Investigation of eutrophication risk in marine aquaculture area (Ordu, southern black sea, Türkiİye)

This study was conducted to determine the possible environmental impacts of fish farming facilities located in Vona Bay, Perşembe district of Ordu province on the Southern Black Sea coast. In order to examine the trophic structure and eutrophication risk of sea water, temperature, pH, dissolved oxygen, oxygen saturation, salinity, Secchi disk depth, ammonium nitrogen, nitrite nitrogen, nitrate nitrogen, total nitrogen, total phosphorus and chlorophyll-a parameters were analyzed in water samples taken from the surroundings of the cages and the reference point using standard methods. The analyses were carried out in May and August (2024), when primary production causing eutrophication was at its highest. The obtained data were compared with the "Black Sea coastal water eutrophication criteria" in the annex of the Surface Water Quality Regulation to determine the water quality class. The TRIX index (TI) in the "Regulation on Environmental Management of Fish Farms Operating in the Sea" was used to determine the eutrophication risk in Vona Bay. Trophic Index (TRIX) is a scale used in the classification of the trophic status (eutrophication) of coastal surface waters. In the calculation of this index, a logarithmic calculation method was used, which includes the parameters of total phosphorus (TP) and total inorganic nitrogen (TIN) from nutrients, chlorophyll-a (kl-a) as a quantitative indicator of phytoplanktonic biomass, and O2% (absolute oxygen percentage deviating from saturation level) as a photosynthetic intensity indicator. As a result of the calculations, the risk of eutrophication in Vona Bay, where aquaculture is carried out, is low (4≤TI≤5) and has good water quality. Existing facilities can continue aquaculture. It is important to carry out such monitoring studies to protect surface water resources and to minimize possible water quality problems and eutrophication risk in the coming years.