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Experimental studies in processes taking place in enclosures with mixed sea and Vistula River water

100%

Witek Z., Pastuszak M., Nakonieczny J., Ochocki S., Zalewski M., Maciejowska M., Gromisz S., Mackiewicz T., Wrzesinska-Kwiecien M.

Oceanological Studies

1997

vol. 26

issue 1

35-57

Biological and chemical processes occurring in seawater from the Gulf of Gdansk, 'enriched' with Vistula river water, were studied in a series of microcosm experiments covering different seasons of the year. Concentrations of inorganic forms of nitrogen were, with one exception, 25 - 800 times higher in the Vistula water than those in the sea; phosphates were from 3.5 to 70 times higher. Two phases were observed during the incubations: during the first there were marked increases in primary production, chlorophyll concentration and bacterial production, and a de-crease in nutrient concentrations. The second phase was characterised by a lack of phosphates, a gradual decrease in chlorophyll concentrations, and an increase in zooplankton abundance. During the growing season the first phase lasted only a few days, during which nitrates and silicates were taken up at a rate of 2-4 mmol?dm-3?d-1 and phosphates and ammonia at a rate of 0.05-0.3 mmol?dm-3?d-1. Further phytoplankton growth and further nutrient uptake were most frequently limited by phosphorus depletion. Phosphorus was probably also a factor limiting bacte-rioplankton growth, which appeared to be correlated with primary production. In spring and autumn phytoplankton growth was additionally limited due to grazing by protozooplankton and rotifers, in summer by nitrogen exhaustion.

The eutrophication model of the Vistula Lagoon

86%

Kwiatkowski J., Koch_Rasmussen E., Ezhova E., Chubarenko B.

Oceanological Studies

1997

vol. 26

issue 1

5-33

The Vistula Lagoon is a shallow coastal ecosystem located on the Polish-Russian border in the coastal area of the southern Baltic. It is strongly influenced by inflows of seawater from the Baltic as well as by river inflow from the catchment area. High concentrations of nutrients in the Lagoon cause high primary production rates (ca 190 gC/m2/year) and other processes related to eutrophi-cation. Mathematical modelling of the physical and biogeochemical processes in the Vistula Lagoon has been applied as a tool for environmental assessment. The integrated MIKE 21 two-dimensional modelling system (by the Danish Hydraulic Institute / Water Quality Institute) was applied in the study. The eutrophication model of the Vistula Lagoon describes the nutrient cycle including eutro-phication-related processes. This paper describes the setup and calibration of the eutrophication model and presents the results of the basic calculation reflecting the situation in 1994. The role of the model in the evaluation of the ecological situation and in water management and planning is discussed. The model has been calibrated against monitoring measurements carried out in the Polish and Russian parts of the Vistula Lagoon.

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2 Oceanological Studies

2 1997

1 Chubarenko B.

1 Ezhova E.

1 Gromisz S.

1 Koch_Rasmussen E.

1 Kwiatkowski J.

1 Maciejowska M.

1 Mackiewicz T.

1 Nakonieczny J.

1 Ochocki S.

1 Pastuszak M.

1 Witek Z.

1 Wrzesinska-Kwiecien M.

1 Zalewski M.

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Experimental studies in processes taking place in enclosures with mixed sea and Vistula River water

The eutrophication model of the Vistula Lagoon