1. Corals Landlords of the Reefs

2. What is a coral? What is a coral? Phylum Cnidaria Phylum Cnidaria Cl. Anthozoa Cl. Anthozoa Order Gorgonacea (soft corals, gorgonians) Order Gorgonacea (soft corals, gorgonians) Order Scleractinia (hard/stony reef builders) Order Scleractinia (hard/stony reef builders)

3. What should you know about corals? They are animals Plants live inside of them Two kinds Soft corals Hard corals (These build reefs!) They are made of tiny polyps (which look like upside-down jellyfish)

4. What’s a Polyp? Tentacles release stinging cells when something brushes by them Polyps make their own limestone cup to hide in during the day At night, polyps come out to catch plankton floating by.

6. “Nerve Net”

7. Zoo-what!?! Algae, Coral Polyps’ Tenants Inside polyps live zooxanthellae, which are algae. Inside polyps live zooxanthellae, which are algae. Zooxanthellae give corals their color. Zooxanthellae give corals their color. Since algae are plants, they use sunlight and CO 2 to make food (photosynthesis). Since algae are plants, they use sunlight and CO 2 to make food (photosynthesis).

8. Symbiosis: So Happy Together Two organisms living together and helping each other is called symbiosis. Two organisms living together and helping each other is called symbiosis. Zooxanthellae make oxygen, remove the polyp’s wastes, and make food for the polyp from photosynthesis. Zooxanthellae make oxygen, remove the polyp’s wastes, and make food for the polyp from photosynthesis. Coral polyps protect the zooxanthellae, release CO 2, and provide it with necessary nutrients from their own waste. Coral polyps protect the zooxanthellae, release CO 2, and provide it with necessary nutrients from their own waste.

9. Hard Corals - Scleractinians The Reef Builders Polyps build hard limestone (CaCO 3 ) cups around their bases Polyps build hard limestone (CaCO 3 ) cups around their bases The cups cement together to make a coral colony The cups cement together to make a coral colony Reefs are made of hundreds of hard coral colonies next to and on top of each other Reefs are made of hundreds of hard coral colonies next to and on top of each other Hermatypic – reef builders Hermatypic – reef builders

10. Coral Colonies Corallite = CaCO 3 structure around polyp Gastrovascular cavities of polyps connected by tube

11. Colony Morphology Arrangement

12. Feeding Suspension feeders Feed on zooplankton, small organisms on reef Use cnidocytes to stun prey Most are nocturnal (during day the polyps are retracted into corallites Mesenterial filaments – extruded by gut, absorb digested organic matter in sediments Bacteria absorb DOM, polyps feed on bacteria Up to 90% nutritional needs - zooxanthellae

13. Reproduction Asexually budding fragmentation Sexually some are hermaphroditic (have both testes & ovaries) broadcast spawners – release gametes into sea few are brooders – sperm boradcast, eggs retained & fertilized internally, planula larvae released

14. Life Cycle of a Broadcaster Coral Spawning Pacific reefs – synchronous, brief annual event Caribbean – nonsynchronous, long periods

15. Reef Formation Constructive & Destructive phases Destructive = bioerosion usually initiated by boring organisms, continued by storms/heavy surges damaging weakened areas Constructive accumulation of sediments, pieces of broken corals, new planula larvae settle on newly exposed substrate surfaces Reef Structure

16. Types of Reefs 4 types of reefs 4 types of reefs 4 types of reefs 4 types of reefs 1. Fringing Reefs 2. Barrier Reefs 3. Atolls 4. Patch Reefs

17. Fringing Reefs borders shores of tropical islands/continental masses borders shores of tropical islands/continental masses Common in S. Pacific & some parts of Caribbean Common in S. Pacific & some parts of Caribbean

18. Barrier Reefs furthest offshore furthest offshore form when land masses sink & fringe reef separates from shore form when land masses sink & fringe reef separates from shore assoc. with lagoons or deep channels assoc. with lagoons or deep channels common in Caribbean and Indo-Pacific common in Caribbean and Indo-Pacific Great Barrier Reef, Austr. 2100 km

20. Atolls elliptical; central lagoon; in deep seas elliptical; central lagoon; in deep seas 130 km diameter 130 km diameter form as volcanic islands sink form as volcanic islands sink Darwin's Volcano Darwin's Volcano Darwin's Volcano Darwin's Volcano

21. Patch Reefs small, numerous small, numerous found in lagoons of atolls or barrier reefs found in lagoons of atolls or barrier reefs can be created by heavy grazers like sea urchins can be created by heavy grazers like sea urchins

22. Reef Types – recap!

23. Typical Reef Zones Reef zones Reef zones Reef zones

25. Fig. 15-13b: view from above, spur & groove formations

26. Where do we find coral reefs? Distribution determined by: Distribution determined by: Temp. Temp. Light Light Sediment accumulation Sediment accumulation Salinity Salinity Wave action Wave action Duration of air exposure Duration of air exposure

27. Distribution Most are tropical (annual temps. 23 ⁰ C- 25 ⁰ C) Most are tropical (annual temps. 23 ⁰ C- 25 ⁰ C) Most < 60 ft. deep (25 m or less) Most < 60 ft. deep (25 m or less) Moderate wave action Moderate wave action Saline areas (less freshwater runoff/input) Saline areas (less freshwater runoff/input)

28. Pacific ReefsAtlantic Reefs older growth seldom exceeds 60 m > % coverage greater diversity of organisms more extensive algal ridges mostly diurnal sexual reprod. growth extends beyond 100 m deeper buttress zones often dom. By Millipora(fire coral) > biomass of sponges mostly nocturnal fragmentation

29. Reef Ecology Source of Nutrients Source of Nutrients req. abund. N 2 and P req. abund. N 2 and P possibly from runoff, upwelling, flow rates, recycling, N 2 fixation by bacteria, fecal matter possibly from runoff, upwelling, flow rates, recycling, N 2 fixation by bacteria, fecal matter Photosynthesis Photosynthesis Zooxanthellae, algae, phytoplankton, sea grasses Zooxanthellae, algae, phytoplankton, sea grasses Turf algae & zooxanthellae fix the most C Turf algae & zooxanthellae fix the most C

30. Ecology cont’d Productivity Productivity High as result of production and efficient use of nutrients High as result of production and efficient use of nutrients 1 of the most productive ecosystems 1 of the most productive ecosystems Exactly how productive is not really known! Exactly how productive is not really known!

