Our research involves the study of the metabolic budget of the ocean and different chemical oceanographic parameters. For this work, we collaborate with the Analytical Core Lab of KAUST.



Oxygen measurements - metabolism

Winkler iodometric determination is a reference method for the measurement of dissolved oxygen (DO) in waters. This methodology allows the determination of Gross Primary Production (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 biogeograp​hy of the pelagic community. It allows for fully automated high-precision titration, required for oxygen analyses and alkalinity measurements. The Mettler Toledo instrument can handle more than 8 samples in a carrousel sampling system, allowing for fast throughput of samples.


Alkalinity measurements

This is an important parameter for understanding the carbonate system in sea water. It is a parameter that can be combined with additional parameters, e.g., pH, CO2, or dissolved inorganic carbon (DIC), to determine other parameters. Alkalinity measurements could be done with two titrator systems:

  • Apollo SciTech's AS-ALK2: Automates the titration procedure by controlling titration and standardization, and the calculation of the final result. This system uses small sample volumes (5-25 mL) with high precision (0.1%). This allows for fast throughput of samples. It also provides full scale pH titration and full temperature control.
  • Metler Toledo Autotritator M50: Measurements can be taken in an open flask after calibrating the electrode pH 4.4 (scale NBS) by utilizing potassium phthalate buffer borax. By interleaving steps of Certified Reference Material (CRMs) between samples, this method can achieve precisions and accuracies of the order of 1-2 mol / kg micro.