Spatial Trends and Factors Affecting Mercury Bioaccumulation in Freshwater Fishes of Washington State, USA

Abstract

Twenty-four lakes in Washington State, United States, were sampled for largemouth and smallmouth bass as well as water chemistry parameters during 2005 to 2009 to evaluate trends in mercury (Hg) concentrations. We analyzed spatial patterns in bass Hg levels across a gradient of land and climate types, lake chemistry parameters, and physical watershed characteristics to identify factors influencing Hg bioaccumulation. Across the state, bass Hg levels followed rainfall patterns and were statistically greater on the coastal west side of the state and lowest in the drier eastern region. Lake and watershed variables with the strongest correlations to Hg bioaccumulation in bass were annual watershed precipitation (+) and lake alkalinity (-). Principal component analysis (PCA) explaining 50.3 % of the variance in the dataset indicated that wet, forested landscapes were more likely to contain lakes with greater fish Hg levels than alkaline lakes in drier agriculture-dominated or open space areas. The PCA did not show wetland abundance and lake DOC levels as variables influencing bass Hg levels, but these were generally associated with small, shallow lakes containing greater chlorophyll levels. The effect of in-lake productivity may have counteracted the role of wetlands in Hg bioaccumulation among this study's lakes.

Effect of eutrophication on mercury (Hg) dynamics in subtropical reservoirs from a high Hg deposition ecoregion

“…Land use affects nutrient and Hg transport to aquatic systems (Bremigan et al ; Betemariam et al ) and was an important HGM predictor for THg and MeHg concentrations in zooplankton. The negative relationship of zooplankton Hg concentrations with increasing % crop is consistent with the effect of % crop on fish Hg concentrations from lakes in agriculture and open areas of Washington State (Mattieu et al ). In subtropical reservoirs, increasing crop cover could lead to higher nutrient inputs and enhanced algal growth that may result in algal biodilution and/or somatic growth dilution.…”

Mercury Temporal Trends in Top Predator Fish of the Laurentian Great Lakes from 2004 to 2015: Are Concentrations Still Decreasing?

“…The trophic status of a lake, fish species, size, and age are important determinants of fish Hg concentrations. − For example, positive correlations have been reported between Hg concentration and fish size or age of a given species; , however, consumption of prey with a higher caloric content could cause a lower Hg concentration in predator fish due to growth dilution . These variables need to be analyzed and then controlled to better determine concentration trends and allow meaningful lake-to-lake comparisons. ,, Fish growth rate has varied significantly in some GL ecosystems because of changing lake-specific food webs caused primarily by invasive species and eutrophication. − Invasive species can also affect the methylation rate in a lake. For example, increased MeHg concentrations were found in nearshore regions of Lake Michigan (LM) with prominent invasive mussel infestations and associated filamentous benthic green algae …”

“…35 These variables need to be analyzed and then controlled to better determine concentration trends and allow meaningful lake-to-lake comparisons. 32,36,37 Fish growth rate has varied significantly in some GL ecosystems because of changing lake-specific food webs caused primarily by invasive species and eutrophication. 38−40 Invasive species can also affect the methylation rate in a lake.…”

Effects of hypolimnetic oxygen addition on mercury bioaccumulation in Twin Lakes, Washington, USA

“…Total Hg levels in trout from Washington lakes, based on annual reporting by the Washington State Department of Ecology over the past decade, typically range from 60 to 130 μg/kg ww (see [WSDOE] Washington State Department of Ecology, 2012 and earlier annual reports). Mean levels of total Hg assessed in largemouth bass (n = 10) from 18 Washington lakes ranged from 48 to 715 μg/kg dw (Mattieu et al, 2013). Of the nearly 200 fish sampled in Twin Lakes in 2011, only one hefty largemouth bass (1654 g) with 439 μg/kg ww total Hg most likely exceeded the USEPA tissue residue criterion of 300 μg/kg MeHg ww.…”