THE ROLE OF HABITAT COUPLING BY ZOOPLANKTON DRIVING POPULATION DYNAMICS AND STABILITY IN SHALLOW LAKES

Abstract

Studies of population stability in shallow lakes are yet to explain how fishless ponds, with high algae productivity, can have stable zooplankton-algae populations throughout the year. These studies have traditionally overlooked the role of benthic-pelagic coupling, a phenomenon that has noticeable effects on population stability in aquatic environments. We analyzed a simple model to show that benthic-pelagic habitat coupling can explain discrepancies between the behavior of classical predator-prey models and the patterns observed in natural aquatic systems. We used a Lotka-Volterra type model of zooplankton and algae, explicitly modeled as phytoplankton and periphyton. Zooplankton could eat in both algal compartments, presenting a multi-chain omnivore configuration, whereas phytoplankton and periphyton engage in exploitative competition as system support capacity increases. We also modeled the algal exchange among compartments. Our model results show that (1) zooplankton—algae systems tend to be stable up to high nutrient values at intermediate degrees of omnivory, that (2) algae exchange among compartments may dampen stability and that (3) exploratory competition between phytoplankton and the periphyton can also decrease stability. The model results are supported by empirical results available in the literature. Despite the limitations of the modeling approach, our results emphasize the role of habitat coupling and contribute to deepening the understanding of the processes and mechanisms capable of promoting the stability of population dynamics in shallow lakes