FACT SHEETS -
CORAL REEF IMPACTS
27 SEDIMENTATION
• Sediments are soil particles, sand and other mineral or organic matter eroded from the land and carried in surface waters.
• Sedimentation is a process where suspended sediments are deposited on a surface by the action of gravity. The sources of sediments are either natural or anthropogenic (man made).
• Natural sediments originate from coastal erosion, storms and runoff or from desert storms. • Anthropogenic sediments are caused by agricultural and aquacultural runoff, deforestation, coral mining, coastal development projects, urban and industrial effluents.
• Sediments can affect the health of coral reefs in two principal ways:
• Suspended in seawater, sediments reduce the amount of light reaching corals and their symbiotic algae, therefore reducing the amount of energy available to the corals.
• As sediments settle, they can smother or bury corals. Corals can clean themselves using mucus, but this process requires energy that the coral could otherwise spend on growth and/or reproduction.
• Whilst offshore coral reefs are generally adapted to low sediment conditions, on the other hand, nearshore coral reefs have evolved in relatively turbid environments.
• Increased levels of sediments discharged from the land are causing significant impacts on some reefs, especially nearshore reefs.
• Sedimentation also affects seagrass meadows, as these organisms rely on sunlight to produce energy.
Further Links:
• The Great Barrier Reef Marine Park Authority (Principal water quality influences and FAQ) http://www.gbrmpa.gov.au/corp_site/key_issues/water_quality/principal_influences.html http://www.gbrmpa.gov.au/corp_site/key_issues/water_quality/faq
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