Development of an agent-based model to assess the role of mesozooplankton community structure and diel vertical migration in fecal pellet carbon flux

The effect of zooplankton community structure, feeding behavior, and diel vertical migration (DVM) on fecal pellet carbon flux was investigated using an individual based model of two contrasting open ocean regions: an oligotrophic (Hawaii Ocean Time-series site ALOHA) and a mesotrophic (Japanese time-series site K2) system. Fecal pellets are usually a significant component of the total particulate organic carbon (POC) flux and a key component of the biological pump, thus accurately representing fecal pellet flux in biogeochemical models is important. Data from the VERtical Transport in the Global Ocean (VERTIGO) project was used to parameterize the model, and model outputs of fecal pellet flux were compared to field-derived sediment trap data to examine how community structure and DVM impact fecal pellet carbon flux in the water column. Results show that primary production at ALOHA is not high enough using a purely herbivorous feeding model to support the magnitude of fecal pellet flux measured by sediment traps, indicating carnivory and aggregate feeding by zooplankton also support a large component of zooplankton metabolism. Zooplankton DVM resulted in fecal pellet fluxes that are closer to field values at both locations, with DVM more important at K2 vs ALOHA. The importance of agent-based models and the inclusion of zooplankton community structure and DVM are discussed, in addition to future goals of predicting fecal pellet and total POC flux in other projects like EXport Processes in the Ocean from Remote Sensing (EXPORTS).