Contamination of the Freshwater Ecosystem by Pesticides

Cope, Oliver

A large part of our disquieting present-day pesticide problem is intimately tied to the freshwater ecosystem. Economic poisons are used in so many types of terrain to control so many kinds of organisms that almost all lakes and streams are likely to be contaminated. In addition to accidental contamination many pesticides are deliberately applied directly to fresh waters for suppression of aquatic animals or plants. The problem is intensified because of the extreme susceptibility of freshwater organisms. The complexity of freshwater environments and their variety makes it difficult to comprehend the total effect of pesticides. The freshwater environment is extremely variable and complex. Stationary ponds and lakes and flowing streams and rivers are very variable in content of water and of dissolved salts. Temperatures range from 0" C to about 38" C. The nature of the bottom is another important variable. The plants and animals extend throughout the phylogenetic scale, and may be fixed to the bottom or free living (floating or mobile) with populations fluctuating regularly or irregularly. We cannot define a 'typical' uncontaminated body of fresh water. Pesticides are economic poisons used to control a wide range of animals and plants. Many different chemicals have been developed to control many different pests. Inorganic and botanical chemicals have been used for years, but the 'pesticide problem' arose when organochlorine insecticides and growth hormone herbicides appeared in the nineteen-forties, and other synthetic organic materials followed. These chemicals had the advantages of high acute toxicity, low costs, residual properties and versatility of action; they provided an enormous variety of toxic agents that can contaminate the freshwater environment.

Contamination of the Freshwater Ecosystem by Pesticides

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