Lead exposure is related to higher infection rate with the gapeworm in Norwegian house sparrows (Passer domesticus).

Anthropogenic pollution is identified as an important threat to bird and other wildlife populations. Many metals and toxic elements, along with poly- and perfluoroalkyl substances (PFASs) are known to induce immunomodulation and have previously been linked to increased pathogen prevalence and infectious disease severity. In this study, the house sparrow (Passer domesticus) was investigated at the coast of Helgeland in northern Norway. This population is commonly infected with the parasitic nematode "gapeworm" (Syngamus trachea), with a prevalence of 40-60 % during summer months. Gapeworm induces severe respiratory disease in birds and has been previously demonstrated to decrease survival and reproductive success in wild house sparrows. The aim of this study was to investigate whether a higher exposure to pollution with PFASs, metals and other elements influences gapeworm infection in wild house sparrows. We conducted PFASs and elemental analysis on whole blood from 52 house sparrows from Helgeland, including analyses of highly toxic metals such as lead (Pb), mercury (Hg) and arsenic (As). In addition, we studied gapeworm infection load by counting the parasite eggs in faeces from each individual. We also studied the expression of microRNA 155 (miR155) as a key regulator in the immune system. Elevated blood concentrations of Pb were found to be associated with an increased prevalence of gapeworm infection in the house sparrow. The expression of miR155 in the plasma of the house sparrow was only weakly associated with Pb. In contrast, we found relatively low PFASs concentrations in the house sparrow blood (∑ PFASs 0.00048-354 µg/L) and PFASs were not associated to miR155 nor infection rate. The current study highlights the potential threat posed by Pb as an immunotoxic pollutant in small songbirds.

Species and reproductive status influence element concentrations in bat fur.

To assess the impact of increasing pollutant levels on wildlife, we measured chemical contaminant loads in bats with different habitat and dietary preferences. Samples were taken from the fur of bats (Eptesicus nilssonii, Myotis brandtii, Myotis mystacinus and Plecotus auritus) to measure concentrations of 55 elements by inductively coupled plasma mass spectrometry (ICP-MS). Variations in element concentrations between different bat groups (species, sex, reproductive status) were analysed with a focus on arsenic (As), mercury (Hg) and lead (Pb) as these are known to cause specific health concerns in wildlife. For M. brandtii we found the highest As concentrations, especially in lactating bats, with a maximum exceeding those from other studies where bats had compromised health. Whereas for M. mystacinus there was a negative correlation between body condition index (BCI) and As concentration, indicating a potential danger for bats in the study area. In M. mystacinus and M. brandtii Hg concentrations were higher for sixteen individuals than in other studies where bats suffered genotoxic effects, although median levels were still below this threshold. Lactating bats from P. auritus and M. brandtii had higher Hg concentrations than bats of other reproductive status, which could endanger offspring as Hg can be transferred through lactation. In females from M. mystacinus Pb concentrations were more than three times higher compared to males. There was also a negative correlation between Pb concentration and BCI, which could mean that Pb has an adverse effect on health. Although many other biotic and abiotic factors should be considered, some of the variations in element concentrations could be due to different behaviours (foraging, roosting, etc.) in the studied species. The high levels of chemical contamination in some of the bats in our study, particularly reproductive individuals, is of conservation concern as bats are important agents for insect control.

The metabolome of pink-footed goose: Heavy metals and lipid metabolism.

Wildlife is exposed to mixtures of environmental contaminants that affect health and population dynamics. Exposure to toxic heavy metals originating from anthropogenic sources may exert metabolic effects at even low exposure concentrations. Here we investigated the relationships between heavy metal exposure and metabolic changes in the migratory bird pink-footed goose (Anser brachyrhynchus). We used blood pellet and blood plasma samples from 27 free-ranging pink-footed geese to study heavy metal (Cd, Cr, Hg, and Pb) exposure in relation to the metabolome. The results relate blood concentrations of Cd (range: 0.218-1.09 ng/g), Cr (range: 0.299-5.60 ng/g), and Hg (range: 2.63-6.00 ng/g) to signal areas of fatty acids and other lipids, while no correlations were identified for Pb level (range: 21.0-64.2 ng/g) exposure. Lipid signal areas were negatively associated with concentrations of Cr and positively associated with Hg exposure (both p < 0.05). α-Linolenic acid and 9-oxononanoic acid were negatively correlated to Cr exposure (both p < 0.05) and were related in the α-linolenic acid metabolism pathway. Compared to known thresholds for aviary species, the heavy metal concentrations are below levels of toxicity, which may explain the low number of metabolites that significantly change. Nevertheless, the heavy metal exposure is still correlated to changes in the lipid metabolism that may reduce migrating birds' breeding success and increase mortality for an exposed part of the population.

