This document provides an overview of a seminar on the impact of climate change on coral reefs. It begins with an introduction to coral reefs, their structure and importance. It then discusses several threats from climate change, including increased sea surface temperatures causing coral bleaching, ocean acidification weakening coral skeletons, and rising sea levels submerging some reefs. The document presents two case studies, one on the relationship between bleaching and mortality in Kenya, finding varying impacts across coral taxa. The second examines accelerating bleaching in the Caribbean linked to rising sea temperatures. Overall, the seminar highlights the threats climate change poses to coral reef ecosystems and their biodiversity.

2. Seminar-I
on
Impact of climate change on coral reefs
VINAYAK S THUMBAGI
PG16AEG8155
Dept. Soil and Water Engineering
College of Agril. Engg. Raichur
Chairman:
Dr. Maheshwarababu
Course teacher:
Dr. U. Satishkumar
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3. OVERVIEW
Introduction
Types of coral reef
Case Studies
Conclusion
References
Impact of climate change
on coral reef

4. Introduction
 Coral reefs are spectacular ecosystem found under the sea.
 Corals are invertebrate animals belonging to the family of sea
animals called Cnidaria, a diverse group that includes jellyfish,
hydroids, and sea anemones.
 Corals are colonial organisms made up of individual polyps, each
1–3 mm in diameter, that are connected to one another via a thin
layer of tissue.
 The connection between polyps allows for the sharing of nutrients.
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 Below the soft bodies of stony corals, polyps secrete a calcium
carbonate skeleton, and this skeleton that becomes the foundation
of coral reef ecosystems.
 Coral reefs are complex system which consist of many animals,
including coral and plant.
 When hundreds or thousands of coral polyps build their skeletons
close together, they create a calcium carbonate structure that
provides habitat and food for a variety of organisms. This is
known as a coral reef.
 Corals are found in different shapes, colours and size

6. Coral polyps
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 Corals need shallow water and sunlight to survive.
 A group of single-celled dinoflagellates that live in the tissue of
corals is called Zooxanthellae.
 The zooxanthellae living in the soft tissue of a coral polyp use
sunlight to produce food through photosynthesis. Thus,
zooxanthellae provide corals with food, in return, the coral
provides the zooxanthellae with shelter and nutrients.
 zooxanthellae supplies the needed energy for corals to secrete
layers of calcium carbonate.

8. Anatomy of a Coral Polyp
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TENTACLES
SKELETON
Mouth

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 Most reef-building corals contain photosynthetic algae, called
zooxanthellae. Zooxanthellae live in the polyp’s tissue.
 This algae provides food for the coral and the coral gives the
Zooxanthellae a home.
 Light must be able to penetrate the water to the depth of a coral to
allow the symbiotic zooxanthellae to photosynthesize. symbiotic
zooxanthellae supply 90% of nutritional needs of stony coral.
 Also capture and consume live prey using their tentacles (Night)

10. Location
Coral reefs are located in tropical oceans near the equator.
91.9% of the worlds coral reef are found in the indo pacific region (Indian
ocean, western pacific)
 They are found in more than 100 countries.

11. Types of coral reefs
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 There are 3 Different types of Coral reefs namely:
1. Fringing Reef
2. Barrier Reef
3. Atoll
1. Fringing Reef : Fringing reefs
develop in shallow waters along the
coast of tropical and subtropical
islands. This reef is attached, laying
adjacent to the shore of the island or
continent. This type of coral reef is
found in the Caribbean and Red sea.

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2. Barrier Reef : The reef is located in the
Coral Sea, off the coast of Queensland,
Australia. it is called The great barrier
reef. It grows parallel to the coastline but
is separated by a lagoon. The lagoon
develops between the fringing reef and
land.
3. Atoll : An atoll is a ring shaped coral
reef or island. It surrounds a lagoon. An
atoll often sits on the rim of an extinct
volcano.

13. Importance of coral reefs
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 The ridges in coral reefs can reduce wave energy, this protects us
from threats such as tsunami’s.
 The reef acts as barriers that help protect 14% of the worlds
coastlines from erosion caused by waters. Hence the name “the
barrier reef”
 Coral reefs are home to thousands of different species.
 Coral extracts have been used for treatment of cancer, asthma,
arthritis, and heart disease. It has also been used for bone
replacement.

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 Coral reefs help moderate atmospheric temperature by removing
𝐶𝑂2 from the atmosphere.
 Coral reefs contribute to the economy as many people earn a
living from collecting and processing reef products.
 Coral reefs are also a tourist attraction as many people love to see
this amazing creation.
 Corals provide food for other marine life.
 Corals support fish population.

