Ecological Drivers of Taxonomic and Functional Beta Diversity in Demersal Fish Communities of Northeastern Brazil: Implications for Marine Spatial Planning

The northeastern Brazilian continental shelf harbors diverse demersal fish communities that play essential roles in local fisheries and ecosystem functions. This study investigates taxonomic and functional β-diversity across depth and substrate types, analysing data from 62 trawling stations (from 5° to 9° S) and over 7,000 specimens representing 127 species. We computed β-diversity indices, specifically species turnover and nestedness measures, to examine how community composition varies with environmental and spatial gradients. Our results indicate that species turnover is the primary driver of taxonomic β-diversity, with distinct changes in species composition across stations. In contrast, functional β-diversity was generally high, with turnover and nestedness contributing equally. However, for functional β-diversity based on abundance data, overall diversity was low, suggesting that while functional composition differs between stations, the relative abundances of these species remain similar. Substratum complexity, depth, and particle dispersion gradients significantly influence β-diversity, supporting taxonomic and functional diversity in this region and maintaining essential functions such as resilience in nutrient cycling and energy flow. Integrating β-diversity metrics into Marine Spatial Planning (MSP) enables more effective targeting of habitats crucial to ecosystem function and resilience. Depth-stratified protection zones, for example, could benefit functionally diverse yet vulnerable habitats, particularly in deeper areas at risk of species and trait loss. Such MSP strategies align conservation and sustainable resource use, safeguarding the ecological roles and biodiversity of demersal fish communities on the northeastern Brazilian shelf.