Multi-proxy assessment of coral reef formation and biotic-abiotic diversity in an urban coastal reef ecosystem in northeastern Brazil

Abstract

Coral reefs are habitats with high animal and mineral diversity and are subject to both climate change and anthropogenic impacts. This article presents novel and relevant data on the Seixas coral reef environment's geological, sedimentological, mineralogical, and biotic aspects in Paraíba State, northeastern Brazil. The aim of this study is to evaluate the processes of reef formation and the diversity of coral reef species in urban coastal environments in northeastern Brazil using a multi-proxy approach. Materials and methods employed to analyze the formation and diversity of biotic and abiotic species include (a) bathymetric survey, (b) collection of sedimentological, mineralogical, and granulometric data, (c) geological and stratigraphic determination, and (d) identification of biotic and abiotic species. Mineralogical slide results reveal that the Seixas Reef is a recent biogenic coral-algal carbonate formation associated with coastline evolution, high coastal sedimentation, and changes that occurred alongside sea-level rise (Holocene-Quaternary period). The diversity results indicate that benthic organism settlement occurred on a consolidated arenite base, with the fauna undergoing continuous succession processes. It can be concluded that this coral reef is highly vulnerable due to the material of its formation and comprises subsectors with high diversity (fore reef) and others with low diversity (reef top), which are affected by both anthropogenic and natural factors. Studies of this nature can contribute to understanding the evolution of coastal reefs, as their proximity to the continent makes them more vulnerable, and they experience direct physical impacts from fishing and tourist activities.