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Coral ecology ppt

  2. Coral reefs are wave- resistant structures notable for their great species richness, ecological complexity and remarkable beauty They are unique in being formed entirely by the biological activity
  3.  Often called rain forests of the sea, due to their richest biodiversity. They occupy less than 0.1% of the world’s ocean surface, but provide home for 25% of marine species
  4. ORIGIN OF REEFS  Subsidence theory – (Darwin-Dana)  Solution theory – (Semper-Murray)  Submerged bank theory  Glacial epoch theory - Daly
  6. It involves understanding biotic and abiotic factors influencing the distribution and abundance of living things of coral community
  7. DISTRIBUTION  Corals occur throughout the oceans, but colonial reef-building (hermatypic) corals are confined to the tropics and sub-tropics where calcification rates are greatly enhanced  Reefs grow best in warm, marine, shallow, clear, sunny and agitated waters
  8. LIMITING FACTORS  Latitude  Temperature  Light  Salinity  Turbidity & Sedimentation  Wave action  Aerial exposure
  9.  Coral reefs, just like any other ecosystem on our planet, rely on a variety of biotic and abiotic factors to keep them healthy and functional.  Without stable temperature, pH, light intensity, water flow, salinity, and chemical composition of sea water, coral reefs could not exist, but without a stable trophic cascade, coral reefs could not survive.
  10. Biotic Factors • Competitors • Disease • Predators • Food availability • Habitat availability • Symbiotic relationships Abiotic Factors • pH • Temperature • Weather conditions • Water availability • Chemical composition of environment • nitrates, phosphates, ammonia, O2, pollution
  11. TYPES OF CORALS  Hard corals, also known as scleractinian and stony coral, produce a rigid skeleton made of calcium carbonate (CaCO3) in crystal form called aragonite. Anatomic structures such as septa, tentacles, and mesenteries are found in sets of six, so hard corals are also often termed hexa corals.
  12.  One of the characteristic feature of hermatypic corals is the presence of unicellular algae (Symbiodinium microadriaticum) with in the gastrodermal tissue.  By their influence on coral growth and calcification rates these symbiotic zooxanthellae play a fundamental role in the reef-building process
  13. HARD CORALS Brain coral Stag horn coral Foliose coral
  15. SOFT CORALS Soft coral, also known as Alcyonacea and ahermatypic coral, do not produce a rigid calcium carbonate skeleton and do not form reefs, though they may be present in a reef ecosystem. Anatomic structures such as tentacles and mesenteries are found in sets of eight, so soft corals are often called octocorals.
  16. DIVERSITY OF CORAL REEFS  Reefs are home to a large variety of organisms, including fish, seabirds, sponges, cnidarians (which includes some types of corals and jellyfish), worms, crustaceans (including shrimp, cleaner shrimp, spinylobsters and crabs), mollusks (including cephalopods), echinoderms (including starfish, sea urchins and sea cucumbers), sea squirts, sea turtles and sea snakes.  Aside from humans, mammals are rare on coral reefs, with visiting cetaceans such as dolphins being the main exception.  A few of these varied species fed directly on corals, while others graze on algae on the reef.  Reef biomass is positively related to species diversity.
  18. NUTRITION  Corals have developed several unique ways of feeding; they receive nutrients from symbiotic algae, capture particles such as plankton, and take up dissolved substances from the water.
  19.  In order to fully appreciate the importance of a balanced ecosystem such as a coral reef, we must first understand its trophic structure; the organisms that make up each trophic level, and the functions of each level in the maintenance of a healthy reef.
  20. TROPHIC STRUCTURE  Coral reefs are complex ecosystems that require a balanced trophic structure to function properly and efficiently.  Imbalances can occur in this intricate trophic cascade from the top down or the bottom up. For an example of bottom-up effects, nutrient-rich agricultural run-off can cause a massive increase in primary productivity (e.g. algal blooms), the effects of which often cannot be buffered by consumers fast enough to prevent a coral reef ecosystem from collapsing.
  21.  There are three categories of organisms in every ecosystem: producers, consumers, and decomposers.  Primary consumers are herbivorous, whereas secondary consumers prey on herbivores and tertiary consumers eat other carnivores.  Decomposers are responsible for breaking down dead and decaying plant and animal matter into components that are once again usable for growth by producers.  None of these three categories of organisms can exist without the others in order to complete the cycle of production, consumption, and decomposition.
  22. PRIMARY PRODUCERS OF CORAL REEF ECOSYSTEM  zooxanthellae in corals  filamentous algal scum (turf algae)  coralline (calcareous) algae  non-coralline seaweed  filamentous algae growing through the upper layers of the porous reef rock (endolithic algae)  benthic and interstitial diatoms  phytoplankton
  23. Tuft algae Zoo xanthellae Coralline red algae Crustose coralline red algae
  27. HERBIVORES  herbivorous fish  most parrotfish  surgeonfish
  28.  Pacific Gregory (Stegastes fasciolatus)  tidepool blennies
  29.  herbivorous snails and sea hares  most sea urchins  herbivorous crabs  green sea turtles Chiton Tiger cowrie
  32.  Consumers  - primary consumers  Phytoplankton and other single-celled primary producers are eaten by primary consumers.  Due to the large community of primary consumers on coral reefs, phytoplankton levels in coral reef waters can be 15-65% lower than in adjacent open ocean waters.  Benthic grazers and some coral species feed by filtering phytoplankton out of the water while other vertebrate and invertebrate grazers eat algae and seaweed; many species of parrotfish, surgeonfish and blennies have a diet that consists entirely of coralline, filamentous, and calciferous algae.
