Coral Disease

Since the first coral disease outbreak was recorded in the early 1970s, approximately 29 diseases have been observed in 106 species of coral and in 54 countries around the globe (Spalding et al. 2001). In the Wider Caribbean region alone, approximately 18 coral diseases have been described that affect 43 species of scleractinian coral, specifically species of important reef-building corals (Weil and Rogers 2011).

In the Caribbean,seven coral disease including black band disease (BBD), white plague diseases (WPD), white band diseases (WBD), white pox disease (WPX), dark spots disease (DSD), yellow band disease (YBD) and Caribbeanciliate infection (CCI) have had the most significant impact on coral reef community structure (Sutherland et al. 2004; Raymundo et al. 2008; Croquer and Weil 2009; Weil and Rogers 2011). These seven diseases are described in detail below.

The first coral disease was observed on coral reefs in Belize, Bermuda, and Florida in 1973 (Rosenberg and Loya 2004). This disease was called black band disease (BBD) and was characterized by a 1mm thick, dark bacterial band that seperated denuded skelton from living tissue and that progressed up and outward across the colony at a rate of 3mm to 1 cm per day (Weiland Rogers 2011; Raymundo et al. 2008; Rosenberg and Loya 2004). Since the disease was first identified in the early 1970s, black band disease has been observed in 22 coral species and has been recorded on coral reefs throughout the world(Rosenberg and Loya 2004). Although the prevalence of black band disease on coral reefs is low, this disease is considered to be a significant factor affecting coral health since it affects large, reef-building coral species and effected colonies rarely recover (Rosenberg and Loya 2004). Recent studies suggest that black band disease may because by at least three different taxa of cyanobacteria (Weil and Rogers 2011).

In 1975, a new rapid tissue loss disease called white plague type I (WPD-I) was observed on coral reefs in the Florida Keys, where it primarily affected Mycetophyllia ferox corals (Dustin 1977; Rosenberg and Loya 2004; Weiland Rogers 2011). In 1995, Richardson et al. (1998) observed a more virulent form of white plague disease primarily affecting colonies of Dichocoenia stokesi and 16 other species of coral. This new type of white plague was called white plague type II (WPD-II) and the bacteriumAurantimonas coralicida was identified as the causative agent for the disease (Denner et al. 2013; Weil and Rogers 2011).

White plague diseases (types I and II) are characterized by lesion(s) of denuded skeleton that lay adjacent to living tissue and that progress as a band across the coral colony at a rate of 1mm to 10 cm per day (Raymundo et al. 2008; Weil and Rogers 2011). White plague diseases have been observed affecting approximately 41 species of scleractinian coral throughout the Caribbean region (Weil and Rogers 2011). Since the disease causes rapid tissue loss and affects species of important reef-building corals, white plague disease can drastically change coral community structure.

For example, between 2005 and 2007, outbreaks of white plague disease typeII, caused coral cover to decline by over 60% throughout the US VirginIslands (Miller et al. 2009). In addition to affecting overall coral cover, outbreaks of white plague disease have devastated populations of Orbicellids, the most important reef-building coral species in the US VirginIslands and Puerto Rico (Miller et al. 2009; Weil and Rogers 2011.)

A couple of years after white plague disease (WPD-I) was observed on coral reefs in the Florida Keys, a new rapid tissue loss disease was identified affecting species of Acropora (Weil and Rogers 2011). This new disease was called white band disease type I (WBD-I) and was described as rapid tissue loss disease that progressed along the Acroporid colony as a band of denuded skeleton. In the late 1990s, another type of white band disease was reported to only affect colonies of Acropora cervicornis.

This new disease, called white band disease type II (WBD-II), was distinguished from white band disease type I (WBD-I) by having a band of bleached tissue that lay between living coral tissue and the denuded skeleton (Weiland Rogers 2011). White band diseases types I and II have caused significant declines in Acropora palmata and Acropora cervicornis populations throughout the Caribbean region. In some locations, populations of Acropora palmata and Acropora cervicornis have been completely wiped as a result of these outbreaks, causing shallow-water coral reef community structure and morphology to change dramatically throughout the Caribbean region (Rosenberg and Loya 2004; AcroporaBiological Review Team 2005; Weil and Rogers 2011).

In 1994 a new tissue loss disease called white pox disease (WPX) was observed on Acropora palmata populations in Puerto Rico (Bruckner 2009; Galloway et al. 2009) and in 1996, the disease was reported on Acroporapalmata populations in Florida (Patterson et al. 2002; Galloway et al. 2009). Since that time, white pox disease has been reported in the US VirginIslands, the Bahamas, Cuba, Jamaica, and Mexico. Many scientists now believe that outbreaks of white pox disease have caused remainingAcroporid populations in the Florida Keys to decline by 88% (Galloway etal. 2009).

Dark spots disease (DSD) was first observed in the 1990s affectingOrbicella annularis colonies on reefs in Columbia (Weil and Rogers 2011; Galloway et al. 2009). Since that time, the disease has been observed affecting16 important scleractinian coral species on coral reefs throughout the Caribbean region (Weil and Rogers 2011). Dark spots disease lesions are characterized as small, circular areas of dark tissue that grow over time. In some species, lesions can cause depressions in the coral skeleton (Weiland Rogers 2011).

Yellow band disease (YBD) was first reported on Orbicella corals in 1997on coral reefs in the Florida Keys however observations of an unknown syndrome in the 1980s have now been identified as yellow band disease(Weil and Rogers 2011). In 1999, the disease was recorded on coral reefs throughout the Caribbean region and Bermuda, primarily affecting colonies of Orbicella annularis, Agaricia agaricites, and Porites astreoides (Galloway et al. 2009; Weil and Rogers 2011). The prevalence of yellow band disease in the US Virgin Islands and Puerto Rico (18-91%) is substantially higher than it is in most other Caribbean countries. As a result yellow band disease has been a main contributor to the decline of Orbicellacorals throughout Puerto Rico and the US Virgin Islands (Galloway et al.2009; Weil and Rogers 2011).

In 2004 a new tissue loss disease resembling black band disease was observed affecting 10 species of coral on reefs in Venezuela. Unlike blackband disease, however, this new disease was caused by a dense population of the ciliate protozoan genus Halofoliculina and was called Caribbean ciliate infection. Since 2004, the disease has been observed on22 coral species and on reefs throughout the Caribbean region (Croquerand Weil 2009; Weil and Rogers 2011).