Satellite observations of seeding of the spring bloom in the Strait of Georgia, BC, Canada

Abstract

ABSTRACTWe extend our previous observations of the spring bloom in the Strait of Georgia, Canada using Moderate Resolution Imaging Spectroradiometer (MODIS) satellite images, to include both a longer time period (2000–2016) and a wider variety of ‘seeding’ bloom events. We have reported on blooms in inlets to the north of the Strait, which appear to seed the main spring bloom in a characteristic ‘Malaspina Dragon’ pattern, leading to significantly earlier spring bloom dates in some years. Here, we double the time period of those observations. We find no clear repetitions of the earlier dragon pattern, but several instances of seeding from other inlets, with varying impacts on spring bloom timing. In situ monitoring has increased in coverage in recent years in the main body of the Strait, and we have deployed a fluorometer to record blooms at one inlet location, but observations of blooms in inlets rely mostly on satellites. We discuss the spatial and temporal resolution requirements imposed by the spatial scale of inlets and the temporal scale of blooms and cloud cover. In these waters, we find chlorophyll fluorescence images more useful than the standard chlorophyll product, restricting the value of NASA’s Visible Infrared Imaging Radiometer Suite (VIIRS) sensor and suggesting increased value from ESA’s Ocean and Land Colour Imager (OLCI) in the future, especially when two instruments are in orbit.