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Coral Ecosystems Research
NOAA's Undersea Research Program supports a range of research projects that address the importance of corals for ecosystem integrity, climate monitoring, and harvesting of marine resources, among many other issues. There is a diversity of coral species that live in many climates and at a range of depths throughout our Earth's oceans. NURP's six regional centers are funding, supporting and conducting research throughout the greater U.S. to better understand the role of corals in the ecosystem. A range of current topics include:

Coral Reef Monitoring
Spotted moray among reef system (photo credit: D. Kesling)NURP supports several reef monitoring programs throughout the country. For example, the National Undersea Research Center for the Southeastern U.S. and Gulf of Mexico supports a coral reef fish assessment program from which results have been used to establish MPA boundaries, baselines and over-fished stocks in Florida Keys National Marine Sanctuary. This program is part of the sanctuary's monitoring effort to evaluate habitat condition and changes in the Sanctuary Preservation Areas and Tortugas Ecological Reserve and is characterized by innovative sample design statistics, rapid and detailed habitat assessments, multidisciplinary participation (benthic and fish groups working together), and timely publication of results. The program covers multiple habitat types, nearshore to offshore, and results provided the baseline from which marine protected areas and other reef habitats will be assessed and monitored for many years.

Coral Disease
Staghorn Coral with white-banded disease (photo credit: A. Bruckner )The most damaging disease killing corals in Florida and throughout the Caribbean is white band disease (right), which affects the branching corals in the genus Acropora and devastated populations long before any research or monitoring programs were in place to document the epidemic. Since then, additional diseases have emerged and the center supported projects that produced major findings. Seminal work related to blackband disease was published over the last ten years, including a Nature paper that identified the first coral pathogen using Koch's postulates and that also documented 40 percent mortality in some populations of the elliptical star coral: the disease now affects nearly two dozen other species. NURP is supporting other researchers who are also emerging as leading figures in marine disease work, related to a fungal pathogen that kills seafans. Results include learning that the fungal growth rate is temperature dependent, with temperatures usually below its growth rate optimum; this means, however, that almost any temperature increase should result in conditions where the pathogen does better. The pathogen is thus a "poster child" for an argument made in a Science paper about climate links (warming) and diseases. Similarly, the correspondence between a killing disease outbreak in a gorgonian and widespread coral bleaching reinforces this point.

Coral Bleaching
Brain coral with bleaching (photo credit: ?)Coral bleaching is an issue that has local, regional, and global significance, but corals are not the only organisms to bleach on the reef. A long-term program to assess the relevance of bleaching in foraminifera was pioneered in the early 1990s through NURP research in Florida and has continued throughout the decade. Forams contain a symbiont (diatoms vs. zooxanthellae found in corals) and are sensitive indicators of environmental change, including light, nutrients, and temperature. These studies point to foraminifera as bioindicators for environmental assessment and monitoring programs, and possibly as indicators of global change. Specific to coral bleaching, a long-term program discovered substantial natural and seasonal variation in the density of zooxanthellae in corals, with bleaching resulting at one extreme when zooxanthellae densities decrease to levels that can be detected by the eye. A main point of this paper is that zooxanthellae density can decrease seasonally by at least half, is not detectable by the human eye as a color change, and does not necessarily progress to a full-blown bleaching "event." This means that there is a lot more natural system variability than was previously known. Another study documented that coral tissue itself was surprisingly unaffected during two severe bleaching events in consecutive years. And corals that bleached one year also bleached the second year: this is important because there is an ongoing debate that suggests coral bleaching may be adaptive, but results here suggest otherwise.

Coral Reef Sponge Ecology
Tube sponges & soft corals  (photo credit: B. Walden)Several examples are provided that highlight ecological studies supported by the center. It's probably not an understatement to say that researchers working with the Florida program are rewriting the book related to sponge ecology and coral feeding biology (not part of this summary). For example, the importance of parrotfish predation on sponges was discovered in a series of experiments that documented the selectivity of sponge-eating fishes. When combined with new data on chemical defense, these results have completely altered our view of sponge predation on Caribbean reefs. The results have interesting management implications because "indirect effects" or linkages between sponge-eating fish and the benthos, due to the loss of certain predators or herbivores, may alter the ecology of reef sponges to permit the growth of otherwise cryptic species, some of which may more effectively compete for space with corals. At least a dozen other publications resulted from work on sponges to understand the chemical defenses of reef invertebrates against predatory fishes and novel assay systems were used to identify and isolate the responsible metabolites - some of which are being tested for their pharmacological potential.

Barrel sponges (photo credit: W. Harrigan)Long-term studies are underway to study the giant barrel sponge Xestospongia muta, which has been called the "redwood of the reef" for its size and supposed long-life. Like corals, specimens of X. muta have recently been observed to bleach during summer months, resulting in intense predation on bleached sponges by fishes and presumed sponge mortality. Since 1997, monitoring of marked sponges at permanent transect sites are used to investigate whether bleaching is caused by high temperatures, changes in chemical defenses, or reproductive status, and to gather demographic data. Early results suggest that temperature is not a factor, and that most sponges recover from bleaching events. Surprising outcomes include high levels of pulsed recruitment of "baby" sponges, and rapid recovery and regrowth of some bleached sponges. Finally, growth rates of X. muta are difficult to determine, but may be faster than originally thought. This monitoring program, along with several long-term, manipulative experiments to test resource allocation among growth, wound-healing, reproduction, and chemical defenses, will require years of study before patterns become clear and are only possible due to sustained funding and long-term commitments that are not typical of most funding programs, but are none-the-less critically important to advance knowledge of coral reef function and structure.

Representative NURP Projects

  1. Edmunds, P. J.. Global Climate Change & Coral Recruitment: The Interactive Effects of Temperature And Ontogeny on the Biology of Porites Astreoides Larvae (Year 2 of 2).
  2. Lirman, D.. Coral size-frequency distributions as indicators of reef health: Monitoring and modeling approaches.
  3. Richardson, L. L., and J. Voss. Environmental factors and coral community composition associated with coral diseases in the Northern Florida Keys and Bahamas’ Exuma Chain, Part II (Year 2 of 2).
  4. Steneck, R. S.. Trophic Cascades and the Role of the Coralline Algae in Coral Recruitment . (Year 2 of 2).
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Updated: April 16, 2007