Anthropogenic disturbance and biodiversity of marine benthic communities in Antarctica: a regional comparison

Oil and gas platforms degrade benthic invertebrate diversity and food web structure

Oil and gas exploitation introduces toxic contaminants such as hydrocarbons and heavy metals to the surrounding sediment, resulting in deleterious impacts on marine benthic communities. This study combines benthic monitoring data over a 30-year period in the North Sea with dietary information on >1400 taxa to quantify the effects of active oil and gas platforms on benthic food webs using a multiple before-after control-impact experiment. Contamination from oil and gas platforms caused declines in benthic food web complexity, community abundance, and biodiversity. Fewer trophic interactions and increased connectance indicated that the community became dominated by generalists adapting to alternative resources, leading to simpler but more connected food webs in contaminated environments. Decreased mean body mass, shorter food chains, and the dominance of small detritivores such as Capitella capitata near to structures suggested a disproportionate loss of larger organisms from higher trophic levels. These patterns were associated with concentrations of hydrocarbons and heavy metals that exceed OSPAR's guideline thresholds of sediment toxicity. This study provides new evidence to better quantify and manage the environmental consequences of oil and gas exploitation at sea.

Assessing the current state of plastic pollution research in Antarctica: Knowledge gaps and recommendations

Antarctica stands as one of the most isolated and pristine regions on our planet. Regardless, recent studies have evidenced the presence of plastic pollution in Antarctic environments and biota. While these findings are alarming and put into perspective the reach of plastic pollution, it is necessary to assess the current knowledge of plastic pollution in Antarctica. In the present review, an updated literature review of plastic pollution in multiple Antarctic environmental compartments and biota was conducted. Studies were cataloged based on environmental compartments (e.g., sediments, seawater, soil, atmosphere) and biota from different ecological niches. A detailed analysis of the main findings, as well as the flaws and shortcomings across studies, was conducted. In general terms, several studies have shown a lack of adequate sampling and analytical procedures for plastic research (particularly in the case of microplastics) and standard procedures; thus, compromising the reliability of the data reported and comparability across studies. Aiming to guide future studies and highlight research needs, a list of knowledge gaps and recommendations were provided based on the analysis and discussion of the literature and following standardized procedures.

Contamination of the marine environment by Antarctic research stations: Monitoring marine pollution at Casey station from 1997 to 2015

The contamination of the marine environment surrounding coastal Antarctic research stations remains insufficiently understood in terms of its extent, persistence, and characteristics. We investigated the presence of contaminants in marine sediments near Casey Station, located in the Windmill Islands of East Antarctica, during the period spanning from 1997 to 2015. Metals, hydrocarbons, PBDEs, PCBs, and nutrients were measured in sediments at anthropogenically disturbed sites, including the wastewater outfall, the wharf area, two former waste disposal sites, and various control locations. Sampling was carried out at three spatial scales: Locations, which were generally kilometres apart and formed the primary scale for comparison; Sites, which were 100 meters apart within each location; and Plots, which were 10 meters apart within each site. Consistently higher concentrations of most contaminants, and in some cases nutrients, were observed at disturbed locations. Some locations also exhibited an increase in contaminant concentrations over time. The spatial distribution of sediment properties (such as grain size and organic matter) and contaminants displayed intricate patterns of variation. Variation in grain size depended on the size category, with fine grains (e.g., <63 μm) showing the greatest variation at the Location scale, while coarse grains exhibited minimal variation at this scale. Contaminant levels demonstrated significant differences between Locations, accounting for approximately 55% of the overall variation for metals, while the variation within the 10-meter scale generally exceeded that within the 100-meter scale. Residual variation among replicate samples was also very high, demonstrating the need for adequate replication in studies of sediments and contaminants around stations. Some contaminants exceeded international guidelines for sediment quality, including metals, hydrocarbons, and PCBs. We conclude that Antarctic research stations such as Casey are likely to pose a moderate level of long-term ecological risk to local marine ecosystems through marine pollution. However, contamination is expected to be confined to areas in close proximity to the stations, although its extent and concentration are anticipated to increase with time. Raising awareness of the contamination risks associated with Antarctic stations and implementing monitoring programs for marine environments adjacent to these stations can contribute to informed decision-making and the improvement of environmental management practices in Antarctica.

