W9: Coral Reefs

Corals are *anthozoans*, the largest class of organisms within the phylum *________*. Comprising over 6,000 known species, anthozoans also include sea fans, sea pansies and anemones

*Cnidaria*

*Corals are _______, even though they may exhibit some of the characteristics of plants and are often mistaken for rocks. In scientific classification, corals fall under the phylum Cnidaria and the class Anthozoa. They are relatives of jellyfish and anemones.*

*animals*

The effects of El Niño during 1998 and 2004 are an example of the natural factors that influence the growth of coral reefs. During this El Niño, sea temperatures rose and many coral reefs were *________* or obliterated.

*bleached*

*Massive coral _________ occurred in the Great Barrier Reef of Australia between 1998 and 2002 and in reefs in the Indian Ocean, the Maldives, Sri Lanka, Kenya, Tanzania, and the Seychelles. Most areas in the Great Barrier Reef rebounded with little damage but in some areas approximately 90% of the coral has vanished.*

*bleaching*

While coral polyps have structurally simple body plans, they possess several distinctive cellular structures. One of these is called a *___________*—a type of cell unique to, and characteristic of, all cnidarians. Found throughout the tentacles and epidermis, *_________s* contain organelles called cnidae, which include nematocysts, a type of stinging cell.

*cnidocyte*

*Corals are in fact animals that fall under the phylum Cnidaria and the class Anthozoa. They are relatives of __________ and anemones*

*jellyfish*

*Creatures found in coral ecosystems are important sources of new _________ being developed to induce and ease labor; treat cancer, arthritis, asthma, ulcers, human bacterial infections, heart disease, viruses, and other diseases; as well as sources of nutritional supplements, enzymes, and cosmetics*

*medicines*

*The best growing habitat for coral reefs is a clear-water photic zone less than 50 m deep where light shines down and microscopic algae can best provide ______________ for the corals.*

*photosynthesis*

Coral reefs are built by millions of coral *______*, small colonial animals resembling overturned jellyfish that use excess carbon dioxide in the water from the atmosphere and turn it into limestone.

*polyps*

*Fringing* _____, which are the most common, project seaward directly from the shore, forming borders along the shoreline and surrounding islands. *Barrier* _____ also border shorelines, but at a greater distance. They are separated from their adjacent land mass by a lagoon of open, often deep water. If a fringing ____ forms around a volcanic island that subsides completely below sea level while the coral continues to grow upward, an *atoll* forms.

*reefs*

*Coral reefs are extremely sensitive to changes in light, temperature (bleaching), overfishing, damaging fishing practices, pollution, and excess ________ from development and erosion.*

*sediment*

The *________* provides 75-80% of the energy the coral needs to survive.

*symbiont*

Coral

. The limestone skeleton of tiny sea animals.

*Coral extracts have been used to develop treatments for:*

1. Asthma. 2. Arthritis. 3. Cancer. 4. Heart disease.

The NOAA National Marine Fisheries Service estimates the annual commercial value of US fisheries from coral reefs to be over $___ ________.

100 million

There are over ____ species of sharks in the world's oceans, and many live around coral reefs.

500

Zooxanthellae often are critical elements in the continuing health of reef-building corals. As much as _____ of the organic material they manufacture photosynthetically is transferred to the host coral tissue. If these algal cells are expelled by the polyps, which can occur if the colony undergoes prolonged physiological stress, the host may die shortly afterwards.

90%

Thylakoid

A flattened membrane sac inside the chloroplast, used to convert light energy into chemical energy.

*Coral Bleaching*

A phenomenon in which algae inside corals die, causing the corals to turn white.

Coral Reef

A structure of calcite skeletons built up by coral animals in warm, shallow ocean water.

Chloroplast

An organelle found in plant and algae cells where photosynthesis occurs; *where the damage happens during coral bleaching.*

Colonies of reef-building (hermatypic) corals exhibit a wide range of shapes, but most can be classified within ten general forms. _________ corals have branches that also have (secondary) branches. Digitate corals look like fingers or clumps of cigars and have no secondary branches. Table corals are table-like structures of fused branches. Elkhorn coral has large, flattened branches.

Branching

Reactive Oxygen Molecules

Cause oxidative damage by stealing electrons from other compounds, causing changes in their structure and function; produced as a result of coral bleaching.

Broadcast Spawning

Consists of both male and female coral expelling massive amounts of gametes (eggs and sperm) into the water column during synchronized events.

