Ice nucleation of Organic and Inorganic Components of a Marine Coccolithophore (Emiliania huxleyi) and a Coccolithovirus
ALYSSA ALSANTE, Daniel Thornton, Sarah Brooks, Jessica Mirrielees, Elise Wilbourn, Brianna Hendrickson, Benjamin Diaz, Kay Bidle,
Texas A&M University Abstract Number: 364
Working Group: Aerosols, Clouds and Climate
AbstractIn the marine environment, aerosol contains a significant amount of organic matter derived from phytoplankton production. A subset of aerosol catalyzes the freezing of atmospheric ice crystals by acting as ice nucleating particles (INPs) at temperatures above the homogeneous nucleation threshold (-38°C), significantly influencing tropospheric cloud formation. In this study, we investigated the ice nucleation of a globally distributed coccolithophore species,
Emiliania huxleyi, before and after viral infection with a coccolithovirus (EhV-207) using a marine aerosol reference tank. Our results indicate the freezing temperature of calcifying
E. huxleyi (-27.5 ± 1.5°C) was not statistically different than seawater (-29.0 ± 2.3°C) aerosolized in the MART. Viral infection with EhV-207 did not influence the freezing temperature (-28.4 ± 0.7°C). However, EhV-207 virus particles had a mean freezing temperature of -20.8 ± 1.6°C (10
5 viruses mL
-1) in the absence of
E. huxleyi. To better understand why
E. huxleyi is not an efficient INP, we investigated an uncalcified strain of
E. huxleyi, purified coccoliths and dimethylsulfoniopropionate (DMSP). Uncalcified
E. huxleyi froze at -30.2 ± 0.7°C, indicating the calcium carbonate covering of calcifying
E. huxleyi has minimal impact on ice nucleation temperature. Purified coccoliths froze at a higher temperature (-25.3 ± 0.5°C) than either strain of
E. huxleyi. The organo-sulfur compound dimethylsulfoniopropionate (DMSP) is produced by coccolithophores in high internal concentrations (>100 mM). DMSP has a median freezing temperature of -34.0 ± 1.5 °C, suggesting this compound could be responsible for depressing the freezing temperature of coccolithophores and sea-spray aerosol containing organic matter and DMSP. These findings suggest that there may be compounds within specific taxa of phytoplankton inhibiting ice nucleation and marine viruses are potentially an abundant source of INP to the atmosphere.