FluorMed-1: Phytoplankton fluorescence studies in Mediterranean. Part 1. Feasibility and comparability of different methods in oligotrophic seas

User group PI: Jukka Seppälä, Finnish Environment Institute (SYKE), Finland

Hosting infrastructures: HCMR Heraklion Coastal Buoy & Poseidon Calibration Lab, Greece

Main Objectives

The FluorMed-1 project aims in providing information on the applicability and comparability of various fluorescence detection methods for phytoplankton community structure at a high frequency in the oligotrophic conditions of the Mediterranean waters. Those methods are used in contemporary online phytoplankton diversity and physiology research on various platforms (buoys, bench with pumped water, ships of opportunity, scientific vessels) and are mostly tested in eutrophied sea areas, where diversity and biomass are important. Since bulk or specific fluorescence sensors are not well defined in terms of detection limits but that they are depicted as required when selecting technology for monitoring the biological state of marine areas, it is important to define the possible applications in the oligotrophic conditions, and when developing the methodology further.

The validation and combination between bulk and physiology analysis in oligotrophic areas will be coupled with single cell analysis using high frequency pulse shape recording flow cytometry. This project will enable to go insight the picoplankton community functioning, dominating oligotrophic areas.

The techniques to be tested:

  • Applicability of new low-priced and miniaturized Chlorophyll a fluorometer for oligotrophic conditions
  • Phycoerythrin fluorescence as proxy for picocyanobacteria abundance
  • Spectral fluorescence and subsequent multivariate analysis of spectra to detect spectral components and their relation to taxonomic groups
  • Variable fluorescence as a proxy for phytoplankton productivity
  • Absolute counting, single cell scatter and fluorescence properties of full phytoplankton populations

Main objectives of our project are

  1. to determine limits of detection and quantification and sensitivity of LED fluorometers technique, for the conditions at the oligotrophic Aegean Sea, as well as detecting the effects of background signal on various fluorometric measurements. This will guide the technology selection in the oligotrophic areas.
  2. to compare how the group specific growth rates (determined with flowcytometry) are related to photophysiological characteristics of natural populations (measured with Frrf ). This combination of automated methods may provide more detailed insight on proxies of trait-based phytoplankton productivity and open possibilities to study their importance on carbon fluxes.
  3. to test longterm deployment of some fluorescence sensors and analyse the nonphotosynthetic fluorescence quenching patterns, which may improve the end-use of data.