Developmental Changes in the Historical and Present-Day Trophic Status of Brown Water Lakes. Are Humic Water Bodies a Uniform Aquatic Ecosystem?

Abstract

The long-term development of three humic lake ecosystems in Poland was investigated through palaeoecological analyses of sediment cores. These wetland records spanning the Holocene were analyzed for plant macroremains, degree of peat decomposition, sediment geochemistry along with radiocarbon dating. Morphological characteristics of the catchments and data on contemporary water quality and management approaches were integrated. Our research on the palaeoecology of humic lakes suggests two main states: humic and eutrophic-humic. Of the lakes studied, only one consistently presented features typical of the humic type. The other two showed various states, and dynamic patterns of transformation. The results indicate that these systems can change from humic to eutrophic-humic, and back again, in response to catchment-linked factors, climatic change and human impact. Thus determination of uniform pattern in the development of humic lakes is questionable. This suggests that a reassessment of brown water lakes is necessary.