Title: Response to coral bleaching in U.S. Virgin Islands National Parks
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Permanent Link: http://ufdc.ufl.edu/CA01300639/00001
 Material Information
Title: Response to coral bleaching in U.S. Virgin Islands National Parks
Physical Description: Book
Language: English
Creator: United States Geological Survey
National Park Service ( Contributor )
Publisher: United States Geological Survey
Publication Date: 2006
 Subjects
Subject: Caribbean   ( lcsh )
Spatial Coverage: North America -- United States Virgin Islands -- Saint John -- Virgin Islands National Park
Caribbean
 Record Information
Bibliographic ID: CA01300639
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.

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National Park Service
U.S. Geological Survey
U.S. Department of the Interior


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Response to Coral Bleaching

in U.S. Virgin Islands National Parks

A major increase in sea temperatures
led to unprecedented bleaching
of corals in 2005 in the Eastern
Caribbean including the U.S. Virgin
Islands where national parks were
particularly hard hit.

What is Coral Bleaching?
Environmental stress can cause corals to lose
symbiotic algae (zooxanthellae) that live inside
their tissue, which leaves the tissue transparent
and reveals the white coral skeleton underneath.
This potentially fatal reaction gives the coral a .
"bleached" appearance. Bleached corals within Virgin Islands National Park.


Initial Assessment of Bleaching and Disease
The National Park Service (NPS) and U.S.
Geological Survey (USGS) intensified coral
monitoring as soon as water temperatures began
to rise in early September 2005 to assess the
scale and impact of bleaching on coral reefs in
the National Parks. An average of 90% of coral
cover bleached at six long-term monitoring
sites at Virgin Islands National Park on St. John
and Buck Island Reef National Monument on
St. Croix. Many corals began to recover from
bleaching and then suffered a "one-two punch"
when they were afflicted by disease. Greater than
40% loss of live coral cover occurred at Tektite
Reef and more than 20% at Haulover Reef on St.
John. Of the over 460 elkhorn colonies that are
being monitored at four reefs in Virgin Islands
National Park by scientists from USGS, NPS
and the University of the Virgin Islands, about
45% bleached, 13% died partially, and 8% died
completely. This bleaching and disease episode
highlights the importance of reducing stresses
on coral reefs and enhancing their resilience to
future bleaching events.

NPS/USGS Coral Monitoring Programs in the
Parks
The NPS South Florida/Caribbean Inventory
and Monitoring Network Program (NPS-SFCN)
has 120 video transects grouped into six study
sites around Virgin Islands National Park in St.
John and Buck Island Reef National Monument
off St. Croix, US Virgin Islands. Repeat digital


video recordings of coral colonies provide an
extensive visual record, which is analyzed to
track changes including bleaching and diseases.
Established in 1999, this program enables the
Park Service to statistically quantify changes
in coral cover and condition of reefs with high
coral abundance and habitat complexity USGS
Caribbean Field Station is monitoring 460 Elk-
horn coral (A. palmata) colonies for bleaching
and diseases in four zones around St. John each
month. All of the NPS-SFCN and USGS sites
are geo-referenced and have underwater tem-
perature data loggers, collecting data every two
hours. Biologists at Buck Island Reef National
Monument on St. Croix conduct long term coral
monitoring at numerous sites within the park,
and initiated additional site surveys in response
to bleaching in 2005.

Impacts of Bleaching and Disease
The 2005 bleaching episode is the most severe
ever recorded in the U.S. Virgin Islands. An av-
erage of 90% of coral cover bleached at the six
NPS-SFCN study sites. This bleaching episode
was followed immediately by a severe outbreak
of coral disease that affected primarily the major
reef building species (e.g., brain and star cor-
als). Together with scientists from the USGS
Caribbean Field Station, NPS-SFCN collected
additional data to quantify coral mortality from
a severe outbreak of coral disease that followed


Parks could serve
as "replenishment
reserves" by protecting
resilient corals and
helping coral reefs
endure future bleaching
events and other
stressors.






