Arctic Benthic Communities Research Articles

Bioaccumulation of pharmaceuticals and stimulants in macrobenthic food web in the European Arctic as determined using stable isotope approach

Although pharmaceuticals are increasingly detected in abiotic matrices in the Arctic, the accumulation of drugs in the resident biota and trophic transfer have not been yet examined. This study investigated the behaviour of several pharmaceuticals in the rocky-bottom, macrobenthic food web in the coastal zone of Isfjorden (western Spitsbergen) using stable isotope analyses (SIA) coupled with liquid chromatography-mass spectrometry (LC-MS/MS). Across 16 macroalgal and invertebrate species the highest average concentration was measured for ciprofloxacin (CIP) (on average 60.3 ng g−1 dw) followed by paracetamol (PCT) (51.3 ng g−1 dw) and nicotine (NIC) (37.8 ng g−1 dw). The biomagnification potential was assessed for six target compounds of 13 analytes detected that were quantified with a frequency > 50 % in biological samples. The trophic magnification factor (TMF) ranged between 0.3 and 2.8, and was significant for NIC and CIP. TMF < 1.0 for NIC (0.3; confidence interval, CI 0.1–0.5) indicated that the compound does not accumulate with trophic position. The dilution of pharmaceutical residues in the food web may result from limited intake with dietary route, poor assimilation efficiency and high biotransformation rates in benthic invertebrates. TMF for CIP (2.8, CI 1.2–6.4) suggests trophic magnification, a phenomenon observed previously for several antibiotics in freshwater food webs. Trophic transfer therefore plays a role in controlling concentration of CIP in the Arctic benthic communities and should be considered in environmental risk assessment. Biomagnification potential of diclofenac (DIC; 0.9, CI 0.5–1.7), carbamazepine (CBZ; 0.4, CI 0.1–2.1), caffeine (CAF; 0.9, CI 0.5–1.9) and PCT (1.3, CI 0.7–2.7) was not evident due to large 95 % confidence of their TMFs. This study provides the first evidence of drug bioaccumulation in the Arctic food web and indicates that behaviour of pharmaceuticals varies among target compounds.

Limited predatory effects on infaunal macrobenthos community patterns in intertidal soft-bottom of Arctic coasts.

Predation shapes marine benthic communities and affects prey species population dynamics in tropic and temperate coastal systems. However, information on its magnitude in systematically understudied Arctic coastal habitats is scarce. To test predation effects on the diversity and structure of Arctic benthic communities, we conducted caging experiments in which consumers were excluded from plots at two intertidal sedimentary sites in Svalbard (Longyearbyen and Thiisbukta) for 2.5months. Unmanipulated areas served as controls and partial (open) cages were used to estimate potential cage effects. At the end of the experiment, we took one sediment core from each plot and quantified total biomass and the number of each encountered taxon. At both sites, the experimental exclusion of predators slightly changed the species composition of communities and had negligible effects on biomass, total abundance, species richness, evenness, and Shannon Index. In addition, we found evidence for cage effects, and spatial variability in the intensity of the predation effects was identified. Our study suggests that predators have limited effects on the structure of the studied intertidal macrobenthic Arctic communities, which is different from coastal soft-bottom ecosystems at lower latitudes.

Chemosynthetic and photosynthetic trophic support from cold seeps in Arctic benthic communities

