Stability characteristics and interaction strength combinations of a shallow water trophic model in Crandon Park, Biscayne Bay, Florida

Abstract

The eastern coast of Key Biscayne is bounded by a shallow water ecosystem typical of of the Florida Reef Tract with patchy hard and soft substrates dominated by macroalgae, sponges, and patches of seagrass. These areas are subject to disturbances associated with urbanization, and are particularly vulnerable to contamination from sources such as land runoff and oil spills. In order to understand the complexity of the ecosystem functioning and predict the consequences of anthropological pressures, a trophic model and an interaction strength food web were developed for waters from 0.5-3.5 m depth off Crandon Park, at the northeastern tip of Key Biscayne. Monte Carlo analyses of interaction strengths indicated that simple and omnivorous tritrophic food chains (those involving three species) occurred less frequently than expected by chance. This indicates that the stability of the food web is highly dependent on a restricted set of species on the lower and upper ends of these food chains for which changes in abundance can lead to cascading effects through the ecosystem. These results differed from a previous analysis of a lower resolution Caribbean food web in which omnivorous tritrophic chains occurred more frequently than in randomized food webs