Trait-based modelling of bioaccumulation by freshwater benthic invertebrates

Quantitative differentiation of toxicity contributions and predicted global risk of fipronil and its transformation products to aquatic invertebrates

Biotransformation often alters chemical toxicity, yet its impacts on risk assessment are hardly quantified due to the challenges in acquiring internal exposure-based thresholds for chemicals that are readily metabolizable. Here, we integrated toxic unit and toxicokinetics to quantitatively assess toxicity contributions and potential risk of both parent compound and transformation products (TPs) to aquatic organisms, using fipronil (FIP) as a representative toxicant. In aquatic invertebrates Chironomus dilutus and Hyalella azteca, approximately 90 % of FIP was transformed to fipronil sulfone (SUL). FIP and SUL exhibited similar intrinsic toxicity to these organisms, which was contrary to conventional perception that SUL was more toxic than FIP. However, biotransformation was still important in risk assessment because the TP had 10-fold slower depuration rate than FIP. The amphipod H. azteca was found to be as sensitive to FIPs as the insect C. dilutus, which was previously considered ten times more sensitive based on external thresholds. This discrepancy has led to overlooking the toxicity of FIP to H. azteca in regional risk assessments. Lastly, we predicted the lethal risk of FIPs in global surface water. When using external thresholds for prediction, FIPs in 3.4 % of the water samples were lethally toxic to H. azteca, and the percentage of water samples at risk increased to 14 % when internal thresholds were used and SUF dominated the risk. This study presents an improved method for quantifying aquatic risk of readily metabolized toxicants. Our findings underscore the urgency of considering TPs in water quality assessments, especially for sensitive species that are at risk in the environment.

Abundance and risk assessment of microplastics in water, sediment, and aquatic insects of the Nile River

Microplastics (MPs) are a serious threat in freshwater environments. The ecological risk and abundance level of MPs in abiotic and biotic compartments of the Nile River haven't been systematically reported. Thus, these issues were highlighted in the present study during different seasons of the sampling year. The results showed that MP concentrations in the river ranged from 2.24 ± 0.6 to 3.76 ± 1.1 particles/L, 298 ± 63 to 520 ± 80 particles/kg dry weight, and 0.081 ± 0.051 to 4.95 ± 2.6 particles/individual in surface water, sediment, and different species of aquatic insects, respectively. All the extracted MPs are colored blue, red, and black. Fiber-shaped polyesters (<500-1500 μm) were the most common MPs in all the river compartments. MPs' dominance was observed during the summer in comparison with that in the other seasons. Environmental risk indicators indicate the high ecological risk of MPs, which are widely distributed in the Nile River. In conclusion, MP consumption by aquatic insects may not only be related to levels of environmental contamination, since other variables, such as taxon size, weight, and particular feeding behavior, may also be significant. Additionally, the presence of MPs in insects (at lower trophic levels) creates the potential for predation-based inter-trophic level transmission. Thus, higher trophic-level investigations of various feeding groups should be carried out to identify any possible harm that MPs cause to various aquatic organisms.

Assessment of exposure of benthic organisms to selected organochlorine pollutants in the west Spitsbergen fjords

