2005 STATE OF CORAL REEF REPORT.pdf - Mote Marine Laboratory

ENVIRONMENTAL AND ANTHROPOGENIC STRESSORS
The State of Coral Reef Ecosystems of the U.S. Virgin Islands
Coral reefs in the USVI face similar pressures as reefs elsewhere in the Caribbean (Rogers and Beets, 2001).
Of the 13 major coral reef stressors identified by the U.S. Coral Reef Task Force, 10 have been identified
as being problematic to reef ecosystems in the territory. These stressors include climate change; diseases;
tropical storms; coastal development and runoff; coastal pollution; tourism and recreation; fishing; and ships,
boats, and groundings. The impacts of these stressors on USVI coral reefs are summarized in this chapter.
Other stressors such as alien species, security activities, and offshore oil activities are not relevant to the
USVI. Stressors are described fully in Chapter 3 of this report.
Climate Change and Coral Bleaching
Climate change refers to the trend of
increasing mean global air temperature
and sea surface temperatures
(SST) within the last century compared
with previous estimates. This
warming trend is generally attributed
to the atmospheric accumulation of
greenhouse gases. Bleaching in the
USVI has been reported since 1987
(Figure 4.2). Bleaching was most
severe and had the highest reported
incidence of occurrence during the
Caribbean-wide event of 1998-1999.
According to the U.S. National Park
Service (NPS), the 1998 bleaching
event coincided with the highest recorded
SSTs in the USVI. Bleaching
was less severe in 1999 probably
because water temperatures were
slightly lower (28.8ºC) during that
year. The 1999 bleaching event did
not result in extensive coral colony
mortality because most colonies recovered
within six months of being
bleached (Nemeth and Sladek-Nowlis,
2001; Nemeth et al., 2003c). For
both years, bleaching was most severe
in St. Croix, followed by St. John,
and then St. Thomas (Figure 4.2).
Diseases
Several diseases have affected coral
community structure and have degraded
coral cover (Table 4.1). Between
1976 and 1989, white band
disease (WBD), bleaching, and hurricanes
reduced the cover of elkhorn
coral (Acropora palmata) by as much
as 85% within the Virgin Islands Na-
tional Park (VINP) and the Buck Is-
Figure 4.2. Annual trends in coral bleaching in the USVI. Upper panel shows the
number of bleaching reports by year and severity. Arrows indicate the Caribbeanwide
bleaching event of 1998-1999. Source: Reefbase 2003, http://www.reefbase.
org, Accessed: 10/23/2003. Lower panel shows the estimated percent of coral tissues
that bleached in 1998-1999. Bars represent the maximum percent of sampled coral
colonies that bleached by island and year. Source: Rogers and Miller, 2001; Nemeth
et al., 2003c.
land Reef National Monument (BIRNM; Gladfelter et al., 1977; Rogers et al., 1982; Edmunds and Witman,
1991; Bythell et al., 1992; Rogers and Beets, 2001). Between December 1997 and May 2001, 14 species of
U.S. Virgin Islands
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