Estimation of Anisotropies in Chlorophyll A spatial distributions based on satellite data and variography by

Sea eutrophication is a natural process, however in many cases is considered one of
the major forms of water pollution affecting coastal areas, lakes and reservoirs all over
the world. Many methodologies have been developed for assessing eutrophication and
during the last decades, the contribution of remote sensing techniques has been proved
very useful in this research area. Satellite data from various sensors have been
processed and analysed by research groups all over the world for estimating chlorophyll
a concentrations and consequently, eutrophication conditions in the marine
environment. Further analysis of the spatial structure of the eutrophication phenomenon
that includes detection of the degree of homogeneity and of the directions of maximum /
minimum anisotropy is of great interest as well.
In this study, an attempt was carried out for estimating the anisotropy in chlorophyll a
spatial distributions produced by the process of satellite data. The North Aegean Sea
was used as the case study area and SeaWiFS monthly satellite data acquired for
February, May, July and September 2003 were analysed. As a result, four
eutrophication maps illustrating the eutrophication levels in the North Aegean Sea were
developed and further analysis of their spatial structure was carried out using
variograms. Semi- and surface variograms were developed and the directions of
minimum / maximum anisotropy as well as the degree of spatial correlation of the
eutrophication phenomenon were assessed.