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Trophic index (TRIX) at selected stations of Central and South Adriatic

As one of the indicators related to the marine ecosystem condition in the National list of indicators, trophic index (TRIX) is included [1]. The TRIX index is a logarithmic formula of four state variables, which are directly related to productivity: chlorophyll-a (Chl, mg/L), oxygen as the absolute percentage deviation from oxygen saturation (DO, %), and nutrient salts such as dissolved inorganic nitrogen (DIN, mg/L) and total phosphorous (TP, mg/L). The trophic index TRIX was developed by Vollenweider in 1998 for the coastal area of Emilia-Romagna (northern Adriatic Sea) [2] and it has been used in this research. Accordingly, sea water can be classified on a scale from 0 to 8, based on degree of eutrophication as: oligotrophic (0-4) ; mesotrophic (4-5) ; eutrophic (5-6) and extremely eutrophic (6-8). In this research trophic index (TRIX) has been used to assess the ecological status of coastal area of Southern and Central Adriatic. Data were obtained from two coastal stations (Dubrovnik-station A1 and Kaštela Bay-station A2) characterized by large loadings on the ecosystem (excessive of nutrient intake through wastewater, agriculture, industrial water etc.) and from another two coastal stations with less loadings on ecosystem (Podstrana-station A3 and Pelješac peninsula station A4). As reference stations, those located at the open sea (R1, R2 i R3). TRIX calculated value based on the data obtained at the research station, range from 2.80 to 3.60. According to obtained TRIX values (< 4) sea water at research station can be classified as oligotrophic.

TRIX index, oligotrophic, Southern and Central Adriatic

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