1. Coral Reefs

2. Scleractinian corals Phyllum Cnidaria –Class Anthozoa Subclass Zoantharia –Order Scleractinia Only polyp phase (no medusae) Colonial organisms CaCO 3 exoskeleton Symbiosis with zooxanthellae

3. http://krupp.wcc.hawaii.edu/

6. Cnidarian Polyp Antozoan corals form Reefs by accumulation of exoskeletons

7. Zooxanthellae Non-motile naked dynoflagellates Embedded in transparent polyps Use corals wastes (CO2 + nutrients) Contribute 60% of primary production to polyp Corals get ~50% energy from Zoox; ~50% from heterotrophic feeding

8. Scleractinian corals stats Average Colony Age ~ 100 years Growth rates ~ 0.5 – 20 cm/year –Boulder corals  slow growth (0.5-1) –Branching corals  fast growth (10-20) Corals reefs –Originated in Triassic (220 mya) –Distributed between 24 o N – 24 o S latitude

9. Coral Reefs environmental requirements Temperature (18 – 30 o C) –Low Solubility of CaCO 3 at high temp. Depth (0-150 m) –Within photic zone –Below low tide Sedimentation –Low tolerance (prefer clear waters) Salinity (33‰ and up) –Low tolerance of fresh water Wave action –(high O 2, clear water and pelagic food supply)

10. Coral reef distribution and Diversity IndoPacific Diversity Eastern Ocean Dominance

11. Global Surface Currents

12. Chlorophyll Concentration

13. Ecosystem Productivity (Annual net productivity)

14. Coral reef productivity Efficient Coral – Zooxanthellae simbiosis –Little loss of nutrients to water Steep drop-offs promote increase pelagic productivity –Backreef eddies, local nutrient upwelling Partially closed systems –high ammounts of benthic organic detritus

15. Evolution of Coral Reefs (Darwin) Fringe reefs Barrier reefs Atolls subsidence ~0.03 mm/yr = 1,200,000 mm/40,000,000 yr

16. 1950 Enewetak

21. Cross-sections of various types of coral reefs

22. Sandy Lagoon Turtle Grass Lagoon

23. Patch reef lagoon

24. Reef flat

25. Reef crest

26. Reef crest – high wave energy

28. Shallow seaward reef

29. Shallow seaward reef – Acropora corals

30. Reef outer slope

31. Buttress Zone with sand channels

32. Outer reef wall

33. Coral Reef Zonation Lagoon –Filled with sediments, corals grow or not according to sediment suspension & re-suspension rates Reef flat –Protected, clear oceanic water, high growth rates Reef crest –High wave turbulence, tidal exposure, calcareous algae can dominate Outer or seaward reef slope –High coral complexity, buttress formations Outer reef wall or drop-off –Low light adapted species, Deep coral morphs, heterotrophy

35. Present degradation of coral reefs Natural Disturbances: –Hurricanes and Storms –Coral Bleaching –Predation of Corals –Coral Diseases Human Indirect Disturbances –Land Sedimentation –Eutrophization (coral diseases) –Overfishing (trophic cascading) –Global Warming (bleaching)

36. Hurricanes, Typhoons & Cyclones

37. Hurricanes & Typhoons Destroy reefs by: –Wave Action –Sedimetation Hurricanes hit a specific reef every ~ 20 years Coral growth rate ~1-20cm

38. Coral Diseases Black-Band Disease Cyanobacteria infection Affects boulder corals White-Band Disease Bacterial infection Affects Acropora spp. St. Croix ~95% kill

39. Aspergillosis Bacterial Bleaching Black Band Dark Spots White Band White Plague White Pox Yellow Band

41. Future of Coral Reefs

42. Coral Bleaching Expulsion of Zooxanthellae symbionts Causes: –Decrease in Salinity River runoff, heavy rains –Decrease of Light Sedimentation – Turbidity –Increase water Temperature (+30’s o C) (enhanced by high UV exposure) El Niño – Mass Bleaching Global Warming +2 o C / 100 years

43. Zooxanthella

44. Coral Bleaching www.ogp.noaa.gov