Bioaccumulation, Bioindication and Health Risk Assessment of Heavy Metals in Cape Horse Mackerel (Trachurus trachurus) and Slinger Seabream (Chrysoblephus puniceus) in the Durban Basin and Cape Vidal, South Africa

The bioaccumulation of heavy metals (HMs) in marine fish is a growing global concern due to potential human health risks. The study analyzed HM in the muscle tissue, gills, and gut of adult male and female cape horse mackerel and slinger seabream caught in the polluted Durban Basin and pristine Cape Vidal from April 2018 to February 2019. Results revealed interspecific, spatial, and organ-specific variability in HM levels. In the Durban Basin, slinger seabream had bioaccumulation (in mg/kg) of As (2.3 ± 0.2), Cr (2.6 ± 0.2), Ni (2.0 ± 0.1), and Pb (4.1 ± 0.3) while cape horse mackerel had Ni (1.6 ± 0.2), Pb (4.7 ± 0.6), and Zn (52 ± 3.01) exceeding World Health Organization (WHO) regulatory limits. Metal pollution index (MPI) values were also higher in Durban Basin (> 5.13) than Cape Vidal (< 3.32) for both species' muscles. Liver and gills of slinger seabream and gut of cape horse mackerel exhibited higher HM accumulation patterns proportionate to the environmental concentrations, indicating the bioindicative potential of HM pollution by the two species. Risk assessment indicated that both fish species had target hazard quotient > 1 for Cr, and target cancer risk < 10-4 for Pb, implying significant potential non-carcinogenic and carcinogenic health risks associated with fish consumption from the Durban Basin. The study recommends daily consumption limits of 16 g/day for slinger seabream and 14 g/day for cape horse mackerel to ensure health safety. The findings contribute to the understanding of HM pollution in the Durban Basin and provide important information for decision-makers and policymakers in developing effective strategies to mitigate and manage HM contamination in fish populations.

Effects of lubricant oil and diesel on macrofaunal communities in marine sediments: A five year field experiment in Antarctica

Hydrocarbons pose significant risks to marine ecosystems. A field experiment investigated the effects of four different hydrocarbon products (diesel fuel and three lubricating oils: Unused, Used and Biodegradable) on sediment macrofaunal communities over a five year period, in a shallow Antarctic marine embayment. Sediments were defaunated, treated with a hydrocarbon and deployed in trays (including a control) on the seabed. Diesel fuel had the biggest initial impact on communities, with strong effects at 5 weeks and 1 year, in particular on annelids, but also on amphipods, ostracods and cumaceans. By five years, however, the effect of diesel was less than that of lubrication oils and showed more recovery than oiled treatments and the biggest effect was from the Used oil. There was an effect of hydrocarbons on diversity, especially diesel, at 5 weeks and 1 year, but by 2 and 5 years diversity was not different or greater in hydrocarbon treatments than controls. Total abundance was always lower in hydrocarbon treatments than controls, especially for crustaceans, but annelids were more abundant in oil treatments than controls at 5 years. Oils, and in some cases diesel, enhanced the abundance of some taxa at 2-5 years, including molluscs, some polychaete families (capitellids, cirratulids, dorvilleids), oligochaetes, as well as ostracods, cumaceans and isopods. Amphipods and tanaids were most sensitive to hydrocarbons, and annelids were very sensitive to diesel. The Biodegradable oil had similar magnitude community effects to standard oil at 5 years, but annelids were more affected by Biodegradable oil, particularly at 1 and 2 years, and it did not enhance annelid or mollusc abundance at 5 years like the other oils, except for some polychaete families. Impacts of spilled hydrocarbons in Antarctica will persist well beyond 5 years, but diesel impacts will recover faster than oil.

Environmental DNA metabarcoding for monitoring metazoan biodiversity in Antarctic nearshore ecosystems

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

Long-term changes in contamination and macrobenthic communities adjacent to McMurdo Station, Antarctica

Improved waste management at McMurdo Station, Antarctica beginning in the 1980s has been followed by decreases in polycyclic aromatic hydrocarbon (PAH) and metal contamination in the adjacent marine sediments. However, determining the effect of the decreased contamination on marine ecological indicators (macrobenthic fauna) is confounded by concurrent changes in climate cycles and other physical forces. Between 2000 and 2013, there was a decrease in concentrations of some contaminants including mercury, copper, organochlorines, and PAHs in marine sediments adjacent to McMurdo Station. PAH concentrations in Winter Quarters Bay decreased an order of magnitude from 2000/2003 to 2012/2013 and were within an order of magnitude of reference area concentrations by 2013. Macrobenthic communities did not indicate any sign of recovery and have not become more similar to reference communities over this same period of time. Temporal changes in macrobenthic community composition during the study period had higher correlations with climatic and sea ice dynamics than with changes in contaminant concentrations. The Interdecadal Pacific Oscillation climatic index had the highest correlation with macrobenthic community composition. The Antarctic Oscillation climatic index, maximum ice extent and other natural environmental factors also appear to influence macrobenthic community composition. Despite large improvements in environmental management at McMurdo Station, continuing environmental vigilance is necessary before any noticeable improvement in ecological systems is likely to occur. The effects of climate must be considered when determining temporal changes in anthropogenic effects in Antarctica. Maintaining long-term monitoring of both contaminants and ecological indicators is important for determining the localized and global influences of humans on Antarctica, which will have implications for the whole planet.

