Theoretical blooming mechanisms for Cochlodinium polykrikoides in a coupled population dynamics and ecosystem model

Abstract:

Cochlodinium polykrikoides is a species notorious for causing Harmful Algal Blooms resulting in substantial damage to aquaculture and fishery industries off the coast of Korea. To understand the ecological-physical interactions underlying blooms, we have developed a simple ecosystem model which couples a population dynamics model for C. polykrikoides with the Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD) general ocean ecosystem model. Theoretical studies are conducted using the governing equations. Steady-state solutions for models that omit zooplankton show that C. polykrikoides are defeated by phytoplankton (diatom) in nutrient resource competition. Similar to previous studies using numerical simulations, C. polykrikoides can be successful when zooplankton that have prey preferences for diatoms are included in the model. Theoretical analysis shows that C. polykrikoides can exist only when the total nutrient concentration (defined as sum of all state variables) is larger than a defined threshold. We analytically determine the nutrient concentration threshold and discuss details of the population dynamics underlying C. polykrikoides blooms in the marine ecosystem.