Guam Long-term Coral Reef Monitoring Program Macroinvertebrate Belt Transects 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, the eastern side of the Cocos Barrier Reef (Cocos-East), and Fouha Bay. 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 and the Piti HPRA since 2012. Data collection for the Achang and Cocos-East HPRAs began in 2014 and at the Fouha Bay HPRA in 2015. Baseline data is available for the Western Shoals HPRA from 2011 but this site has not been re-visited since its establishment due to shifting management priorities.

Macroinvertebrates are culturally, economically, and ecologically important resources for the people of Guam. In recognition of the value and importance of this resource, macroinvertebrate surveys are a key component of the Guam Long-term Coral Reef Monitoring Program. Macroinvertebrate surveys have been conducted at high priority reef areas around Guam since August 2010. The monitoring team counts the number of most commercially and ecologically important macroinvertebrate species within a 4 m x 30 m belt transect (4 x 25 m prior to 2017) at all sampling stations (except at the Western Shoals stations, where 4 m x 15 m belts were used). The longest dimension of Tridacna individuals is also recorded. These monitoring data on macroinvertebrate communities allow for the exploration of community structure by functional group and can be used to detect changes in macroinvertebrate communities over time.

IMPORTANT: Macroinvertebrate taxa consistently targeted by this survey since 2010 include Acanthaster planci (= A. cf. solaris), Actinopgya spp., Bohadschia spp., Charonia tritonis, Culcita novaeguineae, Diadema spp., Echinothrix spp., Holothuria spp., Lambis spp., Leiaster leachi, Linckia guildingi, L. laevigata, Octopus cyanea, Pearsonothuria graeffei, Stichopus spp., Tectus (= Rochia) spp., Thelenota ananas, Tridacna spp., and Tripneustes gratilla. Boring urchins (e.g., Echinometra spp. and Echinostrephus aciculatus) and small sea stars (Echinaster luzonicus, Fromia spp., Gomophia egyptiaca, Linckia multiflora) were dropped from the survey beginning in 2020, as it was clear that the survey method employed by the GLTMP was not appropriate for the consistent detection of these taxa. Anemones, crustaceans, and smaller molluscs (e.g., Cypraea spp., Turbo spp.) were not a focus of the survey and were recorded inconsistently between 2010 and 2019; these taxa were also officially omitted from the survey beginning in 2020. Observations of boring urchins, small sea stars, and these other small or cryptic taxa are included in the dataset archived with NCEI, but it is highly recommended that only larger, conspicuous macroinvertebrates be used to calculate total invertebrate density and invertebrate group density at the transect level, and that densities of the other taxa be utilized cautiously. It should also be noted that nocturnally active macroinvertebrates, such as Diadema spp., Echinothrix spp., Leister leachi, and some holothuroid taxa, were likely undercounted.

IMPORTANT: The 2010-2019 macroinvertebrate observations dataset initially archived with NCEI did not include zero count records, which could result in erroneous density values when averaging count or density values. Zero count records were added to the dataset using a cast and melt operation in R, and the updated dataset was archived with NCEI in December 2023.