Occurrence and tissue distribution of 33 legacy and novel per- and polyfluoroalkyl substances (PFASs) in Baikal seals (Phoca sibirica).

Per- and polyfluoroalkyl substances (PFASs) are bioaccumulative and associated with adverse effects in both wildlife and humans. The occurrence of 33 PFASs was assessed in the plasma, liver, blubber, and brain of 18 Baikal seals (Phoca sibirica) (16 pups and 2 adult females) from Lake Baikal, Russia (in 2011). Of the 33 congeners analysed for: perfluorooctanosulfonic acid (PFOS), 7 long chain perfluoroalkyl carboxylic acids (C8-C14 PFCAs) and 1 branched PFCA (perfluoro-3,7-dimethyloctanoic acid; P37DMOA) were most frequently detected. The PFASs in plasma and liver with the highest median concentrations were legacy congeners: perfluoroundecanoic acid (PFUnA; plasma: 11.2 ng/g w.w.; liver: 7.36 ng/g w.w.), PFOS (plasma: 8.67 ng/g w.w.; liver: 9.86 ng/g w.w.), perfluorodecanoic acid (PFDA; plasma: 5.13 ng/g w.w.; liver: 6.69 ng/g w.w.), perfluorononanoic acid (PFNA; plasma: 4.65 ng/g w.w.; liver: 5.83 ng/g w.w.) and perfluorotridecanoic acid (PFTriDA; plasma: 4.29 ng/g w.w.; liver: 2.55 ng/g w.w.). PFASs were detected in the brain of Baikal seals, indicating that PFASs cross through the blood-brain barrier. In blubber, the majority of PFASs were detected in low abundance and concentrations. In contrast to legacy PFASs, novel congeners (e.g., Gen X) were either detected infrequently or not found in Baikal seals. The worldwide occurrence of PFASs in pinnipeds was compared and lower median concentrations of PFOS were observed in Baikal seals relative to other pinnipeds. Conversely, similar concentrations of long chain PFCAs were found in Baikal seals compared to other pinnipeds. Furthermore, human exposure was assessed by estimating weekly intakes (EWI) of PFASs through Baikal seal consumption. Although PFASs concentrations were comparatively low relative to other pinnipeds, consumption of Baikal seal could exceed current regulatory guidelines.

Testosterone and persistent organic pollutants in East Greenland male polar bears (Ursus maritimus).

Legacy persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) are chemicals that undergo long-range transport to the Arctic. These chemicals possess endocrine disruptive properties raising concerns for development and reproduction. Here, we report the relationship between concentrations of testosterone (T) and persistent organic pollutant (POPs) in 40 East Greenland male polar bears (Ursus maritimus) sampled during January to September 1999-2001. The mean ± standard concentrations of blood T were 0.31 ± 0.49 (mean ± SD) ng/mL in juveniles/subadults (n = 22) and 3.58 ± 7.45 ng/mL in adults (n = 18). The ∑POP concentrations (mean ± SD) in adipose tissue were 8139 ± 2990 ng/g lipid weight (lw) in juveniles/subadults and 11,037 ± 3950 ng/g lw in adult males, respectively, of which Σpolychlorinated biphenyls (ΣPCBs) were found in highest concentrations. The variation in T concentrations explained by sampling date (season), biometrics and adipose tissue POP concentrations was explored using redundancy analysis (RDA). The results showed that age, body length, and adipose lipid content in adult males contributed (p = 0.02) to the variation in POP concentrations. However, although some significant relationships between individual organochlorine contaminants and T concentrations in both juveniles/subadults and adult polar bears were identified, no significant relationships (p = 0.32) between T and POP concentrations were identified by the RDAs. Our results suggest that confounders such as biometrics and reproductive status may mask the endocrine disruptive effects that POPs have on blood T levels in male polar bears, demonstrating why it can be difficult to detect effects on wildlife populations.

A risk assessment review of mercury exposure in Arctic marine and terrestrial mammals.

