Biological production of the oceans: the case for a consensus

Abstract

Biological dynamics in the pelagic ocean are intermittent rather than steady. In oceanic regimes, where nitrogen is limiting to phytoplankton growth, an important fraction of the annual, primary production depends on transient episodes of increased nitrate supply: at such times the role of locally-regenerated nitrogen is correspondingly less. Proper averaging of these variable rates, in time and space, is the key to reconciliation of existing data on the biogenic fluxes of oxygen and carbon in the ocean. The magnitude of oceanic production supported by nitrate (the new production) is higher than previously thought.

Basin scale estimates of sea surface nitrate and new production from remotely sensed sea surface temperature and chlorophyll

“…A major fraction of this carbon transported into the oceans' interior is associated with allochthonous nitrogen inputs, primarily nitrate (N), into the euphotic zone [Eppley and Peterson, 1979;Platt et al, 1989]. Hence, understanding the spatial and temporal variations of N over basin and global scales in the euphotic layer is an important requirement for ocean biogeochemical and climate studies [Platt et al, 1989]. Unfortunately, since N measured conventionally, has limited coverage over space and time, particularly in high latitude areas in winter, most studies rely on maps of N constructed using multi-year data sets [Strass and Woods, 1991 The monthly maps of SSN that were generated, provide a synoptic view of the spatial extent and magnitude of N injection into the surface layer due to winter convective mixing and its consumption following the onset and progress of phytoplankton growth season.…”

“…A major fraction of this carbon transported into the oceans' interior is associated with allochthonous nitrogen inputs, primarily nitrate (N), into the euphotic zone [Eppley and Peterson, 1979;Platt et al, 1989]. Hence, understanding the spatial and temporal variations of N over basin and global scales in the euphotic layer is an important requirement for ocean biogeochemical and climate studies [Platt et al, 1989].…”

Oxygen and nitrate new production and remineralization in the North Atlantic subtropical gyre

“…This approach has numerous difficulties [cf. Platt et al, 1989]. One of the greatest of these, which is relevant to estimating an overall steady state balance, is the problem of obtaining long-term averages.…”

“…Most of the organic matter thus produced is recycled by organisms within the euphotic zone (regenerated production). The remaining highly variable and rather poorly known fraction of order 30% [Platt et al, 1989] manages to escape to the thermocline and abyssal waters. There it is remineralized by metabolic processes which convert organic matter back to dissolved inorganic CO2, PO• -3, and NOj -•, consuming oxygen in the process.…”

Exposure factors for marine eutrophication impacts assessment based on a mechanistic biological model

“…The ecological equivalent for the photosynthesis rate in marine systems is the primary production (PP) rate (Platt et al, 1989). Marine photosynthetic primary producers assimilate nutrients dissolved in seawater: nitrogen (N), phosphorus (P), silicon (Si), and micronutrients, along with carbon (C) available from dissolution of atmospheric carbon dioxide, to synthesise organic compounds necessary for their metabolism and growth.…”