engleski

Effect of salinity gradients on the distribution of phytoplankton pigments in a stratified estuary

Chlorophyll and carotenoid pigments were determined in the highly stratified Krka estuary to study the distribution of phytoplankton during a spring bloom. Both axial and vertical profiles of pigment concentrations revealed the dynamic nature of the phytoplankton in terms of quantity, community structure and physiological status in relation to the salinity gradients in the estuary. The maximum concentrations of chlorophyll a (Chl a) were determined in the brackish layer of the lower part of the estuary, which received additional inputs of nutrients via untreated sewage from the town of Šibenik, whereas the underlying saline layer contained significantly lower levels of Chl a. In fact, detailed depth profiles revealed that the maxima of both photosynthetic pigments (8.5 ľg/L Chl a) and their breakdown products (18 ľg/L phaeophorbide a) occurred at the upper part of the halocline. This indicated that the interface of the brackish water/seawater layers was very efficient in collecting living and detrital particles from the highly productive brackish water layer, thus playing an important role in determining the distribution and fate of organic matter in the estuary.

pigment biomarkers ; phytoplankton ; stratified estuary ; salinity gradients

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