga Rugulopteryx okamurae represents an unprecedented case of bioinvasion by marine macroalgae facing the European coasts. Since the first apparition of the species in the Strait of Gibraltar in 2015, its fast dispersion along the introduced habitats constitutes a real challenge to develop monitoring strategies that ahead of its impacts. The present study uses three different approaches to address impacts on the benthic ecosystems, at the same time offers relevant data for future management actions in El Estrecho Natural Park (PNE). Information obtained by monitoring permanent sentinel stations revealed a significant loss in resident species coverage after the moment of maximum growth in 2017. Thus, despite coverage of R. okamurae did not strongly varied in the latter years, impacts generated remain high in the habitats studied. Estimations of the invasive species coverage by combining cartographic image analysis and in situ data predicted a major occupation (over 85% coverage) between 10 and 30 m, coinciding with the maximum rocky surface areas (m2) mapped on the PNE. Furthermore, a Citizen Science research collaboration evidenced impacts on the benthic seascape through an ad hoc exploration of images that allowed a “before” and “after” comparison of the invasion process in the same geographic locations. This has made it possible to graphically demonstrate severe changes in the underwater seascape and, therefore, the general impact of this new biological invasion. The spatial colonization estimations combined with the impacts reported by both scientific [Sessile Bioindicators in Permanent Quadrats (SBPQ) sentinel stations] and civilian (Citizen Science) monitoring methodologies claim the urgent development of further studies that allow the design of monitoring strategies against R. okamurae expansion across the Mediterranean and Atlantic waters.

Over the course of a year, we conducted three field deployments in South San Francisco Bay to examine seasonal variability in bottom drag. Our data consisted of turbulence measurements both within and outside the bottom boundary layer and benthic characterization surveys adjacent to our study site. Our results suggest that canopies of benthic worm and amphipod feeding tubes, which were denser during summer, can increase the drag coefficient by up to a factor of three relative to the smoother beds found in winter and spring. The extent of the drag increase varied depending on the measurement device, with the greatest increase inferred by measurements taken further from the bed. The small scale and temporally varying population densities of these living roughness elements pose significant challenges for hydrodynamic models, and future work is needed to begin incorporating benthic biology statistics into drag coefficient parameterizations. Plain Language Summary: Tidal flows in estuaries are affected by the properties of the seafloor. By taking flow measurements in South San Francisco Bay during three different seasons, we show here that feeding tubes built by organisms that live in the sediment bed during summer make the bed much rougher and slow down average flow velocities. The extent of the estimated difference in roughness depends on the instrument used for the measurement, but the overall results imply that these bottom‐dwelling populations should be taken into account when modeling flows in estuaries. Key Points: Measured drag coefficients vary across seasons, tidal cycles, and measurement devicesDense canopies of living roughness elements may increase dragSpatial/seasonal variations in benthic biology should be incorporated into drag parameterizations [ABSTRACT FROM AUTHOR]

Abstract This study investigated variations in the composition and biomass of demersal fish assemblages over a 570-metre depth gradient on the temperate, lower west coast of Australia (32° S) in the south-eastern Indian Ocean. Fish assemblages were sampled using Baited Remote Underwater Stereo Video systems (stereo-BRUVs, n = 284 deployments) from shallow waters around a mid-shelf island (Rottnest Island) to the continental slope within a submarine canyon (Perth Canyon). A total of 9013 individual fishes (i.e. ΣMaxN) belonging to 179 species and 75 families were identified. Multivariate statistical analyses revealed three distinct fish assemblages associated with the continental shelf (5–199 m), margin (200–300 m) and upper slope (300–570 m). A distance-based linear model revealed that among environmental covariates, benthic biota (sessile invertebrates and macroalgae) accounted for the highest proportion of variation in fish assemblage composition (16.9%) followed by depth (12.5%) and seabed relief (10.5%). Generalised additive models indicated higher biomass of fish associated with habitats characterised by benthic biota. Species richness decreased with increasing depth across the continental shelf but remained constant with increasing depth on the continental slope. Average fish length was not correlated with depth but was greatest at 200–400 m depth. The continental margin and upper slope habitats revealed a distinct change in assemblage composition as well as a peak in biomass of species that was dominated by larger-bodied meso-predators at the continental margin. The trends exhibited in fish assemblage characteristics across this broad depth range can inform ecosystem based management for deepwater fisheries resources. Highlights • Peak in fish biomass at the shelf margin dominated by larger meso-predator species. • Reveals fish assemblage potentially targeted by multiple fisheries & jurisdictions. • The shelf margin zone strongly correlated with substantial benthic habitat. • Distinct spatial heterogeneity found in deepwater fish assemblages. • 284 baited video systems were deployed in deepwater off the west coast of Australia. [ABSTRACT FROM AUTHOR]

