BIO 2600, Literature review
Student number: 2029474
PARAMETERS AFFECTING MACROINVERTEBRATES DISTRIBUTION IN FRESHWATER
Aquatic macroinvertebrates are an important part of the food chain, especially for fish. Many feed on algae and bacteria, which are on the lower end of the food chain. Some shred and eat leaves and other organic matter that enters the water. Because of their abundance and position in the aquatic food chain, benthos plays a critical role in the natural flow of energy and nutrients. As benthos die, they decay, leaving behind nutrients that are reused by aquatic plants and other animals in the food chain (Internet 1).
Unlike fish, benthos cannot move around as much, so they are less able to escape the effects of sediment and other pollutants that diminish water quality. Therefore, benthos can give reliable information on stream and lake water quality. Their long life cycles allow studies conducted by aquatic ecologists to determine any decline in environmental quality. Macro invertebrates constitute a heterogeneous assemblage of animal phyla and consequently it is probable that some members will respond to whatever stresses are placed upon them (Hellawell, 1986).
Biomonitoring is the use of the biological responses to assess changes in environment. Therefore, macroinvertebrates are most frequently used as indicator species. Cairns & Pratt (1993) conclude that biological surveillance of communities, with special emphasis on characterising taxonomic richness and composition, is perhaps the most sensitive tool now available for quickly and accurately detecting alterations in aquatic ecosystems.
Conca and Wright (1992) states that ideally ecologists and managers should understand the processes which lead to the observed patterns of community structure in unstressed flowing-water systems and that this would provide a firm foundation from which to investigate the processes taking place when environmental stresses lead to community change, both structural and functional.
Many parameters will determine the distribution pattern of macroinvertebrates in freshwaters. Numerous studies and publications have been produced to determine which are the most relevant factors affecting this distribution.
Hynes (1960, 1970) has listed abiotic factors that predominately seem to affect macroinvertebrate population, they are, in order of importance of impact:
Current speed: many invertebrates have an inherent need for current either because they rely on it for feeding purposes or because their respiratory requirement demands it.
Temperature: intimately related to latitude, altitude, seasons, and relative distance from the source.
Substratum: certain species are confined to fairly well defined types of substratum.
Level of oxygen: main factor in polluted waters.
Salinity, acidity, hardness, and general water chemistry.