I’m doing a group assignment on applying the concept of system the issue of coral bleach of Great Barrier Reef in Australia. I’m responsible for my part of explaining a causal loop diagram to the environmental process of coral bleach. The diagram I have already drawn and included below. My part is around 4-500 words. I’m expecting to see some system thinking in my part with at least 3 references. The tricky part is this assignment is not only an assignment for the environmental issue. It is about a sustainability issue. Overall, I would like to see a good explanation for my causal loop. I have attach some useful links about the issue which might be useful for the explanation. Ps, this is an issue for Great Barrier Reef, don’t talk about coral bleach in America or anywhere else.
Coral bleaching is a marine process that occurs when water temperatures become warm. Warm temperatures in the water cause the coral to expel algae known as (zooxanthellae) that are found in its tissues. This process causes the coral to turn entirely white. Any changes in conditions such as light, or nutrients will also cause coral to bleach because of the expulsion of the symbiotic algae.
Coral bleaching of The Great Barrier Reef has happened before in the past. In 1998, roughly 50% of reefs on The Great Barrier Reef were affected by bleaching, and the sea temperatures were very high during this period (Côté & Reynolds, 2006). In 2002, there was more severe bleaching, roughly 60% of the reefs.
Many other factors affect the growth, or lack thereof, of coral reefs apart from water temperatures alone (Hutchings & Hoegh-Guldberg, 2008). We will see this in the interpretation of the loop diagram.
Corals are the backbone of The Great Barrier Reef ecosystem, and they are highly vulnerable to the potential effects of climate change.
According to the loop diagram, global warming is a critical determinant for coral bleaching. An increase in global temperatures will cause a subsequent rise in ocean temperatures too. When temperatures in the sea rise, the zooxanthellae are expelled by the coral due to the thermal stress. The zooxanthellae are responsible for providing 95% of the nutrition required by the coral as well as giving the coral its distinct coloration. The decrease in the number of zooxanthellae causes the rate of photosynthesis to go down as well as the color of the reef. It is the phenomenon known as coral bleach.
When the temperatures of the ocean stabilize and come back to normal levels, the zooxanthellae population shows an increase on the surface of the coral due to the conducive environment in the cooler waters.
When bleaching occurs, zooxanthellae are significantly reduced from the surface of the coral (“Climate change impacts on corals – GBRMPA,” 2016). The lack of zooxanthellae means that the rate of photosynthesis is very low. Photosynthesis is the process by which plants make food by absorbing carbon dioxide. When photosynthesis is low, carbon dioxide is not absorbed by the coral. The excess carbon dioxide is expelled into the ocean, and it builds up with time. When the carbon dioxide levels in the water are very high, the excess is emitted into the surface leading to a build-up. Increased levels of carbon dioxide on the surface leads to global warming.
Global warming does not only cause ocean temperatures to rise but also accelerates acidification. When ocean acidification occurs, the ability of the coral reef to build a strong skeleton is substantially reduced (“Climate change impacts on corals – GBRMPA,” 2016). The result is weaker coral structures that can hardly withstand the physical forces of nature such as storms and massive waves. The ability to withstand stress and disease is reduced and hence most of the coral dies. When there is no coral, there are no zooxanthellae since their relationship is symbiotic.
The issue of bleaching on The Great
Barrier Reef happens due to changes in the water temperature that result from
global warming (Côté & Reynolds, 2006). On the other hand, if the growth
and reproduction of coral reef are encouraged, there will be secondary carbon
dioxide emissions since most will be used by the zooxanthellae. Lower emissions
mean minor contribution to global warming.
Côté, I. M., & Reynolds, J. D. (2006). Coral reef conservation. Cambridge [u.a.: Cambridge University Press.
Hutchings, P. A., Kingsford, M., & Hoegh-Guldberg, O. (2008). The Great Barrier Reef: Biology, Environment, and Management. Collingwood, Australia: CSIRO Pub.
Climate change impacts on corals – GBRMPA. (2016). Gbrmpa.gov.au. Retrieved 4 October 2016, from http://www.gbrmpa.gov.au/managing-the-reef/threats-to-the-reef/climate-change/what-does-this-mean-for-species/corals