Shifting Baselines, Local Impacts, and Global Change on Coral Reefs

  • Nancy Knowlton equal contributor mail,

    equal contributor Contributed equally to this work with: Nancy Knowlton, Jeremy B. C Jackson

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  • Jeremy B. C Jackson equal contributor

    equal contributor Contributed equally to this work with: Nancy Knowlton, Jeremy B. C Jackson

  • Published: February 26, 2008
  • DOI: 10.1371/journal.pbio.0060054
  • Published in PLOS Biology

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The intriguing realities of coral reef decline and the prospective conservation approaches

Posted by plosbiology on 07 May 2009 at 22:22 GMT

Author: Niyaz Ahmed
Position: Staff Scientist and Group Leader
Institution: Centre for DNA Fingerprinting and Diagnostics, Hyderabad, India
Submitted Date: March 05, 2008
Published Date: March 6, 2008
This comment was originally posted as a “Reader Response” on the publication date indicated above. All Reader Responses are now available as comments.

In the current scenario of colossal public attention to environmental problems and far reaching consequences of related studies published in open access journals, the science of coral reef ecology seems to have stratified into two major paradigms: 1) coral reef degradation is the outcome of direct human impacts such as overfishing and development and conservation efforts therefore, should focus on these aspects or 2) decline of corals is largely the result of global climate change and microbial ‘pathogens’ and conservation resources should focus on these issues. Obviously these are the two extremes which need to be balanced. This essay (1) together with two companion articles in PLoS ONE (2, 3) indeed denotes that the much needed balancing act has just started.
The authors convey (1, 2) that coral reefs in remote areas with less human inhabitation support thriving of more fishes and commonly have healthier and bountiful corals than reefs in more populated areas. They suggest the need for understanding how local bio-geo-climatic impacts in synergy with global change affect the structure, function, and resilience of coral reef. Their second paper (2) documents the ecology of perhaps the most pristine reefs that exist, and highlight the gradient of various impacts occurring across the chain of islands with increasing human inhabitation. However, the authors focused heavily on an interpretation in which fishing and development cause the decline in coral and altered fish community structure. Although the essay (1) did not elaborate microbial causes of coral degradation, the issue was addressed separately (3) through metagenomics that revealed linkages between human inhabitation/activity and the incidence of unhealthy corals. The observed increase in the abundance of microbes in water columns studied, and assignment of such microbes to potential pathogenic groups as shown are the indicators of a very real potential for coral reef degradation. The data generated in the form of metagenomes and viromes from sea microbial communities are in fact an invaluable resource.
While it is satisfying that praises of these papers clearly outweigh the objections, there exist notable criticisms of the interpretations made out of correlative studies rather than experimental. But thanks to this fact that correlational studies are often the only option when trying to collate bio-geo-climatic patterns. Another criticism could be made of the choice to refer to sets of organisms as 'opportunistic pathogens'; it should not be taken to mean that these organisms are classical pathogens themselves. For example, saprophytic mycobacteria despite their having highly conserved genomic overlaps with major dreaded forms (M. tuberculosis and M. leprae), do not represent seasoned pathogens. The issue behind this difficulty is the rampant genomic fluidity expressing as phenotypic versatility of the microbial players. Finally, this ‘coral-reef package’ (1, 2, 3) is a big leap towards the general understanding of the biology and ecology of reef degradation and their prospective conservation. I believe these efforts (1, 2, 3), although not an ultimate decree on the coral reef ecology should nonetheless serve as an important foundation for future studies.

1) Knowlton N, Jackson JBC (2008). Shifting Baselines, Local Impacts, and Global Change on Coral Reefs. PLoS Biology 6: e54. 2) Sandin SA, Smith JE, Demartini EE, Dinsdale EA, Donner SD, Friedlander AM, Konotchick T, Malay M, Maragos JE, Obura D, Pantos O, Paulay G, Richie M, Rohwer F, Schroeder RE, Walsh S, Jackson JB, Knowlton N, Sala E (2008). Baselines and degradation of coral reefs in the northern line islands. PLoS ONE 3:e1548. 3) Dinsdale EA, Pantos O, Smriga S, Edwards RA, Angly F, Wegley L, Hatay M, Hall D, Brown E, Haynes M, Krause L, Sala E, Sandin SA, Thurber RV, Willis BL, Azam F, Knowlton N, Rohwer F (2008). Microbial ecology of four coral atolls in the northern line islands. PLoS ONE 3:e1584.

No competing interests declared.