Mineralogical and chemical composition of Arctic gastropods shells

Assessment of environmental controls and natural variability of shell chemistry is inevitable to understand the future of marine calcifiers functioning under the climate change and acidification scenarios. Here we document mineralogical and chemical composition (Al/Ca, Ba/Ca, Fe/Ca, Mg/Ca, Mn/Ca, Na/Ca, P/Ca, S/Ca, Sr/Ca and Zn/Ca ratios) of shells of 27 gastropod species collected in four Arctic and sub-Arctic coastal localities. Most examined gastropods had purely aragonitic shells, although three species were characterized by bimineralic mineralogy, with calcite forming the external shell layer. Positive relationship between shell size and proportion of calcite in bimineralic gastropods indicated that older specimens could possess a thicker outer shell layer of calcite than did younger individuals. Statistically significant differences in shell chemical composition were found among species irrespective of the sampling location, suggesting that organisms exerted a biological control on elements uptake and retention. Extrinsic factors (mostly seawater temperature, seawater and sediment metals concentrations) contributed to elements uptake to a lesser degree. Thus, the observed differences in shell elements' concentrations among gastropod species can be driven by both factors: species-specific selective incorporation of elements into shells and bioavailability of those elements in the ambient environment.