Concerns over the fate of pharmaceuticals and personal care products (PPCP) within the environment have been growing with the advent of more precise analytical methods. The discharge of municipal wastewater has been identified as a significant source of these contaminants, particularly where wastewater treatment is minimal. Here we present results from a comprehensive monitoring regime located around Victoria, BC, Canada. Samples were collected between 2009 and 2016 from a variety of sources including marine water, sediment and biota adjacent to two major untreated sewage outfalls, as well as the sewage itself. PPCP concentrations within the untreated sewage were high, and the sediment surrounding the outfalls showed corresponding contamination. However, this contamination dropped quickly with distance from the outfall such that by 800 m distance most PPCPs were below detection limits. Tissue samples of resident Northern Horse mussels (Modiolus modiolus) collected adjacent to one of the major sewage outfalls showed high single sample concentrations of the antimicrobial triclosan (317 ng g−1 dry weight), the antibiotic ciprofloxacin (176 ng g−1 dry weight), as well as the antidepressant sertraline (84.1 ng g−1 dry weight). Reference stations from around the region showed very low concentrations of contamination with almost all PPCP concentrations being below detection limits. Within the sewage, concentrations were largely stable overtime, with the exception of triclosan and triclocarban which both showed declines over the study period.

The aim of this study was to determine if benthic diatoms can be used as effective and reliable indicators of ionic composition and conductivity in different stream order categories. Samples were collected on two occasions from 22 sampling sites within the Bloukrans River system, Eastern Cape Province, South Africa. The data collected were subjected to multivariate statistical technique, i.e. CCA, to determine environmental gradients along which the diatom species were distributed as well as to elucidate hypothesised differences in community structure per stream order. Significant differences between the two sampling periods were observed in dissolved oxygen, temperature, Na, B, Ca, Zn, Cu, Cr, K, Fe, phosphate, conductivity, salinity and nitrate, while significant stream order variation was observed for conductivity, salinity, Mg, Ca and sediment nitrates. Study sites were grouped into two broad categories (stream order 1 and 2/3 sites) based on CCA. As pollution increased, low to moderate pollution-tolerant species such as Fragilaria tenera, Cyclostephanos dubius and Gyrosigma acuminatum were replaced by high pollution-tolerant species such as Nitzschia palea, Gomphonema parvulum, Tryblionella apiculata, Diploneis vulgaris and Staurosira elliptica. This shows that diatom assemblages are appropriate indicators of ionic composition/conductivity and hydromorphological characteristics (e.g. stream size) of running waters. The results highlight the importance of creating regional calibration datasets which will make it possible to develop procedures to determine conductivity and ion concentration effects on biota. [ABSTRACT FROM AUTHOR]

