SEASONAL DYNAMICS OF THE PHYTOPLANKTON COMMUNITY IN THE GANDIA COASTAL AREA,

Seasonal variability in the phytoplankton community of the coastal area of Gandia in the south of the Gulf of Valencia (Western Mediterranean Sea) was exam-ined in relation to physical and chemical surface water variables (i.e. salinity, nutrients, dissolved oxygen and temperature). This small area presents most of the point and non-point nutrients inputs that affect coastal areas as wastewater discharges through submarine outfall, river discharges and groundwater discharges from a detritic aquifer. Furthermore, surface channels that drain the Safor wetland, which is used mainly for agricultural crops, outflow into the confined har-bour. The main objective of the study was to observe the variations in phytoplankton groups as a response to environmental variables during different seasons and understand which species could be used as indicators of anthropogenic pressure. For this purpose, the taxonomic composition of the micro-phytoplankton communities at 32 fixed stations was determined in four sampling campaigns from summer 2010 to spring 2011. The results indicate that nutrient inputs mainly from the Serpis river and channels that drain the Safor Wetland determine the composition and abundance of the phytoplankton community, and that several key environmental factors such as water temperature, radiation, nutrients, and the molar ratios of nutrients influence seasonal phytoplankton assemblages. However, the discharge of effluent from a sewage treatment plant through the submarine outfall did not appear to have a significant impact on the phytoplankton community. The phytoplankton community comprised two main groups: diatoms and dinoflagellates and a total of 108 taxa were identified. The diatom population primaril