Re: Caribbean Coral Die-Off Could Be Worst Ever
<TABLE id=apex_layout_271110100662109808 class=formlayout border=0 summary=""><TBODY><TR><TD noWrap align=right>
Archive Number</TD><TD noWrap align=left>20101020.3796</TD></TR><TR><TD noWrap align=right>
Published Date</TD><TD noWrap align=left>20-OCT-2010</TD></TR><TR><TD noWrap align=right>
Subject</TD><TD noWrap align=left>PRO/AH/EDR> Coral reef bleaching - Caribbean: temperature related</TD></TR></TBODY></TABLE>
CORAL REEF BLEACHING - CARIBBEAN: TEMPERATURE RELATED*****************************************************A ProMED-mail post<
http://www.promedmail.org>ProMED-mail is a program of theInternational Society for Infectious Diseases<
http://www.isid.org>Date: Thu 14 Oct 2010Source: ScienceNow [edited]<
http://news.sciencemag.org/sciencenow/2010/10/caribbean-coral-die-off-could-be.html>
</PRE>
Scientists studying Caribbean reefs say that 2010 may be the worst
year ever for coral death there. Abnormally warm water since June
appears to have dealt a blow to shallow and deep-sea corals that is
likely to top the devastation of 2005, when 80 percent of corals were
bleached and as many as 40 percent died in areas on the eastern side
of the Caribbean.
Bleaching occurs when crucial microorganisms leave coral reefs during
stress. Corals, which shelter a quarter or more of all marine
species, get bleached, and may die, after prolonged heating. A few
weeks of water temperatures a few degrees above normal can be fatal.
During the 2005 die-off, for example, water temperatures off the
Virgin Islands rose just 3 deg C above the average in August-but
stayed that way until November. "There has been little recovery in
the Caribbean since," says reef specialist C Mark Eakin of the US
National Oceanic and Atmospheric Administration (NOAA) in Silver
Spring, Maryland.
In July of last year [2009], NOAA warned that bleaching was again
likely. Now, temperature maps indicate that the water has remained
hot for longer than in the 2005 episode and the abnormal warmth
spreads over a much broader area (see images at
<
http://news.sciencemag.org/sciencenow/assets/2010/10/14/sn-coral2.jpg>).
The episode 5 years ago hit the Lesser Antilles on the eastern side
of the Caribbean as far south as Guadeloupe. This year [2010], the
bleaching and high temperatures have devastated reefs in the Dutch
Antilles and affected coral along the western and southern sides of
the sea. Those include reefs off Panama and the island of Curacao
near Venezuela. That island's maximum monthly average surface water
temperature is 28.5 deg C [83.3 deg F]; it was 30.2 deg C [86.4 deg
F] for the month of September [2010].
"I've never seen bleaching like [it] in Panama," said Nancy Knowlton,
a coral biologist at the Smithsonian Tropical Research Institute in
Panama who has been studying the local flora for 25 years. She and
colleague Hector Guzman have seen massive reefs die in recent weeks
in the enclosed lagoon of Bocas del Toro in Panama after becoming
coated with giant sheets of slime, the remains of dead
microorganisms. "This is NOT a normal condition on reefs, even
bleached reefs. Where last year [2009] there were healthy corals,
this year [2010] there was only gray ooze," she wrote in an e-mail.
A lack of wind prevents the mixing that would add cool water and
alleviate the die-off. In some areas, says Guzman, the water "is like
a Jacuzzi" and the sea life is dead, extra salty, and low in needed
dissolved oxygen. "I'm trying to be positive," says Guzman, who notes
that some wind has remixed and cooled the waters. "I have seen reefs
get wiped out and come back the next year." But the devastation is
"more dramatic" than he has seen before, affecting hard corals,
sponges, and sea anemones.
A number of factors besides water temperature can cause coral
bleaching and die-offs, including pollution and storms. But
temperature is the number-one culprit in such a massive die-off, says
Eakin. The warmest 12-month period in the NASA temperature record
ended this summer [2010]; June through August was the 4th warmest
such period in the record. The extent of the devastation across the
Caribbean will become clear in the coming months as biologists
measure the deaths.
[Byline: Eli Kintisch]
*This article has been corrected. In 2009, NOAA warned in 2009 that
coral bleaching was likely to happen again, not in 2010.
