engleski

Distribution of phytoplankton, organic matter and trace metals in the Krka river estuary

The estuary of the karstic Krka River is a salt- wedge, highly stratified estuary located in the central part of the eastern Adriatic coast. Previous investigations showed that during most of the year the sharp vertical salinity gradient (halocline) divides the water column into two distinct parts: upper freshwater layer and lower marine layer. Freshwater phytoplankton decomposition represents the main source of biogenic organic matter which accumulates at the interface between fresh- and brackish water. Accumulation of organic carbon at the interface is encompassed by accumulation of nutrients and trace metals. Sampling was conducted during April and June 2010, at four stations along the estuary. Vertical distribution of salinity, temperature, oxygen and chlorophyll a fluorescence was obtained using a conductivity, temperature and depth (CTD) profiler. Sampling was performed using 5L Niskin sampler at various depths, according to the vertical salinity and chlorophyll a fluorescence profiles obtained previously with CTD profiler. Qualitative and quantitative phytoplankton composition was determined by light inverted microscope and phytoplankton pigment analysis by high performance liquid chromatography (HPLC). Dissolved and particulate organic carbon analyses were performed by high temperature catalytic oxidation (HTCO) method. Trace metal concentrations were determined by anodic/cathodic stripping voltammetry on static mercury drop electrode using standard addition method. Data will be presented showing the extent to which biomass of different phytoplankton groups correlates with distribution of organic matter size fractions and trace metals.

phytoplankton ; organic matter ; trace metals ; estuary

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