There has been a considerable number of reports on Hg concentrations in Arctic mammals since the last Arctic Monitoring and Assessment Programme (AMAP) effort to review biological effects of the exposure to mercury (Hg) in Arctic biota in 2010 and 2018. Here, we provide an update on the state of the knowledge of health risk associated with Hg concentrations in Arctic marine and terrestrial mammal species. Using available population-specific data post-2000, our ultimate goal is to provide an updated evidence-based estimate of the risk for adverse health effects from Hg exposure in Arctic mammal species at the individual and population level. Tissue residues of Hg in 13 species across the Arctic were classified into five risk categories (from No risk to Severe risk) based on critical tissue concentrations derived from experimental studies on harp seals and mink. Exposure to Hg lead to low or no risk for health effects in most populations of marine and terrestrial mammals, however, subpopulations of polar bears, pilot whales, narwhals, beluga and hooded seals are highly exposed in geographic hotspots raising concern for Hg-induced toxicological effects. About 6% of a total of 3500 individuals, across different marine mammal species, age groups and regions, are at high or severe risk of health effects from Hg exposure. The corresponding figure for the 12 terrestrial species, regions and age groups was as low as 0.3% of a total of 731 individuals analyzed for their Hg loads. Temporal analyses indicated that the proportion of polar bears at low or moderate risk has increased in East/West Greenland and Western Hudson Bay, respectively. However, there remain numerous knowledge gaps to improve risk assessments of Hg exposure in Arctic mammalian species, including the establishment of improved concentration thresholds and upscaling to the assessment of population-level effects.

Element concentrations, histology and serum biochemistry of arctic char (Salvelinus alpinus) and shorthorn sculpins (Myoxocephalus scorpius) in northwest Greenland.

The increasing exploratory efforts in the Greenland mineral industry, and in particular, the proposed rare earth element (REE) mining projects, requires an urgent need to generate data on baseline REE concentrations and their potential environmental impacts. Herein, we have investigated REE concentrations in anadromous Arctic char (Salvelinus alpinus) and shorthorn sculpins (Myoxocephalus scorpius) from uncontaminated sites in Northwest Greenland, along with the relationships between the element concentrations in gills and liver, and gill histology and serum biochemical parameters. Concentrations of arsenic, silver, cadmium, cerium, chromium, copper, dysprosium, mercury, lanthanum, neodymium, lead, selenium, yttrium, and zinc in gills, liver and muscle are presented. No significant statistical correlations were observed between element concentrations in different organs and gill histology or serum biochemical parameters. However, we observed positive relationships between age and histopathology, emphasizing the importance of including age as a co-variable in histological studies of fish. Despite no element-induced effects were observed, this study is considered an important baseline study, which can be used as a reference for the assessment of impacts of potential future REE mine sites in Greenland.

Oil-mediated oxidative-stress responses in a keystone zooplanktonic species, Calanus finmarchicus.

The copepod Calanus finmarchicus is an ecologically important species in the North Atlantic, Norwegian and Barents seas. Accidental or continuous petroleum pollution from oil and gas production in these seas may pose a significant threat to this low trophic level keystone species. Responses related to oxidative stress, protein damage and lipid peroxidation were investigated in C. finmarchicus exposed to a water-accommodated fraction (WAF) of a naphthenic North Atlantic crude oil. The exposure concentration corresponded to 50% of the 96 h LC50, and samples were obtained at 0, 24, 48, 72 and 96 h after exposure initiation. Gene expressions (superoxide dismutase, catalase, glutathione S-transferase, glutathione synthetase, heat shock protein 70 and 90, ubiquitin and cytochrome P-450 330A1), enzyme activities (superoxide dismutase, catalase, glutathione S-transferase) and concentrations of total glutathione and malondialdehyde were analyzed. Gene expression analyses showed no differences between controls and the exposed animals, however significantly higher glutathione S-transferase activity and malondialdehyde concentrations were found in the exposed group, suggests lipid peroxidation as main toxic effect.

Exposure to low environmental copper concentrations does not affect survival and development in Atlantic cod (Gadus morhua) early life stages.

