3 - Lab-based sampling techniques

This module introduces the main lab-based sampling techinques that are performed on board to measure and understand ocean biogeochemistry and ecology. Lab-based analysis still represents the reference techniques for acquiring high-quality datasets to validate instrument measurements and investigate changes in the carbonate system within the ocean interior. This module illustrates sampling and preservation techniques for samples used in carbonate system analysis, as well as the laboratory analysis of pH using the spectrophotometric method, with hands-on training included.
Lab-based sampling techniques are essential for the accurate taxonomic identification and classification of phytoplankton and zooplankton collected during oceanographic surveys. Following field collection, samples are preserved (typically in formalin or ethanol) and analyzed under stereomicroscopes and compound microscopes by trained taxonomists. These methods enable the detailed identification of plankton to the lowest possible taxonomic level, often down to species. Laboratory analyses provide critical data on biodiversity, community composition, and population structure, serving as a reference for validating automated or image-based classification systems. Despite being time-consuming, taxonomic expertise remains fundamental to understanding ecosystem dynamics and supporting long-term biodiversity monitoring.
Finally, lab-based sampling techniques applied to acquire information about phytoplankton pigments and optical properties; nutrient concentrations and dissolved organic matter are also presented and described.