Methods Used for Reef Monitoring

All of our scientific methods are documented in several reports and publications that can be found here. Below you can find a brief description for each category of monitoring.

A. Benthic Coverage

Video belt transects are used for estimation of benthic cover. For three to five 50m transects a digital video camera is used to record 0.5m x 50m belts. The videos are analyzed by stopping the video at equal intervals to provide 60 still frames. The life form under each point is recorded to the highest taxonomic level possible. Averages, variances, and statistical power are calculated based on the 50m replicates. The benthic categories used for analysis are corals (to genus level), turf algae (smaller than 2cm), macroalgae (larger than 2 cm, genus level if abundant), coralline algae, branching coralline algae, invertebrates with >10% benthic coverage (grouped by genus), all other are invertebrates grouped together, and sand/bare substrate.

B. Coral Communities

The point quadrat method is used to collect data for coral community analysis. At haphazard intervals along our transects described above, a .5m x .5m quadrat is randomly tossed and every coral whose center point lay inside the quadrat was recorded to species level and measured. The largest diameter, and the diameter perpendicular to the maximum were recorded for each colony. Percent coverage, relative abundances, population densities, and geometric diameters were calculated from these measurements.

C. Macroinvertebrate and Fish Abundance

All macroinvertebrates encountered within two meters of each side of the transect line are identified and counted. Fish surveys are completed along each of the five 50m transect lines. Counts are made of all fish, to the family (or functional group) level, within 5 meter of each side of the transect line.

D. Coral Recruitment

For each site, all corals <5cm in five 0.5m x 10m belt transects are identified to the genus level and counted. These data complement the recruitment data collected from permanent quadrats by increasing the spatial scale from 6m2 to 25 m2.

F. Biological Diversity

At each site a checklist list of all fish, corals and other invertebrates and algae identified is created. Identifications are made by MMT marine biologists in the field to the highest taxonomic resolution possible. If necessary, samples are collected for identification using taxonomic references or outside taxonomic expertise. A reference collection has been started by the MMT to support future monitoring and systematic work in the CNMI.