Here, we examined the combinational effect of ocean acidification (OA) and mercury (Hg) in the planktonic copepod Pseudodiaptomus annandalei in cross-factored response to different pCO₂ (400, 800 μatm) and Hg (control, 1.0 and 2.5 μg/L) exposures for three generations (F0–F2), followed by single-generation recovery (F3) under clean condition. Several phenotypic traits and Hg accumulation were analyzed for F0–F3. Furthermore, shotgun-based quantitative proteomics was performed for F0 and F2. Our results showed that OA insignificantly influenced the traits. During F0–F2, combined exposure reduced Hg accumulation as compared with the counterpart Hg treatment, supporting the mitigating effect of OA on Hg toxicity in copepods. Proteomics analysis indicated that the copepods probably increased energy production/storage and stress response to ensure physiological resilience against OA. However, Hg induced many toxic events (e.g., energy depletion and degenerated organomorphogenesis/embryogenesis for F0; cell cycle arrest and detrimental stress-defense for F2), which were translated to the population-level adverse outcome, i.e., compromised growth/reproduction. Particularly, compensatory proteome response was identified (e.g., increased immune defense for F0; energetic compensation and enhanced embryogenesis for F2), accounting for a negative interaction between OA and Hg. Together, this study provides the molecular mechanisms behind the effects of OA and Hg pollution in marine copepods.

Stressors associated with climate change and contaminants, resulting from the activities of humans, are affecting organisms and ecosystems globally. Previous studies suggest that the unique characteristics of polar biota, such as slower metabolisms and growth, and the generally stable conditions in their natural environment, cause higher susceptibility to contamination and climate change than those in temperate and tropical areas. We investigated the effects of increased temperature and decreased salinity on copper toxicity in four subantarctic marine invertebrates using realistic projected conditions under a future climatic change scenario for this region. We hypothesised that these relatively subtle shifts in environmental stressors would impact the sensitivity of cold-adapted species to copper. The four test species were: a copepod Harpacticus sp.; isopod Limnoria stephenseni; flatworm Obrimoposthia ohlini; and bivalve Gaimardia trapesina. These species occupy a range of ecological niches, spanning intertidal and subtidal nearshore zones. We predicted that species would differ in their tolerance to stressors, depending on where they occurred within this ecological gradient. Organisms were exposed to the multiple stressors in a factorial design in laboratory based toxicity tests. Sensitivity estimates for copper (LC50) were calculated using a novel statistical approach which directly assessed the impacts of the multiple stressors. In three of the four species tested, sensitivity to copper was amplified by small increases in temperature (2-4 °C). The effects of salinity were more variable but a decrease of as little as 2 ppt caused a significant effect in one species. This study provides some of the first evidence that high latitude species may be at increased risk from contaminants under projected future climate conditions. This interaction, between contaminants and the abiotic environment, highlights a potential pathway to biodiversity loss under a changing climate.

The distribution, feeding ecology and microplastic contamination were assessed in different ontogenetic phases of Haemulidae species inhabiting the Goiana Estuary, over a seasonal cycle. Pomadasys ramosus and Haemulopsis corvinaeformis are estuarine dependent species that use habitats with specific environmental conditions each season. Pomadasys ramosus was found in the upper and middle estuaries during the rainy season, when salinity showed the lowest values. Haemulopsis corvinaeformis was found in the lower estuary during the dry season, when salinity increased in the estuary. Juveniles of P. ramosus are zooplanktivores, feeding mainly on calanoid copepods. Sub-adults and adults are zoobenthivores, feeding on invertebrates associated to the bottom, mainly Polychaeta. Juveniles of H. corvinaeformis were not found in the main channel, but sub-adults and adults showed a zoobenthivore habit, feeding mainly on Anomalocardia flexuosa (Mollusca: Bivalvia). Dietary shifts along the life cycle and the spatio-temporal relationship between their distribution and the availability of microplastics along the estuary seem to have a strong influence in the ingestion of microfilaments. The highest average ingestion of microfilaments by P. ramosus coincided with the peak of ingestion of Polychaeta by sub-adults in the upper estuary during the late rainy season. For H. corvinaeformis the highest ingestion of microfilaments coincided with the peak of ingestion of A. flexuosa by adults in the lower estuary during the late dry season. Such contamination might be attributed to the time when these phases shifted to a more diverse diet and began to forage on benthic invertebrates. Research on microplastic contamination must consider species-specific behaviour, since the intake of microplastics is dependent on patterns of distribution and trophic guild within fish assemblages.

