J'ai déjà souligné que les moules zébrées contribuent à la contamination de plomb des poissons qui les mangent dans mon entrée "Moules zébrées dans le Lac Érié" http://lesamisdurichelieu.blogspot.com/2010/07/moules-zebrees-dans-le-lac-erie.html.
D'autres scientifiques découvrent que les moules font d'autres dommages. Il semblerait que les endroits fortement contaminés aux BPC connaissent le même problème. Bien que les biphényles polychlorés sont interdits depuis les années 1970, beacoup de cours d'eau en ont dans leurs sédiments à des concentrations variées. Et là aussi, les moules zébrées, qui filtrent l'eau dans le fond des rivières et des lacs contaminés, absorbent les BPC et les réintroduisent dans la chaîne alimentaire, car beaucoup d'espèces de poissons se nourissent à leur tour de ces moules.
Le BPC a cette charactéristique de s'accumuler dans la graisse des animaux, d'où l'importance de manger les petits poissons (qui ont eu moins le temps d'accumuler les BPC dans leur corps) et de ne pas manger les parties grasses des poissons que l'on pêche dans les cours d'eau les plus pollués.
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"Invasive Species and Toxic Chemicals
There are these chemicals called PCBs or polychlorinated biphenyls. They were found to be toxic decades ago. The Environmental Protection Agency considers them to be probable human carcinogens. They were banned in the 1970s, but they’re still all around us. They’re buried in the sediment at the bottom of some of our rivers and lakes. Now researchers are finding invasive species are passing these old, toxic chemicals up the food web.
“Well, the zebra mussels and the quagga mussels, which is a cousin of the zebra mussels, are filtering the water of algae and sometimes other detrital material and PCBs will absorb to that material. Therefore, they accumulate high concentrations of toxic substances including PCBs. So any organism that eats those organisms are going to accumulate PCBs in their bodies.”
“Yes, sometimes there may be a different top predator involved but all the Great Lakes have places where this particular food web is in operation, except for Lake Superior. And, the other point I think I should make is that, again, this study was done in a highly contaminated area. In other areas of the Great Lakes, for example in Lake Michigan, you would not see this sort of uptake of PCBs. It’s only in these contaminated areas of concern across the Great Lakes that we’re seeing this sort of a pattern.” “The bigger the fish, which we found in this study, the more contaminants that they’re going to have. So you should be eating smaller fish and you should do everything you can to get rid of the fat.”
Excerpts from interview with David Jude, research scientist and a fish biologist at the University of Michigan, by Rebecca Williams published here: http://www.environmentreport.org/show.php?showID=459
Also see my other blog entry about lead going up the food chain thanks to zebra mussels and the fish that eat them here: http://lesamisdurichelieu.blogspot.com/2010/07/moules-zebrees-dans-le-lac-erie.html
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