Climate-related changes in environmental conditions, such as reduction of sea ice, intensive glacier retreat, and increasing summer precipitation, directly influence the arctic marine environment and, therefore, the organisms living there. Benthic organisms, being an important food source for organisms from higher trophic levels, constitute an important part of the Arctic trophic network. Moreover, the long lifespan and limited mobility of some benthic species make them suitable for the study of the spatial and temporal variability of contaminants. In this study, organochlorine pollutants (polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB)) were measured in benthic organisms collected in three fjords of western Spitsbergen. Two of these were recommended by the Marine Biodiversity and Ecosystem Functioning (MARBEF) Network of Excellence as European flagship sites, namely Hornsund as the Biodiversity Inventory and Kongsfjorden as the Long-Term Biodiversity Observatory. Adventfjorden, with notable human activity, was also studied. Ʃ7 PCB and HCB concentrations in sediments were up to 2.4 and 0.18 ng/g d.w. respectively. Concentrations of Ʃ7 PCBs and HCB measured in collected benthic organisms were up to 9.1 and 13 ng/g w.w., respectively. In several samples (41 of 169) the concentrations of ∑7 PCBs were below the detection limit values, yet nevertheless the results of the research show effective accumulation of target organochlorine contaminants by many Arctic benthic organisms. Important interspecies differences were observed. Free-living, mobile taxa, such as shrimp Eualus gaimardii, have accumulated a large quantity of contaminants, most probably due to their predatory lifestyle. ∑7 PCB and HCB concentrations were both significantly higher in Hornsund than in Kongsfjorden. Biomagnification occurred in 0 to 100 % of the predator-prey pairs, depending on the congener analyzed. Although the sampled organisms were proved to have accumulated organochlorine contaminants, the measured levels can be considered low, and not posing a substantial threat to the biota.

Target Lipid Model and Empirical Organic Carbon Partition Coefficients Predict Sediment Toxicity of Polychlorinated Biphenyls to Benthic Invertebrates

Quantifying causal exposure-response relationships for polychlorinated biphenyl (PCB) toxicity to benthic invertebrates can be an important component of contaminated sediment assessments, informing cleanup decisions and natural resource injury determinations. Building on prior analyses, we demonstrate that the target lipid model accurately predicts aquatic toxicity of PCBs to invertebrates, providing a means to account for effects of PCB mixture composition on the toxicity of bioavailable PCBs. We also incorporate updated data on PCB partitioning between particles and interstitial water in field-collected sediments, to better account for effects of PCB mixture composition on PCB bioavailability. To validate the resulting model, we compare its predictions with sediment toxicity data from spiked sediment toxicity tests and a variety of recent case studies from sites where PCBs are the primary sediment contaminant. The updated model should provide a useful tool for both screening-level and in-depth risk analyses for PCBs in sediment, and it should aid in diagnosing potential contributing factors at sites where sediment toxicity and benthic community impairment are observed. Environ Toxicol Chem 2023;42:1134-1151. © 2023 SETAC.

Ingestion of microplastics and textile cellulose particles by some meiofaunal taxa of an urban stream

Microplastics (MPs) and textile cellulose are globally pervasive pollutants in freshwater. In-situ studies assessing the ingestion of MPs by freshwater meiofauna are few. Here, we evaluated MP and textile cellulose ingestion by some meiofaunal taxa and functional guilds of a first-order stream in the city of Florence (Italy) by using a tandem microscopy approach (fluorescence microscopy and μFTIR). The study targeted five taxa (nematodes, oligochaetes, copepods, ephemeropterans and chironomids), three feeding (scrapers, deposit-feeders, and predators), and three locomotion (crawlers, burrowers, and swimmers) guilds. Fluorescent particles related to both MPs and textile cellulose resulted in high numbers in all taxa and functional guilds. We found the highest number of particles in nematodes (5200 particles/ind.) and deposit-feeders (1693 particles/ind.). Oligochaetes and chironomids (burrowers) ingested the largest particles (medium length: 28 and 48 μm, respectively), whereas deposit-feeders ingested larger particles (medium length: 26 μm) than scrapers and predators. Pellets were abundant in all taxa, except for Chironomidae. Textile cellulose fibers were present in all taxa and functional guilds, while MP polymers (EVA, PET, PA, PE, PE-PP) differed among taxa and functional guilds. In detail: EVA and PET particles were found only in chironomids, PE particles occurred in chironomids, copepods and ephemeropterans, PA particles were found in all taxa except in nematodes, whereas particles made of PE-PP blend occurred in oligochaetes and copepods. Burrowers and deposit-feeders ingested EVA, PET, PA, PE and PE-PP, while crawlers and scrapers ingested PE and PA. Swimmers and predators ingested PE, PA and PE-PP. Our findings suggest a pervasive level of plastic and textile cellulose pollution consistent with an urban stream which propagates in the meiofaunal assemblage of the stream ecosystem.

