Blackflies + Mudsnails (IMAGE)
Caption
Blackflies have the highest mercury concentration among Grand Canyon invertebrates. As larvae (top), they are important fish prey. When blackflies emerge as adults, they transfer mercury to birds, bats, lizards, and spiders on land. New Zealand mudsnails (bottom) contain mercury but are indigestible to trout; when fish eat them, they pass through unscathed. When the snails die and decompose, the mercury they contain is released back into the river.
Credit
Credit: US Geological Survey/Freshwaters Illustrated-Dave Herasimtschuk
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