The Baltic Sea is particularly sensitive to nutrient input and
eutrophication because of its large catchment area associated with
human activities and due to the small water body characterised by
its distinct topography. Furthermore the single narrow outlet to
the North Sea results in a limited exchange of sea water. Consequently,
the high human induced nutrient loads and the long residence
time of water lead to N accumulation and, thus, cause
typical eutrophication effects (HELCOM, 2009a). This feature is further
enhanced through the pronounced vertical stratification of
water bodies typical for the Baltic Sea which hinders or prevents
ventilation and oxygenation of the bottom waters and sediments
(HELCOM, 2009a). The resulting oxygen depletion has an effect
on nutrient transformations, such as nitrification and denitrification
processes, as well as on the capacity of sediments to adsorb
phosphorus (Kemp et al., 2009). Overall, however, eutrophication
levels vary within the Baltic Sea due to its dynamic nature and differences
between areas or basins regarding their sensitivity to
nutrient overload. Consequently, management actions need to be
based on comprehensive and detailed assessment defining the
eutrophication status of the Baltic Sea and its protected areas.
However, data compilation on vast areas as the Baltic Sea or its
protected area network is somewhat problematic and associated
with extensive time effort and expenses.
The paper at hand aims at introducing a methodology to describe
the eutrophication status of the BSPA network by use of
available data: (1) a map on the eutrophication status of the Baltic
Sea produced by the Helsinki Commission (HELCOM) applying
HEAT (HELCOM Eutrophication Assessment Tool), and (2) modelled
raster data on total atmospheric N deposition made available
by EMEP (European Monitoring and Evaluation Programme).