Fossil pigments as a guide to the paleolimnology of Browns Lake, Ohio

Some aspects of the paleolimnology of Browns Lake, Ohio, have been ascertained by a study of preserved sedimentary plant pigments and conductivity of interstitial water. Temporal changes in the sedimentary environment, especially redox conditions, along with changes in the flora of the lake and the development of peat in the basin have brought about differential sedimentation and preservation of pigments. Measurement of changes in total and relative concentration and diversity of chlorophyll derivatives and carotenoids has provided important clues to late-glacial and postglacial evolution of the lake. Laminated sediments, rich in fossil remains, near the base of the core indicate eutrophic conditions and meromixis for several thousand years beginning shortly after lake inception. As meromixis broke down, the lake evolved gradually to holomictic conditions when sapropel was deposited. An advancing complex of reed swamp and fen forest began during midpostglacial time, providing ever-increasing amounts of highly organic, peaty sediments and continues to the present. The pond is now dystrophic, and increasing deposition of inorganic sediment is apparent at the top of the core, concomitant with land clearance and agriculture. In the same interval, an increase of water conductivity reflects recent agricultural practices and industrialization in the region.