Conclusions: NUTRIENT RETENTION EFFICIENCY, A NEW OCEAN METRIC FROM PLANKTON RESPIRATION & CARBON FLUX T.T. Packard, N. Osma, I. Fernández-Urruzola, F. Maldonado, I. Martinez, A. Herrera, M. Tamés-Espinosa, V. Romero-Kutzner, E. Bru, M. Gómez Grupo de Ecofisiología de los Organísmos Marinos (EOMAR). Facultad de Ciencias del Mar, Universidad de Las Palmas de Gran Canaria, Campus Universitario de Tafira, 35017 Las Palmas de G.C., Canary Islands, Spain. (
[email protected]) NRE Calculation from Respiration NRE is the nutrient remineralization rate within an ocean layer normalized by nutrients entering that layer via particle flux. Below the euphotic zone it can be calculated as the inverse of the carbon-flux transfer efficiency. Also, it can be calculated from aplankton respiration profile (and the Redfield ratio). In the euphotic zone it is essentially the respiration to productivity ratio. Conceptual Basis Ft-s = [Rt/((b+1)(zt)b]*[(zs(b+1)] - (zt(b+1)] Box 1.-Carbon Flux Working Equation. Rtis the respiration at the respiration maximum, bis the exponent on the power function, ztis the depth of the layer through which the carbon will flux, and zsis the bottom depth (sea floor). Microplankton CO2production decreases vertical particle flux by releasing DOC & DON! ABSTRACT Nutrient retention efficiency (NRE) is anew metric to quantify the capacity of an ocean layer to maintain its nutrients.Conceptually, it is the remineralization of inorganic nutrients associated with respiratory CO2production (RCO2)within an ocean layer normalized by nutrients fluxing into that layer.It can be expressed as aratio or apercent.Operationally, below the euphotic zone, it can be calculated either as the ratio, RCO2/(carbon flux) associated with an ocean layer or the inverse of the carbon-flux transfer-efficiency through that layer.Furthermore, it is related to the maximum curvature (b) of the respiration-depth function [RCO2= (RCO2)0z-b]. NRE increases when the absolute value of bincreases.NRE associated with microplankton can be calculated from microplankton-ETS depth-profiles.NRE associated with zooplankton can be calculated from zooplankton-ETS depth-profiles.Conceptually total NRE equals the sum of the NREs associated with allplankton fractions.In the Peru upwelling the NRE, associated with the microplankton, displayed aminimum 40 km seaward of the upwelling center over sediments calculated to have high benthic respiration. Formazan produced from tetrazolium (INT) in the ETS assay “counts electrons”. Reaction strength is proportional to the red color. 1. NRE = (R in any ocean layer)/(Total water-column R from euphotic-zone bottom to sea floor.) 2. Exponent (b), the curvature of R=f(z), controls particle flux & NRE 3. Low water column NRE leads to high benthic respiration and carbon burial. POC, N, P Flux in O2 CO2(RCO2) NH4+(RNH4+) PO4-(RPO4-) POC, N, P Flux out EFFICIENCY WITH WHICH PLANKTON MINERALIZE POM Permits nutrient recycling! NRE =(∆POM Flux)/(Flux in) (Ct-s )1=(d(POC)/dz) d(CO2)/dz) = RCO2 (Ct-s)2 NRE = RCO2/(Ct-s)1 CUEA C-Line off 15°S Peru 0 0,5 1 1,5 2 2,5 020 40 60 DEPTH (km) NRE (R/Fc x 100) Station 16 (C14) Rz= Rt(z/zt)-b Curvature, “b”, is the key to understanding particle flux and NRE! R/V T G THOMPSON (U WASH)