Coral bleaching

1. FROM EDEN TO DESERT
JUVIN ANN THOMAS

2. WHAT ARE CORALS – PLANTS OR
ANIMALS ?

3. THE RAINFORESTS OF SEA
• Corals are marine
invertebrates in the class of
Anthozoa of Phylum Cnidaria.
• They live in compact colonies
of many identical individual
polyps.
• Over many generatios,
secreting exoskeleton, the
colony creates a large skeleton
characteristics of the species

4. ZOOXANTHELLAE
Zooxanthellae are
single celled
dinoflagellates.
They are
photosynthetic
organisms which
contain chlorophyll a
and c, as well as the
dinoflagellate
pigments peridin and
diadinoxanthin.

5. AN ENDOSYMBIOTIC RELATIONSHIP
The zooxanthallea produce
carbohydrate by
photosynthesis.
In turn, corals provide
shelter for the
dinoflagellates.
They help in exoskeleton
formation
Give coloration to the
corals.

6. CORAL ZOOXANTHALLEA SYMBIOSIS

7. CORAL BLEACHING
• It is the physiological stress response of coral
reefs – the most rapid and destructive impact of
global climate change.
• The term coral bleaching is derived from the
whitening of the tissue of reef
• The expulsion of zooxanthellae, thus loss of the
photosynthetic pigments allowing the white
aragonite skeleton to visible through the
transparent coral tissue.

10. Map showing the bleaching of Great barrier reef

11. WHAT CAUSES CORALS TO EXPEL THEIR
SOULMATES ?
• Increase of water temperature
• Change in acidity of water
• Oil spills
• Increase in sea level
• Low tide and exposure
• Herbicides
• Cyanide fishing

12. Increase of water temperature(Global
Warming)
Extreme hot sea water disrupt the nature
of coral.
 Coral cannot adapt the fast changing
climate temperature.
 Sudden change of temperature caused
the expulsion of zooxanthellea
Temperature increases of only 1.5 –2°C
lasting for six to eight weeks are enough
to trigger bleaching.

13. Increase in sea level
•Sea level increase due to
melting of ice caps as
resulted from
greenhouse effect , coral
will be deeper, thus
prevent coral to get
enough sunlight

14. Increase in acidity of water
• As the CO2 in the atmosphere increase, it
affect the sea
• The increase in CO2 simultaneously increase
the acidity of water.
• Coral act as a shield for zooxanthellae. High
water acidity disturb the formation of coral.

15. OIL SPILLS

16. BACTERIAL INFECTION
• Bleaching has also been found to occur as a direct result of
bacterial infection in the coral tissue, particularly by gram-
negative bacteria of the genus Vibrio.
• Bleaching of the Mediterranean coral Oculina patagonica was
caused by Vibrio shiloi, which produces extracellular proline-
rich peptides referred to as Toxin P, which blocks
photosynthesis and bleaches and lyses zooxanthellae.
• Virulence factors for adhesion and ingress into the coral and
Toxin P are produced by the bacterium only at elevated
seawater temperatures

17. Bacteria infected Corals

18. Herbicides and pesticides
• The herbicides and pesticides
used in land eventually run off
to the ocean.
• These hazardous chemicals kill
the corals

19. Cyanide fishing
Cyanide is poisonous to coral.
Fisherman use cyanide to stun
the fish and make it easy to catch
alive

20. DEATH OF THE BEAUTY

21. BLEACHING EVENTS
The past two decades have seen several incidents of widespread coral
bleaching events on many of the world’s coral reefs.
In 2016, record oceans temperatures have led to record widespread coral
bleaching on Australian coral reefs. This bleaching is part of the
ongoing third global bleaching event, declared by the National Oceanic and
Atmospheric Administration (NOAA) in 2015.
Between February and May, the Great Barrier Reef experienced record
warm sea surface temperatures. Extensive field surveys and aerial surveys
found bleaching was the most widespread and severe in the Far Northern
management area, between Cape York and Port Douglas. Here, bleaching
intensity was ‘Severe’ (more than 60% community bleaching). Bleaching
intensity decreased along a southerly gradient.

22. 2008–2011
• In the summers of 2008-2009 and 2010-2011, extreme summer seasons were
associated with extremely high rainfall in Queensland. This led to flooding and
the discharge of large amounts of freshwater to nearshore reefs resulting in
freshwater bleaching.
• The Reef is likely to experience more frequent and more serious thermal and
freshwater stresses in the future, given current rates of global warming due
to increasing levels of atmospheric greenhouse gases
2005–2006
In January and February 2006, a bleaching event took place in the
southern Reef, especially around the Keppel Islands. AIMS (Australian
Institute of Marine Sciences) surveys revealed that, although bleaching
was largely confined to this region, the degree of bleaching was worse
than in previous years. Up to 98 per cent of corals bleached on some
reefs, resulting in nearly 39 per cent mortality on the reef flats and
32 per cent on the reef slopes.

23. HELPING HAND
• Researchers are getting promising early results from cross-breeding
different species of reef-building corals, rapidly developing new
strains of the symbiotic algae that corals rely on and testing
inoculations of protective bacteria. They are also mapping out the
genomes of the algae to assess the potential for genetic engineering.
• “It is a story of hope, rather than saying ‘it’s all going to die and
there’s nothing we can do about it’,” said Prof Madeleine van Oppen,
from the Australian Institute of Marine Science and the University
of Melbourne.

24. Spawning of corals in
Horniman museum

25. THANKYOU

26. REFERENCES
• Grahamm Jeremiah Plass Johnson. “Coral Bleaching”. Technical
university of Denmark
• https://www.aims.gov.au/docs/research/climate.../coral-
bleaching/bleaching-events.ht.
• https://oceanservice.noaa.gov/facts/coral_bleach
• https://en.wikipedia.org/wiki/Coral_bleaching
• www.gbrmpa.gov.au