Impacts of urbanization on stream habitats and macroinvertebrate communities in the tributaries of Qiangtang River,China |
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Authors: | Beixin Wang Dongxiao Liu Shuru Liu Yong Zhang Dongqi Lu Lizhu Wang |
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Institution: | (1) Department of Entomology, College of Plant Protection, Nanjing Agricultural University, Nanjing, 210095, Jiangsu, China;(2) College of Environment and Resource, Nanjing Agricultural University, Nanjing, 210095, Jiangsu, China;(3) Institute for Fisheries Research, Michigan Department of Natural Resources and University of Michigan, 212 Museums Annex Building, Ann Arbor, MI 48109, USA |
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Abstract: | The impacts of watershed urbanization on streams have been studied worldwide, but are rare in China. We examined relationships
among watershed land uses and stream physicochemical and biological attributes, impacts of urbanization on overall stream
conditions, and the response pattern of macroinvertebrate assemblage metrics to the percent of impervious area (PIA) of watersheds
in the middle section of the Qiantang River, Zhejiang Province, China. Environmental variables and benthic macroinvertebrates
of 60 stream sites with varied levels of watershed urban land use were sampled in April, 2010. Spearman correlation analysis
showed watershed urbanization levels significantly correlated with increased stream depth, width, and values of conductivity,
total nitrogen, ammonia, phosphate, calcium, magnesium, and chemical oxygen demand for the study streams. There was significant
difference in total taxa richness, Empheroptera, Plecoptera, and Trichoptera (EPT) taxa richness, and Diptera taxa richness,
percentages of individual abundances of EPT, Chironomidae, shredders, filterers, and scrapers, and Shannon–Wiener diversity
index between reference streams and urban impacted streams. In contrast, percentages of individual abundances for collectors,
oligochaeta, and tolerant taxa, and biotic index were significantly higher in urban impacted than reference streams. All the
above metrics were significantly correlated with PIA. The response patterns of total taxa richness, EPT taxa richness, and
Shannon–Wiener diversity index followed a drastic decrease at thresholds of 3.6, 3.7, and 5.5% of PIA, respectively. Our findings
indicate that stream benthic macroinvertebrate metrics are effective indicators of impacts of watershed urban development,
and the PIA-imperviousness thresholds we identified could potentially be used for setting benchmarks for watershed development
planning and for prioritizing high valued stream systems for protection and rehabilitation. |
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