This may be explained by the general inability of ciliates to feed on Eutreptiella. Ciliates mainly feed on nanosized prey, preferably nanoflagellates ( Paranjape, 1990 and Sherr and Sherr, 1994). Euglenoids are generally considered PARP inhibitor to be poor food items for zooplankton because their reserve product, paramylon, is rarely digestible for the grazers ( Walne and Kivic, 1990). Although the cells may have been grazed by zooplankton, the paramylon grains passed undigested through the gut, thus diminishing the nutritional gain.

Also, increases in jellyfish numbers have been observed, and this may be the result of planktonic food available in greater abundance ( Mills, 2001). Different species dominated in any season, indicating wide variability in species composition over

time. Diatoms were found to be dominant during winter and autumn, which could be due to the fact that diatoms can tolerate the widely changing hydrographical conditions (Sushanth and Rajashekhar, 2012). Asterionellopsis glacialis Selleckchem Target Selective Inhibitor Library and Skeletonema costatum were dominant during winter 2012 and the latter species formed >90% of the total abundance during autumn. These two dominant species appear to be confined to coastal Egyptian waters ( Gharib et al., 2011 and Gharib, 2006). The occurrence of Skeletonema costatum is as an indicator of eutrophication ( Moncheva et al., 2001). The dominance of any species in the polluted water may be considered as an indicator species ( Dorgham et al., 1987). During winter 2013, diatoms abundance was nearly similar to that of dinoflagellates. Dinoflagellates are better adapted to the oceanic environment, while diatoms are more adapted to coastal environments

( Peña and ADP ribosylation factor Pinilla, 2002). The presence of variation in the seasonally cell abundances of these two groups suggests that environmental conditions in Western Harbour change during the year in response to variations in several physicochemical parameters. Gyrodinium sp. was largely responsible for the notable increase in dinoflagellate abundance during summer. Jeong et al. (2011) found that Gyrodinium sp. has considerable potential grazing impact on the populations of the euglenophyte Eutreptiella, and this explains the blooming of Gyrodinium during summer after overwhelming of Eutreptiella. Total phytoplankton richness (157 species) and diversity values (0.02–3.03) registered in the study area were higher than ranges previously reported (Gharib and Dorgham, 2006 and Zaghloul, 1994), in spite of the seasonal sampling during the present study against monthly one in the previous study, with approximately complete replacement of the dominant species. The leader species were: Cyclotella meneghiniana, Pseudonitzschia delicatissima, Prorocentrum cordatum and P.