A 15-million-year-long record of phenotypic evolution in the heavily calcified coccolithophore Helicosphaera and its biogeochemical implications

• Published in: Biogeosciences 2020-06, Vol.17 (11), p.2955-2969
• Main Authors: Supraha, Luka, Henderiks, Jorijntje
• Format: Article
• Language: English
• Subjects: Acidification; Adaptation; Air pollution; Analysis; Aspect ratio; Benchmarking; Biogeochemistry; Calcification; Calcification (Physiology); Carbon; Carbon cycle; Carbon dioxide; Cell size; Coccoliths; Correlation; Cytology; Deep sea; Deep sea drilling; Deep water; Deepwater drilling; Displays (Marketing); Earth Science with specialization in Historical Geology and Palaeontology; Ecophysiology; Evolution; Evolution & development; Experiments; Fossils; Genotypes; Geovetenskap med inriktning mot historisk geologi och paleontologi; Growth rate; Helicosphaera; Inorganic carbon; Light; Miocene; Morphology; Morphometry; Oceans; Organic carbon; Particulate organic carbon; Phenotypic plasticity; Physiological aspects; Physiology; Plankton; Pleistocene; Proxy; Species; Studies; Tropical climate
• ISSN: 1726-4189; 1726-4170; 1726-4189
• DOI: 10.5194/bg-17-2955-2020

The biogeochemical impact of coccolithophores is defined not only by their overall abundance in the oceans but also by wide ranges in physiological traits such as cell size, degree of calcification and carbon production rates between different species. Species' sensitivity to environmental forcing has been suggested to relate to their cellular PIC : POC (particulate inorganic carbon : particulate organic carbon) ratio and other physiological constraints. Understanding both the short-term and longer-term adaptive strategies of different coccolithophore lineages, and how these in turn shape the biogeochemical role of the group, is therefore crucial for modeling the ongoing changes in the global carbon cycle. Here we present data on the phenotypic evolution of a large and heavily calcified genus Helicosphaera (order Zygodiscales) over the past 15 million years (Myr), at two deep-sea drill sites in the tropical Indian Ocean and temperate South Atlantic. The modern species Helicosphaera carteri, which displays ecophysiological adaptations in modern strains, was used to benchmark the use of its coccolith morphology as a physiological proxy in the fossil record.