Effect of phase shift from corals to Zoantharia on reef fish assemblages

Area of Science:

• Marine Biology
• Ecology
• Ichthyology

Background:

• The ecological consequences of coral reef phase shifts on fish communities are not well understood.
• Previous research has primarily focused on coral-to-macroalgae shifts, leaving a knowledge gap on novel phase shifts.
• Understanding impacts on fish assemblages is crucial for reef conservation.

Purpose of the Study:

• To compare fish assemblages on coral reefs with normal conditions versus those dominated by Palythoa cf. variabilis.
• To investigate how this specific phase shift affects fish richness, abundance, and body size.
• To identify changes in fish trophic groups associated with the phase shift.

Main Methods:

• Eight reefs in Todos os Santos Bay, Brazil, were surveyed.
• Cover of corals and Palythoa cf. variabilis was estimated.
• Fish richness, abundance, and body size were quantified for each reef type.

Main Results:

• Fish richness was significantly lower on phase-shift reefs (38 species) compared to normal reefs (48 species), a 20% reduction.
• No significant difference in overall fish abundance was observed between normal and phase-shift reefs.
• Carnivorous fish were more abundant on normal reefs, while mobile invertivores dominated phase-shift reefs.

Conclusions:

• The shift from coral dominance to Palythoa cf. variabilis dominance significantly reduces fish species richness.
• Phase shifts alter the trophic structure of reef fish communities, favoring mobile invertivores.
• These findings highlight the cascading effects of habitat changes on reef fish biodiversity and function.