Slocum glider observations during the spring bloom in the Strait of Georgia

A Slocum Glider mission was undertaken in the southern Strait of Georgia from February 18 - March 10, 2009. The glider flew a repeated 10 Km transect across the Strait, providing excellent meso-scale resolution of measured temperature, conductivity, dissolved oxygen concentration and saturation, chlorophyll a fluorescence, coloured dissolved organic matter fluorescence, and optical backscatter. During this mission, the glider was able to observe the early stages of the spring phytoplankton bloom. The sensors on the glider identify the physical and biological processes that occur in the Strait, many of which have been found to be important for the timing and development of the spring bloom. Glider fluorometer data show sub-surface pulses of high chlorophyll a concentration (>20 ¿g/L) in the Strait from February 19-25, 2009. These pulses were observed 5-20 m below the surface, to a maximum of 4 km wide. These signals were interpreted as part of the ¿Malaspina Dragon¿, a pattern of phytoplankton growth preceding the spring bloom, previously viewed with the Fluorescence Line Height (FLH) algorithm of the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Medium Resolution Imaging Spectrometer (MERIS) ocean colour satellites in 2005 and 2008. The ¿Malaspina Dragon¿ is a phytoplankton bloom originating in Sechelt and Jervis Inlets, spreading towards Malaspina Strait, and out into the Strait of Georgia. Strong winds in the Strait from February 25 - March 1 mixed the surface waters, and spread the phytoplankton throughout the Strait. The glider observed a strong bloom in surface chlorophyll a concentration over the entire mission area (10-15 ¿g/L) from March 3, until the end of the glider mission on March 10. Wind events breaking up the Malaspina Dragon may be a mechanism for early spring blooms in the Strait of Georgia.