Turnover rates of photosynthesis determined by fluorescence kinetic analysis.

Maximum photosynthesis turnover rates in phytoplankton vary from 80 to 800 s^-1, depending on environmental conditions and nutrient availability, as measured by fluorescence kinetics.

• Why it matters: Understanding these rates is crucial because they set an upper limit on global primary production, yet traditional methods are inefficient and uncertain, limiting insights into oceanic productivity.
• What they did: A new method and instrumentation analyze chlorophyll fluorescence kinetics under saturating light to estimate maximum turnover rates in green algae and diatoms across diverse environments, measuring rates from 150 to 600 s^-1.
• The result: Turnover rates correlate strongly with cell growth rates and environmental factors, enabling a practical tool to assess nutrient effects on phytoplankton productivity and global oceanic primary production.