Major concerns for the world’s reefs

Reef and Ocean Ecology Laboratory Major concerns for the world’s reefs

Coral reefs

Overfishing – a problem in tropical waters worldwide

Eutrophication –an excess of nutrients in waters that are clear and naturally low in nutrients; nutrients that may cause excessive growth of algae that kill corals. The death of corals and excessive growth of algae can affect most organisms associated with reefs

Coral bleaching and global warming – coral bleaching has affected reefs in all tropical oceans of the world. It is argued by some that the frequency of bleaching is increasing as a result of global warming.

Crown-of-thorns starfish (COTS) – these voracious starfish consume live coral. Outbreaks of COTS can decimate corals on a reef, but the reefs generally recover (in 5-10 years). The outbreaks have most likely happened for millennia (though some argue that man’s activities have exacerbated outbreaks). Resorts on the Great Barrier Reef often try to control numbers by killing starfish.

Pollution – through oil spills and diversity of pollutants through run off (e.g., fertilizers, industrial waste, sewage)

Development – covering reefs during land reclamation and increased sediment loads to reefs nearby

Introduced species – exotic species can be introduced through ship's ballast and by hitching rides on the sides of ships and smaller vessels. Some of these organisms can have a great impact on the local fauna.

Rocky reefs

Climate change – climate change may cause great changes in the distribution and survival of temperate plants and animals

Overfishing – as for coral reefs a problem worldwide

Pollution – through oil spills and a diversity of pollutants through run off (e.g., fertilizers, boat antifoul, industrial waste, sewage)

Development – covering reefs during land reclamation and increased sediment loads to reefs nearby

Introduced species – exotic species can be introduced through ship's ballast and by hitching rides on the sides of ships and smaller vessels. Some of these organisms can have a great impact on the local fauna. Examples in temperate waters include introductions of the Pacific sea star (to Tasmania), crabs (San Francisco Harbor) and the Japanese kelp Undaria to New Zealand.

On natural reefs all over the world a popular management option for protecting reefs to varying degrees is called ‘Marine Protected Areas’.

Artificial reefs

Positive points – enhance fish stocks, increase catch rates of fish, sustain populations of fishes that were not previously found in the area.

Negative points – make fishes more vulnerable to fishers, justification for putting rubbish into the marine environment, change routes of migration, change location of fisheries and alter catch rates in areas where fishes were previously fished

Climate change

Brierly, A.S., Kingsford, M.J. (2009). Impacts of climate change on marine organisms and ecosystems. Current Biology 19:602-614.

Hoegh-Guldberg, O, and Bruno, J F (2010) The Impact of Climate Change on the World’s Marine Ecosystems. Science 328: 1523-1528

Hoegh-Guldberg O, Mumby PJ, Hooten AJ, Steneck RS, Greenfield P, Gomez E, Harvell CD, Sale PF, Edwards AJ, Caldeira K, Knowlton N, Eakin CM, Iglesias-Prieto R, Muthiga N, Bradbury RH, Dubi A, Hatziolos ME (2007) Coral reefs under rapid climate change and ocean acidification. Science 318: 1737-1742

Pilkey, O.H., and R. Young, 2009, The Rising Sea: Island Press, Washington, D.C., 203 p. ISBN 978-1597261913