Impact of Warm Water Anomalies on Phytoplankton Composition in the Santa Barbara Channel

Abstract

Ocean color remote sensing enables the study of sea surface temperature (SST) and phytoplankton on a large scale, although coastal systems remain a challenge due to their optical complexity. Here I focus on the Santa Barbara Channel (SBC), a complex coastal system that lies in the lee of Point Conception, which partially shelters the region from strong equatorward winds that flow along the central California coastline. I use a remote sensing abundance-based approach that partitions Chlorophyll-a (Chl-a) concentrations by phytoplankton size class and functional type to estimate the underlying biomass composition. I validate the remote sensing classification method using matchups with in situ time series of phytoplankton abundance, and perform a regional spatial analysis of Chl-a and biomass composition in the SBC to improve understanding of how phytoplankton may respond to future ocean temperature shifts in coastal upwelling ecosystems. In 2005, delayed upwelling-favorable winds throughout the California Current System (CCS) triggered a warm water anomaly that coincided with increased levels of toxic dinoflagellate species. Then in 2013-2015 the oceanic phenomenon known as the Blob resulted in record water temperatures in the Northeastern Pacific Ocean. I examine whether the Blob triggered a similar shift in phytoplankton composition in the SBC as during the 2005 warm water anomaly. As harmful algal blooms (HABs) become less predictable and occur more frequently in the CCS, improvements to remote sensing methods for studying phytoplankton must be made for largescale analyses. To gain a socioeconomic perspective of this issue in California, I interview fishermen local to the Santa Barbara region and examine the effects that toxic blooms and warm water events have on their businesses.