If so, then perhaps mitigation efforts are fruitless as this is the lake s natural state . All these as well as many other questions need to be considered in an historical context. Paleolimnological approaches are now being used in enlightened societies to tackle a large suit of environmental and management questions. Although most of the work thus far has been related to lake eutrophication and acidification, these powerful approaches can be used to study problems such as the introduction of exotic species, taste and odor complaints, erosion problems, the extirpation of populations, tracking contaminant trajectories, consequences of water level changes and impoundments, ozone depletion and resultant increases in ultraviolet radiation, and the repercussions of climatic change. The most commonly used biological indicators in paleolimnology are the glass cell walls of diatoms, a major group of algae consisting of over 10,000 species.
Diatoms are a very successful group of organisms that live in virtually every body of water.
They are characterized by having cell walls made up of two glass or siliceous halves, called valves. Diatoms have restricted nutrient requirements and they are sensitive indicators of lake trophic status. Sediment diatom assemblages are composed of a large number of taxa, and therefore contain considerable ecological information. Other biological indicators commonly used in paleolimnology include the scales and cysts of chrysophyte algae, shells and body parts of animals, and the chitinous exoskeletons of a large number of invertebrates. An effective approach to studying diatom communities with respect to lake water quality is to analyze the surface-sediment diatoms from a set of lakes with complete and reliable limnological data.