Coral Reef/Lithosphere Analysis
Winnie Billiel, Melissa DeCarlo, Mark Jackson,
Maria Rivera, and Jason Wright
The lithosphere is the outermost part of the earth’s surface. It is broken up into many plates that
are constantly moving and shifting. These shifting plates lead to all kinds of natural processes
(such as volcanoes, rise and fall of sea floor, etc.) that can have a real impact on the health of
coral reefs. Here are a few ways in which the lithosphere and the health of corals are closely
interconnected. The L listed will represent the lithosphere, and the E will represent the event
(loss of coral reefs).
L>E
Plate tectonics describes the large scale movements of earth’s lithosphere. We see this effect
with things such as tsunamis and earthquakes. Some may have little effect while others can be
deadly. Deadly not only to human lives but also on other animals, even coral reefs. It can either
cause the coral to sink well below normal depths of sustainable growth or far above the surface
of the water. Both of which has a dramatic impact on the coral reefs. An example of this was the
earthquake that hit Ranongga Island in the Solomon Islands that moved 80% of its fringing reef
permanently above sea level. Land thrust from the quake extended out the shoreline of Ranongga
Island by up to 70 meters. Northern reefs thrusted 1m above the high tide water height, whereas
on the south side reefs moved 2 to 3m above the water.
Ranongga is an island located in the
New Georgia Islands group of
Western Province, Solomon Islands.
Coral Reef/Lithosphere Analysis
Winnie Billiel, Melissa DeCarlo, Mark Jackson,
Maria Rivera, and Jason Wright
L>E
Terrestrial can pose a severe threat to the health of surrounding coral reefs. Sediment can be
washed away from exposed soil that lies next to a reef ecosystem. This can cause turbidity levels
to rise blocking the sun which will affect the symbiotic relationship it has with the algae that live
in them. The impacts of sedimentation usually occur in tropical islands with high elevation. The
picture below shows an area in Maui, Hawaii that has exposed soil close to the coastal reef
system. Not only does sedimentation affect the reefs but an over abundance of fertilization that
gets washed into the water can cause an algae bloom that will choke the coral polyps stressing
them out.
Another impact of sedimentation is when the polyps get buried by sediment the corals are forced
to expend a great deal of energy just to keep their surfaces clean. This excessive use of their
energy burns them out and weakening them. This may not cause them to die but hinders their
growth greatly.
A week long laboratory experiment of Hawaiian coral conducted by Greg Piniak and Eric Brown
of the U.S. Geological Survey determined that exposure to sedimentation is detrimental to the
life of the coral. Two different species of corals were tested over a 6-45 hour period. They were
exposed to terrigenous mud and carbonate sand. As you can see the corals did not fair too well.
A pulse-amplitude-modulated (PAM) fluorometer was used to measure stress effects (whatever
that is). Short term (6 hour) exposure time did little damage but the coral were able to bounce
back. However, long term (30 or more hours) the corals were severely damaged.
Two of the coral species
tested. They did not fair
too well.
Coral Reef/Lithosphere Analysis
Winnie Billiel, Melissa DeCarlo, Mark Jackson,
Maria Rivera, and Jason Wright
L>E
There were two major earthquakes in the waters offshore of Aceh during 2004 and 2005. The
first, which occurred on 26 December 2004 and generated the destructive tsunami, was reported
to measure magnitude 9.15, and the second in March 2005, registered 8.7.
Hundreds of large aftershocks have since occurred. Both of the major earthquakes
tilted several islands including Simeulue, Nias and parts of the Banyak archipelago. This pushed
shallow water reef flats above the high tide mark, resulting in 100% mortality as seen in the
photo below.
L>E
Coral grow very slowly—between .5 and 2.8 centimeters per year. Under normal
circumstances, any fluctuation in sea level (possibly due to global warming, or ice ages) typically
would occur over a long period of time. . . .plenty of time for the corals to adjust to the changing
conditions. However, if there was an abrupt change in sea level (such as an oceanic plate being
thrust upward thanks to plate tectonics) this could cause a real problem for corals. In the case of
the megathrust fault that lead to the Indian ocean tsunami of December 26th, 2004, some parts of
the sea floor were displaced by as much as 20 meters. This is far too great a change for any coral
to survive.
L>E
I don’t know, this one may not be right, but I was thinking that a way the lithosphere
affects the event is the fact that corals are only found near the equator. Is that one? Their latitude
affects their survival? No?
