ARE ELEVATED INCIDENCES OF MOUTHPART DEFORMITIES IN CHIRONOMIDAE EARLY WARNING INDICATORS OF ZOOBENTHIC COMMUNITY EFFECTS?

J.J.H. Ciborowski, J. Baillargeon, M. Doherty, L.A. Hudson, G. Pardalis, E.O. Swansburg, and M.E. Whelly. Department of Biological Sciences and Great Lakes Institute for Environmental Research, University of Windsor, Windsor, Ontario, Canada N9B 3P4

Biomarkers are attributes of individuals used to infer environmental stress or to warn of imminent effects at population, community, or ecosystem levels. Chironomid deformities are morphological anomalies reflecting disruption of development. We evaluated incidences of mentum deformities (extra or missing teeth) and chironomid community composition in 6 studies to ascertain whether deformities were more sensitive indicators than community-level measures. We examined at least 100 chironomids/site in A) western Lake Erie (multiple sites - 1982 vs. 1993); B) St. Clair and Detroit rivers (reference vs. degraded sites); C) 10,000-L microcosms receiving experimental creosote applications; D) New Brunswick streams (5 pairs of sites upstream/downstream of metal mines); E) wetlands in NE Alberta (3 pairs: reference vs. those receiving oil sands mining process water); and F) rivers in NE Alberta (3 rivers upstream/downstream of exposed natural bitumen deposits). Significantly elevated incidences of deformities (at least 50% above reference; p<0.01) were observed at stressed locations in studies A-D but not in E or F. There were marked differences in chironomid community composition (richness and relative abundances of genera) among treatments in all studies except F. Deformity incidences can be useful indicators of contaminant-induced teratogenicity, but they accompany rather than anticipate chironomid community-level change.