--
Communicated by:
ProMED-mail
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promed@promedmail.org>
[Corals live in very nutrient poor waters and have certain zones of
tolerance to water temperature, salinity, UV radiation, opacity, and
nutrient quantities.
Scleractinian corals build skeletons of calcium carbonate sequestered
from the water. When the coral polyp dies, this skeleton remains
incorporated in the reef framework.
Scleractinian corals are in the phylum Cnidaria, and they receive
their nutrient and energy resources in 2 ways: they use the
traditional cnidarian strategy of capturing tiny planktonic organisms
with their nematocyst capped tentacles, as well as having an obligate
symbiotic relationship with a single cell algae known as
zooxanthellae. Zooxanthellae are autotrophic microalgae belonging to
various taxa in the phylum Dinoflagellata.
Zooxanthellae live symbiotically within the coral polyp tissues and
assist the coral in nutrient production through its photosynthetic
activities. These activities provide the coral with fixed carbon
compounds for energy, enhance calcification, and mediate elemental
nutrient flux. The host coral polyp in return provides its
zooxanthellae with a protected environment to live within, and a
steady supply of carbon dioxide for its photosynthetic processes. The
symbiotic relationship allows the slow growing corals to compete with
the faster growing multicellular algae because of the tight coupling
of resources and the fact that the corals can feed by day through
photosynthesis and by night through predation.
The tissues of corals themselves are actually not the beautiful
colors of the coral reef, but are instead clear. The corals receive
their coloration from the zooxanthellae living within their tissues.
Bleaching, or the paling of zooxanthellate invertebrates, occurs when
(1) the densities of zooxanthellae decline and/or (2) the
concentration of photosynthetic pigments within the zooxanthellae
fall (Kleppel et al. 1989). Most reef-building corals normally
contain around 1-5 x 10 to the 6th zooxanthellae per cm squared of
live surface tissue and 2-10 pg of chlorophyll a per zooxanthella.
When corals bleach they commonly lose 60-90 percent of their
zooxanthellae and each zooxanthella may lose 50-80 percent of its
photosynthetic pigments (Glynn 1996). The pale appearance of bleached
scleractinian corals and hydrocorals is due to the cnidarian's
calcareous skeleton showing through the translucent tissues (that are
nearly devoid of pigmented zooxanthellae).
If the stress-causing bleaching is not too severe and if it decreases
in time, the affected corals usually regain their symbiotic algae
within several weeks or a few months. If zooxanthellae loss is
prolonged, that is, if the stress continues and depleted
zooxanthellae populations do not recover, the coral host eventually
dies.
The article does not tell us of alkalinity of the water, only
temperatures. If temperatures are the only cause, which is highly
unlikely, are hurricanes then a productive thing as they bring rain
and prevent the temperatures from going too high?
Portions of this comment have been extracted from
<
http://www.marinebiology.org/coralbleaching.htm>. - Mod.TG]
[Maps of the region are available at
<
http://geology.com/world/caribbean-map.gif> and
<
http://healthmap.org/r/0dZi>. - Sr.Tech.Ed.MJ]
[see also:
Montipora white syndrome, coral reef - USA (02): (HI)
20100415.1220
Montipora white syndrome, coral reef - USA: (HI)
20100403.1078
2007
----
Vibrio, rare coral - UK
20070905.2933
Coral reef kill - Costa Rica
20070904.2915
Coral reef kill - Pacific Region
20070810.2600
2004
----
Coral reef kills - USA (FL) (02)
20040327.0846
Coral reef kills - USA (FL)
20040320.0777
2002
----
Coral reef kills, unknown etiology - Australia
20021023.5624
Coral reef kills, human waste suspected - Caribbean
20020627.4622
2000
----
Coral reef kills - Belize
20000510.0713
1999
----
Coral reef kills & potential human disease (02)
19990204.0161
Coral reef kills & potential human disease
19990124.0111
1998
----
Coral reef bleaching & El Nino - Indian Ocean (02)
19981113.2187
Coral reef bleaching, El Nino effects - Indian Ocean
19980705.1246
Coral reef kills, etiology determined - USA
19980415.0693
1996
--
White pox, coral reefs - Florida, USA (02)
19961231.2165
White Pox, coral reefs - Florida, USA
19961228.2160]
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