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 c
ontributing to the majority of silica enrichment are Cyclotella sp. an
d Synedra acus. Their sedimentation rate in the brackish and in marine
layers is estimated.