 | 01 Aspergillosis
Kiho Kim and C. Drew Harvell; Abstract Drivers of disease cycles are poorly understood in marine ecosystems in spite of increasing outbreaks. We monitored a newly emerged fungal epizootic aspergillosis affecting sea fan corals Gorgonia ventalina L. in the Florida Keys to evaluate causes of its rise and fall over 6 years. Since August 1997, aspergillosis has nearly eradicated large sea fans at some sites. However, sea fan densities have remained relatively constant due to episodic recruitment replacing large fans with small. Recruitment itself was affected by infection and occurred only when prevalence of disease was low. This impact on recruitment occurred because the largest, potentially most fecund colonies had the highest prevalence of disease, and the pathogen significantly suppressed reproduction of infected fans. Moreover, high mortality among adults resulted in a demographic shift to smaller colonies. The most dramatic impact of aspergillosis was the Keys-wide loss of >50% of sea fan tissue from complete and partial mortality. Aspergillosis prevalence has declined steadily over the last 6 years, and we consider the following hypotheses for decline of the epizootic: change in environment, change in pathogen input, and increase in host resistance. We conclude that increasing host resistance is the most likely driver of the decline. However, a change in any of a number of factors, for example, recruitment of naïve hosts, rate of pathogen input, or environmental conditions water quality and temperature, is likely to promote reemergence of the epizootic
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CLICK TO VIEW IMAGES FROM THIS STUDY Longitudinal study of aspergillosis in sea fan corals Kiho Kim1,*, Alisa P. Alker2,5, Kara Shuster1,4, Craig Quirolo3, C. Drew Harvell2 1 Department of Biology, American University, 4400 Massachusetts Ave., NW, Washington, DC 20016, USA 2 Ecology & Evolutionary Biology, Cornell University, Ithaca, New York 14853, USA 3 Reef Relief, Historic Seaport, 201 Williams St., #5, Key West, Florida 33040, USA 4 Donald Bren School of Environmental Science & Management, University of California, Santa Barbara, Santa Barbara, California 93106-5131, USA 5 Present address: Department of Epidemiology, CB#7435, University of North Carolina, Chapel Hill, North Carolina 27599, USA ABSTRACT: Aspergillosis a fungal disease is affecting sea fan corals Gorgonia spp. throughout the Caribbean. To measure the impact of this disease, we established longitudinal, or in other words individual-based, monitoring studies on 3 reefs in the Florida Keys, USA, to obtain estimates of incidence, rates of disease progress, recovery, and mortality. At Western Dry Rocks near Key West, 40 Gorgonia ventalinacolonies 20 initially healthy and 20 initially diseased were photo- monitored between June 1996 and May 1998. Additional sea fans were visually monitored during 2 localized outbreaks at Conch May 1998 to September 1999 and Carysfort July 2000 to May 2001 reefs located in the Upper Keys. Data from Western Dry Rocks showed that over a 2 yr period, the incidence rate was 0.58 sea fans yr–1and that tissue purpling can lead to tissue loss and subsequently to mortality, albeit at low frequencies. Most sea fans, once infected, maintained a low level of damage over time. Only 3 fans recovered from the disease; however 2 were subsequently re-infected. Case fatality rate was 10% 2 of 20 initially infected died, which is equivalent to 5% yr–1. However, mortality can increase during localized outbreaks. At Conch, mortality was 46% yr–1 among infected sea fans compared to 8% yr–1 at Carysfort, a less impacted site, during the same period. During an outbreak at Carysfort, mortality was 95% yr–1 among diseased sea fans. These data clearly demonstrate the significant role aspergillosis plays in the population ecology of sea fan corals.
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