Benthic communities below the photic zone are largely reliant on the export of surface-water primary production and the flux of partially degraded organic matter to the seabed, i.e. pelagic−benthic coupling. Over the past decades, however, the role of chemosynthetically produced carbon in food webs has been recognized in various habitats. Cold seeps are now known to be widespread across circumpolar Arctic shelves where natural release of hydrocarbons occurs at the seabed. Here, we investigated to what extent chemosynthesis-based carbon (CBC) enters the food web in a high latitude shelf-system. Specifically, we estimated the contributions of chemosynthesis-based carbon to primarily benthic invertebrate taxa from seeps at both shallow and deeper shelves and comparative non-seep areas in the Svalbard-Barents Sea region using bulk stable isotope-analysis of carbon and nitrogen. Our results show low δ13C values (-51.3 to -32.7 ‰) in chemosymbiotic siboglinids and several species of benthic, higher-trophic level, invertebrates (mainly polychaetes and echinoderms; -35.0 to -26.1‰) collected at cold seeps, consistent with assimilation of chemosynthesis-based carbon into the Arctic benthic food web. Using a two-component mixing equation, we demonstrate that certain species could derive more than 50% of their carbon from chemosynthesis-based carbon. These findings show that autochthonous chemosynthetic energy sources can contribute to supporting distinct groups of ‘background’ benthic taxa at these Arctic seep-habitats beyond microbial associations and chemosymbiotic species. Furthermore, we found a higher degree of chemosynthesis-based carbon in benthos at the deeper Barents Sea shelf seeps (&amp;gt;330 m) compared to seeps at the Western Svalbard shelf (&amp;lt;150 m water-depth), and we suggest this result reflects the differences in depth range, surface production and pelagic-benthic coupling. We detected large intra-species variations in carbon signatures within and across geographical locations and, combined with isotopic niche-analysis, our results show that certain taxa that inhabits seeps, have wider trophic niches in comparison to taxa inhabiting non-seeps. The increasing number of discovered natural seeps in the Arctic suggests that chemosynthetic production from seeps could play a more critical role in Arctic trophic structure than previously thought. Seep-derived carbon should, hence, be accounted for as an additional carbon source and included in food-web and energy-flow models in future work.

Changes to benthic community structure may impact organic matter consumption on Pacific Arctic shelves.

Changes in species composition and biomass of Arctic benthic communities are predicted to occur in response to environmental changes associated with oceanic warming and sea-ice loss. Such changes will likely impact ecosystem function, including flows of energy and organic material through the Arctic marine food web. Oxygen consumption rates can be used to quantify differences in metabolic demand among species and estimate the effects of shifting community structure on benthic carbon consumption. Closed-system respirometry using non-invasive oxygen optodes was conducted onboard the R/V Sikuliaq in June 2017 and 2018 on six dominant species of benthic macrofauna from the northern Bering and southern Chukchi Sea shelves, including five bivalve species (Macoma sp., Serripes groenlandicus, Astarte sp., Hiatella arctica and Nuculana pernula) and one amphipod species (Ampelisca macrocephala). Results revealed species-specific respiration rates with high metabolic demand for S. groenlandicus and A. macrocephala compared to that of the other species. For a hypothetical 0.1-g ash-free dry mass individual, the standard metabolic rate of S. groenlandicus would be 4.3 times higher than that of Astarte sp. Overall, carbon demand ranged from 8 to 475 μg C individual−1 day−1 for the species and sizes of individuals measured. The allometric scaling of respiration rate with biomass also varied among species. The scaling coefficient was similar for H. arctica, A. macrocephala and Astarte sp., while it was high for S. groenlandicus and low for Macoma sp. These results suggest that observed shifts in spatial distribution of the dominant macrofaunal taxa across this region will impact carbon demand of the benthic community. Hence, ecosystem models seeking to incorporate benthic system functionality may need to differentiate between communities that exhibit different oxygen demands.

