International Journal of Marine Science, 2017, Vol.7, No.8, 67-75
72
c
c
Figure 8 Biomass in terms of displacement volume (ml/m
3
) in the North West Arabian Gulf during July 2009 and March 2010
Figure 9 Biomass in terms of standing crop (mg C/m
3
) in the North West Arabian Gulf during July 2009 and March 2010
3 Discussion
Zooplankton plays vital roles in energy and matter transfer through the system. Despite their importance,
understanding of zooplankton biodiversity is limited because of their fragile nature, small body size, and the large
number of species from various taxonomic phyla.
The zooplankton distribution varies both spatially and
temporally according to the environmental conditions prevailing in the region. Differences may also arise due to
the nature of distribution of the plankton, namely patchiness which may 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; in general the crop of a small apertures nets more than larger aperture nets (Ajeel,
1990).
The results showed that the Crustacean constituted a large proportion of zooplankton in the study area, which
comprised (82.8%, 95.3%, 69.7%, 85.3%, 94.5%, 19.3% and 88.0%) of the total zooplankton in seven stations
respectively. This is consistent with the study of Salman et al. (1990) in Khour Abdullah, who found that the
crustaceans comprised 88 % of the total zooplankton, and the study of Ajeel (1990) in Khour Al-Zubair port and
Umm Qasr port and Khour Abdullah, who found that the crustaceans constituted about 97.9%, 90.7% and 94.1%,
respectively. However Al-Zubaidi (1998) found that the crustaceans constituted about 88.4% in the Northwest
Arabian Gulf, while Ajeel (2004) stated that the proportion of crustaceans amounted to 85.4% in Shatt Al -Basrah
and 92.1% and 99.5% in the Khour Al-Zubair ports and Umm Qasr ports respectively. Whereas 62.9% in Shatt
Al-Basrah and 83.7% in Khour Al-Zubair (Ajeel, 2012).
The present results indicate that there were great differences in the abundance of zooplankton among the seven
stations sampled. Moreover, at first three stations (Shatt Al-Arab estuary) are the richest among all in zooplankton
abundance. That’s agreement with Al-Zubaidy and Salman (2001). Similarly the highest zooplankton biomass
