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Weak Effects of Urbanization on Macroinvertebrate Assemblages in Mid-continent, USA, Great Rivers
Citation:
ANGRADI, T. R. Weak Effects of Urbanization on Macroinvertebrate Assemblages in Mid-continent, USA, Great Rivers. Presented at 1st Triennial Symposium for the International Society of River Science, St. Petersburg, FL, July 12 - 17, 2009.
Impact/Purpose:
To study the effectsof urbanization on rivers
Description:
Effects of urbanization on rivers are not well studied in the US, especially for our largest rivers. We compared the macroinvertebrate assemblages on snags and in the littoral benthos between urban and non-urban reaches of the Upper Mississippi and Lower Missouri Rivers. We used National Land Cover Database data to define urban zones based on cover classes 22-24 at two spatial scales. We sampled over 300 sites between the two rivers. Major urban areas along the rivers include, St. Louis, Kansas City, the Quad Cities, Omaha, the Twin Cities, and others. Based on ordination and Bray-Curtis similarity analysis the assemblages were different between rivers and between habitats, but were not different not between urban and non-urban reaches for either river or habitat. Detailed analysis revealed a small number of taxa that did vary in relative abundance between urban and non-urban reaches. The maximum relative abundance of urban-tolerant or urban-intolerant taxa appeared to be limited by degree of urbanization, but at most sites, other factors were more important. Several taxa that are considered pollution intolerant in streams were more abundant in the urban reaches. Although water chemistry was not much different between urban and non urban reaches for most parameters, I speculate that variation in ion concentration and seston characteristics may account for the observed urban effects.