Detailed Research Information

Detailed project information for
Study Plan Number 01094

Branch : Fish Health Branch

Study Plan Number : 01094

Study Title : Diseases of Coral and Coral Reef Fishes

Starting Date : 10/01/2002

Completion Date : 09/30/2007

Principal Investigator(s) : Densmore, Christine

Primary PI : Densmore, Christine

Telephone Number : (304) 724-4437

Email Address : cdensmore@usgs.gov

SIS Number :

Primary Program Element : Fisheries and Aquatic Resources

Second Program Element :

Status : Active

Abstract : BACKGROUND
Coral reefs form taxonomically diverse marine ecosystems and determine the physical structure of many coastlines. Caribbean coral communities are thought to have been relatively stable for 125 thousand years until a collapse in the 1980s. As a result of this collapse, live coral cover dropped from values of 50% or more to 1-2% and long-lived species with mass-spawning reproductive habits such as Acropora and Montastrea are being replaced by shorter-lived species with internal fertilization such as Porites and Agaricia. Often, 19th century overfishing of large reef herbivores is described as setting the stage for coral decline. The grazing sea urchin Diadema antillarum replaced the large herbivores as a controller of macroalgae. The demise of corals followed an overgrowth of macroalgae when an unidentified pathogen devastated urchin populations in 1983-84. Nutrient enrichment due to runoff has also been implicated as a contributing factor in algae overgrowth (Jackson 2001).

Outbreaks of coral diseases are not well understood. While much effort has been applied in attempts to associate disease with singular causative pathogens and to fulfill Koch’s postulates, it appears that several diseases are polymicrobic in nature. Breakdowns of innate defense mechanisms are suspected of playing a role in coral disease, and climate variability, human activity, pollutants, African dust, and habitat degradation have all been identified as predisposing factors. Also, coral predators may play a role in disease increase by initiating tissue damage and allowing infection, or by being vectors for coral pathogens. Pathogenic, parasitic, saprophytic, and fouling microbes are widely distributed in aquatic environments. The density of these microbes often selects for potent chemical defenses in marine macro organisms. Breakdowns in these defense mechanisms due to environmental stressors may result in rapid microbial colonization and death of the organism. Large shifts in commensal microbial consortiums occur in response to plant and animal host stress. These shifts can be monitored by molecular methods and used to assess coral and plant health.

While the use of live coral and related organisms for laboratory-based in vivo studies is certainly beneficial, the development and use of cell culture models offers many advantages. For instance, environmental parameters (temperature, water quality, photoperiod, etc) could be controlled quite specifically in order to evaluate the effects of these abiotic variables at the cellular level. Biotic factors such as the presence of other organisms, including symbiotic algae/ dinoflagellates, could also be manipulated to gauge their relationships to diseases and syndromes affecting corals. In addition, the time needed to ascertain a response to exposure to pathogenic and nonpathogenic organisms, environmental change or other forms of challenge or manipulations may be considerably reduced in cell culture and more biologically conservative than in vivo studies (Kopecky and Ostrander 1999).

The genetics and systematics of many reef organisms is largely unknown and species designations among reef organisms are often nebulous. Corals often spawn en masse offering opportunities for hybridization. Many branching corals reproduce by vegetative processes as well. Thus, hybrid individuals may be the founders of large tracts of coral reef. Hybrid individuals (and colonies) may be either more or less susceptible to particular stresses and pathogens. Thus, patchy die-offs may result. While it may seem intuitive that the genetic differences between reef organisms would simply be a function of distance, other less-obvious factors may well operate as barriers to gene flow.

This study is a broad-based effort to examine the interrelationships of coral reef organisms, disease agents and processes, and the environment. Although this study plan constitutes an overarching document for a number of diverse investigations, focused studies into any of the described problem areas may evolve as interest and funding grows. The proposed research will integrate scientific investigations of factors affecting coral reef health and aid management in developing sound policies for protection of the resource.
OBJECTIVES
This study will address several of the issues and research priorities listed above including studies of the ecological relationships of coral reef species, relationships of environmental factors and contaminants with coral disease, genetics and systematics of coral reef organisms, and microbial pathogens of reef organisms. We will

1. develop culture and propagation techniques for important reef species including coral, anemones, bivalves, echinoderms, sponges, mollusks, algae, and plants in order to provide a ready source experimental material. Special emphasis will be given to Manicina sp. (rose corals), Porites sp. (finger coral), Cladocora sp. (tube corals), Gorgonians (sea rods), Thalassia sp. (turtle grasses), Chione sp. (bivalve useful for following environmental conditions when retrieved from sediment strata), potentially invasive algae (i.e. Caulerpa sp.). Additionally, several coral predators may be cultured including sponges, tunicates, snails, and fireworms to study their role in initiating coral stress and portal of microbial pathogen entry.

