International Journal of Marine Science, 2016, Vol.6, No.10, 1-8
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3 Results and Discussion
The result obtained for the determination of the concentration of heavy metals in liver, gills, eggs and muscle
tissues from Sinop coasts of the Black Sea were given in Figures 2A-H. There are high levels of Zn and Fe at a
significant level (P<0.05) in
M. merlangus
when compared with other metals, followed by the Mn, Co and Cu.
However, there is no significant variation (P>0.05) observed among the heavy metal levels in themuscles and eggs.
Al, Ni and Hg in all tissues were below the detection limits. Cd and Pb were not detected in the edible parts of
M.
merlangus
. Gill and liver tissues showed higher metal concentrations than edible tissues including eggs. The
highest concentrations were found in gills (Fe: 57±9 mg/kg wet wt., Mn: 2.4±0.2 mg/kg wet wt., Cr: 0.65±0.05
mg/kg wet wt. and Pb: 0.88±0.006 mg/kg wet wt.) and in liver (Zn: 43±6 mg/kg wet wt., Co: 0.88±0.03 mg/kg
wet wt., Cu 0.41±0.02 mg/kg wet wt. and Cd: 0.075±0.006 mg/kg wet wt.). The lowest metal levels were
determined in muscle tissues of whiting followed eggs.
The result shows that Zn has the highest concentration in liver than those in other tissues. However the highest
concentration of Fe was in the gills than the other tissues, an indication of its availability in the environment. Cu
has the least of the heavy metals in edible tissues of
M. merlangus
analyzed.
The lowest concentration (0.05±0.003 mg/kg wet wt.) of Mn was observed in the muscles, while the highest
concentration of 0.52±0.05 mg Mn/kg wet wt. Mn was detected in gill. Mn is an essential and deficiencies of the
result in severe skeletal and reproductive abnormalities in mammals (Akan et al., 2012). Cr is also an essential and
the biologically usable form plays vital role in glucose metabolism (Akan et al., 2012). In this study the lowest
concentration (0.06±0.003 mg/kg wet wt.) of Cr was observed in the muscles, while the highest concentration of
0.65±0.1 mg Cr/kg wet wt.
Noreña et al. (2012) indicated that Ni accumulation in fish is not common in research related to environmental
pollution because of its low uptake and rapid elimination. In this study Ni levels in all tissues of
M. merlangus
were below detection limit.
Non-essential metals such as Hg, Pb and Cd, among others, have taken great importance, because their toxic
properties through different levels along the food chain. Fish is the main source of metals like Hg in human diet
(Hosseini et al., 2015).
Zeri et al. (2000) show that the Black Sea is rich in Cd, Co, Cu and Ni, as compared to other regional seas.
However, a comparison of mean concentrations of heavy metals in tissues of some fish species from the
Romanian and Bulgarian coasts of the Black Sea demonstrates that the metal levels in fish tissues are variable and
reflect the level of contamination in the sampling areas (Jitar et al., 2013). Ni levels were slightly higher in
anchovies, bluefish and sprat (Oros et al., 2010).
Large differences in heavy metal concentrations were observed between different tissues. Cd and Pb levels in eggs
and muscle tissues were below detection limits. Regarding these metals significant differences (p<0.05) are
distinguished in the accumulated levels in gills and liver of fish samples. Cd levels in liver (0.74±0.2 mg/kg wet
wt.) were higher than those in gills (0.48±0.1 mg/kg wet wt.) suggesting that liver as the major reservoir of this
metal in the fish organ. Noreña et al., (2012) agreed that Cd binds to
metallothionein
in cells which is more toxic
to renal tubules than the Cd itself whereas Pb levels (0.61±0.15 mg/kg wet wt.) in gills were higher than those in
liver (0.28±0.03 mg/kg wet wt.) in this study. Similar results were found by Akan et al., (2012). It is highlighted
that the gills are a major organ of accumulation of heavy metals, since they are in direct contact with the water and
therefore are the first barrier of defense (Noreña et al., 2012). The fish gills tend to accumulate critical
concentrations of heavy metal than other tissues (Akan et al., 2012). In general it is approved that if the main entry
route of the xenobiotic is via the water, the high concentrations would be in gills, yet the intake is mainly for food
contaminated with metals, the accumulation would take place in the digestive system tract tissues or organs
(Noreña et al., 2012). The liver plays vital role in accumulation and detoxification of heavy metals and the liver
