Resolving Bottom-Up and Top-Down Food-Web Structure and Function for Everglades Restoration

Many ecosystem functions and services that sustain biodiversity and human well-being are rooted in food-web processes, yet food-web studies often fail to integrate multiple ways of quantifying trophic links or to clearly distinguish top-down from bottom-up effects. To address these gaps in support of on-going Everglades restoration, we combined diet data with studies quantifying top-down effects to construct a high-resolution energetic food web for freshwater marshes. Our goal was to identify highly connected nodes relevant to restoration and to evaluate how bottom-up and top-down links interact to shape community structure and ecosystem function. Our review compiled diets for 107 consumers from 82 publications, revealing a food web reliant on detrital-based energy pathways, with notable exceptions for some invasive fishes. The detrital-energy pathway was characterized by highly connected consumer nodes including amphipods, grass shrimp (Palaemon paludosus), and cyprinodontid fishes. Most indicators of restoration success, like American alligators (Alligator mississippiensis), were highly connected. Comparisons of dynamic and energetic links indicated that strong top-down effects often occurred between consumer-resource pairs with weak energetic links; diet importance for predators failed to predict strength of population dynamic effects for prey. Further, top-down effects of some invasive fishes may limit bottom-up effects of Everglades restoration. Using both types of information and visualizing yielded a more complete, though still imperfect, food web, which can better inform ecological restoration strategies. In the Everglades, this means improving resolution for indicator species (higher predators) combined with understanding limitations of their prey and food-web responses to hydrologic and biogeochemical drivers.