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Abstract Climate change brings a range of challenges and opportunities to shrimp fisheries globally. The case of the Colombian Pacific Ocean (CPO) is notable due the crucial role of shrimps in the economy, supporting livelihoods for numerous families. However, the potential impacts of climate change on the distribution of shrimps loom large, making it urgent to scrutinize the prospective alterations that might unfurl across the CPO. Employing the Species Distribution Modeling approach under Global Circulation Model scenarios, we predicted the current and future potential distributions of five commercially important shrimps (Litopenaeus occidentalis, Xiphopenaeus riveti, Solenocera agassizii, Penaeus brevirostris, and Penaeus californiensis) based on an annual cycle, and considering the decades 2030 and 2050 under the Shared Socioeconomic Pathways SSP 2.6, SSP 4.5, SSP 7.0, and SSP 8.5. The Bathymetric Projection Method was utilized to obtain spatiotemporal ocean bottom predictors, giving the models more realism for reliable habitat predictions. Six spatiotemporal attributes were computed to gauge the changes in these distributions: area, depth range, spatial aggregation, percentage suitability change, gain or loss of areas, and seasonality. L. occidentalis and X. riveti exhibited favorable shifts during the initial semester for both decades and all scenarios, but unfavorable changes during the latter half of the year, primarily influenced by projected modifications in bottom salinity and bottom temperature. Conversely, for S. agassizii, P. brevirostris, and P. californiensis, predominantly negative changes surfaced across all months, decades, and scenarios, primarily driven by precipitation. These changes pose both threats and opportunities to shrimp fisheries in the CPO. However, their effects are not uniform across space and time. Instead, they form a mosaic of complex interactions that merit careful consideration when seeking practical solutions. These findings hold potential utility for informed decision-making, climate change mitigation, and adaptive strategies within the context of shrimp fisheries management in the CPO.

For marine ranching, efficiently and accurately detecting, tracking, and enumeration of benthic organisms can help farmers understand the growth and population changes of marine products, avoid high-risk tasks, and analyze changes in the marine ecological environment. To address the problems of target occlusion, low detection accuracy, and numerous small targets in existing marine organism detection models in complex seabed environments, an improved YOLOv5+DeepSORT algorithm for detecting and tracking benthic organisms is proposed. This algorithm integrates the Global Context Block attention mechanism with the BottleneckCSP module to form a new BottleneckCSPGC module, enhancing feature extraction capabilities. Replace the original loss function with the Normalized Wasserstein Distance (NWD) loss function to improve the detection accuracy of small targets. Finally, experimental results show that the accuracy on the underwater dataset reached 87.1% mAP@0.5 and 53.3% mAP@0.5:0.95, which are 1.8% and 4.0% higher than YOLOv5, respectively. The use of DeepSORT for tracking and counting provides technical support for marine ranching supervision.

Within the program "Marine Ecosystems of the Siberian Arctic," based on materials collected during cruises 69 and 72 of the R/V Akademik Mstislav Keldysh, the distribution of chemical elements (As, Ba, Bi, Co, Cr, Cr, Cd, Co, Cu, Cr, Mn, Ni, Pb, Sc, Ti, Tl, Th, V, U, and Zn) and organic carbon in the benthic mass taxa of methane seepage fields in the Laptev Sea and outside of them was examined. For the first time, the bioaccumulation potential (BP) was quantified, taking into account, in addition to the concentrations of elements in organisms, their biomass. On the C-15 methane field, the ophiuroid population accumulates each element per square meter of seafloor up to 40 times greater than at the background station. Ophiuroids and bivalves exhibited elevated BP for Ni, As, Ba, Cu, Ti, V, Mn, and Zn compared to other elements. At the same time, the BP of ophiuroids significantly exceeds that of bivalves. It is suggested that the increased bioaccumulation of some heavy metals and metalloids is related to greater bioavailability of organic matter in the bottom sediments of methane seeps. Organic carbon revealed the highest BP, which was especially pronounced in the C-15 methane field. At the background station, taxa accumulate a significantly smaller (by a factor of 10) amount of carbon in their biomass. As a result of the detritus feeders' activity, bottom sediments are enriched in organic carbon, which indicates an important contribution of benthic organisms to the carbon cycle in the Arctic seas. [ABSTRACT FROM AUTHOR]

This research provides an extensive analysis of the biodiversity and distribution patterns of copepod crustaceans associated with octocoral species. A comprehensive dataset comprising 966 records pertaining to 233 copepod species, encompassing 54 genera, 18 families, and 3 orders, was compiled from 92 scientific papers published between 1858 and 2023, and updated as open data to GBIF. These copepods were found to be closely associated with 183 octocoral species, representing 72 genera and 28 families. The analysis revealed a total of 393 distinct interspecific associations between copepods, classified under the orders Cyclopoida, Harpacticoida, and Siphonostomatoida, and diverse octocorals. Approximately 60% of these associations were reported only once in the literature, which poses challenges to assessing the level of host specificity among the majority of copepod species linked with octocorals. Notably, over 91% of the recorded copepod species were found at depths not exceeding 30 m, with only four copepod species reported at greater depths surpassing 500 m. The presence of these symbiotic copepods was documented across 215 sampling sites situated within 8 of the 12 defined marine ecoregions, with particular attention to the Western Indo-Pacific, Central Indo-Pacific, and Temperate Northern regions. Despite the comprehensive examination of available data, this study highlights substantial gaps in our comprehension of copepod crustacean diversity and distribution in association with octocorals. Moreover, crucial information concerning symbiotic copepods is conspicuously absent for approximately 94% of potential octocoral host species. These disparities emphasize the imperative need for further scientific inquiry to unveil the intricacies of symbiotic relationships and to contribute to a more holistic understanding of copepod–octocoral associations. [ABSTRACT FROM AUTHOR]

The Living Docks restoration program was implemented in the Indian River Lagoon (IRL), Florida, with the goal of affixing oyster restoration mats to dock pilings to promote the growth of filter feeding benthic organisms which can help improve local water quality. However, the relationship between IRL water quality parameters and the presence of filter feeders on the mats is not entirely clear. This study investigates the presence of benthic organisms on eight Living Docks which were deployed throughout the central part of the IRL. Environmental factors (e.g., water salinity, turbidity, pH, and temperature) were collected from the closest available water station to each dock. The main goal was to identify the presence and overall change in percent cover of specific benthic organism(s), those which are known filter feeders, in relationship to environmental parameters. Among functional groups which were identified, barnacles, biofilms, encrusting bryozoans (EBs), oysters, and sponges demonstrated significantly higher cover than the others. Barnacles were higher in abundance at specific dock locations and an increased water pH (up to 8.1), turbidity, and temperature. EB presence was positively impacted by salinity but did not respond to changes in turbidity or temperature within the measured ranges. Oysters were not observed to be impacted by any of the factors within measured ranges. Sponges had sustained abundance in half of the docks in this study. However, they did not respond to any of the environmental factors within measured ranges in different seasons. Results from this study can help target future Living Dock locations which will provide the best environment for the recruitment of filter feeding organisms. [ABSTRACT FROM AUTHOR]

