Modeling time-varying phytoplankton subsidy reveals at-risk species in a Chilean intertidal ecosystem

The allometric trophic network (ATN) framework for modeling population dynamics has provided numerous insights into ecosystem functioning in recent years. Herein we extend ATN modeling of the intertidal ecosystem off the central coast of Chile to include empirical data on pelagic chlorophyll-a concentration. This intertidal community requires subsidy of primary productivity to support its rich ecosystem. Previous work models this subsidy using a constant rate of phytoplankton input to the system. However, data shows pelagic subsidies exhibit short-term, highly variable, pulse-like behavior. Incorporating this variable input into ATN modeling is the primary contribution of this work and provides several new insights into this ecosystems response to pulses of offshore phytoplankton, including: (1) closely related sea snails show differential responses to pulses of phytoplankton that are explained by underlying network structure; (2) increasing the rate of pelagic-intertidal mixing increases fluctuations in species biomasses that may increase the risk of local extirpation; (3) predators are the most sensitive species to phytoplankton biomass fluctuations, putting these species at greater risk of extirpation than others. Finally, our work provides a straightforward way to incorporate empirical, time-series data into the ATN framework that will expand this powerful methodology to new applications.