Geoscience Reference
In-Depth Information
Chapter 18
Sources, Dynamics and Management
of Phosphorus in a Southern Baltic Estuary
Gerald Schernewski, Thomas Neumann, and Horst Behrendt
Abstract
Today, phosphorus is regarded as the key nutrient for Baltic Sea eutroph-
ication management. Major sources are large rivers like the Oder, Vistula and
Daugava in the southern Baltic region. Before entering the Baltic Sea, these rivers
discharge their nutrient load into coastal estuaries, bays and lagoons. The quanti-
tative role of these coastal waters, with restricted water exchange, for Baltic Sea
management is very important, but not well known. Taking the Oder/Odra estuary
as an example, we analyse the long-term pollution history and the major sources
for phosphorus and calculate a phosphorus budget, with special focus on anoxic
phosphorus release from sediments. The budget shows that due to internal eutrophi-
cation in July 2000 the lagoon became a major temporary source of phosphorus for
the Baltic Sea. A phosphorus emission reduction scenario, taking into account dif-
fuse and point sources in the entire Oder/Odra river basin, is presented. Phosphorus
load reductions have only limited effect on the eutrophic state of the lagoon. The
lagoon is more sensitive to nitrogen load reductions. Therefore, both elements have
to be taken into account in measures to reduce eutrophication.
Keywords
Szczecin lagoon
·
Hypoxia
·
Eutrophication
·
Water quality
·
Nutrient
loads
·
Sediment
18.1 Background and Objectives
The Baltic Sea is one of the world's largest brackish water bodies (412,000 km
2
)
with a water residence time of about 25-30 years, a drainage basin of 1,734,000 km
2
and a population in the drainage basin of about 85 millions. According to the Baltic
