Biogeochemical regime (Task 2.2)

In this task, the available information regarding the ecology of the system, the biogeochemical fluxes (including riverine inputs) and the trophic status has been compiled.

 Background and Rationale

In the shallow coastal zone within the vicinity of major Black Sea rivers, a substantial supply of nutrients encourages the growth of phytoplankton blooms, especially during or after flooding, sometimes on such a massive scale that grazers cannot cope with the results. In the central Black Sea , mesotrophic conditions and larger zooplankton stocks result in clearly eutrophicated, but more balanced conditions. However, substantial deviations, as reflected in the predominance of the gelatinous predator Mnemiopsis (introduced by ballast water from North America ), have resulted in the collapse of the previous food web in the Black Sea .

In the northern Aegean Sea though there is localised eutrophication due either to natural conditions or to anthropogenic action (outflow through the Dardanelles, and/or rivers), the pelagic ecosystem can still cope with the increase in suspended biomass and “blue water” scenarios still predominate. The southern Aegean is oligotrophic and the eastern Mediterranean Sea is ultra-oligotrophic.

Existing information on nutrients, suspended biomass (POC/PON, pigments), phytoplankton and zooplankton and pelagic fish data from the two seas from regional and EU investigations will be reviewed.

The target of this task is to compile the available information regarding the trophic status and identify the changes that have taken place during recent decades along the world’s most extensive trophic gradient.

Task leader

Anastasios Tselepides email ttse@her.hcmr.gr

Participants