Coral Reef Monitoring
Calculation Methods
Coral Reef Monitoring
Calculation Methods
Percent Bottom Cover: Results are calculated for each transect using simple
percentage calculations. This is made even simpler because our transects
are designed to cover a total of 100 data points; thus each data point corresponds
to one percentage point.
However because sometimes data is not recorded for all 100 transect data
points, routine percentage calculations should be carried out based on the
actual number of data points recorded for the transect.
First, count and tabulate the data points by bottom cover category. For
each tabulated category, divide the number of category data points by the
total number of data points for the transect and multiply the result by
100. Thus, for 11 hard coral data points on a transect with 97 data points,
the calculation is:
hard coral % = {(hard coral data points) x 100} / total transect data points
hard coral % = (11) x (100) / 97
hard coral % = 11.3%
To report percent bottom covers for monitoring sites, calculate and report
the average of all transects done for the site. Thus, if 3 transects were
run on site A with algae percent cover results of 24%, 17%, and 27%, the
reported result for site A for the time period in question is:
site A algae % cover = (24+17+27) / 3
site A algae % cover = 22.6%
Variances are calculated using standard methods.
Coral Stress Index: Using the same percentage calculation method, we report
the percent of hard coral colonies showing signs of sickness or stress.
For each transect, add together all recorded data points for the sick, bleached
dying, or damaged hard coral heads. Divide this total by the total number
of hard coral colonies recorded for the transect and multiply the result
by 100. Thus, if a transect shows 5 stressed coral colonies out of a total
31 hard coral data points, the coral stress index is:
coral stress index = (5 X 100) / 31
coral stress index = 16%
To report the coral stress index for a monitoring site, average together
the results for all transects done at the site, using the same method described
under percent bottom cover.
Species Richness: Species richness is simply reported as the total number
of hard coral species recorded for a transect. For a site overall, species
richness is the cumulative total of all species recorded for all transects
at the site.
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