A re-assessment of TRIX for trophic status assessment of the North-Eastern coastal area of Turkey (Yomra area)

Since the ability to meet world demand for fish from natural fish stocks has reached its peak and now is declining, it is obvious that demand for fish in future can only be provided by aquaculture and should be increased every year. But this increase is causing some environmental impacts and creates the risk of eutrophication.This study is aiming at to determine Trix index through the concentrations of total phosphorus, total inorganic nitrogen, chlorophyll-a and % saturated oxygen in a full year to be calculated monthly basis at the one of the selected cage farm operating in the eastern Black Sea coast of Turkey. The index is used eutrophication status. The purpose of this study is to determine and assessment eutrophication risk based on TRIX İndex of cage farm which is located at the coast of Yomra, in Trabzon at Eastern Black Sea. During the study, the water samples were taken periodically from seven chosen stations in every month. The measured data were given as following (minimum, maximum and average): dissolved oxygen (6.254-10.640-8.830±0.057 mg/L), chlorophyll-a (0.001-2.630-0.601±0.028 µg/L), nitrate+nitrite nitrogen (NO3-+NO2-)-N (0.098-54.040- 7.264±0.426 µg/L), ammonium nitrogen (NH4+ -N) (0.420- 45.210- 10.909±0.508 µg/L), total phoshhate (0.100-63.496-5.006±0.503 µg/L) and TRIX İndex ( 0.258-4.516-2.702±0.049). TRIX İndex value showed a good degree of throphıc level. Obtaining smaller values than 4, which ic critical value, proved that most of the stations have oligotrophıc fresh water properties.