Enter Reef Survey Inputs
Enter field measurements to estimate a weighted reef health score. The form uses stacked page sections, with a responsive multi-column input grid.
Formula Used
Score = min(100, (Observed ÷ Target) × 100)
Score = max(0, 100 − (Observed ÷ Limit) × 100)
Score = ((Rugosity − 1) ÷ 4) × 100
Reef Health Index = Σ(Indicator Score × Weight) ÷ Σ(Weights)
Default targets and limits used in this calculator
- Live coral cover target = 60%
- Macroalgae upper limit = 50%
- Herbivorous fish biomass target = 2500 kg/ha
- Commercial fish biomass target = 1500 kg/ha
- Bleaching upper limit = 60%
- Disease upper limit = 20%
- Water clarity target = 25 m
- Rugosity scale = 1 to 5
This is a practical weighted screening model for comparisons, planning, and internal ecological reviews. It should complement, not replace, formal reef assessment frameworks.
How to Use This Calculator
- Enter the reef site name, date, and observer information.
- Provide field measurements for coral cover, algae, biomass, bleaching, disease, clarity, and rugosity.
- Click the calculate button to generate the composite index.
- Review the result boxes for overall condition, grade, and pressure.
- Inspect the component score table to identify the strongest and weakest reef indicators.
- Use the Plotly chart for visual comparison across components.
- Download the result as CSV for spreadsheets or PDF for reporting.
- Compare repeated surveys from different sites to track reef changes over time.
Example Data Table
| Site | Coral % | Macroalgae % | Herbivore kg/ha | Commercial kg/ha | Bleaching % | Disease % | Clarity m | Rugosity | Index |
|---|---|---|---|---|---|---|---|---|---|
| Lagoon Crest | 42 | 18 | 1800 | 900 | 12 | 3 | 17 | 3.8 | 70.40 |
| Outer Slope | 55 | 10 | 2400 | 1300 | 5 | 2 | 24 | 4.4 | 90.00 |
| Nearshore Patch | 24 | 32 | 1100 | 500 | 28 | 7 | 9 | 2.6 | 42.40 |
| Restoration Zone | 48 | 14 | 2100 | 850 | 8 | 1 | 20 | 4.1 | 78.20 |
Frequently Asked Questions
1) What does the Reef Health Index show?
It combines several ecological measurements into one weighted score from 0 to 100. Higher scores suggest healthier reef condition and lower visible stress.
2) Is this calculator suitable for official regulation?
It is best used for screening, reporting, education, and internal comparisons. Formal regulation should rely on approved local protocols and validated monitoring programs.
3) Why is macroalgae scored in reverse?
High macroalgae cover often reflects reduced grazing pressure or ecological imbalance. Because it usually signals stress, larger percentages lower the component score.
4) Why include both herbivorous and commercial fish biomass?
Herbivores help control algae, while commercial fish biomass reflects broader food-web strength and fishing pressure. Together they provide a fuller reef condition picture.
5) What is structural complexity or rugosity?
Rugosity estimates how physically complex the reef surface is. More complex reefs often provide more shelter, habitat niches, and ecological resilience.
6) Can I compare sites from different dates?
Yes, but keep field methods, units, and thresholds consistent. Comparisons are most meaningful when the same survey design is repeated over time.
7) What does the pressure index mean?
The pressure index is simply 100 minus the reef health score. It gives a quick stress-style view, where higher values indicate poorer condition.
8) Can I change the built-in thresholds?
In this version, the thresholds are fixed for consistency. You can edit the target and limit values in the code to match your program standards.