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Find out more about some of the factors impacting our reef systems. Some are wide-spread global effects, others have more localised impacts. Increased frequency of some events and compounding threats (more than one threat impacting on an area) are what result in the biggest challenges for reefs.

The call to action to look after reefs & oceans is loud and clear... and we can all do something to help! 

 

Global Climate Change

One of the greatest threats to coral reefs today is global climate change.  Climate change is a change in global climate patterns due to increased levels of atmospheric carbon dioxide.  Warmer temperatures not only influence climatic conditions on land, but also water temperature, chemistry, and circulation in our oceans.  Threats to coral reefs from climate change include:

  • Increased coral bleaching due to rising water temperature
  • A weakening of the limestone reef structures and a reduced rate of coral formation (calcification) due to ocean acidification
  • Increased damage to the reef due to more frequent and intense weather events such as cyclones and flooding
More information can be found at:
http://www.gbrmpa.gov.au/outlook-for-the-reef/climate-change/what-does-this-mean-for-habitats/coral-reefs
http://www.gbrmpa.gov.au/outlook-for-the-reef/climate-change

 

Sedimentation/Siltation

The erosion of land use surfaces, due to practices such as agriculture and construction, can results in high levels of silt in our waterways.  The impacts of siltation to coral reefs include:

  • Prevention of new coral colonies to form and existing corals to re-colonize.
  • Decreased water quality and increased turbidity
  • Reduced light that is able to reach aquatic plants

 

Nutrient and fertilizer pollution

Nutrients from agricultural and other land use activities can runoff into the local waterways and result in excess levels of nutrients in the water.  The threats of nutrient pollution include:

  • Reduction of water quality
  • Increased likelihood for algae blooms that can:
    • reduce oxygen available for aquatic life,
    • reduce the amount of light that is able to reach aquatic plants
    • increase food available to feed larvae of the invasive crown-of-thorns starfish (COTS)

 

Overfishing

Overfishing is the taking of more fish than the ocean can produce or sustain. Although Australian's waters are managed to maintain healthy fish populations, overfishing can occur.  Impacts of overfishing can include:

  • Reduction of native fish and shellfish populations, possibly to extinction
  • Disruptions to the food web due to the reductions of certain species
  • Disruptions to the reef's ecological balance and biodiversity
  • Impacts to fish size, abundance, and species composition

 

Destructive fishing

Destructive fishing can have a direct physical impact on the reef environment.  Trawling, bycatch, and explosive fishing are some destructive fishing practices that harm marine species and their habitat.  Types of destructive fishing and their threats include:

  • Destructive trawling: can damage sea beds, destroy habitats, increase turbidity, and have large collateral losses of other species
  • High percentage of bycatch: can result in a loss of excessive numbers of marine life (such as turtle, dolphins, sharks, etc.) and reduce species populations unintentionally.
  • Explosives: kill not only the target fish, but kill other non-target fish and harm the surrounding fauna and flora.

 

Recreation and Tourism

Many locals and tourists use coral reefs for boating, swimming, snorkeling, and diving, and some are unaware of the damage they can do to the reef. Possible impacts to the reef include:

  • Localised but frequent anchor damage to corals and seagrass meadows
  • Littering of rubbish can be consumed and damage marine life
  • Boat strikes on marine mammals and turtles
  • Fin damage to corals when snorkeling and diving.
  • Sewage discharge that can increase nutrient pollution
More information can be found at:
http://www.gbrmpa.gov.au/outlook-for-the-reef/Managing-multiple-uses/recreation

 

Crown of Thorns Starfish (COTS)

Crown of thorns starfish are carnivorous starfish that feed on living coral.  COTS are fast growing and can reproduce at rapid rates if the conditions are right.  Poor water quality, especially from excess nutrients, can trigger outbreaks of COTS. Threats of COTS include:

  • Outbreaks of COTS that can damage and kill large areas of coral reefs
More information can be found at:
http://www.aims.gov.au/docs/research/biodiversity-ecology/threats/cots.html
http://www.gbrmpa.gov.au/about-the-reef/animals/crown-of-thorns-starfish

 

Shipping

Although shipping is a highly managed industry, impacts to the reef can be damaging.  Possible threats to coral reefs from shipping include:

  • Damage to the reef from vessel groundings
  • Reduced water quality due to oil and chemical spills
  • Reduced of water quality due to the release of toxic anti-fouling paints
  • Increased nutrient pollution and reduced water quality due to sewage and waste disposal
  • Anchor damage to coral
More information can be found at:
http://www.gbrmpa.gov.au/outlook-for-the-reef/Managing-multiple-uses/ports-and-shipping

 

Port Development/Expansion

The number of ports and port expansions along Australia's coastline is on the rise. The cumulative impact of these ports is a possible cause for concern.  Some of the impacts from port development include:

  • Removal and disturbance of existing habitats such as seagrasses
  • Increased pollutant levels from construction and soil displacement
  • The release and recirculation of sediment, heavy metals, and nutrients from dredging and dredge material (spoils)
  • Degradation of water quality
  • Burial and smothering of coral as well as other benthic fauna and flora
  • Changes to coastal processes and hydrology
  • Injury or mortality to marine wildlife

 

More information can be found at:
http://www.gbrmpa.gov.au/__data/assets/pdf_file/0019/28810/Ports-challenges-for-the-Great-Barrier-Reef.pdf
http://www.depi.vic.gov.au/forestry-and-land-use/coasts/marine/bays-inlets-estuaries-and-lakes/dredging