  33.  Secondary consumers  The animals in this trophic level feed on primary consumers and are consequently carnivorous. Secondary consumers in a reef ecosystem can be divided into four main groups: (1) zoo plankton feeders, (2) corallivores - organisms that feed on coral tissue, (3) feeders on other benthic invertebrates, and (4) piscivores - fish eaters.  Plankton feeders can be small sessile invertebrates like barnacles, corals like sun polyps (Tubastrea sp.) and gorgonians, small damselfish or 15-ton whale sharks.
  34.  Corallivores can be sub-divided into polyp eaters, coral scrapers, mucus feeders etc.  Many species of butterfly fish, damselfish specialize in eating coral polyps  Some common coral scrapers are specific species of triggerfish, parrotfish, blennies, puffers, and butterfly fish.  Some animals that feed on coral mucus are coral guard crabs and shrimps
  35.  Benthic invertebrates like mollusks, gastropods, worms, and crustaceans are eaten by many kinds of fish (e.g. goatfish, wrasses, triggerfish, etc.) and other larger invertebrates  Piscivores are carnivores that eat fish; many species of fish are piscivores as well as some mollusks and arthropods.
  36.  Tertiary (top) consumers  Tertiary consumers are large reef fish at the top of the food chain that eat many smaller fish. Some examples of top consumers in a coral reef ecosystem are sharks, barracudas, and moray eels. Marine mammals such as dolphins and seals, and sea birds, if present, are considered tertiary consumers, too.
  37.  Decomposers (and Detritivores)  Decomposers serve an extremely important function in all ecosystems; they break down dead biological matter and waste products and convert them into usable energy while returning important materials to the environment.  The main decomposers in coral reefs are bacteria; these bacteria play an integral part in the nitrogen cycle whereby ammonia (NH4) is converted into nitrite (NO2) by bacteria in the genus Nitrosomonas, after which nitrite is then converted into nitrate (NO3) by bacteria in the genus Nitrobacter.  The ultimate result is that levels of toxic wastes are kept very low and that waste products are converted into components that are available to producers in a readily- usable form.
  38.  Coral reefs are complex ecosystems that require a balanced trophic structure to function properly and efficiently.  Imbalances can occur in this intricate trophic cascade from the top down or the bottom up. For an example of bottom-up effects, nutrient- rich agricultural run-off can cause a massive increase in primary productivity (e.g. algal blooms), the effects of which often cannot be buffered by consumers fast enough to prevent a coral reef ecosystem from collapsing.
  40. PRODUCTIVITY OF CORAL REEFS  The symbiotic arrangement between the algae and corals results in nutrients being tightly recycled with in coral reefs. This internal nutrient cycling is of primary importance in maintaining the productivity of the reef  The gross primary productivity ranges from about 1500 to 5000 g.C/m2/year, values much higher than those of open tropical Oceans
  41. INTERNAL NUTRIENT RECYCLING How can such rich community grow when the surrounding sea is unproductive?
  42. IMPORTANCE OF CORAL REEFS Protection from coastal erosion Very high diversity = ecological stability Source of important natural chemicals being researched as cures for cancer, arthritis, human infections, viruses, etc Reef fisheries Tourism
  43. THREATS TO CORAL REEFS  There are two types of threats to coral reefs, anthropogenic and natural  Destructive and non-sustainable fishery practices  Coral bleaching – socio economic impacts, reef based tourism and fisheries  Coral mining – construction, lime industry, ornamental purposes  Pollution – agriculture, coastal development  Sedimentation - deforestation
  44. CORAL BLEACHING Coral bleaching occurs when symbiotic zooxanthellae algae is removed or expelled Associated with high water temperatures
  45.  Diseases – Black band, white band and red band diseases were observed in corals especially in shallow areas  In addition to the direct human interferences, global climate change poses serious threat – increase in temperature, and a possible increase in the incidence of storms
  46.  Reefs are subjected to physical-erosion and bio- erosion  Physical erosion – intense wave action, currents, tropical storms  Bio erosion  Removal of large no. of animals from reefs may alter the ecology  Sea urchins graze up on the coral frame work ( fish, molluscs are over fished)
  47.  Crown of thorns star fish – Acanthaster planci ( triton snail) Destruction of Great Barrier Reef  Others  As building material – Maldive islands  For ornamental purposes  Destructive fishing methods – dynamite, sodium cyanide  Anchoring – Reefs of Florida
  48.  Walking over the reef during low tide  Mangrove deforestation – Gulf of Kutch