More coral does not fully rescue fish richness when algae also gains ground
WHAT THE EVIDENCE SAYS
Using a global reef dataset spanning 2006–2023, researchers tested how low-lying algae and macroalgae altered the relationship between live hard-coral cover and fish species richness. Both algal groups weakened the positive coral–fish richness relationship. Low-lying-algae effects were evident where coral cover was below about 45%, while macroalgal effects persisted until roughly 65% coral cover. Sensitivity also varied with fish diet and body size.
WHY IT MATTERS / OUR READ
Coral cover is not a sufficient condition metric by itself. Two reefs with similar coral cover can carry different fish-diversity prospects if algal state and functional composition differ.
CAVEATS / UNCERTAINTY
The reported coral-cover values are statistical context thresholds from an observational global dataset, not universal management trigger points. Species richness does not capture abundance, biomass or ecosystem function, and associations do not establish that reducing algae alone would restore fish richness.
SOURCE
Conservation Biology — primary study
View original evidence ↗
A global 2006–2023 dataset found low-lying algae weakened the coral-cover relationship below about 45% coral cover, while macroalgal effects persisted to about 65%.
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