Cold Seeps in a Warming Arctic: Insights for Benthic Ecology

Cold-seep benthic communities in the Arctic exist at the nexus of two extreme environments; one reflecting the harsh physical extremes of the Arctic environment, and another reflecting chemical extremes and strong environmental gradients associated with seafloor seepage of methane and toxic sulfide enriched sediments. Recent ecological investigations of cold seeps at numerous locations on the margins of the Arctic Ocean basin reveal that seabed seepage of reduced gas and fluids strongly influence benthic communities and associated marine ecosystems. These Arctic seep communities are mostly different from both conventional Arctic benthic communities as well as cold-seep systems elsewhere in the world. They are characterized by a lack of large specialized chemo-obligate polychaetes and molluscs often seen at non-Arctic seeps, but nonetheless have substantially higher benthic abundance and biomass compared to adjacent Arctic areas lacking seeps. Arctic seep communities are dominated by expansive tufts or meadows of siboglinid polychaetes, which can reach densities up to >3x10^5 ind.m-2. The enhanced authochthonous chemosynthetic production, combined with reef-like structures from methane-derived authigenic carbonates, provides a rich and complex local habitat that results in aggregations of non-seep specialized fauna from multiple trophic levels, including several commercial species. Seeps are far more widespread in the Arctic than thought even a few years ago. They exhibit in situ benthic chemosynthetic production cycles that operate on different spatial and temporal cycles than the sunlight driven counterpart of photosynthetic production in the ocean’s surface. These systems can act as a spatio-temporal bridge for benthic communities and associated ecosystems that may otherwise suffer from a lack of consistency in food quality from the surface ocean during seasons of low production. As climate change impacts accelerate in Arctic marginal seas, photosynthetic primary production cycles are being modified, including in terms of changes in the timing, magnitude, and quality of photosynthetic carbon, whose delivery to the seabed fuels benthic communities. Furthermore, an increased northward expansion of species is expected as a consequence of warming seas. This may have implications for dispersal and evolution of both chemosymbiotic species as well as for background taxa in the entire realm of the Arctic and fringing seas.

Short-term processing of ice algal- and phytoplankton-derived carbon by Arctic benthic communities revealed through isotope labelling experiments

Short-term processing of ice algal- and phytoplankton-derived carbon by Arctic benthic communities revealed through isotope labelling experiments

Food and disturbance effects on Arctic benthic biomass and production size spectra

Body size is a fundamental biological unit that is closely coupled to key ecological properties and processes. At the community level, changes in size distributions may influence energy transfer pathways in benthic food webs and ecosystem carbon cycling; nevertheless they remain poorly explored in benthic systems, particularly in the polar regions. Here, we present the first assessment of the patterns of benthic biomass size spectra in Arctic coastal sediments and explore the effects of glacial disturbance and food availability on the partitioning of biomass and secondary productivity among size-defined components of benthic communities.The samples were collected in two Arctic fjords off west Spitsbergen (76 and 79°N), at 6 stations that represent three regimes of varying food availability (indicated by chlorophyll a concentration in the sediments) and glacial sedimentation disturbance intensity (indicated by sediment accumulation rates). The organisms were measured using image analysis to assess the biovolume, biomass and the annual production of each individual. The shape of benthic biomass size spectra at most stations was bimodal, with the location of a trough and peaks similar to those previously reported in lower latitudes. In undisturbed sediments macrofauna comprised 89% of the total benthic biomass and 56% of the total production. The lower availability of food resources seemed to suppress the biomass and secondary production across the whole size spectra (a 6-fold decrease in biomass and a 4-fold decrease in production in total) rather than reshape the spectrum. At locations where poor nutritional conditions were coupled with disturbance, the biomass was strongly reduced in selected macrofaunal size classes (class 10 and 11), while meiofaunal biomass and production were much higher, most likely due to a release from macrofaunal predation and competition pressure. As a result, the partitioning of benthic biomass and production shifted towards meiofauna (39% of biomass and 83% of production), which took over the benthic metazoan key-player role in terms of processing organic matter in sediments. Macrofaunal nematodes composed a considerable portion of the benthic community in terms of biomass (up to 9%) and production (up to 12%), but only in undisturbed sediments with high organic matter content. Our study indicates that food availability and disturbance controls the total bulk and partitioning of biomass and production among the size classes in Arctic benthic communities.

