Resource depletion and mechanisms for food web robustness in a Neotropical estuary

Human activities severely threaten biological communities in Neotropical estuaries. Nevertheless, these communities have been poorly studied in comparison to low biodiversity regions, despite the fact that conservation efforts in these habitats are expected to require longer time-scales and greater efforts. In the present study we simulated resource depletion in a consumer–resource food web in a high-diversity Neotropical estuary. We first describe the feeding patters of local assemblages, split across distinct upper and lower estuary habitats. Further, because fish are opportunistic consumers of locally abundant prey, we modelled community robustness using resource availability, number of resources consumed, consumption diversity and environmental constraints. We found different feeding patterns between the upper and lower estuary habitats. Although crustaceans and detritus were preferably consumed in both habitats, thorough identification demonstrated higher dissimilarity between sites of different habitats relative to sites within the same habitat. We found that community robustness has a positive relationship with consumption diversity and that habitat type (upper or lower estuary) was a poor predictor of robustness. However, the modelling results also indicated an interaction between consumption diversity and habitat type. This suggests that promoting spatial gradients across resources, abiotic conditions and local feeding patterns within habitats can help protect against human-mediated disturbances.