Monitoring Water Quality and Assessment of Land-Based Nutrient Loadings and Cycling in Kavala Gulf

The results of a systematic and intensive nutrient monitoring program are reported, which took place during the period 1997–1999 in Kavala Gulf, Northern Greece, having as a general task to study the impact of the various human activities on the nutrient loadings and cycling of the aquatic environment. A nutrient budget box model was used to estimate the annual capacity of Kavala Gulf to store and transform dissolved inorganic nitrogen and phosphorus, aiming at understanding the biogeochemical processes taking place in the area of interest. Point sources of nutrients from two municipal wastewater treatment plants (Kavala and Palio Seawage Treatment Works) and a phosphoric fertilizer producing industrial facility (PFP), as well as non-point sources from agricultural activities, seem responsible for the increased concentrations of dissolved inorganic nitrogen and phosphorus. Seasonal N:P-ratios suggest that nitrogen is the limiting nutrient during the summer, autumn and winter and phosphorus during the spring. The annual nutrient budget model revealed that Kavala Gulf is presently slightly autotrophic with nitrogen fixation exceeding denitrification.