Studying long-term trends of contaminants in Arctic biota is essential to better understand impacts of anthropogenic activities and climate change on the exposure of sensitive species and marine ecosystems. We concurrently measured temporal changes (2006–2014) in mercury (Hg) contamination of little auks (Alle alle; the most abundant Arctic seabird) and in their major zooplankton prey species (Calanoid copepods, Themisto libellula, Gammarus spp.). We found an increasing contamination of the food-chain in East Greenland during summer over the last decade. More specifically, bird contamination (determined by body feather analyses) has increased at a rate of 3.4% per year. Conversely, bird exposure to Hg during winter in the northwest Atlantic (determined by head feather analyses) decreased over the study period (at a rate of 1.5% per year), although winter concentrations remained consistently higher than during summer. By combining mercury levels measured in birds and zooplankton to isotopic analyses, our results demonstrate that inter-annual variations of Hg levels in little auks reflect changes in food-chain contamination, rather than a reorganization of the food web and a modification of seabird trophic ecology. They therefore underline the value of little auks, and Arctic seabirds in general, as bio-indicators of long-term changes in environmental contamination.

The focus of the present study was to find the relationship between concentrations of bisphenol A (BPA), 4-tert-octylphenol (OP) and 4-nonylphenol (NP) in zooplankton and seasonal changes in the composition and biomass of particular zooplankton taxa in the Gulf of Gdansk (Southern Baltic) in the years 2011–2012. Assays of BPA, OP and NP in water and zooplankton samples were performed using the HPLC/FL system. High mean concentrations of the studied compounds, determined in spring (405.9 (BPA); 25.7 (OP); 111.2 (NP) ng g−1 dw), can be linked to the high proportion of meroplankton in that season. Rotifera also had an influence on the rise in concentrations of the studied compounds but to a lesser degree, while the lowest concentrations (determined in summer) can be associated with the high participation of Copepoda and Cladocera in zooplankton biomass. It was also observed that juvenile forms can be more susceptible to accumulating endocrine disrupting compounds (EDCs). This is indicated by the positive correlation between BPA concentration in zooplankton and the proportion of Copepoda nauplii biomass in spring (r = 0.90; p < 0.05). In most cases, greater zooplankton biomass accumulated higher concentrations and loads of the studied compounds. With biomass growth (to 123.32 μg m−3), the bioconcentration factor also rose (to max 46.1·103), demonstrating that unlike typical hydrophobic compounds the studied EDCs do not become “diluted” in zooplankton biomass. The highest BPA concentrations from all compounds may be connected with anthropogenic sources located in the coastal zone.

Identifying general response patterns to contamination in the environment is critical for reliable assessments of ecosystem health. However, it is not often clear if there are biases in the information used to understand general effects of contamination. To investigate this we conducted a review of 314 studies that experimentally manipulated contaminants and measured the effects on marine invertebrate taxa. The majority of studies investigated the effects of metals (54%) on individual taxa (mainly bivalves, amphipods, copepods). Ecologically relevant responses to contamination were measured in only 22% of the studies. A meta-analysis using studies that measured ecological responses to copper illustrated a general negative effect of copper and highlighted the bias towards field or laboratory experiments that measure community or individual-level responses. There is a need for diversification of studies that investigate the ecological effects of contamination as an important advancement in ecotoxicology and ecological research and environmentally relevant risk assessments.

