Phytoplankton in the sunlit layer of the ocean act as the base of the marine food web, and also regulate key biogeochemical processes such as exporting carbon to the deep ocean. Phytoplankton composition structure varies in ocean biomes and phytoplankton functional types (PFTs) drive differently the marine ecosystem and biogeochemical cycles. In the Arctic Ocean, phytoplankton are highly influenced by sea ice conditions and brine release, and their dynamics are influenced by the extent of stratification as this determines the timing of nutrient and light dependent biological production. Fram Strait (located between Svalbard and Greenland) as an important gateway to the Arctic, is a region where the cold ice-covered Arctic water exits from the western side and the warm Atlantic water enters the Arctic Ocean through the eastern side of the Strait. The two contrasting water masses interact in the central Fram Strait leading to complex phytoplankton dynamics especially under a rapidly changing Arctic climate. Within the framework of Copernicus Marine Service Evolution Program, we have established a complete and systematic approach for a consistent long-term monitoring of surface ocean PFTs of the global oceans. The two-decade observations enable us to study the inter-annual variation and analyze the trend of the surface phytoplankton community structure on different scales. Focusing on the Fram Strait, PFT observations from satellites will be evaluated with in situ time series from AWI established LTER (Long-Term Ecological Research) Observatory HAUSGARTEN area, that include data sets of bio-optical properties, pigment composition, phytoplankton taxonomic data from expeditions in the past years. We further investigate the trend and current state of the major PFTs; present and interpret their phenological patterns, inter-annual changes and the potential connections between the PFT shifts/trends and climate drivers in the Fram Strait.