Coral reef ecosystems are intricate and diverse collections of species that interact with each other and the physical environment.

A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups.
Seven Surprising Facts about Coral
1: Corals Are Animals. ...
2: Corals Can Be Fluorescent. ...
3: Corals Eat Plankton/Small Fish. ...
4: There Are Hundreds of Coral Species of All Colors, Shapes and Sizes. ...
5: Corals Can Move. ...
6: Corals Support 25 Percent of Ocean Life. ...
7: Climate Change Is the Biggest Threat to Corals.
Benefits of coral reef ecosystems

Coral reefs protect coastlines from storms and erosion, provide jobs for local communities, and offer opportunities for recreation. They are also are a source of food and new medicines. Over half a billion people depend on reefs for food, income, and protection.

1. CORAL REEF ECOSYSTEM PRESENTED BY, BP241502 KESAVARDHINI K 1 ST M.SC MICROBIOLOGY SHC-TIRUPATTUR

2. INTRODUCTION Coral reefs are the colonies of tiny living creatures that are found in oceans. They are the underwater structures that are formed of coral polyps that are held together by calcium carbonate. Coral reefs are also regarded as the tropical rainforest of the sea and occupy just 0.1% of the ocean’s surface but are home to 25% of marine species. They are usually found in shallow areas at a depth less than 150 feet. However, some coral reefs extend even deeper, up to about 450 feet.

3. WHAT IS CORAL REEF ? Coral reef are one of the most biologically diverse ecosystem on earth, revealed only by tropical rain forests. They are made up only of hard and soft corals, but also sponges, crustaceans, mollusks , fish, sea turtles, sharks, dolphins and much more.

4. Animals commonly found in and around coral reef include : Soft corals, hard corals, fire corals, anemones . Hundreds of different species of sponges . Conch, clams, sea slugs, cowries . Fireworms , Christmas tree worms, fan worms . Crabs, lobster, shrimp . Urchins, starfish, basket stars, sea cucumbers . Thousands of different species of fish . Sea turtles and sea snakes.

5. ENVIRONMENTAL CONDITIONS NECESSARY FOR A HEALTHY CORAL REEF : Abundant sunlight Reef-building corals cannot survive without sunlight, since zooxanthellae , their symbiotic algae, require sunlight for photosynthesis. The majority of zooxanthellae reef-building corals do not grow below 45m (150ft). Warm temperature Corals can only live within a narrow temperature range from around 16°C - 29°C (62°F - 85°F). This explains why corals thrive in the warmer waters of the tropics.

6. Low Nutrients Level Corals are adapted to live in ocean water, which contains very low levels of nutrients. Nutrients, which are needed by all living organisms, are found in food and dissolved in water. Clear Sediment Free water Corals prefer clear water with low levels of sediments (small particles of earth, rock and sand). Sediments can bury corals, blocking out needed sunlight and killing them. Salty Water Corals are marine animals adapted to live in seawater with a salinity of around 35 parts per thousand. In areas that are too salty, or not salty enough, corals cannot survive.

7. Types of coral reef Fringing reefs It lie around islands and continents, and are separated from the shore by narrow, shallow lagoons. They usually parallel the coastline and at their shallowest point can reach the water’s surface. Barrier reefs It also grow parallel to the coastline, but are separated by deep, wide lagoons. At their shallowest point, they can reach the water’s surface, forming a “barrier” to navigation. Atolls It is a rings of coral that create protected lagoons and are often located in the middle of the sea. Atolls usually form when islands surrounded by fringing reefs sink into the sea or the sea level rises around them (they are often the tops of underwater volcanoes).

8. Bank or platform reefs It is a open ocean reefs that are simple structures with many different origins, yet no clear attachment to the coastline. Most of these reefs have an area that is exposed to wind and a sheltered side where lagoons and small reef patches can be found. Larger and slightly submerged reefs of this type are also called shoals. Patch reefs This is small areas of reef that occur in shallow waters and lagoons.

9. Beneficial of Microbes in corals: Antimicrobial compounds produced by corals probably function in controlling the associated microbiota . For example, the antimicrobial peptide damicornin was most active against a fungus and some (but not all) Gram-positive bacteria, and had no effect on the four tested vibrios . Organic extracts of the coral  Siderastrea siderea  showed selective antimicrobial activity against two of four strains of Gram-positive bacteria isolated from coral surfaces. Antibiotic activity against nine strains of marine bacteria, including known coral pathogens and bacteria related to those from coral surfaces, was found in the crude aqueous extracts of three common Hawaiian corals,  Montipora captitata ,  Porites lobata  and  Pocillopora meandrina  .

10. Beneficial of microbes in corals : Extracts of M. capitata  displayed the most antimicrobial activity, which might be related to the presence of montiporic acids A and B, which are cytotoxic and antimicrobial polyacetylene carboxylic acids found in  Montipora  spp. Otherwise, the chemical structures of antimicrobial compounds in corals are not known. Exposure of corals to pathogens also induces production of enzymes with predicted defence functions: phenoloxidase , peroxidases and chitinases , as well as melanin, which is the end product of phenoloxidase . Genome-mining projects identified a number of homologues of the genes with predicted functions in chemical defence , products of which are probably involved in the interactions with microbes.

11. GROWTH FORMS OF CORALS Scientists currently estimate that there are 794 species of reef-building corals throughout the world . Identifying coral species can be surprisingly difficult even for experts, and in some cases impossible without taking a sample to a laboratory for testing. A simple way to categorize corals is based on theirdifferent shapes. Corals can be classified into ten general growth forms:

12. Braches coral Elkhorn coral Digitate coral

13. Encrusting coral Table coral Foliose coral

14. Massive coral Submassive coral Flower/cup coral

15. Factors affecting coral reef Extreme climate conditions Overfishing Coastal development Pollution Sedimentation

16. Applications of coral reef : Coral Reefs play an important role in the following ways. They protect coastlines from the damaging effects of wave action and tropical storms. They provide habitats and shelter for many marine organisms. They are the source of nitrogen and other essential nutrients for marine food chains. They assist in carbon and nitrogen-fixing. They help with nutrient recycling.