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What Is the Greatest Threat to Australia's Great Barrier Reef?

Bell, P.R.F., Elmetri, I. and Lapointe, B.E. 2014. Evidence of large-scale chronic eutrophication in the Great Barrier Reef: Quantification of chlorophyll a thresholds for sustaining coral reef communities. Ambio 43: 361-376.
In a paper published in AMBIO - a journal of the Royal Swedish Academy of Sciences - Bell et al. (2014) note that long-term monitoring data show hard coral cover on Australia's Great Barrier Reef (GBR) has declined by more than 70% over the past century. And they report that "although authorities and many marine scientists were in denial for many years, it is now widely accepted that this reduction is largely attributable to the chronic state of eutrophication that exists throughout most of the GBR." More specifically, the three researchers say that "the principal proximate causes of the loss of hermatypic corals have been attributed to storm damage, coral bleaching events, widespread growth of corallivores (e.g., crown-of-thorns starfish, COTS), and coral skeletal diseases (CSDs)," a number of which have been identified in the GBR, including Black Band Disease, Brown Band syndrome, White Syndrome, Atramentous Necrosis, Skeletal Eroding Band and Pigmented Spots on Porites, as revealed by assessments of the situation made by Willis et al. (2004), Boyett (2006) and Haapkyla et al. (2011).

In further discussion of the subject, Bell et al. write "it is now widely accepted that the lack of recovery of the reefs and the proliferation of COTS are largely attributable to eutrophication," while also reporting "evidence is emerging that CSDs and coral bleaching are also promoted by eutrophication," much of which is due to "increased loads of nutrients exported via discharges from coastal developments."

Taken together, these findings suggest that it is local water pollution that is the primary instigating force that has led to the destruction of nearly three-quarters of the GBR's corals over the past century. The historical increase in the atmosphere's CO2 concentration has had next to nothing to do with it.

Additional References
Boyett, H.V. 2006. The ecology and microbiology of black band disease and brown band syndrome on the Great Barrier Reef. MSc Thesis. James Cook University, Townsville, Australia.

Haapkyla, J., Unsworth, R.K.F., Flavell, M. , Bourne, D.G., Schaffelke, B. and Willis, B.L. 2011. Seasonal rainfall and runoff promote coral disease on an inshore reef. PLOS ONE 6: e16893.

Willis, B.L., Page, C.A. and Dinsdale, E.A. 2004. Coral disease on the Great Barrier Reef. In: Rosenberg, E. and Loya, Y. (Eds.). Coral Health and Disease, Springer, Berlin, Germany, pp. 69-104.

Archived 1 July 2014