A biological condition gradient for Caribbean coral reefs: Part II. Numeric rules using sessile benthic organisms

Area of Science:

• Marine biology
• Ecosystem assessment
• Conservation science

Background:

• Coral reefs face global collapse, threatening ecosystem services.
• Effective management requires tools to assess reef condition under anthropogenic stress.
• The Biological Condition Gradient (BCG) is a conceptual model for tracking ecological changes.

Purpose of the Study:

• To develop a quantitative BCG model for coral reefs in Puerto Rico and the US Virgin Islands.
• To provide a transparent framework for ecologically meaningful management decisions.
• To assess and communicate the condition of these fragile reef resources.

Main Methods:

• Developed a numeric BCG model using expert-defined decision rules for benthic assemblages.
• Utilized metrics such as live coral cover, species richness, and substrate type.
• Applied the model to shallow-water tropical fore reefs (<30 m depth).

Main Results:

• The numeric BCG model accurately predicted expert panel ratings for calibration (84%) and validation (89%) sites.
• The model demonstrated robustness in assessing coral reef condition.
• Key metrics included % live coral cover, coral species richness, and substrate composition.

Conclusions:

• The quantitative BCG model is a suitable tool for adaptive coral reef management.
• It supports bioassessment, criteria development, and the establishment of ecosystem condition benchmarks.
• This tool aids resource managers in evaluating, communicating, and restoring coral reef health.