Guam Long-term Coral Reef Monitoring Program Coral Colony Size and Condition Surveys since 2010

The Government of Guam's Comprehensive Long-term Monitoring at Permanent Sites in Guam project, also known as the Guam Long-term Coral Reef Monitoring Program (GLTMP), is a NOAA-funded project currently coordinated through the University of Guam Marine Laboratory. The program involves the regular, intensive collection of data for a suite of coral reef ecosystem health parameters at high priority reef areas (HPRAs) around Guam, as well as critical support for coral bleaching response and other activities carried out by the multi-partner Guam Coral Reef Response Team. The program currently utilizes a split-panel sampling approach, whereby a mix of permanent and non-permanent sampling stations (one sampling station = one transect) are visited within each HPRA. The HPRAs were selected by an advisory body comprised of reef managers, researchers, and technicians; these reef areas were not intended to be representative of Guam's reefs more broadly. The locations of the sampling stations within each HPRA are generated randomly using GIS software. Various coral reef surveys are carried out on an annual basis along the seaward slope between 7 and 15 m depth in the Tumon Bay Marine Preserve and in East Agana Bay, while surveys are carried out biennially within the Piti Bomb Holes Marine Preserve, the Achang Reef Flat Marine Preserve, and the eastern side of the Cocos Barrier Reef (Cocos-East). Surveys were also carried at along reef margin (1-2 m) and slope (2-15 m) of Western Shoals, in Apra Harbor, in 2011. The surveys, which are currently conducted by University of Guam Marine Laboratory biologists, and which were supported by NOAA PIRO through 2019, currently include benthic photo transects, stationary point count fish surveys, macroinvertebrate belt transects, and chain-length rugosity surveys. The GLTMP has conducted surveys at the Tumon and East Agana HPRAs since 2010, the Piti HPRA since 2012, and the Achang and Cocos-East HPRAs began in 2014. Surveys for Fouha Bay HPRA began in 2015 with data collections also occurring in 2019 and 2021, but the site has not been re-visited due to shifting management priorities. Baseline data is available for the Western Shoals HPRA from 2011 but this site has not been re-visited.

Corals are the main contributor to coral reef accretion, provide critical habitat for numerous reef organisms, and serve as a food source for some reef organisms. In recognition of the critical important of corals, coral colony size and condition surveys were carried out by the GLTMP at several HPRAs on a regular basis between 2010 and 2019. Nearly all of the coral quadrat surveys were carried out by a single observer. The size and condition are assessed for all coral colonies found within quadrats placed every 5 meters along 30-m transects (15-m transects for the Western Shoals HPRA, 25 m for other HPRAs prior to 2018). These monitoring data on coral communities provide results on coral colony density, size, condition, and diversity; allow for exploration of community structure by functional group and size; and can be used to detect changes in coral communities over time. The coral quadrat surveys were eliminated beginning in 2020 due to staff capacity limitations, but the nails marking the quadrat locations at some sampling stations have been been maintained opportunistically.

IMPORTANT NOTE: The plate-and-pillar coral, Porites rus, was excluded from the coral quadrat survey during the 2019 and 2020 field seasons due to the considerable time required to properly assess the size and condition of this abundant species and the limited availability of the program coordinator to carry out the specialized survey.