Mercury Bioaccumulation in a Stream Network

Mercury Bioaccumulation in a Stream Network

2009

Mercury (Hg) contamination is common in stream and river ecosystems, but factors mediating Hg cycling in the flowing waters are much less understood than in the lakes and wetlands. In this study, we examined the spatial patterns of methylmercury (MeHg) concentrations in the dominant groups of aquatic insect larvae across a network of streams (drainage area ranging from 0.5 to 150 km2) in northern California during summer baseflow conditions. We found that, with the exception of water striders, all invertebrate groups showed significant (p < 0.05) increases in MeHg concentrations with drainage area. The largest stream in our study watershed, the South Fork Eel River, had the highest aqueous MeHg concentration (unfiltered: 0.13?0.17 ng L?1) while most of the upstream tributaries had aqueous MeHg concentrations close to or below the established detection limits (0.02 ng L?1). A filamentous alga abundant in South Fork Eel River (Cladophora glomerata) had an exceptionally high fraction of total-Hg as MeHg (i.e., %MeHg from 50?100%). Since other potential hotspots of in-stream Hg methylation (e.g., surface sediment and deep pools) had %MeHg lower than or similar to surface water (14%), we hypothesize that Cladophora and possibly other autotrophs may serve as hotspots of in-stream MeHg production in this bedrock-dominated stream. Recent studies in other regions concluded that wetland abundance in the watershed is the predominant factor in governing Hg concentrations of stream biota. However, our results show that, in the absence of wetlands, substantial spatial variation of Hg bioaccumulation can arise in stream networks due to the influence of in-stream processes.

Tsz Ki Tsui, Martin
Finlay, Jacques C.
Nater, Edward A.

U of M, Dept. of Soil, Water and Climate

6

Surface Water
Water Conveyance & Hydraulics

stream
streams
surface water
surface waters
surface-water
surface-waters
surfacewater
surfacewaters
water quality & pollutants
water quality and pollutants
water monitoring & assessment
water monitoring and assessment
mercury
methyl-mercury
methylmercury
MeHg
methyl mercury

2000-2009

Yes

Do Not Have Copyright Permission

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