Mercury contamination of fish and its implications for other wildlife of the Tapajos Basin, Brazilian Amazon

Since 1979 the gold rush in the Brazilian Amazon has caused serious environ mental damage to one of the most complex ecosystems on Earth. Mainly due to the toxicity of mercury to humans, this problem has received wide public a ttention and prompted many studies. Although these studies have involved sa mpling of fish, the negative effect of mercury contamination to fish themse lves and other wildlife has been largely ignored. To assess the present lev el of mercury contamination of fish, and its implication for fish and other animals, we collected and examined data on mercury concentration in fish o f the Brazilian Amazon, especially for the Tapajos basin, between 1991 and 1996. We conclude that omnivores and piscivores that live nearer to gold mi ning areas in the Tapajos basin are already at high risk of mercury toxific ation, especially reproductive failure. Mercury concentrations in these fis h are also high enough to have detrimental effects on animals at higher tro phic levels. The same conclusion applies to other mercury-contaminated area s in the Brazilian Amazon. Because most Amazonian rivers or their tributari es have favorable conditions for mercury contamination, we can expect the p roblem to persist in the Amazon for a long time, and the consequences are l ikely to become more significant in the future. These conclusions have impo rtant implications for all tropical rainforests where gold mining operation s have caused extensive mercury pollution.