Omega-3 fatty acids in diatom-dominated biofilms in the Fraser River Estuary: Quantifying nutrient sources for migratory bird populations

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Many shore birds, such as Western Sandpipers, make extensive seasonal migrations up and down the coast of British Columbia in spring and fall. They spend their winters along the southern coasts of the US, and in Central and South America and they spend summer along the northern coasts of Alaska. Such long distance journeys require calorie- and nutrient-rich foods and which are supplied at very specific "re-fueling" locations. One such location is Roberts Bank situated on the south side of the estuary of the Fraser River ~35 kilometers south of Vancouver. Extensive biofilm communities are known to grow on the exposed intertidal mudflats in Roberts Bank and which account for approximately 45 - 68% of the total diet (50% of daily energy budgets) of Western Sandpipers. These biofilm communities are dominated by a group of algae called diatoms. Diatoms are known to be high in energy and nutrients and are rich in a type of lipid (fat) called omega-3 fatty acids; including two fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), that are known to be essential for the health of all vertebrates including birds. In particular, omega-3 fatty acids, like EPA and DHA, are known to be important to sustain flight of long-distance migrants such as shorebirds, and may therefore be critical for shorebird migration success. However, water conditions (e.g. salinity, temperature) may have a