Skip to main content

Regional phytoplankton ecophysiology products for coastal waters from local and satellite measurements

Final Report Summary - PHY2COAST (Regional phytoplankton ecophysiology products for coastal waters from local and satellite measurements)

Mapping primary productivity of coastal seas is an essential, but far from operational, part of monitoring ecosystem health. The optical complexity and spatial heterogeneity of the waters prevents accurate extrapolation of ship-based measurements as well as retrieval of phytoplankton biomass from satellite imagery.

The Baltic Sea is a eutrophic, isolated and shallow sea suffering high anthropogenic stress, as well as an ideal ground to develop new optically-based measurement techniques. Annual phytoplankton blooms include toxin producing cyanobacteria with a specific range of optical properties that require dedicated observation methods.

The PHY2COAST project aimed to contribute to improved mapping of phytoplankton biomass in terms of the main photosynthetic pigment, chlorophyll-a, and of the solar energy available for phytosynthesis, expressed as the vertical diffuse attenuation coefficient (Kd). The project also aimed to improve fluorometric measurements to assess the photosynthetic capacity of harmful blooms, in particular cyanobacteria. To achieve this, a fast repetition rate fluorometer (FRRF) was custom built to yield sensitivity to cyanobacteria that was higher than the one exhibited by the existing commercially available models. The final objective of PHY2COAST was to assess the spatial variability of photosynthetic parameters using research vessels and, where possible, to use ship-based assessment of primary production to seed synoptic observations using satellite imagery.

Following particularly large scale bloom events during the summers of 2005 and 2006, research cruises in mid to late summer were joined in 2008 and 2009 to test the prototype FRRF, developed with the collaboration of the Laboratoire d'Océanographie de Villefrance, France. Blooms were, however, less extensive than in previous years and had mostly disappeared before the cruises started. In situ data collection did therefore not include high biomass events. The gathered data contributed to a unique and growing dataset of optical properties of the Baltic Sea; nevertheless it was not sufficient to build new algorithms to estimate Chl-a, even though algorithms for Kd proved highly reliable.

The sensitivity of the prototype FRRF and its optimal optical configuration was explored under laboratory conditions, lacking sufficient in situ observations. This coincided with the launch of a European-wide effort to improve technology in support of automated measurements of primary productivity in European seas, as expressed by the Seventh Framework Programme 'PROTOOL' project. As a result, better timed research cruises could be planned for the years 2010 to 2012. The FRRF was further developed, optimised for both algae and cyanobacteria, and then adopted in this larger framework, resulting in the first commercial prototypes produced in 2010 by 'Photon Systems Instruments', Drasov, Czech Republic, which broadly followed the specifications laid out in PHY2COAST. During our research cruise in the summer of 2010, at the very end of the project, the fluorometric method was extensively tested with six different FRRF setups and a large contribution to the optical dataset of the Baltic Sea during cyanobacteria bloom could finally be made. The work on algorithm improvement using this dataset would, amongst other activities, be continued as part of various European Union and national research projects.

PHY2COAST advanced our ability to map photosynthetic parameters in water bodies with frequent cyanobacteria blooms, even though proper merging of in situ and satellite data was still a subject for future work. Increased attention to mapping primary productivity in areas affected by phytoplankton bloom sparked involvement in new research projects and resulted in dedicated, better timed, research cruises from a tight budget of research capacity at sea. These, in turn, strengthened cooperation of research groups around the Baltic Sea and would continue to do so beyond the project lifetime. We could thus expect considerable further research achievements in the direction of PHY2COAST.