Phytoplankton primary production is a crucial component of Arctic Ocean (AO) biogeochemistry, playing a pivotal role in the carbon cycling by supporting higher trophic levels and removing atmospheric carbon dioxide. The advent of satellite observations measuring chlorophyll a concentration (Chl_ a) has yielded unprecedented insights into the distribution of AO phytoplankton, enhancing our ability to assess oceanic productivity. However, the optical properties of AO waters differ significantly from those of lower‐latitude waters, and standard Chl_a algorithms perform poorly in the AO. In particular, Chl_a retrievals are challenged by interferences from other marine constituents including higher pigment packaging and higher proportion of light absorption by colored dissolved organic matter. To derive phytoplankton-originating signature as well as mitigate those effects, solar-induced chlorophyll fluorescence (SIF) emerges as a valuable tool for acquiring physiological insights into the direct photosynthetic processes in the AO. In this study, we leverage satellite-based SIF measurements to assess their correlation with a set of predictive factors influencing phytoplankton photosynthesis. We extend the temporal coverage of AO SIF data to cover the period 2004 - 2020. This novel dataset offers a pathway to monitor the physiological interactions of phytoplankton with changes in climate, promising to significantly improve our understanding of the Arctic water’s productivity. The application of this data is expected to provide insights into how phytoplankton respond to shifts in environmental changes, contributing to a more nuanced understanding of their role in High-Latitude Northern Oceans ecosystems.

Marine heatwaves, increasingly frequent, impact marine ecosystems and services. Still, understanding how temperature affects observed responses remains limited due to complex interactions among temperature, abiotic and biotic factors, and community dynamics. Here we try to fill this gap by exposing simulated plankton communities to seasonal heatwaves of 4°C with a trait- and size-structured model that accounts for protists and the life cycle of copepods. Despite the short lifespans and fast growth rates of plankton, results show that heatwaves affect communities differently and for an extended period up to six years after their appearance. Temperature affects species physiology and ecosystem dynamics, directly and indirectly, shaping structure and biomass. Species traits, interactions, and functional diversity under changing temperatures emerge as pivotal. Our study advances mechanistic insights into marine heatwave impacts, highlighting the complex connections between temperature, species traits, and ecological interactions.