Water quality as a regional driver of coral biodiversity and macroalgae on the Great Barrier Reef

Poor water quality significantly degrades coral biodiversity and promotes macroalgae growth on the Great Barrier Reef (GBR), according to a large-scale study. The research found that inshore reefs, characterized by lower water clarity and higher chlorophyll levels due to runoff, exhibit reduced richness in hard corals and phototrophic octocorals while experiencing a fivefold increase in macroalgal cover compared to offshore regions. Water quality explained 18–46% of the variation in these biotic groups, with spatial patterns also playing a role. The study identifies potential water quality guidelines—Secchi disk depth >10 meters and chlorophyll <0.45 g/L—that correlate with low macroalgal cover and high coral richness. Improving water quality on 23% of GBR reefs currently exceeding these thresholds could reduce macroalgae by 39% and boost hard coral and phototrophic octocoral richness by 16% and 33%, respectively, offering a target for pollution reduction strategies.

De’ath, G., & Fabricius, K. (2010). Water quality as a regional driver of coral biodiversity and macroalgae on the Great Barrier Reef. Ecological Applications, 20(3), 840–850. Portico. https://doi.org/10.1890/08-2023.1