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CORAL REEFS

Unit 1 Lesson 3: Corals, Forams, and Reef Health

Lesson Objectives: Students will understand the plight of coral reefs, and the diseases and factors responsible for their decline.

Vocabulary: coral bleaching, zooxanthellae, , , coralline, foraminifera, symbiotic Source and co-author: Dr. Pamela Hallock Muller, University of South Florida

Corals and Forams

Coral reefs are in trouble are subject to bleaching and worldwide. According to a may die if the environment is 1998 study by the World not favorable. Institute, 60% of the radiation, carbon dioxide and world’s coral reefs are other factors affect them. threatened. Threats to coral reefs can be classified as local, regional and global.

Forams are small organisms that live on the coral reef. They

Local Threats

Local threats include runoff of world, with the exception of sediments and nutrients from some protected areas on , and ’s Great Barrier Reef, destructive fishing, dredging that are not overfished. and careless boat operation, including grounding of large ships on coral reefs. Many “local” threats are so widespread, they are actually regional or even global in extent. For example, the World Resources Institute report concluded that there are virtually no reefs in the entire Pipe Coral 23 PROJECT OCEANOGRAPHY SPRING 2000

CORAL REEFS

Regional Threats

Regional threats include new been unlimited growth of algae diseases that sweep through on coral reefs. The spiny sea populations of organisms living urchin population fed on the on the reefs. For example, in algae populations found on the 1983, an unknown disease, coral reefs. For example, in the possibly a virus, is believed to early 1980’s, coral covered have come through the more than 60% of the reefs in Panama Canal from the Pacific Jamaica. Now, coral covers Ocean. This disease killed less than 10% of the reef. most of the spiny sea urchin Algae are taking over the reefs everywhere.

Another disease swept through the coral reefs of the Caribbean and western Atlantic in the 1980’s – white-band disease. This disease, which looks like a white band of death as it attacks a coral colony, wiped out most of the branching coral (Acropora palmata and Acropora cervicornis) Sponge Coral. throughout the Caribbean. White Band disease is one of population, first in Panama then the reasons why Jamaican throughout the Caribbean and reefs lost most of their coral. to the Western Atlantic reefs of the Florida Keys and Bahamas. Another coral disease is Black More than 99% of the spiny sea Band disease, which mostly urchins were killed. The virus attacks head-forming corals like seems to still be present, star coral and brain coral. This because spiny sea urchins are disease was first reported in the now uncommon on Caribbean 1970’s and now is extremely reefs. common, especially in areas where corals are weakened by The consequence of the die-off other stresses such as coral of the spiny sea urchin has

24 PROJECT OCEANOGRAPHY SPRING 2000 CORAL REEFS bleaching or excess nutrients from or . but they have been given A variety of other coral descriptive names like White diseases have more recently Pox, White Plague, and Rapid been discovered. Scientists Wasting disease. don’t know much about them,

Global Threats

There are truly global problems carbon dioxide in the that contribute to the atmosphere caused by burning prevalence of coral diseases. fossil fuels like coal, oil and The two global problems are natural gas. These fuels are global warming and carbon compounds that, when stratospheric ozone burned, combine with depletion. Global warming is from the atmosphere to form the natural consequence of carbon dioxide. increasing concentrations of

Global Warming

Carbon dioxide is a levels of greenhouse gases “greenhouse” gas in the drop, another age may be atmosphere, and therefore may the result. contribute to global warming. Carbon dioxide in the During years known as El Nino atmosphere acts like a blanket years, tropical oceans around that holds in heat and . many coral reefs become This process is called global warmer than usual. The years warming. Sources of carbon 1983, 1987, 1991, and 1997 dioxide in the ’s were warmer than normal. atmosphere include Many coral reefs suffered decomposition of organic bleaching. Coral bleaching is matter, burning of fossil fuels when the corals expel their and by-products of human and symbiotic algae, known as animal respiration. The amount zooxanthellae, in an attempt to of carbon dioxide needs to be save themselves. “just right”. If too much heat is trapped, the ocean can Zooxanthellae are symbiotic become warmer than normal. If dinoflagellates that live within

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CORAL REEFS the corals and give them their after expelling their carbohydrate and protein zooxanthellae. supply. Usually corals die

