engleski

ECOLOGICAL QUALIFICATION OF ISLAND VIS COASTAL WATERS ACCORDING TO THE TROPHICAL TRIX INDEX

The eutrophication of coastal waters is considered to be one of the greatest threats to the health of marine ecosystems. It is described as a change in the marine food web connected to the seawater enrichment by nutrients, which can modify the carbon pathways and excessive oxygen consumption [1]. Eutrophication can happen in natural mechanisms, but also in anthropogenic influences. Natural eutrophication happens because of the increase in biological resources in an ecosystems, which is a positive appearance. Anthropogenic eutrofication is caused by irregular outcome of urban waste waters that can affect negatively on the natural balance of the ecosystem. In this investigation trophic index (TRIX) has been used to assess the ecological status of the island Vis coastal waters. The trophic index TRIX was developed by Vollenweider in 1998 for the coastal area of Emilia-Romagna (northern Adriatic Sea), and was exploited by Italian legislation to characterize the trophic state of coastal waters [1]. The TRIX index is an logarithmic formula of four state variables, which are directly related to productivity: chlorophyll-a (Chl, µg/L), oxygen as the absolute percentage deviation from oxygen saturation (DO, %), and nutritious compounds such as dissolved inorganic nitrogen (DIN, µg/L) and total phosphorous (TP, µg/L). The sea water samples were collected for four seasons of 2015 year, at standard depths (5, 10, 20, 30, 50, 75, 100 m) using a Nensen sampler. Trix calculated value based on the data obtained at the investigation station, range from 1.76 to 3.23. According to obtained TRIX values (< 4) sea water at investigation station is generally oligotrophic. [1] E. Fiori et al., Nat. Hazards Earth Syst. Sci. doi:10.5194/nhess-2016-69, 2016.

eutrophication ; ecological state ; TRIX index

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