Global distribution of pteropods representing carbonate functional type biomass

Abstract

Abstract. Pteropods are a group of holoplanktonic gastropods for which global biomass distribution patterns remain poorly resolved. The aim of this study was to collect and synthesize existing pteropod (Gymnosomata, Thecosomata and Pseudothecosomata) abundance and biomass data, in order to evaluate the global distribution of pteropod carbon biomass, with a particular emphasis on its seasonal, temporal and vertical patterns. We collected 25 902 data points from several online databases and a number of scientific articles. The biomass data has been gridded onto a 360 × 180° grid, with a vertical resolution of 33 WOA depth levels. Data has been converted to NetCDF format which can be downloaded from PANGAEA, http://doi.pangaea.de/10.1594/PANGAEA.777387. Data were collected between 1951–2010, with sampling depths ranging from 0–1000 m. Pteropod biomass data was either extracted directly or derived through converting abundance to biomass with pteropod specific length to weight conversions. In the Northern Hemisphere (NH) the data were distributed evenly throughout the year, whereas sampling in the Southern Hemisphere was biased towards the austral summer months. 86% of all biomass values were located in the NH, most (42%) within the latitudinal band of 30–50° N. The range of global biomass values spanned over three orders of magnitude, with a mean and median biomass concentration of 8.2 mg C l−1 (SD = 61.4) and 0.25 mg C l−1, respectively for all data points, and with a mean of 9.1 mg C l−1 (SD = 64.8) and a median of 0.25 mg C l−1 for non-zero biomass values. The highest mean and median biomass concentrations were located in the NH between 40–50° S (mean biomass: 68.8 mg C l−1 (SD × 213.4) median biomass: 2.5 mg C l−1) while, in the SH, they were within the 70–80° S latitudinal band (mean: 10.5 mg C l−1 (SD × 38.8) and median: 0.2 mg C l−1). Biomass values were lowest in the equatorial regions. A broad range of biomass concentrations was observed at all depths, with the biomass peak located in the surface layer (0–25 m) and values generally decreasing with depth. However, biomass peaks were located at different depths in different ocean basins: 0–25 m depth in the N Atlantic, 50–100 m in the Pacific, 100–200 m in the Arctic, 200–500 m in the Brazilian region and >500 m in the Indo-Pacific region. Biomass in the NH was relatively invariant over the seasonal cycle, but more seasonally variable in the SH. The collected database provides a valuable tool for modellers for the study of ecosystem processes and global biogeochemical cycles.