International Journal of Marine Science 2016, Vol.6, No.26, 1-13
10
quality (Tomlinson
et al
., 1980). The PLI gave an evaluation of the overall toxicity status of the sample and also it
is a consequence of the contribution of the studied four metals. The present study area showed PLI values between
0.87 and 3.57 (for sediments) with maximum at station 2, and minimum at station 7 and between 1.07 and 1.69
(for bivalve) with maximum at station 4, and minimum at station 3. The obtained PLI values indicating
progressive decline in the quality of the present investigated sites (Table5).
Table (5): values of the pollution load index (PLI) and metal pollution index (MPI) in sediments and bivalve
B. variabilis
collected
from the Gulf of Suez
Stations
Sediments
B. variabilis
PLI
MPI
PLI
MPI
St. 1
St. 2
St. 3
St. 4
St. 5
St. 6
St. 7
1.59
3.57
1.11
2.34
1.71
2.28
0.87
10.51
23.65
7.35
15.48
11.30
15.11
2.77
1.51
---
1.07
1.69
1.39
1.15
1.25
2.07
---
1.47
2.32
1.91
1.58
1.72
In addition to calculate the PLI values, metal pollution index (MPI) can also be used to assess the quality of the
coastal areas and compare the total metal content in the different compartments of the studied area. In the present
study, MPI varied from 2.77 to 23.65 (sediments) and 1.47 – 2.32 (bivalve) (Table5). MPI was previously used to
evaluate the metal contamination in sediments and different marine organisms, and compare its degree between
locations and within different species (Giusti
et al
., 1999; Hamed and Emara, 2006; El-Sikaily, 2008; Abdel-
Salam and Hamdi, 2014 and Ibrahim and Abu El-Regal, 2014).
According to the calculated data resulting from contamination factor and pollution indices (PLI and MPI); it can
classified the degree of contamination in the present area as following: by using sediment samples, st. 2 > st. 4 >
st. 6 > st. 5 > st. 1 > st. 3 > st. 7, and by using bivalve
B. variabilis
, st. 4 > st. 1 > st. 5 > st. 7 > st. 6 > st. 3. The
difference in contamination degree between sediments and bivalve specie at each site may be attributed to that
bivalve exposure to metals not only from the sediments or from surrounding water, but also through prey
consumption which in turn bioaccumulation of heavy metals in their tissues (Wang and Fisher, 1999). Molluscs as
filter feeder organisms are most frequently used to monitor the pollution of coastal water by metals (Zia and Khan,
1989). Lying in the second trophic level in the aquatic ecosystem, mollusks have long been known to accumulate
trace elements in aquatic ecosystems (Phillips, 1977). However, sediments are the reservoir of metals in the
aquatic systems and can be used as indicator of pollution in the coastal areas, but molluscs species “
B. variabilis
in the present study” can easily use to assess the metal pollution and is a good bioindicator for heavy metals.
5 Conclusion
The land based activities, oil industry and the different shipping activities are the main sources of metal pollution
the Gulf of Suez. The level of the studied metals (Cd, Pb, Cu and Zn) in sediment samples and bivalve
B.
variabilis
were varied among different stations and seasons (summer and winter). In addition to, contamination
factor (CF), pollution indices (PLI and MPI) of sediments and
B. variabilis
were used to determine the degree of
pollution of heavy metals at the different stations and, which indicated that the investigated area was varied
between low and moderate contamination.
In conclusion, soft tissues of bivalve
Brachidontes variabilis
are suitable to be used as bioindicator for heavy
metals contamination in the Gulf of Suez due to its availability to regulate and accumulate elevated concentrations
of different metals and it act as a watch species in the gulf and most other Egyptian water. As well as, detailed
study on the bioaccumulation level of heavy metals by other molluscs species, especially bivalve and gastropod,
