Project Funding: 2016 - 2017

NRA: 2015 NASA: Ocean Biology and Biogeochemistry   

Funded by NASA

Abstract:
The spatial distribution of phytoplankton biomass and its photophysiological responses to the environment in the upper ocean potentially can be inferred from satellite platforms (e.g., MODIS and, historically, MERIS) by analyzing the variations in solar induced fluorescence (SIF) originating from chlorophyll a. Although the SIF algorithm is potentially most advantageous in Case 2 waters, where DOM and suspended sediments interfere with chlorophyll algorithms based on blue-green water leaving radiances, the application of SIF to understanding either phytoplankton photophysiology or carbon fixation on a global scale has not yet been achieved. The variability in SIF quantum yields appears to correlate with environmental forcing, but the mechanisms responsible for and the interpretation of this variability are fundamentally not known due to very limited field studies of biophysically related processes. Within the framework of the NASA OBB funded project on “The application of lifetime analyses in the upper ocean to the interpretation of satellite-based, solar induced chlorophyll fluorescence signals (NNX08AC24G), we designed and constructed a sea-going instrument package to directly and simultaneously measure lifetimes and quantum yields of phytoplankton chlorophyll a fluorescence in the ocean. The quantum yields are accurately calculated from picosecond resolved measurements of fluorescence lifetimes and allowed for the first validation and calibration of the satellite-based retrievals of SIF quantum yields. This novel technology was deployed on ten cruises in the Atlantic, Pacific, Arctic, and Southern oceans spanning five years to infer the variability in phytoplankton physiology and SIF signals in major biogeochemical provinces of the ocean. The combination of amplitude-based variable fluorescence and lifetime measurements allowed us to deduce the global budgets of fate of solar radiation absorbed by phytoplankton for the first time. The results of this research are summarized in a paper Science (Lin et al. 2016). Here we propose to expand these robust and highly sensitive technologies to elucidate the patterns of global distributions of quantum yields of chlorophyll fluorescence in the ocean. This effort is essential to interpreting the variability of satellite-based retrievals of SIF quantum yields in relation to phytoplankton photophysiological responses to environmental forcing; e.g. nutrient availability on basin, meso-scale, and smaller spatial scales. Specifically, we propose to construct and deploy a network of five paired, calibrated instruments to be used by the oceanographic community throughout the world. The resulting data will be analyzed and archived at Rutgers University and distributed to the community via collaboration with the ocean color program at GSFC. We envision that this project will provide the scientific background for the interpretation of the variability in solar induced fluorescence signals in the ocean, help to improve MODIS chlorophyll based biomass algorithms (and potentially follow-on sensors on other satellites), and provide crucial physiological information needed for better estimates of primary production from remote sensing of the ocean color and solar induced fluorescence. We suggest that relating the space-based estimates to in situ measurements of chlorophyll fluorescence lifetimes will provide a pathway to robustly observe how photobiological energy utilization and dissipation processes in the global ocean potentially change in the future.

Publications:

Falkowski, P. G., Lin, H., Gorbunov, M. Y. 2017. What limits photosynthetic energy conversion efficiency in nature? Lessons from the oceans. Philosophical Transactions of the Royal Society B: Biological Sciences. 372(1730), 20160376. DOI: 10.1098/rstb.2016.0376

Lin, H., Kuzminov, F. I., Park, J., Lee, S., Falkowski, P. G., Gorbunov, M. Y. 2016. The fate of photons absorbed by phytoplankton in the global ocean. Science. 351(6270), 264-267. DOI: 10.1126/science.aab2213

Park, J., Kuzminov, F. I., Bailleul, B., Yang, E. J., Lee, S., Falkowski, P. G., Gorbunov, M. Y. 2017. Light availability rather than Fe controls the magnitude of massive phytoplankton bloom in the Amundsen Sea polynyas, Antarctica. Limnology and Oceanography. 62(5), 2260-2276. DOI: 10.1002/lno.10565

Shirshin, E. A., Nikonova, E. E., Kuzminov, F. I., Sluchanko, N. N., Elanskaya, I. V., Gorbunov, M. Y., Fadeev, V. V., Friedrich, T., Maksimov, E. G. 2017. Biophysical modeling of in vitro and in vivo processes underlying regulated photoprotective mechanism in cyanobacteria. Photosynthesis Research. 133(1-3), 261-271. DOI: 10.1007/s11120-017-0377-8

More details may be found in the following project profile(s):

• NASA Ocean Biology & Biogeochemistry (OBB) Project Profile