Aim A key paradigm of deep-sea ecology is that the ocean interior is a food-limited environment, which limits the faunal growth. Here, we estimated the efficiency of deep-sea fauna in exploiting resources to assess the potential response of deep-sea organisms to changes in the food inputs expected with global change. Location Mediterranean Sea. Time period 1989-2010. Major taxa studied Viruses, prokaryotes, meiofauna, macrofauna and megafauna. Methods Using the largest data set spanning from microbes to megafauna produced synoptically so far, we investigated patterns of abundance, biomass and ecosystem efficiency across depth-related and longitudinal gradients of food availability in both Western and Eastern Basins of the Mediterranean Sea. Results Our results revealed that prokaryotes dominated benthic biomass at depths > 2,000 m. Contrary to what has been reported at a global scale, meiofaunal biomass decreased with increasing water depth more rapidly than macrofauna and megafauna. Meiofauna showed a significant negative log-linear relationship with increasing water depth in the whole Mediterranean Sea, whereas the other benthic components, from viruses to megafauna, did not decrease significantly, decreased or even increased (e.g., prokaryotes) with increasing water depth. Taking all components together, the efficiency of benthic ecosystems in exploiting organic carbon (OC) inputs increased with increasing depth, in both mesotrophic and ultra-oligotrophic conditions of the deep Mediterranean Sea. Main conclusions Changes in ecological efficiency in exploiting the energy available in food-limited conditions suggest that deep-sea ecosystems can show a responsive adaptation to changes in OC inputs from the photic zone. Our results contribute to explaining the high efficiency of resource exploitation by consumers in limited trophic conditions and allow us to hypothesize that the consequences of a potential reduction of food supply in deep-sea ecosystems induced by global changes could be less severe than expected. [ABSTRACT FROM AUTHOR]

Thirty seven benthic samples of the inner shelf area of São Sebastião, Brazil, were collected between April 1994 and August 1998 and analysed for seventeen chlorinated pesticide residues and PCBs congeners. Pesticide residues and PCBs congeners levels were low (ng/g) and predominantly found in the crustacean samples. DDE was the most frequently residue with a maximum of 9,7 ng/g followed by HCHs with maximum of 17,1ng/g. As for the PCBs, the heavier congeners predominate: CB 138,153,170, 180 and 183. Maximum total PCBs was 17,4 ug/g in a crab sample. Higher levels of PCBs are related to feeding habits and local inputs of raw sewage or land runoff. Although EPA and FDA (U.S.A) below the guidelines for human consumption propose these levels, they do show that even in marine areas without intense agricultural or industrial activities these compounds are present at detectable levels.Trinta e sete amostras de bentos da área interna do Canal de São Sebastião, Brasil, foram coletadas entre Abril de 1994 e Agosto de 1998 e analisadas quanto aos níveis de resíduos de 17 pesticidas organoclorados os congêneres dos PCBs. Os níveis de resíduos de organoclorados e PCBs foram baixos( ng/g) e encontrados com maior freqüência nas amostras de crustáceos. DDE foi o resíduo de pesticida encontrado com mais freqüência apresentado um máximo de 9,7 ng/g seguido dos isômeros de HCHs com um máximo de 17,1 ng/g. No caso dos PCBs os congêneres mais pesados foram os predominantes: CB 138, 153, 170, 180 e 183. O valor máximo de PCBs totais foi de 17,4 ug/g numa amostra de crustáceo. Níveis maiores de PCBs estão associados aos hábitos alimentares e introduções pontuais de esgotos e água de drenagem urbana. Apesar dos níveis observados estarem abaixo dos recomendados para consumo humano pela EPA e da FDA( U.S.A) ,eles demonstram que mesmo em área marinhas costeiras sem agricultura intensiva ou atividades industriais de porte , estes compostos orgânicos persistentes sintéticos ( POPS) estão presentes em níveis mensuráveis.

Abstract: Benthic ecosystem in Gwangyang Bay, a fast developing industrial area with steel production, port container handling, petroleum and other chemical processing in South Korea was studied. The average levels of polychlorinated biphenyls (ΣPCB) in the benthic components were: seawater 2.99±0.13 (ng/L); sediment 294±118 (ng/g TOC); [biota=ng/g lipid] starfish 92; prawn 131±2; mussels 127±22; crab 182±114; clam 187; polychaeta 215; sea cucumber 497±90; squill 603±38; fish 396±159. Levels in the inner bay samples were higher than the outer bay samples suggesting land based pollution. Good correlation (r 2 =0.79; p <0.05) existed between PCB concentration and lipid content indicating partitioning processes in action. PCB signature in the abiotic and biotic components shows enrichment of lower chlorinated congeners emitted by a unique source nearby, viz. steel manufacturing plant. [Copyright &y& Elsevier]

