Seasonal and interannual variability of heavy metals and other microelements in wild and farmed mussels Mytilus galloprovincialis in Saldanha Bay (South Africa)

Abstract

The temporal fluctuations of the levels of 21 of macro- and microelements including heavy metals in soft tissues and shells of mussels from waters of Saldanha Bay (South Africa) collected in the period of 2013–2019 were analyzed by using Neutron activation analysis. The wild and farmed sets of Mytilus galloprovincialis were selected from the bays with different hydrological conditions: from open ocean bay to the relatively closed site. It was concluded that the found features of elements’ distribution could be explained by hydrological regimes, influence of the coastal runoffs and mixing of waters, which led to higher levels of heavy metals and microelements. The farmed mussels demonstrated lower maxima for many elements during the study period but could show local increasing due to intense hydrological mixing with resuspending of bottom sediments and terrigenous runoff indicated by the non-volatile elements such as Sc, Cs, Th. The obtained data were not revealed high anthropogenic influence during studied period in comparison with the other water areas. The study proposed the indicative background levels for the heavy metals and other determined elements in the Saldanha Bay area based on the maximum values from the pristine water area obtained in the considered period.