SS3.10 Ecological Implications of Terrestrial Inputs into Lakes and Ponds
Date: Tuesday, June 11, 2002
Time: 4:15:00 PM
Location: Esquimalt
 
VaalgamaaS, Department of Geography, University of Helsinki, Helsinki, Finland, sanna.vaalgamaa@helsinki.fi
 
THE EUTROPHICATION HISTORY OF LAAJALAHTI BAY, HELSINKI CITY, AS REFLECTED BY SEDIMENT GEOCHEMISTRY
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A radiometrically dated sediment core was analyzed to determine how different activities in the urbanized watershed and sediment-water processes are reflected in the sediment geochemistry. Despite the possible post-depositional changes there are definite signs of eutrophication in Laajalahti Bay's sediment record. The eutrophication started in beginning of past century and the nutrient loading received by the bay peaked already in the 1950's - 20 years before the beginning of regular coastal monitoring programs. Although the nutrient input to Laajalahti Bay has decreased significantly during the last decades, the water quality of the bay is still classified as as poor or fair due to internal loading of nutrients from the sediments. Furthermore, five phases of development with special characteristics and processes were identified in the sediment record by using principal components analysis (PCA) and cluster analysis.