Regional variation in the particulate organic carbon to nitrogen ratio in the surface ocean

Abstract

[1] The concept of constant elemental ratios in plankton communities-the Redfield ratio -is of central importance to ocean biogeochemistry. Recently, several studies have demonstrated regional differences in the plankton C:P and N:P ratio. However, less is known about potential systematic variations in the C:N ratio. Here we present an analysis of the particulate organic carbon to nitrogen ratio of 40,482 globally distributed samples from the upper 200 m of the ocean water column. Particulate organic carbon and nitrogen concentrations are highly correlated (R 2 = 0.86) with a median value of 6.5. Using an artificial neural network analysis, we find regional variations in the C:N ratio linked to differences in environmental conditions. The ratio is lower in upper latitude cold water as well as upwelling regions in comparison to the warm oligotrophic gyres. We find substantial differences between ocean gyres that might be associated with differences in the nutrient supply ratio. Using cell sorting, we also quantified the C:N ratio of Prochlorococcus, Synechococcus, and picoeukaryotic field populations. The analysis demonstrates that picophytoplankton lineages exhibit a significantly higher ratio than the bulk particulate material but are only marginally significantly different from each other. Thus, the dominance of picophytoplankton in ocean gyres may contribute to the elevated ratios observed in these regions. Overall, the median C:N ratio derived from 40,482 samples is close to the canonical Redfield ratio, but significant regional deviations from this value are observed. These differences could be important for marine biogeochemistry and the regional coupling between the ocean's carbon and nitrogen cycles.

Global-scale variations of the ratios of carbon to phosphorus in exported marine organic matter

“…If we assume that the low C:N ratio observed in high-latitude suspended particles 17 is also present in exported organic matter, the low (C:P) exp in high-latitude regions is consistent with the high-latitude dominance of diatoms, which have been shown to contribute export with low N:P ratios 18 . We also find extensive regional variation in (C:P) exp between the subtropical gyres.…”

Variation pattern of particulate organic carbon and nitrogen in oceans and inland waters

“…This leads to a C/N ratio that is higher and much more variable in inland waters than in offshore oceans; there is also a sharp contrast in nutrient levels and water residence times between the two (Hall et al, 2007, Sterner et al, 2008Watanabe and Kuwae, 2015). Several studies suggest that the currently observed C/N ratio, and variations in it, are difficult to reconcile with the value estimated by Redfield (6.63-7.7), which was based on data 55 taken from ocean-surface plankton and deep, dissolved nutrients from 1898 to 1933 (Kokrtzinger et al, 2001;Schneider et al, 2004;Koeve, 2006;Sterner et al, 2008;Martiny et al, 2013a;2013b;DeVries and Deutsch, 2014;Watanabe and Kuwae, 2015). The factors influencing variations in C/N are complex; nitrogen and light limitation and phytoplankton can only explain approximately 20% of the variation in C/N on a global scale (Martiny et al, 2013b).…”

The <sup>3</sup>He flux gauge in the Sargasso Sea: a determination of physical nutrient fluxes to the euphotic zone at the Bermuda Atlantic Time-series Site

“…In carbon units, using the revised Redfield ratio of Anderson and Sarmiento (1994) of 106 : 16, new production estimated in this study was 4.3 ± 0.9 mol C m −2 yr −1 in 2003-2006 and 6.96 ± 1.3 mol C m −2 yr −1 in 1985-1988. Because of global and regional variations in the C : N ratio Martiny et al, 2013;Ono et al, 2001), there are additional uncertainties when converting nitrate fluxes to carbon fluxes. Additionally, as noted above, these rates represent new production derived from the physical vertical supply of nitrate over the northern half of the subtropical gyre.…”