An atoll not at all what I expected
The Center for Coastal Monitoring and Assessment (CCMA) within the National Centers for Coastal Ocean Science (NCCOS) at NOAA is among those responsible for creating maps of coral reefs. Maps are a critical part of nearly every aspect of coral reef protection. In 2009, NOAA’s Coral Reef Conservation Program (CRCP) asked us to map the coral reefs of Majuro, a Pacific Ocean atoll and the most populous island in the Marshall Islands chain. We have lots of experience with mapping reefs worldwide but none in an atoll with the geological makeup of a place like Majuro. With no elevation, a land area only a few hundred feet wide, and a deep central lagoon, the atoll looked quite different from the satellite images of other coral reefs we’ve mapped in the last ten years.
Our objective for this two week mission was to map as many of the unique reef types around the atoll as possible and match them up with the colors and textures shown in remote sensing images, a process called “ground truthing.” Being physically present in the study area is an essential part of accurately mapping natural resources. We needed to confirm what we believed were coral reefs based on analysis of a satellite imagery was actually a coral reef. CRCP will eventually use the maps we created to make decisions about how to conserve and manage those coral reefs. You can read more about this project on the NCCOS website, or download the report titled, Majuro Atoll, Republic of the Marshall Islands Coral Reef Ecosystems Mapping Report.
Using a GPS, a stack of satellite images, a note book, and video and still cameras, we made our way from site to site and recorded bottom type, reef zone, water depth, coral and algal cover, and any other notable aspects of the habitats at each site that could make our maps more accurate. We used small motor boats, kayaks, snorkeling, and simply hiking along the shoreline and wading to get to the necessary locations, some of which have seen very little human contact.
What we found
Despite the language barrier, we found the Marshallese eager to offer us access to the reefs in their backyards. Pointing out their house in a satellite picture and gesturing at a draft of our maps was always enough to get us to the right location for site validation.
We visited 311 spots and used the data that we collected to validate information from satellite imagery. When completed, we drew 1,829 reef ecosystem features covering 366 km2. We documented the locations of over 700 patch reefs, nearly 200 aggregate reefs, 6 km2 of dramatic spur and groove reef formations, and many other reef habitats that ringed the island in concentric circles. These maps, videos, and images are all available in a variety of formats to help people understand the atoll. Printable atlas-style maps, map computer files for technical users (in GIS), and interactive internet-based maps with links to field videos and pictures, satellite imagery, and other information; all are available to help guide science, education, and management activities on Majuro reef ecosystems.
The State of Majuro Coral Reefs
This was a great opportunity to do a comparative study of reef health with those found elsewhere in the world. The vast areas of live impossibly iridescent blue and pink toned corals at Majuro, and the regular presence of these small sharks- a group devastated in many parts of the world- were heartening to witness first-hand. It was disappointing to see the degraded condition of the reef habitats near some developed areas. Adjacent to one densely populated survey site, the islanders’ homes were little more than corrugated metal and salvaged lumber boxes backed right up to the water’s edge. As we were surveying the lagoon floor near these communities and we found reefs with less coral that were overgrown with algae or fouled with garbage.
The approach that we used here can be used to map other atolls and seamounts throughout the Marshall Islands.
Potential future work could focus on systems near more heavily populated areas, with development pressures, or those with key conservation or monitoring programs such as Ailinglaplap, Ailuk, Arno, Bikini, Jaluit, Kwagelain, Mili, and Rongelap.
NCCOS Blogger Biography: Matt Kendall has authored papers on fish habitats, biodiversity, marine parks, and seafloor mapping and has conducted research in a diversity of ocean settings including Hawaii, Samoa, Puerto Rico, the Virgin Islands, Chesapeake Bay, and coastal Georgia. Dr. Kendall joined CCMA in 1998, where he is a currently a scientist with CCMA’s Biogeography Branch. Prior to joining NOAA, he worked as a researcher at Florida Marine Research Institute and the Smithsonian Environmental Research Center. Dr. Kendall earned a Ph.D. from the University of Maryland, an M.S. from North Carolina State University, and a B.S. from the University of South Carolina.