International Journal of Marine Science, 2017, Vol.7, No.8, 67-75
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estimations were occurred at the second station (Ras-Al-Bisha) and first station (Al-Faw) more than other stations
during July 2009 and March 2010 respectively, this may be due to changing environmental conditions especially
salinity concentration. According to Day et al. (1989) the temperature and salinity have been identified as
important factors regulating zooplankton abundance in estuaries. As well as the effect of nutrients from Shatt
Al-Arab to the Arabian Gulf.
Figure 10
The average value of zooplankton biomass in term of wet weight and dry weight at Shatt Al-Arab estuary, Khour Abdulla
and Umm Qaser during study period
Figure 11 The average value of zooplankton biomass in term of displacement volume and standing crop at Shatt Al-Arab estuary,
Khour Abdulla and Umm Qaser during study period
Also it is obvious that the average highest density of zooplankton (16518 ind./m
3
) is recorded at station 2 (Ras
Al-Bisha) and the lowest density (3997 ind./m
3
) is recorded at station 5 (Bouy 13). Several researchers in other
estuaries elsewhere exhibited a similar pattern of zooplankton abundance (Pace et al., 1992; Laprise and Dodson,
1994). Moreover the Shatt Al-Arab estuary represents a calm environment (Albadran et al., 1995). Therefore,
higher salinities which have reduced current velocities and increase transparencies at this part of the estuary may
have resulted in increasing retention time, phytoplankton and high zooplankton abundance observed (Bakker,
1994; Bakker and Rijswijk, 1994).
A comparison of the results of the present study with those of previous studies in different regions may be
meaningful because of the different mesh sizes of nets used in the collection of samples (Table 3). While Table 4
shows a comparison of the biomass of zooplankton in the Garmat Ali River, Shatt Al-Arab River, Shatt Al-Arab
estuary, Khour Al-Zubair, Khour Abdullah and Arabian Gulf. The highest value of biomass was 3.461 ml/m
3
and
recorded in Khour Al-Zubair in February 1990, while the lowest value was 0.001 ml/m
3
and reported in the Shatt
Al-Arab in June 1996. The results show the average biomass of the zooplankton was high in the Shatt Al-Arab
estuary at (St. 1, 2 and 3) and lower in the St. 7 (Umm Qaser), these differences are likely locality variations.
