Changes in trace elements during lactation in a marine top predator, the grey seal

in Aquatic Toxicology (2013), 126

Lactation in pinnipeds represents the most significant cost to mothers during the reproductive cycle. Dynamics of trace elements and their mobilization associated with energy reserves during such an ... [more ▼]

Lactation in pinnipeds represents the most significant cost to mothers during the reproductive cycle. Dynamics of trace elements and their mobilization associated with energy reserves during such an intense physiological process remains poorly understood in marine mammals. The changes in tissue concentrations of 11 elements (Ca, Cd, Cr, Cu, Fe, Hg, Ni, Pb, Se, V, and Zn) were investigated in a longitudinal study during the lactation period and during the post-weaning fast period. Blood, milk, blubber, and hair samples were collected sequentially from 21 mother-pup pairs of grey seals (Halichoerus grypus) from the Isle of May in Scotland. Maternal transfer through the milk was observed for all trace elements, except for Cd. As an indicator of the placental transfer, levels in pup lanugo (natal coat) revealed also the existence of maternal transfer and accumulation of all assayed trace elements during the foetal development. The placental and mammary barriers against non-essential metal transfer to offspring appear to be absent or weak in grey seals. Examining the contamination levels showed that this grey seal population seems more highly exposed to Pb than other phocid populations (2.2 mg/kg dw of grey seal hair). In contrast, blood and hair levels reflected a lower Hg exposure in grey seals from the Isle of May than in harbour seals from the southeastern North Sea. This study also showed that trace element concentrations in blood and blubber could change rapidly over the lactation period. Such physiological processes must be considered carefully during biomonitoring of trace elements, and potential impacts that rapid fluctuations in concentrations can exert on seal health should be further investigated. [less ▲]

How are trace elements mobilized during the post-weaning fast in northern elephant seals?

in Environmental Toxicology & Chemistry (2012), 31(10), 2354-2365

Northern elephant seal (Mirounga angustirostris) pups undergo a substantial intertissue reorganization of protein, minerals, and other cellular components during their postweaning development, which might ... [more ▼]

Northern elephant seal (Mirounga angustirostris) pups undergo a substantial intertissue reorganization of protein, minerals, and other cellular components during their postweaning development, which might entail the mobilization of associated contaminants. The authors investigated the changes in concentrations of 11 elements (Ca, Cd, Cr, Cu, Fe, Hg, Ni, Pb, Se, V, and Zn) in a longitudinal study on 22 northern elephant seal pups during the postweaning fast. Slight changes in most element concentrations were observed in blood throughout the fast. Circulating levels of Hg, Se, and Cu appeared less altered during the postweaning fast than during suckling (previously measured). Despite the considerable fat utilization, element concentrations in blubber remained stable throughout the fast (except Fe), which suggests that elements are mobilized from blubber as efficiently as lipids. As indicators of the placental transfer, concentrations in lanugo hair revealed the existence of maternal transfer and accumulation of all assayed trace elements during fetal development. In addition, the new pelage, rapidly produced after weaning, appeared to be an important elimination route for toxic metals like Hg, Cd, and Pb. The high mineral content detected in pup hair suggests that this species would be more exposed to trace elements than other phocids (except Cd and Pb). This statement needs nevertheless further monitoring and toxicological studies to determine better the exposition to trace elements and its potential impact on the northern elephant seal’s health. [less ▲]

Fatty acids and stable isotopes in fish and harbour porpoises (Phocoena phocoena) from the North Sea: further insights in their trophic relationships

Poster (2007)

Recent observations revealed an increased abundance of the harbour porpoise in the southern part of the North Sea. Concomitant to sightings of living individuals, the number of stranded porpoises ... [more ▼]

Recent observations revealed an increased abundance of the harbour porpoise in the southern part of the North Sea. Concomitant to sightings of living individuals, the number of stranded porpoises displaying lesions linked to fishing nets has also increased this last decade. The increased abundance of porpoises together with the increase in numbers of bycaught animals raised the question of possible competition between porpoises and fishermen in the North Sea. Therefore, a detailed view on harbour porpoise trophic ecology in this region is crucial for their conservation. Stomachs of the washed ashore porpoises were often empty and provided limited information on their recent diet. Another way of looking into the diet of marine mammals is the analysis of blubber. Stable isotopes ratio (d13C and d15N, SI) and fatty acid composition (20 fatty acids, FA) were analyzed in muscle and blubber of 10 freshly stranded harbour porpoises and in 60 potential prey fish from 10 species collected in the North Sea. The SI ratio and FA composition of these fish enabled a clear classification in different trophic levels and different trophic niches. The FA composition was very similar between harbour porpoise blubber and demersal fish, underlining a preferential predation on that resource for the porpoises investigated. A bias might exist for the porpoises: most of the animals were juveniles, and washed ashore during spring. Porpoises might display other feeding habits in other life stages, other periods of the year. These preliminary results however indicate the enhanced accuracy of crossing these biomarker approaches. [less ▲]