1. The Undersea Environment of Coral Reefs
Coral reefs are the most biologically diverse marine ecosystems on earth, rivaled only by
the tropical rainforests. They provide homes and nurseries for almost a million
fish and other species. Incredibly, coral reefs occupy only one quarter of one percent
of the earth's marine environment, yet they are home to more than a quarter of all
known fish species. Let’s take a look at these fascinating communities under
the sea that have been in existence for almost 200 million years.

2. Presentation Overview
Biological characteristics of reefs
Functions of reefs
Potential Diseases and Hazards
These are the three important topics we will discuss in this presentation.

3. Coral reefs are like undersea cities.
Communities of coral reefs can be compared to our cities. They are complex
ecosystems that rely on the various occupants and the surrounding environment
to sustain their vitality. These undersea cities provide food, shelter,
and breeding grounds for their inhabitants.

4. Each coral within a reef is similar to an apartment complex in a neighborhood with many tenants
Corals can be compared to a condominium - a home for many different
people. A coral reef is simply a community of many of these condominiums,
or coral homes.
There are many species of coral that grow throughout the world’s oceans, but
most all corals have common structural characteristics. Corals have been in
existence for nearly 200 million years but reached their current level of
diversity only 50 million years ago.

5. A coral is actually a home for billions of tiny soft-bodied animals called coral polyps.
Is a coral an animal or a plant? Many people think that because corals stay
stationary on the bottom of the ocean that they are plants. In fact,
a coral is actually a home for billions of tiny soft-bodied animals called coral
polyps.

6. These polyps reside within a cup-like calcium carbonate skeleton
These polyps reside within a cup-like calcium carbonate skeleton. They have a central opening surrounded by tentacles which can be extended to feed on phytoplankton in the water column.
A coral contains a very thin outer layer of living coral polyps. Although
most corals contain hundreds or thousands of polyps, some contain
only one. The polyp is a hollow, cylindrical animal with a mouth that
is surrounded by tentacles armed with stinging cells for capturing
food. Underneath these coral polyps is the dead coral skeleton
composed of calcium carbonate. Each coral polyp excretes a calcareous
exo-skeleton that lives in a symbiotic relationship with zooxanthellae,
host algae located in the tissue of the polyp, that gives the coral its
green, blue, purple or brown color.

7. There are two different types of corals
Hard Corals known as scleractinians
Soft Corals know as gorgonians
There are two main types of corals; hard corals composed of stony
calcium carbonate, and soft corals made up of a protien/calcium
carbonate material. Scleractinians, or hard corals such as brain, star,
staghorn, elkhorn and pillar corals have rigid exoskeletons, or corallites,
that protect their soft delicate bodies. Gorgonians, or soft corals
such as sea fans, sea whips and sea rods, sway with the currents and
lack an exoskeleton.
Soft coral
Hard coral

8. Corals are located in three primary locations
Western North Atlantic
Indo-Pacific
Coral reefs are located in three primary regions of the world oceans:
the Indo-Pacific, the Western North Atlantic, and the Red Sea. These three regions lie between 20N and 20 S of the equator. The Indo-
Pacific region stretches from Southeast Asia through Polynesia and
Australia, eastward across the Indian Ocean to Africa. This is the largest
and richest assemblage of reefs in terms of coral and fish species present.
The Western North Atlantic region stretches from Florida to Brazil, and
Includes Bermuda, the Bahamas, the Caribbean, Belize and the Gulf of
Mexico. The Red Sea is the smallest of the three regions, located between
Africa and Saudi Arabia. It is considered a separate region because of
the high number of coral reefs found only in this area.
Red Sea
Indo-Pacific

9. They survive in unique conditions that require...
Adequate sunlight
Water temperatures between Celsius
Shallow water depths
Low siltation
In order for corals to live, they require healthy living conditions including
adequate sunlight, clean water with low levels of siltation, relatively shallow
depths and stable water temperatures. Drastic changes in any of these
Conditions for significant periods of time can contribute to the death of corals.

10. Corals obtain food via…..
Zooxanthellae photosynthesis
Predation upon zooplankton and phytoplankton
Absorption of dissolved organic material
Corals obtain their food in three ways. One is through zooxanthellae photosynthesis.
Photosynthesis, as you may remember, is the process plants use to convert trapped sunlight energy, water and
carbon dioxide into oxygen and carbohydrates (sugar). The zooxanthellae take in carbon dioxide through
photosynthesis, and then give off oxygen as a by-product that is used by the host polyp. Both oxygen and
carbohydrates are essential elements in the energy production of corals. Algae “leak” these elements into the polyp’s
tissue where they are absorbed and used for energy production. Besides playing an important role in coral nutrition,
zooxanthellae are also essential in the process of skeleton deposition. The polyp, on the other hand, provides protection
for the algae.
Corals also obtain their food through more active means. They prey on different types of algae called zooplankton and
phytoplankton. These microscopic algae generally float in the water, although some are able to swim short distances,
migrating from the bottom of the reef during the day, and back up to the top at night. This is why feeding, for most marine
Organisms, is much more active at night.
The corals “come alive” at night, eating by extending tentacles to capture their prey. The coral nematocysts
sting and immobilize their prey so that the tentacles can withdraw and bring the food down into digestive cavity
of the polyp. Polyps can also release mucus in the form of thin sheets over the whole colony or in strands or sheets into
the water. Plankton, bacteria and organic debris get stuck to mucus and, the cilia on the tentacles help to bring
the mucus back into the digestive cavity.
The third way corals obtain food is through the absorption of dissolved organic molecules (DOM), particulate organic
material (POM), and from sharing of food. For example, DOM such as glucose and certain amino acids can be absorbed
from water through the polyp's body wall by means of tiny fuzzy projections called "microvilli.” These organic molecules
enter the water column from decomposing animals and plants. Particulate organic material, such as bacteria, decomposing
organic matter and fish fecal material (detritus), are directly ingested by the polyp. Food can also be shared in some species
of colonial corals whose digestive cavities are interconnected Thus, food obtained by one polyp can be transported throughout
it's own body or to other polyps.

