Estimation of primary production from hourly to annual scales: More than seven years of high-frequency measurements from the SMILE buoy
Résumé
Many observation systems of the littoral/coastal ocean focus on phytoplankton biomass but give little attention to primary production, which corresponds to flux measurements. Remote sensing of chlorophyll a concentration is commonly used to estimate primary production based on chlorophyll a stock data, but these results have rarely been validated by in situ measurements. To obtain a precise estimation of primary production, in situ measurements are essential. However, in coastal ecosystems, primary production varies strongly on very short time scales due to numerous environmental factors, which makes its estimation challenging. In the present study, a fully automated FRRF and then a LABSTAF (Chelsea Technologies Ltd) were developed and installed on the smart buoy SMILE in the Bay of Seine (English Channel, France). These systems enable the measurement of photobiological parameters based on single turnover flash fluorescence every two hours. These measurements were then used to estimate phytoplankton primary production from hourly to annual scales. The system is fully autonomous and provides a powerful tool for primary production assessments and photobiological studies in coastal ecosystems. The data acquired since 2017 (with some interruptions) are coupled with other high-frequency parameters such as nitrate concentration, salinity, light, and temperature. This integration allows us to better understand the physico-chemical and biological controls of primary production as well as the impact of extreme events.