Catarina V. Guerreiro is a researcher and lecturer in Marine Sciences at the Faculty of Sciences of the University of Lisbon (FCUL). She is an integrated member of MARE/ARNET (MARE – Marine and Environmental Sciences Centre / ARNET – Aquatic Research Network) and a collaborator of the Instituto Dom Luiz (IDL). Her research lies at the interface between biological oceanography, marine biogeochemistry, and paleoceanography, with a particular focus on coccolithophores—microscopic algae that produce a calcite shell around their cell—and their role in the marine carbon cycle, carbonate production, and climate regulation. She adopts a source-to-sink, multi-timescale approach, linking processes operating in the modern ocean to sedimentary archives that record past ocean and climate variability. Her work integrates in situ oceanographic observations, satellite remote sensing, laboratory microcosm experiments, sediment trap records, and deep-sea sediments to investigate atmosphere–ocean–seafloor interactions and the response of marine pelagic ecosystems to natural variability and climate change. She has coordinated and contributed to several national and international research projects addressing climate variability, desert dust deposition, and ocean-based carbon dioxide removal strategies, with a strong focus on the Atlantic Ocean and contributions to studies in the Southern Ocean. She is the Portuguese National Representative of the SOLAS (Surface Ocean–Lower Atmosphere Study) international network, a member of the Board of the International Nannoplankton Association (INA), and is actively engaged in the training and mentoring of students and early-career scientists, as well as in science communication and outreach. Driven by a deep passion for the ocean and scientific curiosity, she believes that understanding the ocean is fundamental to understanding the planet—and our future.