The trophic state and the quality of the waters were determined
by means of various indices: Carlson’s (1977) Trophic State Index
(TSI) for fresh waters, the Trophic Index (TRIX) proposed by Vollenweider
et al. (1998) for coastal waters, and the set of criteria
adopted by the European Environmental Agency (EEA, 2001) for
freshwater, marine and transitional environments