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Coral communities in the Caribbean face a new and deadly threat in the form of the highly virulent multi-host stony coral tissue loss disease (SCTLD). In late January of 2019, a disease with signs and characteristics matching that of SCTLD was found affecting a reef off the coast of St. Thomas in the U.S. Virgin Islands (USVI). Identification of its emergence in the USVI provided the opportunity to document the initial evolution of its spatial distribution, coral species susceptibility characteristics, and its comparative impact on coral cover at affected and unaffected coral reef locations. Re-assessments at sentinel sites and long-term monitoring locations were used to track the spread of the disease, assess species affected, and quantify its impact. The disease was initially limited to the southwest of St. Thomas for several months, then spread around the island and to the neighboring island of St. John to the east. Differences in disease prevalence among species were similar to reports of SCTLD from other regions. Highly affected species included Colpophyllia natans, Eusmilia fastigiata, Montastraea cavernosa, Orbicella spp., and Pseudodiploria strigosa. Dendrogyra cylindrus and Meandrina meandrites were also highly affected but showed more variability in disease prevalence, likely due to initial low abundances and the rapid loss of colonies due to disease. Siderastrea spp. were less affected and showed lower prevalence. Species previously reported as unaffected or data deficient that were found to be affected by SCTLD included Agaricia spp., Madracis spp., and Mycetophyllia spp. We also observed multi-focal lesions at SCTLD-affected sites on colonies of Porites astreoides, despite that poritids have previously been considered low or not susceptible to SCTLD. Loss of coral cover due to acute tissue loss diseases, which were predominantly SCTLD, was significant at several monitoring locations and was more impactful than previous mass bleaching events at some sites. There are no signs that the USVI SCTLD outbreak is abating, therefore it is likely that this disease will become widespread across the U.S. Caribbean and British Virgin Islands in the near future.
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DETERMINING CORAL REEF WATER QUALITY USING FORAMINIFERA IN THE US VIRGIN ISLANDS
Coral reefs in the US Virgin Islands (USVI) are threatened by multiple human impacts such as coastal development and pollution. In St. John,USVI, watershed development and unpaved roads have been shown toincrease the delivery of sediment and land-based pollutants to sensitive coral reef habitats. Hallock et al. (2003) described a “FORAM Index” (FI),based on the proportion of symbiont-bearing foraminifera. The FI is used asa proxy for water quality in tropical coral reef environments and predicts whether water quality is adequate for reef growth or recovery. The objectives of this study are 1) to examine differences between the FI in coral reefs below areas of watershed development (with abundant unpaved roads) compared to below undeveloped watersheds that are protected within the Virgin Islands National Park, and 2) to examine if the FI changed from 2011 to 2013. Benthic sediment samples (top 1-2 cm) were collected using snorkel and SCUBA in 2010, 2011, and 2013 from three coral reef sites, one below a developed watershed, one below a minimally developed watershed and one from a mangrove area with coral reefs (Hurricane Hole).Samples were wet sieved (63μm), split, and 150-200 Foraminifera were picked and counted. Foraminifera were then identifi ed and classified as symbiont-bearing, opportunistic, or heterotrophic. Finally, the FI was calculated for each site. The FIs at minimally developed sites were greater than at developed sites, indicating better water quality at sites protected by the national park. The FI increased between the years, suggesting a slight improvement in water quality over time, which may be related to the paucity of large storms or the implementation in 2011 of watershed restoration. The FORAM Index can be used as part of regular reef monitoring to track the condition of coral reefs.
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- Award ID(s):
- 1700920
- PAR ID:
- 10487699
- Editor(s):
- no editor.
- Publisher / Repository:
- Ocean Sciences Meeting
- Date Published:
- Journal Name:
- Ocean Sciences Meeting
- Edition / Version:
- 1
- Volume:
- 1
- Issue:
- 1
- Page Range / eLocation ID:
- 1
- Subject(s) / Keyword(s):
- foraminifera reef Virgin Islands
- Format(s):
- Medium: X Size: 1 Other: 1
- Size(s):
- 1
- Location:
- Honolulu, HI
- Sponsoring Org:
- National Science Foundation
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Stony coral tissue loss disease (SCTLD) was first observed in St. Thomas, U.S. Virgin Islands (USVI) in January 2019. This disease affects at least 20 scleractinian coral species; however, it is not well understood how reef diversity affects its spread or its impacts on reef ecosystems. With a large number of susceptible species, SCTLD may not follow the diversity-disease hypothesis, which proposes that high species diversity is negatively correlated with disease prevalence. Instead, SCTLD may have a higher prevalence and a greater impact on reefs with higher coral diversity. To test this, in 2020 we resampled 54 sites around St. Thomas previously surveyed in 2017 or 2019 by the National Oceanic and Atmospheric Administration National Coral Reef Monitoring Program. These sites represented a variety of species diversity values [categorized into poor (<12 spp. rich.) and rich (12 spp. rich.)] in multiple disease zones (Endemic: disease present 9 months; Epidemic: disease present 2–6 months; Control and Emergent: disease present no disease/<2 months). We hypothesized that, contrary to the diversity-disease hypothesis, sites with high species diversity (as measured by species richness or Simpson’s index) would have higher disease prevalence within the epidemic zone, and that high species diversity sites would have a greater impact from disease within the endemic zone. Results indicated a significant positive relationship between disease prevalence and diversity in the epidemic zone, and a similar trend in the endemic zones. Additionally, a negative relationship was seen between pre-outbreak diversity and loss of diversity and coral cover within the endemic zone. This supports the hypothesis that higher diversity predicts greater disease impact and suggests that SCTLD does not follow the diversity-disease hypothesis. Within the epidemic zone, the species with the highest SCTLD prevalence were Dendrogyra cylindrus, Colpophyllia natans, and Meandrina meandrites, while in the endemic zone, Diploria labyrinthiformis, Pseudodiploria strigosa, Montastraea cavernosa, and Siderastrea siderea had the highest SCTLD prevalence. Understanding the relationship between species diversity and SCTLD will help managers predict the most vulnerable reefs, which should be prioritized within the USVI and greater Caribbean region.more » « less
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