Natural Products Repertoire of the Red Sea

Marine natural products have achieved great success as an important source of new lead compounds for drug discovery. The Red Sea provides enormous diversity on the biological scale in all domains of life including micro- and macro-organisms. In this review, which covers the literature to the end of 2019, we summarize the diversity of bioactive secondary metabolites derived from Red Sea micro- and macro-organisms, and discuss their biological potential whenever applicable. Moreover, the diversity of the Red Sea organisms is highlighted as well as their genomic potential. This review is a comprehensive study that compares the natural products recovered from the Red Sea in terms of ecological role and pharmacological activities.

Assessing the Risk of Metals and Their Mixtures in the Antarctic Nearshore Marine Environment with Diffusive Gradients in Thin-Films

Robust environmental assessments and contaminant monitoring in Antarctic near-shore marine environments need new techniques to overcome challenges presented by a highly dynamic environment. This study outlines an approach for contaminant monitoring and risk assessment in Antarctic marine conditions using diffusive gradients in thin-films (DGT) coupled to regionally specific ecotoxicology data and environmental quality standards. This is demonstrated in a field study where DGT samplers were deployed in the near-shore marine environment of East Antarctica around the operational Casey station and the abandoned Wilkes station to measure the time-averaged biologically available fraction of metal contaminants. The incorporation of DGT-labile concentrations to reference toxicity mixture models for three Antarctic organisms predicted low toxic effects (<5% effect to the growth or development of each organism). The comparison of metal concentrations to the Australian and New Zealand default water quality guideline values (WQGVs) showed no marine site exceeding the WQGVs for 95% species protection. However, all sites exceeded the 99% WQGVs due to copper concentrations that are likely of geogenic origin (i.e., not from anthropogenic sources). This study provides evidence supporting the use of the DGT technique to monitor contaminants and assess their environmental risk in the near-shore marine environment of Antarctica.

Sources of elevated heavy metal concentrations in sediments and benthic marine invertebrates of the western Antarctic Peninsula

Antarctica is one of the least anthropogenically-impacted areas of the world. Metal sources to the marine environment include localised activities of research stations and glacial meltwater containing metals of lithogenic origin. In this study, concentrations of nine metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn) were examined in three species of benthic invertebrates collected from four locations near Rothera Research Station on the western Antarctic Peninsula: Laternula elliptica (mudclam, filter feeder), Nacella concinna (limpet, grazer) and Odontaster validus (seastar, predator and scavenger). In addition, metals were evaluated in sediments at the same locations. Metal concentrations in different body tissues of invertebrates were equivalent to values recorded in industrialized non-polar sites and were attributed to natural sources including sediment input resulting from glacial erosion of local granodioritic rocks. Anthropogenic activities at Rothera Research Station appeared to have some impact on metal concentrations in the sampled invertebrates, with concentrations of several metals higher in L. elliptica near the runway and aircraft activities, but this was not a trend that was detected in the other species. Sediment analysis from two sites near the station showed lower metal concentrations than the control site 5 km distant and was attributed to differences in bedrock metal content. Differences in metal concentrations between organisms were attributed to feeding mechanisms and habitat, as well as depuration routes. L. elliptica kidneys showed significantly higher concentrations of eight metals, with some an order of magnitude greater than other organs, and the internal structure of O. validus had significantly higher Ni. This study supports previous assessments of N. concinna and L. elliptica as good biomonitors of metal concentrations and suggests O. validus as an additional biomonitor for use in future Antarctic metal monitoring programs.

