Before and after mink fur farming: water chemistry and sedimentary diatom assemblages in lakes from southwestern Nova Scotia, Canada

Abstract

Libera N, Rühland KM, Kurek J, Smol JP. 2024. Before and after mink fur farming: water chemistry and sedimentary diatom assemblages in lakes from southwestern Nova Scotia, Canada. Lake Reserv Manage. 40:18–35. Since the 1930s, farmed mink pelts have been an important contributor to the economy of rural Nova Scotia (NS, Canada). However, these farms are a potential source of pollutants to nearby ecosystems. To determine how regional lakes have been affected by fur farms, we compared modern water chemistry and sedimentary diatom assemblages in 14 lakes in southwestern Nova Scotia. We categorized lakes into 3 groups: (a) 5 lakes with fur farms in the catchment or near inlets; (b) 4 lakes downstream from or near fur farms; and (c) 5 reference lakes without hydrological connection to fur farms. To assess whether lake conditions have changed since the establishment of fur farms, we conducted a “before-and-after” paleolimnological analysis comparing surface sediments (representing modern environments) to dated sediments deposited prior to fur farm operations. Diatom assemblages registered distinct responses to eutrophication in several hypereutrophic lakes with farms within their catchment boundaries. In lakes ∼25 km downstream from fur farms, diatom assemblage changes were more characteristic of climate warming and acidification than of eutrophication, despite surface water nutrient concentrations well above levels in reference lakes. We found no association between the presence of fur farms and surface water trace metals that could potentially bioaccumulate and/or biomagnify. Our data indicate that decades of nutrient inputs from fur farms have caused eutrophication at several lakes where fur farms are close to the shoreline or to inlet streams.