Paleolimnology

Paleolimnology (from Greek: παλαιός, palaios, "ancient", λίμνη, limne, "lake", and λόγος, logos, "study") is a scientific sub-discipline closely related to both limnology and paleoecology. Paleolimnological studies focus on reconstructing the past environments of inland waters (e.g., lakes and streams) using the geologic record, especially with regard to events such as climatic change, eutrophication, acidification, and internal ontogenic processes. Paleolimnological studies are mostly conducted using analyses of the physical, chemical, and mineralogical properties of sediments, or of biological records such as fossil pollen, diatoms, or chironomids. Most early paleolimnological studies focused on the biological productivity of lakes, and the role of internal lake processes in lake development. Although Einar Naumann had speculated that the productivity of lakes should gradually decrease due to leaching of catchment soils, August Thienemann suggested that the reverse process likely occurred. Early midge records seemed to support Thienemann's view. Hutchinson and Wollack suggested that, following an initial oligotrophic stage, lakes would achieve and maintain a trophic equilibrium. They also stressed parallels between the early development of lake communities and the sigmoid growth phase of animal communities – implying that the apparent early developmental processes in lakes were dominated by colonization effects, and lags due to the limited reproductive potential of the colonizing organisms. In a classic paper, Raymond Lindeman outlined a hypothetical developmental sequence, with lakes progressively developing through oligotrophic, mesotrophic, and eutrophic stages, before senescing to a dystrophic stage and then filling completely with sediment. A climax forest community would eventually be established on the peaty fill of the former lake basin. These ideas were further elaborated by Ed Deevey, who suggested that lake development was dominated by a process of morphometric eutrophication.