In t h~s study we estimated the amount and fate of phytoplankton primary product~on in the coastal zone of the Gulf of Gdansk, Poland, an area exposed to nutnent enrichment from the Vistuld R~v e r and nearby inunlcipal agglomeration The ~n v e s t i g a t~o n s were carned out at 2 sites d u r~n g 5 months in 1993 (February, April, May, August and October). A prolonged bloom pei-iod occurred in the coastal zone, as compared to the open Gulf and the open sea waters. From Aprll until October most values of gross primary production in the near-surface layer were in the range 100 to 500 m g C m-'' d 1 Phytoplankton net exudate release constituted on average 5 % of the gross prlmai-y production, total exudate release was estimated to be about 2 times h~gher. Bacterial production in the growth season was relatively low (the mean value l y~n g between 5 and 9 % of gloss primary production), nevertheless, the microbial community (bactena and protozoans) u t~l~z e d a large proportion of primary production (from about 50% in April and May to 16'%, in October). Usually direct protozoan grazing on phytoplankton exceeded bacterial uptake of the phytoplankton exudates. In winter, summer and autumn communlty respiration exceeded depth-averaged primary production, ~n d~c a t i n g that external energy sources ( s e d~m e n t resuspension, allochthonous organic matter) play a substantial role in communlty metabol~sm.

Sea Fi.sheriei. fumrute Gdymi;, !.',iJ..md The paper presents results of long•term investigations on primary production and chlorophyll a concentrations at two stationsin. the Southern Baltic (in the Gdansk Deep and il"' the Bomholm Deep). The data show increasing trends in the anrcual primary production and mean chlorophyll a contents. A mean increase in the annual primary production within the recent years is estimated at 1-2% per year.

Sell Fisheries hmti!te Gd}'llia. Pol.!md The paper presents data on primary production and chloro phyll a concentrations at two stations located in the Gulf of Gdaiisk (Baltic Sea). The primary production in 1987 was much higher than the mean values for the region, observed in other years when the production was 125-200 g C/m 2 a. Our observations show the primary production in the Puck Bay to be approximately two times that in offshore waters of the Gdaiisk Deep. The chloro phyll contents decrease along the Vistula estuary-Gdaiisk Deep transect.

The paper presents data on Secchi depth in the Southern Baltic waters. The mean annual Secchi depth is 8.2 m in the Gdansk Deep, 9.6 m in the Bomholm Deep, 9.9 m in the southern part of the Gotland Deep, and 5.7 m in the Gulf of Gdansk. The Secchi depth is subject to seasonal fluctuations, their amplitude being approximately 35% of the mean annual value. A trigono• metric polynomial was applied to describe periodic intra-annual changes of Secchi depth in the Baltic. The largest water trans parency was observed in winter, the transparency being lowest in summer. Effects of chlorophyll a concentrations on water transparency are presented in a graphic form.