The effects of land use and habitat quality on fish and macroinvertebrate concordance, ecological community thresholds, and trophic structure: A case study of a perturbed watershed (Onondaga Lake Watershed, NY)

Increasingly, studies focused on streams and rivers are taking a landscape perspective, where the factors influencing ecosystem structure and function are examined at multiple scales. Fish and benthic macroinvertebrate assemblages were sampled at seventeen locations in the Onondaga Lake Watershed (Onondaga County, NY) in 2007 and from 2009 to 2011 to determine the effects of land use and habitat quality on: (1) assemblage-specific responses to environmental stressors, (2) fish and macroinvertebrate concordance, (3) community changes along an urbanization gradient, and (4) fish diet composition and feeding habits.;A comparison of assemblage-specific metrics and indices showed that fish and macroinvertebrate communities differed in their response to various environmental variables, resulting in discrepancies between assessments of ecological integrity. Similarly, concordance between assemblages was weak for all sample years and not significant (p < 0.05). Local variables, such as water chemistry and stream morphometry were significant to fish communities; whereas land use and stream conductivity were significant to macroinvertebrates (p < 0.05). Despite differences in the response of each group to environmental variables, both assemblages displayed a similar rural-urban gradient in composition; from cool-water, pollution intolerant species (rural) to warm-water, pollution tolerant species (urban). Threshold Indicator Taxa Analysis (TITAN) revealed that both fish and macroinvertebrate assemblages displayed a distinct decline in species frequency and abundance at a very low level of urban land use (~3%). The decrease in macroinvertebrate and fish taxa at relatively low urban land use appeared to be a function of reduced substrate suitability. Changes in environmental conditions also resulted in noticeable differences in prey selectivity and feeding habits of several fish species. Detrended correspondence analysis (DCA) revealed that the diet of fishes was significantly related to dominant subcatchment land use, in-stream substrate composition, and water chemistry to be significantly related to spatial changes in fish diet.;Collectively, the results of these studies showed that land use and habitat quality were important factors affecting fish and macroinvertebrate composition and food web structure. Though fish and macroinvertebrate assemblages responded differently to specific environmental stressors, both assemblages exhibited a negative response to increased urbanization and an associated reduction in stream habitat quality.