Meiofauna is a group of heterotrophic organisms smaller than macroinvertebrates but larger than microfauna and characterized by groups such as testate amoebae, ciliates, and nematodes. They are a link between bacteria and resources and macroinvertebrates. However, tropical meiofauna is poorly studied; thus, our goal was to characterize meiofaunal community composition and abundance and assess potential environmental variables controlling these community dynamics. Monthly samplings of meiofauna were conducted for eight months in Quebrada Prieta, El Yunque National Forest, Puerto Rico. Sampling was made in 12 pools, and data on discharge, sediment characteristics, and biotic variables were also collected. A total of 62 meiofaunal morphospecies were identified, with nematodes dominating the community, followed by testate amoebae. Bacterivores and detritivores taxa dominated the community. Meiofaunal abundance was negatively related to discharge and positively to the percentage of coarse sand, nitrate, and macroinvertebrate abundance. The composition of meiofauna in Quebrada Prieta is like the composition reported for temperate streams, at least in major meiofaunal groups present. However, the community in Quebrada Prieta was dominated by testate amoebae. In contrast, temperate streams are often dominated by rotifers and nematodes. Both abiotic and biotic variables are important for meiofaunal communities in the headwater streams in Puerto Rico. [ABSTRACT FROM AUTHOR]

Trace elements in aquatic ecosystems are considered as major pollutants due to their environmental persistence, toxicity and ability to be incorporated into food webs. Contaminated sediments represent a threat to benthic macroinvertebrates which in turn expose high trophic organisms to hazardous trace elements, therefore metals accumulated in benthic organisms can also be bio concentrated in food webs. Direct toxic effects of metals include changes in diversity and abundance of benthic invertebrates while, indirect effects include modifications of species interactions and reductions in food quality. In this work, we study the potentially toxic metal concentrations in both sediments and benthic macroinvertebrates in the Maipo River basin (central Chile) evaluating the risk assessment of sediment, toxicity to the biota and bioaccumulation in the organisms. Sediments and benthic organisms were sampled in spring (October-December) 2016 from four sites of the Maipo River basin. Twelve trace elements (As, Al, Cd, Cu, Cr, Hg, Fe, Mn, Mo, Ni, Pb and Zn) were determined by AAE. The Geo accumulation index showed that Zn was moderate to strong pollute in all sites and the enrichment factor showed that there were no important anthropic impacts in the river. High level of contamination was found for Cu in PEL and the pollution index showed that PEL was extremely polluted. Three (Cu, Mn and Zn) out of the five metals analyzed were the elements which presented the largest toxicity to organisms in these aquatic systems based on the Threshold Effect Concentration (TEC) and Probable Effect Concentration (PEC) analysis. Most of the metals analyzed did not show bioaccumulation; however, Ni and Pb were the metals with the highest bioaccumulation factor in all the studied sites. [ABSTRACT FROM AUTHOR]

Internal solitary waves (ISWs) exert a significant influence on the deep-sea floor, yet little research has been conducted on their impact on benthic organisms. The objective of this study was to investigate the propagation characteristics of ISWs on the Shenhu continental slope in the northern South China Sea, as well as their mechanisms of influence on benthic activity. In-situ observation was performed at the head of the Shenhu Canyon (water depth 655m) to determine the physical characteristics of ISWs and the changes in benthic organisms. The study revealed that the abundance and density of benthic organisms were positively correlated with the time and intensity of ISWs. The abundance of benthic organisms affected by ISWs is 3-5 times that without ISWs, and the density of benthic organisms is 3-9 times. The impact induced by ISWs, including resuspension of bottom sediments, formation of marine snow, changes in the bottom boundary layer environment, and vertical transfer of seawater environmental factors, played a crucial role in the impact on benthic activity. To our limited knowledge, this is the first in-situ long-term observation study on the effects of ISWs on deep-sea benthic organisms on the continental slope of the northern South China Sea deeper than 600m, providing new insights for exploring the environmental impact of ISWs on the deep-sea bottom boundary layer.

In an era of accelerating biological globalization and climatic warming, it is vital to understand how introduced species integrate. Pacific Manila clams Ruditapes philippinarum were introduced for aquaculture to Europe in the 1970s, spread and became harvested from the Mediterranean Sea to British coasts. From the Dutch Rhine Delta, Manila clams immigrated stepwise into the southern Wadden Sea, and by long distance jump dispersal they arrived in the northern Wadden Sea in the 2010s. Encounters remained few until 2021, when live clams were often found in intertidal seagrass beds and around mixed beds of Pacific oysters with native mussels. Shell lengths reached up to 74 mm with a longevity of 7–8 years. Adult abundances remained low (<10 clams m−2), although larval numbers substantially increased in 2022 and 2023. Strong predation on spat may constitute ecological resistance to the immigrant. Haplotype diversity at mtDNA COI gene fragments is high and its composition is mixed from dominant haplotypes of other European sites, suggesting multiple introductions or an unknown source with an already mixed population. Currently, this is the most northern (55° N) population of R. philippinarum in continental Europe, but with the rapid expansion of this genetically variable population, further northward spread can be expected. [Display omitted] • The Manila clam arrived in the European Wadden Sea in the early 2010s. • Two independent routes of immigration into the Wadden Sea. • Genetic comparisons leave the question of a donor population unresolved. • Population development commenced slowly and spat probably meets predatory resistance. • The Wadden Sea population represents the northern frontier in the European range. [ABSTRACT FROM AUTHOR]

Differences and similarities between spiny lobster' sexes diet could result from multifactorial environmental influence. We evaluated the trophic spectrum for Panulirus argus, estimated lobster's selectivity, and corroborated the hypothesis that lobster' sexes diet is similar between subzones with different benthic community in two fishing subzones of the gulf of Batabano, Cuba. Stomach contents of 52 lobsters from Diego Pérez (DP), and 68 from Aguardiente (AA), were analyzed. Frequency of occurrence (FO), gravimetric (G), and relative importance (IIR) indices were calculated for each food category. Ellenberg Similarity (ISe), Morisita, and Ivlev Selectivity (E) indices were also applied. Different diet descriptors were also related to benthic community attributes also used to compare between subzones and sexes. Trophic spectrum for P. argus consisted of gastropods, bivalves, polyplacophores, sea urchins, stomatopods, brachyurans, anomurans, polychaetes, ophiuroids, sponges, foraminifera, hydrozoans, fish, and plant matter. The E index showed a P. argus positive selectivity for gastropods Costoanachis sp., Diodora sp., Lucapina sp., Rissoina sp., Fasciolaria tulipa, and Gibberula fluctuata, the bivalves Arcopsis sp., Barbatia domingensis, Antillipecten antillarum, and Codakia orbicularis, and crustaceans of the Order Stomatopoda. Selectivity was highest but negative for Pinctada imbricata, Tucetona pectinata, Chione sp., and anomurans. Diet between sexes was similar in DP (ISe = 47.1%) and the same in AA (ISe = 97.6%), both with high trophic level overlap. Lobster's diet descriptors and the diet for each sex were similar (medium level) between subzones, while the attributes of the benthic community were different. Similarities between diets for each sex were kept despite differences in benthic community-specific composition. [ABSTRACT FROM AUTHOR]

