Sediment suppresses herbivory across a coral reef depth gradient

Area of Science:

• Marine biology
• Coral reef ecology
• Ecological processes

Background:

• Sediments are common on coral reefs, but their impact on ecological processes is not fully understood.
• Previous studies show sediment in algal turfs suppresses fish herbivory on reef flats.
• Herbivory is crucial for coral reef health and resilience.

Purpose of the Study:

• To investigate the role of sediment in suppressing herbivory across different coral reef zones (base, crest, and flat).
• To quantify the effect of sediment reduction on herbivore feeding behavior.

Main Methods:

• Observations of fish feeding behavior were conducted following reductions in benthic sediment.
• Herbivory rates were measured across a depth gradient (reef base, crest, and flat).
• The impact of sediment load on herbivore bites per area per hour was quantified.

Main Results:

• Sediment was found to suppress herbivory across all reef zones studied.
• A slight reduction in sediment on the reef crest led to a substantial increase in herbivore bites.
• Surgeonfishes (Acanthuridae) accounted for over 80% of observed herbivore bites.

Conclusions:

• Natural sediment loads play a significant role in regulating coral reef herbivory.
• Reductions in sediment increased herbivory, particularly by surgeonfishes.
• Changes in benthic sediment loads could negatively affect coral reef resilience.