Relationships between concentrations of mercury in largemouth bass and physical and chemical characteristics of Connecticut lakes

Concentrations of total mercury were determined for axial muscle tissue of 438 largemouth bass Micropterus salmoides from 46 lakes representing five regions in Connecticut to determine relationships between mercury concentrations and lake characteristics and to assess regional differences in mercury concentrations. Expected concentrations of mercury (EHg) predicted for a length of 356 mm for each population ranged from 0.103 to 0.795 mu g/g wet weight. Principal components analysis revealed that, in general, two types of lakes were represented in the data set and were grouped based on hydrologic characteristics. Type-II lakes (artificial impoundments) had a significantly lower mean retention time than type-I lakes (natural drainage lakes) and a significantly larger mean watershed area, watershed area : surface area ratio, watershed area:lake volume ratio, and shoreline development index. Mean EHg was approximately 20% higher in type-II lakes (0.514 mu/g wet weight) than in type-I lakes (0.410 mu g/g wet weight; P = 0.08); factors most strongly correlated with EHg differed between lake types. Largemouth bass EHg in type-I lakes was most strongly correlated to particulate phosphorus (r = -0.64) and conductivity (r = -0.55); EHg in type-II lakes was most strongly correlated with retention time (r = 0.76) and watershed area:lake volume ratio (r = -0.75). Stepwise multiple regression revealed that particulate P and mean depth accounted for 51% of the variability in EHg among type-I lakes. Retention time was the only variable retained in stepwise regression of type-II lakes and accounted for 57% of the variation in EHg. Largemouth bass EHg in type-I lakes was significantly different among regions, as were lake variables describing hardness, alkalinity, and productivity.