Patterns and trends of macrobenthic abundance, biomass and production in the deep Arctic Ocean

Little is known about the distribution and dynamics of macrobenthic communities of the deep Arctic Ocean. The few previous studies report low standing stocks and confirm a gradient with declining biomass from the slopes down to the basins, as commonly reported for deep-sea benthos. In this study, we investigated regional differences of faunal abundance and biomass, and made for the first time ever estimates of deep Arctic community production by using a multi-parameter artificial neural network model. The underlying data set combines data from recent field studies with published and unpublished data from the past 20 years, to analyse the influence of water depth, geographical latitude and sea-ice concentration on Arctic benthic communities. We were able to confirm the previously described negative relationship of macrofauna standing stock with water depth in the Arctic deep sea, while also detecting substantial regional differences. Furthermore, abundance, biomass and production decreased significantly with increasing sea-ice extent (towards higher latitudes) down to values <200 ind m−2, <65 mg C m−2 and <73 mg C m−2 y−1, respectively. In contrast, stations under the seasonal ice zone regime showed much higher standing stock and production (up to 2500 mg C m−2 y−1), even at depths down to 3700 m. We conclude that particle flux is the key factor structuring benthic communities in the deep Arctic Ocean as it explains both the low values in the ice-covered Arctic basins and the higher values in the seasonal ice zone.

International governance of the arctic marine environment

The Arctic is a region in the northernmost hemisphere of the Earth. It is known for its extreme environmental conditions, in particular its cold temperatures, high winds, snow, and ice. Yet, life in this polar region is plentiful and includes both terrestrial and marine organisms. The Arctic Ocean provides for a unique, cold-temperatureadapted ecosystem containing plankton, marine mammals, and fish. Studies have shown that polar ice coverage has declined, which is believed to be caused by climate change (i.e., a persistent long-term warming trend). This widespread change impacts arctic biota by altering the distribution of species and the composition of food webs. Shifts in species distribution patterns of arctic benthic communities and marine fishes of the arctic have recently been described in detail by Ilken et al. (2013) and by Mueter et al. (2013), respectively. The book by Weidemann (2014) is about the implications of climate change for the arctic marine environment and the deficits of legal regimes that govern this part of the world. The example of high seas fisheries is used to demonstrate the shortcomings in the Arctic’s international governance. Besides a brief introduction, Weidemann (2014) divided the book into three major sections: 1. Environmental Situation in the Arctic; 2. International Governance of the Arctic Marine Environment; and 3. Possible Ways for Enhancement. I will use in this review the same section headings to highlight some of the author’s main arguments. The book is part of the series Hamburg Studies on Maritime Affairs (Volume 27).

Degradation and recovery of an Arctic benthic community under organic enrichment

Fast development of mariculture in the world leads to increasing of the load on natural habitats, especially due to organic enrichment. There are a few investigations concerning the effect of additional organic loading on the Arctic benthic communities. The main goal of our research was to ascertain the impact of mussel farm on the benthic community in the White Sea and its following recovery after mussel farm removal. We performed annual observations from 1988 to 2011. During the mussel farm functioning, two stages of organic enrichment impact on community structure were recorded: in the first 2 years, diversity and proportion of deposit feeders increased but later all studied characteristics of the benthic community decreased significantly. After the mussel farm removal, the benthic community started to restore and we distinguished several stages of recovery succession. Native structure of benthic community began to recover 8 years after organic loading had ceased, when selective deposit feeding bivalves Portlandia arctica Gray appeared in the benthos. 4–6 years later it became the only dominating species in the studied benthic community. Therefore, in the White Sea, native structure recovery of the Arctic benthic community after the severe disturbance took about 15 years.