2. develop molecular biomarkers indicative of coral health status. Many gene products are regulated by physiological and environmental factors (for example, heat shock proteins are elevated in response to temperature change, and metallothionins are up-regulated in response to heavy metal exposure). These molecules can be identified and measured by molecular techniques to provide a profile of health status for use in predictive modeling.

3. identify microbes associated with coral and other reef organisms and determine their population dynamics, host range and (in the case of pathogens) virulence mechanisms.

4. develop genetic markers to study the dispersion and gene flow of ubiquitous reef organisms and gain understanding of the degree of interrelatedness of reefs and their populations.

5. identify patterns of cryptic or pseudocryptic speciation in widely dispersed reef organisms and determine how these patterns are influenced by and distributed throughout the environment. As one example, pseudocryptic coccolithophorid and foraminiferal species have recently been identified that occupy particular niches in the environment. These pseudocryptic species, once recognized, can then be identified in cores making it possible to use these proxies to study past environmental conditions.

6. investigate methods for non-invasive, non-destructive sampling of coral tissues and identify surrogate indicators of reef health.

7. develop in vitro (cell culture) methodologies for use in the investigation of physiological and viral disease in corals.
HYPOTHESIS TO BE TESTED
1. Large volume culture systems using natural lighting (greenhouse conditions) can be designed to operate efficiently and to imitate faithfully near shore coral environmental conditions.

2. Pathogenic, parasitic, saprophytic, and fouling microbes are widely distributed in aquatic environments. The density of these microbes may select for potent chemical defenses in marine macroorganisms. Breakdowns in these defense mechanisms due to environmental stressors may result in rapid microbial colonization and death of the organism. Large shifts in commensal microbial consortiums occur in response to plant and animal host stress. These shifts can be monitored by molecular methods and used to assess coral and plant health.

3. Widely dispersed organisms such as corals, marine plants and algae, bivalves, and protists such as foraminifera may elaborate cryptic or pseudocryptic speciation patterns as a result of stabilizing selection and/or ecological selection. Molecular methods may be used to identify these speciation patterns and to associate particular unrecognized species with particular environmental conditions.

4. Molecular biomarkers can be found in corals or surrogate reef species that accurately reflect reef health.

5. In vitro (cell culture) methodologies can be developed to be utilized as laboratory models to aid our investigations of the effects of environmental variables and pathogenic and nonpathogenic organisms on coral reef systems.

