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Tuesday, May 27, 2008
356
Response of chironomidae to multiple gradients of urban impact
Susan E. Gresens, Biological Sciences, Towson University, 8000 York Road, Towson, MD 21252-0001
Twenty-five Baltimore (Maryland) area streams were surveyed to determine the response of chironomid communities to environmental changes associated with urbanization. Surface-floating chironomid pupal exuviae were collected in conjunction with measurement of nutrients, periphytion abundance, sediment particle size distribution, and concentration of sediment-bound metals. Results are presented for mid-June, when maximum emergence was expected. Richness of emerging chironomids ranged from 57 to 8 species, declining with increasing catchment urbanization. Richness showed a significant negative relationship to total phosphorus (TP), and a unimodal relationship to peak periphyton abundance. Ordination using non-metric multidimensional scaling produced one axis strongly associated with landuse: forested streams, having sandier beds were contrasted with more urban streams having higher TP, algal abundance and conductivity. In contrast, the second axis distinguished a subset of urban streams associated with high metal concentrations. Richness of Tanytarsini species was greatest in streams in forested catchments. Cricotopus and Rheocricotopus spp. were associated with urban streams having high metal concentrations, whereas Polypedilum scalaenum gr. sp., Nanocladius spp. and Cryptochironomus sp. characterized urban streams with lower sediment metal concentrations. Although richness of midsummer-emerging chironomids declined with urbanization, the urban streams varied greatly in chironomid community composition.
Web Page: Chironomidae, biodiversity, urbanization
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See more of The Nabs 56th Annual Meeting (25-28 May, 2008)