Metals in the shell of Bathymodiolus azoricus from a hydrothermal vent site on the Mid-Atlantic Ridge

A Cravo,P Foster,C Almeida,R Company,R.P Cosson,M.J Bebianno

doi:10.1016/j.envint.2007.01.002

A Cravo, P Foster + Show 4 more

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https://doi.org/10.1016/j.envint.2007.01.002

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Abstract

Specimens of the mussel Bathymodiolus azoricus were collected from Menez Gwen, a relatively shallow (850 m) hydrothermal vent field on the Mid-Atlantic Ridge. Each bivalve shell ( n = 21) was individually cleaned by selective chemical. The residual crystal matrix of each shell was individually analysed for the concentrations of the minor elements magnesium and strontium and the trace elements iron, manganese, copper and zinc. The chemical composition of the crystal matrix is unusual. B. azoricus is identified as a species having one of the most strontium impoverished shells amongst the marine molluscs. For a bimineral species the magnesium concentration is also extraordinary low. Despite originating from a trace metal rich environment; the metal concentrations in the shells were exceptionally low. Mean concentrations of iron, manganese, copper and zinc were 20.6, 3.7, 0.6 and 9.4 μg g − 1 respectively. Minor and trace element concentrations exhibited a marked intra-population variability. Copper concentrations increased and iron and zinc concentrations decreased with increasing shell weight. Due to its insensitivity to the high environmental levels of trace elements and the variability in intra-population concentrations induced by shell weight the crystal matrix of the shell of B. azoricus has little potential for use in environmental trace metal monitoring in areas contiguous to deep-sea hydrothermal vents.

Highlights

Hydrothermal vents, first observed at the Galapagos Ridge in the East Pacific Ocean in 1977 are very unusual environments (Little and Vrijenhoek, 2003; van Dover and Lutz, 2004)
In view of the high concentrations of dissolved, colloidal and particulate trace metal concentrations in hydrothermal vent areas this paper addresses the cleaning problem and presents for the first time data on the chemical assemblage in the crystal matrix of the shell of a deep-sea hydrothermal mollusc, B. azoricus
Of the minor elements associated with the shells of the Menez Gwen population strontium was consistently present in much higher concentrations than magnesium

Summary

Introduction

Hydrothermal vents, first observed at the Galapagos Ridge in the East Pacific Ocean in 1977 are very unusual environments (Little and Vrijenhoek, 2003; van Dover and Lutz, 2004). Concentrations of toxic trace metals in the solution, colloidal and particulate phases are generally extremely high (Desbruyères et al, 2001; Douville et al, 2002). Such areas are highly biologically productive (Rousse et al, 1997; Little and Vrijenhoek, 2003; van Dover and Lutz, 2004). Amongst the life forms associated with the chimneys of the hydrothermal sources the bivalve mussels (Bathymodiolus sp.) are normally found living in high densities (van Dover et al, 1996; von Cosel et al, 1999; Desbruyères et al, 2001; Hardivillier et al, 2004; Miyazaki et al, 2004)

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