L6 : conservation ecology and marine biodiversity Flashcards

1
Q

biodiversity and ecosystem resilience
[case study - tropical reefs]

A
  • biodiversity hotspots
  • protect coastal habitats and ecosystems
  • nursery grounds
  • feeding grounds
  • carbon sinks
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2
Q

Role of grazers in reef communities

A
  1. many grazers are predators (feed on coral polyps)
  2. many are algal specialists
  3. many “specialists” are in fact omnivorous
    - specialist mouth structure
    - specialist digestive structures
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3
Q

grazer importance

A
  • highest grazing rates (removal of 1^degree prod) of any habitat on earth
  • important role of space clearing
  • clear coral rock of algae to provide space for settlement, and maintain low standing crop of algae that would otherwise overgrow corals
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4
Q

healthy reef

A
  • clear water
  • abundant coral
  • species diversity
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5
Q

over-fishing

A
  • shift from subsistence to cash economies - increased pressure on reef fish populations
  • reef fish species have crucial role in maintaining balance between algae and coral
  • overfishing removes biological limits on algal growth -> algae dominate -> phase shift
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6
Q

phase shift

A

a change in the ecosystem state in response to a persistent change in external environmental conditions,

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7
Q

phase shift - macroalgal dominance

A
  • turbid water
  • limited coral
  • reduced biodiversity
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8
Q

removing top predators

A
  • removing sharks allows increase in mid-level predators
  • these place extra pressure in grazing fishes
  • unable to keep up with algal growth
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9
Q

Excess nutrients

A
  • corals prefer low nutrient conditions
  • nutrients are captures and recycled within biomass
  • high nutrients cause uncontrolled algal growth -> out compete corals -> phase shift
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10
Q

status of world coral reefs

A
  • 20% destroyed
  • 24% at imminent risk of collapse under human pressure
  • 26% under long-term threat
  • most damages in SE Asia, Indian ocean and Caribbean
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11
Q

role of urchins and phase shift

A
  • disease in urchin species (Diadema antillarium) in the Caribbean
  • increased algal cover
  • decline in reef biodiversity
  • recovery of urchin has reduced algal cover 65% to 5%
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12
Q

Crown of thorns starfish

A

(Acanthaster planci)
- voracious pred of coral polyps
- can cause permanent damage to reefs
- natural preds have been fished out, larvae are benefiting from eutrophication

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13
Q

k-species

A

produce offspring that each have a higher probability of survival to maturity

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14
Q

Ecological effects of reserve networks

A
  1. increasing evidence that a network of reserve buffers against the vagaries of environmental variability and provides significantly greater protection for marine communities that a single reserve
  2. effective network needs to span large geographic distance and encompass a substantial area to protect against catastrophes and provide a stable platform for the long-term persistance of marine communities
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