Presenter: Melissa Carter (Scripps Institution of Oceanography/ UCSD)

Description:
An unprecedented red tide of Lingulodinium polyedra occurred along the coast of southern California in spring 2020. These blooms are common in southern California and have often been regarded as benign with little concern for ocean and human health impacts. Yet, in May 2020, the red tide was followed by a massive death event of fishes and invertebrates, and 25% of beachgoers surveyed reported symptoms of sore throat, watering eyes, and dermatitis. Chemical analysis targeting yessotoxin and analogs were performed from SIO Pier over the course of the bloom on both the particulate and dissolved phases of seawater as well as on sea spray aerosols. Cell concentrations of L. polyedra peaked at 42 million cells L^-1 on April 30^th, yet sustained abundance of L. polyedra persisted at over 1 million cells L^-1 for over a month. The production of yessotoxin during the peak of the bloom was very low with values ranging between 0.01 and 1 fg cell^-1. No yessotoxin analogs were detected. Due to high cell abundance, the total concentration of yessotoxin in seawater still ranged between 0.5 and 4 ng L^-1. Dissolved yessotoxin was also detected and observed the same trend as the particulate yessotoxin. Yessotoxin was also detected in the aerosols throughout the bloom, and was particularly high in late April. This is first reported detection of yessotoxin in aerosols associated with blooms of L. polyedra. This presentation will focus on trends in yessotoxin production and their aerosolization, 18S rRNA, and environmental data during the 2020 bloom.