Macroinvertebrates

Benthic macroinvertebrates are organisms that inhabit the bottom substrates (sediments, debris, logs, macrophytes, filamentous algae, etc.) of freshwater habitats, for at least a part of their life cycle. Macroinvertebrates are those retained by mesh sizes of 500µm, although the early life stages of many macroinvertebrates species are smaller than this size (D.M. Rosenberg & V.H. Resh, 1993).

Stream invertebrates play an important role in the stream ecosystem. According to the River Continuum Concept, the distribution of stream invertebrates reflects the shift in location and types of food resources available in different-sized streams. Aquatic insects play an important role in the processing and cycling of nutrients mainly through (1) their feeding activities (2) bioturbation (3) the uptake, excretion and organic mineralization of phosphorus and (4) filtration of material from the water column. They are an important part of the food web. They act as primary consumers (animal that feeds on primary producers and/or decomposers) through 4 types of feeding mechanisms - filter-feeding, deposit-collecting, scraping and shredding. They also act as prey for higher organisms in the food web such as amphibians, fish and birds.

Stream invertebrates can be used as biomonitors. Biological monitoring can be defined as the systematic use of biological responses to evaluate changes in the environment with the intent to use this information in a quality control program. It can be used for surveillance or to ensure compliance (D.M. Rosenberg & V.H. Resh, 1993).

There are several advantages of using macroinvertebrates as biomonitors of stream health.

	A common and diverse group of animals which are found in all types of freshwater; therefore, they can be affected by environmental perturbations in many different types of aquatic systems and in habitats within those waters
	The large number of species involved offers a spectrum of responses to environmental stresses
	They are near the base of food chains, so may be vital agents of metal entry into food chains
	Many taxa are fairly sedentary and thus representative of local conditions. This allows effective spatial analyses of pollutant or disturbance effects.
	Many taxa are benthic and thus are closely associated with sediments
	Life span of several months allows integration of contaminants into their bodies (allows elucidation of temporal changes caused by perturbations). As a result, they act as continuous monitors of the water they inhabit, enabling long-term analysis of both regular and intermittent discharges, variable concentration of pollutants, and even synergistic or antagonistic effects
	They may accumulate metals and yet tolerate low-moderate metal concentrations

However, there are several disadvantages too.

	They do not respond to all impacts
	High numbers of samples are required to achieve desirable precision in estimating population abundance. Hence sample processing and identification requirements can be costly and time-consuming
	The distribution and abundance of organisms can be affected by factors other than water quality (e.g. natural conditions such as current velocity or nature of the substrate)
	Well defined seasonal variation in abundance and distribution, especially of insects, may create sampling problems during specific periods or in specific habitats, or may pose problems in comparing samples taken in different seasons
	Drift behavior in lotic waters can carry macroinvertebrates into areas in which they do not normally occur

Webpage designed and created by Jean V. D'sa (MSES), OSM Intern, Ohio University, Athens, Ohio - 45701

Send mail to jd346400@oak.cats.ohiou.edu or johnsok3@ohio.edu with questions or comments about this web site.

This webpage will be best viewed using Internet Explorer
Last modified: May 20, 2003

Webpage designed and created by Jean V. D'sa (MSES), OSM Intern, Ohio University, Athens, Ohio - 45701

Send mail to jd346400@oak.cats.ohiou.edu or johnsok3@ohio.edu with questions or comments about this web site.

This webpage will be best viewed using Internet Explorer Last modified: May 20, 2003

This webpage will be best viewed using Internet Explorer
Last modified: May 20, 2003