HELCOM Environmental Fact Sheet published

Recently, WP3 work conducted in SYKE has led to the publication of a HELCOM Environmental Fact Sheet, regarding the phytoplankton community composition in relation to the pelagic food web in the open northern Baltic sea.

The emerging key messages are:

  • Phytoplankton primary producers constitute the base of the Baltic Sea open sea food web. Based on Suikkanen et al. (2013), in the open Gulf of Finland, the Åland Sea, and the northern Baltic proper, the late summer phytoplankton composition has changed towards a more mixotrophic and potentially low-quality food for higher trophic levels. From the food web perspective, the healthiness of the phytoplankton community has decreased also due to the increase in biomass of certain HAB species. Based on Kuosa et al. (submitted), there are some indications of similar phytoplankton community changes also in the Gulf of Bothnia.
  • Indications of bottom-up effects of the phytoplankton community on higher trophic levels already exist, since small zooplankton such as rotifers have increased, and copepods have decreased.
  • Suikkanen et al. (2013) concluded that the pressures behind plankton community changes are most probably interactions between warming, eutrophication and increased top-down pressure due to overexploitation of resources, and the resulting trophic cascades.
  • The monitoring of phytoplankton species composition in addition to monitoring chlorophyll-a (chl-a) is essential, since summarizing parameters like chl-a, whether measured from water samples or using satellite imagery, do not provide information on community composition, i.e. on the healthiness of the community from the food web point of view.

The work is progressing to add more data sets and to develop this into a commonly agreed HELCOM biodiversity indicator.

More info at  http://www.helcom.fi/baltic-sea-trends/environment-fact-sheets/eutrophication/phytoplankton-community-composition