Even H. Jørgensen

Exposure and effects assessment of persistent organohalogen contaminants in arctic wildlife and fish

Persistent organic pollutants (POPs) encompass an array of anthropogenic organic and elemental substances and their degradation and metabolic byproducts that have been found in the tissues of exposed animals, especially POPs categorized as organohalogen contaminants (OHCs). OHCs have been of concern in the circumpolar arctic for decades. For example, as a consequence of bioaccumulation and in some cases biomagnification of legacy (e.g., chlorinated PCBs, DDTs and CHLs) and emerging (e.g., brominated flame retardants (BFRs) and in particular polybrominated diphenyl ethers (PBDEs) and perfluorinated compounds (PFCs) including perfluorooctane sulfonate (PFOS) and perfluorooctanic acid (PFOA) found in Arctic biota and humans. Of high concern are the potential biological effects of these contaminants in exposed Arctic wildlife and fish. As concluded in the last review in 2004 for the Arctic Monitoring and Assessment Program (AMAP) on the effects of POPs in Arctic wildlife, prior to 1997, biological effects data were minimal and insufficient at any level of biological organization. The present review summarizes recent studies on biological effects in relation to OHC exposure, and attempts to assess known tissue/body compartment concentration data in the context of possible threshold levels of effects to evaluate the risks. This review concentrates mainly on post-2002, new OHC effects data in Arctic wildlife and fish, and is largely based on recently available effects data for populations of several top trophic level species, including seabirds (e.g., glaucous gull (Larus hyperboreus)), polar bears (Ursus maritimus), polar (Arctic) fox (Vulpes lagopus), and Arctic charr (Salvelinus alpinus), as well as semi-captive studies on sled dogs (Canis familiaris). Regardless, there remains a dearth of data on true contaminant exposure, cause-effect relationships with respect to these contaminant exposures in Arctic wildlife and fish. Indications of exposure effects are largely based on correlations between biomarker endpoints (e.g., biochemical processes related to the immune and endocrine system, pathological changes in tissues and reproduction and development) and tissue residue levels of OHCs (e.g., PCBs, DDTs, CHLs, PBDEs and in a few cases perfluorinated carboxylic acids (PFCAs) and perfluorinated sulfonates (PFSAs)). Some exceptions include semi-field studies on comparative contaminant effects of control and exposed cohorts of captive Greenland sled dogs, and performance studies mimicking environmentally relevant PCB concentrations in Arctic charr. Recent tissue concentrations in several arctic marine mammal species and populations exceed a general threshold level of concern of 1 part-per-million (ppm), but a clear evidence of a POP/OHC-related stress in these populations remains to be confirmed. There remains minimal evidence that OHCs are having widespread effects on the health of Arctic organisms, with the possible exception of East Greenland and Svalbard polar bears and Svalbard glaucous gulls. However, the true (if any real) effects of POPs in Arctic wildlife have to be put into the context of other environmental, ecological and physiological stressors (both anthropogenic and natural) that render an overall complex picture. For instance, seasonal changes in food intake and corresponding cycles of fattening and emaciation seen in Arctic animals can modify contaminant tissue distribution and toxicokinetics (contaminant deposition, metabolism and depuration). Also, other factors, including impact of climate change (seasonal ice and temperature changes, and connection to food web changes, nutrition, etc. in exposed biota), disease, species invasion and the connection to disease resistance will impact toxicant exposure. Overall, further research and better understanding of POP/OHC impact on animal performance in Arctic biota are recommended. Regardless, it could be argued that Arctic wildlife and fish at the highest potential risk of POP/OHC exposure and mediated effects are East Greenland, Svalbard and (West and South) Hudson Bay polar bears, Alaskan and Northern Norway killer whales, several species of gulls and other seabirds from the Svalbard area, Northern Norway, East Greenland, the Kara Sea and/or the Canadian central high Arctic, East Greenland ringed seal and a few populations of Arctic charr and Greenland shark.

Effects of stocking density on food intake, growth performance and oxygen consumption in Arctic charr (Salvelinus alpinus)

Abstract Food intake, growth rates, and rates of oxygen consumption were measured in Arctic charr (Salvelinus alpinus), stocked at low (15 kg·m−3), medium (60 kg·m−3) and high (120 kg·m−3) densities. Growth rates were similar for fish stocked at the medium and high densities, but were markedly depressed at the lowest stocking density. Differences in growth were probably the result of similar differences in food intake. Low levels of food intake were probably also the prime reason for the low oxygen consumption rates recorded in the groups of fish stocked at low density. Stocking density affected the behaviour of the fish, and schooling behaviour was observed in the groups subjected to the medium and high stocking density. No significant correlations were found between initial body size, food intake and growth rates in the groups of fish held at any stocking density. Consequently, social constraints due to the formation of dominance hierarchies may not have been the prime reason for the appetite and growth reduction seen in groups stocked at low density.

