Coral Reef & Mangrove Swamps
What are coral reefs?
What is the importance of coral reefs?
What are the general threats to coral reefs?
What are mangrove swamps?
What is the importance of mangroves?
What are the general threats to mangroves?
Coral Reefs
• What are coral reefs?
– Massive living calcium carbonate structures
primarily built by corals
• Corals are colonies of invertebrate animals
called coral polyps.
Structure of Coral
Because the
zooxanthellae are plants,
they need sunlight to
photosynthesize, so they
need to find a part of
their host animal which is
not regularly shaded, that
sunlight can't penetrate
Brown zooxanthellae inside tentacles of a
coral polyp
Reef-forming corals, would be unable to build
their calcium carbonate skeletons without the
nutrients provided by their zooxanthellae
Where are coral reefs located?
The majority of reef building corals are found within tropical and subtropical waters. These typically occur between 300
north and 300 south latitudes. The red dots on this map show the location of major stony coral reefs of the world.
Credit:NOAA
Structure (Types) of Coral Reefs
•
Barrier- Barrier reefs are platforms separated from the
shoreline by a channel or a lagoon. The longest barrier
reefs are found along the coasts of Belize and Australia.
Fringing reefs, the most
common type, extend
outward from a body of land
with no water separating the
reef from land.
Atolls are coral islands that
usually consist of a narrow,
horseshoe shaped reef with a
shallow, central lagoon. Over
300 atolls are found
throughout the South Pacific.
Function of Reefs
• Function as breakwaters
• Act as producers and recyclers - they rapidly convert carbon and
nutrients into food through photosynthesis.
• Provide food and shelter for plants and animals
• “Cleaning stations” - Smaller animals may appear to be "picking" or
"biting" a larger one, with the "victim" doing nothing to defend itself.
This is actually cleaning behavior; the smaller fish is removing
parasites, debris, or infected tissue from the skin of the larger fish. The
cleaner lives in a semi-permanent territory called a "cleaning station",
which other fish recognize. Both parties benefit from this relationship:
the larger fish gets rid of an irritant and the cleaner gets a meal
without being harmed. (Symbiotic relationship – mutualistic)
• Some reef organisms transform biologically unavailable atmospheric
nitrogen gas into a form useful for coral and plant growth.
Value of Coral Reefs
According to one estimate, coral reefs goods
and services are worth about 0 $375 billion each
year.
Shoreline protection
Source of food
Recreation/Tourism
Diverse communities
Coral Reefs in crisis –
What’s happening to our coral reefs?
Recent report from the Global Coral Reef Monitoring Network estimates that 25% of the world's
reefs are already gone or severely damaged and that another third are degraded and
threatened. This coral reef crisis is happening here at home in the U.S. and in far away places, in
some of the most remote areas of the world.
• overexploitation of resources for subsistence and commercial fishing;
• destructive fishing practices that degrade and destroy the habitat itself;
• increasing coastal populations, which are expected to double in the next 50 years;
• poor land use practices and runoff of pollutants, sediments and nutrients;
• disease outbreaks, which may be associated with poor water quality and pollutants;
• coral bleaching, associated with increasing seawater temperatures and sedimentation
• removal of coastal mangrove forests.
Major threats to Coral Reefs
• Overfishing (including aquarium
collection)
• Human Population Growth
• Pollution
• Sediment/Turbidity
• Nutrient Enrichment
• Invasive Species
• Bleaching
What can we do?
–
–
–
–
–
–
–
–
–
–
Conserve water: The less water you use, the less runoff and wastewater will pollute our oceans.
Help reduce pollution: Walk, bike or ride the bus. Fossil fuel emissions from cars and industry
raise lead to ocean warming which causes mass-bleaching of corals and can lead to widespread
destruction of reefs.
Use only ecological or organic fertilizers: Although you may live thousands of miles from a
coral reef ecosystem, these products flow into the water system, pollute the ocean, and can harm
coral reefs and marine life.
Dispose of your trash properly: Don't leave unwanted fishing lines or nets in the water or on the
beach. Any kind of litter pollutes the water and can harm the reef and the fish.
Support reef-friendly businesses: Ask the fishing, boating, hotel, aquarium, dive or snorkeling
operators how they protect the reef. Be sure they care for the living reef ecosystem and ask if the
organization responsible is part of a coral reef ecosystem management effort.
Plant a tree: Trees reduce runoff into the oceans. You will also contribute to reversing the
warming of our planet and the rising temperatures of our oceans.
Practice safe and responsible diving and snorkeling: Do not touch the reef or anchor your
boat on the reef. Contact with the coral will damage the delicate coral animals, and anchoring on
the reef can kill it, so look for sandy bottom or use moorings if available.
