Salish Sea Marine Survival Project

32 USE OF SATELLITE IMAGERY During the Salish Sea Marine Survival Project, researchers at the University of Victoria (UVic) used satellite imagery to examine the link between phytoplankton and zooplankton using long-term data from specific regions within the Salish Sea. Almost 15 years (from SeaWifs and MODIS) (Figure 1) of spatial-temporal satellite-derived phytoplank- ton 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. SeaWifs and MODIS are two principal Earth Observation sensors. 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 acquired by SPOT and WorldView. SPOT and WorldView are two principal Earth Observation satellites. SUMMARY OF RESULTS TO DATE Identify the seasonal patterns and interannual variability in phytoplankton Spatio-temporal satellite-derived chlorophyll (Chl_a) was constructed over the time period 2003-2016 to determine interannual differences in the timing of the spring bloom and in the northern and central regions of the Strait of Georgia (Figure 2). Figure 3 shows the spatial extent of Chl_a in the "northern" and "central" Strait. Over time, the highest median Chl_a concentrations were observed in the central region of the Strait of Georgia in spring 2005 and 2015, and fall of 2008. Similar peak timings were also observed in the northern region of the Strait, but to a lesser degree. Low Chl_a concentrations were observed in spring 2011 in both regions. Spatially, further analyses of the satellite data has indicated that there are hotspots, areas that show particularly high concentrations of Chl_a. For example, the highest concen- trations of Chl_a in the spring were located in the south- ern portion of the central region near the mouth of the Fraser River. During summer, the highest Chl_a concentra- tions tended to occur in coastal areas of the central region and on the eastern side of Texada Island. Satellite imagery was also used to calculate the timing of the spring bloom. Bloom initiation was defined as the 8-day week where Chl_a was greater than a threshold value equal to the annual median plus 5%, and concentra- tions during one of the two following weeks were higher than 70% of the threshold value. The average spring bloom initiation throughout the time series was the end of March (Day 88). Earlier-than-average bloom initiation years were 2005 and 2015, whereas 2007 and 2008 had later-than-average blooms (Figure 4). Figure 2. Spatial maps showing chlorophyll a concentrations for spring, summer and fall 2003-2016 in the Strait of Georgia. Figure provided by Dr. Karyn Suchy, UVic. Figure 1. This image shows an example of satellite-derived Chlorophyll-a information. The signal of Chl-a is used as a proxy for the phytoplankton bloom. This image shows a strong bloom presence in the centre of the Strait of Georgia during July 2018. Figure provided by Dr. Maycira Costa, UVic.

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