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

Dennis Hubbard dennis.hubbard at oberlin.edu
Wed Nov 27 12:00:34 EST 2013

Thanks.... and, yes it does. I do have two additional questions. First,
were these patches isolated features that had no access to resources that
might have facilitated their recovery? And two, given recent list-serve
discussions, how did you get permits to stress corals? - sorry to be so
snarky, but I couldn't resist.

Nice study!


On Wed, Nov 27, 2013 at 10:50 AM, Rebecca <rvegathurber at gmail.com> wrote:

> Dennis,
>  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*"

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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