Research Article
Accumulation of Heavy Metals in Zooplanktons from Iraqi National Waters 
,
Talib A. Khalaf2 
,
Shaker G. Ajeel2 ,
Abdullah Y. Khudhair3 ,
Ramiz Saad4 2 Department of Marine Biology, Marine sciences center / University of Basrah, Iraq
3 Medicinal Branch/ College of Pharmacy, University of Basrah, Iraq
4 Maxxam analytical INC.6740 Campobello Rd. Mississauga, On L5N 2LB, Canada
Author Correspondence author
International Journal of Marine Science, 2018, Vol. 8, No. 3 doi: 10.5376/ijms.2018.08.0003
Received: 24 Nov., 2017 Accepted: 20 Dec., 2017 Published: 12 Jan., 2018
Al-Imarah F.J.M., Khalaf T.A., Ajeel S.G., Khudhair A.Y., and Saad R., 2018, Accumulation of heavy metals in zooplanktons from Iraqi National Waters, International Journal of Marine Science, 8(3): 25-34 (doi: 10.5376/ijms.2018.08.0003)
Samples of zooplankton's were collected by special net from 8 sites within Iraqi national waters represented by stations: 1- Shatt Al-Basrah cannal, 2- Khour Al-Zubair, 3- Buoy 29, 4-Buoy 13, 5-Buoy 5, 6-Al-Musab, 7- Ras Al-Bisha, and 8-Al-Fao. Samplings were conducted during the period June 2009 and Feb. 2010. Zooplankton's were classified in groups: Copepods, Rofifera, Cirriped larvea, and some other minor species. Major abundant zooplankton's were Copepods, Rotifera, Cirriped larvea, Polychates, and Bivalves, while other zooplankton's which appear in minor abundance were Appendicularea, Castropod, Forminilifora, and Megalopa. Selected heavy metals Cd, Co, Cu, Fe, Hg, Ni, Pb, U, and Zn were determined in the collected samples by adopting a highly sophisticated ICP/MS at Maxxan Analytical Inc., Canada. Levels estimated of heavy metals in µg/g were high for most of studied metals due to two main reasons: 1- the marine vessels sank in the water ways, and 2- discharging of waste water from Basrah City and certain industrial estate around. Trend of descanding concentrations of heavy metals accumulated in zooplankton's at southern Iraqi Waters were in the order: Fe> Zn> U > Cu > Co > Pb > Cd > Hg. Highest levels in µg/g for toxic heavy metals Co (1.91±6.62), Hg (0.40±1.100), Ni (15.52±40.15), Pb (1.013±2.030), and U (88.6±156.55), were reported at site 7 the Ras Al-Bishah station at the top of the Northern West Arabian Gulf due to waste discharge from the Iranian idustrial estate.
Background
The Marine and fresh water ecosystems are being threatened by the discharges of untreated sewage wastes and industrial effluents. This ultimately affects the sustainability of living resources and public health. The wastes carry an enormous level of toxicants, especially the heavy metals that have the tendency to accumulate into the basic food chain and move up through the higher tropic level. Also, the wastes have negative impacts on the marine and freshwater resources which cause economic loss by affecting the migration of many aquatic Creatures. As well as, anyone exposed to the waters which will cause the government to spend large amount of money to treat the polluted area (Robin et al., 2012). In aquatic system, the primary concentrator, the photosynthetic plants, take chemical elements from the surroundings, these plants are the phytoplankton's which has small size and offer large surface for adsorption. The accumulation of chemical elements by phytoplankton’s will pass to marine animals through the food webs of the water ways (Chipman, 1959). Phytoplankton is the major food producer in marine and estuarine ecology. In addition, zooplankton plays a fundamental role in food chains as secondary producers. It is considered to be major food sources for the marine mammals, birds and fishes (Percy, 1993; Nilsson et al., 1995a; Nilsson et al., 1995b). Thus, zooplankton organisms may contribute to the transfer of metals to the higher trophic levels and have been chosen among other as recommended organisms in baseline studies for marine environment (AMAP, 1995). There is a variety of significant human health and environmental associated issues with the geographically widespread prevalence of elevated levels of both organic and inorganic compounds in freshwater and marine biota. A linkage is evident between the bioaccumulation of heavy metals and aquatic system and the atmospheric mobilization and deposition of heavy metals, which has