As in many coastal zones and harbours of the Mediterranean basin, two peaks (spring and autumn) in zooplankton abundance are usually observed (Vasilievich et al., 2003). Higher diversity in the zooplankton population recorded at stations 1 and 2 were related to the existence of fresh and brackish

water forms as the result of increased inflow of wastewater from Noubaria Canal. Analysis of the main environmental influences on zooplankton abundances showed that pH and dissolved oxygen were the most important parameters, which positively affected the variation of zooplankton. In contrast, salinity exercised negative effects with Protozoa. Temperature does not appear to directly correlate with total zooplankton abundance. The conditioning effect of temperature Selleckchem GSK1210151A on zooplankton groups is documented in large investigations (e.g. Marques et al., 2006). A total of 106 species NVP-BKM120 price were recorded in the present study, and this is slightly lower than the number recorded by Abdel-Aziz (2002) which amounted to 111 species. Except in spring, copepods were the most abundant group and their average

abundance value was >52% of total zooplankton and maximum value reached in autumn. The abundance of copepods steadily increased during winter and autumn with rising trend of salinity. Biodiversity of the copepod community was not adversely affected by the differences in the average nutrient load in the investigated area. Oithona nana emerged as the most successfully adapted copepod species at both seasonal and spatial scales because it has the ability to consume a much wider range of food than the other copepods ( Lampitt and Gamble, 1982), and it is very important in many neritic regions that are exposed to eutrophication ( Richard and Progesterone Jamet, 2001). The average abundances of this species ranked

first among adult copepods in winter (78.1%), spring (66.9%), summer (60.7%) and autumn (39.9%). Apart from Oithona nana, among the top 4 species throughout the investigated area were Oithona plumifera, Euterpina acutifrons and Paracalanus parvus. Oithona spp., Paracalanus parvus and Euterpina acutifrons are the most ubiquitous and abundant copepods in the coastal Mediterranean ( Gallienne and Robins, 2001). One of the characteristic features of the present observation was the relatively large occurrence of copepod nauplii (22.0% of the total zooplankton) which could be attributed to high density of older stage copepods ( Uye et al., 2000). Tintinnids had the highest species richness (29 spp.); meanwhile, they occupied the second order of abundance after copepods, forming 35.23% of the total count. Its predominance during spring could be due to their high reproductive capacity and euryhaline nature (Govindasamy and Kannan, 1991).