Ocean Optics and Biogeochemistry Protocols for Satellite Ocean Colour Sensor Validation Volume 7.0. Aquatic Primary Productivity Field Protocols for Satellite Validation and Model Synthesis.

Abstract

The measurement of aquatic primary productivity (PP) is central to the quantitative understanding of the global biosphere, yielding critical insights into the role and magnitude of carbon, oxygen, and other bioactive element fluxes between the ocean, the geosphere, and the atmosphere. The accumulation of theoretical, methodological, and technological advances has led to the development of numerous approaches to measure oceanic PP, all with the common objective of quantifying the fluxes of reduced carbon into aquatic ecosystems. Methods to derive estimates of PP include, the analysis of incubations to measure dissolved oxygen gas accumulation and consumption, radioactive 14C, stable 13C, and 18O uptake, isotopic composition of atmospheric and dissolved oxygen, underway measurements of O2/Ar, kinetic measurements of variable chlorophyll fluorescence, and temporally and spatially integrated time series from gliders or buoys. Integrating these measurements with satellite observations of ocean biomass and its physical environment enable the scaling up of PP data into a comprehensive, global picture. The main goal for these PP protocols is to establish a set of best practices across multiple methods for measuring aquatic primary productivity, in an effort to constrain systematic and random measurement biases. Through a better understanding of the different capabilities, assumptions, and limitations inherent to each measurement, users may leverage the assets and liabilities of each method in the context of satellite validation and model synthesis.