Leptin and ghrelin in anadromous Arctic charr: Cloning and change in expressions during a seasonal feeding cycle

Anadromous (sea-migrating) Arctic charr (Salvelinus alpinus) display pronounced seasonal variations in food intake and growth and is an interesting model for studying mechanisms of appetite regulation. In this study cDNAs encoding for ghrelin (GHRL) and leptin (LEP) in Arctic charr were cloned, after which stomach GHRL and liver LEP mRNA expressions were examined by qPCR during a seasonal feeding cycle of semi-wild anadromous Arctic charr. The fish were captured as they returned from summer feeding in seawater and transferred to an indoor tank where they were fed in excess until October the year after. Growth rate was low in late winter, increased in late spring and reached a peak during summer, and then declined during autumn, when the fish became sexually mature. The changes in growth rate were associated with corresponding changes in the proportion of fish that had been eating at each sampling date, and whole body lipid status. Stomach GHRL mRNA expression was high in late winter, decreased to a nadir in mid-summer and increased again to a high level in early autumn. Liver LEP mRNA remained low during winter, spring and early summer, after which there was a gradual, 7-fold increase until October. The seasonal changes in ghrelin and leptin support a role of these hormones in the long-term regulation of energy homeostasis in the anadromous Arctic charr. It cannot be excluded, however, that the increase in liver leptin expression during autumn is related to sexual maturation.

The effects of exercise on growth, food utilisation and osmoregulatory capacity of juvenile Atlantic salmon, Salmo salar

Abstract Specific growth rate (SGR), food intake (FI) and frequency of fin damage were recorded in juvenile Atlantic salmon ( Salmo salar ), held for 63 days in standing water (controls) and at water currents corresponding to initial swimming speeds of 1.0, 1.5 and 2.0 BI·s −1 , respectively. SGRs were significantly higher in all exercised groups than in the controls, with a maximum in the group swimming at 1.5 BI·s −1 . FI increased slightly with increasing swimming speed, and there was a more even distribution of food as swimming speed increased. The reduced inter-individual variation in FI was reflected in greater homogeneity of growth in the exercised groups than in controls reared in standing water. As compared to the controls, which had a growth/food intake ratio of 1.31, food utilisation was significantly higher in the fish swimming at 1.0 BI·s −1 (with a ratio of 1.56), but food utilisation of the groups swimming at the highest speeds did not differ significantly from the controls. Analysis of body composition revealed that the body water content was higher, and energy content lower in the salmon swimming at the highest speed than in the controls. Exercise affected the behaviour of the fish, appeared to result in reduced levels of agonistic activity, and the rate of fin wound healing seemed to increase with increasing swimming speed. Exercise did not, however, lead to any improvement of the osmoregulatory capacity of fish undergoing parr-smolt transformation.

Lipid dynamics in anadromous Arctic charr, Salvelinus alpinus (L.): seasonal variations in lipid storage depots and lipid class composition

Changes in lipid class composition of tissues of anadromous Arctic charr, Salvelinus alpinus, were studied in relation to seasonal patterns of lipid deposition and lipid mobilisation. Charr of a north Norwegian population were collected in late May when fish were migrating towards the sea, and in mid-July when the fish re-entered fresh water. Some maturing fish captured in mid-July were held in captivity until late September to assess lipid dynamics associated with maturation. The carcass (head, fins, skeleton and skin) accounted for approx. 50% of the total body lipid content when the fish re-entered fresh water from the sea. Triacylglycerols (TAG) comprised 75-80% of the carcass lipid in ascending charr, confirming that the carcass is a major lipid depot. The skeletal muscle also represented a major lipid store: muscle of ascending charr contained 35-40% of the body lipids, with TAG being dominant (approx. 75% of muscle lipid). The gut (gastrointestinal tract and visceral lipid) and liver of ascending charr each held only 4-5%; of the body lipid, TAG being the dominant lipid class in both of these depots (Gut TAG: 60-65%; Liver TAG: 50-55%). Body lipid decreased 30-40% during maturation: lipids were depleted from all depots, but mobilisation of from the carcass and muscle was quantitatively the most important. In mature females, the ovaries held almost 25% of the body lipid, with the proportion of TAG exceeding that of polar lipids (PL)(TAG: 62%; PL 12.4%). In the mature males, the testes accounted for less than 3% of the total lipids. TAG tended to dominate the testis lipids (TAG: 29.5%), but there were also quite high proportions of free fatty acids, cholesterol and polar lipids (FFA: 23.5%; C: 15%; PL 9.7%). Females lost approx. 80% of their body lipid during spawning and overwintering, the majority of this being TAG. Males also lost large amounts of TAG during the winter, but in contrast to the females lipid depletion amounted to only 50-55% of that present at the time of ascent into fresh water.

