POSTER Session 4

EVALUATING THE PERFORMANCE OF SATELLITE MULTISPECTRAL APPROACHES FOR ASSESSING PHYTOPLANKTON COMMUNITY COMPOSITION IN THE WEST ANTARCTIC PENINSULA

Phytoplankton communities in the Western Antarctic Peninsula (WAP) are undergoing recent changes in biomass, phenology, community composition and size structure. Shifts from diatoms to cryptophytes (nanoflagellates) impact both the food web due to krill’s preference for large-celled nutritious diatoms and the efficiency of the biological carbon pump. This study tests and validates the use of remote sensing multispectral ocean color for distinguishing phytoplankton groups in the WAP. We used the most extensive regional in-situ database of phytoplankton pigments obtained via High-Performance Liquid Chromatography (HPLC) from the Palmer LTER and GOAL cruises (1998-2021) with a regionally-tuned approach for identifying diatoms and cryptophytes. Reflectance data from both MODIS and multi-sensor products were matched to the HPLC data yielding over 500 stations in total and evaluated using random forest models. Our results show that multispectral data cannot be used to distinguish between diatoms and cryptophytes when normalizing for in-situ biomass. We will also investigate whether cryptophytes may be distinguishable with the additional channels of Sentinel 3 OLCI due to absorption and fluorescence features from the phycobiliprotein accessory pigments. This work sheds light on the complexity of using multispectral data in the WAP for phytoplankton community composition, highlighting the need for satellite hyperspectral missions (e.g. PACE OCI).

*Afonso Barros Barreto Ferreira, Marine and Environmental Sciences Centre (MARE), Faculdade de Ciências, Universidade de Lisboa, [email protected], https://orcid.org/0000-0002-2670-8125

Carlos R.B. Mendes, Laboratório de Fitoplâncton e Microorganismos Marinhos, Instituto de Oceanografia, Universidade Federal do Rio Grande, Brazil, [email protected]

Oscar Schofield, Department of Marine and Coastal Sciences, Rutgers University, NJ, USA, [email protected]

Ana C. Brito, Marine and Environmental Sciences Centre (MARE), and Aquatic Research Network (ARNET), Faculdade de Ciências, Universidade de Lisboa, Portugal, [email protected]

Jessica S. Turner, Department of Marine Sciences, University of Connecticut, CT, USA, [email protected]

Raul R. Costa, Laboratório de Fitoplâncton e Microorganismos Marinhos, Instituto de Oceanografia, Universidade Federal do Rio Grande, Brazil, [email protected]

Vanda Brotas, Marine and Environmental Sciences Centre (MARE), and Aquatic Research Network (ARNET), Faculdade de Ciências, Universidade de Lisboa, Portugal, [email protected]

Heidi Dierssen, Department of Marine Sciences, University of Connecticut, CT, USA, [email protected]

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