[Coral-List] Chronic nutrient enrichment increases prevalence and severity of coral disease and bleaching

Rebecca rvegathurber at gmail.com
Wed Nov 27 10:50:20 EST 2013

 No we treated whole patches of reef not individual corals. The corals we assessed for disease and bleaching we within and beyond our treatment areas. We examined all corals greater than 5cm in size with a 5 meter radius of the center of our enrichment which was 3m in radius. We suggest in the paper that the effect may have been larger if we only surveyed corals within our treatments. Does this make sense. - becky 

> On Nov 27, 2013, at 7:03 AM, Dennis Hubbard <dennis.hubbard at oberlin.edu> wrote:
> Rebecca:
> Thanks for bringing your paper to our attention. I've only had a chance to scan it, but I have one question regarding recovery. I assume that your nutrient treatment was to selective corals within a community. Therefore, when the stresses are removed, there are no other diseased colonies nearby (except for other treatments). If I am correct, do you have a sense of what this experiment would look like if you negatively treated the entire reef and then took nutrients away? It has been my experience that reef responses are decidedly more non-linear than those for individual colonies or individuals - and that once things are perturbed simply backing the stress off a bit does not reverse the impacts, i.e., it is cheaper to not break it than to have to fix it. Do you have a sense that this may not be the case with nutrients?
> Dennis
>> On Tue, Nov 26, 2013 at 4:30 PM, Rebecca Vega Thurber <rvegathurber at gmail..com> wrote:
>> Hello Coral List,
>>    I would like to direct you all to our newest study published in the
>> journal *Global Change Biology*. This study concerns the effects of
>> inorganic nutrients on coral disease and bleaching. In summary, we found
>> that chronic nutrient (inorganic N + P) enrichment increased the prevalence
>> and severity of coral disease and bleaching. However, we also showed that
>> within 10 months after nutrient enrichment was removed the coral community
>> recovered. For more information, below are the abstract, a link to the
>> work, and to our current press release on the topic. -Becky
>> http://www.eurekalert.org/pub_releases/2013-11/osu-lss111413.php
>> http://onlinelibrary.wiley.com/doi/10.1111/gcb.12450/abstract
>> Abstract
>> Nutrient loading is one of the strongest drivers of marine habitat
>> degradation. Yet, the link between nutrients and disease epizootics in
>> marine organisms is often tenuous and supported only by correlative data.
>> Here, we present experimental evidence that chronic nutrient exposure leads
>> to increases in both disease prevalence and severity and coral bleaching in
>> scleractinian corals, the major habitat-forming organisms in tropical
>> reefs. Over 3 years, from June 2009 to June 2012, we continuously exposed
>> areas of a coral reef to elevated levels of nitrogen and phosphorus. At the
>> termination of the enrichment, we surveyed over 1200 scleractinian corals
>> for signs of disease or bleaching. *Siderastrea siderea* corals within
>> enrichment plots had a twofold increase in both the prevalence and severity
>> of disease compared with corals in unenriched control plots. In addition,
>> elevated nutrient loading increased coral bleaching; *Agaricia* spp. of
>> corals exposed to nutrients suffered a 3.5-fold increase in bleaching
>> frequency relative to control corals, providing empirical support for a
>> hypothesized link between nutrient loading and bleaching-induced coral
>> declines. However, 1 year later, after nutrient enrichment had been
>> terminated for 10 months, there were no differences in coral disease or
>> coral bleaching prevalence between the previously enriched and control
>> treatments. Given that our experimental enrichments were well within the
>> ranges of ambient nutrient concentrations found on many degraded reefs
>> worldwide, these data provide strong empirical support to the idea that
>> coastal nutrient loading is one of the major factors contributing to the
>> increasing levels of both coral disease and coral bleaching. Yet, these
>> data also suggest that simple improvements to water quality may be an
>> effective way to mitigate some coral disease epizootics and the
>> corresponding loss of coral cover in the future.
>> --
>> Dr. Rebecca Vega Thurber
>> Assistant Professor of Microbiology
>> Oregon State University
>> 454 Nash Hall
>> Corvallis OR  97331-3804, U.S.A
>> 541-737-1851 (office) 541-737-0496 (FAX)
>> rvegathurber at gmail.com;Rebecca.Vega-Thurber at oregonstate.edu<Rebecca.Vega.Thurber at oregonstate.edu>
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> -- 
> Dennis Hubbard 
> Chair, Dept of Geology-Oberlin College Oberlin OH 44074 
> (440) 775-8346
>  "When you get on the wrong train.... every stop is the wrong stop"
>  Benjamin Stein: "Ludes, A Ballad of the Drug and the Dream"

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