The diatom Thalassiosira gravida under Arctic change: algal exudates and their microbial transformation under contrasting temperatures and photoperiods.

Temperature and photoperiod significantly influence algal DOC quantity and quality, with axenic Thalassiosira gravida cultures showing a 52% decrease in cell-normalized DOC at higher temperature and continuous light.

• Why it matters: Understanding how climate change alters phytoplankton-derived DOC and its microbial transformation is crucial for predicting carbon cycling in rapidly warming Arctic ecosystems.
• What they did: The study analyzed axenic and xenic cultures of Thalassiosira gravida at 9°C and 13.5°C under 16:8 h and 24:0 h light cycles, quantifying extracellular DOC and characterizing molecular composition via ultrahigh-resolution mass spectrometry.
• The result: Findings reveal that temperature and photoperiod modify DOC quantity and chemodiversity, with bacterial presence weakening treatment-dependent DOM responses, impacting carbon cycling in future Arctic conditions.