Phytoplankton functional types from multi-sensor satellite observations – towards a long-term monitoring (2002-2020)

• Main Authors: Xi, Hongyan, Peeken, Ilka, Bretagnon, Marine, Brotas, Vanda, Gomes, Mara, Alvarado, Leonardo, Lampe, Vanessa, Losa, Svetlana N., Mangin, Antoine, Metfies, Katja, Nöthig, Eva-Maria, Bracher, Astrid
• Format: Conference Object
• Language: unknown
• Published: 2022
• Subjects: Fram Strait
• Online Access: https://epic.awi.de/id/eprint/55867/; https://epic.awi.de/id/eprint/55867/1/Xi_et_al_OSM2022_PFT_evaluation_timeseries.pdf; https://hdl.handle.net/10013/epic.83471b3a-5cad-4c2e-9f56-26c01d95f409

Phytoplankton in the sunlit layer of the ocean act as the base of the marine food web fueling fisheries, and also regulate key biogeochemical processes such as exporting carbon to the deep ocean. Phytoplankton composition structure varies in ocean biomes and different phytoplankton groups drive differently the marine ecosystem. As one of the algorithms deriving phytoplankton composition from space borne data, within the framework of the EU Copernicus Marine Service (CMEMS), OLCI-PFT algorithm was developed using multi-spectral satellite data collocated to an extensive in-situ PFT data set based on HPLC pigments and sea surface temperature data (Xi et al. 2020, 2021). It provides global PFT retrievals including chlorophyll a estimations of diatoms, haptophytes, dinoflagellates, chlorophytes and prokaryotic phytoplankton spanning the period from 2002 until today, by using multi-sensor merged products and OLCI data. These PFT products with per-pixel uncertainty are publicly available on the CMEMS. Due to different lifespans and radiometric characteristics of the ocean color sensors, it is crucial to evaluate the CMEMS PFT products to provide quality-assured data for a consistent long-term monitoring of the phytoplankton community structure. In this study, using in-situ phytoplankton data (HPLC pigment data further evaluated with microscopic, flow cytometry, molecular and hyperspectral optical data) collected from expeditions since 2009 in the tropical, temperate and polar (mainly Fram Strait within the PEBCAO network) regions, we aim to 1) validate the CMEMS PFT products and investigate the continuity of the PFTs data derived from different satellites, and 2) deliver two-decade consistent PFT products for times series analysis. For the latter we determine inter-annual trends and variation of the surface phytoplankton community structure targeting some key sub-regions (e.g.,east Fram Strait) that have been observed being influenced by the changing marine environment.