The isotopic composition and elemental chemistry of calcareous microfossils is one of the proxies most frequently applied in paleoceanographic and paleoclimatic studies. Faunal data of foraminifers and the stable isotope (δ13C and δ18O) and elemental ratios of their carbonate shells provide crucial proxies for reconstructing ancient oceanic environments. However, these studies are not possible without complementary research aimed at understanding the biological mechanisms that underlie the isotopic signal. The complexity of these factors demonstrates the necessity of studies on living specimens from culturing experiments with laboratory controlled conditions. It has been proposed that the stable carbon isotope ratios of foraminiferal shells are affected by diet. According to this idea, the stable carbon isotopic composition depends, among other things, on the stable isotopic composition of its food sources and on isotopic fractionation during the feeding process. Therefore, the work that is proposed to undertake in this Marie Curie postdoctoral fellowship aims to better understand feeding strategies in order to properly apply isotope-based proxies in paleoceanography and consists of two parts: 1) to develop a technique that will improve our ability to examine trophic pathways in foraminifera and the fate of carbon ingested by these protists, and 2) to relate the above measurements to isotopic composition of the growing shell using stable isotope tracers. We will test hypotheses addressing species-specific feeding patterns, resource partitioning and selective feeding. These are key hypotheses addressed to better understand food as a controlling resource for foraminifer biomass and shell growth as well as the role of foraminifera in carbon cycling.
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