15. Impact of climate change on coral reefs are:
Increased sea surface temperatures.
Ocean acidification
Solar radiation
Rising sea level
Sedimentation
Desalinisation
Viral infection
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16. Increased sea surface temperatures.
The warming ocean waters do affect coral by directly impacting
the coral symbiotic, Zooxanthellae. Zooxanthellae are highly
sensitive to temperature.
Changes and usually thrive in temperatures within the range of
23-29 °C, beyond which bleaching occurs (Henkel, 2010).
The major impacts are Coral bleaching, Coral diseases and Affect
other reef organisms.
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17. Coral bleaching
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19. Increase in Sea surface temperature
(SST)
SSTs in the Pacific, Atlantic and Indian Ocean
Highest in the last 40,0000 years
Increased 0.4～0.7℃ in the last century

20. Temperature effect on condition of coral
reefs in future.
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21. Ocean acidification
 Burning of fossil fuels and deforestation have increased the amount
of carbon dioxide emitted to the atmosphere and the amount that
dissolve into the ocean.
 It will cause ocean become more acidic.
 If atmospheric CO2 reaches 450 ppm, coral reef growth around the
world is expected to slow down considerably and at 550 ppm reefs
are expected to start to dissolve. CO2 level of below 350 ppm
appears to be required for the long-term survival of coral reefs. The
currently level of acidity is about 390 ppm.
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 As increase in ocean acidity, coral skeletons will be weaker
and grow more slowly, and a shrinking coral population
means these reef dependent species ( rest of the food chain )
will suffer.

23. Climate change and acidification
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24. Solar radiation
 Increased solar radiation, both in the visible (400–700 nm) and the
ultraviolet (290–400 nm) regions of the spectrum, have also been
variably implicated in mass coral bleaching (Andrew et al., 2008).
 Higher rates of UV radiation as a result of atmospheric ozone
depletion are potentially an important element of global change,
with harmful future effects on coral reef ecosystems.
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 Organisms living in shallow-water tropical coral reef environments
are exposed to high UVR irradiances due to the low solar zenith
angles (the angle of the sun from the vertical), the natural thinness
of the ozone layer over tropical latitudes, and the high transparency
of the water column.

26. Rising sea level
Global sea level has already increased 20 cm over the past century as a
consequence of thermal expansion and melting of land-based ice.
The major impacts are :
Coastal erosion
Higher storm surges
‘Drowning’ of some reefs
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27. Case study - 1
“The relationship between bleaching and mortality of common corals”
by,
McClanahan, T. R.,
(2004)
Marine biology
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28. Objectives
 Recording the loss of color (bleaching) and observing recently
dead individuals among 6,803 colonies during five sampling
periods.
 Estimating mortality based on 180 m of line-intercept transects
completed 4 months before and near the end of the bleaching
episode.
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29. MATERIALS AND METHODOLOGY
Location : Mombasa Marine National Park (MNP)
The study was undertaken along a continuous fringing back-reef
lagoon of the Mombasa Marine between November 1997 and
September 1998.
The study area included hard bottom areas between 1 to 6 m
depths, depending on the tide, on the leeward side of Kenya’s
fringing reef.
The site is approximately 1 km from shore and protected from all
forms of resource extraction.
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30. Colour response
• The colour response is based on observations of 6,803 coral
colonies selected during five sampling periods between March and
September 1998.
• Colonies were sampled by swimming, this process was continued
until less than 650 coral colonies were sampled, but in most cases
more than 1600 colonies were sampled per period. selecting all
corals colonies within a 2 m radius for colour categorization.
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 Number of individual coral colonies sampled for each taxon during each
sampling period in the Mombasa Marine National Park in 1998.

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Massive
BranchingShort branching
Encrusting

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Each colony was identified to the genus and categorized into the
following six categories:
 unbleached (normal coloration),
 pale (lighter color than usual for the time of year),
 0–20% of the surface bleached,
 20–50% bleached,
 50–80% bleached, and
 80–100% bleached

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 examples of Porites lutea taxa
a. unbleached (normal coloration)
b. pale (lighter color than usual for the time of year),
c. 20–50% partially bleached coral.
d. A fully bleached coral on the left and one of normal color on the right

35. Death estimates
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 Estimates of death due to warm water are based on two
methods:
(1) direct observations of dead corals in the color surveys.
(2) line-intercept transects undertaken 4 months before and at the
bleaching event, which is referred to as mortality.