In this study we investigated potential impacts of Cu exposure at low, environmentally relevant, concentrations on early live stages of Atlantic cod (Gadus morhua). Cod embryos and larvae were exposed to 0.5 µg/L (low), 2 µg/L (medium), and 6 µg/L (high) Cu from 4 to 17 days post fertilisation (dpf). Hatching success, mortality, oxygen consumption, biometric traits, and malformations were determined. A dynamic energy budget (DEB) model was applied to identify potential impacts on bioenergetics. A positive correlation was found between Cu exposure concentrations and Cu body burden in eggs, but not in larvae. The tested concentrations did not increase mortality in neither embryos nor larvae, or larvae deformations. Further, the DEB model did not indicate effects of the tested Cu concentrations.

Effects of marine mine tailing exposure on the development, growth, and lipid accumulation in Calanus finmarchicus.

Marine tailing disposal (MTD) is sometimes practiced as an alternative to traditional mine tailing deposition on land. Environmental challenges connected to MTD include spreading of fine particulate matter in the water column and the potential release of metals and processing chemicals. This study investigated if tailing exposure affects the marine copepod Calanus finmarchicus, and whether effects are related to exposure to mineral particles or the presence of metals and/or processing chemicals in the tailings. We investigated the impacts of three different tailing compositions: calcium carbonate particles with and without processing chemicals and fine-grained tailings from a copper ore. Early life stages of C. finmarchicus were exposed over several developmental stages to low and high suspension concentrations for 15 days, and their development, oxygen consumption and biometry determined. The data was fitted in a dynamic energy budget (DEB) model to determine mechanisms underlying responses and to understand the primary modes of action related to mine tailing exposure. Results show that copepods exposed to tailings generally exhibited slower growth and accumulated less lipids. The presence of metals and processing chemicals did not influence these responses, suggesting that uptake of mineral particles was responsible for the observed effects. This was further supported by the applied DEB model, confirming that ingestion of tailing particles while feeding can result in less energy being available for growth and development.

A targeted mass spectrometry immunoassay to quantify osteopontin in fresh-frozen breast tumors and adjacent normal breast tissues.

Osteopontin (OPN) is a multifunctional protein that can activate cell-signaling pathways and lead to cancer development and metastasis. Elevated OPN expression was reported in different cancer types, including breast tumors. Here, we present a new immuno-mass spectrometry method for OPN quantification in fresh-frozen malignant and adjacent normal human breast tissues. For quantification we used two proteotypic peptides: OPN-peptide-1 and OPN-peptide-2. Peptide concentrations were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in multiple reaction monitoring (MRM) mode with stable isotope standards (SIS) and immuno-affinity enrichment for isolation of OPN peptides. Based on the OPN-peptide-1, the average OPN concentration in normal breast tissue was 19.42 µg/g, while the corresponding level in breast tumors was 603.9 µg/g. Based on OPN-peptide-2, the average concentration in normal breast tissue was 19.30 µg/g and in breast tumors 535.0 µg/g. In ER/PR/HER2(-) patients the OPN levels in breast tumors were significantly higher than in corresponding normal breast tissue samples, whereas in the single ER/PR/HER2(+) patient the OPN concentration in tumor samples was lower than in normal breast tissue sample. In conclusion, the current method is considered promising for the quantification of OPN in research and in clinical settings and should be further studied in breast cancer patients. SIGNIFICANCE: A new immuno-mass spectrometry method was successfully developed and applied to determine OPN concentrations in malignant tumor and normal breast tissues from six patients, and the method is promising for OPN quantification in both research and clinical settings.

Using an apex predator for large-scale monitoring of trace element contamination: Associations with environmental, anthropogenic and dietary proxies.

Understanding the levels and drivers of contamination in top predators is important for their conservation and eventual use as sentinels in environmental monitoring. Therefore, metals and trace elements were analyzed in feathers of Bonelli's eagles (Aquila fasciata) from southern Portugal in 2007-2013, where they are believed to be exposed to a wide range of contamination sources such as agricultural land uses, urban areas, active and abandoned mines and a coal-fired power plant. We focused on concentrations of aluminum (Al), arsenic (As), copper (Cu), chromium (Cr), mercury (Hg), lead (Pb), selenium (Se) and zinc (Zn), as these contaminants are potentially associated with those sources and are known to pose a risk for terrestrial vertebrates. Stable isotope values of nitrogen (δ15N: 15N/14N), carbon (δ13C: 13C/12C) and sulphur (δ34S: 34S/32S) were used as dietary proxies to control for potential effects of prey composition on the contamination pattern. The spatial distribution of potential contamination sources was quantified using geographic information systems. Concentrations of Hg in the southern part of the study area were above a reported toxicity threshold for raptors, particularly in territories closer to a coal-fired power plant at Sines, showing that contamination persisted after a previous assessment conducted in the 1990s. Hg and Se levels were positively correlated with δ15N, which indicates biomagnification. Concentrations of As, Cr, Cu, Pb and Zn were generally low and unrelated to mining- or industrial activities, indicating low environmental background concentrations. Al was found at higher concentrations in the southernmost areas of Portugal, but this pattern might be related to external soil contamination on feathers. Overall, this study indicates that, among all elements studied, Hg seems to be the most important contaminant for Bonelli's eagles in southern Portugal, likely due to the power plant emissions and biomagnification of Hg in terrestrial food webs.

