SMRU > Research > Toxicology
Marine mammals are top predators (that is, they are at the top of the food chain) and as such they are often ‘sinks’ for many different classes of marine environmental pollutants. These pollutants often biomagnify in concentration as they move up through the food chain, so that the levels found in marine mammal tissues are many orders of magnitude above the concentration measured in the water or plankton. In addition, many classes of pollutants are toxic. Adverse effects on many different physiological systems including reproduction, immune function and thyroid homeostasis have been found in seals and cetaceans.
Studies on toxic contaminants have included determining both the levels of contaminants in marine mammal tissues and their effects on different physiological functions. This has encompassed carrying out field studies, collecting samples from both live captured and dead stranded animals and in vivo correlative studies relating observed tissue levels with various physiological response measures. In addition we have conducted in vitro experimental approaches using marine mammal cells in culture and exposing them to different contaminant types and concentrations.
Of particular interest are the classical compounds such as the polychlorinated biphenyls, DDT and more recently the polybrominated diphenyl ethers that are found at sometimes very high concentrations in the milk and blubber.
Paddy Pomeroy and others have studied the dynamics of contaminants during lactation in female grey seals and their transfer from mother to pup in milk. The relationship between pollutant transfer and some important vitamin groups has been outlined. The role of different fatty acids in selective pollutant transfer is being investigated.
Ailsa Hall and her collaborators have carried out research focussing on the physiological effects of exposure, particularly on thyroid homeostasis and on immune function in grey and harbour seals in the UK. Cooperating with Bernie McConnell, she has modelled the potential impacts of pollutants at the population level, using bottlenose dolphins as an example. This risk assessment work is now being advanced in collaboration with the International Whaling Commission under its Pollution 2000+ initiative.