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NCER Grantee Research Project Results

Differences in Susceptibility to Black Band Disease (BBD) of two Species of the Host Coral Diploria on Bermuda Reefs

EPA Grant Number: MA916976
Title: Differences in Susceptibility to Black Band Disease (BBD) of two Species of the Host Coral Diploria on Bermuda Reefs
Investigators: Kuehl, Kristin
Institution: Florida International University
EPA Project Officer: Jones, Brandon
Project Period: September 1, 2008 through August 31, 2010
RFA: GRO Fellowships for Graduate Environmental Study (2008)
Research Category: Academic Fellowships

Description:

Objective:

Black band disease (BBD) is a polymicrobial disease associated with the global decline of coral reef ecosystems. On the reefs of Bermuda, Diploria labyrinthiformis demonstrates what appears to be resistance to BBD whereas D. strigosa is often observed to be infected. This project aims to investigate the underlying reasons behind the observed difference in BBD prevalence and susceptibility by addressing the following hypotheses: 1) the microbial communities normally present in the surface mucopolysaccharide layer (SML) of D. labyrinthiformis differ from those associated with D. strigosa and confer resistance to BBD; 2) the microbial community present in BBD in Bermuda differs from those in other regions of the Caribbean where D. labyrinthiformis is commonly infected; 3) the BBD consortium that infects D. strigosa is not able to cause infection in D. labyrinthiformis; 4) BBD infection, with BBD from D. strigosa, will occur in D. labyrinthiformis under conditions of increased temperature; and 5) D. labyrinthiformis is more efficient at sloughing SML, and therefore pathogens that settle into the protective mucus layer, than D. strigosa.

Approach:

Microbial communities in the SML and BBD will be characterized by amplicon length heterogeneity polymerase chain reaction (LH-PCR), a method that distinguishes microbial community patterns based on the lengths of the hyper-variable regions of the 16S rRNA gene. Molecular profiles generated from the Bermuda BBD samples will be compared to published LH-PCR profiles of BBD collected in other regions of the Caribbean. Infection experiments will be conducted at 26 ºC and 30 ºC (below and above the disease temperature threshold) by placing aliquots of BBD collected from infected D. strigosa and D. labyrinthiformis (if found) on top of healthy colonies of each species to determine if BBD collected from one species will infect the other and whether temperature has a role in infection of D. labyrinthiformis. The ability of each species to shed SML will be compared by measuring the rate at which individual colonies clear their surfaces of marine sediment deposited experimentally on the coral surface.

Expected Results:

Anticipated differences between the microbial communities present in the SML of healthy colonies of both species will provide evidence to support the role of microbes in conferring resistance to infectious disease. Microbial communities in BBD are expected to have a distinct molecular profile that differs from previously documented BBD community profiles in other regions of the Caribbean. Laboratory induced BBD infections are expected to occur regardless of the BBD origin when conducted at the increased temperature treatment. Preliminary results suggest that D. labyrinthiformis is more efficient at shedding SML, which may be the basis of BBD resistance.

Supplemental Keywords:

Black band disease (BBD), coral disease, Diploria strigosa, Diploria labyrinthiformis,16S rRNA, microbial communities, surface mucopolysaccharide layer (SML), mucus, amplicon length heterogeneity (ALH-PCR), molecular profiling, Bermuda,

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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