State of knowledge on current exposure, fate and potential health effects of contaminants in polar bears from the circumpolar Arctic.

The polar bear (Ursus maritimus) is among the Arctic species exposed to the highest concentrations of long-range transported bioaccumulative contaminants, such as halogenated organic compounds and mercury. Contaminant exposure is considered to be one of the largest threats to polar bears after the loss of their Arctic sea ice habitat due to climate change. The aim of this review is to provide a comprehensive summary of current exposure, fate, and potential health effects of contaminants in polar bears from the circumpolar Arctic required by the Circumpolar Action Plan for polar bear conservation. Overall results suggest that legacy persistent organic pollutants (POPs) including polychlorinated biphenyls, chlordanes and perfluorooctane sulfonic acid (PFOS), followed by other perfluoroalkyl compounds (e.g. carboxylic acids, PFCAs) and brominated flame retardants, are still the main compounds in polar bears. Concentrations of several legacy POPs that have been banned for decades in most parts of the world have generally declined in polar bears. Current spatial trends of contaminants vary widely between compounds and recent studies suggest increased concentrations of both POPs and PFCAs in certain subpopulations. Correlative field studies, supported by in vitro studies, suggest that contaminant exposure disrupts circulating levels of thyroid hormones and lipid metabolism, and alters neurochemistry in polar bears. Additionally, field and in vitro studies and risk assessments indicate the potential for adverse impacts to polar bear immune functions from exposure to certain contaminants.

Developmental Toxicity of Perfluorooctanesulfonate (PFOS) and Its Chlorinated Polyfluoroalkyl Ether Sulfonate Alternative F-53B in the Domestic Chicken.

The chlorinated polyfluoroalkyl ether sulfonate F-53B is used as a mist suppressant in the Chinese electroplating industry. Because of the regulations on perfluorooctanesulfonate (PFOS), its use is expected to increase. Until now, F-53B toxicity data have been scarce and are, to our knowledge, lacking for birds. This study therefore investigated the effects of PFOS and F-53B, separately and as mixtures, on the development of the chicken ( Gallus gallus domesticus). Compounds were injected in ovo, before incubation, at 150 and 1500 ng/g egg. At embryonic day 20, a significantly lower heart rate was observed in all treated groups compared to the control group and hatchlings exposed to the high dose of F-53B had a significantly enlarged liver (8%). Embryonic survival was not affected and no significant effects on hatchling body mass or oxidative stress parameters were found. Our results suggest that these compounds likely have different toxicity thresholds for the investigated endpoints, and/or different modes of action. This study thereby underlines the potential developmental toxicity of PFOS and F-53B at environmentally relevant concentrations. Assessment of PFOS alternatives should therefore continue, preferably prior to their large scale use, as they should be ensured to be less harmful than PFOS itself.

Anthropogenic impact on marine ecosystem health: A comparative multi-proxy investigation of recent sediments in coastal waters.

Hazardous substances entering the sea, and ultimately deposited in bottom sediments, pose a growing threat to marine ecosystems. The present study characterized two coastal areas exposed to significant anthropogenic impact - Gulf of Gdansk (Poland), and Oslofjord/Drammensfjord (Norway) - by conducting a multi-proxy investigation of recent sediments, and comparing the results in light of different available thresholds for selected contaminants. Sediment samples were analyzed for benzo(a)pyrene (B(a)P) and other polycyclic aromatic hydrocarbons (PAHs), nonylphenols (NPs), organotin compounds (OTs), toxic metals (Cd, Hg, Pb), as well as mutagenic, genotoxic and endocrine-disrupting activities (in CALUX bioassays). In general, a declining trend in the deposition of contaminants was observed. Sediments from both basins were not highly contaminated with PAHs, NPs and metals, while OT levels may still give rise to concern in the Norwegian fjords. The results suggest that the contamination of sediments depends also on water/sediment conditions in a given region.