Although sediments are important reservoirs of plastics, most of the ecotoxicological studies on these contaminants are focused on the organisms living in the water column, while only a smaller number of evidence concerns the plastic impact on benthic species. Therefore, this study compared the multigenerational effects on the sediment-dwelling midge Chironomus riparius exposed to both virgin polystyrene microbeads (22,400-224,000 plastics/kg sediments dry weight), and plastic mixtures (40-420 plastics/kg dry weight) collected from four of the main tributaries of Po River (Ticino, Adda, Oglio and Mincio Rivers, Northern Italy) to evaluate the role played by other characteristics related to these physical contaminants in determining their toxicity as opposed to concentration alone. The modified Chironomid Life-Cycle Toxicity Test (OECD 233) was used to evaluate the multigenerational effects on the Emergence and Development Rates, Fecundity and Fertility. In addition, a biomarkers' suite of cellular stress, neurotoxicity, and energetic metabolism was applied in the 2 nd generation (2 nd /3 rd instar of larvae) to investigate the potential mechanisms associated to the apical effects. Our results showed no significant (p > 0.05) multigenerational effect for any of the endpoints tested for the virgin plastics' exposures. Coherently, no significant effects on biomarkers were measured. Concerning the sampled plastics, the particles collected in Adda River instead induced a significant decrease (p < 0.05) of the Emergence Rate in the 2 nd generation, suggesting that this parameter was the most susceptible among those measured. These results highlight that the different plethora of polymers, sizes and shapes of plastics sampled in natural ecosystems, compared to homogeneous characteristics of virgin polystyrene microbeads, appears to have considerable importance over concentration alone in determining the toxicity of these emerging contaminants., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Riccardo Sbarberi reports financial support was provided by Italian Ministry of University and Research (PhD fellowship). If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Simple Summary: The sediments on the seafloor are inhabited by multiple macroscopic organisms such as shells and worms, which, among other things, influence the biogeochemical cycling by flushing the near-bottom water through their gangways. This is called bioirrigation, one of key processes in the functioning of marine sediments. The density of animals, in addition to the features (or traits) of each species, define their specific contributions to this process. Measuring the intensity of this rather dynamic process in nature is difficult and costly; therefore, the available direct observations are too scarce for large-scale assessments. However, such assessments are essential for broadening our understanding of ecosystem functioning, and of the role that biodiversity plays in it. To address this shortage of observational data, a traits-based index "BIPc" that expresses the bioirrigation potential, based on available data on sediment-dwelling animals, comes into play. In this paper, we focus on the performance of the BIPc index in the south-western Baltic Sea, and on how it changes in space and time. The results support the usefulness of this index, but also highlight its existing limitations. Modelled distribution map layers of the bioirrigation potential and scores for 120 key species required for index calculation are made available for reuse. Benthic community bioirrigation potential (BIPc), an index developed to quantify the anticipated capacity of macrofauna to influence the solute exchange at the sediment–water interface, was calculated for the south-western Baltic Sea. This index can be regarded as an effect trait that is useful for predicting ecosystem processes impacted by animal burrow ventilation. The special feature, and presumably an advantage, of BIPc, compared to alternative recently developed benthic macrofauna-based bioirrigation indices, lies in its ability to distinguish the taxa-specific score values between diffusion- and advection-dominated sediment systems. The usefulness of the BIPc index was compared against the estimates of the well-established community bioturbation potential index (BPc). The BIPc index displayed a moderately but significantly stronger correlation with estimates of irrigation rates derived from tracer experiments. Using a random forest machine learning approach and a number of available relevant environmental predictor layers, we have modelled and mapped the spatial differences in this ecosystem functioning expression. The key species contributing to bioirrigation potential in the study area were identified. The interannual variation in BIPc was assessed on a small exemplary dataset. The scores required to calculate the index, that were assigned to 120 taxa dominating abundance and biomass in the region, are provided for reuse. The utility, temporal variability and uncertainty of the distribution estimate are discussed. [ABSTRACT FROM AUTHOR]

Featured Application: A simple model was developed to select indicator species based on individual species' contributions to biodiversity. Targeting biodiversity can be used for environmental monitoring and to inform restoration designs. In both ecological research and engineering, the selection of indicator species is crucial. Biodiversity has always been an important policy objective for ecologists and environmental managers. Based on this target requirement, we developed a method that reveals the individual contributions of species to biodiversity to quantitatively identify indicator species for selection during environmental monitoring. The Siangshan Wetland in Hsinchu, Taiwan, was selected as an application case. The spread of mangroves not only changed the original habitat composition and function of benthic organisms in wetlands, but also led to problems such as estuary filling, flooding, and black mosquito breeding. Therefore, a large-scale mangrove removal project was undertaken by the Hsinchu City Government from October 2015 to March 2016. In this study, the biological effects of mangrove removal on benthic organisms and adjacent habitats were investigated from October 2015 to September 2016. According to biodiversity contribution algorithms, we identified five indicator species, namely, Mictyris brevidactylus, Macrophthalmus banzai, Uca arcuata, U. lacteal, and U. borealis. These indicator species had the most prominent biodiversity contribution, and they provided direct evidence of the beneficial effect of mangrove removal for wetland restoration. After mangrove deforestation, tidal flat species returned to their original habitats, and their related densities increased significantly in mangrove removal areas. Improving our understanding of the relationships between biodiversity and indicator species is crucial for the development of coastal management processes. Mangrove removal can be confirmed as an appropriate habitat rehabilitation strategy for benthic organisms. Consequently, these indicator species and the results obtained can provide valuable ecological information for those involved in coastal management or other officials seeking to control the spread of mangroves. [ABSTRACT FROM AUTHOR]

Climate change is impacting organisms in every region of the world ocean by acting though on individuals in response to their local environments. Given projected future risks derived from these changes, it is becoming increasingly important to understand regional signals of how organisms respond to facilitate their governance and protection. Benthic organisms structure ecological compositions and ecosystem dynamics, therefore not only providing insights into their own response to climate change but also how ecosystems might respond to future conditions. European seas are transitional areas including boreal, warm-temperate, and subarctic waters with organisms frequently at limits of their distributions. Here, we use a meta-analytical approach to assess how calcification, growth, metabolism, photosynthesis, reproduction, and survival in European benthic organisms respond to ocean acidification and warming. Using meta-regression, we examine how study design factors influence effect-size outcomes. Longer experimental periods generally amplified the effects of climate change on taxonomic groupings and related physiological traits and against expectation do not result in acclimation. In agreement with global studies, we find that impacts vary considerably on different taxonomic groupings and their physiological traits. We found calcifying organisms are an at-risk taxon in European waters, with climate stressors decreasing growth rates, reproduction, and survival rates. Fleshy algal species demonstrate resilience to climate stressors, suggesting future European benthic ecosystems will undergo restructuring based on current climate emission pathways.

