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Temporal Development Of The Distribution Of Inorganic Nutrients 
And The Oxygen Situation In The Pomeranian Bight During The Flood Event 
G.Nausch 1 , M.v.Weber 2 and A. Bachor 2 
1 Institut für Ostseeforschung 
Seestrasse 15 
18119 Rostock-Warnemünde 
2 Landesamt für Umwelt und Natur 
Badenstraße 18 
18439 Stralsund 
Abstract 
The nutrient situation in the Pomeranian Bight in August is normally characterized by very 
low concentrations near to the detection limit. Fist nutrient signals of the outflowing Oder 
water could be detected at the end of July. Maximum values were measured on July 31 st . 
Table 1 summarizes the highest measured nutrient concentrations in the Pomeranian Bight 
compared with maximal concentrations which were normally observed during winter/early 
spring time connected also to high riverine water discharge. The concentrations measured 
during the oder flood event are in the same order of magnitude. Exceptions are the large 
inputs of silicate due to ‘direct’ discharge of freshwater. In contrast to the winter/early spring 
situation where the high nutrient concentrations are only diluted by physical processes and 
transported directly into the open Baltic Sea, in summer time an active biological community 
transforms some of the inorganic nutrients into biomass. 
Table 1: Maximum nutrient concentrations (pmoL/1) during earlier monitoring cruises and 
during the Oder flood event (all mentioned station are near the Swina mouth) 
Station 
Nitrate 
Phosphate 
Silicate 
winter values 
1993/1996 
OB 4 
49.1 
1.98 
49.5 
28 July 1997 
010 
23.3 
2.76 
72.5 
31 July 1997 
010 
29.0 
2.70 
95.5 
04 August 1997 
001 
20.6 
2.56 
118.5 
12 August 1997 
OB 4 
8.6 
2.07 
91.6 
Using distribution patterns for the periods 29.-31. July, 3.-5. August and 11./12. August the 
spreading of the outflowing Oder water along the coast of Usedom could be observed (Fig. 
1). The most interesting observation was that silicate and to some extent also phosphate were 
mixed conservatively whereas the nitrate concentrations decreased very rapidly near to the 
outlet. This leads to the conclusion that the production in large areas of the Pomeranian 
Bight is nitrogen limited and the high silicate and phosphate concentrations can not used 
effectively (see also the contribution by C. Humborg). 
The outflowing Oder water formed a layer of around 5m thickness, overlaying denser water 
masses. This strong stratification prevailed due to the long lasting calm and warm weather 
and caused an extreme oxygen depletion and the presence of hydrogen sulphide from the 
August 17 th in large areas in front of the Usedom coast. An intense degradation of the benthic 
community in this area has to be expected with the death of many sessile evertebrates. A 
similar observation was already made in the Pomeranian Bight in summer 1994 as a result of 
a 3 week calm weather period. The stratification lasted until the beginning of September 
when strong winds mixed the water in the Pomeranian Bight down to the bottom. Nutrient