Daily dynamics of phytoplankton photosynthetic parameters in the surface layer.

Daily photosynthesis quantum yield (φ) in the Black Sea surface layer varies significantly, with Fv/Fm decreasing up to 50% and Ik increasing threefold at midday.

• Why it matters: Understanding these daily dynamics is crucial for accurately estimating primary production in marine ecosystems, which impacts global carbon cycling models.
• What they did: Researchers analyzed the dependence of Fv/Fm and Ik on photosynthetically available radiation (PAR) over daily cycles, developing methods to retrieve Ik dynamics based on measurements at specific times.
• The result: The proposed approaches accurately estimated the daily average φ across most times, especially when measurements were taken near midday, enhancing the precision of primary production assessments.