Non‐random community changes are becoming more frequent in many ecosystems. In coral reefs, changes towards communities dominated by other than hard corals are increasing in frequency, with severe impacts on ecosystem functioning and provision of ecosystem services. Although new research suggests that a variety of alternative communities (i.e. not dominated by hard corals) exist, knowledge on the global diversity and functioning of alternative coral reef benthic communities, especially those not dominated by algae, remains scattered. In this systematic review and meta‐analysis of 523 articles, we analyse the different coral reef benthic community changes reported to date and discuss the advantages and limitations of the methods used to study these changes. Furthermore, we used field cover data (1116 reefs from the ReefCheck database) to explore the biogeographic and latitudinal patterns in dominant benthic organisms. We found a mismatch between literature focus on coral‐algal changes (over half of the studies analysed) and observed global natural patterns. We identified strong biogeographic patterns, with the largest and most biodiverse biogeographic regions (Western and Central Indo‐Pacific) presenting previously overlooked soft‐coral‐dominated communities as the most abundant alternative community. Finally, we discuss the potential biases associated with methods that overlook ecologically important cryptobenthic communities and the potential of new technological advances in improving monitoring efforts. As coral reef communities inevitably and swiftly change under changing ocean conditions, there is an urgent need to better understand the distribution, dynamics as well as the ecological and societal impacts of these new communities. [ABSTRACT FROM AUTHOR]

The use of living organisms to provide information on the quality of aquatic environments is now a widely accepted methodology for assessing contaminant bioavailability. Molluscs have developed tolerance mechanisms towards environmental stressors and can accumulate a large range of contaminants. The assessment of marine environment quality was based on heavy metals (HM), persistent organic pollutants (organochlorine pesticides - OCPs and polychlorinated biphenyls - PCBs) and polynuclear aromatic hydrocarbons (PAHs) analysis in Mytilus galloprovincialis, Rapana venosa, Anadara kagoshimensis species sampled during 2016 - 2020 along Romanian Black Sea coast. Toxic metals (cadmium, lead) had bioaccumulation levels below threshold values in most molluscs samples investigated. Cadmium registered few values (15%) surpassing maximum admissible levels, in all three species. Data evaluation demonstrated the maintenance of a high level of concentrations of persistent organic pollutants in the mollusc tissue, but also of the exceedances of the values that characterize the good ecological status of these compounds. Polynuclear aromatic hydrocarbons showed a declining trend and no exceeding of the maximum allowed limit for benzo[a]pyrene was recorded in the last years. In consequence, the overview assessment based on "OneOutAllOut" (OOAO) approach, considering all groups of substances, indicates a bad chemical status for this period. [ABSTRACT FROM AUTHOR]

Abstract As part of efforts to restore fishery resources and recover damaged coastal ecosystems, artificial reefs are often anchored on the seafloor in coastal zones, to provide new habitats for marine organisms. The aim of the study was to describe the structure of a community of benthic invertebrates colonising a niche-type artificial reef (AATN in Spanish). Nine structures were anchored at depths of 16 ± 1.5 m for 99 weeks (22 months) in the Area of Benthic Resource Management and Exploitation (AMERB) in coastal waters of the Region of Bio Bio, Chile. The results showed that, at 3 months from submersion of the NTAR, much of the artificial substrate remained bare and there were only low levels of specimens of Balanus sp. barnacles, showing mean coverage of 11.26%, and even lower proportions of Rhodophyta, with mean coverage of 0.34%. At 6 months, the presence of hydrozoans was seen, decreasing the coverage of the barnacles, which was aided further at 8 months with the arrival of barnacle predatory invertebrates. At 8 months, new benthic invertebrates appeared and competed for the substrate. These included sponges and algae. At 99 weeks, the hydrozoans dominated the substrate, followed by barnacles and Rhodophyta, the first colonising organisms, leading to colonisation by motile macro-invertebrates, mainly consisting of crustaceans, echinoderms and molluscs. The AATN artificial system provides an ideal substrate for the development of early ecological succession and the use of this technology should be feasible in the recovery process of habitat damaged by anthropogenic actions and climate change.

It is imperative to understand the carbon (C) and nitrogen (N) pools in tropical mangrove systems considering the diminished C storage potential and increasing nutrient loading in a global context due to rising anthropogenic disturbances. Here, we report that the Mangalavanam Coastal Wetland (MCW), a tropical mangrove stand, is a C‐rich environment, with high sediment total organic carbon (70.35 ± 23.84 mg/g) and the δ13C (−26.56 ± 0.65‰) signatures indicate that the major source of carbon in the study area is from mangrove litter. The total nitrogen concentration in the sediment (3.78 ± 0.18 mg/g) was high despite the low N environment of mangrove ecosystems where the mangrove leaf litter was a major contributor to C. The sediment δ15 N (7.70 ± 0.23‰) signatures indicated that the influence of anthropogenic N discharges and the contribution of marine algae were the primary cause of N enrichment. The mean δ13C and δ15N signatures of the mature mangrove leaves of the MCW were −28.66 ± 1.04‰ and 5.93 ± 0.65‰, respectively. The mangrove dweller crab Parasesarma plicatum was observed to have enriched δ13C (−23.78 ± 0.33‰) and δ15N (6.54 ± 0.35‰) signatures, indicative of a mixed dietary source. This study provides the impetus for ongoing conservation efforts to limit the loss of carbon storage and protect against the impact of anthropogenic nitrogen loadings on lowering the carbon and nitrogen emission potential for this system, which can have implications for other tropical mangrove systems as well. [ABSTRACT FROM AUTHOR]

A comprehensive monitoring and risk assessment of arsenic (As) pollution concerning surface water and sediment is performed in the Jie River basin, where gold smelting enterprises are concentrated. The study area is divide into six regions, labeled as A, B, C, D, E, and F, from sewage outlets to downstream. Results shows that with far away from the sewage outlets, the total As concentrations in water and sediment gradually decrease from regions A to F. However, in region F, the concentration of bioavailable As significantly increases in the sediment due to the higher pH, leading to the transformation of As(V) into more mobile As(III). In sediment, Paracladius sp. exhibits strong resistance to As pollution in sediment, which can potentially elevate the risk of disease transmission. In water bodies, diatoms and euglena are the main phytoplankton in the Jie River while toxic cyanobacteria exhibits lower resistance to As pollution. Overall, measures should be taken to ecologically remediate the sediment in downstream while implementing appropriate isolation methods to prevent the spread of highly contaminated sediments from regions near sewage outlets. [Display omitted] • Total As may not be consistent with bioavailable As due to pH and geology. • Diatoms and euglena exhibit strong resistance to As pollution while cyanobacteria not. • Paracladius sp. exhibits strong resistance to As pollution in sediment. [ABSTRACT FROM AUTHOR]