Bioaccumulation and bioamplification of pharmaceuticals and endocrine disruptors in aquatic insects

Environmental fate of emerging contaminants such as pharmaceuticals and endocrine disrupting compounds at the aquatic terrestrial boundary are largely unexplored. Aquatic insects connect aquatic and terrestrial food webs as their life cycle includes aquatic and terrestrial life stages, thus they represent an important inter-habitat linkage not only for energy and nutrient flow, but also for contaminant transfer to terrestrial environments. We measured the concentrations of pharmaceuticals and endocrine disrupting compounds in the larval and adult tissues (last larval stages and teneral adults) of five Odonata species sampled in a wastewater-impacted river, in order to examine their bioaccumulation and bioamplification at different taxonomic levels. Twenty different compounds were bioaccumulated in insect tissues, with majority having higher concentrations (up to 90% higher) in aquatic larvae compared to terrestrial adults (reaching 88 ng/g for 1H-benzotriazole). However, increased concentration in adults was observed for seven compounds in at least one suborder (41% of the accumulated), confirming contaminants bioamplification across the metamorphosis. Both, bioaccumulation and bioamplification differed at various taxa levels; the order (Odonata), suborder (Anisoptera and Zygoptera) and species level. Highest variability was observed between Anisoptera and Zygoptera, due to the underlying differences in their ecology. Generally, Zygoptera had higher concentrations of contaminants in both larvae and adults. Additionally, we aimed at predicting effects of contaminant properties on bioaccumulation and bioamplification patterns using the commonly used physicochemical and pharmacokinetic descriptors on both order and suborder levels, however, neither of the two processes could be consistently predicted with simple linear models. Our study highlights the importance of taxonomy in studies aiming at advancing the understanding of contaminant exchange between aquatic and terrestrial food webs, as higher taxonomic categories include ecologically diverse groups, whose contribution to "the dark side of subsidies" could substantially differ.

Organochlorine pesticides and chlorpyrifos in the sea anemone Bunodosoma zamponii (Actiniaria: Actiniidae) from Argentina's southeastern coast

Temporal and spatial distribution of organochlorine pesticides (OCPs) and the organophosphate pesticide chlorpyrifos, one of the main insecticides used in Argentina, was evaluated in two populations of the sea anemone Bunodosoma zamponii living under different anthropological stressors: Las Delicias (LD) adjacent to a wastewater plant, and Punta Cantera (PC) a reference site. Pesticides were analyzed throughout the year in water, sediments and whole organisms. Chlorpyrifos represented 50% of the total pesticide found in water samples during winter. HCHs and drins were predominant in sediment samples, mainly in LD. Total pesticide concentration in anemones from LD was higher than those from PC during winter (mainly associated with HCHs, endosulfans, DDTs and chlorpyrifos levels), coincident with the main period of effluent discharge to the coast after pesticide applications and also the rainiest season. Dissimilarities among anemones populations could stem from a differential input of pesticides in each site and/or a contrasting physiological status of the populations.

Microplastics accumulation in functional feeding guilds and functional habit groups of freshwater macrobenthic invertebrates: Novel insights in a riverine ecosystem

Microplastics pose a major threat for aquatic ecosystems, but the contamination dynamics in organisms inhabiting freshwater ecosystems is still little studied. Largely used for biomonitoring, macrobenthic invertebrates provide a pivotal trophic resource for many fish and bird species. In this study, we investigated the microplastics contamination in a macrobenthic invertebrate community (2772 individuals belonging to 33 taxa identified) in a high-plain riverine ecosystem (Vipacco River, northeast Italy) and compared the amount of microplastics accumulated in functional feeding guilds/functional habit groups. Microplastics (cellulosic fibers associated with polyester) were found in 48.5% of the taxa, with the highest amount detected in the collector-gatherers, followed by predators. The collector-gatherers showed a significantly higher microplastic accumulation than the other functional feeding guilds, whereas there was no difference among the functional habit groups. The main source of microplastics pollution was most likely urban wastewater discharge points located along the river. Our study reports a novel approach about microplastic pollution assessment in lotic environments, as it focuses into the microplastic contamination dynamics in an entire macrobenthic invertebrate community perspective and underlines the need for further study.

