- Monitor the status and trajectories of coral reefs across a majority of habitats and threats, including land-based sources of pollution & thermal stress
- Link changes in coral reef health with specific stressors, indicating specific management interventions most effective for preserving reefs
- Integrate assessments of understudied mesophotic coral reef ecosystems and threatened species in the USVI
- Provide data, outputs, and advice to stakeholders and create a nexus of information for reef research
At each site, benthic cover and coral health surveys are conducted yearly along six 10 m long permanent transects marked with steel or brass rods. Video sampling consists of one diver traversing each transect videotaping the benthic cover using a high definition digital video recorder. After taping, images from each transect are captured and imported into Coral Point Count with Excel Extension software (Kohler and Gil 2006). Each image is then analyzed by superimposing ten randomly located dots and identifying the substrate type located under each of the dots. For each transect, the percent cover of coral, epilithic algae, macroalgae, sponges, gorgonians, and sand/sediment are calculated by dividing the number of random dots falling on that substrate type by the total number of dots for that transect.
All coral colonies located directly under the transect lines are assessed in situ for signs of mortality and disease following a modified Atlantic and Gulf Rapid Reef Assessment protocol (Kramer et al. 2005). Partial mortality of coral colonies is broken into two categories: recent partial mortality and old partial mortality. Diseases are conservatively categorized into recognized Caribbean scleractinian diseases and syndromes that include bleaching, black band disease, dark spots disease, white plague, and yellow band (blotch) disease (following Bruckner 2007). Bleaching is assessed as abnormal paling of the colony, and, when present, the severity of the bleaching (paling or total whitening) and the area of the colony affected are assessed. A major bleaching event occurred between September and December 2005, affecting all monitored sites, and a mild bleaching event occurred September and October 2010. For each transect, the prevalence of coral impairment categories is calculated as the number of colonies with partial mortality, disease, or bleaching divided by the number of colonies assessed. For more details about coral health in the USVI click here.
Fish surveys have been historically conducted at 14 sites around St. Croix and
10 sites around St. Thomas and, starting in 2012, are conducted at 32 of the 33 monitoring sites. Ten replicate belt transects and three replicate
roving dive surveys are conducted at each site. Belt transects are 25m
x 2m and are conducted in 15 min per replicate. Roving replicates are either 30
min (sites < 25 m depth) or 15 min (sites >25 m depth). All fish encountered are recorded except blennies and gobies. Divers also assess the abundance of Diadema
antillarum sea urchins along the 25x2m belt
transects. The mean number of sea urchins per 100 m2 is calculated for each site. For more details about fish and Diadema
antillarum communities in the USVI click here.
Benthic temperatures are recorded at each site with a HoboTemp™ thermistor data logger (Onset Computer Corporation, Bourne, Massachusetts). Thermistors are affixed within transects and set to record at intervals of 15 minutes. Records are presented as daily averages across months.
currents are recorded at a subset of sites and times with Nortek Aquadopp™
Acoustic Doppler Current Profilers (ADCPs).
Profilers are set in bases on the seafloor and set to record current
speed and direction within predefined depth bins above the substrate.