BALTIC SEAENVIRONMENT PROCEEDINGS No. 59 - Helcom

had been a ten-fold reduction of concentrations achieved between
1970 and 1980. With regard to Hg and DDT, by 1979 environmental
protection measures seemed to be effective.
- Very little was known about other organic contaminants.
- Modelling the water exchange between the North Sea and the
Baltic was still undeveloped.
The Second Periodic Assessment for the period 1984-1988
The conclusions of the scientific material from the "Second
Periodic Assessment of the State of the Marine Environment of the
Baltic Sea'l(Baltic Marine Environment Protection Commission,
1990a,b), covers the period 1984 - 1988. Experts from all Baltic
States worked together in the "Ad _ hoc _ Group of Experts for the
Preparation of the Second Periodic Assessment" (GESPA). The main
topics were as follows:
* Hydrography
* Oxygen, hydrogen sulphide, alkalinity, pH
* Nutrients
* Pelagic biology
* Zoobenthos
* Baltic fish stocks
* Micro-organisms
* Trace elements
* Organic contaminants
The assessment dealt mainly with observations made in the open
sea. Consequently, the conclusions did not reflect findings in
coastal areas, which fall within the jurisdiction of each State.
However, an holistic assessment of the various coastal areas of
the Baltic Sea has for a long time been requested by the
Commission. Such an evaluation, based on national reports, is now
under way and will be finalized at the end of 1993.
Some general conclusions were drawn from the Second Periodic
Assessment:
- The strong increase of phosphorous and nitrogen, which was
observed in the 197Os, has ceased in many areas of the Baltic
Sea. However, this is not a proof that anthropogenic inputs do
not further increase but may only be an indication that
hydrographic conditions play an important role.
- There was evidence that phytoplankton primary production has
doubled within the last 25 years in the area from the Kattegat
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