Seasonal and Size-specific Distribution of Methylmercury in Seston and Zooplankton of Two Contrasting Great Lakes Embayments

Cleckner, Lisa B.; Back, Richard C.; Gorski, Patrick R.; Hurley, James P.; Byler, Steven M.

doi:10.1016/s0380-1330(03)70422-5

Cited by 14 publications

(16 citation statements)

References 25 publications

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“…Even for the other elements the size fractions were often different for a given lake and date, but the differences were less consistent across lakes and dates (i.e., the date x size interaction within lakes accounted for the largest proportion of the variation). Similarly, other studies that tested for differences in MeHg concentrations across zooplankton size fractions found significant differences (Back et al, 2003; Cleckner et al, 2003; Kainz et al, 2002; Masson and Tremblay, 2003; Paterson et al, 1998; Plourde et al, 1997; Tremblay et al, 1998). However, our review of the literature revealed that most studies (74%) do not separate zooplankton size fractions.…”

Section: Discussionmentioning

confidence: 72%

Assessing element-specific patterns of bioaccumulation across New England lakes

Ward

Mayes

Stürup

et al. 2012

Science of The Total Environment

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Little is known about differences among trace elements in patterns of bioaccumulation in freshwater food webs. Our goal was to identify patterns in bioaccumulation of different elements that are large and consistent enough to discern despite variation across lakes. We measured methylmercury (MeHg) and trace element (As, Cd, Hg, Pb, and Zn) concentrations in food web components of seven New England lakes on 3–5 dates per lake, and contrasted patterns of bioaccumulation across lakes, metals and seasons. In each lake, trace element concentrations were compared across trophic levels, including three size fractions of zooplankton, planktivorous fish, and piscivorous fish. The trophic position of each food web component was estimated from N isotope analysis. Trace element concentrations varied widely among taxa, lakes and sampling dates. Yet, we identified four consistent patterns of bioaccumulation that were consistent across lakes: (1) MeHg concentration increased (i.e., was biomagnified) and Pb concentration decreased (i.e., was biodiminished) with increased trophic position. (2) Zinc concentration (as with MeHg) was higher in fish than in zooplankton, but overall variation in Zn concentration (unlike MeHg) was low. (3) Arsenic and Cd concentrations (as with Pb) were lower in fish than in zooplankton, but (unlike Pb) were not significantly correlated with trophic position within zooplankton or fish groups. (4) Average summer concentrations of As, Pb, Hg, and MeHg in zooplankton significantly predicted their concentrations in either planktivorous or piscivorous fish. Our secondary goal was to review sampling approaches in forty-five published studies to determine the extent to which current sampling programs facilitate cross-lake and cross-study comparisons of bioaccumulation. We found that studies include different components of the food web and sample too infrequently to enable strong cross-lake and cross-study comparisons. We discuss sampling strategies that would improve our capacity to identify consistent patterns of bioaccumulation and drivers of elevated trace element concentrations under naturally high levels of variability.

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Section: Discussionmentioning

confidence: 72%

Assessing element-specific patterns of bioaccumulation across New England lakes

Ward

Mayes

Stürup

et al. 2012

Science of The Total Environment

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“…Previous research on the Great Lakes had identified the importance of riverine mixing zones on nearshore bioaccumulation of MeHg by phytoplankton and zooplankton. 21 For this study, we assessed the influence of riverine and Cladophora− quagga assemblages as potential sources of MeHg. Sampling began at the Manitowoc River mouth, and CDOM was used to follow the plume south (SI Figure S2).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Influence of Cladophora–Quagga Mussel Assemblages on Nearshore Methylmercury Production in Lake Michigan

Lepak

Krabbenhoft

Ogorek

et al. 2015

Environ. Sci. Technol.

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Recent spread of invasive mussels in Lake Michigan has altered primary productivity in the nearshore zone, resulting in proliferation of filamentous benthic green algae (Cladophora glomerata). In areas of dense Cladophora and quagga mussel (Dreissena bugensis) assemblages, as well as in regions where sloughed Cladophora accumulates, methylmercury (MeHg) production is enhanced. A shoreline transect from a river mouth through waters overlying Cladophora/quagga-rich zones showed that aqueous MeHg concentrations increased, despite river dilution. Cladophora, as primary producers, ranged from 0.6 to 7.5 ng g(-1) MeHg [4-47% of total mercury (Hg) as MeHg], and were higher than MeHg concentrations in offshore-collected seston. Concentrations of MeHg in decaying Cladophora accumulated onshore ranged from 2.6 to 18.0 ng g(-1) MeHg (18-41% as MeHg) and from 0.1 to 3.0 ng g(-1) MeHg (2-21% as MeHg) in deposits of recently sloughed and accumulated Cladophora in a nearshore topographical depression. Relative to offshore open waters, interstitial waters within decaying Cladophora from onshore and nearshore deposits were elevated in MeHg concentration, 1000- and 10-fold, respectively. Percent Hg as MeHg was also elevated (65-75% and 9-19%, respectively for onshore interstitial water and nearshore interstitial water, compared to 0.2-3.3% as MeHg for open water). Quagga mussels collected within growing Cladophora beds in the nearshore zone were significantly higher in MeHg than offshore counterparts. Our combined results suggest that recent changes in nearshore primary production contributes to MeHg production and bioaccumulation in Lake Michigan.

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“…However, in this study, samples were collected only during the summer. MeHg concentrations often exhibit seasonal fluctuations, with comparatively higher levels during the spring, likely because of growth dilution from increased phytoplankton biomass during the summer Cleckner et al, 2003). Precise comparisons are also limited by variability in analytical methodologies.…”

Section: Methylmercury and Total Mercury Concentrationsmentioning

confidence: 99%