Virtual aquatic ecology: stepped simulations of gross production within constraints explain biomass changes

A simulator, ECOLPS in R, is developed and trialed for ecological studies of closed aquatic ecosystems. Its constraint-based approach contrasts with function-based models widely applied in ecology. Total gross production ({Sigma}GP) by wild components (= species/life stages, grouped by ecological roles) is maximized within constraints over short time steps using linear programming, thereby enabling simulations of opportunistic growth and harvesting by competing components. Constraints use integrated terms from an [n]-component generalization of the Lotka-Volterra (LV) predator-prey model, and from mass-based models for fisheries, non-living organics, nutrients and essential habitats. Seasonality uses programmed temperature and light indices. Trial simulations, total 12, sought first to confirm conformance with LV theory. Further trials of gradually increasing ecosystem complexity were designed to simulate wellknown ecological events. They found biomass oscillations depending on starting biomasses and seasons, predator satiation, competitive exclusion, predator diets dependent on available prey, instability of unconstrained 3-level food chains, limitation of GP by essential habitats and nutrients, recycling of nutrient and biomass, trophic cascades and wasp-waist systems caused by fishing, and seasonal succession. Step-wise studies of simulated series explained results. A constrained-GP hypothesis is proposed. Priorities for further developments are suggested. ECOLPS simulations could support cause-and-effect investigations, field work, and aquatic ecological risk assessments.