Automated μFTIR Imaging Demonstrates Taxon-Specific and Selective Uptake of Microplastic by Freshwater Invertebrates

Microplastic particles can be deposited to sediments and subsequently ingested by benthic organisms. It is unknown to what extent ingestion of microplastic is taxon-specific or whether taxa can be selective toward certain types of microplastics. Here, we used state-of-the-art automated micro-Fourier-transform infrared (μFTIR) imaging and attenuated total reflectance FTIR spectroscopy to determine small-size (20-500 μm) and large-size (500-5000 μm) microplastic particles in sediments and a range of benthic invertebrate species sampled simultaneously from the Dommel River in the Netherlands. Microplastic number concentrations differed across taxa at the same locations, demonstrating taxon-specific uptake, whereas size distributions were the same across sediments and taxa. At the site with the highest concentration, microplastic occupied up to 4.0% of the gut volume of Asellidae. Particle shape distributions were often not statistically different between sediments and taxa, except for Astacidea at one of the locations where the proportion of particles with a length to width ratio >3 (i.e., fibers) was twice as high in sediments than in Astacidea. Acrylates/polyurethane/varnish was predominately found in sediments, while soft and rubbery polymers ethylene propylene diene monomer and polyethylene-chlorinated were the dominant polymers found in invertebrates. Microplastic polymer composition and thus polymer density differed significantly between invertebrates and their host sediment. Trophic transfer at the base of the food web appears to have a filter function with respect to microplastic particle types and shapes. Together with the very high ingestion rates, this has clear implications for ecological and human health risks, where uptake concerns edible species (e.g., Astacidea).

Lumbriculus variegatus (oligochaeta) exposed to polyethylene microplastics: biochemical, physiological and reproductive responses

Freshwater sediments are a repository of microplastics (MPs) resulting from inland anthropogenic activities. Benthic invertebrates, particularly endobenthic sediment-ingesting species such as the annelid Lumbriculus variegatus (blackworm), are commonly found in contaminated sediments where they likely find and ingest MPs. In the present study, L. variegatus was exposed to concentrations between 0.51 and 20 g kg^-1 dry sediment of four size-classes of irregularly-shaped polyethylene MPs (PE-MPs; size-class A: 32-63, B: 63-125, C: 125-250 and D: 250-500 μm) for 48 h to assess their sub-cellular responses to particles ingested, and for 28 days to determine chronic effects on worm's reproduction and biomass. After the short-term exposure (48 h), number of PE-MPs in blackworms' gut were related to MPs concentration in the sediment. In general, PE-MPs ingestion by blackworms induced depletion of their energy reserves (e.g., sugars in all size classes and lipids in the size-classes of PE-MPs > 125 μm), concomitant with the activation of antioxidant and detoxification mechanisms (increased level of total glutathione in all size-classes, and increased glutathione-S-transferase activity in PE-MPs > 250 μm), preventing lipid peroxidation. In addition, it was observed a reduction of aerobic energy production (decreased activity of the electron transport system) and a slight increase in neurotransmission (cholinesterase activity). After a long-term exposure (28 d), the presence and ingestion of PE-MPs did not affect reproduction and biomass of L. variegatus. The activation and efficiency of the antioxidant and detoxification mechanisms allied with the anatomy and physiology of L. variegatus, its feeding strategy and potentially dynamic ingestion/egestion capacity seem to be key features preventing MP deleterious effects under short- and chronic-exposures. Considering the MPs levels reported for freshwater sediments, and despite evidence of MPs ingestion and some sub-organismal effects, our results suggest no adverse impacts of PE-MPs contamination on L. variegatus populations fitness. This study applies an integrative approach in which data concerning the ingestion of different sized MPs and subsequent sub-cellular and apical responses are delivered, raising knowledge on endobenthic invertebrates' strategies to potentially overcome MP toxicity in field contaminated sites.

