Download An underwater nightmare: Global warming and

An underwater nightmare:
Global warming and coral disease
Half of all coral reefs in danger,
experts warn global warming cited;
U.S. warns of major event in
Caribbean
Caribbean coral suffers record
die-off World's coral reef loss
'an underwater holocaust'
Friday, March 31, 2006
WASHINGTON (AP) -- A one-two
punch of bleaching from record hot
water followed by disease has killed
ancient and delicate coral in the
biggest loss of reefs scientists have
ever seen in Caribbean waters.
THERMAL STRESS INDUCES
PATHOGENIC EFFECTS OF VIBRIO
SPECIES ON INDO- PACIFIC AND
CARIBBEAN SYMBIOTIC REEF
BUILDING CORALS
Jane McClanahan & Dr. James Cervino
Department of Biological and Health Sciences
Pace University
Questions to answer
• What is the coral-algal
symbiosis?
• What are threats are
disrupting the symbiosis?
• How is global warming
affecting coral disease?
Goals of our research
• Determine if heat stress causes symbiotic
algae cells to become immunocompromised
• Identify the cell death pathways of Vibriobacteria infected zooxanthellae
• Compare amounts of apoptotic cells from
Vibrio-infected zooxanthellae to controls
• Identify possible heat-induced toxins
produced by Vibrio
Coral reefs are the most climatically
sensitive ecosystems on the planet
Reef health can be used as an indicator of rising seasurface temperatures
Why are corals important?
• Biodiversity
• Coastal
protection
• Economic value
• Fish protein
Biodiversity
4,000 species of fish
800 species of hard coral
Rising Seawater Temperatures
1-2C Above the warmest
summer average
Great Barrier Reef 2002-2006 left more
than 30 percent of the reef destroyed.
Today, 65% of the worlds reefs are dying
due to temperature stress, diseases and chemical pollution
(US Coral Reef Task Force, NOAA)
Corals: plant or animal?
…a little bit of both!
• 1 millimeter of
LIVING animal tissue
on top of massive
calcium carbonate
(limestone) skeleton
• thousands of polyps
form a colony
• Stings prey
(zooplankton) with
tentacles
• Non-mobile, can’t
escape stress such as
predators or disease
What is Zooxanthellae?
Reef-building coral animals have single-celled
plants living within their tissues…..Why?
• Single-celled plant (algae) living within the coral
tissues uses energy from the sun for photosynthesis
• Products of photosynthesis, such has glucose and
oxygen, are used by the coral
(AN EXTRA SOURCE OF FOOD)
• Zooxanthellae use coral waste products (nitrogen,
CO2) for photosynthesis
• Like a self-sufficient recycling system
• Algae helps coral to deposit skeleton
• Almost all the coral’s color comes from the
zooxanthellae
Zooxanthellae: coral’s solar power
Coral Reef Disease
Coral diseases: what is known?
• Out of 18 coral diseases known, pathogens
have been identified for 4 of them:
• Yellow Band Disease: vibrio spp, shellfish
pathogens
• Black Band Disease
• Sea fan disease: aspergillosis soil fungus
• White plague (bacteria), affects 18 diff spp, 1
cm/day
• White pox: sewage pathogen (human gut)
9/1997
Yellow Band Disease
12/1997
BBD
3/1996
2/1997
Yellow Band
Vibrio-induced Yellow Band Disease
• Infection caused by 4 Vibrio bacteria species
• Causes yellow lesions
• Effects the zooxanthellae directly, not the
coral host
• Higher rate of infectivity at higher
temperatures
• Same group of bacteria in Pacific and
Caribbean
Yellow-band causing Vibrio bacteria
Yellow band disease causes the
destruction of zooxanthellae in-situ
Coral Mortality
100
80
60
40
20
0
20
22
24
26
Temperature C
28
30
32
What are the cell death
mechanisms when corals
are subjected to thermal
stress and infected with
shell-fish Vibrio pathogens?
Bacterial Mat &
Zoox
Healthy
Zooxanthellae
lysis
Fragmented
degenerate
zoox Titlyanov
(1996).
Internal
structures
Begin to shrink
Healthy
PCD in zoox
described
in Dunn et al.,
(2001).
PCD?
Apoptosis
(Dunn et al. 2002)
Bacterial Lysis
Fragmented
Degenerate
Alga
The effects of Vibrio on zooxanthellae
Starch crystals
Transmission Electron Microscopy
Shrinkage
CL
CL
AC
C-W
S
Cl
v
N
N
S
After Vibrio 24 hrs
Apoptosis
Special thanks Marine Biological Lab
Woods Hole MA.
Control 24 hrs
Why does the Yellow Band
infection intensify with
temperature?
• How does temperature affect the
zooxanthellae?
• Does temperature stress make
zooxanthellae more susceptible to
infection?
Presentation at the 106th General Meeting
May 24, 2006
VIBRIO INFECTION INTENSIFIES FOLLOWING THERMAL
STRESS ON ZOOXANTHELLAE CLADE SPECIES IN
CULTURE and in THE PACIFIC ANEMONE
STICHODATYLA SP.
J.M. Cervino1, Pace University, New York NY
J.M. McClanahan2, Pace University, New York NY
E.A. Lorence3, Pace University, New York NY
F. Thompson4, Universidade Estadual de Campinas, BR
T.J. Goreau5, Global Coral Reef Alliance, Cambridge MA
R.L. Hayes6, College of Medicine, Howard University, Washington D.C.
Our results
• Specific species of symbiotic
zooxanthellae are the targets of Vibrio
infection
• Temperature weakens the “immune
system” of algae, which affects growth
• Lower cell division
• Lower densities
• Lysed apoptotic cells
Implications
• ID which zoox are most susceptible to
infection
• ID usual zoox-host partnerships
• Prediction of which coral species will be
affected by Yellow Band
What can we do to reduce stress
on corals?
Influence policy makers to immediately address the
significant impacts that heat-trapping carbon
emissions have on coral reefs in the tropics
Black Band Disease
• Affects major reef builders
• Linked to pollution
• Caused by a consortium of
bacteria
• Grows in a slimy mat over
the coral surface
Sea Fan Disease
• Caused by Aspergillosis, a soil
fungus
• Deforestation and excavating
cause the soil fungus to be
washed down rivers and into the
ocean – onto the reef
environment
White Plague
• Caused by a bacteria
• Affects 18 different
species of coral
• Often mistaken for
bleaching
Thermal Bleaching
The most severe threat to corals worldwide
Global warming is causing thermal bleaching
on a massive scale
The Great Barrier Reef has suffered severe damage
What is bleaching?
• When temps exceed 1-2C above the
summer average
• Zooxanthellae are expelled
• Lack of pigment in tissue makes it become
translucent, skeleton becomes visible
• Coral starves from lack of energy
• Immune system is weakened, coral
becomes more susceptible to pathogens
Thermal bleaching
Healthy, with pigment
Bleached – no
zooxanthellae
Corals worldwide suffer from bleaching
Bonaire, 2001
Fully Bleached
For more information about coral reef disease
contact James Cervino, PhD
Biological and Health Sciences Dept.
[email protected]