Abstract
Abstract. In vivo chlorophyll a fluorescence is a proxy of chlorophyll a concentration, and is one of the most frequently measured biogeochemical properties in the ocean. Thousands of profiles are available from historical databases and the integration of fluorescence sensors to autonomous platforms has led to a significant increase of chlorophyll fluorescence profile acquisition. To our knowledge, this important source of environmental data has not yet been included in global analyses. A total of 268 127 chlorophyll fluorescence profiles from several databases as well as published and unpublished individual sources were compiled. Following a robust quality control procedure detailed in the present paper, about 49 000 chlorophyll fluorescence profiles were converted into phytoplankton biomass (i.e., chlorophyll a concentration) and size-based community composition (i.e., microphytoplankton, nanophytoplankton and picophytoplankton), using a method specifically developed to harmonize fluorescence profiles from diverse sources. The data span over 5 decades from 1958 to 2015, including observations from all major oceanic basins and all seasons, and depths ranging from the surface to a median maximum sampling depth of around 700 m. Global maps of chlorophyll a concentration and phytoplankton community composition are presented here for the first time. Monthly climatologies were computed for three of Longhurst's ecological provinces in order to exemplify the potential use of the data product. Original data sets (raw fluorescence profiles) as well as calibrated profiles of phytoplankton biomass and community composition are available on open access at PANGAEA, Data Publisher for Earth and Environmental Science. Raw fluorescence profiles: http://doi.pangaea.de/10.1594/PANGAEA.844212 and Phytoplankton biomass and community composition: http://doi.pangaea.de/10.1594/PANGAEA.844485
Highlights
Phytoplankton biomass is generally recognized to play a key role in the global carbon cycle, stressing the need for a better understanding of its spatio-temporal distribution and variability in the global ocean
The vertical distribution of chlorophyll a can be estimated with greatest accuracy from the analysis of water samples by high-performance liquid chromatography (HPLC, Claustre et al, 2004; Peloquin et al, 2013)
In order to assess the vertical distribution of the total chlorophyll a concentration and the chlorophyll a concentration associated to each phytoplankton size index, the FLAVOR method (Sauzède et al, 2015a) is applied to each chlorophyll fluorescence profile, satisfying the quality control procedure
Summary
Phytoplankton biomass is generally recognized to play a key role in the global carbon cycle, stressing the need for a better understanding of its spatio-temporal distribution and variability in the global ocean. Global data compilations of phytoplankton community composition from discrete water samples have recently been published in ESSD (Peloquin et al, 2013) but data remain rather sparse It could be an invaluable source of information to have a database of phytoplankton community size indices with the same spatiotemporal resolution as the fluorescence data sets. The widely used climatology of the global vertical distribution of chlorophyll a concentration is published in the World Ocean Atlas 2001 (Conkright et al, 2002) The latter climatology is based on estimates from analyzed water samples available in the World Ocean Database (WOD, Levitus et al, 2013) and the World Data Center (WDC, http:// gcmd.gsfc.nasa.gov/). This paper presents a global compilation of chlorophyll fluorescence profiles obtained from online databases and from published and unpublished individual sources These were converted into a global compilation of phytoplankton biomass (i.e., chlorophyll a concentration) and community composition using the FLAVOR method. It is obviously a first step towards a database that will regularly be improved thanks to the ongoing intensification of chlorophyll a fluorescence profile acquisition by Bio-Argo profiling floats, gliders and mammals equipped with instruments
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