NWT RESEARCH DATABASE

Regions: North Slave Region

Tags: arsenic, evolution, aquatic biodiversity

Objective(s): 1) To assess how arsenic pollution from historical gold mining has altered species distribution in lakes surrounding Yellowknife. 2) To collect preliminary samples to assess the evolutionary response of Daphnia pulex, a keystone zooplankton species, to historical arsenic pollution.

Project Description: This licence has been issued for the scientific research application No. 5868. This project is part of a long-term project that aims to determine ecological and evolutionary processes, and interactions between ecology and evolution (eco-evolutionary interactions), that are potentially limiting and/or facilitating the biological recovery of mining-impacted lakes around Yellowknife, NWT. The main objective of this year’s sampling (this permit application) is to assess how arsenic pollution from historical gold mining has altered species distribution in lakes surrounding Yellowknife. A secondary objective will be to collect preliminary samples to assess the evolutionary response of Daphnia pulex, a keystone zooplankton species, to historical arsenic pollution. To do so, freshwater biodiversity will be quantified using environmental DNA metabarcoding (eDNA: eukaryotic: 18S, bacterial: 16S, fish: 12S) applied to sediment cores. This will allow for the investigation of species distribution at multiple time periods: before the onset of gold mining, and after. Sediment cores will be taken from 15 remote lakes last sampled ten years ago for water chemistry, with the new addition of these ecological data, within 30 km of Yellowknife, NWT. Cores from some of the lakes will also be taken to investigate the presence of D. pulex resting eggs at different depths for a future evolutionary experiment. 1. Collection of sediment cores for eDNA analysis A gravity corer will be used to collect 3 sediment cores from each lake for dating and eDNA analysis. Zorbitol will be used to fix the cores and they will be kept whole and stored at 4°C at Aurora College until transport back to Montreal. The samples will be stored in a -20°C freezer at Aurora College until they are shipped back to Montreal by air. The cores will then be processed in the lab into 0,5 cm sections and stored at 80°C. All sampling equipment will be washed in 30% bleach between each lake to avoid contamination. 2. Collection of sediment cores for evolutionary experiment Sediment cores will be sampled from six lakes using a gravity corer. The cores will be cut into 1 cm sections with a Glew extruder on the lake shore and stored in individually labeled whirlpool bags. The samples will be stored in a -20°C freezer at Aurora College until they are shipped back to Montreal by air, where they will be stored at -80°C until further analysis. Sections from the cores will be investigated for the presence of Daphnia pulex resting eggs at different depths. 3. Collection of Zooplankton from the water column for community and Daphnia pulex genomics analyses Crustacean zooplankton communities will be collected by whole water column vertical tows with a 35-cm diameter Wisconsin net from 0.5 m off the bottom to the surface in deeper lakes, or gently pumped for a fixed volume using a bilge pump in shallow lakes less than 2 m deep. The zooplankton will be sampled from four sampling stations along an open water transect across each lake. The crustacean zooplankton will be anaesthetized with bromoseltzer, preserved with 95% ethanol, and they brought back to the laboratory at the Université du Québec à Montréal (UQAM) for identification. For community analysis, the samples will be pooled to a single sample per lake for identification and enumeration in the laboratory. The crustacean zooplankton will be identified to species level with a high- resolution dissecting microscope (and species will be enumerated for the number of individuals per L. Crustacean zooplankton will be counted using a protocol that targeted mature individuals that could be identified unambiguously to species, as well as to detect rare species (Mack et al. 2012). Daphnia pulex will be identified from the samples and put aside for whole genome sequencing. 1. Winter 2019 to Winter 2022: Communications for research planning and collaboration with Mike Palmer, Aurora College, are already in progress, and have been in progress since 2019 (pre-pandemic). 2. Winter 2024: First communication for intent of research project to the Yellowknives Dene First Nation will be sent by email following the submission of this permit application on January 30, 2024. 3. Summer 2024: field sampling and coordination with M. Palmer, Aurora College 4. Winter to summer 2024: reporting of preliminary eDNA results to Aurora College and Yellowknives Dene First Nation via in-person meeting. Collaboration with M. Palmer at Aurora College for sharing water chemistry and morphometric lake characteristics. The fieldwork for this study will be conducted from: July 05 - July 19, 2024