Salish Sea Marine Survival Project

22 7. Use of Satellite Imagery The Salish Sea is a highly productive marine ecosystem. Every year we see a spring diatom bloom in the Strait, which generally starts around the end of March, and sometimes a second bloom in the summer. 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 many factors such as ocean temperature, wind speed, cloud cover and ocean surface stratification caused by river inputs. The processes that produce the food for fishes are referred to as "bottom up" processes in ecological jargon. In some years, a "mismatch" may occur when phytoplankton blooms occur either earlier or later than usual resulting in less zooplankton production available for young fish to feed on. This can impact survival of the young salmon. Such interannual variability in phytoplankton and zooplankton has likely contributed to the variability in production of Chinook and Coho Salmon between years, and to its general decline since the 1980s. In order to address the impacts of bottom-up processes on salmon, detailed and long-term data on phytoplankton, zooplankton and oceanographic/environmental conditions are needed but often lacking. Satellites and other optical sensors aboard vessels and on 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 phyto- plankton 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. During the Salish Sea Marine Survival Project, researchers at the University of Victoria (UVic) used satellite imagery to determine bloom timing and hotspots of productivity, and how they translate to changes moving through the food web via zooplankton, and ultimately, juvenile salmon. Almost 15 years (from SeaWifs and MODIS) of spatial- temporal satellite-derived phytoplankton data and zooplankton samples were analyzed in relation to environmental data that have long time series (SST, Fraser River discharge, turbidity, wind, cloud cover) and large-scale climate indices. A second major project was to examine the change in kelp distribution over the past twenty years in areas of the Strait of Georgia. This project used historical satellite imagery. Figure 14. Satellite imagery of the development of the summer bloom in the Strait of Georgia. Images provided by Dr. Maycira Costa, University of Victoria. Figure 13. A hyperspectral above-water reflectance sensor used on BC Ferries. This sensor was used to validate satellite imagery, by gathering information on above-water reflectance. Photograph from Dr. Maycira Costa, UVic. July 21, 2018 July 26, 2018 July 22, 2018 July 28, 2018 July 25, 2018 July 30, 2018

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