Monitoring Biodiversity of Picophytoplankton in Marine Waters (EU Project PICODIV)
Picoplankton (defined operationally as cells that pass through a 3 micron filter) dominate the photosynthetic biomass in many marine ecosystems, not only in the very oligotrophic regions of the world oceans, such as the Eastern Mediterranean Sea, but also in mesotrophic areas. However, picophytoplankton are clearly not exclusively restricted to pelagic environments. In many coastal regions, they are present throughout the year and constitute a 'background' population, onto which episodic phenomena such as the spring bloom develops. In some environments, such as coastal lagoons, picoplankton can be a major component of biomass and productivity for most of the year. In addition, some bloom-forming picoplankters such as Aureococcus spp. are toxic. However, to date fewer than 30 species of picophytoplankton have been described. A clear proof of our poor knowledge of picophytoplankton diversity is revealed by the discovery of three novel algal classes in the last ten years described from picophytoplanktonic taxa. The major objective of the european PICODIV project which has begun in April 2000 is to develop, test and validate probing methods based on molecular biology techniques that allow for routine and extensive assessment of picophytoplankton diversity (species composition and relative contribution of taxa to total community) in the marine environment. Our strategy to meet this objective is encapsulated in the following four steps:
- Obtain SSU rDNA sequences for as many as possible picophytoplankton taxa from both cultures and natural samples. Novel taxa will be assessed using a combination of methods including in particular pigment analysis and electron microscopy.
- Using this sequence database, develop hierarchical probes recognizing each taxonomic group having picophytoplanktonic representatives.
- Develop fast and efficient techniques to quantify the fraction of the pico-phytoplankton recognized by the probes in natural samples.
- Test and validate these probes on time series of picophytoplankton biodiversity in three coastal ecosystems.
More information about PICODIV can be found on the project homepage.
http://www.sb-roscoff.fr/Phyto/PICODIV/index.html.
Comparison of clone library diversity for eukaryotic picoplankton at the Helgoland time series site.
