How environmental factors determine mussel metal concentrations? A comparative study between areas facing different pressures

Abstract

This study examines mussel accumulation capacity in relation to metal concentrations in the marine environment as well as mussel food availability in the coastal marine environment. Field data obtained from mussel-farms facing different natural and/or human derived pressures (Thermaikos gulf receiving river discharges and Elefsis bay receiving industrial effluents). Cd, Cr, Cu, Fe, Mn, Ni and Zn concentration in mussels and seawater (particulate phase) chlorophyll α, particulate organic carbon and suspended particulate matter (SPM), seawater temperature and salinity were measured. Median mussel metal concentrations measured as μg g−1 dw were 0.62 for Cd, 5.6 for Cu, 2.8 for Cr, 5.0 for Ni, 129 for Zn, 311 for Fe and 12.4 for Mn. The corresponding concentrations in SPM expressed as μg L−1 were 0.004 for Cd, 0.33 for Cu, 1.14 for Cr, 0.31 for Ni, 3.60 for Zn, 46.0 for Fe and 1.63 for Mn. Mussel metal concentrations were higher at the industrial site. Metals in the seawater particulate phase were higher in the estuary front, which was attributed to higher SPM levels from river discharges. Due to the limited nutritional value of the SPM in the industrial area, mussels were exposed to elevated metal load by both the anthropogenic activities and the slower and more effective digestion of their potential food in order to optimize available organic matter exploitation from restricted and low nutrition value food.