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 Scatterplot of the relationship between percentage mortality based on line
transects before and after the bleaching episode and observed dead of the
18 taxa.
Results and discussion

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 The average of the observed dead for the 18 taxa was significantly
lower (17.0±5.2%) than mortality estimated from the line transects
(41.2±8.2%).
 The highest correspondence between the observed dead and mortality
was for taxa that experienced mortality of <10%. These taxa were
Astreopora, Favia, Favites, Goniopora, Leptoria and Pavona.
 Of the 15, taxa that lost color, five taxa, Astreopora, Favia, Favites,
Goniopora, and Leptoria, did not die. These taxa are those most likely
to have reduced potential mortality by the loss of pigments and
associated algal symbionts.

38. Conclusion
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 There was no clear relationship between the loss of color and either
direct observation or transect-based estimates of mortality for the 18
taxa.
 The morphology of the taxa did not influence color loss but branching
and encrusting taxa had higher mortality than massive and submassive
taxa.
 Loss of color and mortality are the most common responses to warm
water as only Pavona, did not lose color or die and only two taxa,
Cyphastrea and Millepora, did not significantly lose color but died.

39. Case study - 2
“Accelerating impacts of temperature-induced coral bleaching in the
caribbean”
John, P. M., Isabelle, M. C., Jennifer, A. G., William, J. S., and
Andrew, R. W., (2005)
Centre for Ecology, Evolution and Conservation, School of Environmental
Sciences, University of East Anglia,
Norwich NR4 7TJ.
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40. MATERIALS AND METHODOLOGY
• Materials – They are collated reports of bleaching occurring on
Caribbean coral reefs between 1983 and 2000 from published
literature, email correspondence and internet sources.
• The main bleaching period in the Caribbean occurs during the summer
specifically from August to October.
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 Distribution of bleaching reports in the Caribbean between 1983 and 2000 in
relation to month of onset of bleaching. Reports from August to October..

42. They are used two estimates of regional
bleaching severity:
1. Bleaching extent : Regional bleaching extent was obtained for
every year by counting the number of cells reporting bleaching
and calculating the area over which bleached cells were
distributed using minimum convex polygons.
2. Bleaching intensity : Regional bleaching intensity was calculated
by averaging multiple values (percentage of colonies bleached),
first within individual cells, and then using cells across the region
to produce one intensity value per year.
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 Each data point represents
one year.
 Solid circles represent years
described in the literature as
mass bleaching events, open
circles represent other years.
 The dashed line shows the
SST at which maximum
bleaching extent.
Results and discussion

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 The relationship between
regional SST anomalies
and the area encompassing
all cells reporting
bleaching from 1983 to
2000.
 Solid circles represent
years mass bleaching
events; open circles
represent other years.

45. Conclusion
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 ‘‘Increasing SST anomalies’’ are used here to increasingly positive
temperature anomalies. Summer (August–October) SST anomalies
increased from 1983 to 2000 with the maximum anomaly occurring
in 1998 (+0.72ºC) and the minimum in 1984 (0.51ºC).
 A 0.1O C increase in regional SST produces a 35% increase in the
number of coral reef cells reporting bleaching and a 42% increase in
the mean percentage of coral colonies affected by bleaching.

46. Overall Conclusion
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 Taking care of our marine life is extremely important. Coral reefs provide the
world with a complex and diverse habitat that supports many organisms.
 They also provide coastal protection as they absorb wave energy, many island
would not exist today if it were not for coral reefs.
 It also contribute to the economy because of tourism and fisheries.
 Save the coral reefs and you save the world, It begins with you.

47. References
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1. Andrew, C. B., Peter, W. G. and Bernhard, R., 2008, Climate change and coral reef
bleaching An ecological assessment of long-term impacts, recovery trends and future
outlook. Estuarine Coastal and Shelf Sci., 80:435–471.
2. Henkel, T. P., 2010, Nature education citation Coral Reefs. Dept of Biology, Murray
State Univ., 3(10):1-5.
3. John, P. M., Isabellem, M. C., Jennifer, A. G., William, J. S. and Andrew, R. W., 2005,
Accelerating impacts of temperature-induced coral bleaching in the Caribbean.
Ecology., 86(8):2055–2060.
4. Janice, M. L., 2007, 10th Anniversary Review: a changing climate for coral reefs. J. of
Environ. Monitoring., 10(1):1-148.

48. 48
1. McClanahan, T. R., 2004, The relationship between bleaching and mortality of
common corals., Marine biology., 144:1239–1245.
2. Mahabir, R., 2016, Coral reefs challenges, opportunities and evolutionary strategies for
surviving climate change in the caribbean. J. of Mason Graduate Res., 3(2): 71-96.

49. THANK YOU