Food web dynamics in coastal vegetated habitats of the Southern Gulf of Mexico

Abstract

This dissertation aimed to study the food web dynamics and fish assemblage connectivity in different coastal settings in the microtidal portion of the Southern Gulf of Mexico comprised by the Centla Wetlands Biosphere Reserve and the Terminos Lagoon Protected Area. Based on stable isotope analysis (A 13C, A 15N) of riparian and aquatic basal resources, and representative consumer taxa in four study sites located 26, 25, 13 and 1 km from the coast, the overall hypothesis was that the importance of riparian-derived carbon (from marsh and/or mangrove vegetation) for aquatic consumers is highly variable across spatial scales, and that the periodic dry and wet conditions in the area (the later influenced by strong northerly winds) drive the major changes in resource availability and the connectivity of aquatic food webs. Results suggest that the role as feeding areas of coastal vegetated habitats varies across spatial and temporal scales. While the variation at the spatial scale has to do with factors like geomorphology, distance to the sea and availability of resources, the temporal variation (at the seasonal scale) relates with flood pulses (river-influenced areas) and the effect of winds (marine-influenced area). Finally, emphasis is given to the importance of habitat heterogeneity and seasonal environmental forces, particularly rain, in enhancing the connectivity of fish assemblages through freshwater runoff in river-influenced areas, making these sites attractive feeding areas for an array of marine species migrating into these productive systems. However, the role that wind exerts on this connectivity merits further consideration. This work contributes to the body of research addressing the different basal resources to aquatic consumers and food web connectivity in tropical coastal regions, as well as the specific importance of riparian-derived carbon in different ecosystems and under contrasting seasonal influences. This knowledge can be useful for management and conservation, particularly in face of the vulnerability and degradation of spatially and temporally complex ecosystems like Centla Wetlands and Terminos Lagoon.