The Great Barrier Reef Flashcards
GBR: Spatial patterns and dimensions: location, altitude, latitude, size, shape and continuity.
GBR is a diverse ecosystem (330+ different species) + largest CR system with an area of approx 350,000km², hugging the coast of QLD.
Located in the Euphotic zone -> a prerequisite for coral formation due to photosynthesis
Located near the Equator: temperature must be in the range of 23- 29°C -> rise in water temp puts stress on coral algae -> coral bleaching.
Requires continuity / stable, saline conditions -> elevated levels stunt growth + zooxanthellae could die.
-> has over 3000 + individual reefs which form the GBR.
GBR: The dynamics of weather and climate -> Atmosphere El Nino
La Nina
Yes, La Niña typically increases precipitation over the Great Barrier Reef (GBR) region.
During a La Niña event, the sea surface temperatures in the central and eastern Pacific Ocean are cooler than average. This change affects weather patterns globally. In Australia,
La Niña is associated with wetter-than-normal conditions, especially in the northern and eastern parts of the country, including the Great Barrier Reef area.
This increased precipitation can lead to more runoff from the land, which can affect water quality and the health of the reef.
Walker circulation and increase upswelling
GBR: Tropical storms:
Tropical cyclones assist in shaping the reef ecosystem
-> 10-15 years after heavy cyclones till return to normal.
Tropical cyclones also cause damage to the corals themselves
-> Ex-Cyclone Jasper exposed 20% of the GBR to waves that could destroy coral.
Causes large volumes of freshwater flood onto the reef from coastal river systems the salinity level in the waters of the reef is altered
GBR: Hydrological process
GBR precipitation is 80 inches per year, due to the very warm sea temperatures that result in high levels of evaporation.
Connectivity supports genetic diversity and resilience of reef populations
Nutrient transport and organism across the reef
Thermal regulation: mitigate water temperatures as it redistributes.
Evaporation caused by sun’s heat on reef’s waters -> increase in salinity & add concentration of salts which affects local aquatic life.
Nutrient Loads → Runoff can also carry nutrients and sediments that may affect coral health and the overall ecosystem.
-> East Atlantic Current 3km/h shift southward -> disturbing the delicate balance in coral sea temperature range.
-> Carries warm water down the coast to Tasmania.
GBR: Geomorphic Processes:
The coastal zone is notably prone to erosion, especially on slopes and close to waterways.
-> Burdekin river 4 million tons / year of sedimentation reduces coral sunlight and boost algae in the GBR.
GBR is mostly made of CALCIUM CARBONATE (lime)–> impacted by chemical weathering and coral’s lime shells are broken down by chemical reactions.
Mechanical weathering to coral caused by cyclones leading to large blocks of broken coral (Bommies).
(Biological) Mechanical weathering caused by parrotfish, sponges and other species, physically breaks the coral and moves them throughout the reef.
GBR: Biogeographical processes Invasion
Foreign species enter an ecosystem, affecting an ecosystem through disrupting food web)
CHALLENGE:
Natural change
GBR is seen in large plagues which greatly distribute the dynamic equilibrium = hard for the ecosystem to recover
Rate of Change: Catastrophic ; for short periods of time
Outbreaks have been more frequent in recent years due to human modification to the ecosystem -> Agricultural runoff has resulted in the abundance of nutrients i.e Phosphorus
RESPONSE:
Program scale and effort: The crown of thorns is extensive, resulting in multiple vessels to patrol. The Program secured $58 million from Australian government in 2018 to enhance efforts
2018 - 2021 has led to the reduction of 700,000 COTS reef -> help reduce the outbreak
More than 100 trained divers are engaged working in 20 vessels
GBRMPA has highlighted that infested zones are starting to recover, with infected areas seeing a 20% increase of coral cover.
Highly effective.
GBR: Biogeographical processes succession
2 types Primary & Secondary
Primary succession coral seeds are dispersed by birds or currents, colonising a barren environment -> a form of ecological succession which creates a biodiverse habitat.
