Náttúra og náttúrutilfeingi
Effects of POPs in pilot whale
Umhvørvisstovan og NTNU
Bjørn Munro Jenssen, vegleiðari o.fl.
Stuðul úr Granskingargrunninum:
Monitoring of contaminant exposure in long-finned pilot whales (Globicephala melas) has shown high levels of persistent organic pollutants, POPs, like PCB, DDT, flame retardants PBDE and heavy metals such as mercury and cadmium. The high levels of contaminants in the tissues of pilot whales are raising concern for the health of the whales, because these contaminants are known to interfere with several biological systems with serious effects on the individual and populations as a result. Similar levels of contaminants have been linked to negative impact on reproduction success in other cetacean species.
POPs can affect the levels of hormones, vitamins and enzymes. Previous studies of marine mammals have shown negative correlations between POP concentrations and thyroid hormone and vitamin A concentrations along with positive correlation between POP exposure and the induction of enzyme systems involved in the metabolism of POPs. Thyroid hormones control metabolism and growth and are essential for normal reproduction. Retinoids are essential for vision, growth, reproduction, immune function and cellular division and differentation in mammals. The decreased levels of these compounds occuring from POP are thus expected to cause impairment of these functions in mammals.
The aims of this study is to investigate the effects of POPs on pilot whales sampled in connection with the traditional whale hunt at the Faroe Islands. This will be done by analysing the pilot whales for POPs and mercury concentration (in liver, blubber, blood, kidney and muscle) and several biomarkers of contaminant exposure, including thyroid hormones (TT4, TT3, FT4 and FT3 in plasma), steroids (incl. estrogens and androgens in plasma), Vitamin A (retinoids in liver, blubber and plasma), Cytocrome P450 enzymes related to biotransformation of xenobiotics and steroids, and other molecular responses related to contaminant exposure including gene expression of hormone receptors (androgen-, estrogen- and thyriod receptors). These analyses are integral components of overt physiology, reproduction and health condition of these whales that are potentially under contaminant stress with possible deleterious consequences for longterm survival and recruitment.
Studies of effects of POPs on cetaceans have been limited partly due to difficulties in getting samples because many whale species are protected. Analyses of cetaceans are often made on stranded animals or by non-lethal sampling of free-ranging or captive animals. These samplings do however have some restrictions for use in effect studies as such analyses require fresh samples from animals not heavily stressed by hunger and/or disease, and analyses of internal organs are not possible with the non-lethal sampling methods. The traditional pilot whale hunt on the Faroe Islands provides a good opportunity to get such fresh whales samples, including internal organs, and to analyse the effects of POPs and metals on odontocete cetaceans.
The results from the analyses will be an important contribution to the knowledge of the impacts of contaminant exposure on cetaceans.
Final Pilot whales (Globicephala melas) in the Northeastern part of the Atlantic Ocean have high body concentrations of persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), organochlorinated pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs). These compounds and their biological biotransformation products, i.e. metabolites, have been linked to serious health effects in mammals, including effects on the reproductive system, due to disruption of their endocrine systems. The aim of this study was to analyse levels of POPs and their metabolites in pilot whales from Faroese waters and to investigate the possible effects of the POP exposure on steroid hormones, thyroid hormones, and vitamin A, E and D, which have been suggested as sensitive biomarkers for endocrine disruptive effects. In addition, the ability of the whales to biotransform the POPs was investigated. The possible effects of the POPs on the biomarkers were studied by analysing correlative relationships between the POP concentrations and the biomarkers, and furthermore, the POP concentrations were compared to toxic reference values (TRVs) which have been suggested for toxic effects in marine mammals.
The analyses confirmed that the pilot whales from the Faroe Islands had high concentrations of POPs in their tissues, exceeding some TRVs which have been suggested for toxic effects in marine mammals, but low concentrations of metabolites. In addition low activities of phase I and phase II enzymes were measured, indicating that the pilot whales have low ability to biotransform POPs, although they expressed enzymes of the CYP1A, 2B and 3A families. The biomarkers for endocrine disrupting effects did generally not show high correlative relationships with the POP concentrations, but differed with age and sex of the whales, indicating that that these are important confounding factors. Nevertheless, some correlations were found between single POPs and hormones and vitamins, suggesting that POPs may have some effect on the vitamin and hormone homeostasis in pilot whales.
From the study it could be concluded, that although the pilot whales from the Faroe Islands were exposed to relatively high concentrations of POPs, and the concentrations exceeded some of the toxic reference levels suggested for effects on marine mammals, the POPs did not seem to have clear overall negative effects on the analysed biomarkers. This indicates that the POPs in the Faroe Island population of pilot whales may be below threshold levels for negative effects on steroid and thyroid hormones and vitamin A levels. This could possibly be related to the apparent low biotransformation of POPs in pilot whales and thus their low concentrations of metabolites, such as OH-PCBs and OH-PBDE, which often have been linked to the endocrine disrupting effects of POPs.
Hoydal, K.S., Letcher, R.J., Blair, D.A.D., Dam, M., Lockyer, C., Jenssen, B.M., 2015. Legacy and emerging organic pollutants in liver and plasma of long-finned pilot whales (Globicephala melas) from waters surrounding the Faroe Islands. Sci. Total Environ. 520, 270–285. doi:10.1016/j.scitotenv.2015.03.056
Hoydal, K.S., Ciesielski, T.M., Borrell, A., Wasik, A., Letcher, R.J., Dam, M., Jenssen, B.M., 2016. Relationships between concentrations of selected organohalogen contaminants and thyroid hormones and vitamins A, E and D in Faroese pilot whales. Environ. Res. 148, 386–400. doi:10.1016/j.envres.2016.04.012
Hoydal, K.S., Styrishave, B., Ciesielski, T.M., Letcher, R.J., Dam, M., Jenssen, B.M., 2017. Steroid Hormones and Persistent Organic Pollutants in plasma from North-eastern Atlantic Pilot whales. Environ. Res. 159, 613–621. doi:10.1016/j.envres.2017.09.003
Hoydal, K.S., Obuchowska, M., Bączek, T., Jenssen, B.M. and Ciesielski, T. Effects of POPs on vitamin A and E homeostasis in pilot whales (Globicephala melas). VIII International Conference «Marine Mammals of Holarctic», St. Petersburg, 22. – 27. September 2014.
Hoydal, K.S., Arukwe, A., Ciesielski, T., Letcher, R.J., Dam, M and Jenssen, B.M. Effects of persistent organic pollutants on vitamin A levels in Faroese pilot whales. SETAC Europe 26th Annual Meeting, Nantes, France, 22-26 May 2016.
Hoydal, K.S., 2017. Levels and endocrine disrupting effects of legacy POPs and their metabolites in long-finned pilot whales of the Faroe Islands. PhD thesis, Department of Biology, Faculty of Natural Sciences, Norwegian University of Science and Technology.
Other results, such as unpublished articles, patents, computer systems, original models and new procedures
Hoydal, K.S., Jenssen, B.M., Letcher, R.J., Dam, M., Arukwe, A., Hepatic Phase I and II Biotransformation Responses and Contaminant Exposure in Long-Finned Pilot Whale from the Northeastern Atlantic. Submitted.
Hoydal, K.S., Jenssen, B.M., Ciesielski, T.M., Letcher, R.J., Dam, M., Arukwe, A., Changes in CYP26 expression and vitamin A levels in relation to contaminant levels in Faroese pilot whales. Manuscript.