Estuarine sediment toxicity testing with an indigenous subtropical amphipod

This study reports on a sediment toxicity test developed with a native amphipod strain of Ptilohyale barbicornis where sediments from 10 estuarine stations along the western coastline of Taiwan were evaluated with respect to trace metals and PAHs. The test was validated by determining dose-response relationships for aqueous copper, and cadmium and sodium dodecyl sulfate as well as copper-spiked sediment, showing a sensitivity of P. barbicornis indicating its capability serving as a toxicity test species. A significant negative correlation between growth effects after 28 days of exposure to field-collected contaminated sediments and PAHs concentrations was observed. Similarly, the chronic toxicity test showed that growth was mostly inhibited compared to controls, body lengths in particular being significantly different from controls (p < 0.05). Various estuarine sediment pollutants in the quality guidelines can be further evaluated using P. barbicornis to understand their comprehensive biological effects and ecological risks.

Biological Traits and the Transfer of Persistent Organic Pollutants through River Food Webs

Freshwater organisms remain at risk from bioaccumulation and biomagnification of persistent organic pollutants (POPs), but factors affecting their transfer through food webs are poorly understood. Here, we investigate transfer pathways of polychlorinated biphenyls, polybrominated diphenyl ethers, and organochlorine through a river food web, assessing the distribution and flux between basal resources (n = 3), macroinvertebrates (n = 22), and fish (n = 1). We investigate the effects of biological traits on the observed patterns and use trait-based models to predict POP bioaccumulation. Transfer pathways differed among POPs and traits such as habitat affinity, feeding behavior, and body size explained some variation in POP burdens between organisms. Trait-based models indicated that relationships between POPs, trophic transfers, and traits were relatively well conserved across a wider array of river food webs. Although providing more consistent predictions of POP bioaccumulation than steady-state models, variability in bioaccumulation across food webs limited the accuracy of trait-model predictions. As some of the first data to illustrate how ecological processes alter the flux of pollutants through river food webs, these results reveal important links between POPs and contrasting energetic pathways. These data also show the utility of trait-based methods in the assessment of persistent contaminants, but further field validations are required.

A Bayesian framework for estimating parameters of a generic toxicokinetic model for the bioaccumulation of organic chemicals by benthic invertebrates: Proof of concept with PCB153 and two freshwater species

Toxicokinetic (TK) models are relevant and widely used to predict chemical concentrations in biological organisms. The importance of dietary uptake for aquatic invertebrates has been increasingly assessed in recent years. However, the model parameters are estimated on limited specific laboratory data sets that are bounded by several uncertainties. The aim of this study was to implement a Bayesian framework for simultaneously estimating the parameters of a generic TK model for benthic invertebrate species from all data collected. We illustrate our approach on the bioaccumulation of PCB153 by two species with different life traits and therefore exposure routes: Chironomus riparius larvae exposed to spiked sediment for 7 days and Gammarus fossarum exposed to spiked sediment and/or leaves for 7 days and then transferred to a clean media for 7 more days. The TK models assuming first-order kinetics were fitted to the data using Bayesian inference. The median model predictions and their 95% credibility intervals showed that the model fit the data well. From a methodological point of view, this paper illustrates that simultaneously estimating all model parameters from all available data by Bayesian inference, while considering the correlation between parameters and different types of data, is a real added value for TK modeling. Moreover, we demonstrated the ability of a generic TK model considering uptake and elimination routes as modules to add according to the availability of the data measured. From an ecotoxicological point of view, we show differences in PCB153 bioaccumulation between chironomids and gammarids, explained by the different life traits of these two organisms.

