Variability of respiration and pyridine nucleotides concentration in oceanic zooplankton

We have studied the in vivo respiratory oxygen consumption (RO2) and the potential respiration rates (Phi), measured by the enzymatic activity of the electron transport system (ETS), in epipelagic marine zooplankton from several marine systems. Furthermore, we have determined the intracellular concentration of the ETS substrates, i.e. the pyridine nucleotides (PNs), in these organisms. Both the RO2 and Phi and the relationship between them (RO2/Phi) showed a major dependency on habitat temperature, with significantly higher values in the warm waters of North Atlantic. Conversely, the pattern described by the PN concentration was mainly associated with the productivity regime that ultimately determined the food availability for the zooplankton. We further studied seasonal variability of the RO2, Phi and PN concentrations in the coastal waters of the Canary Islands. Larger values were measured during the late winter bloom period, whereas they decreased between 30 and 40% with the stratification of the water column. Shedding light on the processes that drive the respiratory control at the physiological level will help in understanding the variability of the respiration rates in marine organisms as well as the impact that these rates have on the remineralization of the organic matter.