Researchers at Cal State have just released the results of their studies on contaminants found in the bodies of juvenile sharks:
As Dr Chris Lowe mentions in our film, chemical contaminants in the food chain accumulate in the blubber of marine mammals, are eaten by adult female sharks, and then passed on to their pups before they are born. But they are not seeing the effects of disease and sterility that are affecting sea mammals in the sharks. Whilst it is a popular myth that sharks “don’t get cancer”, their immune system has evolved separately to that of mammals, and this kind of resilience to toxins that have serious effects on mammals, could lead to a whole new area of vitally important research. It’s another reason the shark survival is of paramount importance:
Left: Dr Chris Lowe, Cal State and Monterrey Bay Aquarium researchers net a juvenile White Shark; toxins passed maternally appear not to affect it. Photo Steve McNicholas
Evidence of Maternal Offloading of Organic Contaminants in White Sharks (Carcharodon carcharias)
Christopher G. Mull, Kady Lyons, Mary E. Blasius, Chuck Winkler, John B. O’Sullivan, Christopher G. Lowe
Organic contaminants were measured in young of the year (YOY) white sharks (Carcharodon carcharias) incidentally caught in southern California between 2005 and 2012 (n = 20) and were found to be unexpectedly high considering the young age and dietary preferences of young white sharks, suggesting these levels may be due to exposure in utero. To assess the potential contributions of dietary exposure to the observed levels, a five-parameter bioaccumulation model was used to estimate the total loads a newborn shark would potentially accumulate in one year from consuming contaminated prey from southern California. Maximum simulated dietary accumulation of DDTs and PCBs were 25.1 and 4.73 µg/g wet weight (ww) liver, respectively. Observed ΣDDT and ΣPCB concentrations (95±91 µg/g and 16±10 µg/g ww, respectively) in a majority of YOY sharks were substantially higher than the model predictions suggesting an additional source of contaminant exposure beyond foraging. Maternal offloading of organic contaminants during reproduction has been noted in other apex predators, but this is the first evidence of transfer in a matrotrophic shark. While there are signs of white shark population recovery in the eastern Pacific, the long-term physiological and population level consequences of biomagnification and maternal offloading of environmental contaminants in white sharks is unclear.