engleski

Biological and physicochemical parameters reflecting rearing conditions in the fish farm in the central part of the Eastern Adriatic Sea

Phytoplankton are planktonic, photosynthetic microorganisms which grow in euphotic part of the oceans and seas. Their growth is connected to concentration of nutrients and other abiotic factors in the environment (temperature, salinity, oxygen concentration, organic matter, sea currents etc.). Although phytoplankton is at the base of trophic levels in aquatic environments, their overgrowth (phytoplankton blooms) can cause many problems in aquaculture environments, as well as economic losses. Hence, regular monitoring of fish farms is recommended to assess the potential eutrophication of such aquatic environment. In February 2017 and May 2018 sampling was conducted at one commercial fish farm of sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata) in the central part of the Eastern Adriatic Sea. Physico- chemical properties of the water column were measured in situ (Secchi depth, temperature, salinity, oxygen concentrations, pH and ORP). Phytoplankton samples were taken with Niskin sampler at 3 depths (0, 5m, 7, 5m and 18m) and sediment samples were collected by diver. Phytoplankton samples were analyzed quantitatively by Utermöhl method. Several parameters were determined for chemical analysis of sediment: pH and ORP, carbon, hydrogen, sulfur, inorganic matter and total phosphorus. Phytoplankton as biological parameter gave indication of water quality, with high percentage on nanophytoplankton versus microphytoplankton, showing tendency to oligotrophic status and good mixing of water column. Also, potentially toxic species were rarely identified and in low abundances. Results of physico-chemical properties confirmed stable abiotic conditions, with well oxygenized water column despite aquaculture production. Results of sediment analysis concur with good trophic status of the water in the sea bass fish farm.

phytoplankton ; aquaculture ; eutrophication

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