Quantifying fish-derived nutrient hotspots across reefscapes.

Area of Science:

• Marine ecology
• Biogeochemistry
• Reef ecosystems

Background:

• Animal aggregations create nutrient hotspots, enhancing ecosystem processes.
• Conditions for nutrient hotspot formation in continuous reef habitats are poorly understood.

Purpose of the Study:

• Investigate how reef structural complexity at different scales affects fish-derived nutrient supply.
• Determine the relationship between nutrient supply and benthic enrichment.

Main Methods:

• Fish surveys and photogrammetry were used across six reefscapes in the Florida Keys.
• Quantified vertical relief and vector ruggedness (VRM) at 25 m² scales.
• Estimated nitrogen (N) and phosphorus (P) supply using bioenergetics models and measured macroalgal nutrient content.

Main Results:

• Fish-derived nutrient supply increased with vertical reef relief up to ~2.8 m, then saturated.
• Vector ruggedness (VRM) positively correlated with nutrient supply, especially in low-relief areas.
• Macroalgal nutrient content showed non-linear responses to nutrient supply, with saturation observed at specific rates.

Conclusions:

• Mesoscale habitat complexity interacts across scales to influence consumer-driven nutrient supply and benthic enrichment.
• High-relief areas act as nutrient hotspots, with supply several times greater than surrounding reefs.
• Identifying thresholds in reef relief and VRM can guide restoration efforts to maximize productivity.