ITCH

Oceanic plankton are sensitive to physical and biochemical changes in the surface ocean. It is an important modulator of the ocean carbon cycle through photosynthesis and calcification.

Fossil remains of plankton deposited on the seabed and preserved in sediments contain key clues to past climate change and associated biological responses and feedbacks.

The Western Equatorial Indian Ocean (WEIO) is a major player in the ocean-atmosphere dynamics of the tropical ocean: it has an impact on global climate.

In 2021, the SCRATCH mission aboard the oceanographic vessel Marion Dufresne II collected high quality sediment cores from the WEIO covering the Pleistocene (~2 million years), with the aim of resolving past climate variability and volcanic activity in this important region. In this project, we propose to study the coevolution of plankton and climate during the Pleistocene.

We will perform palaeogenetic, biomarker and micropalaeontological analyses, as well as reconstruction of key palaeoceanographic variables to reconstruct climate change, in four sediment cores collected during the SCRATCH cruise. Using state-of-the-art methodologies from three partner institutes, we will combine expertise in palaeoceanography, organic geochemistry, genetics and micropalaeontology to test the hypothesis that cyclic changes in plankton fossil morphology represent genetic evolution, forced by external climate cycles. The expected results will provide a comprehensive picture of the palaeoceanographic evolution of the WEIO, including the mean state of the Indian Ocean dipole, explore for the first time the relationship between genetic and morphological evolution of plankton in multiple groups, and inform on the external (climatic, volcanic) drivers of evolution, planktonic community dynamics and pelagic and neritic productivity.