Spatial differences in macroinvertebrate community structure in springs in southeastern Ontario in relation to their chemical and physical environments

This study examined the benthic macroinvertebrate communities of 20 springs in southeastern Ontario in relation to major water chemical variables and temperature. Significant differences were evident among the spring communities, and a TWINSPAN classification showed three major groups, which were associated with different levels of urbanization and water chemical conditions. Canonical correspondence analysis (CCA) ordinations indicated that the major environmental gradient was related to temperature and NH₄ and to two springs adjacent to a landfill site. CCA ordination of a sub-data set excluding these latter two sites together with 3 closely related variables better illustrated the response of spring communities to different levels of urbanization. The strongest relationship to emerge was that between taxon occurrences and chloride, a major contaminant in groundwater in the study area and believed to be derived from road salt. Several taxa were closely associated with high chloride levels (e.g., Tipulidae and Ceratopogonidae), whereas others occurred only in springs with low chloride levels (e.g., Gammarus pseudolimnaeus and Turbellaria). The possibility of using spring macroinvertebrates as biological indicators of chloride contamination of groundwater is discussed.