*Zooxanthellae*

Coral provides this algae with a protected environment and the compounds necessary for *photosynthesis.* These include carbon dioxide, produced by coral respiration, and inorganic nutrients such as nitrates, and phosphates, which are metabolic waste products of the coral. In return, the algae produce oxygen and help the coral to remove wastes.

________ fishing in the Indonesian and Philippine coral reefs of South Asia stuns and injures valuable fish. Although 85% of the world's aquarium fish are captured with this destructive method, they suffer a 90% mortality rate usually several weeks after they have been poisoned by ________.

Cyanide

What do corals eat?

During feeding, a coral polyp will extend its tentacles out from its body and wave them in the water current where they encounter zooplankton, bacterioplankton, or other food particles. A coral's prey is typically microscopic zooplankton.

_________ in developing countries depend on reef fish for income to provide for their families; however, illegal fishing practices and overfishing is depleting fish stocks in these areas, rapidly threatening the livelihood of these local populations.

Fishermen

How fast do corals grow?

Hard Coral: The rate at which a stony coral colony lays down calcium carbonate depends on the species, but some of the branching species can increase in height or length by as much as 10 cm a year (about the same rate at which human hair grows). Other corals, like the dome and plate species, are more bulky and may only grow 0.3 to 2 cm per year. Soft Coral: A soft coral colony has the growth potential of two to four centimeters per year.

Budding

In this form of asexual reproduction, new polyps bud off from parent polyps to expand or begin new colonies. This occurs when the parent polyp reaches a certain size and divides. This process continues throughout the animal's life and produces polyps that are genetically identical to the parent polyp.

Soft Corals

Including sea fans; do not produce a rigid calcium carbonate skeleton and do not form reefs, though they may be present in a reef ecosystem.

With approximately 85,470 sq km of tropical coral reefs, _________ hosts about 33% of the total coral in the world and 25% of all fish species. However, in 2000 it was reported that over 70% of the coral reefs are in bad to fair condition due to fishing practices, out of control tourism, and long periods of bleaching.

Indonesia

Coral colony

Many coral polyps of the same species interconnected through a common skeleton.

Another factor that seems to affect the diversity of reef-building corals is the ______ in which they are located. At least 500 reef-building species are known to exist in the waters of the Indo-Pacific region. In comparison, the Atlantic ______ contains approximately 62 known species.

Ocean

Coral reefs in the ___________ were found to be 77% less productive from 1966-1986, while the national population doubled in size. If the destruction continues, we will lose about 70% of the world's reefs within 25-40 years.

Philippines

Hard Corals

Produce a rigid skeleton made of calcium carbonate (CaCO3) in crystal form called aragonite, with reef-building capabilities.

_______ coral reefs have optimal growth rates in warm water ranging from 70-85°F (21-29°C).

Shallow

Brooding

Similar to broadcast spawning, except only the male gametes are released into the water column. Coral sperm is negatively buoyant once released and hopefully will be carried by ocean currents to female coral where they will fertilize the egg cells of the female coral.

Coral Triangle

The heart of the world's coral reef biodiversity, located in Southeast Asia.

*Symbiont*

The smaller participant in a symbiotic relationship, living in or on the host.

Fragmentation

This method also allows a portion of an entire colony to establish a new colony. If a portion of a larger colony is broken off from the main colony during a storm or boat grounding, the separated individuals can start new coral colonies that are genetically identical to the parent colony. However, the success of the fragments in establishing a new colony is dependent upon whether they are exposed to favorable growth conditions. For instance, fragments exposed to strong wave action will find it difficult to settle on a substrate for continued growth.

Organisms responsible for building tropical (biotic) coral reefs can only grow at 20-28°C, so although coral reefs live in all oceans, most are found between the ______ of Capricorn and the ______ of Cancer.

Tropic

Corals can exist as individual polyps, or in ________ and communities that contain hundreds to hundreds of thousands of polyps.

colonies

Sustainable coral reef fisheries in Southeast Asia alone are valued at $2.4 billion per year. These numbers do not take into account the value of deep-sea corals, which are themselves home for many _____________ valuable species and thus additional fisheries value.

commercially

Fishermen hit the coral reefs with crowbars to shake out stunned fish and they also even fish with dynamite, which often destroys every living thing on the reef. Many reefs once teeming with life are now wastelands that even the most vigorous ____________ efforts can't begin to restore.

conservation

Globally, one estimate shows fisheries benefits account for $5.7 billion of the total $29.8 billion global net benefit provided by _____ ______.

