Turnover of particulate matter in a Baltic estuary

The turnover of particulate material in Gårdsfjärden, a semi-enclosed, non-tidal estuary of the Baltic Sea, was studied during 1 year. Large temporal variation characterized the particle dynamics. The estuary had a stable stratification during most of the year, being mainly controlled by temperature. Under stratified conditions, inflowing particulate material of fluvial origin was largely transported straight through the estuary to the sea. At the spring and autumn turnover of the water column, there was a net erosion of the surface sediment due to re-suspension. Barotropbically forced seawater intrusions destabilized the stratification on a few occasions in the summer, and probably more often in the winter, causing increased retention of suspended particulate matter in the summer, and increased re-suspension and erosion of the surface sediment in the winter. The morphology of the basin, the bi-annual turnover of the water column and irregular seawater intrusions were the three most important factors governing the turnover of particulate material in Gårdsfjärden.