Bioaccumulation of polycyclic aromatic hydrocarbons by arctic and temperate benthic species

Increasing oil and gas activities may substantially increase chemical stress to benthic ecosystems in the Arctic, and it is necessary to evaluate such environmental risks in these systems. Risk assessment procedures for oil-related compounds (e.g., polycyclic aromatic hydrocarbons [PAHs]) should address differences in exposure between Arctic and temperate benthos. We compare for the first time the bioaccumulation of PAHs by Arctic benthic invertebrate species with that of temperate species, based on their biota-sediment accumulation factors (BSAFs). Measured PAH BSAFs were generally higher in temperate bivalves (Limecola balthica) than in Arctic bivalves (Macoma calcarea), whereas BSAFs in Arctic polychaetes (Nephtys ciliata) were higher than in temperate polychaetes (Alitta virens). Differences in measured BSAFs were explained by species-specific feeding modes and traits. However, modeled BSAFs revealed that steady state was not likely to be reached in the 28-d tests for all PAHs and organisms. Due to the low numbers of individuals, most species-specific parameters were too uncertain to reveal differences between Arctic and temperate species. The results of the present study suggest that data from temperate species could be used as a surrogate for Arctic species in risk assessment. Environ Toxicol Chem 2019;38:883-895. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Microplastic ingestion by riverine macroinvertebrates

Although microplastics are a recognised pollutant in marine environments, less attention has been directed towards freshwater ecosystems despite their greater proximity to possible plastic sources. Here, we quantify the presence of microplastic particles (MPs) in river organisms upstream and downstream of five UK Wastewater Treatment Works (WwTWs). MPs were identified in approximately 50% of macroinvertebrate samples collected (Baetidae, Heptageniidae and Hydropsychidae) at concentrations up to 0.14 MP mg tissue^-1 and they occurred at all sites. MP abundance was associated with macroinvertebrate biomass and taxonomic family, but MPs occurred independently of feeding guild and biological traits such as habitat affinity and ecological niche. There was no increase in plastic ingestion downstream of WwTW discharges averaged across sites, but MP abundance in macroinvertebrates marginally increased where effluent discharges contributed more to total runoff and declined with increasing river discharge. The ubiquity of microplastics within macroinvertebrates in this case study reveals a potential risk from MPs entering riverine food webs through at least two pathways, involving detritivory and filter-feeding, and we recommend closer attention to freshwater ecosystems in future research.

Fate and effects of sediment-associated triclosan in subtropical freshwater microcosms

Triclosan (TCS) is an antibacterial agent that is commonly used in personal care products. Because of its sediment-binding properties, TCS exposure presents a potential threat to sediment-dwelling aquatic organisms. Currently our knowledge of the fate and effects of sediment-associated TCS in aquatic systems is limited. To understand the impact of sediment-associated TCS, we used microcosms to assess effects of TCS exposure on a diverse range of organisms selected to mimic a subtropical community, with an exposure period of 28 days. We included the oligochaete freshwater worm Limnodrilus hoffmeisteri to evaluate the interaction between sediment-associated TCS and sediment-dwelling organisms, including potential loss of TCS from the sediment due to biological activity and bioaccumulation. Benthic macroinvertebrate presence significantly increased the TCS levels from 0.013 ± 0.007 μg/L to 0.613 ± 0.030 μg/L in the overlying water through biological activity, posing a potential additional risk to pelagic species, but it did not result in a significant reduction of the sediment concentration. Furthermore, worms accumulated TCS with estimated Biota-Sediment-Accumulation-Factors (BSAFs) ranging between 0.38-3.55. Other than for algae, TCS at environmental concentrations did not affect the survival of the introduced organisms, including the L. hoffmeisteri. Our results demonstrate that, although TCS at currently detected maximum concentration may not have observable toxic effects on the benthic macroinvertebrates in the short term, it can lead to bioaccumulation in worms.

