Concentrations of Heavy Metals (Zn, Cu, Pb, Cd and As) in the Mediterranean Mussel Mytilus Galloprovincialis from the Montenegrin Coast of the Southeastern Adriatic Sea

Danijela Joksimović1, Zoran Kljajić1, Slavka Stanković2

 

 

1 University of Montenegro, Institute of Marine Biology, Dobrota bb, 85330 Kotor, Montenegro; e-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

2University of Belgrade, Faculty of Technology and Metallurgy, Karnegijeva 4, 11 000 Belgrade, Serbia

 

Abstract

The Mediterranean blue mussel Mytilus galloprovincialis (L) was collected from fall 2006 to spring 2007 from five sites along the Montenegrin coastline. Three wild samples were collected from the open sea coastline, and the other two wild samples, were collected from the enclosed Boka Kotorska Bay. The soft tissue of mussels was analyzed for zinc (Zn), copper (Cu), lead (Pb), cadmium (Cd) and arsenic (As). Concentrations of these metals ranged from 160 - 221.1 for Zn, 6.25 -15.25 for Cu, 4.25 - 9.5 for Pb, 1.4 - 2.3 for Cd and 3.7-11.2 for As in mg kg-1 dry weight. Metals were found to be present in samples at different levels, but not in concentrations higher than maximum residual levels prescribed by EU.

Keywords: M. galloprovincialis, heavy metals, Montenegro, Adriatic

 

Introduction

 

The continental shelf constitutes the most important zone of the marine environment as far as human activities are concerned, as it contains the main source of living marine resources (Castro et al., 1999; Usero et al., 2005) and as the area that is most concerned by human-induced changes (Zoller, 2006). The coastal part of this continental shelf is the most sensitive, as it receives large amounts of contaminants introduced by domestic, industrial and agricultural activities, directly or via rivers or through atmospheric deposition (Zoller and Hushan, 2000; Usero et al., 2005). Pollution by heavy metals is a serious problem due to their toxicity and their ability to accumulate in biota (Isam and Tanaka, 2004).

Metals are natural constituents of the biosphere. Many are essential to biological systems to such a degree that in the absence of an essential metal an organism can neither grow nor reproduce (Underwood, 1977). Apart from the major ions such as sodium, potassium, calcium and magnesium which are essential to sustain life, other metals, normally only present in trace amounts, are also required to some degree. Organisms absorb heavy metals, essential or not, from the surrounding environment with the potential to accumulate them within their bodies. All heavy metals are potential toxins at some concentration (Rainbow, 1993), but the non-essential metals e.g. mercury, lead and cadmium are particularly toxic at relatively low concentrations (Bryan, 1976).

Mussels are an important source of Ca and Fe, some vitamins such as niacin and thiamine, and are a good source of protein for human consumption (Yap et al., 2004). Even though mussels are an excellent source of nutrients, they can potentially be toxic because certain metals - such as Pb, Cd, As and Hg - can accumulate in their soft tissue over time making them detrimental to human health (Clarkson, 2002, Sivaperumal et al., 2007, Mubiana and Blust, 2007, Joksimović et al., 2011). As natural habitats of M. galloprovincialis (L) are usually close to estuaries, they are exposed to contaminants from land-based activities, as well as to sea based ones, making them an excellent heavy metal biomonitoring agent (Jović et al., 2011).

Due to the propensity of M. galloprovincialis (L) to accumulate metals and other contaminants in their soft tissue (Phillips, 1976a; Phillips, 1976b; Goldberg et al., 1978; Roméo et al., 2003; Roméo et al., 2005), mussels have actively been used as a biomonitoring agent, as the determination of contaminant levels in mussel species provides means of assessing the possible toxicant risk to public health (Sivaperumal, et al., 2007, Kljaković-Gašpić, et al., 2007, Türkmen and Ciminli, 2007). Since heavy metals are non - biodegradable inorganic chemicals which cannot be metabolized and will not break down into harmless forms (Kromhout, et al., 1985), the measurement of their concentration in mussel soft tissue has become increasingly significant.

The primary purpose of this study was to obtain quantitative information on the concentration of trace metals in the soft tissue of M. galloprovincialis collected from natural (wild) farms of the Southeastern Adriatic - Montenegrin coast. The results reported here will provide valuable information on heavy metal pollution along the Adriatic coast.

 

 

Study area

The samples for analysis were collected during fall 2006 and spring 2007 from five sites from this Adriatic coastal area: Sv. Stasije and Herceg Novi in the semi-enclosed Boka Kotorska Bay, and Žanjice, Bar and Rt Djeran on the open coastline, situated in the proximity of different geochemical, hydrological and human impacts.

The Boka Kotorska Bay occupies a specific position in the Adriatic Sea. It is composed of four smaller bays which build upon each other (Herceg Novi and Tivat which make the outer part, and Risan and Kotor make the inner part of the Bay) and two penetrations; the first one connects the open sea to the Bay and the other (Verige) connects Tivat with Risan and Kotor Bay. Sv. Stasije and Herceg Novi are located in Boka Kotorska bay, they are favoured touristic city destinations, with marine, shipyard and food industries. The beach Žanjice with a lot of cottages is situated close to the entrance of the Bay. The port of Bar is in the south of the Montenegrin coastal area with 15,000 inhabitants. Bar is an important industrial harbour, especially for crude oil and oil products traffic. Rt Djeran is a place near the big tourist-town of Ulcinj, and the 12 km long sand beach, with 60,000 inhabitants and a large number of industrial facilities and highly intensive agricultural activities. The problem of pollution in the vicinity of these sites increases in the fall periods because of the summer tourist seasons and increased discharge of wastewater directly into the sea. For this reason, the water and mussel samples were all collected in the fall.

Material and methods

Sampling, storage and sample preparation

The sampling sites are shown in Figure 1. Sampling was conducted in fall 2006 and spring 2007. The mussels and the seawater samples from the surface were collected simultaneously at all studied locations. Three samples were collected from the wild site in the open sea and two in the enclosed Boka Kotorska Bay. Mussels of similar shell length were placed in plastic bags with sea water, and transported to the laboratory. After washing and cleaning with additional seawater, they were opened raw and the flesh was scraped out of the shells, and then frozen, lyophilized, reduced to powder, dissolved and analyzed.

 

Fig01

Figure 1: Sampling locations in the southeastern Adriatic Sea, Montenegro: 1. Sveta Stasija, 2. Herceg Novi, 3. Žanjice, 4. Bar and 5. Rt Djeran