Historical impacts of mink fur farming on chironomid assemblages from shallow lakes in Nova Scotia, Canada

Abstract Campbell J, Libera N, Smol JP, Kurek J. 2022. Historical impacts of mink fur farming on chironomid assemblages from shallow lakes in Nova Scotia, Canada. Lake Reserv Manage. 38:80–94. Mink fur farms in southwestern Nova Scotia, Canada, are a suspected source of nutrients that have likely contributed to water quality issues in nearby lakes. Despite a decade of water quality monitoring, the cumulative effects of mink farming are not fully known due to a lack of information regarding baseline conditions. We used sedimentary midge remains and visible reflectance spectroscopy of sedimentary chlorophyll a (VRS Chl-a) to assess environmental changes prior to and following the establishment and growth of the local mink farming industry. Study lakes include hypereutrophic Nowlans Lake, with mink farms near its shoreline, mesotrophic Porcupine Lake with mink farms upstream, and oligotrophic Clearwater Lake (reference lake) with no mink farms in the catchment. We recorded a significant compositional shift in midge assemblages at Nowlans Lake (ANOSIM: 0.63, P < 0.001) following an increase in VRS Chl-a and the growth of the industry ca. 1970. Midge assemblage changes were indicative of a deterioration of benthic habitat and included increases in taxa associated with productive environments (i.e., Glyptotendipes, Endochironomus, and Cricotopus). Porcupine and Clearwater lakes, however, showed no significant assemblage shifts, suggesting relatively stable benthic conditions. VRS Chl-a increased around the 1950s in Porcupine Lake, whereas VRS Chl-a in Clearwater Lake increased around the 1980s. Our findings indicate that impacts from mink farming should be considered from a site-specific context. This study highlights the complexity of shallow lake responses associated with human activities related to >50 yr of mink farming.