Microplastic Effect Thresholds for Freshwater Benthic Macroinvertebrates

Now that microplastics have been detected in lakes, rivers, and estuaries all over the globe, evaluating their effects on biota has become an urgent research priority. This is the first study that aims at determining the effect thresholds for a battery of six freshwater benthic macroinvertebrates with different species traits, using a wide range of microplastic concentrations. Standardized 28 days single species bioassays were performed under environmentally relevant exposure conditions using polystyrene microplastics (20-500 μm) mixed with sediment at concentrations ranging from 0 to 40% sediment dry weight (dw). Microplastics caused no effects on the survival of Gammarus pulex, Hyalella azteca, Asellus aquaticus, Sphaerium corneum, and Tubifex spp. and no effects were found on the reproduction of Lumbriculus variegatus. No significant differences in growth were found for H. azteca, A. aquaticus, S. corneum, L. variegatus, and Tubifex spp. However, G. pulex showed a significant reduction in growth (EC₁₀ = 1.07% sediment dw) and microplastic uptake was proportional with microplastic concentrations in sediment. These results indicate that although the risks of environmentally realistic concentrations of microplastics may be low, they still may affect the biodiversity and the functioning of aquatic communities which after all also depend on the sensitive species.

Microplastic Effect Thresholds for Freshwater Benthic Macroinvertebrates

Now that microplastics have been detected in lakes, rivers, and estuaries all over the globe, evaluating their effects on biota has become an urgent research priority. This is the first study that aims at determining the effect thresholds for a battery of six freshwater benthic macroinvertebrates with different species traits, using a wide range of microplastic concentrations. Standardized 28 days single species bioassays were performed under environmentally relevant exposure conditions using polystyrene microplastics (20-500 μm) mixed with sediment at concentrations ranging from 0 to 40% sediment dry weight (dw). Microplastics caused no effects on the survival of Gammarus pulex, Hyalella azteca, Asellus aquaticus, Sphaerium corneum, and Tubifex spp. and no effects were found on the reproduction of Lumbriculus variegatus. No significant differences in growth were found for H. azteca, A. aquaticus, S. corneum, L. variegatus, and Tubifex spp. However, G. pulex showed a significant reduction in growth (EC₁₀ = 1.07% sediment dw) and microplastic uptake was proportional with microplastic concentrations in sediment. These results indicate that although the risks of environmentally realistic concentrations of microplastics may be low, they still may affect the biodiversity and the functioning of aquatic communities which after all also depend on the sensitive species.

Endocrine disruption in aquatic systems: up-scaling research to address ecological consequences

Endocrine‐disrupting chemicals (EDCs) can alter biological function in organisms at environmentally relevant concentrations and are a significant threat to aquatic biodiversity, but there is little understanding of exposure consequences for populations, communities and ecosystems. The pervasive nature of EDCs within aquatic environments and their multiple sub‐lethal effects make assessments of their impact especially important but also highly challenging. Herein, we review the data on EDC effects in aquatic systems focusing on studies assessing populations and ecosystems, and including how biotic and abiotic processes may affect, and be affected by, responses to EDCs. Recent research indicates a significant influence of behavioural responses (e.g. enhancing feeding rates), transgenerational effects and trophic cascades in the ecological consequences of EDC exposure. In addition, interactions between EDCs and other chemical, physical and biological factors generate uncertainty in our understanding of the ecological effects of EDCs within aquatic ecosystems. We illustrate how effect thresholds for EDCs generated from individual‐based experimental bioassays of the types commonly applied using chemical test guidelines [e.g. Organisation for Economic Co‐operation and Development (OECD)] may not necessarily reflect the hazards associated with endocrine disruption. We argue that improved risk assessment for EDCs in aquatic ecosystems urgently requires more ecologically oriented research as well as field‐based assessments at population‐, community‐ and food‐web levels.

