Changes in Copepod Community Structure in Response to Land-Based Activities along Alexandria Coastline, Mediterranean Sea

Abstract

Along the coastal water of Alexandria, Copepods were collected from four different areas subjected to agricultural/industrial mixed discharge, primary treated sewage flow, industrial effluent and agricultural runoff to trace the impact of land-based activities on their distribution patterns and community structure during high and low flow periods. Industrial discharge exerted the highest impact on the copepod population by decreasing its density to less than 500 ind./m3. Despite the decrease m copepod abundance during high flow of sewage, the impacted area sustained the maximum copepod density low discharge i.e. 11,222 ind./m3 due to presence of available food. The acceptable water quality characteristics and high nutritive nature of the agricultural runoff increased the copepod density and diversity. Euterpina acutifrons. Oithona nana and Paracalanus parvus showed high resistivity to pollution levels, blooming always near the discharge points. Harpacticoids showed high capacity to withstand industrial discharge more than Calanoids and Cyclopoids. Diversity indices for the area heavily affected by agricultural discharge (1.8 - 2.6) were higher than for the areas impacted by sewage (1.6 - 1.9), mixed agricultural/industrial (1.4 - 1.6) and industrial (0.6 - 0.8) discharge. Freshwater species were recorded at nearshore stations opposite agricultural runoff where salinity declined to < 10 psu. Multiple regression equations proved that the copepod community structure is influenced by various environmental factors which differed according to the water quality in the four investigated areas. While temperature and oxygen were not effectively involved in copepod community structure variations, pollution by Hg and oil seemed to suppress copepods abundance at areas impacted by industrial discharges.