Toxic anthropogenic signature in Antarctic continental shelf and deep sea sediments

Industrial activity generates harmful substances which can travel via aerial or water currents thousands of kilometers away from the place they were used impacting the local biota where they deposit. The presence of harmful anthropogenic substances in the Antarctic is particularly surprising and striking due to its remoteness and the apparent geophysical isolation developed with the flows of the Antarctic Circumpolar current and the ring of westerly winds surrounding the continent. However, long-range atmospheric transport (LRAT) of pollutants has been detected in the Antarctic since the 70’s along the Antarctic trophic food web from phytoplankton to birds. Still, no information exists on the presence of cytotoxic compounds in marine sediments neither at basin scales (thousands of kilometers) nor in water depths (hundreds of meters) beyond shallow coastal areas near research stations. Our results showed for the first time that there is cytotoxic activity in marine sediment extracts from water depths >1000 m and along thousands of kilometers of Antarctic continental shelf, in some cases comparable to that observed in Mediterranean areas. Ongoing anthropogenic pressure appears as a serious threat to the sessile benthic communities, which have evolved in near isolation for millions of years in these environments.

Chronic toxicity of five metals to the polar marine microalga Cryothecomonas armigera - Application of a new bioassay

The paucity of ecotoxicological data for Antarctic organisms is impeding the development of region-specific water quality guidelines. To address this limitation, toxicity testing protocols need to be developed to account for the unique physiology of polar organisms, in particular their slow growth rates. In this study, a toxicity test protocol was developed to investigate the toxicities of five metals to the polar marine microalga Cryothecomonas armigera. The concentrations which reduced population growth rate by 10% (EC10) after 24-d for Cu, Pb, Zn, Cd and Ni were 21.6, 152, 366, 454, and 1220 μg.L^-1, respectively. At the concentrations used in tests, only Cu and Ni were sufficiently toxic to enable the derivation of EC50 values of 63.1 and 1570 μg.L^-1 respectively. All metals affected C. armigera's cellular physiology including cellular chlorophyll a fluorescence, cell complexity and size, and lipid concentrations. However, no changes to cellular membrane permeability were observed. The reduction in cellular lipid concentrations was a more sensitive indicator of toxicity for Cd, Ni, and Pb than growth rate inhibition, with EC10 values of 89, 894, and 11 μg.L^-1, respectively, highlighting its potential as a sensitive measure of metal toxicity.

The environmental impact of sewage and wastewater outfalls in Antarctica: An example from Davis station, East Antarctica

We present a comprehensive scientific assessment of the environmental impacts of an Antarctic wastewater ocean outfall, at Davis station in East Antarctica. We assessed the effectiveness of current wastewater treatment and disposal requirements under the Protocol on Environmental Protection to the Antarctic Treaty. Macerated wastewater has been discharged from an outfall at Davis since the failure of the secondary treatment plant in 2005. Water, sediment and wildlife were tested for presence of human enteric bacteria and antibiotic resistance mechanisms. Epibiotic and sediment macrofaunal communities were tested for differences between sites near the outfall and controls. Local fish were examined for evidence of histopathological abnormalities. Sediments, fish and gastropods were tested for uptake of sewage as measured by stable isotopes of N and C. Escherichia coli carrying antibiotic resistance determinants were found in water, sediments and wildlife (the filter feeding bivalve Laternula eliptica). Fish (Trematomus bernacchii) within close proximity to the outfall had significantly more severe and greater occurrences of histopathological abnormalities than at controls, consistent with exposure to sewage. There was significant enrichment of ¹⁵N in T. bernacchii and the predatory gastropod Neobuccinum eatoni around the outfall, providing evidence of uptake of sewage. There were significant differences between epibiotic and sediment macrofaunal communities at control and outfall sites (<1.5 km), when sites were separated into groups of similar habitat types. Benthic community composition was also strongly related to habitat and environmental drivers such as sea ice. The combined evidence indicated that the discharge of wastewater from the Davis outfall is causing environmental impacts. These findings suggest that conditions in Antarctic coastal locations, such as Davis, are unlikely to be conducive to initial dilution and rapid dispersal of wastewater as required under the Protocol on Environmental Protection to the Antarctic Treaty. Current minimum requirements for wastewater treatment and disposal in Antarctica are insufficient to ameliorate these risks and are likely to lead to accumulation of contaminants and introduction of non-native microbes and associated genetic elements. This new understanding suggests that modernised approaches to the treatment and disposal of wastewater are required in Antarctica. The most effective solution is advanced levels of wastewater treatment, which are now possible, feasible and a high priority for installation. As a direct outcome of the study, a new advanced treatment system is being installed at Davis, effectively avoiding environmental risks.

