This text, written by a leading researcher in the field, describes the origin and formation of lakes in order to give context to the question of how lacustrine deposits form. It explains the process of sedimentation in lakes and the chemistry of those deposits and describes how the age of lake deposits are determined. Additionally, this book shows how different groups of fossils are used in interpreting the paleontological record of lakes. In order to illustrate the more synthetic approaches to interpreting the history of lakes, the author also discusses such special topics as lake-level history, lake evolution, and the impact of environmental change on lakes.

"Paleolimnology offers insights into long-term perspective in freshwater ecosystems and is useful to fill gaps in historical limnological data. Using multiple indicators to reconstruct ecological trajectory of lakes may strengthen our comprehension of their ecology over long time periods. Past ecological changes of lakes are often based on morphological remains archived in the sediments (e.g., diatom subfossils, cladocerans remains) as well as geochemical indicators (e.g., algal pigments, carbon and nitrogen content). However, many other organisms (e.g., bacteria, protists, copepods), which might play essential roles in the aquatic food webs, are not widely studied in paleolimnology. Technical advancements in molecular methods have opened the possibility of using DNA-based approaches applied to sediment extracts, which can greatly expand the number of taxa studied in paleolimnology. My research aimed (1) to evaluate the advantages and limitations of using DNA-based approaches in paleolimnology and (2) use both classical and DNA-based approaches to reconstruct past ecological dynamics of a peri-urban lake, Cultus Lake, British Columbia. In my second chapter, I used a contemporary 36-month time series to evaluate which taxa DNA can be deposited in the sediments. The specific goals were to assess the extent to which the micro-eukaryotic communities identified with the 18S rRNA gene in the sediments reflect the biological communities present in the water column, and to assess the congruence between morphological and DNA identification of diatoms and crustaceans in water and sediment extracts. From this chapter, I identified other potential taxonomic groups of organisms that could be studied in paleolimnology, such as ciliates, dinoflagellates, chytrids and cercozoans. The results also showed that DNA-based approaches are robust enough to reconstruct ecological dynamics from sediments, when compared to morphological data. Using morphological identification of diatoms from chapter 2 and contemporary limnological data, I evaluated the present ecological conditions of Cultus Lake to better assess how the lake deviated from its reference period. In chapter 3, I used multiple paleolimnological indicators and archival material of human history to reconstruct the ecological changes of Cultus Lake. The lake has experienced modest eutrophication since the mid-1900s, which was related to multiple stressors, such as an increase of anthropogenic use of the watershed, a warmer regional climate mainly after the 1970s, and a decrease in sockeye salmon escapement returning to the lake. This chapter indicates the importance of studying long-term perspective to understand the complexity of changes in lake ecosystems and their related drivers. In my last chapter, my objectives were to evaluate how micro-eukaryotic communities reconstructed with 18S rRNA gene changed in Cultus Lake over time and to compare the changes observed in micro-eukaryotic communities to the changes in classical paleolimnological indicators from chapter 3. Using both extracellular and intracellular DNA fractions archived in the sediments, I found that micro-eukaryotic community dynamics followed similar temporal dynamics than classical indicators. Intracellular DNA was more suitable to track long time periods as extracellular DNA seemed to have preservation issues after 30 years of burial. Overall, my doctoral thesis demonstrated that DNA-based approaches applied to sediment extracts were efficient to reconstruct past biological conditions and could increase our knowledge of ecological dynamics of lakes on a longer time scale when applied simultaneously with classical paleolimnological indicators"--

The Third International Symposium on Paleolimnology was held at the beginning of September 1981 in Finland. After registration at the University of 10ensuu and the opening session and welcome reception in the Town Hall, the participants moved to a hotel at Koli, a hill famed as a landmark and for its panoramic view. Here the lecture session, lasting four days, took place. Momentarily, the mosaic of the lakeland became visible between the clouds showing the hill slopes covered by mature spruce forest and scattered old birch trees, a reminder of the last slash-and-burn phase some 130 years ago. Altogether 120 paleolimnologists participated in the meetings and most also attended one of the two post-symposium excursions to the Arctic Circle and to South Finland. The lectures covered a wide range of paleolimnological subjects. The main topics, however, included current aspects in the dating of sediments and the history of eutrophication. The symposium was advised by the international organizing committee under the presidency of Professor Edward S. Deevey. Other members present at Koli were Dr. Maj-Britt Florin, Dr. Heikki Ignatius, Prof. Heinz Lamer, Prof. Gerbert Martinson and Dr. Magdalena Ralska-lasiewiczowa. They also gave direction to a discussion on future plans for international activity in paleolimnology. Later in the autumn, after the end of the symposium, the partici pants sent special thanks to the secretaries, Mrs. Eija Merilainen, Mrs. Tuula Nylander and Mrs. Anita Toukomaa, for solving individual problems during the symposium with smooth and rapid efficiency.

Introduction to Paleolimnology

This is the first book to describe the ecology of high latitude lakes, rivers and glacial environments in both the North and South polar regions. From the lake-rich floodplains of the Arctic to the deep, enigmatic waters of Lake Vostok, Antarctica, these regions contain some of the most extraordinary aquatic ecosystems on Earth. They provide a fascinating diversity of habitats for plant, animal and microbial communities, and are proving to be valuable model systems for exploring many ecological themes including landscape-lake interactions, adaptation of life to environmental extremes, and controls on the structure and functioning of aquatic ecosystems. Some of these waters also have direct global implications, including permafrost thaw lakes as sources of greenhouse gases, subglacial aquatic environments as a storehouse of ancient microbes, and Arctic rivers as major inputs of freshwater and organic carbon to the World Ocean. Given that many polar areas are experiencing greater climate warming than at lower latitudes, these ecosystems can also be viewed as sentinels of global change. This timely volume brings together many of the world's leading researchers in polar limnology to describe these diverse aquatic environments and their ecology. It introduces each major ecosystem type, examines the similarities and differences between Arctic and Antarctic systems as well as their responses to environmental change, and describes new frontiers for future research. A glossary of terms is provided for non-specialists, and a set of colour plates introduces the ecosystems and their biota. Polar Lakes and Rivers will be of value to students and specialist researchers alike, as well as to those with a more general interest in aquatic ecology, polar environments or global change who require an authoritative overview of this fast emerging topic.