{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Eosc 270 Lecture Notes - March 17th

Eosc 270 Lecture Notes - March 17th - Eosc 270 Lecture...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Eosc 270 Lecture Notes March 17 th , 2009 Natural Disturbances: 1. Storms & Hurricanes 2. Bleaching 3. Outbreak of predators 4. Competition (between corals & between corals & algae) 5. Disease (fungal, bacterial infections) 6. Mass mortalities of reef herbivores (fish that keep algae in check disappear so algae populations increase & kill coral) Storms & Hurricanes: - physical destruction (massive waves), run-off (freshwater input from land), sedimentation (corals don’t like freshwater or sediments), nutrients (algae benefit from nutrients to the detriment of corals) - effect of storm will depend on: duration, intensity & frequency of storm; species, morphology & depth of the coral - if duration between storms is too short & the intensity of storms is too high, corals will not be able to recover - now more intense & more frequent hurricanes due to climate change - intermediate disturbance is good & leads to higher diversity because it reduces the dominant species Coral Bleaching: - loss of colour due to loss of dinoflagellates that are normally associated with corals - natural occurrence in corals, however, now more common & widespread - due to stressed polyps - triggers: >30 C temp (threshold), high UV, nutrients, salinity, sediments, air exposure - non-uniform across reef (environmental or intrinsic differences in corals that makes them more or less susceptible) - corals can either voluntarily get rid of zooxanthellae (loss of suboptimal zooxanthellae in order to replace by more resistant genetic strain) o some zooxanthellae have higher temp thresholds o sacrifice short-term health for long-term advantage - mass bleaching events (not natural) o strong El Nino related warming event destroyed 16% of corals in 9 months o sedimentation, fishing & mining contributed to a further 11% of corals lost o sea temp in the tropics has increased by almost 1 C over the past 100 years & will continue to increase due to global warming o reef-building corals are currently living close to their upper thermal limit therefore small increases in temp will have big impact - 1997-1998 El Nino: o percentages indicate how much of corals were affected by El Nino event in those specific areas
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
o 14% of world’s reefs are in “critical stage” (loss expected in 2-10 years) o 2030 not expected to have any corals left Predator outbreak: - crown-of-thorns starfish ( Acanthaster planci ) feeds on adult corals -
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 6

Eosc 270 Lecture Notes - March 17th - Eosc 270 Lecture...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon bookmark
Ask a homework question - tutors are online