Environmental factors and seasonal dynamics of Prorocentrum lima population in coastal waters of the Gulf of Tunis, South Mediterranean.

Abstract

In the frame of a phytoplankton study, a series of samples were collected in the Punic harbors of Carthage (Gulf of Tunis, South Mediterranean) from March 2008 to March 2010. Species composition, seasonal variations of pelagic Prorocentrum populations and several physico-chemical parameters were specified, as well as the relation between Prorocentrum species dynamics and water temperature, salinity and nutrient concentrations. The main detected species are included in the benthic/epiphytic group; P. lima (Ehrenberg) Stein 1878 and P. emarginatum Fukuyo 1981. P lima was the dominant species. The highest abundance of P. lima (6.97 x 10(3) Cells L(-1)) was recorded in August 2008 where temperature and salinity values ranged from 23.1 to 30.2 degrees C and 36.1 to 40.3 psu, respectively. The dynamics of the P. lima population had significant positive correlations with both temperature and salinity, and negative correlations with both nitrogen/phosphorus ratio and ammonium concentrations. Proliferations of this species represent a serious hazard for public health in Tunis northern coasts.