Week 8a: Mass Bleaching in the Great Barrier Reef

what is a collapse profile

represents the rate of change in a chosen indicator variable

types of collapse profiles

• abrupt: pulse/one off events

• smooth: press pressures

• stepped: consecutive events, ecosystem does not recover and eventually collapses

• fluctuating: events that decrease health of ecosystem, but ecosystem recovers. ecosystem is resillient

3 main methods of ecosystem monitoring

• satellite

• aerial survey

• underwater survey

Satellite: what does it answer, and what is its +/-?

Where did thermal stress occur?

+: Broadest spatial coverage.

-: Temperature data from satellites measured the pressure, not bleaching itself

Aerial survey: what does it answer, and what is its +/-?

Where was bleaching occurring/how widespread was visible bleaching?

+:Detects reef scale bleaching patterns, extensive spatial replication possible, broad coverage

-: limited underwater detail

Underwater in-situ survey: what does it answer, and what is its limit?

Did aerial scores reflect coral condition underwater? Able to directly observe coral condition at selected reefs and sites.

+: Provide fine-scale detail and ground-truthing aerial scores.

Why need to observe more than 1 reef?

Reef condition varies, 1 site is unrepresentative

Why are all 3 monitoring methods needed?

No single method provides scale, detail and validation simultaneously → all 3 methods are needed.

Press/pulse pressures on a global scale for coral

Press: Temperature rise, ocean acidification, salinity

Pulse: Crown of thorns starfish, floods, storms, heatwave

Press/pulse pressures on a regional scale

press: habitat loss

pulse: runoff/pollution

A fluctuating ecosystem trajectory (graph)

stressors of different severities can affect an ecosystem at same/different times, before recovery is complete

a short section of the graph may not represent the long term trajectory