Libera N, Ruhland 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. XX:XXX-XXX.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 similar to 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.

Eutrophication, which remains one of the greatest threats to water quality worldwide, is particularly acute in agricultural areas. Here we assessed long-term drivers of potential pollution inputs to lakes in southwest Nova Scotia (Canada), a region marked by fur farming (mainly mink) and other agricultural activities. We used a BACI (before-after-control-impact) study design with sediment cores collected from 14 lakes selected based on their proximity to mink farms. We combined economic data, mink faecal samples, and a series of geochemical markers in dated sediment cores, including sterols, δ15N, visible reflectance spectroscopy (VRS)-inferred chlorophyll-a, and heavy metals, to relate changes in sediment geochemistry to the growth of mink farms in the region. Sterol biomarkers (cholesterol and β-sitosterol) measured in a range of samples (i.e. mink faeces and feed, aquaculture feed), were elevated where mink farms were located close to each study lake. Mink-related sterols (cholesterol, β-sitoserol), δ15N measurements, VRS chlorophyll-a, and heavy metals As, Cu, Sr increased in the 1980s coeval with a ∼400% increase of mink farms in the region, especially near Nowlans Lake. Agricultural impacts were subtler in other lakes. Our study expands on prior applications of geochemical fingerprinting in forensic paleolimnology when direct monitoring data are incomplete. This multi-proxy approach has promising applications for environmental pollution assessments in other lake ecosystems experiencing water quality issues.

Human activities in the headwaters of the Carleton River Watershed (southwest Nova Scotia, Canada) are suspected to have led to nutrient enrichment of freshwaters, resulting in downstream effects. However, the presence of multiple nutrient sources in the headwaters, including mink fur farming and land-based aquaculture, have made it difficult to distinguish the dominant stressor(s). We used sedimentary chironomid and chaoborid remains and visible reflectance spectroscopy of sedimentary chlorophyll-a (VRS chl-a) to assess the timing and nature of limnological changes in two shallow eutrophic-hypereutrophic lakes that have been directly monitored for water quality since 2008. The catchment of eutrophic Hourglass Lake contains one mink farm and an aquaculture operation, and the outlet of Hourglass Lake flows into hypereutrophic Placides Lake through a watershed with several mink fur farms. Midge assemblages at Hourglass Lake showed a compositional shift (ANOSIM: 0.65, P < 0.001) coincident with the start of aquaculture in ~ 1990. However, the Chaoborus:chironomid (chaob:chir) ratio and midge-inferred volume-weighted hypolimnetic oxygen (VWHO) did not reflect decreased concentrations of dissolved oxygen. Midge assemblages at hypereutrophic Placides Lake showed no significant compositional shift and the chaob:chir ratio and inferred of dissolved oxygen were stable over the ~ 80-year record. It is likely that hypolimnetic oxygen concentrations have not decreased markedly in these productive lakes. Trends in VRS chl-a were also relatively stable at Placides Lake despite decades of nutrient inputs from the upstream watershed. High water colouration of these eutrophic-hypereutrophic shallow lakes may have increased their resilience to nutrient inputs from the catchment. Moreover, our study confirms that midge assemblage composition does not respond directly to phosphorus inputs in these shallow, stratified lakes. We highlight the stability of midge assemblages to decades of nutrient inputs from a land-based aquaculture operation and mink fur farms.

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. XX:XX-XX. 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.

This paper presents the tidypaleo package for R, which enables high-quality reproducible visualizations of time-stratigraphic multivariate data that is common to several disciplines of the natural sciences. Rather than introduce new plotting functions, the tidypaleo package defines several orthogonal components of the ggplot2 package that, when combined, enable most types of stratigraphic diagrams to be created. We do so by conceptualizing multi-parameter data as a series of measurements (rows) with attributes (columns), enabling the use of the ggplot2 facet mechanism to display multi-parameter data. The orthogonal components include (1) scales that represent relative abundance and concentration values, (2) geometries that are commonly used in paleoenvironmental diagrams created elsewhere, (3) facets that correctly assign scales and sizes to panels representing multiple parameters, and (4) theme elements that enable tidypaleo to create elegant graphics. Collectively, this approach demonstrates the efficacy of a minimal ggplot2 wrapper to create domain-specific plots.

Mink fur farming was once a widespread agricultural activity in southwestern Nova Scotia. Freshwaters near to and downstream of several mink fur farm operations have experienced severe water quality issues, including eutrophication and recurring algal blooms. Here, we use dated lake sediments to examine trends in primary producers and primary consumers from a hypereutrophic lake to assess how cladoceran assemblages have responded to extreme eutrophication. Shifts in the dominant pelagic cladoceran taxa began in the early 1900s, coinciding with an increase in sedimentary chlorophyll-a concentrations. Notably, small-bodied bosminids decreased, while taxa such as Chydorus brevilabris and Daphnia pulex spp. dominated assemblages in recent decades. Bottom-up ecological factors, such as decades of greater primary production, were the likely drivers of assemblage shifts of primary consumers. Consistent body sizes of bosminids throughout the sedimentary record suggested that pelagic cladocerans were not influenced solely by predation pressure from macroinvertebrates or fish. This study provides evidence of large-scale ecological shifts occurring at multiple trophic levels in a hypereutrophic temperate lake with mink farming operations in its catchment.

The Athabasca Oil Sands Region (AOSR) in northeast Alberta contains Canada’s largest reserve of hydrocarbons, and the third largest in the world. Extraction and processing operations generate contaminants and nutrients that are aerially deposited across the region. However, structured environmental monitoring efforts were only initiated decades following the establishment (1967) and escalation (~ 1980) of commercial operations. We examined whether diatom assemblages preserved in 210Pb-dated sediment cores retrieved from strategically selected lakes have responded to aerial deposition of contaminants. The relative amount of contaminant inputs was tracked using sedimentary dibenzothiophene (DBT) concentrations and DBT enrichment factors, which are established proxies for AOSR activities. We observed no relationship between diatom assemblage changes and DBT enrichment. The nature of the diatom changes differed among lakes, regardless of DBT enrichment, suggesting that diatom responses were related to site-specific conditions. Moreover, diatom assemblage changes at several sites tracked trends in whole-lake primary production. Collectively, these records indicate that regional warming is likely the primary driver of recent diatom assemblage changes in these shallow, closed-basin lakes.