Osoyoos lakebed study to examine impact of settlement

There’s a lot of environmental history at the bottom of Osoyoos Lake. Starting June 16, researchers from UBC Okanagan and the B.C. Ministry of Environment will begin to reconstruct that history by sampling and analyzing sediments from the deepest parts of the lake.

They’ll be looking for chemical and biological clues about how human settlement in that part of the South Okanagan has impacted the environment during the past century and a half.

“Lakes are continually accumulating layers of sediment, and preserved in those sediments we have a variety of chemical substances,” says paleo-ecologist Ian Walker, Professor of Biology and Earth and Environmental Sciences at UBC Okanagan. “Sediment analysis will indicate the level of nutrient enrichment of the lake before European settlement of the area, and early in that settlement period.”

The research is a collaboration between the Okanagan Basin Water Board which provided primary funding, the B.C. Ministry of Environment, Okanagan Nation Alliance, UBC Okanagan, and the Osoyoos Lake Water Quality Society.

“Our intention is to reconstruct historic nutrient concentrations as well as look at the levels of contaminants entering Osoyoos Lake back to the late-1800s,” says Michael Sokal, Impact Assessment Biologist with the B.C. Ministry of Environment’s Environmental Protection Division in Penticton. “From this information, more accurate and supportable nutrient targets, particularly for phosphorus, may be set for Osoyoos Lake.”

The project will involve collecting sediment cores from two locations in Osoyoos Lake, and examining the sediment for the presence of specific toxins and other chemicals -- for example, phosphates, nitrates, the pesticide DDT, PCBs, lead and arsenic -- and algal remains which can indicate, for example, total phosphorus concentrations in the lake during the past.

Walker notes that if the results are similar to recent studies of sediments from Wood Lake in the Central Okanagan and Skaha Lake south of Penticton, the upper half-metre of sediments from Osoyoos Lake could reveal evidence of human activities such as fertilizing crops (adding phosphorus and nitrogen), spraying pesticides (historically a contributor of arsenic), and even driving cars with leaded gasoline (causing elevated lead levels).

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