Volunteer for a coral reef cleanup: You don't live near a coral reef? Then do what many people
do with their vacation: visit a coral reef. Spend an afternoon enjoying the beauty of one of the
most diverse ecosystems on the Earth.
Contact your government representatives: Demand they take action to protect coral reefs, stop
sewage pollution of our oceans, expand marine protected areas and take steps to reverse global
warming.
Spread the word
Mangrove Swamps
• If there are no mangrove forests, then the
sea will have no meaning. It is like having
a tree with no roots, for the mangroves are
the roots of the sea."
Structure
•
•
•
Mangrove swamps are found along
tropical seacoasts on both sides of the
equator. They are named for the
Mangrove trees that grow there.
Mangrove swamps, to most people,
look like muddy, swampy places filled
with mosquitoes, snakes and spiders.
The term "mangrove" refers both to the
many species of salt tolerant trees
which may be found in a mangrove
swamp, and to the actual area in which
these salt tolerant trees are dominant.
Actually, they are a forest community
that bridges the gap between land and
sea. Mangroves are found along muddy
estuaries of large rivers, and in
sheltered intertidal coastal settings that
include lagoons, bays, tidal creeks and
inlets.
To avoid suffocation in the oxygen poor mud, mangrove
trees snorkel for air. They develop aerial or air-breathing
roots. These take in aboveground air. Only air can get
through the lenticels, not water or salts.
All aerial roots also contain large air spaces These not
only transport air, but also provide a reservoir of air
during high tide when all the aerial roots may be
underwater.
The function of aerial roots are to absorb air or/and to
provide structural support in the soft mud. Roots for
absorbing nutrients are tiny and emerge near the muddy
surface.
Function
• Mangrove root systems provide a filtering system for run-off
from the guts of our islands, allowing the sediments to be
removed before entering open water. This sediment would
otherwise cover and kill coral reef colonies.
• Protect land from soil erosion
• Pollution control
• Flood control
• Provide food
• Nursery areas
Incredible Fact!
If you were to scoop up just one teaspoon of mud from a North
Queensland, Australia Mangrove Swamp and look at it under a
very strong microscope, you would find that it contains more
than 10 billion bacteria - that's among the highest found in
marine mud anywhere in the world!
Bacteria helps break down leaf litter and other bits of natural
material. Lots of bacteria tells biologists that these swamps are
producing lots of leaves and other sources of nutrition for plants
and animals, making Mangrove Swamps an immensely
important coastal habitat.
Value
•
•
•
•
Flood control
Nursery for many species of marine life
Pharmaceutical
Economic
– Mangroves are a rich source of timber which
can be harvested on a sustainable basis.
– Some mangrove animals, like the proboscis
monkeys of Borneo with their unusual noses, are
tourist attractions and thus generate income.
Threats to Mangrove Swamps
•
Clearing: Mangrove forests have often been seen as unproductive and smelly, and so cleared to make
room for agricultural land, human settlements and infrastructure (such as harbors), and industrial areas.
More recently, clearing for tourist developments, shrimp aquaculture, and salt farms has also taken place.
This clearing is a major factor behind mangrove loss around the word.
•
Overharvesting: Mangrove trees are used for firewood, construction wood, wood chip and pulp
production, charcoal production, and animal fodder. While harvesting has taken place for centuries, in
some parts of the world it is no longer sustainable, threatening the future of the forests.
•
River changes: Dams and irrigation reduce the amount of water reaching mangrove forests, changing the
salinity level of water in the forest. If salinity becomes too high, the mangroves cannot survive. Freshwater
diversions can also lead to mangroves drying out. In addition, increased erosion due to land deforestation
can massively increase the amount of sediment in rivers. This can overcome the mangrove forest’s filtering
ability, leading to the forest being smothered.
•
Overfishing: The global overfishing crisis facing the world’s oceans has effects far beyond the directly
overfished population. The ecological balance of food chains and mangrove fish communities can also be
altered.
•
Destruction of coral reefs: Coral reefs provide the first barrier against currents and strong waves. When
they are destroyed, the stronger-than-normal waves and currents reaching the coast can undermine the
fine sediment in which the mangroves grow. This can prevent seedlings from taking root and wash away
nutrients essential for mangrove ecosystems.
•
Pollution: Fertilizers, pesticides, and other toxic man-made chemicals carried by river systems from
sources upstream can kill animals living in mangrove forests, while oil pollution can smother mangrove
roots and suffocate the trees.
•
Climate change: Mangrove forests require stable sea levels for long-term survival. They are therefore
extremely sensitive to current rising sea levels caused by global warming and climate change.