From New Findings on Contaminant Threats in African Dust to the Future of Coral Reefs to Coral Chemical Defenses
USGS scientists will present major research findings at the 11th International Coral Reef Symposium in Fort Lauderdale, Fla. from July 7-11, 2008.
For more information on the symposium, please visit http://www.nova.edu/ncri/11icrs/
African Dust Poses Threat to Coral Reefs and Human Health: Contaminants carried with African dust to the Caribbean and the Americas may be a threat to marine organisms and humans, according to preliminary results of a new study by researchers with the U.S. Geological Survey, Oregon State University, and the University of the West Indies. The scientists compared contaminant levels in sources of African dust and downwind regions. Of the more than 100 persistent organic pollutants screened for in the samples, including banned and common-use pesticides, six pesticides (chlorpyrifos, dacthal, endosulfans, hexachlorobenzene, chlordane, and trifluralin) were detected in samples from all sites. Concentrations were significantly higher in Mali. DDE (a breakdown product of DDT) was also identified in Mali, U.S. Virgin Islands, and Trinidad samples. To date, DDT and carcinogenic dioxins and furans have been detected only in samples from Mali. Many of the identified contaminants are thought to be toxic to corals and other marine organisms and can interfere with reproduction, fertilization, or immune function. For more information, contact Virginia Garrison at 727-803-8747, ext. 3061 or email@example.com.
The Emperor Has No Coral? Results of research on coral reefs in the Florida Keys reef challenge the highly popular notion that present declines in reefs in Florida and elsewhere are related to human activities. High-resolution sub-bottom profiling, reef drilling, and mapping of benthic habitats along the reef tract present a paradox in coral growth patterns: reefs that are dead or dying -- and therefore not building -- outnumber live and building reefs about 100 to 1. Yet growth rates of all common coral reef species should have kept pace with the well-documented rise in sea level over the past 6,000 years. Why did so few reefs keep pace or build up with the rise in the present sea level? Geological history may provide an answer: two 500-year periods of non-growth of coral reefs occurred in the region 4.5 thousand years ago and 3,000 years ago. These periods of non-growth indicate times of environmental crises that predated modern human presence in the Florida Keys. The present period of rapid coral demise has spanned only about 30 years. For more information, contact Eugene Shinn at 727-533-1158, firstname.lastname@example.org or Barbara Lidz at 727-803-8747, ext. 3031, email@example.com.
The Future of Coral Reefs in the U.S. Virgin Islands: Can the Two Most Important Coral Species Recover? The Caribbean bleaching and disease event that began in the summer of 2005 caused significant mortality of the two most important reef-building corals in the U.S. Virgin Islands -- Acropora palmata (elkhorn coral) and Montastraea annularis (star coral) complex (Macx). The ability of these corals to recover will largely determine the future seascape in the Virgin Islands. Research by U.S. Geological Survey, National Park Service, and Florida Institute of Technology scientists on the effects of bleaching and disease showed that M. annularis complex was more affected by bleaching and disease than Acropora palmata. After the record-high seawater temperatures in 2005, more than 98 percent of the Macx coral cover bleached, and about 90 percent of the mortality from disease also occurred on this species group, with healing of disease lesions not seen. From 2003 to 2007, researchers documented disease prevalence on A. palmata around St. John that ranged from 0 to 52 percent, with high levels of white pox and low levels of white band disease. White pox lesions often heal. In addition, A. palmata in the U.S. Virgin Islands bleached for the first time in 2005. Over the next 50 to 100 years, it appears that A. palmata has a greater potential to recover than Macx because of its higher growth rate, greater ability to colonize new areas, and lower vulnerability to bleaching and disease. The future of these major reef-building corals and of U.S. Virgin Island reefs will depend also on the connectivity between these reef zones and sources of coral larvae. For more information, contact Caroline Rogers at 340-693-8950, ext. 221, firstname.lastname@example.org. Also, check out the new fact sheet on coral diseases following the massive bleaching event in 2005; it can be found at http://pubs.usgs.gov/fs/2008/3058/
