International Journal of Marine Science 2016, Vol.6, No.26, 1-13
7
In this context, the soft tissue of bivalve
Paphia undulata
from Lake Timsah, Suez Canal accumulated high
concentrations of heavy metals during the worm months, spring-summer (El-Moselhy and Yassien, 2005). As in
sediments, Pb only showed significant temporal difference (p = 0.0198), while other studied metals recorded
insignificant variations (p = 0.1007, 0.1372 and 0.7968 for Cd, Cu and Zn, respectively).
Figure (3): Mean concentrations of heavy metals (µg/g) in bivalve, Brachidontes variabilis collected from the northern part of the
Gulf of Suez.
Temporal variations in heavy metals accumulation, which were reported in mollusca species from other regions
(Szefer
et al
., 1999; Yüzereroglu
et al
., 2010; Singh
et al
., 2012, 2013 and Rashida
et al
., 2015), may be attributed
to different factors such as food supply for the mollusc populations and/or runoff of particulate metal to the coastal
waters of the lagoon. Seasonal fluctuations of tissue metal concentrations in molluscs may be affected by various
environmental (physicochemical conditions of water) and biological factors (physiological state of organism); and
have been related to a great extent to seasonal changes in flesh weight during development of gonadic tissues
(Cossa and Rondeau, 1985; Joiris
et al
., 1998; Otchere
et al
., 2000, 2003 and Sokolowski
et al
., 2004).
In respect to the spatial distribution of the studied metals in the bivalve
B. variabilis
, station 2 is characterized by
oily sediments which suffered from pollution coming from the surrounding oil industrial area, therefore it has no
any marine life appearance; accordingly, we did not found bivalve species in this station. For other stations, Cd
and Zn exhibited their highest values at station 4 (0.56 and 17.04 µg/g, with an annual means of 0.40 and 16.46
µg/g, respectively), while Pb was found at station 5 (2.54 with an annual mean of 1.70 µg/g) and Cu was in station
1 (4.38 with an annual mean of 4.06 µg/g). Lowest values of the studied metals were recorded at stations 6 (0.18
µg Cd/g and 8.12 µg Zn/g), 1 (0.53 µg Pb/g) and 7 (2.11 µg Cu/g). In the present investigated bivalve, variations
of Cd, Pb, Cu and Zn within the different studied stations were significantly different (p = 0.0001, 0.0424, 0.0000
and 0.0000, respectively). Post-Hoc Comparisons of Means “Duncan test” (Table 4) showed that the difference in
Cd, Cu and Zn concentrations were significantly at a position of stations 1 and 4; while Pb was detected at stations
3 and 5.
The obtained results of the studied metals in soft tissues of
B. variabilis
were more or less comparable with those
recorded in mollusca species by Yassien (1998), El-Moselhy
et al
. (1999), El-Moselhy and Gabal (2004), Kesavan
et al
. (2013) and Sharaf and Shehata (2015). In order to the variation in metals content in the different mollusca
species may be attributed to the bioavailability of each species to uptake metals from the surrounding areas. In
unpolluted and mildly polluted waters, residues of the present studied metals (Cd, Pb, Cu and Zn) are typically <
3, 5, 20 and 300 µg/g, respectively, in base of wet and dry weight regardless of species (Chiu
et al
., 2000;
Widdows
et al.
, 2002 and Bayen
et al
., 2004). Accordingly, the present results were lies in the range of those
recorded for unpolluted and middle polluted water.