The article discusses a study of the effects of demersal trawling on benthic biota in the southern Benguela upwelling region. A geographic information system (GIS) was utilized to plot the spatial distribution of commercial fishing activity in South Africa from 2003 to 2007. Prior log categorization has reportedly rendered the absolute values of epifaunal biomass inappropriate for further univariate analysis. Conventional analysis of variance (ANOVA) and permutational multivariate ANOVA (PERMANOVA) were used in the two-way crossed design of the study. Results show that an ophiuroid brittle star has increased while the polychaete Chloeia decreased with heavier trawling.

Repeat multibeam mapping of two slope-confined canyons on the northwest Australian margin provides new understanding of the processes that are active in shaping these environments. The Cape Range and Cloates canyons initiate on the mid to lower continental slope but are now known to be connected to the shelf via small channels and gullies. Both canyons have areas of steep walls, with evidence of slides, and large depressions on the canyon floors. These canyons were first mapped systematically with multibeam sonar in 2008 and were remapped in 2020 during a biodiversity survey that also collected high-resolution imagery and biological samples. Comparison of seabed features between these two time periods indicates active sliding, minor headwall retreat and continued excavation of deep depressions on the canyon floor. Significantly, intact blades of displaced seagrass imaged at various depths up to 4200 m throughout both canyons indicates that material sourced from the adjacent continental shelf is being transported through these canyon systems. Turbidity currents are actively modifying canyon walls and floor depressions, while also providing a sediment source that has resulted in minor accretion on the canyon floor. Sedimentation likely regulates benthic communities in these canyons, with imagery showing highest densities of sessile invertebrates in habitats protected from sedimentation (e.g. rock overhangs, cliff edges). Since steep canyon habitats are rare within these canyons, and support high benthic abundance, they likely represent biologically significant areas of the Gascoyne Marine Park. Repeat mapping provides an understanding of the dynamics of these canyons and a context for assessing and monitoring the stability of the seabed habitats within this marine reserve. • Repeat mapping of slope-confined submarine canyons reveals active sedimentary processes on a passive continental margin. • Both canyons contain evidence for active sliding, minor headwall retreat and continued excavation of deep floor depressions. • Intact displaced seagrass blades indicate channelling of material from the continental shelf through these canyon systems. • Sessile invertebrates have highest densities in rare habitats protected from sedimentation, such as on rock overhangs. [ABSTRACT FROM AUTHOR]

Abstract: Geological, biological and biogeochemical characterization of the previously unexplored margin off Unimak Island, Alaska between 1965 and 4822m water depth was conducted to examine: (1) the geological processes that shaped the margin, (2) the linkages between depth, geomorphology and environmental disturbance in structuring benthic communities of varying size classes and (3) the existence, composition and nutritional sources of methane seep biota on this margin. The study area was mapped and sampled using multibeam sonar, a remotely operated vehicle (ROV) and a towed camera system. Our results provide the first characterization of the Aleutian margin mid and lower slope benthic communities (microbiota, foraminifera, macrofauna and megafauna), recognizing diverse habitats in a variety of settings. Our investigations also revealed that the geologic feature known as the “Ugamak Slide” is not a slide at all, and could not have resulted from a large 1946 earthquake. However, sediment disturbance appears to be a pervasive feature of this margin. We speculate that the deep-sea occurrence of high densities of Elphidium, typically a shallow-water foraminiferan, results from the influence of sediment redeposition from shallower habitats. Strong representation of cumacean, amphipod and tanaid crustaceans among the Unimak macrofauna may also reflect sediment instability. Although some faunal abundances decline with depth, habitat heterogeneity and disturbance generated by canyons and methane seepage appear to influence abundances of biota in ways that supercede any clear depth gradient in organic matter input. Measures of sediment organic matter and pigment content as well as C and N isotopic signatures were highly heterogeneous, although the availability of organic matter and the abundance of microorganisms in the upper sediment (1–5cm) were positively correlated. We report the first methane seep on the Aleutian slope in the Unimak region (3263–3285m), comprised of clam bed, pogonophoran field and carbonate habitats. Seep foraminiferal assemblages were dominated by agglutinated taxa, except for habitats above the seafloor on pogonophoran tubes. Numerous infaunal taxa in clam bed and pogonophoran field sediments and deep-sea “reef” cnidarians (e.g., corals and hydroids) residing on rocks near seepage sites exhibited light organic δ13C signatures indicative of chemosynthetic nutritional sources. The extensive geological, biogeochemical and biological heterogeneity as well as disturbance features observed on the Aleutian slope provide an attractive explanation for the exceptionally high biodiversity characteristic of the world’s continental margins. [Copyright &y& Elsevier]

