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| USGS Coral Microbial-Ecology Studies: |
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| Global Climate Change - Microbial Communities as a Diagnostic Tool? |
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Scientists and reef managers are concerned about coral reef systems being affected by global change and need to understand the processes that control their resilience. This large, integrated project involves collaboration between the USGS, the University of Hawaii, the Florida Institute of Technology, the Wildlife Conservation Society, and the National Park Service. Studies are underway in the National Park of American Samoa to determine the internal and external factors that increase the ability of a wide variety of corals to resist environmental stress. The shallow lagoon there contains species of Acropora and Pocillopora, corals ordinarily prone to bleaching (expelling their symbionts) at high temperatures. External factors include changes in water temperature, ultraviolet (UV) radiation, dissolved oxygen, and water motion. Internal factors being investigated include genetic diversity of algal symbionts and the associated microbial communities. Because changes in the coral-associated bacterial communities echo changes in the health of the coral, bacteria are at minimum atuned to their host's metabolism and may play an active role in maintaining the overall health of the coral.
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Left: Pocillopora eydouxi is one of the coral species being monitored for microbial-community changes in Ofu Lagoon, American Samoa. Photo credit: Virginia Garrison, USGS. [larger version] |
The microbial-ecology portion of this
project seeks to answer the following
questions:
- Does the coral-associated bacterial community shift on a seasonal basis? We are using molecular methods to analyze and compare "fingerprints" of the total bacterial community quarterly for one year.
- If the microbial community does
change, do the changes correlate to physical changes like temperature, water
flow, amount of UV, or other extrinsic
factors? That is, are the changes in the
microbial community indicators of certain
types of stress?
- Can changes in the microbial community
be used as "early warnings" of
bleaching or disease? A few studies have
shown that coral-associated bacterial communities
change when the coral bleaches
or becomes infected. Maybe that shift is becomes infected. Maybe that shift is
detectable before the macroscopic signs of
distress are apparent in the coral.
- If microbes can be used as a diagnostic
tool, can the samples be non-invasive,
meaning only the mucus layer is sampled,
not the coral tissue? There are different
microbes in the thin layer of mucus covering
corals and inside the coral tissue. If
the microbial community in the mucus is
responsive enough to the coral's metabolism,
we may be able to test the mucus
alone. Over the course of the larger study,
corals under different stress conditions on
the reef will be evaluated for acclimatization,
adaptation, and (or) susceptibility to
disease. The results of these investigations
may play an important role in choosing the
most effective Marine Protected Areas to
mitigate the effects of global warming on
coral communities.
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Above Left: An aerial view of the Ofu lagoon, part of the National Park of American Samoa. Photo credit: Christina Kellogg, USGS. [larger version]
Above Right: Acropora gemmifera is one of four coral species being monitored as part of this study. Photo credit: Virginia Garrison, USGS. [larger version] |
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Above Left: Ofu lagoon's underwater landscape is heavily populated by massive Porites colonies. Photo credit: Christina Kellogg, USGS. [larger version]
Above Right: A view of Ofu's lagoon from the beach is practically a postcard from the South Pacific! Photo credit: Christina Kellogg, USGS
. [larger version] |
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Above Left: Pocillopora damicornis is very susceptible to bleaching at high temperatures and is particularly important to the study. Photo credit: Virginia Garrison, USGS. [larger version]
Above Right: An underwater panorama featuring a Porites sp. and Pocillopora eydouxi. Photo credit: Christina Kellogg, USGS. [larger version] |
continue to Discovering Archaea Associated with Corals
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