Plankton Respiration from the Cellular to the Basin Scale

Estimates of marine plankton respiration provide an important constraint on the magnitude of the biological carbon pump and global elemental nutrient cycles, yet respiration remains one of the least constrained terms in models of metabolism, gas exchange and carbon mass balance. This is due in part to the difficulty in measuring both total oceanic respiration and that attributable to specific plankton groups or size classes and the resulting lack of earth observation algorithms. Respiration in the surface layer of the ocean is usually estimated from either the consumption of dissolved oxygen in a contained sample volume or from enzymatic proxies such as INT, and is less frequently determined from mixed layer oxygen utilisation, allometric equations or biomass / abundance spectra.

As part of a tracer release (SF6) experiment in the Mauritanian upwelling and a seasonal study of UK shelf sea biogeochemistry, we measured plankton respiration using a range of methods which span time and space scales from cells to the mixed layer and hours to years. This presentation will compare and contrast these concurrent measurements with a view to assessing the range of variability in respiration relative to that in primary production alongside measures of parameters such as plankton community structure and organic carbon availability which may lead to this variability. In addition, by comparing between systems and between seasons in the same system, and utilising the available global dataset, we aim to test predictive empirical models of respiration in an attempt to extrapolate to the basin scale.