Benthic community bioirrigation potential (BIPc), an index developed to quantify the anticipated capacity of macrofauna to influence the solute exchange at the sediment–water interface, was calculated for the south-western Baltic Sea. This index can be regarded as an effect trait that is useful for predicting ecosystem processes impacted by animal burrow ventilation. The special feature, and presumably an advantage, of BIPc, compared to alternative recently developed benthic macrofauna-based bioirrigation indices, lies in its ability to distinguish the taxa-specific score values between diffusion- and advection-dominated sediment systems. The usefulness of the BIPc index was compared against the estimates of the well-established community bioturbation potential index (BPc). The BIPc index displayed a moderately but significantly stronger correlation with estimates of irrigation rates derived from tracer experiments. Using a random forest machine learning approach and a number of available relevant environmental predictor layers, we have modelled and mapped the spatial differences in this ecosystem functioning expression. The key species contributing to bioirrigation potential in the study area were identified. The interannual variation in BIPc was assessed on a small exemplary dataset. The scores required to calculate the index, that were assigned to 120 taxa dominating abundance and biomass in the region, are provided for reuse. The utility, temporal variability and uncertainty of the distribution estimate are discussed.

In both ecological research and engineering, the selection of indicator species is crucial. Biodiversity has always been an important policy objective for ecologists and environmental managers. Based on this target requirement, we developed a method that reveals the individual contributions of species to biodiversity to quantitatively identify indicator species for selection during environmental monitoring. The Siangshan Wetland in Hsinchu, Taiwan, was selected as an application case. The spread of mangroves not only changed the original habitat composition and function of benthic organisms in wetlands, but also led to problems such as estuary filling, flooding, and black mosquito breeding. Therefore, a large-scale mangrove removal project was undertaken by the Hsinchu City Government from October 2015 to March 2016. In this study, the biological effects of mangrove removal on benthic organisms and adjacent habitats were investigated from October 2015 to September 2016. According to biodiversity contribution algorithms, we identified five indicator species, namely, Mictyris brevidactylus, Macrophthalmus banzai, Uca arcuata, U. lacteal, and U. borealis. These indicator species had the most prominent biodiversity contribution, and they provided direct evidence of the beneficial effect of mangrove removal for wetland restoration. After mangrove deforestation, tidal flat species returned to their original habitats, and their related densities increased significantly in mangrove removal areas. Improving our understanding of the relationships between biodiversity and indicator species is crucial for the development of coastal management processes. Mangrove removal can be confirmed as an appropriate habitat rehabilitation strategy for benthic organisms. Consequently, these indicator species and the results obtained can provide valuable ecological information for those involved in coastal management or other officials seeking to control the spread of mangroves.

Seawater reverse osmosis (SWRO) desalination facilities produce freshwater and, at the same time, discharge hypersaline brine that often includes various chemical additives such as antiscalants and coagulants. This dense brine can sink to the sea bottom and creep over the seabed, reaching up to 5 km from the discharge point. Previous reviews have discussed the effects of SWRO desalination brine on various marine ecosystems, yet little attention has been paid to the impacts on benthic habitats. This review comprehensibly discusses the effects of SWRO brine discharge on marine benthic fauna and flora. We review previous studies that indicated a suite of impacts by SWRO brine on benthic organisms, including bacteria, seagrasses, polychaetes, and corals. The effects within the discharge mixing zones range from impaired activities and morphological deformations to changes in the community composition. Recent modeling work demonstrated that brine could spread over the seabed, beyond the mixing zone, for up to several tens of kilometers and impair nutrient fluxes from the sediment to the water column. We also provide a possible perspective on brine's impact on the biogeochemical process within the mixing zone subsurface. Desalination brine can infiltrate into the sandy bottom around the discharge area due to gravity currents. Accumulation of brine and associated chemical additives, such as polyphosphonate-based antiscalants and ferric-based coagulants in the porewater, may change the redox zones and, hence, impact biogeochemical processes in sediments. With the demand for drinking water escalating worldwide, the volumes of brine discharge are predicted to triple during the current century. Future efforts should focus on the development and operation of viable technologies to minimize the volumes of brine discharged into marine environments, along with a change to environmentally friendly additives. However, the application of these technologies should be partly subsidized by governmental stakeholders to safeguard coastal ecosystems around desalination facilities.

This brief research compares the bioconcentration of heavy metals (Cd, Cr, Cu, Pb, Ni, and Zn) in the soft tissues of native oysters Crassostrea rhizophorae (Guilding, 1828) from two areas in the Potengi estuary, northeastern coast of Brazil. The purpose was to test the hypotheses of relevant differences in bioaccumulation while the environmental conditions change upstream. The downstream station showed higher concentrations for cadmium and nickel, and the upstream one revealed increased values for body weight, condition index, chromium, lead, and zinc (p < 0.05). The copper variation between sites was negligible, but as for zinc and chromium, the metal content observed was above guidance levels. Results revealed two aspects that were mainly influencing the bioavailability and bioaccumulation of metals in oysters. First, the predominance of marine or riverine characteristics of each site, and second, the relative proximity to the point of introduction of the pollutant even though stations were not quite far apart. C. rhizophorae accumulated heavy metals in significant concentrations, endorsing its efficiency as a biomonitor.

As part of efforts to restore fishery resources and recover damaged coastal ecosystems, artificial reefs are often anchored on the seafloor in coastal zones, to provide new habitats for marine organisms. The aim of the study was to describe the structure of a community of benthic invertebrates colonising a niche-type artificial reef (AATN in Spanish). Nine structures were anchored at depths of 16 ± 1.5 m for 99 weeks (22 months) in the Area of Benthic Resource Management and Exploitation (AMERB) in coastal waters of the Region of Bio Bio, Chile. The results showed that, at 3 months from submersion of the NTAR, much of the artificial substrate remained bare and there were only low levels of specimens of Balanus sp. barnacles, showing mean coverage of 11.26%, and even lower proportions of Rhodophyta, with mean coverage of 0.34%. At 6 months, the presence of hydrozoans was seen, decreasing the coverage of the barnacles, which was aided further at 8 months with the arrival of barnacle predatory invertebrates. At 8 months, new benthic invertebrates appeared and competed for the substrate. These included sponges and algae. At 99 weeks, the hydrozoans dominated the substrate, followed by barnacles and Rhodophyta, the first colonising organisms, leading to colonisation by motile macro-invertebrates, mainly consisting of crustaceans, echinoderms and molluscs. The AATN artificial system provides an ideal substrate for the development of early ecological succession and the use of this technology should be feasible in the recovery process of habitat damaged by anthropogenic actions and climate change. [ABSTRACT FROM AUTHOR]