In ovo transformation of two emerging flame retardants in Japanese quail (Coturnix japonica).

Tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) and Dechlorane Plus (DP) are two chlorinated, alternative flame retardants that have been found in wild birds and bird eggs. Little is known about the fate and effect of these compounds in birds, especially during the vulnerable stages of embryonic development. To investigate the ability of birds to biotransform these compounds, an in ovo exposure experiment with Japanese quail eggs was performed. Quail eggs were injected in the yolk sac with 1000ng/g egg of TDCIPP (2.3 nmol/g ww), DP (1.5 nmol/g ww) or a mixture of both and were then incubated at 37.5°C for 17 days. To get a time-integrated understanding of the in ovo transformation of the compounds, one egg per treatment was removed from the incubator every day and analyzed for TDCIPP and its metabolite bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) and/or for DP. By the end of the incubation period, TDCIPP was completely metabolized, while simultaneously BDCIPP was formed. The conversion of the parent compound into the metabolite did not occur proportionally and the concentration of BDCIPP showed a tendency to decrease when TDCIPP became depleted, both indicating that BDCIPP was further transformed into compounds not targeted for analysis. Further untargeted investigations did not show the presence of other metabolites, possibly due to the volatility of the metabolites. On the other hand, the DP concentration did not decrease during egg incubation. This study indicates that within the incubation period, avian embryos are able to biotransform TDCIPP, but not DP.

Steroid hormones and persistent organic pollutants in plasma from North-eastern Atlantic pilot whales.

Persistent organic pollutants (POPs) are known to have endocrine disruptive effects, interfering with endogenous steroid hormones. The present study examined nine steroid hormones and their relationships with the concentrations of selected POPs in pilot whales (Globicephala melas) from the Faroe Islands, NE Atlantic. The different steroids were detected in 15 to all of the 26 individuals. High concentrations of progesterone (83.3-211.7pmol/g) and pregnenolone (PRE; 4.68-5.69pmol/g) were found in three adult females indicating that they were pregnant or ovulating. High androgen concentrations in two of the males reflected that one was adult and that one (possibly) had reached puberty. In males a significant positive and strong correlation between body length and testosterone (TS) levels was identified. Furthermore, positive and significant correlations were found between 4-OH-CB107/4'-OH-CB108 and 17ß-estradiol in males. In adult females significant positive correlations were identified between PRE and CB149 and t-nonachlor, between estrone and CB138, -149, -187 and p,p'-DDE, between androstenedione and CB187, and between TS and CB-99 and -153. Although relationships between the POPs and the steroid hormones reported herein are not evidence of cause-effect relationships, the positive correlations between steroids and POPs, particularly in females, suggest that POPs may have some endocrine disrupting effects on the steroid homeostasis in this species.

Acute hydrogen peroxide (H2O2) exposure does not cause oxidative stress in late-copepodite stage of Calanus finmarchicus.

Use of hydrogen peroxide (H2O2) for removal of salmon lice in the aquaculture industry has created concern that non-target organisms might be affected during treatment scenarios. The aim of the present study was to examine the potential for H2O2 to produce oxidative stress and reduce survival in one of the most abundant zooplankton species in Norwegian coastal areas, the copepod Calanus finmarchicus. Copepods were subjected to two 96-hr tests: (1) acute toxicity test where mortality was determined and (2) treated copepods were exposed to concentrations below the No Observed Effect Concentration (0.75 mg/L) H2O2 and analyzed for antioxidant enzyme activities, as well as levels of glutathione (GSH) and malondialdehyde (MDA). Compared to available and comparable LC50 values from the literature, our results suggest that C. finmarchicus is highly sensitive to H2O2. However, 96-hr exposure of C. finmarchicus to 0.75 mg H2O2/L did not significantly affect the antioxidant systems even though the concentration is just below the level where mortality is expected. Data suggest that aqueous H2O2 exposure did not cause cellular accumulation with associated oxidative stress, but rather produced acute effects on copepod surface (carapace). Further investigation is required to ensure that aqueous exposure during H2O2 treatment in salmon fish farms does not exert adverse effects on local non-target crustacean species and populations. In particular, studies on copepod developmental stages with a more permeable carapace are warranted.