International Journal of Marine Science 2016, Vol.6, No.58, 1-8
7
zooplankton density was observed in the third station more than the other stations, due to the increasing of the
Copepoda groups. Also the study results noted the more density of the zooplankton recorded during summer
(23607 and 23981 ind./m
3
) and less density recorded during winter (659 and 253 ind./m
3
) in the first station
(Al-Ashar) and second station (Abu Al-Khasib) respectively. While at the third station (Al-Faw) the high density
was recorded during winter (69223 ind./m
3
) and less density was recorded during autumn (3797 ind./m
3
). Also the
high density of zooplankton was observed in the last station during winter, spring and summer compared with the
other stations due to the increased concentration of salinity. However the concentration of salinity during autumn
was low so the zooplankton concentration was similar to the other stations.
Fig. 8 Percentage of important groups of zooplankton at stations 1, 2 and 3 in Shatt Al-Arab, sampled seasonally through 2013.
Zooplankton assume a great ecological significance in ecosystem as they play vital role in food web of the food chain,
nutrient recycling, and in transfer of organic matter from primary producers to secondary consumers like fishes
(Krishnamurthy et al., 1979).
The zooplankton distribution varied both spatially and temporally according to the environmental conditions
prevailing in the region. Differences might also arise due to the nature of distribution of the plankton, namely
patchiness which might be the cause of the great variations in the catches of the nets (Raymont, 1983). Moreover,
the mesh-size of the net is an important factor controlling the quality and quantity of the catch.
The present results indicate that there were great differences in the abundance of zooplankton among the three
stations sampled, due to the abundance of Cladocera, Cirripede larvae and Copepoda groups in stations 1, 2 and 3
respectively (Fig. 8). It was noted that the density of Cladocera was decreasing towards the south to the sea waters,
while intensity of Copepoda group was increasing. This is in agreement with the studies of Ajeel (1990) who
stated that the proportion of Copepoda reached to 58.94% in the port of Khour Al-Zubair, 83.97% in the port of
Um Qasr and 91.33% in Khour Abdullah of the total number of zooplankton, Al-Zubaidi and Salman (2001) and
Ajeel (2004) in Shatt Al-Arab, Shatt Al-Basrah and Khour Al-Zubair, also the study of Ajeel (2012) the Copepoda
which accounted for 44.7% in Shatt Al-Basrah and 66.9% in Khour Al-Zubair.
