Coral Reefs Warm, shallow, tropical ocean waters Warm, shallow, tropical ocean waters “Rainforest of the Sea” “Rainforest of the Sea” High production High production High organismal diversity High organismal diversity High structural diversity High structural diversity Provides food & shelter to many organisms Provides food & shelter to many organisms Provides natural products Provides natural products Source of many drugs and chemicals Source of many drugs and chemicals

Phylum? Phylum? Cnidaria Cnidaria Includes? Includes? jellyfish, sea anemones, corals jellyfish, sea anemones, corals Key shared characteristic? Key shared characteristic? Cnidocytes or “stinging cells” Cnidocytes or “stinging cells” Colony of polyps Colony of polyps Calcium carbonate skeleton Calcium carbonate skeleton Key players

Process Coral growth is slow… Coral growth is slow… ~ 1 cm / year ~ 1 cm / year Other organisms help Other organisms help Zooxanthellae Zooxanthellae single-celled algae single-celled algae See Fig. 14.1, Castro & Huber See Fig. 14.1, Castro & Huber symbiotic relationship symbiotic relationship Coralline algae Coralline algae Multicellular Multicellular Produces its own CaCO 3 skeleton Produces its own CaCO 3 skeleton Adds to reef and helps “glue” it together Adds to reef and helps “glue” it together

Types of Coral Reefs Fringing reefs Fringing reefs Shallow coastal waters Shallow coastal waters Vulnerable to sediment, freshwater runoff, & human disturbance Vulnerable to sediment, freshwater runoff, & human disturbance Reef flat Reef flat Wide & influenced by low tides Wide & influenced by low tides Reef slope Reef slope Dense with corals Dense with corals

Barrier reefs Barrier reefs Parallel the coast Parallel the coast Separated by lagoon Separated by lagoon Inner reef (back reef slope) protected Inner reef (back reef slope) protected Outer reef slope Outer reef slope Dense Dense Spur & Groove Spur & Groove Windward side Windward side Shock absorbers Shock absorbers

Atolls Circular reef left by subsiding island Circular reef left by subsiding island Windward side Windward side Lots of wind and waves Lots of wind and waves Tradewinds (30 0 to 0 0 ) Tradewinds (30 0 to 0 0 ) Spur & groove Spur & groove Coralline algae Coralline algae Leeward side Leeward side Sheltered Sheltered Begins as fringing Begins as fringing Volcanic island Volcanic island Island subsides Island subsides Creates barrier reef Creates barrier reef Subsiding continues Subsiding continues Ring left behind Ring left behind Atoll Atoll

Limitations of Coral Reefs Shallow water Shallow water Hard substrate Hard substrate Limited temperature range Limited temperature range ~20 – 32 Celsius (68 – 90 Fahrenheit) ~20 – 32 Celsius (68 – 90 Fahrenheit) Sensitive to lowered salinity Sensitive to lowered salinity Sensitive to human impacts Sensitive to human impacts Pollutants Pollutants Fuels, waste, sunscreen Fuels, waste, sunscreen Increased run-off from population growth Increased run-off from population growth eutrophication eutrophication Coral bleaching? Coral bleaching? Loss of zooxanthellae Loss of zooxanthellae Increased turbidity (sediments) Increased turbidity (sediments) Decreased salinity Decreased salinity Weather events Weather events Hurricanes Hurricanes Cyclones Cyclones