A global diatom database – abundance, biovolume and biomass in the world ocean

Phytoplankton identification and abundance data\r\nare now commonly feeding plankton distribution databases\r\nworldwide. This study is a first attempt to compile the largest\r\npossible body of data available from different databases as\r\nwell as from individual published or unpublished datasets\r\nregarding diatom distribution in the world ocean. The data\r\nobtained originate from time series studies as well as spatial\r\nstudies. This effort is supported by the Marine Ecosystem Model Inter-Comparison Project (MAREMIP), which aims\r\nat building consistent datasets for the main plankton functional\r\ntypes (PFTs) in order to help validate biogeochemical\r\nocean models by using carbon (C) biomass derived from\r\nabundance data. In this study we collected over 293 000 individual\r\ngeo-referenced data points with diatom abundances\r\nfrom bottle and net sampling. Sampling site distribution was\r\nnot homogeneous, with 58% of data in the Atlantic, 20%\r\nin the Arctic, 12% in the Pacific, 8% in the Indian and 1%\r\nin the Southern Ocean. A total of 136 different genera and\r\n607 different species were identified after spell checking and\r\nname correction. Only a small fraction of these data were\r\nalso documented for biovolumes and an even smaller fraction\r\nwas converted to C biomass. As it is virtually impossible\r\nto reconstruct everyone’s method for biovolume calculation,\r\nwhich is usually not indicated in the datasets, we decided to\r\nundertake the effort to document, for every distinct species,\r\nthe minimum and maximum cell dimensions, and to convert\r\nall the available abundance data into biovolumes and C\r\nbiomass using a single standardized method. Statistical correction\r\nof the database was also adopted to exclude potential\r\noutliers and suspicious data points. The final database contains\r\n90 648 data points with converted C biomass. Diatom\r\nC biomass calculated from cell sizes spans over eight orders\r\nof magnitude. The mean diatom biomass for individual locations,\r\ndates and depths is 141.19 μg Cl−1, while the median\r\nvalue is 11.16 μg Cl−1. Regarding biomass distribution,\r\n19% of data are in the range 0–1 μg Cl−1, 29% in the range\r\n1–10 μg Cl−1, 31% in the range 10–100 μg Cl−1, 18% in\r\nthe range 100–1000 μg Cl−1, and only 3% > 1000 μg Cl−1.\r\nInterestingly, less than 50 species contributed to >90% of\r\nglobal biomass, among which centric species were dominant.\r\nThus, placing significant efforts on cell size measurements,\r\nprocess studies and C quota calculations of these\r\nspecies should considerably improve biomass estimates in\r\nthe upcoming years. A first-order estimate of the diatom\r\nbiomass for the global ocean ranges from 444 to 582 Tg C,\r\nwhich converts to 3 to 4 Tmol Si and to an average Si\r\nbiomass turnover rate of 0.15 to 0.19 d−1. Link to the dataset:\r\ndoi:10.1594/PANGAEA.777384.