Functional and Structural Food Web Comparison of Terminos Lagoon, Mexico in Three Periods (1980, 1998, and 2011)

Terminos Lagoon has a high diversity of species and habitats and is the largest coastal lagoon in the southern Gulf of Mexico. It has been a natural protected area since 1994, but in recent decades, environmental changes have modified its biological communities and habitats. In this study, we construct three trophic models for the periods 1980, 1998, and 2011 using the Ecopath with Ecosim approach to evaluate the status of the ecosystem. Based on model outputs, we compare functional indicators and perform a structural analysis of the food web. We found significant changes in the biomasses of trophic compartments and in other functional indicators. The global productivity of the ecosystem was the main ecosystem indicator that changed over time. The structural analysis included a collection of centrality indices which measure the number, strength, and distance (in terms of number of links) of linkages between each trophic compartment and all other compartments, as indicators of the relative importance of each compartment in overall energy flows. Structure was also assessed by identifying the number and composition of subgroups connected by strong trophic linkages. Certain compartments from lower trophic levels, such as seagrasses, microcrustaceans, meiobenthos, and echinoderms had the higher values of centrality measures in the three periods analyzed. Substructures were relatively stable between periods, confirming that a reduction in productivity was the main ecosystem indicator that changed over time. Some trophic compartments were recurrent in substructures, revealing their key role in the food web structure regardless of changes in productivity. This analysis suggests that those compartments must be prioritized in conservation scenarios because the loss of those species would change the ecosystem structure impacting severely its biological productivity.