Daniela Cristina Ibănescu, Adina Popescu, V. Cristea

This study aimed at establishing the water quality of the fish farm Malina, Galati County through environmental and diversity indices of phytoplankton communities. The ecological indices and the estimation of diversity are important tools in the assessment of any ecosystem health. A healthy ecosystem is an ecosystem "stable and sustainable" meaning that it maintains its organization and autonomy over the years. In order to assess the structure of phytoplankton have been used different ecological indices (the abundance, the constancy, the dominance, the ecological significance), and the analysis of diversity was done by calculating indices such as Shannon - Wiener (H'), Shannon equitability index (E = HR). Simpson diversity index (1-D), Simpson equitability index (E1/D). Also, the algal pollution index (API) was calculated to determine if the ecosystem has a high organic load. The research on phytoplankton taxonomic structure led to the establishment of aquatic ecosystem studied, which is the identification of 28 species belonging to five taxonomic groups: Cyanophyceaea (0.07%), Euglenophyceae (29.789%), Bacillarophyceae (1.04), Chlorophyceae (68.63%), Zymnematophyceae (0.48%). The eudominante species belong to the Clorophyceae and Euglenophyceae genus. The Shannon - Wiener index (H') value was calculated at 1.78 and Shannon equitability at 0.71. The Simpson's diversity index value is 0.77 and 0.79 for the Simpson equitability. The value obtained for algal pollution index was API = 11. The results indicate that the studied aquatic ecosystem presents good environmental status, optimal for increasing the carp and asian cyprinids.

Key words: phytoplankton, ecological indices, diversity indices, eudominate species