Evaluation of zooplankton potential CO2 production: isocitrate dehydrogenase (IDH) enzyme activity

Abstract

Isocitrate dehydrogenase (IDH), a CO2 producing enzyme, plays a key role in the Krebs cycle, being responsible for the emission of one of the three CO2 molecules related to this central phase of cellular respiration. Using a modified IDH methodology, we have assayed IDH activity in the marine planktonic community and have calculated its potential CO2 production. This measure will improve estimations of the impact of plankton on ocean carbon flux and carbon sequestration in the deep ocean. Samples of different plankton fractions (from 0.7 to 50 µm, from 50 to 200 µm and from 200 to 2000 µm) from the Canary Island coastal waters were used to develop and validate this method. Although more experiments are needed, this methodology is leading to a better understanding of cellular respiration in marine samples. Thus, other points of view about the role of plankton communities within the food chain, new knowledge about vertical carbon flux and new estimations about the current sequestering capacity for anthropogenic CO2 by these plankton communities are emerging.