Document Detail

Algal blooms reduce the uptake of toxic methylmercury in freshwater food webs.
MedLine Citation:
PMID:  11904388     Owner:  NLM     Status:  MEDLINE    
Mercury accumulation in fish is a global public health concern, because fish are the primary source of toxic methylmercury to humans. Fish from all lakes do not pose the same level of risk to consumers. One of the most intriguing patterns is that potentially dangerous mercury concentrations can be found in fish from clear, oligotrophic lakes whereas fish from greener, eutrophic lakes often carry less mercury. In this study, we experimentally tested the hypothesis that increasing algal biomass reduces mercury accumulation at higher trophic levels through the dilution of mercury in consumed algal cells. Under bloom dilution, as algal biomass increases, the concentration of mercury per cell decreases, resulting in a lower dietary input to grazers and reduced bioaccumulation in algal-rich eutrophic systems. To test this hypothesis, we added enriched stable isotopes of Hg to experimental mesocosms and measured the uptake of toxic methylmercury (CH3 200Hg+) and inorganic 201Hg2+ by biota at several algal concentrations. We reduced absolute spike detection limits by 50-100 times compared with previous techniques, which allowed us to conduct experiments at the extremely low aqueous Hg concentrations that are typical of natural systems. We found that increasing algae reduced CH3Hg+ concentrations in zooplankton 2-3-fold. Bloom dilution may provide a mechanistic explanation for lower CH3Hg+ accumulation by zooplankton and fish in algal-rich relative to algal-poor systems.
Paul C Pickhardt; Carol L Folt; Celia Y Chen; Bjoern Klaue; Joel D Blum
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.     Date:  2002-03-19
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  99     ISSN:  0027-8424     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  2002 Apr 
Date Detail:
Created Date:  2002-04-03     Completed Date:  2002-04-25     Revised Date:  2010-09-14    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  4419-23     Citation Subset:  IM    
Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA.
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MeSH Terms
Daphnia / metabolism
Food Chain*
Fresh Water
Methylmercury Compounds / metabolism*
Water Pollutants, Chemical / metabolism*
Zooplankton / metabolism
Grant Support
Reg. No./Substance:
0/Methylmercury Compounds; 0/Water Pollutants, Chemical

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