Monitoring Coral Reefs to Understand Trends in Space and Time
By Erica K. Towle, Ph.D., National Coral Reef Monitoring Program coordinator
Have you ever wondered how coral scientists can track how coral reefs are doing? How can we compare
one coral reef area to another? How do we know if coral reef condition is changing over time? NOAA’s
Coral Reef Conservation Program monitors coral reefs at two different scales in order to help answer
If we want to know how coral reefs are doing broadly for a given region or compared to other
we can use data collected by the National Coral Reef Monitoring Program (NCRMP). This program covers
all U.S. states and territories that have coral reefs and uses the same methods in each region
collect data on corals and algae, fish, climate, and social science indicators. NCRMP uses a
sampling design that is called “stratified random sampling.” It means that we survey randomly
throughout given areas, for example, sites between 0-30m depth that have a hard bottom. Random
selection means we are not selecting for specific conditions like sites with the best coral
Random site selection allows us to see a representative range of all the sites in a given
that are in good condition, sites that are doing alright, and sites that are not doing as well.
random, representative sample allows us to say something about the jurisdiction or sub-region on
Let’s use Florida’s Coral Reef as an example. Using NCRMP data, we can say something about how the
reefs of Florida are doing on the whole, and we can even break that down to sub-regions, like how
the reefs in Southeast Florida are doing compared to the reefs of the Florida Keys.
But what if someone wanted to know about a particular reef site? NCRMP would not be a good dataset
to use in that case because we do not study the same sites over time (remember, random sampling!).
So in this case, we would want to use a fixed site monitoring design. The Coral Reef Conservation
Program supports fixed site monitoring in the states and territories through our grants and
cooperative agreements. Usually these local monitoring programs consist of a set number of
that the monitoring team goes back to year after year! This type of monitoring is especially useful
for answering specific questions about how a popular snorkeling or diving site may be changing over
time, or whether a coral restoration project is successful at a given location.
The questions you want to answer are important in designing a monitoring program, and sometimes, you
may want to consider a mix of both random and fixed sites! In general, a random-site design that
allows you to see the bigger picture of what’s happening at a regional scale can help put a
fixed-site design in perspective to help you key in on what’s happening at a specific place.
If you want to learn more about how NCRMP data can tell us about the status of a reef site overall
and by sub-region, check out the NCRMP Status Reports. If you want to learn more about other
projects that the Coral Reef Conservation Program supports through our competitive grants, such as
the Jurisdictional Awards that support local, fixed-site monitoring, check out Coral Reef
Conservation Program Funded Projects.
The NOAA Coral Reef Conservation Program was established in 2000 by the Coral Reef Conservation Act. Headquartered in Silver Spring, Maryland, the program is part of NOAA's Office for Coastal Management.