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Last Modified: October 21, 2002 dwn
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Branch :	Fish Health Branch
Study Plan Number :	01094
Study Title :	Diseases of Coral and Coral Reef Fishes
Starting Date :	10/01/2002
Completion Date :	09/30/2007
Principal Investigator(s) :	Densmore, Christine
Primary PI :	Densmore, Christine
Telephone Number :	(304) 724-4437
Email Address :	cdensmore@usgs.gov
SIS Number :
Primary Program Element :	Fisheries and Aquatic Resources
Second Program Element :
Status :	Active
Abstract :	BACKGROUND Coral reefs form taxonomically diverse marine ecosystems and determine the physical structure of many coastlines. Caribbean coral communities are thought to have been relatively stable for 125 thousand years until a collapse in the 1980s. As a result of this collapse, live coral cover dropped from values of 50% or more to 1-2% and long-lived species with mass-spawning reproductive habits such as Acropora and Montastrea are being replaced by shorter-lived species with internal fertilization such as Porites and Agaricia. Often, 19th century overfishing of large reef herbivores is described as setting the stage for coral decline. The grazing sea urchin Diadema antillarum replaced the large herbivores as a controller of macroalgae. The demise of corals followed an overgrowth of macroalgae when an unidentified pathogen devastated urchin populations in 1983-84. Nutrient enrichment due to runoff has also been implicated as a contributing factor in algae overgrowth (Jackson 2001). Outbreaks of coral diseases are not well understood. While much effort has been applied in attempts to associate disease with singular causative pathogens and to fulfill Koch’s postulates, it appears that several diseases are polymicrobic in nature. Breakdowns of innate defense mechanisms are suspected of playing a role in coral disease, and climate variability, human activity, pollutants, African dust, and habitat degradation have all been identified as predisposing factors. Also, coral predators may play a role in disease increase by initiating tissue damage and allowing infection, or by being vectors for coral pathogens. Pathogenic, parasitic, saprophytic, and fouling microbes are widely distributed in aquatic environments. The density of these microbes often selects for potent chemical defenses in marine macro organisms. Breakdowns in these defense mechanisms due to environmental stressors may result in rapid microbial colonization and death of the organism. Large shifts in commensal microbial consortiums occur in response to plant and animal host stress. These shifts can be monitored by molecular methods and used to assess coral and plant health. While the use of live coral and related organisms for laboratory-based in vivo studies is certainly beneficial, the development and use of cell culture models offers many advantages. For instance, environmental parameters (temperature, water quality, photoperiod, etc) could be controlled quite specifically in order to evaluate the effects of these abiotic variables at the cellular level. Biotic factors such as the presence of other organisms, including symbiotic algae/ dinoflagellates, could also be manipulated to gauge their relationships to diseases and syndromes affecting corals. In addition, the time needed to ascertain a response to exposure to pathogenic and nonpathogenic organisms, environmental change or other forms of challenge or manipulations may be considerably reduced in cell culture and more biologically conservative than in vivo studies (Kopecky and Ostrander 1999). The genetics and systematics of many reef organisms is largely unknown and species designations among reef organisms are often nebulous. Corals often spawn en masse offering opportunities for hybridization. Many branching corals reproduce by vegetative processes as well. Thus, hybrid individuals may be the founders of large tracts of coral reef. Hybrid individuals (and colonies) may be either more or less susceptible to particular stresses and pathogens. Thus, patchy die-offs may result. While it may seem intuitive that the genetic differences between reef organisms would simply be a function of distance, other less-obvious factors may well operate as barriers to gene flow. This study is a broad-based effort to examine the interrelationships of coral reef organisms, disease agents and processes, and the environment. Although this study plan constitutes an overarching document for a number of diverse investigations, focused studies into any of the described problem areas may evolve as interest and funding grows. The proposed research will integrate scientific investigations of factors affecting coral reef health and aid management in developing sound policies for protection of the resource. OBJECTIVES This study will address several of the issues and research priorities listed above including studies of the ecological relationships of coral reef species, relationships of environmental factors and contaminants with coral disease, genetics and systematics of coral reef organisms, and microbial pathogens of reef organisms. We will 1. develop culture and propagation techniques for important reef species including coral, anemones, bivalves, echinoderms, sponges, mollusks, algae, and plants in order to provide a ready source experimental material. Special emphasis will be given to Manicina sp. (rose corals), Porites sp. (finger coral), Cladocora sp. (tube corals), Gorgonians (sea rods), Thalassia sp. (turtle grasses), Chione sp. (bivalve useful for following environmental conditions when retrieved from sediment strata), potentially invasive algae (i.e. Caulerpa sp.). Additionally, several coral predators may be cultured including sponges, tunicates, snails, and fireworms to study their role in initiating coral stress and portal of microbial pathogen entry. 2. develop molecular biomarkers indicative of coral health status. Many gene products are regulated by physiological and environmental factors (for example, heat shock proteins are elevated in response to temperature change, and metallothionins are up-regulated in response to heavy metal exposure). These molecules can be identified and measured by molecular techniques to provide a profile of health status for use in predictive modeling. 3. identify microbes associated with coral and other reef organisms and determine their population dynamics, host range and (in the case of pathogens) virulence mechanisms. 4. develop genetic markers to study the dispersion and gene flow of ubiquitous reef organisms and gain understanding of the degree of interrelatedness of reefs and their populations. 5. identify patterns of cryptic or pseudocryptic speciation in widely dispersed reef organisms and determine how these patterns are influenced by and distributed throughout the environment. As one example, pseudocryptic coccolithophorid and foraminiferal species have recently been identified that occupy particular niches in the environment. These pseudocryptic species, once recognized, can then be identified in cores making it possible to use these proxies to study past environmental conditions. 6. investigate methods for non-invasive, non-destructive sampling of coral tissues and identify surrogate indicators of reef health. 7. develop in vitro (cell culture) methodologies for use in the investigation of physiological and viral disease in corals. HYPOTHESIS TO BE TESTED 1. Large volume culture systems using natural lighting (greenhouse conditions) can be designed to operate efficiently and to imitate faithfully near shore coral environmental conditions. 2. Pathogenic, parasitic, saprophytic, and fouling microbes are widely distributed in aquatic environments. The density of these microbes may select for potent chemical defenses in marine macroorganisms. Breakdowns in these defense mechanisms due to environmental stressors may result in rapid microbial colonization and death of the organism. Large shifts in commensal microbial consortiums occur in response to plant and animal host stress. These shifts can be monitored by molecular methods and used to assess coral and plant health. 3. Widely dispersed organisms such as corals, marine plants and algae, bivalves, and protists such as foraminifera may elaborate cryptic or pseudocryptic speciation patterns as a result of stabilizing selection and/or ecological selection. Molecular methods may be used to identify these speciation patterns and to associate particular unrecognized species with particular environmental conditions. 4. Molecular biomarkers can be found in corals or surrogate reef species that accurately reflect reef health. 5. In vitro (cell culture) methodologies can be developed to be utilized as laboratory models to aid our investigations of the effects of environmental variables and pathogenic and nonpathogenic organisms on coral reef systems.
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U.S. Department of the Interior \|\| U.S. Geological Survey 11700 Leetown Road, Kearneysville, WV 25430, USA URL: http://www.lsc.usgs.gov Maintainer: lsc_webmaster@usgs.gov Last Modified: October 21, 2002 dwn Privacy Policy and Disclaimers \|\| FOIA \|\| Accessibility