SCOR Working Group 156

Active Chlorophyll fluorescence for autonomous measurements of global marine primary productivity

Phytoplankton (single-celled algae) control marine food webs and the cycles of important nutrients in the ocean, such as carbon, nitrogen, phosphorus, and iron. The growth of phytoplankton, called primary productivity, strongly influences the oceanic uptake of carbon dioxide from the atmosphere, thus exerting a significant impact on global climate. Understanding how and why marine primary productivity changes over space and time requires frequent and consistent measurements with standardized approaches. Such measurement intensity cannot be achieved with most existing methods, which rely on the collection of individual bottle samples.  Recent developments in automated instrumentation have enabled rapid and continuous measurements of active fluorescence from chlorophyll a, the main photosynthetic pigment in algae.  These active fluorescence measurements yield quantitative estimates of photosynthetic electron transport rates, which in turn, can be used as a measure of primary productivity.  Although the theory of active fluorescence is well developed, the application of this method to derive primary productivity remains limited by a number of factors, including differences among investigators in measurement approaches and data interpretation. With the increasing use of active fluorescence sensors by research groups around the world, it is critical to develop conceptual and practical approaches ensuring that results from these measurements remain inter-comparable.  Our group will develop a series of bench mark standards of practice, focusing on both hardware configurations and data analysis approaches for the retrieval of photosynthetic parameters from active fluorescence measurements, and the conversion of electron transport rates into primary productivity estimates.  We will also establish a framework to integrate active fluorescence measurements into a global database that will support a richer understanding of the temporal and spatial variability in marine productivity.

Chair(s)
David Suggett (Australia) and Philippe Tortell (Canada)
Other Full Members
Aurea Ciotti (Brazil), Tetsuichi Fujiki (Japan), Maxim Gorbunov (USA), Zbignew Kolber (USA), Jacco Kromkamp (Netherlands), Mark Moore (UK), Kevin Oxborough (UK), Nina Schuback (Switzerland), and Sandy Thomalla (South Africa)
Associate Members
Ilana Berman‐Frank (Israel), Doug Campbell (Canada), Kim Halsey (USA), Anna Hickman (UK), Yannick Huot (Canada), Ondrej Prasil (Czech Republic), Greg Silsbe (USA), Stefan Simis (UK), and Deepa Varkey (Australia)
Reporter
Sinjae Yoo
Terms of Reference
  1. To inter‐compare active Chla induction measurements across instruments and approaches, identifying key aspects of instrument configuration, deployment and parameter acquisition that may introduce variability in retrieved data.

  2. To develop, implement and document internationally agreed best practice for data acquisition, standardised output formats and archiving approaches.

  3. To develop, implement and document internationally agreed best practice for processing raw fluorescence data to retrieve photosynthetic parameters and primary productivity estimates, taking into account taxonomic and environment factors driving diversity in chlorophyll fluorescence signals in the ocean. From this work we will develop freely available software and documentation to allow non‐specialist users to process fluorescence data according to these best practices.

  4. To produce a new synthesis of parallel 14C and active Chla induction measurements that can be used to examine the relationship between these two productivity metrics under a range of field conditions. We will also consider other metrics of Net Primary Production alongside 14C.

  5. To develop a global database structure for hosting quality‐controlled active Chla induction measurements, creating standards for data and meta‐data collection, submission and archiving.

  6. To build a framework through which in situ active Chla induction data can be used to validate and refine relevant remote sensing measurements (e.g., sun‐induced fluorescence yields).

  7. To share knowledge and transfer skills in instrumentation, best practice, quality control and data stewardship with the rapidly expanding user community in developing nations.

Approved
September 2018
Financial Sponsors
SCOR, NSF