International Journal of Marine Science, 2017, Vol.7, No.8, 67-75
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The added volume of water is equal to the displacement volume of the zooplankton. The volume of zooplankton
(ml/m
3
) was then obtained by dividing the volume of zooplankton by the volume of the samples filtered by the
net.
The standing crop of the zooplankton (mg C/m
3
) was calculated using the conversion factor of 65 mg C/ml of
displacement volume. (Jacob et al., 1979).
1.2.2 Wet weight and Dry weight
Fresh weight and dry weight of the zooplankton were estimated by filtering the sample through a wet filter paper
of a known weight using a vacuum pump and the wet weight was recorded by subtracting the weight of the wet
filter paper from the paper with the zooplankton. Then the paper was oven–dried at 60ºC for 24 hours and the dry
weight was recorded. The dry weight of the filter paper was subtracted from that of the paper with the sample and
the dry weight of the sample was obtained. Then the wet weight and dry weight were converted int o mg/m
3
by
dividing the weight of the sample by the volume of the sample filtered.
2 Results
2.1 Environmental factors
Water quality parameters varied according to seasonal norms. Temperature ranged from 20.4°C in March 2010 at
St. 7 (Umm Qaser Port) to 29.5°C in July 2009 at St. 5 (Khour Abdulla (Buoy 13), salinity from 5.87 psu in
March 2010 at St. 1 (Al-Faw) to 47 psu in July 2009 at St. 5 (Khour Abdulla (Buoy 13)) (Figure 2).
Figure 2 Water temperature and salinity in the study area during July 2009 and March 2010
2.2 Density of zooplankton
The density of zooplankton ranged between 185 ind./m
3
during March 2010 to 32856 ind./m
3
during July 2009 at
St. 3 (Al-Musab) (Figure 3). The average density of zooplankton was 12940 ind./m
3
in the study area during July
2009 and 5216 ind./m
3
during March 2010 (Table 1 and Table 2). Crustaceans were the dominant of the total
zooplankton in seven stations respectively (82.8%, 95.3%, 69.7%, 85.3%, 94.5%, 19.3% and 88.0%). Copepoda
constitute (76%) of the total zooplankton. The second important group was Bivalve (9%), then Rotifera (6%),
whereas Cirripede larvae and Appendicularia (2%) followed by the other zooplankton (5%) (Figure 4). Among
Copepoda, Calanoid was the dominant group in all stations (67%). Then Cyclopoida (15%), nauplii (12%),
Harpacticoida (4%), and Poecilostomatida (2%) of total Copepoda (Figure 5).
2.2.1 Station 1 (Al-Faw)
The density of zooplankton reached 16696 ind./m
3
in July 2009. It was found that the Copepoda (11827 ind./m
3
)
constituted about 70.8% of the total zooplankton, and the important species were
Acartia pacifica
(1119 ind./m
3
)
(6.7%) and Paracalanidae (4137 ind./m
3
) (24.8%). The second important group was Bivalve (3796 ind./m
3
)
(22.7%), then the Cirripede larvae (584 ind./m
3
) (3.5%) of the total zooplankton (Table 1).