Contraceptive drugs are nowadays found in aquatic environments around the globe. Particularly, 17α-ethinylestradiol (EE2) may act even at low concentrations, such as those recorded in natural ecosystems. We evaluated the physiological effects of EE2 on cyclopoids and calanoids, common copepods in both marine and freshwater communities. We used three EE2 concentrations and assessed its impact on activity of different physiological endpoints: Acetylcholinesterase (neurotransmission), Glutathione S-transferase (detoxifying system), and Caspase-3 (apoptosis). While EE2 exerts, distinctive effect on detoxifying and apoptotic systems, no effect on AChE was observed at environmental doses. Our results show that EE2 exposure affects differently copepod physiology endpoints, altering moulting process, adult recruitment in calanoids and calanoid to cyclopoid ratio. The ecological consequences of this underlying physiological process may affect since life history to population and community structures, and this represent a new aspects of this xenobiotic in natural systems.

Despite the great concerns about dioxins in the marine environments, the biokinetics and bioaccumulation of these compounds in marine organisms remains little known. Using radioactive tracers the aqueous uptake, dietary assimilation efficiency, and elimination of dioxins were measured in marine phytoplankton, copepods and seabream. The calculated uptake rate constant of dioxins decreased with increasing trophic levels, whereas the dietary assimilation efficiency (AE) was 28.5–57.6% in the copepods and 36.6–70.2% in the fish. The dietary AE was highly dependent on the food concentrations and food type. The elimination rate constant of dioxin in the copepods varied with different exposure pathways as well as food concentration and food type. Biokinetic calculation showed that dietary accumulation was the predominant pathway for dioxin accumulation in marine copepods and fish. Aqueous uptake can be an important pathway only when the bioconcentration of dioxins in the phytoplankton was low.

The study presented here searched for the level of taxonomic resolution required to detect the effects of low-level chronic pollution on estuarine meiobenthic communities. Meiofauna from two sites, with special attention to harpacticoid copepods, was analysed at different taxonomic levels of aggregation using uni- and multivariate methods. Adaptation processes that could buffer biodiversity disruptions were also considered through the analysis of fitness-related and tolerance traits in the harpacticoid copepod Paronychocamptus nanus. Results showed that uni- and multivariate analyses could be inadequate when assessing subtle anthropogenic contamination. Instead, the assessment of inter-population differences in tolerance to the main source of stress rises as a required procedure if potential effects of this type of contamination are being investigated. Specifically, a 96 h acute toxicity test performed with populations from the affected site appears as a faster and reliable general tool to assess impacts of low-level chronic pollution in estuaries.

Because of environmental and societal concerns, new strategies are being developed to mitigate the effects of road salt. These include new deicers that are alternatives to or mixtures with the most common road salt, sodium chloride (NaCl), improved techniques and equipment, and biotic mitigation methods. Using outdoor mesocosms, we investigated the impacts of NaCl and two common alternatives, magnesium chloride (MgCl₂) and calcium chloride (CaCl₂) on freshwater communities. We also investigated the mitigation ability of a common macrophyte, Elodea. We hypothesized that road salt exposure reduces filamentous algae, zooplankton, and macrocrustaceans, but results in increases in phytoplankton and gastropods. We also hypothesized that MgCl₂ is the most toxic salt to communities, followed by CaCl₂, and then NaCl. Lastly, we hypothesized that macrophytes mitigate some of the effects of road salt, specifically the effects on primary producers. We found that all three salts reduced filamentous algal biomass and amphipod abundance, but only MgCl₂ reduced Elodea biomass. MgCl₂ had the largest and longest lasting effects on zooplankton, specifically cladocerans and copepods, which resulted in a significant increase in phytoplankton and rotifers. CaCl₂ increased ostracods and decreased snail abundance, but NaCl increased snail abundance. Lastly, while we did not find many interactions between road salt and macrophyte treatments, macrophytes did counteract many of the salt effects on producers, leading to decreased phytoplankton, increased filamentous algae, and altered abiotic responses. Thus, at similar chloride concentrations, NaCl alternatives, specifically MgCl₂, are not safer for aquatic ecosystems and more research is needed to find safer road management strategies to protect freshwater ecosystems.