Catchment Area Composition and Water Chemistry Heavily Affects Mercury Levels in Perch (Perca Fluviatilis L.) in Circumneutral Lakes

Abstract

The environmental impact on the mercury level in perch (Perca fluviatilis L.) is examined using Partial Least Squareregression (PLS) on 48 environmental descriptors assessingland use, various catchment area and lake characteristics,lake water chemistry, and fish stock. The lake specificintercepts of Hg content vs. fish length regressions are usedto describe the Hg level in the fish. The Hg levels in perchfrom 78 circumneutral lakes were largely influenced by landuse in the surroundings. Boreal forest lakes had the highestHg burden in the fish, while fish from lakes heavilyinfluenced by arable land possessed lower contents. The Hglevels also showed a negative relationship to the concentrationsof dissolved ions and total nutrients in lake water, and to theperch growth rate, whereas the relationship was positive to theconcentration of TOC/humic matter. Lake pH did not have any significant influence on the Hg content in perch in these circumneutral lakes. The Hg levels in perch from lakes surrounded by large amounts of wetland were less satisfactorily explained by the presently examined environmental descriptors, which suggests that the Hg burden in fish from these lakes are influenced by other factors.