The Oder Estuary - IOW

3.4 Retention of nutrients within the Oder estuary
Based on model results the amounts of nitrogen and phosphorus retained in both parts of the
Lagoon were calculated for the entire period 1980-99. On average, about 22% of incoming nitrogen
was retained in the Grosses Haff, including 12% of denitrification, on annual basis. In case of
phosphorus 17% of the incoming load was retained there. In the Kleiness Haff 48 % of nitrogen
was retained, including 39 % of denitrified nitrogen, and 17 % of phosphorus. Mean annual budget
calculations from the model results for both parts of the Szczecin Lagoon area are given in
Table 3.4.
Table 3. 4. Budget of nitrogen and phosphorus based on model calculations – average annual
values for the 1980-99 period.
Grosses Haff Kleines Haff
Nitrogen
[tons N a -
1 ]
Phosphor
us [tons P
a -1 ]
Nitrogen
[tons N a -
1 ]
Phosphor
us [tons P
a -1 ]
Input 80,900 7,100 19,000 1,330
Output 64,200 5,900 10,500 1,100
Denitrification 8,800 --- 7,000 ---
Burial 7,900 1,200 1,500 230
3.4.1 Retention in the sediment
Different values of the amount of nitrogen and phosphorous accumulated in the sediment of the
Grosses Haff and Kleines Haff are given in literature. The soft bottom sediment area, where
accumulation takes place, covers about 56% (350 km 2 ) of the Lagoon area (LEIPE et al. 1998,
MEYER & LAMPE 1999). According to LEIPE et al. (1998) within this area 100,000 tons of nitrogen
and 30,000 tons of phosphorus were accumulated during last century in the surface layer of the 15
cm depth. MEYER & LAMPE (1999) calculated that annually about 1 mm of the sediment is
accumulated in the soft bottom deposits of the Lagoon on annual basis, which means accumulation
of about 0.74 g N m -2 a -1 and 0.11 P m -2 a -1 . These values recalculated for the entire 100 year period
would yield about 51,000 tons of nitrogen and 7,600 tons of phosphorus accumulated within a
10 cm layer of sediment. Table 3.5 presents data on the amount of nitrogen and phosphorus
accumulated in the sediment calculated on the basis of the model results, estimates from literature
and other modeling results given by HUMBORG et al. 2000.
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