Two new coral bleaching abstracts
Coral Health and Monitoring Program
coral at coral.aoml.erl.gov
Tue Jun 27 19:52:12 EDT 1995
Following are two new coral bleaching abstracts added to the CH&M WWW site:
Gleeson, M.W. and A. E. Strong, 1995: Applying MCSST to coral reef
bleaching, Adv. Space. Res., 16: 151-154.
In the 1980s and early 1990s, coral reef bleaching events of unprecedented
frequency and global extent were observed. Elevated water temperature is
suspected as the primary causal stress of mass bleaching events from this
period. The relationship between sea surface temperatures (SSTs) and
coral bleaching events was investigated using National Oceanic and
Atmospheric Administration (NOAA) Multi-Channel Sea Surface Temperature
(MCSST) satellite imagery from 1982-1992. Nighttime MCSST weekly averages
were compared with moored-buoy temperatures for sea-truthing the
satellite. Average errors from 11 individual buoy comparisons throughout
the tropics were found to be approximately 0.5C. Confirmed satellite SST
data were applied to bleaching events at Bermuda (1988, 1991), Tahiti
(1984, 1987, 1991), and Jamaica (1987, 1989, 1990), with a non- bleached
site off Belize selected as control. MCSST data showed elevated SSTs
coincided with bleaching events both in onset and duration. Bleaching
thresholds were developed. An MCSST Degree Heating Weeks (DHW) bleaching
index was developed for the Belizean and Jamaican reef sites. A
cumulative heating stress of 26 DHW is proposed as the threshold for mass
reef bleaching at Belize and Jamaica.
Montgomery, R.S. and A.E. Strong, 1994: Coral Bleaching Threatens Ocean,
Life. EOS 75: 145-147.
People around the world depend on the resources provided by the ocean
to support life. But global-scale damage to the coral reefs, a large and
integral part of the ocean environment that supports a variety of sea
life, is a frightening scenario that may unfold in the coming years.
Recently, a phenomenon called coral bleaching has raised concerns
about the deteriorating conditions in the world's oceans and the
implications for life on our planet. Coral bleaching occurs as coral
tissue expels zooxanthellae, a symbiotic algae that resides in the
structure of the coral and is essential to its survival. The widespread
nature of the bleaching threatens the state of the environment.
The zooxanthellae, besides giving color to the otherwise white coral
skeleton, produce carbon compounds that nourish the coral. In return, the
coral provides the algae with a home inside its skeletal structure and
nitrogen and phosphorous, which are essential for its survival [Brown and
This delicate symbiosis can be disrupted by several factors, and this
causes the coral to expel the algae. Disturbances such as extremes of
temperature, hypersalinity, pollutants in the water, or changes in
radiation flux cause coral bleaching. The correlation between high water
temperatures and coral bleaching is of acute concern.
In the 1980s, many reefs including those near Easter Island, the
Great Barrier Reef, and the coasts of Central America showed signs of
More nottceable events occurred in 1983 near Panama and in 1987-1988
in the Caribbean [Ghiild, 1990]. The Panama event is connected with the
1982-1983 El Nino, which raised water temperatures in the area to above
The Caribbean event, which lasted for 9 months, was associated with
widespread bleaching in the reefs off Jamaica. Water temperatures in the
area were above 30C at the peak of the bleaching. This event in particular
raised concerns about a possible link between coral bleaching, rising
water temperatures, and global warming [Goreau et al., 1993].
The possibility that a recent warming trend in the world's oceans is
responsible for the recent bleaching events merits further inquiry.
Evidence favoring this hypothesis exists in oceanic and atmospheric
physical data, but until such evidence is examined with known bleaching
events, conclusions cannot be made.
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