New insights into global biogeographic distribution patterns of oceanic tintinnids: a species-level approach

Tintinnids are key components of the marine microbial food web. Previous studies classified the global biogeography of oceanic tintinnids into three broad Regions at the genus level, but a finer resolution is needed to improve both taxonomic and spatial understanding, especially when compared with the well-established nine-belt framework of epipelagic plankton. Drawing on recent advances in studies of cross-water mass distributions over the past decade, this review refines the biogeography of oceanic tintinnid at the species level. We propose that oceanic tintinnids can be delineated into fourteen biogeographical belts: the Arctic Belt, the Subarctic-Arctic Transition Belt, the Subarctic Belt, two Tropical Submergence Belts, two Subtropical Belts, two Subsurface Maximum Belts, the Equatorial Belt, the Subantarctic Belt, the Subantarctic-Antarctic Transition Belt, the Antarctic Belt and the Antarctic Slope Belt. Each belt had a variable number of endemic species. Oceanic tintinnid biogeography comprised more belts than that of other plankton, with the presence of a Northern-Southern Hemisphere asymmetry. Oceanic tintinnid abundances in different belts had characteristic vertical distributions. More field surveys are needed in future studies to fill the existing knowledge gaps in tintinnid biogeography such as differences between Pacific, Atlantic and Indian Oceans, seasonal variations, poleward expansions.