The Salish Sea Marine Survival Project: Canadian Program Summaries summarizes findings from the Pacific Salmon Foundation’s five year study on salmon declines in the Strait of Georgia.
Issue link: http://digital.canadawide.com/i/1354465
31 SATELLITE IMAGERY AND ITS VALUE TO THE SALISH SEA MARINE SURVIVAL PROJECT BACKGROUND The Salish Sea is highly productive, especially during spring when resident and migratory fish populations are either spawning or entering the region. The high productivity is closely linked to phytoplankton and the subsequent zooplankton blooms, and the former is characterized by the annual spring diatom bloom which generally starts around the end of March. The timing of phytoplankton blooms and associated increases in zooplankton, which feed on the phytoplankton, is highly variable in the Salish Sea as a result of a combination of biophysical factors such as ocean temperature, wind speed, cloud cover and ocean surface stratification caused by river inputs (or "bottom-up" processes). In general, a "mismatch" year when phytoplankton blooms occur either earlier or later than usual results in fewer zooplankton prey being available for young fish to feed on, which lowers the chance of the fishes survival. As a result, interannual variability in phytoplankton and zooplankton likely contributes to the variability in salmon production (e.g., Chinook and Coho) over the last 50 years, and its general decline since the 1980s. In order to address the impacts of bottom-up processes on salmon, detailed and long-term data on phytoplank- ton, zooplankton and oceanographic/environmental conditions are needed, but often lacking. Satellites and other optical sensors aboard vessels and buoys can provide this information at the needed spatial and temporal scales. Satellites detect a signal which is a function of the particles and dissolved matter in seawater, and this can be used to estimate properties of the water such as phytoplankton biomass, water turbidity and even the type of phytoplankton such as harmful algae. Operational ocean colour satellites such as MODIS-Aqua and Sentinel-3 provide a great opportunity for continuous data acquisition at high temporal resolution — and a great opportunity for future monitoring. QUESTIONS ADDRESSED DATA CONCLUSIONS What are the interannual differences in the timing of the spring bloom and bloom duration in the Northern and Central regions of the Strait of Georgia? How do plankton respond to climate drivers? How do variations in phytoplankton relate up the food web to zooplank- ton, and ultimately, to salmon? How have kelp distributions changed historically in the Strait? Satellite-derived chlorophyll (Chl_a) climatology from 2003-2016 was constructed to determine interannual differences in the timing of the spring bloom, bloom duration and anomalies in the Northern and Central regions of the Salish Sea. Data from ferries, PSF citizen science vessels and the DFO-IOS database were used to validate satellite data. Environmental drivers (Photosynthet- ically Active Radiation, Fraser River discharge, Sea Surface Temperature etc.) collated for 2003-2016. Historical satellite imagery for Kelp: ground-truthing from kayaks. Bloom timing varies from year to year. Some regions of the Strait of Georgia have seasonal hotspots with area of particularly high concentrations of Chl_a. Environmental drivers influence Chl_a differently in the Northern vs Central subregions. Chl_a anomalies in the Northern region were tightly coupled with large-scale North Pacific climate indices, but the Central region was influenced more by localized factors. Satellite imagery may be used (under certain conditions) to assess changes in kelp distribution in the Strait.