Impact of eutrophication and climate change on Cd and other trace metal dynamic in the Gulf of Riga, Baltic Sea

The ability of Cd and other trace metals to be incorporated in living phytoplankton cells has been widely used to explain its dynamic in marine ecosystem. However, the discrepancy between results from water column studies and those from studies in sediments remain unexplained. This strongly suggests a need for study with a more interconnected approach in identification of the main governing factors of trace element dynamics. Therefore, we conducted this study, which linked sedimentary records of trace elements with particular emphasis on Cd with available supporting information from sediments and water column. The concentrations of Cu, Mn, Cd and Cr in sediments of the Gulf of Riga exhibited significant (P < 0.01) positive relationships, while concentrations of Al and Ni had significant (P < 0.01 and P < 0.05, respectively) negative correlation with concentrations of TC. Concentrations of Zn, Pb and Fe in sediments did not exhibit significant correlation with concentrations of total carbon (TC). The vertical profiles of concentrations of several elements indicated that their accumulation patterns in sediments have changed substantially over time in respect to that of TC. The magnitude of change varied substantially from retaining positive correlation but changing element ratio value, in case of Cd, to complete shift from positive correlation to negative, in case of Zn and Cu.