Salinity dynamics in the Baltic Sea linked to anthropogenic foraging behavior during the Holocene: S03-03

S03-03 Salinity dynamics in the Baltic Sea linked to anthropogenic foraging behavior during the Holocene

Nils-Olof Svensson¹

¹ Department of Science and Mathematics, Kristianstad University, 291 88 Kristianstad, Sweden

Email: [email protected]

 

Former Lake Vesan is situated in the province of Blekinge in South Sweden. Before drainage and cultivation in 1927 forming a shallow lake surrounded by Phragmites reeds and connected to the Baltic Sea through a c. 3 km long outlet river.

This region has a well studied sea-level history showing that here global sea-level change since the last glacial is surprisingly well balanced by the glacioisostatic uplift. The result is that the studied basin for the last 10 000 years repeatedly shifted between being a lake or a bay of the Baltic. For most of this time it´s shores were important for fishing and hunting as well as for dwelling places. Later also activities like farming and burials left their traces.

In this archeologically unusually rich environment it was decided to build a highway initiating extensive archaeological and paleoecological studies of which this study is a part.

In the project my role is to study a more than 5 m long sediment core for microfossils and physical parameters to reveal the environmental history of the basin and its surroundings. Pollen and algae are the primary subjects here and analysis is still ongoing. Diatoms give information both on nutrient levels and salinity in the water, important both for revealing local sea-level history and productivity. This information may allow discussing changes in abundance and species composition of the limnic and marine fauna foraged by man. The sediments from early Holocene are unfortunately missing due to a hiatus. This is related to the wave action during the early part of the transgressive Ancylus stage. The younger sediments shows initially rather low but gradually increasing organic content, interpreted as low organic production during later part of the Ancylus Lake stage, and then increasing productivity as salinity in the Baltic increased due to the sea level rise in the areas of the Baltic Sea inlets.

Further up in the sediments a color change and increase in organic content coincides with major changes in the algae flora, the green algae Pediastrum decreases at the same time as dinoflagellate resting spores becomes frequent. The diatom flora also changes distinctly, indicating higher salinity. The horizon is radiocarbon dated to 5900 BC (7900 BP) and coincides in time rather well with the shift to the fully marine part of the Littorina Sea stage.