Aquatic insects as environmental indicators

All life forms on the planet have a set of requirements for their existence. The existence of a taxa at a site indicates that the basic requirements are being met, at least for the stage observed, although they may not be optimal. Each taxa will have different requirements and varying optimal conditions, so that as environmental conditions change so will the populations of the taxa in a habitat. Even though the fauna of Newfoundland are impoverished, there are several hundred species of aquatic insects. These insects live in all types of aquatic habitats and are herbivores, carnivores, detritivores, and omnivores. They obtain this food by shredding, scraping, collecting and predation and have a range of substrate, water movement and chemical requirements. Thus by knowing the impact(s) on a taxa of a gradient of an environmental variable(s) it is possible to predict the conditions in a habitat by whether a taxon is absent or present plus its condition. Examples of the use of aquatic insects to indicate environmental condition will be given and how biotic indices have been developed.