Presentation on theme: "The Undersea Environment of Coral Reefs"— Presentation transcript:
1 The Undersea Environment of Coral Reefs Coral reefs are the most biologically diverse marine ecosystems on earth, rivaled only bythe tropical rainforests. They provide homes and nurseries for almost a millionfish and other species. Incredibly, coral reefs occupy only one quarter of one percentof the earth's marine environment, yet they are home to more than a quarter of allknown fish species. Let’s take a look at these fascinating communities underthe sea that have been in existence for almost 200 million years.
2 Presentation Overview Biological characteristics of reefsFunctions of reefsPotential Diseases and HazardsThese 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 complexecosystems that rely on the various occupants and the surrounding environmentto 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 differentpeople. 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, butmost all corals have common structural characteristics. Corals have been inexistence for nearly 200 million years but reached their current level ofdiversity 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 staystationary 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 coralpolyps.
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. Althoughmost corals contain hundreds or thousands of polyps, some containonly one. The polyp is a hollow, cylindrical animal with a mouth thatis surrounded by tentacles armed with stinging cells for capturingfood. Underneath these coral polyps is the dead coral skeletoncomposed of calcium carbonate. Each coral polyp excretes a calcareousexo-skeleton that lives in a symbiotic relationship with zooxanthellae,host algae located in the tissue of the polyp, that gives the coral itsgreen, blue, purple or brown color.
7 There are two different types of corals Hard Corals known as scleractiniansSoft Corals know as gorgoniansThere are two main types of corals; hard corals composed of stonycalcium carbonate, and soft corals made up of a protien/calciumcarbonate 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 coralssuch as sea fans, sea whips and sea rods, sway with the currents andlack an exoskeleton.Soft coralHard coral
8 Corals are located in three primary locations Western North AtlanticIndo-PacificCoral 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 20N and 20 S of the equator. The Indo-Pacific region stretches from Southeast Asia through Polynesia andAustralia, eastward across the Indian Ocean to Africa. This is the largestand richest assemblage of reefs in terms of coral and fish species present.The Western North Atlantic region stretches from Florida to Brazil, andIncludes Bermuda, the Bahamas, the Caribbean, Belize and the Gulf ofMexico. The Red Sea is the smallest of the three regions, located betweenAfrica and Saudi Arabia. It is considered a separate region because ofthe high number of coral reefs found only in this area.Red SeaIndo-Pacific
9 They survive in unique conditions that require... Adequate sunlightWater temperatures between CelsiusShallow water depthsLow siltationIn order for corals to live, they require healthy living conditions includingadequate sunlight, clean water with low levels of siltation, relatively shallowdepths and stable water temperatures. Drastic changes in any of theseConditions for significant periods of time can contribute to the death of corals.
10 Corals obtain food via….. Zooxanthellae photosynthesisPredation upon zooplankton and phytoplanktonAbsorption of dissolved organic materialCorals 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 andcarbon dioxide into oxygen and carbohydrates (sugar). The zooxanthellae take in carbon dioxide throughphotosynthesis, and then give off oxygen as a by-product that is used by the host polyp. Both oxygen andcarbohydrates are essential elements in the energy production of corals. Algae “leak” these elements into the polyp’stissue 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 protectionfor the algae.Corals also obtain their food through more active means. They prey on different types of algae called zooplankton andphytoplankton. 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 marineOrganisms, is much more active at night.The corals “come alive” at night, eating by extending tentacles to capture their prey. The coral nematocystssting and immobilize their prey so that the tentacles can withdraw and bring the food down into digestive cavityof the polyp. Polyps can also release mucus in the form of thin sheets over the whole colony or in strands or sheets intothe water. Plankton, bacteria and organic debris get stuck to mucus and, the cilia on the tentacles help to bringthe mucus back into the digestive cavity.The third way corals obtain food is through the absorption of dissolved organic molecules (DOM), particulate organicmaterial (POM), and from sharing of food. For example, DOM such as glucose and certain amino acids can be absorbedfrom water through the polyp's body wall by means of tiny fuzzy projections called "microvilli.” These organic moleculesenter the water column from decomposing animals and plants. Particulate organic material, such as bacteria, decomposingorganic matter and fish fecal material (detritus), are directly ingested by the polyp. Food can also be shared in some speciesof colonial corals whose digestive cavities are interconnected Thus, food obtained by one polyp can be transported throughoutit's own body or to other polyps.
11 Reefs play important roles in the coastal and ocean environment Habitats for many marine speciesBreeding grounds for lobster, shrimp, and various fishFood and shelterBarriers protecting the coasts from stormsSources of sand for beachesRecreational areas for snorkelers, divers and fishermenCoral reef ecosystems have important ecological and economic functions for ourcoastal regions. It is evident that the reef is a significant link to the vitality andsustainability of other environments.Reefs form a natural and self-repairing barrier that protects the coasts by absorbingviolent wave impacts of ocean storms and hurricanes. Corals and calcareous algae aremajor sources of sand. Fish graze on coral and then excrete organic material thatcontributes to the bottom sediment. Reefs also provide habitat, shelter, food andbreeding 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 theireconomic stability. Take the Florida Keys for example. This region depends on nearly2 million tourists visiting the Keys and their coral reefs annually. Tourists come tosnorkel, fish, scuba dive and see the sites. Commercial and recreational fishing is anotherindustry that relies on the health of the reefs. The coral reefs support the fish that attractlocal 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 plantsAnother 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 echinodermsall help to clean the waters surrounding the reef.
13 Many natural and human-induced factors can harm reefs Bioerosion by fishes and other marine organismsDiseasesStormsOverfishingCoastal developmentPollutionSeveral frequently observed conditions have been identified as harmfulto 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'ssusceptibility 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 reefis bioerosion. For example, the sea urchin Diadema antillarum functionsas both a grazer on algae that can smother coral, and as a bioeroder ofcorals as it feeds on them. Other bioeroders include crown of thorns,parrot fish, and boring worms. All of these marine organisms manageto weaken the coral structure the coral skeleton, making it moresusceptible 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 temperaturesexceed the coral’s maximum tolerable temperature range. Coralstypically grow in warm tropical waters between degrees Fahrenheit.Coral bleaching occurs when sea temperatures rise or when other stresses occurThat 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 thecoral and leaving the white coral skeleton behind. When blackband diseasekills part of a colony, the skeleton is then available to be colonized by othercoral species recruits. In fact, some scientists suggest that blackband diseasemay actually help maintain coral diversity because it is most prevalent in coralspecies that form large colonies. Studies have shown, however, that there wereno coral recruits among corals infected by blackband disease after 25 months.It is believed that whiteband disease is caused by a bacterial pathogen notyet known. It affects corals much as blackband disease , leaving behind a white,lifeless coral skeleton. Unlike blackband disease , scientists do not see whitebanddisease as being beneficial to reefs. Scientists have shown that whiteband diseasedestroys the reef structure because algae, invertebrates, gastropods and boringsponges colonize the dead coral skeleton. This colonization works to weaken the coralskeleton,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 alsofor the economic benefits - such as tourism, fishing and recreational resources - theyprovide to tropical areas around the world. If we don't get involved in protecting thesefragile ecosystems, the first generation to discover scuba may be the last to enjoycoral reefs.