coral reefs

The number of species of corals on a reef declines rapidly in _______ water. High levels of suspended sediments can smother coral colonies, clogging their mouths which can impair feeding. Suspended sediments can also serve to decrease the depth to which light can penetrate. In colder regions, murkier waters, or at depths below 70 m, corals may still exist on hard substrates, but their capacity to secrete limestone is greatly reduced.

deeper

Many species found in coral ecosystems produce chemical compounds for ________ or attack, particularly the slow-moving or stationary species like nudibranchs and sponges.

defense

Local __________ receive billions of dollars from visitors to reef regions through diving tours, recreational fishing trips, hotels, restaurants, and other businesses based near reef ecosystems. One estimate places the total global value of coral-reef based recreation and tourism at $9.6 billion of the total global net benefit of coral reefs.

economies

Many species find ____ in and around coral reefs.

food

All coral polyps share two basic structural features with other members of their phylum. The first is a ______________ cavity that opens at only one end. At the opening to this cavity, commonly called the mouth, food is consumed and some waste products are expelled.

gastrovascular

Approximately ____ of all federally managed fisheries in the United States depend on coral reefs and related habitats for a portion of their life cycles.

half

More than 500 million people worldwide depend on coral reefs for food, _____, and protection

jobs

*Coral reefs begin to form when free-swimming coral ______ (planulae) attach to the submerged edges of islands or continents. As the corals grow and expand, reefs take on one of three major characteristic structures—fringing, barrier or atoll.*

larvae

Coral can be grown using a process known as mineral accretion where _________ is stimulated to collect on metal by a safe low voltage current, providing a nice place for baby coral to latch on and grow. The voltage itself can be provided using solar panels or energy from wave action.

limestone

Other factors influencing coral distribution are availability of hard-bottom substrate, the availability of food such as plankton, and the presence of species that help control __________, like urchins and herbivorous fish.

macroalgae

Human activity is one of the greatest threats to coral reefs, particularly the destruction of ________ forests that naturally absorb sediment and nutrients that can suffocate coral reefs with silt and algae blooms.

mangrove

The mutual exchange of algal photosynthates and cnidarian ____________ is the key to the prodigious biological productivity and limestone-secreting capacity of reef building corals.

metabolites

Using its tentacles that extend outside it body, the coral uses its ___________, or stinging cells, to stun and kill its prey before passing it to its mouth. Once the food has been digested, the waste is expelled from the same opening.

nematocysts

Unlike stony corals, most soft corals thrive in _________-____ waters with less light intensity. Almost all utilize zooxanthella as a major energy source. However, most will readily eat any free floating food, such as brine shrimp, out of the water column.

nutrient-rich

As members of the phylum Cnidaria, corals have only a limited degree of _____ development. Each polyp consists of three basic tissue layers: an outer epidermis, an inner layer of cells lining the gastrovascular cavity which acts as an internal space for digestion, and a layer called the mesoglea in between.

organ

Coral reefs provide shelter for a wide variety of marine life, human recreation, valuable resources of ____________ for potential medicines, sands for beaches, and serve as buffers for shorelines.

organisms

Most importantly, zooxanthellae supply the coral with organic products of ________________. These compounds, including glucose, glycerol, and amino acids, are utilized by the coral as building blocks in the manufacture of proteins, fats, and carbohydrates, as well as the synthesis of calcium carbonate (CaCO3).

photosynthesis

The _______ containing organisms are lost as temperature or stress level due to increased light reaches intolerable levels. As temperatures return to normal, some reefs can recover within several weeks or months. However, equilibrium may not be restored due to global warming and the bleaching effect exposes corals to white and black band diseases.

pigment

Coral reefs can be found at depths exceeding 91 m (300 ft), but ____-________ corals generally grow best at depths shallower than 70 m (230 ft). The most prolific reefs occupy depths of 18-27 m (60-90 ft), though many of these shallow reefs have been degraded

reef-building

There are two groups of Scleractinia: Colonial corals found in clear, shallow tropical waters; they are the world's primary reef-builders, and solitary corals which are found in all regions of the oceans and do not build _____.

reefs

Coral bleaching occurs when the single-celled algae vital for coral reef survival and known as symbiotic zooxanthellae are ________ from the coral, soft corals, some sponges and even Tridacna clams.

rejected

Corals also need ____ water to survive, so they also grow poorly near river openings with fresh water runoff.

salt

Most corals require very _____ (saline) water ranging from 32 to 42 parts per thousand. The water must also be clear to permit high light penetration. The corals' requirement for high light also explains why most reef-building species are restricted to the euphotic (light penetration) zone, approximately 70 m.