Abstract: A suite of management options for a prawn trawl fishery in Torres Strait, Australia was assessed for impacts on the benthic fauna using a dynamic management strategy evaluation approach. The specification of the management options was gained through consultation with stakeholders. Data for the model was drawn from several sources: the fleet data from fishery logbooks and satellite vessel monitoring systems, benthic depletion rates from trawl-down experiments, benthic recovery rates from post-experiment recovery monitoring studies, and benthic distribution from large-scale benthic surveys. Although there were large uncertainties in the resulting indicators, robust measures relevant to management were obtained by taking ratios relative to the status quo. The management control with the biggest effect was total effort; reducing trawl effort always led to increases in benthic faunal density of up to 10%. Spatial closures had a smaller benefit of up to 2%. The effect of closing a set of buffer zones around reefs to trawling was indistinguishable from the status quo option. Closing a larger area, however, was largely beneficial especially for sea cucumbers. When the spatial distributions of fauna prior to fishing were accounted for, fauna with distributions positively correlated with effort improved relative to those negatively correlated. The reduction in prawn catch under effort reduction scenarios could be ameliorated by introducing temporal closures over the full-moon period. [Copyright &y& Elsevier]

Abstract: A study was conducted on the impacts of the presence of the Acoustic Thermometry of Ocean Climate (ATOC)/Pioneer Seamount cable on the benthos from nearshore waters adjacent to its origin at Pillar Point Air Force Station in Half Moon Bay, California to its terminus 95km along its length on Pioneer Seamount. The coaxial Type SD cable was installed, unburied on the seafloor in 1995. Thirteen sites along the cable route were surveyed using the Monterey Bay Aquarium Research Institute (MBARI) ROVs Ventana and Tiburon equipped with cable-tracking tools. Quantitative comparisons of biological communities and seafloor features between cable and control sites were performed at nine stations. Forty-two hours of video footage and 138 push cores were collected over 15.1km of seafloor. Approximately 12.1km of the cable was observed (13% of the cable route). This study documents the appearance and condition of the cable and the underlying seafloor, and the effects of the cable on biological communities along its route. Limited self-burial of the cable has occurred during the 8-year deployment, particularly over the continental shelf and upper slope. Cable strumming by nearshore wave action has incised rocky siltstone outcrops. Several observations of kinks and snags in the cable on the upper slope (∼240m depth) suggest contact with trawling gear. Few changes in the abundance or distribution of benthic fauna were detectable from video observations (epifaunal) and sediment core samples (infauna). Of 17 megafaunal groups and 19 infaunal taxa, no tests evaluating the overall effect of the cable were statistically significant. While these results indicate that the biological impacts of the cable are minor at most, three megafaunal groups exhibited cable-related changes at one or more stations. Actiniarians (sea anemones) colonized the cable when it was exposed on the seafloor, and were therefore generally more abundant on the cable than in surrounding, sediment-dominated seafloor habitats. Some fishes were also more abundant near the cable, apparently due to the higher habitat complexity provided by the cable. The study also documents general changes in the benthos across the Central California continental margin. [Copyright &y& Elsevier]

