ABSTRACTS

Oral Session 8 | Wednesday, October 5, 14:40–15:00 | Abstract 537

Seasonal Dynamics of the Major Phytoplankton Groups in the West Coast of Canada Retrieved from CHEMTAX, OLCI Sentinel 3A and Hyperspectral Reflectance

Seasonal dynamics of the major phytoplankton groups (PGs) were addressed using output results from CHEMTAX (derived from HPLC pigment data), OLCI Sentinel 3A and hyperspectral data over the west coast of Canada during 2018 and 2019. Surface water samples for the HPLC pigment were collected from ~ 2 m depth using a seawater pump installed on the passenger ferry Queen of Alberni (QA). Level 1 full-resolution Sentinel 3 data were downloaded from the CODA marine website and processed using the POLYMER atmospheric correction algorithm. In addition, hyperspectral remote sensing reflectance was derived from the above water radiometer installed on the ferry’s bow. Here, we adapted a previously proven Empirical Orthogonal Function (EOF) algorithm developed using matchups between CHEMTAX data and EOF scores derived from OLCI (N=102) and hyperspectral reflectance (N=87). Model training using satellite data showed moderate retrieval for diatom and raphidophytes (R2=0.51, MDPD=56%; R2=0.49, MDPD=58%) and improved performance using hyperspectral data for PGs, including cryptophytes, cyanobacteria, diatom, dictyochophytes, dinoflagellates, haptophytes, prasinophytes, and raphidophytes (R2=0.58, MDPD=45%; R2=0.42, MDPD=54%; R2=0.70, MDPD=50%; R2=0.41, MDPD=45%; R2=0.36, MDPD=43%; R2=0.50, MDPD=38%; R2=0.66, MDPD=34%; R2=0.68, MDPD=66%, respectively). PGs derived from CHEMTAX, OLCI Sentinel 3, and hyperspectral spatial retrievals showed remarkable seasonal and spatial variability across the region, with diatom dominating spring and fall bloom and Heterosigma akashiwo bloom during summer 2018. To our knowledge, this is the first study that combines CHEMTAX, multispectral and hyperspectral data to elucidate major PGs on the West Coast of Canada.

*Vishnu P. Suseelan, University of Victoria, 0000-0003-1439-4939

Hongyan Xi, Phytooptics Group, Physical Oceanography of Polar Seas, Climate Sciences, Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research

Justin Del Bel Belluz, Hakai Institute

Midhun Sha Hussain, Department of Marine Biology, Microbiology and Biochemistry, Cochin University of Science and Technology

Astrid Bracher, Phytooptics Group, Physical Oceanography of Polar Seas, Climate Sciences, Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research

Maycira Costa, SPECTRAL Remote Sensing Laboratory, Department of Geography, University of Victoria