Monitoring the Bio-optical State of the Baltic Sea Ecosystem with Remote Sensing and Autonomous In Situ Techniques - The Baltic Sea Basin - page 426

Fig. 20.11 Stacked contributions of the main optical component (CDOM, chl-a and inor-
ganic SPM) to the diffuse attenuation coefficient, K d (490), along a transect from the outlet of
Himmerfjärden sewage treatment plant to Landsort Deep, the deepest part of the Baltic Sea (459 m
depth). Note that K d (490) was corrected for the attenuation of water itself, K w (490). The black line
indicates the end of Himmerfjärden and the beginning of the open sea (after Kratzer and Tett 2009 )
surface mixed layer, stimulating primary production (Fig. 20.2 ) . From this point
of view it would be therefore desirable to further extend the breadth of the coastal
zone as defined in the WFD. As the northwestern Baltic Sea is characterized by
relatively low terrestrial runoff compared to, e.g., the southern Baltic Sea, coastal
waters extend even further offshore in the southern Baltic Sea. Chlorophyll is the
optical component that is most variable over the year as it is so dependent on the
nutrient status. However, both CDOM and TSM also have a strong seasonal cycle
governed by seasonal changes in precipitation and runoff. In coastal areas of the
Baltic Sea, there is also a significant contribution of inorganic SPM to the optical
signal, and it also increases the reflective signal from the water close to the coast.
Darecki et al. ( 2003 ) have also observed very large variability in reflectance in the
Southern Baltic, which may be related to relatively high sediment loads compared
to the northern Baltic Sea.
20.3.3 Synoptic Use of Remote Sensing and In Situ Techniques
Figure 20.12 shows the spatial distribution of TSM in the Baltic Sea on 23rd April
2008. The FUB/WeW 5 MERIS Water Processor was here applied to MERIS RR
data (Schroeder et al. 2007a , b ) . The panels illustrate qualitatively and quantitatively
5 FUB: Freie Universität Berlin, WeW: Institut für Weltraumwissenschaften (Institute for Space
Science).