The Effect of Microplastic on the Uptake of Chemicals by the Lugworm Arenicola marina (L.) under Environmentally Relevant Exposure Conditions

It has been hypothesized that ingestion of microplastic increases exposure of aquatic organisms to hydrophobic contaminants. To date, most laboratory studies investigated chemical transfer from ingested microplastic without taking other exposure pathways into account. Therefore, we studied the effect of polyethylene (PE) microplastic in sediment on PCB uptake by Arenicola marina as a model species, quantifying uptake fluxes from all natural exposure pathways. PCB concentrations in sediment, biota lipids (C_lip) and porewater measured with passive samplers were used to derive lipid-normalized bioaccumulation metrics C_lip, Biota sediment accumulation factor (BSAF), Bioaccumulation factor (BAF) and the Biota plastic accumulation factor (BPAF). Small effects of PE addition were detected suggesting slightly increased or decreased bioaccumulation. However, the differences decreased in magnitude dependent on the metric used to assess bioaccumulation, in the order: C_lip > BSAF > BPAF > BAF, and were nonsignificant for BAF. The fact that BAF, that is, normalization of C_lip on porewater concentration, largely removed all effects of PE, shows that PE did not act as a measurable vector of PCBs. Biodynamic model analysis confirmed that PE ingestion contributed marginally to bioaccumulation. This work confirmed model-based predictions on the limited relevance of microplastic for bioaccumulation under environmentally realistic conditions, and illustrated the importance of assessing exposure through all media in microplastic bioaccumulation studies.

Bioaccumulation of polycyclic aromatic hydrocarbons, polychlorinated biphenyls and hexachlorobenzene by three Arctic benthic species from Kongsfjorden (Svalbard, Norway)

The predicted expansion of oil and gas (O&G) activities in the Arctic urges for a better understanding of impacts of these activities in this region. Here we investigated the influence of location, feeding strategy and animal size on the bioaccumulation of Polycyclic Aromatic Hydrocarbons (PAHs), Polychlorinated Biphenyls (PCBs) and Hexachlorobenzene (HCB) by three Arctic benthic species in Kongsfjorden (Svalbard, Norway). No toxicity was expected based on biota PAH critical body residues. Biota PCB levels were mainly below limit of detection, whereas samples were moderately polluted by HCB. PAH concentrations in biota and Biota Sediment Accumulation Factors (BSAFs) were generally higher in Blomstrandhalvøya than in Ny-Ålesund, which was explained by a higher abundance of black carbon in Ny-Ålesund harbour. BSAFs differed significantly among species and stations. We conclude that contaminant body residues are a less variable and more straightforward monitoring parameter than sediment concentrations or BSAFs in Arctic benthos.

Evaluating the Relationship between Equilibrium Passive Sampler Uptake and Aquatic Organism Bioaccumulation

This Critcal Review evaluates passive sampler uptake of hydrophobic organic contaminants (HOCs) in water column and interstitial water exposures as a surrogate for organism bioaccumulation. Fifty-seven studies were found where both passive sampler uptake and organism bioaccumulation were measured and 19 of these investigations provided direct comparisons relating passive sampler uptake and organism bioaccumulation. Polymers compared included low-density polyethylene (LDPE), polyoxymethylene (POM), and polydimethylsiloxane (PDMS), and organisms ranged from polychaetes and oligochaetes to bivalves, aquatic insects, and gastropods. Regression equations correlating bioaccumulation (C_L) and passive sampler uptake (C_PS) were used to assess the strength of observed relationships. Passive sampling based concentrations resulted in log-log predictive relationships, most of which were within one to 2 orders of magnitude of measured bioaccumulation. Mean coefficients of determination (r²) for LDPE, PDMS, and POM were 0.68, 0.76, and 0.58, respectively. For the available raw, untransformed data, the mean ratio of C_L and C_PS was 10.8 ± 18.4 (n = 609). Using passive sampling as a surrogate for organism bioaccumulation is viable when biomonitoring organisms are not available. Passive sampling based estimates of bioaccumulation provide useful information for making informed decisions about the bioavailability of HOCs.