Dispersal and dilution of wastewater from an ocean outfall at Davis Station, Antarctica, and resulting environmental contamination

The Antarctic Treaty permits the discharge of wastewater into Antarctic marine waters providing that conditions exist for initial dilution and rapid dispersal. We investigated the dilution and dispersal of macerated wastewater around Australia's Davis Station in East Antarctica and examined sediments for evidence of contaminants. Methods used to examine hydrodynamic conditions included current meters, dye release experiments and measurement of sewage-associated microbial markers and surfactants in the water column. We measured marine sediments for metals, nutrients, PBDEs, hydrocarbons and faecal sterols. We propose that if there is adequate dilution and dispersal there would be no significant difference in contaminant concentrations in sediments around the outfall compared to distant control sites. Currents were strongly correlated with prevailing wind conditions. Modelling indicated that diffusivity of wastewater had the greatest effect on dilution factors and that neither discharge rates nor local currents had as much effect. During summer conditions of open water, wastewater is likely to be constrained in a narrow plume close to the coast. Concentrations of sewage bacteria were high around the outfall and detected up to 1.5 km away, along with dye. There were significant differences in sediment concentrations of metals, PBDEs, hydrocarbons, nutrients and faecal sterols between sites within 2 km of the outfall and control sites. We conclude that dilution and dispersal conditions at the Davis outfall are insufficient to prevent the accumulation of contaminants in local sediments and that microbial hazards posed by wastewater are an environmental risk to local wildlife.

Extracellular DNA amplicon sequencing reveals high levels of benthic eukaryotic diversity in the central Red Sea

The present study aims to characterize the benthic eukaryotic biodiversity patterns at a coarse taxonomic level in three areas of the central Red Sea (a lagoon, an offshore area in Thuwal and a shallow coastal area near Jeddah) based on extracellular DNA. High-throughput amplicon sequencing targeting the V9 region of the 18S rRNA gene was undertaken for 32 sediment samples. High levels of alpha-diversity were detected with 16,089 operational taxonomic units (OTUs) being identified. The majority of the OTUs were assigned to Metazoa (29.2%), Alveolata (22.4%) and Stramenopiles (17.8%). Stramenopiles (Diatomea) and Alveolata (Ciliophora) were frequent in a lagoon and in shallower coastal stations, whereas metazoans (Arthropoda: Maxillopoda) were dominant in deeper offshore stations. Only 24.6% of total OTUs were shared among all areas. Beta-diversity was generally lower between the lagoon and Jeddah (nearshore) than between either of those and the offshore area, suggesting a nearshore-offshore biodiversity gradient. The current approach allowed for a broad-range of benthic eukaryotic biodiversity to be analysed with significantly less labour than would be required by other traditional taxonomic approaches. Our findings suggest that next generation sequencing techniques have the potential to provide a fast and standardised screening of benthic biodiversity at large spatial and temporal scales.

Metabolic responses of the Antarctic fishes Notothenia rossii and Notothenia coriiceps to sewage pollution

The present study aimed to assess the sewage effects of the Brazilian Antarctic Station Comandante Ferraz, Admiralty Bay, King George Island, on the hepatic metabolism (energetic, antioxidant, and arginase levels) and levels of plasma constituents of two Antarctic fish species Notothenia rossii and N. coriiceps. The bioassays were conducted under controlled temperature (0 °C) and salinity (35 psu), exposing the fish for 96 h, to sewage effluent diluted in seawater to 0.5 % (v/v). Liver homogenates were tested for the specific activities of the enzymes glucose-6-phosphatase (G6Pase), glycogen phosphorylase (GPase), hexokinase, citrate synthase, lactate dehydrogenase, malate dehydrogenase, glucose-6-phosphate dehydrogenase, superoxide dismutase, glutathione reductase, catalase, and arginase. Plasma levels of glucose, triacylglycerides, cholesterol, total protein, albumin, chloride, magnesium, calcium, and inorganic phosphate were also determined. In N. rossii, the decrease in citrate synthase and the increase in G6Pase and GPase suggested that the sewage effluent activated glycogenolysis and hepatic gluconeogenesis, whereas is N. coriiceps, only G6Pase levels were increased. In N. rossii, sewage effluent induced hypertriglyceridemia without modulating glucose plasma levels, in contrast to N. coriiceps, which developed hypoglycemia without elevating plasma triglyceride levels. The decrease in glutathione reductase levels in N. coriiceps and in superoxide dismutase and catalase in N. rossii suggest that these two species are susceptible to oxidative stress stemming from the production of reactive oxygen species. An increase in magnesium in N. rossii and a decrease in N. coriiceps showed that sewage effluent compromised the control of plasma levels of this cation. Although phylogenetically close, both species of Antarctic fish exhibited different metabolic responses to the sewage effluent, with N. coriiceps showing greater susceptibility to the toxic effects of the pollutants. The present study suggests that the biochemical responses of these two species are potential indicators of metabolic changes caused by sewage effluents.