salty

Much of the framework of coral reefs is formed by ______________.

scleractinians

Alcyonacea corals contain minute, spiny skeletal elements called _________. Aside from their scientific utility in species identification, _________ give these corals some degree of support and give their flesh a spiky, grainy texture that deters predators.

sclerites

A *gorgonian*, also known as sea whips or ___ ____ (soft corals), are an order of sessile colonial cnidarian found throughout the oceans of the world, especially in the tropics and subtropics.

sea fans

Gorgonians are similar to ___ _____, another soft coral. Individual tiny polyps form a colonies that are normally erect, flattened, branching, and reminiscent of a fan.

sea pens

More than 1/4 of all ocean species depend on coral reefs for food and ________.

shelter

In general, massive corals tend to grow ______, increasing in size from 0.5 cm to 2 cm per year. However, under favorable conditions (high light exposure, consistent temperature, moderate wave action), some species can grow as much as 4.5 cm per year.

slowly

The *Alcyonacea*, or the ____ ______, are an order of corals which do not produce calcium carbonate skeletons and so are neither reef-building corals nor do they lay new foundations for future corals.

soft corals

While the growth patterns of stony coral colonies are primarily ________-specific, a colony's geographic location, environmental factors (e.g., wave action, temperature, light exposure), and the density of surrounding corals may affect and/or alter the shape of the colony as it grows.

species

In addition to affecting the shape of a colony's growth, environmental factors influence the rates at which various species of corals grow. One of the most significant factors is _________.

sunlight

The Pulley Ridge reef off the southern coast of Florida absorbs more light by increasing _______ ____ and growing flat rather than the usual vertical growth seen in shallower coral reefs.

surface area

Reef-building corals are restricted in their geographic distribution. This is because the algal-cnidarian _________ machinery needs a narrow and consistent band of environmental conditions to produce the copious quantities of limestone necessary for reef formation.

symbiotic

The formation of highly consolidated reefs only occur where the ___________ does not fall below 18°C for extended periods of time. This specific ___________ restriction -18°C- does not, however, apply to the corals themselves. In Japan, where this has been studied in detail, approximately half of all coral species occur where the sea ___________ regularly falls to 14°C an approximately 25% occur where it falls to 11°C.

temperature

A second feature all corals possess is a circle of __________, extensions of the body wall that surround the mouth. _________ help the coral to capture and ingest plankton for food, clear away debris from the mouth, and act as the animal's primary means of defense

tentacles

Because nematocytes are capable of delivering powerful, often lethal ______, they are essential to capturing prey, and facilitate coralline agonistic interaction.

toxins

In contrast to the massive species, branching colonies tend to grow much faster. Under favorable conditions, these colonies can grow __________ by as much as 10 cm per year. This fast growth rate is not as advantageous as it may seem, however. Mechanical constraints limit the maximum size that branching corals can achieve.

vertically

The ridges in coral reefs can reduce ____ energy by up to 95%, providing crucial protection against threats like tsunamis.

wave

The symbiotic zooxanthellae also confers its color to the polyp. If the zooxanthellae are expelled, the colony takes on a stark _____ appearance, which is commonly described as "coral bleaching."

white

Most reef-building corals have a mutually beneficial relationship with a microscopic unicellular algae called _____________ that lives within the cells of the coral's gastrodermis. As much as 90% of the organic material the algae manufacture *photosynthetically* is transferred to the host coral tissue

zooxanthellae

The fish that grow and live on coral reefs are a significant food source for over a billion people worldwide—many of whom live far from the reefs that feed them.

a billion

*Tropical coral reefs* are biotic reefs formed in tropical waters by live organisms such as calcareous _____ (including red _____) and corals. In contrast, abiotic reefs are formed by the deposit of sand and other materials in shallow water.

algae

*Scleractinia*, also called stony corals, are exclusively marine animals; they are very similar to sea _________ but generate a hard skeleton.

anemones

Corals are unique in that they are capable of reproducing both sexually and _________. Sexual reproduction is the more common method and can be performed in two ways: broadcast spawning or brooding.

asexually

All three reef types—fringing, barrier and atoll—share similarities in their _____________ profiles. Bottom topography, depth, wave and current strength, light, temperature, and suspended sediments all act to create characteristic horizontal and vertical zones of corals, algae and other species.

biogeographic

Most corals _______ and consume live prey ranging from microscopic zooplankton to small fish, depending on coral size.

capture