Document Type
Article
Publication Date
5-1-2007
Publication Title
Proceedings of the National Academy of Sciences of the United States of America
Abstract
Rapid growth could significantly reduce methylmercury (MeHg) concentrations in aquatic organisms by causing a greater than proportional gain in biomass relative to MeHg (somatic growth dilution). We hypothesized that rapid growth from the consumption of high-quality algae, defined by algal nutrient stoichiometry, reduces MeHg concentrations in zooplankton, a major source of MeHg for lake fish. Using a MeHg radiotracer, we measured changes in MeHg concentrations, growth and ingestion rates in juvenile Daphnia pulex fed either high (C:P = 139) or low-quality (C:P = 1317) algae (Ankistrodesmus falcatus) for 5 d. We estimated Daphnia steady-state MeHg concentrations, using a biokinetic model parameterized with experimental rates. Daphnia MeHg assimilation efficiencies (≈95%) and release rates (0.04 d−1) were unaffected by algal nutrient quality. However, Daphnia growth rate was 3.5 times greater when fed high-quality algae, resulting in pronounced somatic growth dilution. Steady-state MeHg concentrations in Daphnia that consumed high-quality algae were one-third those of Daphnia that consumed low-quality algae due to higher growth and slightly lower ingestion rates. Our findings show that rapid growth from high-quality food consumption can significantly reduce the accumulation and trophic transfer of MeHg in freshwater food webs.
DOI
10.1073/pnas.0611261104
Dartmouth Digital Commons Citation
Karimi, Roxanne; Chen, Celia Y.; Pickhardt, Paul C.; Fisher, Nicholas S.; and Folt, Carol L., "Stoichiometric Controls of Mercury Dilution by Growth" (2007). Open Dartmouth: Published works by Dartmouth faculty. 1426.
https://digitalcommons.dartmouth.edu/facoa/1426
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