Uncovering the legacy of DDTs in lake food webs

The ECAB Lab field team had a successful summer sampling brook trout and collecting water quality measures at New Brunswick lakes for the MSc research of Meghan Fraser. The 2020 field team included MSc students, as well as summer research assistants, and occasionally Dr. Kurek. We spent more than 20 days in the field between May and October, often working in remote areas of north-central and southern New Brunswick. Funding from New Brunswick’s Wildlife Trust Fund supported these research activities.

Our primary goal was to collect brook trout and use their muscle tissue to measure contaminants of concern, such as DDTs and mercury. DDT is an organochlorine pesticide used >50 years ago for pest management. Because of previous research at ECAB published in 2019, we know that DDTs are present in high concentrations in the sediments of several New Brunswick lakes. Now, we hope to determine the relationship between past DDT use and modern aquatic food webs in lakes across New Brunswick.

The field team, with the help of project partners at the Department of Natural Resources and Energy Development (NRED) and Parks Canada, collected brook trout from seven lakes. A total of 43 brook trout were collected and analyzed for DDTs and total mercury. Water quality measures, sediment samples, and invertebrates were also collected. With these diverse measures, we aim to show how levels of DDTs and mercury differ between lake food webs.

We targeted remote, headwater lakes with no major inflowing streams. Lake size, depth, fish stocking history, fish community composition, water chemistry, and location were also considered when choosing lakes to study. Our sampling techniques included angling with single, barbless hooks and collecting trout with fyke nets. Fyke nets were used after several failed angling attempts at a few lakes, and we were aided by our partners at NRED and Parks Canada.

Trout muscle tissues were freeze dried and homogenized before they were sent to Queen’s University Analytical Services Unit for DDT analyses and collaborator Karen Kidd’s lab at McMaster University for mercury analyses. Stable isotopes were also measured on trout at Mount Allison University to understand typical diets. Preliminary results were presented at the Science Atlantic Environment Conference in March 2021 by Meghan Fraser. Next steps for this project include invertebrate identifications, stable isotope analyses, and data synthesis.