A comparative analysis of the current content of petroleum hydrocarbons in various components of the ecosystem was performed to assess the ecological state of the southeastern part of the Onega Bay (White Sea) that suffered from a spill of fuel oil in 2003. The analysis showed relatively low levels of petroleum hydrocarbon concentrations: from 0.34 to 4.55 mg/kg, with a median of 1.41 mg/kg in bottom sediments; from 9.41 to 14.25 mg/kg, with a median of 12.30 mg/kg in tissues of benthic organisms; and below 1 MPCfishery (the maximum permissible concentration) in water. The records of low concentrations of bacteria that use petroleum hydrocarbons (fuel oil) allow us to conclude that the state of the examined ecosystem is close to the natural condition. [ABSTRACT FROM AUTHOR]

Microplastics have accumulated in the environment since plastic production began, with present-day observations that range from marine trenches to mountains. However, research on microplastics has only recently begun so it is unclear how they have changed over time in many oceanic regions. Our study addressed this gap by quantifying the temporal and spatial dynamics of microplastics in two deep-water regions of the Gulf of Mexico (GOM). We isolated agglutinated foraminifera from sediment cores and assessed microplastics that were incorporated into their tests. Our results indicated that microplastics were incorporated by agglutinated foraminifera after plastic production began. Microplastics were higher at deep-water sites and closer to the Mississippi River. This study confirms the presence of microplastic incorporation into agglutinated foraminifera tests and investigates microplastics in deep-water sediments in the GOM. Additional work is needed to fully identify the distribution of microplastics across the GOM and other oceanic basins. • Agglutinated foraminifera non-selectively incorporated microplastics into tests. • Microplastics were mostly incorporated into larger foraminifera. • Microplastics were higher post-plastic production. • Microplastics were higher closer to the Mississippi River. • Microplastics were higher in deeper waters. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are widely found in the ocean and cause a serious risk to marine organisms. However, fewer studies have been conducted on benthic organisms. This study conducted a case study on the pollution characteristics of MPs on 16 marine benthic organisms in Haizhou Bay, and analyzed the effects of habitat, trophic level, and feeding mode on the MPs pollution characters. The results showed that MPs were detected in all 16 organisms with an average abundance of 8.84 ± 9.14 items/individual, which is in the middle-high level in the international scale. Among the detected MPs, the main material was cellophane. This study showed that benthic organisms can be used as indicator organisms for MPs pollution. MPs in organisms can be affected by their habitat, trophic level, and feeding mode. Comprehensive analysis of MPs in benthic organisms will contribute to fully understand the characterization and source resolution of MPs pollution. [Display omitted] • Widespread presence of MPs in benthic organisms in Haizhou Bay. • Habitat, feeding mode, and trophic level all affect the abundance of MPs in benthic organisms. • Benthic organisms can be used as indicator organisms for MPs pollution. [ABSTRACT FROM AUTHOR]

This paper presents an approach for incorporating species-conditional co-occurrence into models used for the selection of marine indicator species. Mangrove invasion within the Siangshan Wetland in Hsinchu, Taiwan, has changed the original structures and functions of habitats for benthic organisms. The Hsinchu City Government ran a large-scale mangrove removal project from October 2015 to March 2016 to restore the wetland. From October 2015 to September 2016, we investigated the biological effects of mangrove removal on benthic crabs and their adjacent habitats. Density, number of species, Shannon–Weaver index (H′) and Palou’s evenness index (J′) were calculated and compared between mangrove and non-mangrove regions. The results showed that values for these attributes in the non-mangrove regions were higher than those of the mangrove regions. After mangrove removal, species returned to their original habitats and the related density increased significantly. Using conditional co-occurrence algorithms, we identified five indicator species (Mictyris brevidactylus, Macrophthalmus banzai, Uca arcuata, Uca lacteal and Uca borealis) with high co-occurrence probabilities, whose population responses provided direct evidence of the benefits of mangrove removal for wetland restoration. The results indicate that mangrove removal is an appropriate habitat rehabilitation strategy for benthic organisms, and that the chosen indicator species may provide valuable ecological information for coastal managers seeking to control the spread of mangroves.

We use a linear stability approach to develop a process-based morphodynamic model including a two-way coupling between tidal sand wave dynamics and benthic organisms. With this model we are able to study both the effect of benthic organisms on the hydro- and sediment dynamics, and the effect of spatial and temporal environmental variations on the distribution of these organisms. Specifically, we include two coupling processes: the effect of the biomass of the organisms on the bottom slip parameter, and the effect of shear stress variations on the biological carrying capacity. We discuss the differences and similarities between the methodology used in this work and that from 'traditional' (morphodynamics only) stability modelling studies. Here, we end up with a 2 × 2 linear eigenvalue problem, which leads to two distinct eigenmodes for each topographic wave number. These eigenmodes control the growth and migration properties of both sand waves and benthic organisms (biomass). Apart from hydrodynamic forcing, the biomass also grows autonomously, which results in a changing fastest growing mode (FGM, i.e. the preferred wavelength) over time. As a result, in contrast to 'traditional' stability modelling studies, the FGM for a certain model outcome does not necessarily have to be dominant in the field. Therefore, we also analysed the temporal evolution of an initial bed hump (without perturbing biomass) and of an initial biomass hump (without perturbing topography). It turns out that these local disturbances may trigger the combined growth of sand waves and spatially varying biomass patterns. Moreover, the results reveal that the autonomous benthic growth significantly influences the growth rate of sand waves. Finally, we show that biomass maxima tend to concentrate in the region around the trough and lee side slope of sand waves, which corresponds to observations in the field. [ABSTRACT FROM AUTHOR]

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While the study of dispersal and connectivity in the ocean typically centres on pelagic species and planktonic larval stages of benthic species, the present work explores an overlooked locomotor means in post‐settlement benthic stages that redefines their dispersal potential.Members of the echinoderm class Holothuroidea colonize a diversity of marine environments world‐wide, where they play key ecological and economical roles, making their conservation a priority. Holothuroids are commonly called sea cucumbers or sea slugs to reflect their slow movements and are assumed to disperse chiefly through pelagic larvae.The present study documents and explores their unexpected ability to actively modify their buoyancy, leading them to tumble or float at speeds orders of magnitudes faster than through benthic crawling. Two focal species representing different taxonomic orders, geographic distributions and reproductive strategies were studied over several years.Active buoyancy adjustment (ABA) was achieved through a rapid increase in water‐to‐flesh ratio by up to 740%, leading to bloating, and simultaneously detachment from the substrate. It occurred as early as 6 months post settlement in juveniles and was recorded in wild adult populations. In experimental trials, ABA was triggered by high conspecific density, decreasing salinity and increasing water turbidity. Based on field video footage, ABA‐assisted movements generated speeds of up to 90 km/day.These findings imply that displacement during planktonic larval stages may not supersede the locomotor capacity of benthic stages, challenging the notion of sedentarity. Combining the present results and anecdotal reports, ABA emerges as a generalized means of dispersal among benthic animals, with critical implications for world‐wide management and conservation of commercially and ecologically significant species. [ABSTRACT FROM AUTHOR]