-> Michaelmas Cay
Secondary succession is the repopulation of an area that is recovering -> often after an invasion of weather event.
-> COTS outbreaks
GBR: Biogeographical processes Modification
Often leads to a more vulnerable ecosystem, due to one species only growing.
Less diversity = more vulnerable
Northern & central GBR has seen growth of hard cover coral -> growth of one species called Acropora (fast branching hard coral) however as it is vulnerable to COTS, coral bleaching & storm damage.
The GBR is more susceptible to future damage -> lower resilience.
GBR: Biogeographical processes Resilience
GBR high biodiversity leads to high resilience to cyclonic damage
All coral populations are affected by rising sea temps
GBR is threatened by multiple sources i.e COTS and climate change. Most of these are human induced.
GBR has low elasticity = long time to recover, leaving them susceptible to continuous climate change.
GBR: Nature and rate of change
for intro
The GBR has experienced a 50% decline in coral cover since the 1980s due to factors like coral bleaching, cyclones, and crown-of-thorns starfish outbreaks.
GBR: Tropical Cyclones:
Nature
Natural Change
Create large waves which damage / exposes coral
->20% of GBR reefs were exposed by cyclone Jasper 2024
Bring large amounts of freshwater onto the reef which alters salinity levels
The increased turbidity caused by the erosive power of these storm
Rate of Change:
Catastrophic
GBR: Coral Bleaching:
Nature:
Human induced change
Bleached coral isn’t dead yet, it’s just in a vulnerable state and only dies if the water doesn’t cool down
-> In 2016, 22% of the coral was killed off across the Great Barrier Reef
Rate of Change:
Catastrophic
Coral bleaching happens in patches over relatively short periods of time when the temperature is high (bleaching events)
-> 2016: some regions saw 67% of their coral bleaches
GBR: Human impacts
Recreational and Commercial Sea Vessels:
Challenges:
The boats’ heavy metal anchors damage the reef’s coral formations and dredge up the seagrass beds
-> Zoning plan which resticts trolling to only the (Olive Green) zone or buffer zone, in which could only catch pelagic fish species such as Tuna.
Ships crashing into the reefs 40% are bulk carriers such as coal while 10% are oil
1987: 6000 ships have crashed into the GBR
-> 2010 Chinese bulk carrier created a 3km scar on the ground
-> lead to immediate effects on the reef as oil leaks out, covering the surface which prevents photosynthesis -> disruption of reef food web.
Boat owners vent their onboard sewerage systems while at sea, releasing raw sewage into the oceans.
-> GBRMPA banning of dumping 12 nautical mile
33% of the park placed into highly protective zones -> plan enacted in 2004 resulted in the reef split into 9 different zones
Pink zone (preservation zone) bans all human access except for scientific research which required as permit -> preserving of genetic diversity and precautionary principles
James Cook university found in green zone (commercial fishing) species 1.7 times the average size of fishing due to zoning
Limitation: Zoning results in ecosystem simplification -> with the need for a careful balance between ecocentric and anthropogenic views such as commercial fishing and coal transport. If fixed, highlight sufficient management strategies.
GBR: Human impacts
Tourism:
Positives:
2.4 million annual visitors, generating AU$6.4 billion and supports over 64,000 jobs.
1990’s found that breeding cycles in seabird colonies were disturbed by tourist activities
Tourism such as recreational diving is the most intense human activity -> leads to human to break off coral.
-> Tourism and recreational Reef Advisory Committee, produces educational materials in order to highlight the fragility of the GBR coral and ecosystem.
+
Tourist boats: speed limits are enforced in many part of the reefs reduce the damage caused by the wake and propulsion of boats
-> restriction of tourist to only 7% of the GBR, in order to protect recovering areas from unnecessary human damage.
-> forcing organisations to have a tourist permit and must only use specially endorced vessels.
