Impact of Extreme Climate Events on Coastal Phytoplankton Abundance and Diversity in the Southern California Bight, California, USA.

Long-term observations of temperature and salinity at Scripps Pier, La Jolla began in 1916 and expanded in 1930 to include phytoplankton species abundance. Over 40 years of phytoplankton observations have been collected at Scripps Pier by researchers, E. W. Allen (1930-1939), J. McGowan et al. (1983-2000), L. Busse et al. (2003-2005), and current efforts (2008-2018) through the Southern California Coastal Ocean Observing System. Current and historical observations are used to evaluate the change in abundance and diversity of phytoplankton species over time in relation to a warming ocean.

Long term warming and recent temperature increases associated with anomalous warm water (“blob”, summer 2018 marine heat wave) have been observed in southern California. The biological responses of primary producers to these events include a major decline in chlorophyll concentration, abundance, and diversity at Scripps Pier. Warm temperatures and low chlorophyll have also been observed at the three Southern California Bight (SCB) stations, however the most northern station (Cal Poly Pier), just outside of the SCB shows varied results. Preliminary results of the plankton response during two other major warming events (1930-31) and (1997-98) are compared to (2013-2018) at Scripps Pier, La Jolla.