32. Coral Reef Community Complex & biologically diverse Complex & biologically diverse Light, space & other resources are limited therefore there is much competition Light, space & other resources are limited therefore there is much competition Slow growing corals use mesenterial filaments to kill competitor polyps Slow growing corals use mesenterial filaments to kill competitor polyps Faster growing corals respond w/ sweeper tentacles Faster growing corals respond w/ sweeper tentacles

33. Slow growers – more aggressive Slow growers – more aggressive Some take advantages of different locations Some take advantages of different locations More massive corals – more shade tolerant – deeper More massive corals – more shade tolerant – deeper Faster growing, branching – dominate upper, shallow reef Faster growing, branching – dominate upper, shallow reef Corals in shallow water rely on grazing animals to help control algal growth Corals in shallow water rely on grazing animals to help control algal growth

34. Competition Among reef fishes Among reef fishes > diversity than other marine habitats > diversity than other marine habitats 3D structure of reef = microhabitats for fish (& others) 3D structure of reef = microhabitats for fish (& others) Competitive Exclusion Principle Competitive Exclusion Principle Time of day, size of prey, position of water column, etc. provide unique niches Time of day, size of prey, position of water column, etc. provide unique niches Natural mortality (incl. predation) controls population sizes Natural mortality (incl. predation) controls population sizes Chance determines larval settlement Chance determines larval settlement

35. Effects of Grazing Urchins & fishes prevent algal overgrowth Urchins & fishes prevent algal overgrowth Diadema (long spined urchin) is a keystone predator Diadema (long spined urchin) is a keystone predator

36. Effect of Predation Some predators prey on coral competitors giving some inferior corals advantage Some predators prey on coral competitors giving some inferior corals advantage Some feed directly on polyps & limit their growth Some feed directly on polyps & limit their growth corallivores corallivores Parrot fish, surgeon fish Parrot fish, surgeon fish add sediment to reef (do not digest the coral skeletons) add sediment to reef (do not digest the coral skeletons)

37. Symbiotic Relationships help organisms exploit niches, survive help organisms exploit niches, survive Mutualism – zooxanthellae Mutualism – zooxanthellae Cleaning stations Cleaning stations Inverts & small fish clean parasites of larger animals Inverts & small fish clean parasites of larger animals Others Others clownfish & anemones clownfish & anemones hermit crabs & snail shells hermit crabs & snail shells

38. Evolutionary Adaptations Adaptive Behaviors Adaptive Behaviors Nocturnal feeders Nocturnal feeders Eviscerate internal organs Eviscerate internal organs Produce toxic mucus Produce toxic mucus Hide @ night Hide @ night Sea CucumberSea Cucmber eviscerating

39. Structural Adaptations – feeding Structural Adaptations – feeding Cnidocytes (cnidarians) Cnidocytes (cnidarians) Appendages Appendages like radioles (hairlike; on Christmas tree worms, filter) like radioles (hairlike; on Christmas tree worms, filter) “feathers” on feather duster worms for suspension feeding Feather Duster worm “feathers” on feather duster worms for suspension feeding Feather Duster wormFeather Duster wormFeather Duster worm “forelimbs” of Mantis Shrimp Mantis shrimp punch “forelimbs” of Mantis Shrimp Mantis shrimp punchMantis shrimp punchMantis shrimp punch Cirri of Crinoids (feather stars) Cirri of Crinoids (feather stars) Radula – molluscs Radula – molluscs Cephalopods – suckers, mantle (jet propulsion), eye sight, modified radula or beak Cephalopods – suckers, mantle (jet propulsion), eye sight, modified radula or beak

40. Protective Body Covering Protective Body Covering CaCO 3 deposits in tissues (algae, corals, sponges) or in shells (molluscs) CaCO 3 deposits in tissues (algae, corals, sponges) or in shells (molluscs) Hardened outer cover & spines (test & spines of sea urchins) Hardened outer cover & spines (test & spines of sea urchins) Bony skin (trunkfish) Bony skin (trunkfish)

41. Role of Color Role of Color Cryptic Cryptic Aposematic Aposematic Disruptive Disruptive Defend territory Defend territory Mating rituals/attract mates Mating rituals/attract mates

42. Threats Human Human Destructive fishing practices Destructive fishing practices Overfishing Overfishing Dynamite Dynamite Cyanide Cyanide Coastal Development Coastal Development Human-induced Climate Change Human-induced Climate Change Coral Bleaching Coral Bleaching Coral Diseases - bacterial Coral Diseases - bacterial

43. Other Threats Pollution Pollution Mining coral Mining coral Collecting coral for commercial trade (trinkets) Collecting coral for commercial trade (trinkets) Boat anchors Boat anchors

44. Coral Bleaching Corals expel zooxanthellae due to: Corals expel zooxanthellae due to: Inc. temps. Inc. temps. Excessive radiation Excessive radiation Aerial exposure Aerial exposure Sedimentation Sedimentation Bacterial infection Bacterial infection Inc. greatly since 1980 Inc. greatly since 1980