local regional and global components (Manson et al., 1994). Many pollutant problems can be linked to the expansion of specific sources which include oil refineries, untreated sewage wastes, and paper factories. There are particular concerns when such sources are adjacent to estuarine and to marine systems supporting significant fisheries (Ninomiya et al., 1995). Although, the pollution increases, no laws or actions were done to prevent or treat the contaminated areas. As in previous studies, the major sources of pollution by heavy metals in southern Iraq are the heavy casualty using of projectiles used in the first and second Gulf wars. The discharging of untreated sewages in rivers, the waste product discharges from oil refineries and petrochemicals are present near the Khour Al-Zubair (Al-Imarah et al., 2010; Al-Imarah et al., 2003; Karabedain et al., 2009). The salt and chlorine plant in Kuwait and petrochemical plant near the north of Kuwait has affected Northwest of the Gulf under the influence of tide and sub tide in the water (Al-Majed and Perston, 2000). The heavy metals in mixed zooplankton organisms can generally be found in higher concentration near the coast, due to the untreated discharged of many waste products of plants close to the coast or near the rivers (Rezai and Yusoff, 2011; Robin et al., 2012). Marin zooplankton constitute is a major component of total biomass of marine environment, and there by plays a vital role in the biogeochemical cycling of heavy metals in the sea (Shulz-Blades, 1992). Plankton is capable of concentrating traces of metals from seawater. The average heavy metals content in zooplankton from north of Mediterranean was reported by many studies (Rezia and Yusoff, 2011). A Certain levels of heavy metals Cd, Cu, Hg, Ni, and Zn were reported in zooplankton's of lake Kenon (Itigilova et al., 2016). The aim of the study is to bring awareness to the lack of studies concerned with the evaluation of heavy metals especially in the zooplankton in this area. The phytoplankton and zooplankton are the primary and secondary producers in the food chain. This fact has not been taken into consideration in this area and other areas including countries such as India (Robin et al., 2012) and Saudi Arabia (Al-Tison and Chandy, 1995).
1 Materials and Methods
1.1 Sample collection
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Figure 1 Map of southern part of Iraq showing the position of sampling stations 1-8 |
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1.2 Chemical analysis
All samples of collected zooplankton were analyzed for heavy metals by ICP/MS at Maxxam. Analytical INC. in Canada, which followed the procedure used by the company.
1.3 Statistical analysis
Statistical analysis was performed using analysis of variance (ANOVA) without replication. This was carried out to observe the special variation of metals variables. Significant level was considered at 95% confidence limit.
2 Results
The density of zooplankton, their main diversity groups as classified earlier (Ajeel et al., 2015), is shown in Table 1 and Table 2. The heavy metals concentrations in zooplankton for all stations are shown in Table 3. The hierarchy concentrations of each individual metals from higher to lower concentration among the stations are summarized in Table 4.
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Table 1 The density and diversity of zooplanktons (ind/m3) collected at study area, stations 1-2, during the period July 2009-March 2010 |
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Table 2 The density and diversity of zooplanktons (ind/m3) collected at study area, stations 3-8, during the period July 2009-March 2010 |
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Table 3 Levels of heavy metals (in µg/g) measured in zooplankton's at different stations within the Iraqi national waters (1-8) Note: n =No. of samples |
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Table 4 The hierarchy for individual element from the higher to lower level of stations |
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3 Discussion
A literature review shows that both freshwater and planktons have trace elements and radionuclides concentrations in a factor of up to 104 (Marsh and Buddemeier, 1984).