Coral Reef/Lithosphere Analysis
Winnie Billiel, Melissa DeCarlo, Mark Jackson,
Maria Rivera, and Jason Wright
L>E
When glaciers melt, the sea levels rise, thus killing the coral. Coral needs to be close to the
surface so that the alga that lives on it can perform photosynthesis. The alga gives nutrients to the
coral. According to climate experts, sea level has risen by 2 mm per year. The melting of
glaciers, ice caps and polar ice sheets as well as heating of the ocean has contributed to seal level
rise. Sea level is expected to increase in the range of 6 to 37.5 inches (15 to 95 cm) over the next
century. The vertical growth rate of coral is likely to be slower than this increase. As a result,
corals will be deeper, receive less sunlight and grow more slowly. The combined effect of deeper
reefs and slower growth will cause two problems for coastal areas: 1) corals will not be able to
protect the shore as effectively and wave energy could increase in strength; and 2) smaller reefs
will produce smaller mounts of reef sediment which builds and supports island land-bases.
L>E
When volcanoes erupt, the ash and smoke can block the sunlight from the surface of the earth.
This results in a lower temperature. Without the sunlight, the alga cannot perform photosynthesis
causing it to die. Without the alga, the coral will die.
Smoke rings
from Stromboli
L>E
Underwater, large stands of toppled broken coral lined the south coast of Pulau Weh. The
damage was found along a 7 km long, 50 m wide series of patch reefs comprised of blue coral at
2 - 6 m depth. This damage was likely caused by the earthquake that disrupted the lithosphere.
The December earthquake was the fourth largest in history. The total energy released has been
estimated as 1.1×1018 joules or about 0.25 gigatons of TNT. The earthquake was so powerful that
it moved the Earth's surface vertically by up to 1 cm and altered the Earth's rotation. In many
areas, the earthquakes caused instantaneous uplifting of the seafloor by several meters. The
second earthquake was also powerful. Such energy and movement could easily dislodge and
break up corals located nearby.
Coral Reef/Lithosphere Analysis
Winnie Billiel, Melissa DeCarlo, Mark Jackson,
Maria Rivera, and Jason Wright
L>E
After the earthquake, the sediment from the lithosphere was displaced due to the disturbance.
This led to a high turbidity in the water which led to sedimentation of the coral. Sediments can
settle directly on top of corals and smother them. Corals are not capable of moving, and most
coral have very poor mechanisms with which to remove sediments from on top of them.
Sediments in the water affect water clarity, making the water cloudy or turbid. High turbidity
reduces the amount of light that gets through the water column to the corals, and reduces the
ability of zooxanthelle to photosynthesize.
L>E
Charles Darwin proposed that atolls begin with a coral reef growing around a volcanic island.
The disruption of the lithosphere occurs when the volcano erupts. Over thousands of years, as
sea levels change and as the volcano subsides, or sinks, the coral reef grows upwards.
First an island is formed
by a volcano, then corals
start to grow as a fringing
reef around the island.
Over time the volcano dies
and starts to erode and
subside, while the corals
grow up into a large
barrier reef around the
volcanic island. The old
volcanic island continues
to subside and sink
beneath the sea, while the
coral reef continues to
grow upwards,
maintaining a coral island at the sea surface. Given the slow growth of coral and lots of time, an
old volcanic island can subside far below the surface of the sea, while a coral reef perched atop
the island continuously grows upwards keeping the reef at sea level even while its volcanic roots
subside deep beneath it. This dual process of the volcano sinking and the corals growing
eventually leads to the familiar circle shape of an atoll. It is now known that an atoll can take as
long as 30 million years to form. This lithospheric event contributes to the healthy formation of
coral.
L>E
During the winter of 1992 (following the eruption of Mount Pinatubo, a volcano in the
Philippines) coral were observed dying in the Gulf of Aqaba (an area located in the northern part
of the Red Sea). It was the coldest winter on record in the past 46 years that weather records had
been documented. The volcanic eruption ejected large amounts of sulfuric acid high into the
atmosphere. This gas reflected sunlight, resulting in the cooler than average weather. Soon after,
Coral Reef/Lithosphere Analysis
Winnie Billiel, Melissa DeCarlo, Mark Jackson,
Maria Rivera, and Jason Wright
the Red Sea coral began to die. Scientists quickly looked for possible reasons—volcanic dust's
smothering the coral, presence of hydrogen sulfide (H2S), disease, or some combination of
causes. However, when scientists measured water temperatures, they found cold water mixed
very thoroughly throughout the water column. Normally, cold water is usually found in very
deep water, with warmer water near the surface (just think about the swimming pool in the back
yard!). Here's what happened: The unusually cold surface water had sunk (because it was more
dense than normal), helping to mix the water column. This also helped to bring up nutrients (like
phosphorous) that normally stay in the deep, cold water, up near to the surface. This resulted in
the growth of thick, red algal blooms. Scientists believe that they smothered the coral, blocking
out the sunlight. When temperatures returned to normal (meaning warm water is now at the
surface, preventing the nutrient rich water from beneath to come near the surface), the algal
blooms died because they no longer had the nutrients they needed. The reefs were soon healthy
again. This is one way that the lithosphere can have a dramatic impact on the health of coral
reefs.