Rapid consumption of phytoplankton and ice algae by Arctic soft-sediment benthic communities: Evidence using natural and &lt;SUP&gt;13&lt;/SUP&gt;C-labeled food materials

Reduction of sea ice in the Arctic may significantly alter the relative fluxes of phytoplankton and ice algae to the seafloor. To examine the response of Arctic benthic communities to changing food supplies, we incubated sediment cores collected from two sites (Smeerenburg Fjord, northwest Svalbard in May 2003 and Storfjord Trench, Barents Sea in May 2004) with controlled additions of natural phytoplankton and ice algal assemblages, and laboratory-cultured C-labeled ice algae (Nitzschia frigida, in 2004 only). We measured sediment respiration, pigments, lipid biomarkers, and compound-specific C signals over the course of incubations. Both communities responded rapidly to the addition of food materials: regardless of food type, concentrations of organic biomarkers (pigments and fatty acids) decreased to the levels of control cores within seven days. Although we found no evidence for selective ingestion of the different food types by macrofauna, fatty acids were differentially consumed. The enriched polyunsaturated fatty acids of the ice algae were preferentially utilized compared to saturated and monounsaturated fatty acids bound in ice algae. However, the saturated and monounsaturated fatty acids of phytoplankton (with depleted polyunsaturated fatty acids) are utilized more efficiently than those counterparts bound in ice algae. Bacterial activity was stimulated by food addition, indicated by the immediate increase of bacteria-specific fatty acids, but the direct assimilation of C-labeled carbon into bacterial biomass was limited. Our results imply that Arctic benthic communities can meet their energetic requirements by altering strategies to assimilate different components from variable food supplies.

Benthic community response to petroleum-associated components in Arctic versus temperate marine sediments

We assessed the effects of crude oil and drill cuttings on sediment oxygen demand (SOD) of marine benthic communities from Arctic (Barents Sea) and temperate (Oslofjord) areas of the Norwegian continental shelf. Field-collected cores in both areas were subjected to three different treatments: two concentrations of hydrocarbon-contaminated sediments, and drill cuttings (DC). Cores were incubated for 21 days at 5°C (Barents Sea) and at 10°C (Oslofjord) during which SOD was measured five times. We observed significantly higher SOD in the high oil concentration (HOC) and DC treatments compared to control cores from the Arctic, but not in the temperate Oslofjord. No difference was observed between the low oil concentration (LOC) and control at either location. The clear differences in the response of Arctic benthic communities to petroleum compounds compared to temperate benthic communities is likely related to differences in community structure, sensitivity of individual taxa to petroleum-related compounds and different contamination history of the two study areas.

Species size distributions in Arctic benthic communities

In most subtidal soft-sediment faunal assemblages there is a trough in the species size distribution separating the macrofauna and meiofauna. To examine the hypothesis that this may be maintained by the avoidance of competition between macrofaunal adults and settling larvae, samples were taken from around Svalbard, an area where most macrofaunal species have either lecithotrophic or direct development. At three contrasting sites, bimodality of the species size spectrum was conserved. However, it is proposed that the adult-larval interaction hypothesis should not be rejected as low endemism in the fauna of the study area suggests its species size spectrum probably reflects evolutionary processes outside rather than within the Arctic.

Temperature effects on uptake and retention of contaminant radionuclides and trace metals by the brittle star Ophiothrix fragilis

Recent revelations of extensive dumping of radioactive wastes in Arctic seas emphasize the need to understand the processes affecting accumulation of contaminants in polar marine food webs. Little is known, however, about the effects of low temperatures on bioaccumulation of radionuclides and toxic metals. To address this question, we examined the effects of temperature on uptake and retention of 11 dissolved radioisotopes (including both nuclear waste components and required, and toxic metals) by the brittle star Ophiothrix fragilis, typical of species which dominate Arctic benthic communities. Lower temperatures significantly reduced uptake rates of all elements examined, but had little effect on loss rates. These results raise questions about the validity of extrapolating previous work on biological dynamics of dissolved contaminants, largely carried out at temperate zone temperatures, to polar ecosystems. This work suggests that the effects of low Arctic temperatures may need to be taken into consideration in order to understand the potential for food chain accumulation of nuclear wastes and toxic metals in high-latitude seas.