Ozone Depletion

The second global problem is decade ago, the chemicals stratospheric ozone depletion. already introduced into the It is caused by certain atmosphere continue to cause chemicals called ozone depletion. Besides the , which Earth being extra warm during were used in (e.g., in the 1980’s and 1990’s, more spray cans) for several biologically damaging UV decades, and in radiation has been reaching the and refrigeration systems (e.g., Earth. UV radiation by itself ). High in can cause coral bleaching in the Earth’s some cases, but corals actually atmosphere is a produce their own sunscreens layer called the to protect themselves from UV , damage. Unfortunately, when where a special the ocean temperature goes up, form of oxygen the coral is stressed and unable called ozone is to produce its sunscreens at found. Molecules the normal rate, making the of ozone selectively absorb the corals even more vulnerable to part of that is “”. especially biologically damaging –ultraviolet Together, high temperatures radiation (UV). UV radiation and high UV can be especially can cause mutations, skin damaging. High UV levels also cancer and ‘sunburn’ in many damage the immune systems organisms, including corals. If of organisms, which may be there were no ozone in the why there are so many stratosphere, on Earth incidences of new or previously would be much reduced or unknown diseases. changed. New diseases have also been Although an international treaty found in a variety of other reef slowed the use of ozone- and animals, besides destroying chemicals nearly a corals. Sea fans are

26 PROJECT OCEANOGRAPHY SPRING 2000 CORAL REEFS susceptible to a fungus that have also decimated coralline comes from land, probably algae, seagrasses, sea urchins either from river runoff or and sponges in some reef atmospheric dust. New or areas. previously unknown diseases

Other Reef Plants and Animals in Peril

Another group of organisms bleaching suggest that that are susceptible to both biologically damaging UV bleaching and new diseases radiation may be the cause, are reef-dwelling foraminifera, since these forams don’t seem single-celled animals that form to be bothered by slightly a calcium carbonate outer elevated temperatures. skeleton. The most common foram on reefs worldwide, The forams become Amphistegina spp., have been progressively weakened and stressed worldwide throughout unable to fend off attack by the 1990’s. Seasonal, depth diseases, predators, and and latitudinal patterns of parasites, and there is an increase in incidents of birth defects in the population. Bleaching in forams results when their symbiotic algae stop working (photosynthesizing). This prompts the forams to digest their symbionts. Without them, the forams ultimately starve.

Elkhorn Coral

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CORAL REEFS Activity 3-1: Environment in Danger

Background: To make this a successful classroom exercise, the teacher should assign the exercise a week ahead of time so the students have something to report. The classroom part allows students to identify where their news report is from using a world map. Use pushpins to do so.

Purpose: To make students aware that problems occur in natural populations and environmental factors are sometimes the source of the problems. To show students there is a need for more research on many .

Exercise: Watch the news or programs on TV, listen to the news on the radio, look in the newspaper, or look in magazines at home or in the library for one story on disease, unusual affliction, or unexplained decline in or animal populations other than humans. Examples could include, such things as beak deformities in chickadees in Alaska, the unexplained decline of bison in Buffalo National Park in Canada, bleaching or disease in coral reefs of Florida, or deformed frogs in Minnesota. Give the source of the story (which news or TV program, newspaper or magazine, date, the kind of plant or animal, and where in the world the report is from).

Ask students to summarize the known scientific explanation for each event. Then ask what are the unknown aspects of the event that may require additional research.

Variation: Instead of having the students present their materials individually, have them gather together in groups that are “geographically” near each finding. Have the students in each group discuss if there was a ‘local’ event that might have resulted in the findings that they have found in the media. Have one spokesperson for the group working together.

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CORAL REEFS Student Information Sheet 3: Corals, Forams, and Reef Health.

Corals and foraminifera survive Global warming causes together in reef communities. temperature to rise, and corals This is a symbiotic relationship. expel their symbiotic algae, A symbiotic relationship is one called zooxanthellae. in which both organisms benefit Zooxanthellae are from living together. dinoflagellates that live within the corals and give them their Coral reefs are in trouble. rich colors. They also produce There are local, regional and complex carbohydrates and global threats that influence the proteins that feed the growing overall health of reef corals. Usually corals die after populations. Local threats expelling their zooxanthellae. include sediment and nutrient runoff, dredging, and careless Ozone depletion is a result of boat operation. Regional chemicals called threats include diseases to chlorofluorocarbons being organisms that live on reefs, released into the atmosphere and diseases to corals and destroying the protective themselves. A few coral of the atmosphere. diseases are white-band This allows more ultraviolet disease, coral bleaching and (UV) sunrays into the earth’s White Pox. Globally, there are atmosphere, and ultimately two outstanding threats to coral the coral reefs and reefs: global warming and organisms. Combined with ozone depletion. increased temperatures, coral reefs can become very stressed.

Things you can do to help 1. Don’t use aerosols that contain chlorofluorocarbons (CFC’s). 2. Don’t pollute. 3. Volunteer in coral reef monitoring programs. If you do not live near the coast, get involved in local programs to save the river or bay. Remember, all watersheds affect the oceans and eventually the coral reefs.

PROJECT OCEANOGRAPHY 29 SPRING 2000