The role of avoidance by zooplankton for survival and dominance of toxic phytoplankton

In aquatic systems, the dominance of toxic phytoplankton has become an area of growing concern in recent years. In this article, we develop and analyze a model with three interacting species, toxic and non-toxic phytoplankton as well as zooplankton, including the effect of avoidance of zooplankton for the toxic phytoplankton in the presence of non-toxic one. We find that avoidance does not only promote the survival of the toxic phytoplankton population, but it also plays an important role for its dominance over its competitors. Additionally, it is observed that high avoidance helps to support the coexistence of toxic phytoplankton, non-toxic phytoplankton and zooplankton.

► Zooplankton show an avoidance tendency towards ingesting toxic species.
► Avoidance may result in coexistence of toxic phytoplankton, non-toxic phytoplankton and zooplankton.
► Avoidance helps toxic species to survive and form HABs.