This is a caption of the Mt. Pinatubo eruption of July,
1991. This single lithospheric event is thought to have
been responsible for the degradation of many coral
reefs in the surrounding area.
L>E
When drought occurs in many parts of Africa, numerous dust storms plague the
surrounding areas. West African dust, which is thickest during drought years, is transported by
winds all across the continent, spreading even up to the Caribbean. This dust carries the fungus
aspergillus, which thrives on sea fans, a type of coral. During times of extreme drought and high
winds, a tremendous amount of material (dirt and dust) is transported to the ocean and seas. Once
there, the fungus latches on and begins attacking the coral, negatively impacting the reef. Also,
large quantities of dust can also block out the sun's rays from above the water, resulting in
reduced photosynthesis. As you know, zooxanthellae algae live symbiotically with the corals,
providing them with the bulk of their nutritional requirements. If these algae become stressed or
Coral Reef/Lithosphere Analysis
Winnie Billiel, Melissa DeCarlo, Mark Jackson,
Maria Rivera, and Jason Wright
die (due to the lack of sunlight for photosynthesis) the coral becomes stressed as well, resulting
in a condition called coral bleaching. Below is an illustration that shows some ‘stressed out’
coral.
Barbados Mineral Dust Annual Average and Benchmark Caribbean Events: The graph below,
courtesy of Dr. Joe Prospero, University of Miami, shows the overall increase in African dust
reaching the Caribbean island of Barbados since 1965. Notice the peak years for the dust
deposition were 1983 and 1987. These were also years of extensive environmental change on
Caribbean coral reefs.
Coral Reef/Lithosphere Analysis
Winnie Billiel, Melissa DeCarlo, Mark Jackson,
Maria Rivera, and Jason Wright
E>L
Coral reefs provide a barrier for the coastal regions during storms
H>E
Coral reefs are very selective in their range of water quality that they can tolerate. They
require very warm, very clear tropical waters. If there are any changes (even subtle changes in
temperature, turbidity, etc.) to the water quality, this could negatively affect the coral reef.
E>B
The loss of coral reef will cause a dramatic decrease in biodiversity.
L>E>B
Coral reefs do not do well in areas where there is a lot of freshwater river runoff, because they
prefer salt The silt from the river runoff can cover a reef or muddy the water, thus blocking the
sunlight. If the sunlight is blocked, the algae cannot perform photosynthesis so they will die. The
coral relies on the algae for food.
E>L>B
Coral secretes calcium carbonate which builds into a limestone scaffolding providing a home to
many species of marine life.
A>H>E
Here’s a doomsday hypothetical idea I had (I love these) . . . Any sudden change in the
climate (such as global warming) could potentially (and abruptly) change sea level due to the
loss of polar ice. This sudden increase in sea level may put the corals in a deeper water
environment that may not be beneficial for their survival.
A>H>E
As our atmosphere continues to store more carbon dioxide and sulfur dioxide, this can
(along with other factors) contribute to acid precipitation. As this acidic precipitation enters the
ocean (through rainfall), this could alter the pH of the surface water of the ocean, right where the
corals live.
L>H>B>E
As soil erosion near the coast increases (due to natural reasons, commercial development,
etc.) this causes the water to become cloudy (turbid) which can choke out the algae living within
the coral reef. These algae provide the bulk of the nutritional requirements for the coral.
L>H>B>E
Another way of looking at this same connection is . . . if the runoff coming from land
contains fertilizers or other organic contaminants (such as sewage / manure) this will increase the
nutrient content of the water (particularly the phosphate and nitrates). Phosphates are a key
ingredient to triggering algal blooms. Algal blooms are detrimental to the reef because they
Coral Reef/Lithosphere Analysis
Winnie Billiel, Melissa DeCarlo, Mark Jackson,
Maria Rivera, and Jason Wright
block the sunlight while the algae are alive, and then as they die (due to lack of nutrients) they
settle and coat the corals, choking them out.
References
http://www.cotf.edu/ete/modules/coralreef/CRlitho.html
http://earthobservatory.nasa.gov/IOTD/view.php?id=7609
http://en.wikipedia.org/wiki/Plate_tectonics
http://soundwaves.usgs.gov/2004/11/
http://pubs.usgs.gov/fs/2002/fs025-02/
www.usgs.gov
this site was helpful in many of the images
www.cotf.edu/ete/
this site was used for the lithosphere interactions
http://www.panda.org/about_our_earth/aboutcc/problems/people_at_risk/personal_stories/witnes
s_stories/?116880
http://www.decadevolcano.net/photos/stromboli_photos.htm
http://www.coral.org/node/126