Winkler iodometric determination is a reference method for the measurement of dissolved oxygen (DO) in waters. This methodology allows the determination of Gross Primary Prduction (GPP), Net Community Production (NCP) and Community Respiration (CR) produced by the plankton community. Community Respiration and NCP are calculated from changes in DO concentrations, before and after incubation of samples in dark and transparent conditions respectively. GPP is calculated as NCP + CDO. DO concentrations are determined by automated high-precision titration. Measurements are performed with a Mettler Toledo Autotritator M 50 (using calibrated potentiometric electrodes and automated end-point detection). With these methods, we achieve an estimate of the variation and biogeography of the pelagic community.
The Mettler Toledo Autotritator allows for fully automated high-precision titration, required for oxygen analyses and alkalinity measurements. Whereas the Methron autotitrator can do the same analysis the advantage of the Mettler Toledo instrument is that it can handle more than 8 samples in a carrousel sampling system and can handle the leaders, allowing for fast throughput of samples.