Antifouling paint particles (APPs) of between 500 μm and >2 mm in diameter have been identified in silty, intertidal estuarine sediments through a combination of microscopy and x-ray fluorescence spectrometry. APPs were heterogeneously distributed, with maximal concentrations of 430 particles L−1 (0.2 g L−1) near to a facility where boats are regularly maintained and 400 particles L−1 (4.2 g L−1) at a location where old boats had been abandoned, with the majority of particles encountered in the finest size fraction retrieved. APPs contained variable concentrations of Cu, Zn, Sn and Pb, with respective maxima of 562,000, 269,000, 9,970 and 126,000 mg kg−1. These characteristics are attributed to a multitude of contemporary and historic sources of an assortment of formulations and result in significant but heterogeneous metal contamination of local sediments. APPs were also identified in the guts of the deposit-feeding ragworm, Hediste diversicolor , that inhabited sediments impacted by abandoned boats or boating activities. The tissue of H. diversicolor was particularly enriched in Cu where ingested APPs were observed, with a significant correlation between dry weight Cu concentrations in the two media (r = 0.734) presumably reflecting the inability of the animal to regulate this metal. While the toxicity of APPs requires further investigation, there is clearly a need for stricter regulations on antifouling wastes in boatyards and marinas and a requirement to better manage abandoned boats. Image 1 • Antifouling paint particles (APPs) are a source of metals to the marine environment. • APPs were abundant in estuarine sediment impacted by boating activities. • APPs were identified in the guts of the deposit-feeder, Hediste diversicolor. • APPs result in elevated metal concentrations in sediment and H. diversicolor. Antifouling paint particles in contaminated estuarine sediments can be ingested by Hediste diversicolor and result in the bioaccumulation of copper. [ABSTRACT FROM AUTHOR]

The present study assessed biochemical responses as sublethal endpoints in the polychaete Armandia agilis exposed to contaminated sediments to in order to assess its potential use as a test organism. Sediment samples from several locations at a dredging site were obtained and used in whole-sediment exposures. Samples were tested with A. agilis to determine the 10-day toxicity of the 100% sample and the enzymatic activity of catalase (CAT), glutathione-S-transferase (GST) and acetylcholinesterase (AChE) biochemical measurements made in whole-body homogenates of a subset of the surviving organisms. Biochemical responses reported in A. agilis were not statistically different from the reference site sediment, however, the integrated analysis demonstrated that contaminants bound to sediment samples influenced the sublethal effects. [ABSTRACT FROM AUTHOR]

This study aimed to examine the benthic structure of Guanabara Bay's (GB) rocky shores through Functional Diversity (FD) perspective. Over a five-year period, benthic communities were periodically examined using photographic samples from the meso-littoral zone. FD were analysed using the Rao Index of marine macroalgae and benthic invertebrates' functional groups (FGs) and their relationship was investigated through null models, considering temporal, geographical, and environmental variations. The entrance site exhibited exclusive FGs and overlap niches more than expected by chance, while the inner site had a higher frequency of Bacterial Biofilm and predominance of competitive exclusion. Orthophosphate and nitrate showed significant correlations with FGs inside the bay, whereas average irradiance and rainfall were at the entrance. A functional gradient was registered, with higher Rao's Index values at the entrance compared to the inner site, probably due to increased anthropogenic disturbance and abundance of FGs with opportunistic life strategies inside GB. [Display omitted] • Rao Index efficiently assessed Guanabara Bay's rocky shores' functional structure. • Functional gradient was recorded at Guanabara Bay using benthic functional groups. • Functional groups had niche overlap and competitive exclusion in different sites. • Abiotic factors were differently correlated with functional groups in the sites. • Results emphasized the impact of anthropogenic disturbance on the bay's dynamic. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are recognized as an increasing threat to the marine environment, but little is known about their effects on benthic organisms, including sea urchins, when ingested. For this purpose, wild sea urchins (P. lividus) and seafloor sediment samples were investigated across three coastal areas of Zakynthos Island (Ionian Sea), each exposed to different anthropogenic pressures, revealing a consistent pattern in MP abundance, shape, and color. Biomarkers related to oxidative stress, neurotoxicity, and genotoxicity showed no significant effects of MP ingestion in the sea urchins, except for a positive correlation between GST activity and ingested MPs, suggesting a possible activation of their detoxification system in response to MP ingestion. While MP concentrations in sea urchins and sediments were within the low range reported in the global literature, it remains crucial to conduct further investigations in areas with MP pollution approaching predicted levels to fully comprehend the potential effects of MP pollution on marine organisms. [Display omitted] • Low microplastic abundance in sediments and sea urchins in Zakynthos Island • Blue fibers dominate in both sediments and sea urchins. • Microplastic ingestion did not exhibit significant effect on sea urchins. • Positive correlation between GST activity and ingested MPs • FTIR analysis revealed majorly PP, PE, PVA in sediments and PP in sea urchins. [ABSTRACT FROM AUTHOR]

Aim. We present the findings of studies of the current state of benthic fauna of the Volga delta channels by the structure of benthic communities. The study has been carried out in the framework of researches by FSBSI "Caspian Fisheries Research Institute" conducted in the period from 2010 to 2014. The main goal was to assess the current state of benthic fauna of output channels of the Volga delta areas against the backdrop of changing water availability of the Volga river.Methods. We have conducted sample processing of zoobenthos within investigated watercourses of the Volga River according to conventional methods of Zhadin V.I. (1960), Winberg G.G. (1984) and Abakumov V.A. (1992).Results. The results of the work on the study of the modern state of the benthic fauna of the Volga delta channels show that the species composition of macrozoobenthos in these sections of the river in dry years was characterized by mass development of oligochaetes. With the increase of water content (between the years 2012 and 2013) in all studied water streams there is a change of the dominant group. With the decrease in the annual runoff (in 2014) the qualitative characteristics of zoobenthos have changed. In the average long-term aspect, the distribution pattern of quantitative indicators of benthic invertebrates in the delta of Volga river was uneven, and their greatest density has been marked in the wet year.Main conclusions. Thus, the research found that increase of the water content of the Volga River positively influences the hydrobiological picture in the output channels of the delta of the Volga River.

