The use of image analysis systems for the assesment of zooplankton physiological rates and carbon fluxes

Abstract

Measuring zooplankton physiological rates is of paramount importance in biological oceanography in order to assess the role of this community in e.g., carbon fluxes. Classical methods (incubations) are highly time-consuming and impractical to match physical and chemical measurements in oceanography. Attempting to solve this, a variety of methods (egg production, RNA/DNA ratio, enzyme activities, etc.) have evolved over the last decades. These methods also show many uncertainties and hitherto only in- cubation methods have been widely accepted. Predictive equations relating physiological processes and body weight and temperature, are a rough alternative normally used to ascertain the role of these organ- isms in the ecosystem. However, using imaging systems and empirical relationships to determine body weight allow the application of physiological models to each individual, obtaining reliable estimations for taxonomic groups and size classes. In this study, the physiological rates assessed from predictive equations in combination with an image-based analysis system (ZooImage) were compared with enzy- matic methods. We observed a consistent agreement between both methodologies, the former resulting a faster procedure for the appraisal of community carbon fluxes in large spatial and temporal scales.