Annual net community production and the biological carbon flux in the ocean

Abstract

The flux of biologically produced organic matter from the surface ocean (the biological pump), over an annual cycle, is equal to the annual net community production (ANCP). Experimental determinations of ANCP at ocean time series sites using a variety of different metabolite mass balances have made it possible to evaluate the accuracy of sediment trap fluxes and satellite-determined ocean carbon export. ANCP values at the Hawaii Ocean Time-series (HOT), the Bermuda Atlantic Time-series Study (BATS), Ocean Station Papa (OSP) are 3 ± 1 mol C m À2 yr À1 -much less variable than presently suggested by satellite remote sensing measurements and global circulation models. ANCP determined from mass balances at these locations are 3-4 times particulate organic carbon fluxes measured in sediment traps. When the roles of dissolved organic carbon (DOC) flux, zooplankton migration, and depth-dependent respiration are considered these differences are reconciled at HOT and OSP but not at BATS, where measured particulate fluxes are about 3 times lower than expected. Even in the cases where sediment trap fluxes are accurate, it is not possible to "scale up" these measurements to determine ANCP without independent determinations of geographically variable DOC flux and zooplankton migration. Estimates of ANCP from satellite remote sensing using net primary production determined by the carbon-based productivity model suggests less geographic variability than its predecessor (the vertically generalized productivity model) and brings predictions at HOT and OSP closer to measurements; however, satellite-predicted ANCP at BATS is still 3 times too low.

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

“…At present, satellite-derived estimates of ANCP are fairly uncertain, but tend to show values that are at least a factor of two lower in the subtropics compared to high latitudes 25,26 . In contrast to the satellitebased estimates and those of most global ocean biogeochemical models, the limited number of sites with experimental determinations of ANCP indicate less variation 10 . We compare these experimentally determined ANCP values against the export production computed with either a constant (C:P) exp or the optimal spatially varying (C:P) exp (Fig.…”

C : N : P stoichiometry at the Bermuda Atlantic Time-series Study station in the North Atlantic Ocean

“…Export production is estimated to be 3-4 mol C m −2 yr −1 in the BATS region (Jenkins, 1982;Emerson, 2014), which requires more nutrient input than observations suggest (Williams and Follows, 1998). A possible mechanism to sustain such export production is the supply of DOM to the sunlit layer.…”

Estimates of micro-, nano-, and picoplankton contributions to particle export in the northeast Pacific

“…In contrast to the low variability in primary production, POC export recorded by moored sediment traps at OSP exhibits a stronger seasonal cycle with fluxes at 200 m depth ranging from ∼ 0.4 mmol C m −2 d −1 in winter to ∼ 2.4 mmol C m −2 d −1 in summer (Timothy et al, 2013). The average annual sediment trap POC flux at OSP (1.4 ± 1.1 mmol C m −2 d −1 ) is nearly 5 times lower than the annual net community production (ANCP) at OSP (6.3 ± 1.6 mmol C m −2 d −1 ), suggesting that the majority of organic carbon export is due to active transport by zooplankton and/or dissolved organic carbon (DOC) export (Timothy et al, 2013;Emerson, 2014).…”