Disease

Spatiotemporal and species-specific patterns of diseases affecting crustose coralline algae in Curac ̧ao

Abstract Distribution and abundance of coral diseases have been well documented, but only a few studies con- sidered diseases affecting crustose coralline algae (CCA), particularly at the species level. We investigated the spa- tiotemporal dynamics of diseases affecting CCA along the south coast of Curac ̧ao, southern Caribbean. Two syn- dromes were detected: the Coralline White Band Syndrome (CWBS) previously described and the Coralline White Patch Disease (CWPD) reported here for the first time. Diseases were present at all six study sites, and our results did not reveal a relationship between disease occurrence and human influence. Both diseases were more prevalent on the shallower reef flat than on the deeper reef slope, and during the warm/rainy season than during the cold/dry season. The patterns observed were consistent with a positive link between temperature and disease occurrence. Reef flat communities were dominated by Neogoniolithon mamillare and Paragoniolithon solubile, whereas deeper habitats were dominated by Hydrolithon boergesenii. Dis- eases affected all the species encountered, and no prefer- able host was detected. There was a significant relationship between both disease occurrences and CCA cover. Moni- toring of affected patches revealed that 90 % of lesions in CWBS increased in size, whereas 88 % of CWPD lesions regenerated over time. CWBS linear progression rate did not vary between seasons or species and ranged from 0.15 to 0.36 cm month-1, which is in the same order of mag- nitude as rates previously documented. We conclude that diseases have the potential to cause major loss in CCA cover, particularly in shallow waters. As CCA play a key role in reef ecosystems, our study suggests that the emer- gence of diseases affecting these algae may pose a real threat to coral reef ecosystems. The levels of disease reported here will provide a much-needed local baseline allowing future comparisons. 

Date
2015
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Curacao

Are infectious diseases really killing corals? Alternative interpretations of the experimental and ecological

Abstract:

Emerging infectious diseases are a worldwide problem and are believed to play a major role in coral reef degradation. The study of coral diseases is difficult but the use of culture-independent molecular techniques has been, and will continue to be, useful in a system where a limited number of visible signs are commonly used to define a “coral disease”. We propose that coral “diseases”, with rare exception, are opportunistic infections secondary to exposure to physiological stress (e.g. elevated temperature) that result in reduced host resistance and unchecked growth of bacteria normally benign and non-pathogenic. These bacteria are from the environment, the host, or the coral mucus layer and become opportunistic pathogens. While difficult and time consuming, we do not advocate abandoning the study of disease-causing pathogens in corals. However, these studies should include comprehensive efforts to better understand the relationship between coral diseases and environmental changes, largely anthropogenic in nature, occurring on coral reefs around the world. These environmental insults are the cause of the physiological stress that subsequently leads to coral mortality and morbidity by many mechanisms including overwhelming infections by opportunistic pathogens.

Date
2007
Data type
Scientific article
Theme
Research and monitoring

Human Pathogen Shown to Cause Disease in the Threatened Elkhorn Coral Acropora palmata

Abstract:

Coral reefs are in severe decline. Infections by the human pathogen Serratia marcescens have contributed to precipitous losses in the common Caribbean elkhorn coral, Acropora palmata, culminating in its listing under the United States Endangered Species Act. During a 2003 outbreak of this coral disease, called acroporid serratiosis (APS), a unique strain of the pathogen, Serratia marcescens strain PDR60, was identified from diseased A. palmata, human wastewater, the non-host coral Siderastrea siderea and the corallivorous snail Coralliophila abbreviata. In order to examine humans as a source and other marine invertebrates as vectors and/or reservoirs of the APS pathogen, challenge experiments were conducted with A. palmata maintained in closed aquaria to determine infectivity of strain PDR60 from reef and wastewater sources. Strain PDR60 from wastewater and diseased A. palmata caused disease signs in elkhorn coral in as little as four and five days, respectively, demonstrating that wastewater is a definitive source of APS and identifying human strain PDR60 as a coral pathogen through fulfillment of Koch’s postulates. A. palmata inoculated with strain PDR60 from C. abbreviata showed limited virulence, with one of three inoculated fragments developing APS signs within 13 days. Strain PDR60 from non-host coral S. siderea showed a delayed pathogenic effect, with disease signs developing within an average of 20 days. These results suggest that C. abbreviata and non-host corals may function as reservoirs or vectors of the APS pathogen. Our results provide the first example of a marine ‘‘reverse zoonosis’’ involving the transmission of a human pathogen (S. marcescens) to a marine invertebrate (A. palmata). These findings underscore the interaction between public health practices and environmental health indices such as coral reef survival. 

Date
2011
Data type
Scientific article
Theme
Research and monitoring
Journal