engleski

Trophic state assessment of NE Adriatic Sea coastal waters based on water quality parameters

The aim of the present study was to assess water quality of the coastal waters in Rijeka Bay (NE Adriatic Sea) using a composite trophic index (TRIX) that takes into account oceanographic parameters, nutrient concentrations and chlorophyll a as an indicator of phytoplankton biomass. Despite the defined eutrophic status of the investigated area as mesotrophic with the exception of the eutrophic harbor site, high surface DIN/TP ratio at all investigated stations (>16) generally indicated potential P-limitation of phytoplankton growth, while occasionally, nutrient concentrations were balanced. However, at the Secchi depth and at the bottom of all investigated stations, DIN/TP ratio was near the Redfield’s ratio (16) during whole investigated period, indicating unhindered and nutrient balanced phytoplankton growth. Bioassay results with higher biomass of Phaeodactylum tricornutum in water samples from the harbour site and a lower biomass in all other water samples coincided with the trophic state based on nutrients and the TRIX index. In controlling of the actual variation of trophic state it was observed that nutrients were not utilized to their maximum potential.

Adriatic Sea; nutrient limitation; TRIX; eutrophication; bioassay; Phaeodactylum tricornutum

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