The mercury concentration appears to be at the highest level at the Khuor Al-Zubair station and the lowest at Al-Fao station, as shown in Table 3. The multiple comparisons between the stations for the mercury did not show significant difference. In general, the concentration level of mercury in all stations was either moderate or high compared with that of other studies (Chvojka et al., 1990; Al-Majed and Prestona, 2000). This revealed that territories in Basrah are highly contaminated with mercury which has been confirmed by local studies (Al-Imarah et al., 2010).
The Uranium concentration which appeared in analyzed samples showed high levels of concentrations at Al-Musab station, which was significantly high (P < 0.01) when compared with all other stations of study except Ras Al-Bisha which did not have a significant difference in concentrations level. Also, the hierarchy was arranged highest to lowest as follows Al-Musab, Ras Al-Bisha, Khour Al-Zubair, Buoy 29, Shatt Al-Basrah channel, Buoy 13, Buoy 5, and Al-Fao (Table 3) The appearance of Uranium was confirmed in the samples analysis and by other studies carried out in this area (UNEP, 2003; Al-Imarah et al., 2010) as well as in the surrounding countries such as Kuwait (Fido and Al-saad, 2008).
Sources of radioactive elements in the aquatic environment include naturally occurring radionuclide's (Al-Battat, 2016), fallout from atmosphere, due to emission from military waste as well as effluent runoff from that waste during raining and distributed between water column and sediments from which aquatic organisms receive radioactive elements (Al-Imarah and Ali, 2009).
The higher level of lead appeared in Ras Al-Bisha and the lowest level appeared in Buoy 29, as shown in Table 3. The multiple comparisons between the stations did not show any significant differences. The results could be related to the high variable in the readings. The high concentration of Pb which appeared in this study could be a result of the stations 5 which are located near industrial sources. These sources distribute discharges into rivers which increases the bio-availabilities thereby uptake of metal by zooplankton. Metal accumulation by zooplankton is mainly of two pathways which are direct uptake from water and the assimilation from injected food and detritus (Davis, 1978). Also, the observed high level of Pb in zooplankton could be attributed to the high influxes of these regions, primarily from automotive exhausts. These exhausts load and unload large quantities of general and bulk cargo at these localities. Pb is known to form colloids in sea, estuarine and brackish water. These colloids can be absorbed onto plank tonic debris, which consequently might have resulted in a higher concentration of these elements in zooplankton from coastal water (Zauke, 1997; Safahieh et al., 2011; Robin et al., 2012).
For Cadmium, the highest concentration appeared in Al-Musab station and the lowest level appeared in Al-Fao station (Table 3). Though, the hierarchy of Cd concentration in all stations is ranked from highest to lowest as follows Al-Musab, Buoy 13, Buoy 29, Khour Al-Zubair, Buoy 5, Ras Al-Bisha, Shatt-Al-Basrah channel, Al-Fao (Table 4). The Cd concentration in zooplankton reported within this study was higher than that in other study carried in Arabian sea (Rezai and Yusoff, 2011) which was ranged between 0.32 – 0.49 ppm compared to 0.402- 2.620 ppm reported within this study. This indicates that this particular area is highly polluted; which might be very close to the industrialized area than that of other studies (Safahieh et al., 2011).
The higher concentration of Zn appeared in Buoy 13 and Khour Al-Zubair stations, as shown in Table 3. The multi comparison between buoy 13 and the other stations showed higher differences (P<0.01), except that of Ras Al-Bisha which had no significant difference in concentrations. The hierarchy of Zinc concentration ranked from most to least concentrated as follows Bouy 13, Khour Al-Zubair, Shatt Al-Basrah, Ras Al-Bisha, Al-Fao, Buoy 29, Al-Musab, and Buoy 5 as showin in (Table 4). The Zinc concentration is very high in the zooplankton appears in the study comparing with other studies (Ritterhoff and Zauke, 1997; Rezai and Yusoff, 2011; Robin et al., 2012). The increases of high concentration of Zinc could be a result of industrialized plants being close to the stations of study (Figure 1).
