ISSN:
1573-2932
Keywords:
mercury
;
methylmercury
;
benthic invertebrates
;
lakes
;
reservoirs
Source:
Springer Online Journal Archives 1860-2000
Topics:
Energy, Environment Protection, Nuclear Power Engineering
Notes:
Abstract Total mercury (Hg) concentrations in benthic insects from a 14 years old hydroelectric reservoir (La Grande 2) were 2 to 3 times higher than those from a reference lake and, in some groups, up to 7 times. The difference was even more pronounced for methylmercury (MeHg) concentrations, with a mean of 4 fold and a maximum of 12 fold between systems. The enrichment factors (dw) of insects, relative to the substrate in which they reside was around 3 for total Hg and 6 to 22 for MeHg. On the basis of their diet, we have classified the insects into four different trophic levels: detritivores, grazers, grazers-predators and predators. In insects collected in the reservoirs, the McHg:Hg ratio was 20–25% in dipterans-ephemeropterans (detritivores) and 30–40% in trichopterans (grazers), but 60–85% in heteropterans-coleopterans (grazers-predators) and 95% in odonates (predators). The pattern was similar in the lake with slightly lower values. In both systems, the proportion of MeHg increases in direct relation to our defined trophic levels. Given that insects are an important food source for many fish, our results suggest that they are a strong vector of McHg to these fish in hydroelectric reservoirs. The bioavailability of MeHg to insect larvae appears to depend on the nature and composition of the substrate in which they reside.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00666262
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