The Impact of Climate Change on the Fraser River may Result in Increased Algal Blooms in the Strait of Georgia

Abstract:

The Fraser River is one of British Columbia's most diverse and valuable ecosystems. Water levels and temperatures along the Fraser are seasonally variable, with high flow during the spring freshet and low flow during winter months. The Fraser River is affected by urbanization and agriculture in the Fraser Valley, and mountain pine beetle and logging in other areas. Biological oxygen demand (BOD) is an indicator of water quality in freshwater environments as it measures the amount of oxygen consumed by bacteria during the decomposition of organic matter, relative to the total available dissolved oxygen (DO). We found BOD of the Fraser River at Fort Langley was higher in the summer than winter, but no relationship between BOD and nutrient concentration (NH4, NO2+NO3, PO4). There did appear to be a positive correlation between BOD and turbidity. There is increased agricultural input into the river in the summer: increasing dissolved organic matter (DOM) and coarse and fine particulate organic matter, as well, turbidity increases during the spring freshet. The Fraser River plume contributes to Strait of Georgia algal blooms. These blooms can occur as early as March and end as late as September. The algal bloom in the Georgia Strait does not correlate to nutrient levels in the river, but is more closely related to river turbidity and dissolved organic matter (DOM). It is predicted this algal bloom will become more prominent as the sediment and DOM levels increase in the Fraser River due to the loss of forests in the watershed from the Mountain pine beetle.