Peruvian upwelling plankton respiration: calculations of carbon flux, nutrient retention efficiency, and heterotrophic energy production

[摘要] Oceanic depth profiles of plankton respiration are described by a powerfunction, R_CO2 =(R_CO2)₀ (z/z0)^b, similarto the vertical carbon flux profile. Furthermore, because both oceanprocesses are closely related, conceptually and mathematically, each can becalculated from the other. The exponent b, always negative, defines themaximum curvature of the respiration–depth profile and controls the carbonflux. When |b| is large, the carbon flux (F_C) from theepipelagic ocean is low and the nutrient retention efficiency (NRE) is high,allowing these waters to maintain high productivity. The opposite occurs when|b| is small. This means that the attenuation of respiration in ocean watercolumns is critical in understanding and predicting both verticalF_C as well as the capacity of epipelagic ecosystems to retaintheir nutrients. The ratio of seawater R_CO2 to incomingF_C is the NRE, a new metric that represents nutrient regenerationin a seawater layer in reference to the nutrients introduced into that layervia F_C. A depth profile of F_C is the integral ofwater column respiration. This relationship facilitates calculating oceansections of F_C from water column respiration. In an F_Csection and in a NRE section across the Peruvian upwelling system we found anF_C maximum and a NRE minimum extending down to 400 m, 50 km off thePeruvian coast over the upper part of the continental slope. Finally,considering the coupling between respiratory electron transport systemactivity and heterotrophic oxidative phosphorylation promoted the calculationof an ocean section of heterotrophic energy production (HEP). It ranged from250 to 500 J d⁻¹ m⁻³ in the euphotic zone to less than5 J d⁻¹ m⁻³ below 200 m on this ocean section.

[学科分类] 地球化学与岩石