Abstract: Water and sediment quality and benthic biota were investigated in all seasons during three years in the River Akagawa that receives the effluent from a mine drainage treatment plant at its upstream site. The upper reaches kept the low pH, the comparatively high concentrations of metals and a large amount of iron deposited on the riverbed. The predominant macroinvertebrates were Protonemura sp., Capnidae, Nemoura sp. and Chironomidae in the upper and middle reaches. In the lowest reaches, the community structure of the macroinvertebrate changed into Chironomidae, Trichoptera (Hydropsychidae) and Ephemeroptera (Baetis sp.) as the pH was increased. From the results of multivariate analyses, it was found that the restoration of pH and attached algae and the increase in the concentrations of nutrients and organic matter promoted the inhabitation of Chironomidae and Hydropsychidae, whereas the dissolved metals in the river water inhibited the inhabitation of these families. Moreover, the sedimentation of metals would cause a severe damage to the inhabitation of Hydropsychidae compared with that of Chironomidae. [Copyright &y& Elsevier]

This study applies detailed seafloor bathymetry data and seafloor images to understand upper slope features and how these influence the distribution of seafloor biota on the East Antarctic margin. The East Antarctic slope on the Sabrina margin has been shaped by diverse processes related to repeated glaciation. Differences in the morphology of gullies on the upper slope enable an understanding of the likely processes that have been active on this margin. Gully morphology varies according to changes in slope gradient, which may have driven variations in sedimentation. Areas of lower slope angles may have led to rapid sediment deposition during glacial expansion to the shelf edge, and subsequent sediment failure. Typically, gullies in these areas are U-shaped, initiate well below the shelf break, are relatively straight and long, and have low incision depths, consistent with formation due to mass wastage. Areas of higher slope angles likely experienced enhanced flow of erosive turbidity currents during glaciations associated with the release of sediment-laden basal meltwaters. Sediment-laden subglacial meltwater flows typically create gullies such as those we observe that initiate at, or near, the shelf break; are V-shaped in profile; and have high sinuosity, deep incision depths and a relatively short downslope extent. The short downslope extent reflects a reduced sediment load associated with increased seawater entrainment as the slope becomes more concave in profile. These differences in gully morphology have important habitat implications associated with differences in the composition and beta-diversity of the seafloor communities. This upper slope region also supports seafloor communities that are distinct from those on the adjacent shelf, highlighting the uniqueness of this environment for biodiversity. Conservation strategies therefore need to consider slope and shelf communities as distinct and equally important components of the Antarctic ecosystem. • Upper slope gullies on this Antarctic margin have distinct morphology. • Upper slope morphology is driven largely by variations in depositional history. • Benthic community structure and beta-diversity is associated with gully morphology. • Upper slope communities are distinct from the adjacent continental shelf. [ABSTRACT FROM AUTHOR]

We provide here the first assessment of the composition, abundance and distribution of rocky reef fishes of Itaipu Sound, Rio de Janeiro, off the southeastern Brazilian coast. Monthly visual censuses, benthic quadrats and chain link transects were conducted over one year on rocky reefs at three islands (Menina, Mãe and Pai). A total of 2466 individual fish, belonging to 29 families and 42 species were recorded. The most abundant fish species were Parablennius pilicornis, Haemulon steindachneri, Orthopristis ruber and Diplodus argenteus. Sheltered and complex habitats showed the most abundant and diverse fish populations. There was a major significant separation between sampling sites and a secondary seasonal pattern. The three sites showed similar fish communities with locally structured environmental gradients according to their inherent habitat characteristics.

The papers in this special issue present the results of a five-year project to study sedimentary biogeochemical processes in the Strait of Georgia, with special emphasis on the near-field of a large municipal outfall. Included in this special issue are overviews of the sedimentology, benthic biology, status of siliceous sponge reefs and distribution of organic carbon in the water column. Other papers address the cycling of contaminants (PCBs, PBDEs) and redox metals in the sediment, a method to map the extent of the influence of municipal effluent from staining on benthic bivalves, and the relationships among geochemical conditions and benthic abundance and diversity. The latter set of papers addresses the role of municipal effluent as a pathway of organic carbon and other contaminants into the Strait of Georgia and the effect of the effluent on benthic geochemistry and biology. [Copyright &y& Elsevier]