National Park Service
U.S. Department of the Interior

Water Resources Division
WASO-NRPC
P.O. Box 25287
Denver, CO 80225-0287


the bleaching episode. Measurements of disease
mortality were taken along with tissue samples
for microbial analysis. Assessment results from
two study sites are available and reveal greater
than 40% loss of live coral cover at Tektite Reef
and more than 20% loss at Haulover Reef. Ex-
tensive disease mortality has been observed at
depths ranging from 10-100 feet.

Losses Affecting Elkhorn Coral (Acropora
palmata)
Of the over 460 elkhorn colonies that are be-
ing monitored at four reefs in Virgin Islands
National Park by scientists with USGS, NPS
and the University of the Virgin Islands, about
45% bleached, 13% died partially, and 8% died
completely. However, white pox and other un-
identified diseases have caused greater losses
than bleaching at two of these sites. Bleaching
of elkhorn was more severe within Buck Island
Reef National Monument than on reefs around
St. John. Elkhorn coral (Acropora palmata) once
defined and dominated shallow Caribbean coral
reefs. With its complex branching morphology
and large size, Elkhorn coral reefs provide habi-
tat for fishes and many other organisms includ-
ing endangered hawksbill sea turtles. It is now
being proposed for listing as threatened under
the Endangered Species Act because of exten-
sive losses from disease and hurricanes in the
1970s and 1980s. In the last 15 years, new elkhorn
colonies have begun to grow on many Caribbean
reefs, including within Virgin Islands National
Park, Virgin Islands Coral Reef National Monu-
ment, and Buck Island Reef National Monu-
ment. However, disease and physical damage
from natural and human causes are limiting its
recovery. During the recent bleaching episode,
elkhorn coral bleached for the first time on re-


cord in the US Virgin Islands, which led directly
to the death of many colonies.

Implications for Resource Managers
This event exemplifies how the delicate eco-
logical balance of coral reefs can so easily be
disrupted. Coral reef ecosystems are deteriorat-
ing from stresses such as sustained, higher sea
temperatures, pollution, fishing, and physical
damage. Management actions to improve water
quality, prevent over-fishing, physical damage
and overuse, and minimize reef degradation will
reduce stresses on coral reefs and create a foun-
dation for ensuring their recovery and long-term
survival. Parks could serve as "replenishment re-
serves" by protecting resilient corals and helping
coral reefs endure future bleaching events and
other stressors.

Future Monitoring and Research
Scientists are beginning to frame questions about
the variability in how corals respond to bleach-
ing and disease. USGS plans to investigate these
patterns by looking at genotypes of the host
corals and the types ("clades") of zooxanthel-
lae found in corals that either resist or succumb
to bleaching, using a recently developed swab
sampling technique that does not harm the coral
colony. Research may identify types of corals that
could be more resistant than others to bleach-
ing and disease. USGS and NPS are particularly
concerned about incidence of disease occurring
around this bleaching event and the correlations
between disease outbreaks, bleaching, and water
temperatures. In addition, NPS and USGS are
working closely with the National Oceanic and
Atmospheric Administration (NOAA) on bio-
geographic assessments of coral reefs, including
bleaching and recovery.


Ten national parks are working
to conserve valuable coral reef
resources. In 2005, the National
Oceanic and Atmospheric
Administration proposed both
elkhorn (shown here bleached on
the left and healthy on the right)
and staghorn coral for listing as
threatened under the Endangered
Species Act.

APRIL 2006


EXPERIENCE YOUR AMERICATM


9


Contacts:

Cliff McCreedy
Marine Resource Program Leader
National Park Service
202-513-7164
cliff_mccreedy@nps.gov

Jeff Miller
Fisheries Biologist
National Park Service
340-693-8950 ext. 227
williamj_miller@nps.gov

Dr. Colleen W. Charles
Assistant Program Coordinator
Terrestrial, Freshwater, and Ma-
rine Ecosystems Program
U.S. Geological Survey
703-648-4110
colleen_charles@usgs.gov

Dr. Caroline S. Rogers
Marine Ecologist
Carribbean Field Station
U.S. Geological Survey
340-693-8950 ext 221
caroline_rogers@usgs.gov




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