Trophic modeling of the continental shelf ecosystem outside of Tabasco, Mexico: A network and modularity analysis

The continental shelf of the southern Gulf of Mexico is influenced by a critical riverine basin that serves as a productive area for economic activities, notably fishing and oil extraction activities. The area is thus subjected to multiple uses, and this can alter the structure and functioning of the ecosystem. Hence, the assessment and sustainable use of natural resources requires the consideration of complex trophic interactions in the ecosystem. This study characterizes the structure and function of the continental shelf ecosystem food web outside of Tabasco, Mexico. Meaningful compartments with strong trophic interrelationships that may be of relevance to the sustainability of the ecosystem were also identified using a modularity maximization algorithm. The Ecopath approach is employed to construct a trophic model with 33 functional living groups and a detritus pool. Barracudas and sharks are found to be the main predators. Detritus also plays an important role in the food web, as this group supplies half of the system's primary energy supply and has significant positive mixed trophic impacts on several functional groups. A constant supply of organic matter via continental discharge reinforces the important role of detritus while limiting matter recycling in the ecosystem. A high degree of omnivory in the food web also forms intricate trophic relationships. According to ecosystem indices, the ecosystem is well organized, and this is also evident given the presence of three meaningful compartments in the food web. Flows within compartments were higher than between them. These compartments include heterogeneous functional groups and may prove central to the resilience of the ecosystem. Two compartments include groups from the base of the food web, one included primary and secondary producers from the sea bottom and the other comprised groups from the water column. (C) 2015 Elsevier B.V. All rights reserved.