Biogeochemical Implications Of Diel Changes In Migratory Copepod Physiology

The diel vertical migration (DVM) of zooplankton and fish across hundreds of meters between shallow and deep waters is a predominant pattern in pelagic ecosystems. DVM has consequences for biogeochemical cycling as it moves a substantial portion of surface fixed carbon and nitrogen directly to depth. Despite the acknowledged biogeochemical importance of this “active flux”, these contributions remain poorly constrained, in part because daily variations in metabolic rates are not considered or are modeled as simple functions of temperature. This project uses transcriptomic, proteomic, physiological and biochemical methods to characterize the metabolic consequences of daily physiological rhythms and DVM for a model zooplankton species, the abundant subtropical copepod Pleuromamma xiphias. We sampled copepods at 6-hour intervals during their migratory cycle and measured organisms continuously for 48 hour periods to correlate underlying diel rhythms in physiology with functional pathway profiles. Through these efforts, we find significant variation in the production rate of a number of biogeochemically relevant products and reveal the functional pathways involved. By pairing distributional studies with the organismal metrics we explore and discuss the potential biogeochemical implications of underlying circadian changes in zooplankton physiology.