coral bleaching

coral bleaching

• Caused by stress

• Stress response - expels zooxanthellae from tissue

• Tissue is clear so you can see the limestone underneath

causes of stress

• High light/ UV levels

• Cold temp

• Low salinity and high turbidity from coastal run off events of heavy rainfall

• Exposure to air during very low tides

• High water temperature

• When stressed the coral is more likely to get sick

thermal stress

• Live close to their thermal maximum limit

• If water gets 1/2 degrees higher than summer average corals gets tressed and bleach

• NOAA satellites measure global ocean temp and internal stress

 

coral recovery

• Recovery possible id stress doesn't last too long

• Some corals can eat more zooplankton to make up for lack of zooxanthellae

• Certain species more resistant to bleaching/ more able to recover

• May regain colour by repopulating their zooxanthellae

  • Algae may come from the water column

  • Algae may come from reproduction of cells remaining on the coral

• Can begin to recover after a few weeks

coral killing

• If stress is severe enough

• Some polyps in a colony might die

• If bleaching is severe whole colonies can die

coral diseases

• High temp/ bleaching can leave corals more vulnerable to disease

• Kill part or all of the coral colony

bioerosion

• Dead coral is more vulnerable to bioerosion

  • Animals wear away the coral reefs limestone structures

hurricanes

• Cause direct physical damage to coral reefs

• Storms cool the water

protect from bleaching

• Cool reefs

• Shade reefs

• Improve water quality

• Reduce other stress

• Reduce overfishing

coral_bleaching (1).pptx