11. Reefs play important roles in the coastal and ocean environment
Habitats for many marine species
Breeding grounds for lobster, shrimp, and various fish
Food and shelter
Barriers protecting the coasts from storms
Sources of sand for beaches
Recreational areas for snorkelers, divers and fishermen
Coral reef ecosystems have important ecological and economic functions for our
coastal regions. It is evident that the reef is a significant link to the vitality and
sustainability of other environments.
Reefs form a natural and self-repairing barrier that protects the coasts by absorbing
violent wave impacts of ocean storms and hurricanes. Corals and calcareous algae are
major sources of sand. Fish graze on coral and then excrete organic material that
contributes to the bottom sediment. Reefs also provide habitat, shelter, food and
breeding grounds for many commercially valuable species such as lobsters, shrimp,
grouper and snapper.
Many regions located close to reefs rely heavily on these fragile ecosystems for their
economic stability. Take the Florida Keys for example. This region depends on nearly
2 million tourists visiting the Keys and their coral reefs annually. Tourists come to
snorkel, fish, scuba dive and see the sites. Commercial and recreational fishing is another
industry that relies on the health of the reefs. The coral reefs support the fish that attract
local fisherman, the second-most important economic and traditional force in the Keys.

12. Reefs also clean the surrounding water through sponges that have filtering systems similar to water treatment plants
Another function of the reef is to clean and filter surrounding waters.
In this way, reefs can be compared to water treatment plants. Filter-
feeding sponges, bivalve mollusks, crustaceans, worms, and echinoderms
all help to clean the waters surrounding the reef.

13. Many natural and human-induced factors can harm reefs
Bioerosion by fishes and other marine organisms
Diseases
Storms
Overfishing
Coastal development
Pollution
Several frequently observed conditions have been identified as harmful
to corals: black band disease (BBD), white band disease (WBD), bioerosion,
and coral bleaching. These conditions are all stress-related. However,
anthropogenic, or human-caused, stresses can increase a coral's
susceptibility to these conditions.

14. Many inhabitants, such as angelfish and parrotfish, utilize the reef as a source of food and shelter. But too much feeding causes bioerosion of the reef.
Another condition that can cause coral mortality in the reef
is bioerosion. For example, the sea urchin Diadema antillarum functions
as both a grazer on algae that can smother coral, and as a bioeroder of
corals as it feeds on them. Other bioeroders include crown of thorns,
parrot fish, and boring worms. All of these marine organisms manage
to weaken the coral structure the coral skeleton, making it more
susceptible to breakage during storms.

15. Global warming causes increases in water temperature which can cause harm to the coral reef environment in the form of coral bleaching.
Coral bleaching is a symptom of the stress that occurs when water temperatures
exceed the coral’s maximum tolerable temperature range. Corals
typically grow in warm tropical waters between degrees Fahrenheit.
Coral bleaching occurs when sea temperatures rise or when other stresses occur
That cause the corals to expel their symbiotic algae.

16. Diseases such as blackband and whiteband disease are caused by excessive warming of waters
Two diseases frequently observed on corals are blackband and whiteband disease.
These diseases actually kill coral tissue while advancing in a band around the
coral and leaving the white coral skeleton behind. When blackband disease
kills part of a colony, the skeleton is then available to be colonized by other
coral species recruits. In fact, some scientists suggest that blackband disease
may actually help maintain coral diversity because it is most prevalent in coral
species that form large colonies. Studies have shown, however, that there were
no coral recruits among corals infected by blackband disease after 25 months.
It is believed that whiteband disease is caused by a bacterial pathogen not
yet known. It affects corals much as blackband disease , leaving behind a white,
lifeless coral skeleton. Unlike blackband disease , scientists do not see whiteband
disease as being beneficial to reefs. Scientists have shown that whiteband disease
destroys the reef structure because algae, invertebrates, gastropods and boring
sponges colonize the dead coral skeleton. This colonization works to weaken the coral
skeleton,making it more susceptible to breakage during storms.

17. We need to protect our reefs not only for their intrinsic value, but for the economic and recreational resources they provide.
Coral reefs deserve protection not only for their intrinsic natural value, but also
for the economic benefits - such as tourism, fishing and recreational resources - they
provide to tropical areas around the world. If we don't get involved in protecting these
fragile ecosystems, the first generation to discover scuba may be the last to enjoy
coral reefs.