Cupper concentration, as listed in Table 3, showed a higher level at station 4 (Buoy 13) and the lowest concentration at station 8 (Al-Fao). The hierarchy from level of concentration was arranged from highest to lowest as follows Buoy 13, Buoya 29, Al-Musab, Khuor-AlZubair, Shatt-Al-Basrah, Buo 5, Ras Al-Bisha, Al-Fao (Table 4). The multi comparison between stations was significantly higher in Buoy13 by P<0.001 than other stations except for Buoy 29 which had no significant change in levels comparing to Buoy 13. The levels of concentrations in the conducted study was higher comparing to other studies in the surrounding areas (Ritterhoff and Zauke, 1997; Rezai and Yusoff, 2011; Safahieh et al., 2011; Robin et al., 2012).
The iron concentrations in most stations appeared at high levels. The highest concentration was recorded at Buoy 29 and the lowest reading was at Al-Musab (Table 3). The multiple comparison demonstrated high significant (P<0.05), when compared Buoy 29 with Shatt Al-Basrah, Khour Al-Zubair and Al-Musab only. On the other hand, when comparing Khour Al-Zubair to the other stations, a significant difference was observed between Khour Al-Zubair and Buoy 29 , Buoy 13 and Al-Fao (P<0.01) (Table 3).
Iron and Zinc are reported to be the highest accumulated chemical elements in zooplankton's (Masuzawa et al., 1988).
The level of cobalt was recorded in all stations, as shown in Table 3. The hierarchy concentration ranked from highest to lowest was as follow Buoy13, Fao, Buoy 29, Buoy 5, Shatt Al-Basrah, Rass Al-Bisha, Khour Al-Zubair, and Al-Musab (Table 4). The cobalt concentration which in this study appeared higher than that of other studies at the Iranian side of the Gulf (Rezai and Yusoff, 2011).
The Nickel concentration (Table 3) shows the highest level at Al-Fao station and the lowest was at Ras Al-Bisha. A reason for the result could be due to the priority of the oil loading terminals.
In conclusion, the increase in concentration of Zn, Pb, Cu, Cd, and Hg in zooplankton of coastal samples is relatively higher than that off shore samples in other studies. The high levels of Iron, Cobalt, Nickel and the appearance of Uranium in this study could be attributed to their industrial sources carried through rivers discharges which increases the Bio availabilities thereby uptake of metals by zooplankton. Zooplankton is very important in the cycling processes of elements in the coastal water since it is a secondary producer in the food chain. Moreover, being a major source of food for larger animals, their role in transporting the metals to the higher tropic level (Gajbhiye et al., 1985). Metals accumulation by zooplankton is mainly by two pathways such as direct uptake from water, the assimilation from injected food and detritus (Davis, 1978). The observed high levels of metal, including Pb in zooplankton in the area of study, could be attributed to the high influxes at this region, primarily from automotive exhausts. Pb is known to form colloid salt and brackish water. The colloids would have adsorbed onto planktonic debris, which consequently might have resulted in higher concentration of this element in zooplankton from coastal water (Robin et al., 2012). The contamination of sea water, freshwater and estuarine water, due to direct exposure to atmospheric input, is probably the major source of pollution in all of the stations used in this study. There is a significant amount of industrial pollutant untreated waste which has been discharged in River Shatt Al-Arab, Shatt Al- Basrah channel, Khour Al-Zubair, and the Gulf. It has been generated from discharging domestic sewages as well as sewages of he oil production industeries and waste of sinking vessels for more than 30 years (Chua et al., 2000).
Finally, the zooplankton's removed nearly all the chemical elements available in the Iraqi National Waters, and help in decreasing pollution by these elements.
Authors’ contributions
FJA carried out the analysis of results and writing the paper. TAK participated in the classification of Zooplanktons. SGA involved in the collection of the zooplankton samples. AYK carried out the processes before heavy elements determination, and RS carried out the ICP analysis for the heavy element in the samples.
Acknowledgments
The authors would like to acknowledge Mr. Ramiz Saad, and Maxxam analytical laborayories INC., Canada for their help in chemical analysis by ICP.
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