Transport of silica in a stratified estuary

The enrichment of dissolved silica found in the marine layer near the head of the highly stratified Krka estuary is attributed to sinking of freshwater diatoms through the halocline and subsequent decomposition of biogenic silica. In the marine layer, freshwater diatoms sink and order of magnitude slower than in the brackish layer. As a consequence their dissolution path is shorter. Freshwater phytoplankton species contributing to the majority of silica enrichment are Cyclotella sp. and Synedra acus. Their sedimentation rate in the brackish and in marine layers is estimated.