Marine Ecology Coral Reefs

CORAL REEFS Most diverse and productive communities DIVERSITY! Protection from wave energy Foster ecological oases Mangroves Seagrass beds Iconic ecosystem Sensitive Threatened by humans

Development and Distribution http://data.unep-wcmc.org/datasets Biogenic 30* N and S of equator Cover <0.1% of global ocean surface area Host >25% of fish species Better than rainforests! Species per unit area

Development and Distribution Hermatypic Reef-building Tropics Growth and distribution influenced by physical environment Ahermatypic Non reef-building Mostly world-wide

Development and Distribution Temp: 18-36*C Types of reef based on; Underlying substratum Existing carbonate reef Igneous rock Sea level changes Light levels Wave action

Patch Reefs Bommies Small reefs Grow in shallow lagoonal areas Surrounded by sand Deeper Don’t go above surface at low tide

Fringing Reefs Develop on shelving shores Rocky tropical islands Corals settle and grow on well-lighted and shallows areas Grow toward surface

Barrier Reefs Surround tropical islands Separated from land by lagoon Usually 1-10km wide Line of breaking surf May develop from fringing After sea level rise Grow quickly Exposure to wind/currents

Atolls A ring of reef with low-lying islands surrounding a lagoon 10km (or more) across Biological diversity Seabird colonies Charles Darwin Formation theory http://www.youtube.com/watch?v=vrD1O5hex6Y

Reef Growth Not continuous Net reef growth Periods of rapid growth Periods of bioerosion Net reef growth Fastest: 20m in 1000yrs Usual: 3m in 1000yrs Growth affected by sea-level Glaciers

Corals and Coral Communities CaCO3 skeletons Polyps Protection and nutrients Zooxanthellae Photosynthesizers Dinoflagellate Can live independently No flagella/motility in polyp

Corals and Coral Communities Zooxanthellae Transmitted during reproduction Obtained from seawater Produce energy Autotrophic Waste from host- RECYCLE! High rate of photosyn more calcium carbonate

Coral Reproduction Recruitment Sexual and asexual Hermatypic Sexual http://www.youtube.com/watch?v=wsaZ8-I7akg Recruitment Sexual and asexual Hermatypic Polyps; asexual budding Break off, settle, grow Sexual Long-distance dispersal Gonochoric- one Simultaneous- both Sequential Hermaphrodites- change

Coral Reproduction Brooding Broadcasting Fertilized internally http://www.youtube.com/watch?v=06BPlLATtgc Brooding Fertilized internally Planula develops inside polyp Broadcasting Certain period of the year Lunar cycle Synchronized Common cues Too many eggs for the evil predators to eat

Coral Reproduction Fertilized eggs Settle in 1-3 days Zooxanthellae aquired after settlement and metamorphosis Brooder larvae contain them Calcified base plate Grazing helps growth Influenced by environment http://www.youtube.com/watch?v=_Mt0h5v4xos

Coral Reproduction LIGHTlightlightlightlight Reef accretion Sunburn! 0-10m Hermatypic Rare below 30m Shallow, well-lit zone More light Less predators Sunburn! Stenothermal

Coral Growth Evolved in stable temp Evolved in variable temp Less tolerant Evolved in variable temp More tolerant Salinity 33-35ppt Wave action currents Nutrient spreading Can be harmful Hurricanes

Coral Growth Sediments Some coral can remove it http://www.youtube.com/watch?v=9pdmkckANH4 Sediments Some coral can remove it Smothering, abrasion, shading, recruitment inhibition Pulse Sediment Storms Not as harmful Suspended Sediment Human actions Reduced light for coral

Productivity Production recycled within the reef Carbon fixation Less than half the carbon they fix is available Few organisms feed on coral directly Reef algae Very productive Grazed on and carbon

Productivity Phytoplankton! Support zooplankton Support larger consumers Currents carry them across reef Currents carry them from outlying water, and over the reef… Then they can be eaten- YUM!!

Productivity 24-h cycle used to measure Day- photosynthesis Night- respiration Excess Production- net production which occurs (E) Photosyn/Respiration ratio (P/R ratio) E=0, P/R of 1 E is relatively low Competition Nutrient recycling

Reef Fauna Could be home to over a million species Diiiiiiiiiverse! Not uniform Determined by reef history and environment Reef building coral evolved over 200 mil yrs ago Large scale extinctions Every 20-30 million years

Reef Fauna Diversity Study Influenced by isolation Began; 1950’s and 60’s Focused on ecology Realized instability Research still young

THREATS! Humans (of course) Direct Indirection We suck!! Increased sedimentation Fishing Ship stupidity Pollution Indirection Climate change Over-fishin

Disease Yes, corals get sick too Black band Pathogens and parasites Can be aggravated by human influences Black band 1st recorded Affects brain coral Caused by cyanobacteria Create anoxia in the tissue Physically damaged More susceptible

Bad Weather Storms Cyclones Hurricanes Branching corals Reef fish (10-25* N/S) Fast growing coral that relocate Hurricanes Fast growers Acropora

Climate Change Climate change Rising sea level Should be good for shallow water coral Increased ENSO due to temp increase HUMANS Nutrient input Deep corals will not do well

Coral Bleaching Stressed coral expel their zooxanthellae http://www.youtube.com/watch?v=60jof35WuAo Stressed coral expel their zooxanthellae Skeleton becomes visible Prolonged bleaching leads to coral death Bioerosion takes over Algae move in Reduce reef accretion Fish species will be lost High water temperature http://www.youtube.com/watch?v=aEdoizgeNJk

Coral Predators Crown-of-thorns starfish Feed on living coral http://www.youtube.com/watch?v=2fE2gIARQWA Crown-of-thorns starfish Feed on living coral Free-spawners 12-60mil eggs in a spawning season Evert their stomach on coral, and secreting an enzyme which breaks down the coral Fishing may have reduced their predators

Pollution, Sediments, Nutrients Deforestation, port development, and dredging Run off Increased sediment load Nutrients from run-off Increased algal growth Phosphate; big no-no Oil pollution http://www.youtube.com/watch?v=rkKs-5JGSoo

Fishing Expanding fisheries Habitat-destructive fishing Direct damage Reef drive netting Trapping Blast/chemical fishing Unselective Illegal

Reef Growth Limestone produced And broken down Coral rubble/sand Balance between accretion and bioerosion Erosion by organisms Grazers Mollusc, echinoderm, fish Loss of hermatypic corals

Reef Animals Difficult to record densities Used as ‘laboratories’ Behavior and ecology Carrying capacity Recruitment limitation hypothesis Population sizes limited and determined by rates at which larval fish from plankton to adult http://www.youtube.com/watch?v=UB7tqiL-Eqs

Reef Animals No one species can out-compete the other Reef structure is complex Symbiosis Coexist Cleaner fish Burrowers http://www.youtube.com/watch?v=xaJdXO_j2MY http://www.youtube.com/watch?v=UJbPej8uytw

Reefs and Humans Provide food and income Subsistence fishing Tourism Not recorded Tourism Great Barrier Reef Over 10mil per year Towns can be supported by revenue Ecosystem services; help humans Coastal defense Coral mining, bleaching, sedimentation