Characteristics of Benthic Toxic Dinoflagellate Communities within Three Coastal Regions of the Great Barrier Reef, Australia

Abstract

Benthic dinoflagellates are fundamental to marine ecosystems, contributing to marine food webs, species interactions, and community diversity. They are also known to produce a range of biotoxins that are harmful to humans and wildlife. Our study demonstrates that benthic dinoflagellates exhibit significant spatial variability in their distribution and diversity across three coastal regions of the Great Barrier Reef, Australia. High-throughput sequencing targeting the V8–V9 region of the 18S rRNA gene identified distinct benthic toxic dinoflagellate assemblages shaped by regional and habitat associations. Genera, including Amphidinium, Coolia, Gambierdiscus, Ostreopsis, and Prorocentrum, were detected across multiple regions, highlighting their potential risk to seafood safety, wildlife and ecosystems. Strong correlations between genera such as Gambierdiscus and Coolia suggest shared environmental preferences, as well as potential interspecies interactions, that may influence benthic bloom dynamics. Additionally, the presence of traditionally planktonic toxin-producing genera, such as Alexandrium, Azadinium, Karenia, and Gonyaulax, highlights their ecological plasticity and potential role in toxin accumulation within benthic environments. In addition, habitat characteristics, including benthic substrate type and riverine influence, significantly shape benthic dinoflagellate distributions. These findings contribute to the growing understanding of benthic toxic dinoflagellate ecology and highlight the need for targeted monitoring and management strategies to mitigate the associated risks. By integrating DNA metabarcoding with ecological assessments, this study provides a valuable framework for future research on toxic dinoflagellate dynamics in benthic environments and their environmental drivers in tropical and subtropical marine ecosystems.

Keywords: biotoxins, eDNA, Harmful Algal Blooms (HABs), metabarcoding, microalgae, Queensland