Elsevier

Journal of African Earth Sciences

Volume 87, November 2013, Pages 93-99
Journal of African Earth Sciences

Gastropod shells as pollution indicators, Red Sea coast, Egypt

https://doi.org/10.1016/j.jafrearsci.2013.08.004Get rights and content

Highlights

  • Nerita albicilla and Canarium (Gibberulus) gibbosus are used as pollution indicator.

  • Gastropods do not show the same response to pollutants.

  • The Red Sea coast is subjected to natural and anthropogenic pollutants.

Abstract

Thirty samples of gastropod shells belonging to Nerita albicilla and Canarium (Gibberulus) gibbosus from 15 stations along the Egyptian Red Sea coast were selected for chemical analysis. The analysis indicated that Nerita is a geochemical marker for a sizeable group of trace elements including; Cu, Pb, Zn, Ag, Th, Ba, Tl, S, Sc and Se, while Canarium is a good accumulator of the elements, Mo, U, Au and K. Both species have the same selectivity for Ni, Mn, Fe, As, Sr and P. The differences in sensitivity between the two species are attributed to the mode of life and incorporation of the elements within the crystal lattice of calcium carbonates composing the shells. On basis of the obtained data, the study area can be subdivided into three zones namely; almost pristine, moderately polluted zone and markedly polluted. Pollution is mostly attributed to anthropogenic sources.

Introduction

Marine organisms can be exposed to high metal concentrations as a result of near shore developmental activities such as coastal mining, harbor dredging, discharge of industrial and domestic effluents into the ocean, urbanization and over population (Bastidas and Garcia, 1999, Esslemont, 2000, Fallon et al., 2002, Gopinath et al., 2009). Many studies were done on the Red Sea environment, and tourism projects and their impact on coastal zone based on the ecological analysis by several authors, e.g., Kotb et al., 2001, Abd El-Wahab and El-Sorogy, 2003, Wielgus et al., 2004, Shaalan, 2005, El-Sorogy, 2008, Madkour and Youssef, 2008 and El-Sorogy et al. (2012).

The quantification of pollution magnitude in the aquatic ecosystems is a relatively new field of research. Human environment is tightly linked to the aquatic ecosystems, hence will be subjected, by way or another, to the same pollutants like marine organisms. The present work focuses on the possible toxicity of aquatic organisms by trace metals as a requisite for the protection of this ecosystem rather than an inexpensive safeguard to man, although these aims are not mutually exclusive. In a sense, all organisms pollute their immediate environment, at least by the excretion of waste products. There are few studies on the trace elements concentration in seashells. However, many studies on the tissues of organisms are carried out. Walsh et al. (1995) recorded that gastropods have the potential to act as a useful bio-monitoring system of pollutants in the marine environment.

The main objectives of the present study are to evaluate the levels of pollution along the Red Sea coast from Abu Darag on the Gulf of Suez southwards to Berenice (Fig. 1). Two gastropod species (Fig. 2) are selected for monitoring toxicity by trace metals, namely; Nerita albicilla (Linnaeus) and Canarium (Gibberulus) gibbosus (Röding). These two species have a wide geographical distribution along the Red Sea coast, moreover they are large enough, easy to be sampled and have relatively long life time. The selectivity of the two species for trace elements can be considered as geochemical markers in environmental assessment of shore lines.

Fifteen shells of living N. albicilla and similar number of Canarium (Gibberulus) gibbosus were selected from rocky shore dwellers of fifteen stations to perform complete chemical analysis. These stations (Fig. 1) were chosen to cover the most polluted and most “pristine” sites along the Red Sea coast of Egypt.

The selected shells were washed and the soft tissues were separated from the shells with a glass rod. The shells were cleaned by scrubbing in distilled water with tooth brush to remove loosely attached biogenic and inorganic particles and dried at 80 °C to constant weight. Each shell was crushed and pulverized to −100 mesh grain size and then placed in adequate plastic veils. The analysis of 20 elements (Fe, Cu, Pb, Zn, Ni, Mn, U, Th, Mg, Sr, P, Se, As, Ba, Sc, Mo, Au, Ag, Tl and S) was done by the inductively coupled plasma-mass spectrometry (ICP-MS) in the Analytical Laboratories Ltd., Canada (Table 1, Table 2).

Section snippets

Results and discussion

The Red Sea coast has been considered, for a long time, as being relatively unpolluted or almost “pristine”. Recently, some forms of pollution such as leakage from oil fields, refining, navigation, phosphate ore shipping, waste, sewage and other activities are associated with mobilization of metal into the marine environment. The modern advances point to the significance of the trace elements content for the food web and the soil–plant–animal chain. Consideration must be given to essentiality,

Conclusions

The Red Sea coast is subjected to natural and anthropogenic sources of trace elements. The natural sources include weathering of rocks, thermal springs, wadi deposits and vegetation. Inputs from anthropogenic sources include tourist activity, smelting, oil spills, industrial and mining operations, waste disposal, agricultural activities, and domestic sewage.

The study area can be subdivided into three zones; the first one is the almost pristine zone which covers the stations: 12 km to the north

Acknowledgements

This work was supported by King Saud University, Deanship of Scientific Research, College of Science Research Center.

References (32)

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