Paleolimnology

Due to their hydrologically closed nature, saline lakes are very responsive to past and present climate change. Paleolimnologists can track these climatic changes by examining cores from lake sediments. Preserved in the core are biological, geological and chemical signals - essentially clues which can reveal not only the ecological history of the lake but the surrounding landscape as well. Paleolimnological examination of cores from saline lakes, for example, has been used to predict the duration and frequency of droughts on the Canadian prairies. During droughts, evaporation rates increase and in saline lakes, as water is lost, salinity increases. As salinity increases, the numbers of algal species able to tolerate this increase decline and species change. Scientists can track these changes by first cutting lake sediment cores into sections and dating them. Dating techniques for these core sections include use of the following: radioactive carbon-14 (14C) and lead-210 (210Pb) isotopes, pigment remnant analysis, plant pollen and spore analysis, algal microfossil analysis, plant macrofossil analysis and fossilized remains of Cladocera, ostracods, and midges. Because the outer shells (silica valves) of diatoms are so well preserved in sediments, past changes in their communities can be related to historical changes in nutrient chemistry and salinity due to variations in climate and lake levels. Also, by-products of plant pigments, are often well preserved in sediments and so the stratigraphy of chlorophyll and carotenoid (plant pigments) degradation products can also be used to determine historical lake productivity.

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