Influence of nutritional status on biomarker responses to PCB in the Arctic charr (Salvelinus alpinus)

Transport of pollutants from industrial areas has resulted in Arctic environments facing increasing levels of organic pollution. Thus, a need for sensitive and reliable biomarkers that can be used to assess the risk associated with exposure to xenobiotics in these areas has arisen. In high latitudes, temporal variations in the nutritional status of animals can be considerable, and these variations may influence toxicokinetic processes and biomarker responses. In the present study, different biomarker (cytochrome P450 (CYP1A), pre- and post-stress plasma cortisol concentrations and fin erosion) responses were recorded in groups of PCB-exposed (given a single oral dosage of 1 μg Aroclor 1260 (g body weight)−1) and unexposed Arctic charr. Following treatment (PCB administration), fish were held for 141 days under either a restricted feeding regime or without food. PCB exposure did not effect either growth or organ lipid concentrations. Food deprivation resulted in a marked reduction in lipid concentration in muscle and kidney, and a 3- and 11-fold increase in the PCB concentrations in the kidney and liver of the PCB-exposed fish. Food deprivation did not appear to influence hepatic EROD activities and CYP1A content, but the elevated PCB concentration in the liver of the fasted, PCB-exposed fish seemed to result in a dose-related increase in EROD activity and CYP1A content. Plasma cortisol concentrations of unstressed fish were below the detection limit of 3.6 ng ml−1. Post-stress plasma cortisol concentrations were low in the food deprived fish, irrespective of PCB exposure. The highest post-stress plasma cortisol concentrations were recorded in PCB-exposed, fed fish. The fish that were held without food had the lowest incidence of fin erosion, whereas the combination of food deprivation and PCB exposure resulted in the highest prevalence of fin erosion. Thus, nutritional status (i.e. long term food deprivation) influenced both tissue concentrations of PCB, and biomarker responses. This must be borne in mind if biomarkers are to be used in environmental monitoring programmes.

Feeding behaviour and effect of feeding regime on growth of Atlantic salmon, Salmo salar

Abstract Feeding rates (food intake per hour) during night and day, feeding modes under different light conditions and the effects of the length of the daily feeding period on growth have been studied in Atlantic salmon, Salmo salar . In autumn (12L:12D), winter (4L:20D) and spring (14L:10D), feeding rates were 3.1 to 7.5 times higher during daylight hours than at night. All food was taken in the water column during light conditions, but juvenile salmon did take food lying on the tank bottom during the hours of darkness. Different feeding regimes (food offered 3 h per day, during the light period of the day only, and continuously) appeared to have no effect on growth and parr-smolt transformation.

Fasting modifies Aroclor 1254 impact on plasma cortisol, glucose and lactate responses to a handling disturbance in Arctic charr

Integrated effects of polychlorinated biphenyl (PCB) and nutritional status on responses to handling disturbance were investigated in the Arctic charr (Salvelinus alpinus). The fish were orally contaminated with Aroclor 1254 and held either with or without food for 5 months before they were subjected to a 10-min handling disturbance. Food-deprived fish were given 0, 1, 10 or 100 mg PCB kg(-1) and the fed fish 0 or 100 mg PCB kg(-1). Plasma cortisol, glucose and lactate levels were measured at 0 (pre-handling), 1, 3, 6 and 23 h after the handling disturbance. Food-deprived control fish had elevated plasma cortisol levels compared with fed fish before handling. These basal cortisol levels were suppressed by PCB in food-deprived fish, and elevated by PCB in fed fish. The immediate cortisol and glucose responses to handling disturbance were suppressed by PCB in a dose-dependent way in food-deprived fish. Although these responses were also lowered by PCB in the fed fish, the effect was much less pronounced than in food-deprived fish. There were only minor effects on plasma lactate responses. Our findings suggest that the stress responses of the Arctic charr are compromised by PCB and that the long-term fasting, typical of high-latitude fish, makes these species particularly sensitive to organochlorines such as PCB.

The application of X‐radiography in feeding and growth studies with fish: A summary of experiments conducted on arctic charr

Abstract The X‐radiographic method first described by Talbot and Higgins (1983) can, with suitable modifications and in combination with other simple techniques, have a wide range of applications in feeding and growth studies with fish. The method can be used for the accurate determination of feed intake, something that is required for the construction of feed tables for farmed fish. The method also may be used in studies designed for the investigation of feeding behavior and modes of feeding. The most useful application may, however, be related to the study of feed‐growth relationships because the method enables the monitoring of feeding and growth performances of individual fish within groups. The application of the method to the study of feed‐growth relationships is described using the effects of different levels of sustained exercise on these relationships as an example. The data show that exposure of fish to moderate water currents for prolonged periods leads to both higher rates of weight gain and i...

Feeding modes in Arctic charr, Salvelinus alpinus L.: the importance of bottom feeding for the maintenance of growth.

Abstract Results of short-term experiments revealed that Artic charr, Salvelinus alpinus , may take a substantial proportion of their food from the bottom, both under light and dark conditions. Longer term studies showed that charr required access to food on the bottom in order to maintain high rates of feed intake and growth. Fish appeared unable to adapt to taking food exclusively in the water column since food intake of fish prevented from feeding on the bottom remained low throughout the 17-week experiment.