Research Suggests Coral Bleaching Increases Likelihood of Diseases: Unusually high-water temperatures can increase the occurrence of coral disease by either influencing the concentration or virulence of disease-causing agents, or by increasing host susceptibility through bleaching. The 2005 Caribbean coral-bleaching event provided the opportunity to test the compromised-host hypothesis on two species in the U.S. Virgin Islands. Researchers found that as water temperature increased, the prevalence of disease on both bleached and unbleached coral colonies increased, and bleached A. palmata colonies suffered greater disease-associated mortality than unbleached colonies. By November 2005, more than 98 percent of the Montastraea cover had bleached, and within 5 months, disease incidence had increased 51-fold. Although the scarcity of unbleached Montastraea colonies prohibited a comparison between bleached and unbleached colonies, disease incidence returned to pre-bleaching conditions once colonies partially recovered by July 2006. These studies support the compromised-host hypothesis by indicating that disease prevalence and severity increase when colonies bleach, at least for A. palmata and Montastraea species. For more information, contact Erinn Muller at 321-674-7323, email@example.com. Also, check out the new fact sheet on coral diseases following the massive bleaching event in 2005; it can be found at http://pubs.usgs.gov/fs/2008/3058/
The Good, the Bad, and the Smelly: How do Coral Larvae Know Where to Settle? How algal species maintain dominance in degraded reef habitats is a critical question for reef resource managers. Some common reef algae, but not all, use chemical defenses to inhibit grazing by Caribbean reef fishes and the sea urchin Diadema antillarum. These chemical defenses may also influence competitive interactions between algae and corals. In this study, researchers found that chemical extracts of certain algal species could be detected (i.e., "smelled") by coral larvae, causing them to avoid settling in the area. However, not all algae are bad; some coralline (calcified) algae may act as facilitators for coral settlement. The research also showed that individual species of corals had the highest settlement in response to different species of coralline algae, indicating that higher coralline algal diversity could potentially enhance coral recruit diversity. For more information, contact Raphael Ritson-Williams at 772-538-0495, firstname.lastname@example.org or Ilsa Kuffner at 727-492-3886, email@example.com.
Underwater Sleuthing with Deep ATRIS: A New Tool for Mapping Habitats and Animals: Although geo-positioned observations of coral reefs and nearby areas are essential to many resource-conservation, monitoring and research projects, acquiring such imagery for large areas can be expensive and time-consuming. To enhance its mapping capabilities and provide a more efficient alternative, the U.S. Geological Survey has developed the Deep Along-Track Reef-Imaging System (Deep ATRIS), a towed sensor package deployable from boats of moderate size. Deep ATRIS is a lightweight, computer-controlled, towed vehicle that is 1.3 m long with a 63-cm wing span, and an operating tow-depth limit of 27 m, extendable to 90 m. Transect lengths of 56 km can be surveyed in 6 hours. Deep ATRIS can carry a wide variety of instruments, including sensors for measuring salinity, temperature, and chlorophyll, as well as cameras. Images are displayed and archived in real time on a topside computer, along with the corresponding GPS coordinates and imaging distance. The first sea trial was conducted in a coral reef habitat within Biscayne National Park, Florida, in July 2007. Deep ATRIS can provide a wealth of important information for managers and researchers, including percent cover, species abundance and richness, and bed-form characteristics. This information is useful for characterizing essential habitat, assessing changes, monitoring the progress of restoration efforts and ground-truthing other kinds of imagery. The images obtained from Deep ATRIS also reveal the potential for unobtrusive animal observations; fish and sea turtles seem unperturbed by the presence of the vehicle. For more information, contact David Zawada at 727-803-8747, ext 3132, firstname.lastname@example.org.
Barium Provides Clues to Coral Reef Health on Moloka‘i, Hawaii: An increase in erosion - and therefore sediment run-off into rivers and oceans -- on the island of Moloka‘i, Hawaii, has been linked to intensification of farming, clearing of native vegetation and introduction of feral and domesticated grazing animals. Managers would like to know if and how this increased sediment is affecting coral health in the fringing reef of Moloka‘i's southern coast. It is difficult, however, to decisively demonstrate a clear link between land-use patterns and changes in coral condition. Geochemical proxy records from corals offer a technique for recording environmental changes. Since suspended sediment in river water contains minor levels of barium, USGS researchers examined the presence of this element in Moloka‘i's coral skeletons as an indicator of coral reef health. Scientists also investigated the effects of infrequent, large-scale events such as Kona Storms and modification of the coastline. Coral geochemical results show an alongshore barium presence indicative of local runoff and sediment transport from the trade winds as well as reduced barium levels due to the impediment of sediment accumulation west of the wharf. The researchers compared these results with historical information from adjacent watersheds to compare present-day conditions with those of the past several decades. For more information, contact Nancy Grumet Prouty at 831-427-4726, email@example.com or Michael Field at 831-427-4737, firstname.lastname@example.org.