In early 2018, a large easterly storm hit the East Anglian coast of the UK, colloquially known as the ‘Beast from the East’, which also resulted in mass strandings of benthic organisms. There were subsequent instances of dogs consuming such organisms, leading to illness and, in some cases, fatalities. Epidemiological investigations identified paralytic shellfish toxins (PSTs) as the cause, with toxins present in a range of species and concentrations exceeding 14,000 µg STX eq./kg in the sunstar Crossaster papposus. This study sought to better elucidate the geographic spread of any toxicity and identify any key organisms of concern. During the summers of 2018 and 2019, various species of benthic invertebrates were collected from demersal trawl surveys conducted across a variety of locations in the North Sea. An analysis of the benthic epifauna using two independent PST testing methods identified a ‘hot spot’ of toxic organisms in the Southern Bight, with a mean toxicity of 449 µg STX eq./kg. PSTs were quantified in sea chervil (Alcyonidium diaphanum), the first known detection in the phylum bryozoan, as well as eleven other new vectors (>50 µg STX eq./kg), namely the opisthobranch Scaphander lignarius, the starfish Anseropoda placenta, Asterias rubens, Luidia ciliaris, Astropecten irregularis and Stichastrella rosea, the brittlestar Ophiura ophiura, the crustaceans Atelecyclus rotundatus and Munida rugosa, the sea mouse Aphrodita aculeata, and the sea urchin Psammechinus miliaris. The two species that showed consistently high PST concentrations were C. papposus and A. diaphanum. Two toxic profiles were identified, with one dominated by dcSTX (decarbamoylsaxitoxin) associated with the majority of samples across the whole sampling region. The second profile occurred only in North-Eastern England and consisted of mostly STX (Saxitoxin) and GTX2 (gonyautoxin 2). Consequently, this study highlights widespread and variable levels of PSTs in the marine benthos, together with the first evidence for toxicity in a large number of new species. These findings highlight impacts to ‘One Health’, with the unexpected sources of toxins potentially creating risks to animal, human and environmental health, with further work required to assess the severity and geographical/temporal extent of these impacts.

The Western Antarctic Peninsula (WAP) has undergone significant changes in air and seawater temperatures during the last 50 years. Although highly stenotherm Antarctic organisms are expected to be severely affected by the increase of seawater temperature, high-resolution datasets of seawater temperature within coastal areas of the WAP (where diverse marine communities have been reported) are not commonly available. Here we report on within-year (2016–2017) variation in seawater temperature at three sites on Doumer Island, Palmer Archipelago, WAP. Within a year, Antarctic organisms in South Bay were exposed to water temperatures in excess of 2 °C for more than 25 days and 2.5 °C for more than 10 days. We recorded a temperature range between −1.7° to 3.0 °C. Warming of seawater temperature was 3.75 times faster after October 2016 than it was before October. Results from this study indicate that organisms at South Bay are already exposed to temperatures that are being used in experimental studies to evaluate physiological responses to thermal stress in WAP organisms. Continuous measurements of short to long-term variability in seawater temperature provides important information for parametrizing meaningful experimental treatments that aim to assess the local effects of environmental variation on Antarctic organisms under future climate scenarios.

Sewage treatment plants in Ilha Solteira City, which consist of stabilization ponds, have been modifying water and sediment characteristics around sewage outfall area. Water quality parameters such as dissolved oxygen (OD) and conductivity were directly influenced by the sewage outfall. OD values were reported before (6.36 mg L-1) and after (2.94 mg L-1) the sewage outfall. Measurement of organic matter content in the sediment showed the same pattern, with values of 1.34% and 4.80% for the SP1 and SP3 samples, respectively. A copper and zinc analysis indicated that metals are being transported through the water column, and SP3 is an important sedimentation zone. The total concentrations reported for copper are 6.48, 26.97, 37.54, 27.12 and 18.55 mg kg-1 for SP1, SP2, SP3, SP4 and SP5, respectively, and the total concentrations for zinc are 11.21, 48.53, 67.41, 58.62 and 24.76 mg kg-1. Bureau Community of Reference (BCR) sequential extraction indicated the following bioavailability order of copper and zinc: SP1 < SP5 < SP4 < SP3 < SP2. At SP2, more than 70% of the copper and zinc is found in bioavailable fractions. Benthic organism’s analysis indicates that the Oligochaetes correlation with organic matter content is related to the decrease in water quality. DOI: http://dx.doi.org/10.17807/orbital.v7i4.777

Abstract Background Recent studies have reported that soft tunic syndrome (STS) in the edible ascidian Halocynthia roretzi is caused by the kinetoplastid parasite Azumiobodo hoyamushi. In this study, we attempted to detect and quantify the pathogen in benthic animals. Methods Four species of ascidians, three species of echinoderms, two species of bivalves, one species each of sponge and algae, as well as seawater, were collected in 2014 and 2015 from an ascidian farm on the southern coast of Korea by SCUBA diving. Samples were collected from ascidian hanging culture ropes or the sea bottom. Inhalent siphons were excised for the analysis of ascidians, and soft body tissues were excised from the other species. Membrane filters were used to filter collected seawater. Tissues and membrane filters were analysed using culture testing, PCR testing, and qPCR diagnoses. Results Only organisms belonging to Ascidiacea are susceptible to A. hoyamushi infection. The infection rate (% infected of the total number collected) and infection intensity (number of cells infected/g tissue wet weight) varied depending on the seasonal variation in seawater temperatures. Most ascidians examined were infected with A. hoyamushi and showed higher infection intensity in cold water seasons (April 2014 and February 2015), followed by a dramatic drop during warm water seasons (August and November, 2014). In addition, infection intensity of A. hoyamushi during the warm water period was higher in ascidians from the sea bottom than those from the hanging culture rope. Conclusions Among benthic organisms that inhabit the southern coast of Korea, most ascidians are susceptible to A. hoyamushi infection. Seasonal cycle of infection rates and intensities of the pathogen correspond well with the STS disappearance and onset cycle observed in ascidian farms. The high intensity of A. hoyamushi infection in the ascidians on the sea bottom of ascidian farms during summer suggest further studies on the role of the pathogen in resumption of STS occurrence in late fall or early winter in the southern coast of Korea.

The presence of potentially toxic elements (PTE) was determined in different tissues of five selected marine organisms. The As, Cd, Cu, Mn, Mo, Ni, Pb and Zn concentrations were measured in the seagrass Cymodocea nodosa , the green alga Cladophora echinus , the red alga Gelidiella lubrica , the marine topshell Phorcus turbinatus and the littoral crab Carcinus aestuarii , as well as in seawater from Makirina Bay. The levels of As, Cd, Cu, Mn and Zn in the biota were found to exceed those in previously analysed sediments, indicating the bioaccumulation of these PTE. The biota-sediment accumulation factor (BSAF) and concentration factor (CF) varied among different organisms. As regards the five selected species, C. nodosa , C. echinus and G. lubrica proved to be the strongest accumulators of Mn, while P. turbinatus and C. aestuarii showed a high capacity to accumulate As, Cd, Cu and Zn. These species can be considered as good ecological indicators in the assessment of PTE pollution in marine littoral environments. [ABSTRACT FROM AUTHOR]