Marine Climate Change Impacts
 
image by M.Edwards

Climate Impacts and Kelp Forest

Kelp forests are marine ecosystems dominated by large brown algae (Phaeophyta). These include the largest alga in the world, Macrocystis pyrifera which can grow 30cm per day under optimum conditions to a maximum of 60m. The forests are considered to be among the most scenic dive sites in the world. Kelp grows along rocky coastlines in cold and temperate nutrient-rich waters at depths of up to 40m. Kelp forests, which are among the most biologically productive habitats in the marine environment are thickest in summer declining during winter storms and high surf though some plants may survive for up to three years. These forests provide a habitat utilized by many species, including marine mammals, fish, other algae, and a vast numbers of invertebrates. Many of the species characteristic of the forests are highly adapted to the conditions provided by the kelps, the keystone species of these ecosystems. Kelps are commercially harvested for alginates, which are used in ice cream and cosmetics.

Climate change may influence kelp forests through the direct effects of temperature, moving the boundaries of the areas where they have the potential to survive. In addition, nutrient inputs necessary for the kelp to thrive may be altered due to changes in the geographical or seasonal distributions of rainfall and upwelling. In kelp forests off southern California, the proportion of cold water fish such as the greenspotted rockfish, have fallen and warm water species like the Garibaldi have increased since the 1970s. Since the 1940s in Tasmania an increase of 1.5 – 2.0°C in minimum water temperature associated with a southward shift in the boundary between the warm East Australian current and the cold, nutrient-rich sub-Antarctic waters has contributed to a decline in the extent of what was once the largest kelp forest in Australia. An increase in the numbers of sea urchins has also contributed to the decline. These are normally passive grazers of algae but graze the kelp when the waters become warmer, as in El Niño events. In the Northern Hemisphere former kelp forests have become 'sea urchin barrens' due to overfishing, removing the predators that would normally control the urchins. Disruption of ecosystems due to climate change may re-inforce the imbalances that have resulted in the overgrazing of the kelps.

Additional information and key links
http://greennature.com/article1074.html
Green Nature
An Introduction to Kelp Forests. (web)
http://www.mbnms-simon.org/sections/kelpForest/overview.php?sec=kf
SIMON
Sanctuary Integrated Monitoring Network. (web)
http://www.climateark.org/articles/reader.asp?linkid=26969
Climate Ark
AUSTRALIA: Giant kelp forests under threat(web)
Key references
Tegner, M.J.; Dayton, P.K.; Edwards, P.B.; Riser, K.L. 1996. Is there evidence for long-term climatic change in
      southern California kelp forests? Reports. California Cooperative Oceanic Fisheries Investigations,
      37, 111-126.
 
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