The Origin of Aspergillus Sydowii, a Common Disease of Caribbean Corals: Coral reefs are increasingly suffering outbreaks of disease, causing dramatic declines in population abundance and diversity. One of the best-characterized coral diseases is aspergillosis, caused by the fungus Aspergillus sydowii. A. sydowii is a globally distributed fungus commonly found in soil, so its presence in marine systems raises questions about its origin. By using microsatellite markers, researchers analyzed the population structure of A. sydowii from diseased sea fans, diseased humans and environmental sources worldwide. The results indicate that A. sydowii forms a single global population, with low to moderate genetic differences between the disease found in sea fans and the same fungus from environmental sources. Past researchers have suggested that A. sydowii originates from African dust blown into the Caribbean, and have identified Aspergillus from dust samples, although often only to the genus level. To test this, researchers isolated fungi from dust samples collected in Mali and St. Croix. Although a diversity of fungi was documented from African dust, including seven species of Aspergillus, none of the samples contained A. sydowii. Taken in conjunction with recent molecular evidence suggesting lack of a single point source of the fungus, this research suggests that there are likely multiple sources and introductions of this pathogen into marine systems. For more information contact Krystal Rypien at 858-534-3196, email@example.com or Virginia Garrison at 727-803-8747, ext. 3061 or firstname.lastname@example.org.
Growth Anomalies in Corals of the Indo-Pacific: Researchers assessed the distribution and prevalence of growth anomalies in Acropora corals from French Frigate Shoals (Hawaii), Johnston Atoll, and Tutuila (American Samoa) to better understand the disease and to develop preliminary assessments of the disease's spread in coral colonies. The study found that Acropora coral in all three regions had growth anomalies, but the distribution and prevalence was highest in American Samoa. Growth anomalies appear to cluster on coral colonies and progress to colony death. For example, growth anomalies on two coral colonies increased from 90 to 300 percent over 11 months of monitoring. At the cellular level, it is unclear whether these growth anomalies are true cancers or not. For more information, contact Thierry Work at 808-792-9520, email@example.com.
Coral Disease in the Remote Central Pacific: Distribution and the Importance of Proper Characterization: Coral diseases are an ever-increasing threat to coral reefs. This is clearly a concern for conservation and management of these systems and their reef associated organisms. This baseline survey was aimed at detailing the relationship between coral disease occurrence, environmental variables and coral community structure. Researchers conducted their study in the summer of 2007 at Palmyra Atoll National Wildlife Refuge. They measured environmental variables and recorded growth anomalies on four coral genera (Astreopora, Montipora, Fungia and Acropora). In addition, researchers observed tissue loss on colonies of encrusting Montipora sp. This presentation will discuss how prevalence of coral disease relates to the environmental variables and coral community structure. In addition, this study and others have determined that gross and microscopic characterization of Astreopora growth anomalies is crucial in helping establish case definitions for coral disease. Knowledge of coral disease at this important wildlife refuge will aid its future monitoring and management, as well as advance the understanding of coral diseases globally. For more information, contact Gareth Williams at Hawaii Institute of Marine Biology, 808-386-4784, Gareth.Williams@vuw.ac.nz or Thierry Work at 808-792-9520, Thierry_work@usgs.gov.
Disease Characteristics of Montipora White Syndrome in Kaneohe Bay, Oahu, Hawaii: Coral disease is emerging as a problem in the Indo-Pacific yet little is known about the ecology of these diseases or factors that may be affecting disease levels. Montipora white syndrome (MWS) is a coral disease resulting in tissue loss that was identified in Kaneohe Bay, Oahu, Hawaii, in 2004 but that has been documented throughout the Hawaiian archipelago. Kaneohe Bay provided a model system to examine the ecology and pathogenesis of this disease in detail. MWS was found in all seasons of the year, as well as all regions of Kaneohe Bay but prevalence was highest in south Kaneohe Bay. Fifty-four out of 57 tagged coral colonies infected with this disease experienced progressive tissue loss ranging from 1 percent of the colony to complete mortality within one year. One-third of the colonies lost more than 90 percent of their tissues resulting in partial to complete colony collapse within one year. Researchers found that MWS stopped and re-started on individual colonies and that multiple potential causes were seen when lesions were examined under the microscope. In addition, orange morphs of Montipora capitata are more susceptible to the disease than red morphs. For more information, contact Greta Aeby at 808 386-4784, firstname.lastname@example.org or Thierry Work at 808-792-9520, Thierry_work@usgs.gov.