Relationships between environmental heterogeneity and fish beta diversity in a tropical bay

Estuarine shallow waters have many habitats favouring the colonization and establishment of different fish species. Our study investigated the variability in the composition of these communities by examining beta diversity and evaluated the relationship between fish beta diversity and environmental heterogeneity, which can be dependent on the level of human alteration to which an ecosystem is exposed. Our goal is to provide insights not only on the biodiversity, but also to help develop effective conservation measures. We sampled fish and environmental variables (physicochemical water variables and sediment nutrients and granulometry) in three zones (inner, middle and outer) of Sepetiba Bay, in Southeastern Brazil. The aims of our study were to compare fish communities in the different zones by using beta diversity and to investigate the relationship between environmental heterogeneity and beta diversity. Habitat conditions varied considerably among the zones. Relationships between species and environmental conditions were species-specific, and a weak positive correlation between environmental heterogeneity and beta diversity was found. The highest beta diversity was detected in the inner bay zone, suggesting that relatively more urbanized areas had greater environmental heterogeneity and, thus, higher beta diversity. Our results serve as a 'caution' to reduce the urbanization effects on these environments that sometimes can increase habitat heterogeneity and species richness. The 'weak' relationship suggest that the ecosystems may have been in the 'early stages' of human influences and managers should take into account that anthropogenic impacts would reduce beta diversity because continued degradation would lead to natural habitat reduction. http://zoobank.org/urn:Isid:zoobank.org:pub:EBBEA81F-6D4D-4CB3-8796-7E2A578A8B03

Automated summary

This study investigated the variability in fish community composition and its relationship with environmental heterogeneity in estuarine shallow waters. The results showed that more urbanized areas had greater environmental heterogeneity and higher beta diversity, suggesting the need to reduce urbanization effects on these habitats for effective conservation measures.