2007 (PDF) - Rosenstiel School of Marine and Atmospheric Science ...

Marine Life
‘Nursing’ Coral Fragments
Until recently, branching elkhorn (Acropora palmata) and staghorn
(Acropora cervicornis) corals were among the most abundant reefbuilding
corals in Caribbean and Florida reefs. However, in the
last few decades a drastic regional decline of this genus has been recorded
due mainly to elevated temperatures, coral diseases, and the
impact of hurricanes. This region-wide decline, which has resulted
in losses of up to 95 percent of colonies at several locations, has
prompted the listing of these species as “threatened” under the U.S.
Endangered Species Act in 2006.
In response to the need for localized efforts to protect and recover
surviving coral populations, Dr. Diego Lirman and graduate student
James Herlan established an underwater
nursery dedicated to the propagation of
the threatened staghorn coral. The underwater
nursery, located in the waters of Biscayne
National Park, is part of a network of
Acropora nurseries established with support
from The Nature Conservancy, NOAA, and
the National Park Service.
Fragment of staghorn
coral demonstrating fast regrowth
between July 2007
and October 2007. Photo
credit: James Herlan and
Diego Lirman
The goals of the coral nursery program are
to develop effective coral fragmentation and
propagation methodologies, and to evaluate
the role of coral genetics on the resilience of
corals to disturbance. Coral nurseries provide
a unique opportunity to learn about
coral growth and survivorship, as well as
how to stabilize corals damaged by physical
disturbances.
A total of 250 staghorn coral fragments
have been collected and placed on cement
platforms where they are individually measured
at monthly intervals to assess growth
and mortality patterns. The fast growth
rate of these species -- up to 15 cm per
year -- makes them ideal candidates for reef restoration programs.
It is expected that the staghorn fragments kept in the University of
Miami’s nursery will provide an expanding coral stock to be used
for reef restoration.
Coral Cooldown
Scientists have known that hurricanes reduce sea-surface temperatures
upon passage. In fact, Rosenstiel School Professor Peter
Glynn was the first to put forth the hypothesis that thermally
stressed corals might benefit from cooling due to proximal hurricane
passage. But until
now, all evidence for this
phenomenon has been
anecdotal or qualitative,
or researchers have
chosen to focus solely
on the damaging effects
of hurricanes on coral
reef habitats. As seemingly
sensitive animals,
corals may seem unlikely
Pacific staghorn coral (Acropora sp.) Photo
credit: Andrew Baker
candidates to benefit from strong wind and wave conditions, but
as Rosenstiel School graduate student Derek Manzello and a team
from the National Oceanic and Atmospheric Administration
(NOAA) discovered, the intense cooling effect tropical cyclones
and storm force winds have on the waters of the Atlantic are giving
corals a much-needed boost to encourage repopulation.
Hurricane development is dependent on warm sea surface temperatures
and often closely linked with widespread coral bleaching
events. Corals survive mainly in shallow water where photosynthetic
algae reside symbiotically within the coral’s transparent tissue
using the sun’s energy to convert it into food for the coral. Even the
slightest changes in water temperature can cause widespread bleaching,
forcing the tiny food-producing algae to be expelled from the
coral tissue.
Milne Bay, Papua New Guinea. Photo credit: Michael Schmale
In a study published in the July 2007 issue of the Proceedings of
the National Academy of Sciences, the team, organized by Manzello,
documented the potential benefits of hurricane and tropical
storm weather on bleached coral reefs. Researchers showed
evidence suggesting that by circulating colder deep ocean waters
toward the surface, high winds surrounding hurricanes and tropical
storm events cooled surface waters enough to promote rapid
recovery of bleached corals stressed by anomalously warm waters
off the Florida coast. The study focused on the magnitude and duration
of sea temperature
cooling after the passage
of hurricanes and tropical
storms near five reef sites
on the Florida Reef Tract
between 1998 and 2005.
Data analyzed from the
2005 Atlantic hurricane
season -- the busiest in
recorded history -- showed
that the area affected by
hurricane cooling is much
Cervicornis polyps. Photo credit: Wade
Cooper
larger than the narrow bands where damage actually occurs to
reefs.
A Marine “Connection”
A special issue of Oceanography published in 2007 features articles
and cover images by faculty,
researchers and staff members
from the Rosenstiel School.
The edition focuses on
marine population connectivity,
a concept described in an
article authored by Rosenstiel
Marine Biology and Fisheries
Division Chair and Maytag
Professor of Ichthyology, Dr.
Robert Cowen, and colleagues
Drs. Glen Gawarkiewicz,
Jesus Pineda and Simon
Thorrold from Woods Hole
Oceanographic Institution
(WHOI), and Cisco Werner
from UNC-Chapel Hill
(UNC-CH).
Larval transport and dispersal play a critical role in marine connectivity,
having important consequences on coastal and nearshore
marine populations as highlighted in an article by Drs. Jesus Pineda
(WHOI), Jonathan Hare (NOAA) and Su Sponaugle (Rosenstiel
School). Modern modeling and computational skills also play a
critical role in studying connectivity. Biological and physical models
are needed to uncover the dynamics at work in our oceans, as is
detailed in a piece by Drs. Cowen and Claire Paris-Limouzy, also
of the Rosenstiel School, in collaboration with Dr. Cisco Werner
(UNC-CH). The article details current model tracking for connectivity,
as well as the direction that needs to be taken in improving
the representation of physical dynamics and the development of
new algorithms. The authors also propose the use of more integrated
models that can help to inform how field experiments may
be designed for greater effectiveness.
Dr. Chris Langdon measures the
vertical extension rate of a coral
sample. Photo credit: Barbra
Gonzalez
Corals & Climate Change
In August 2007, Drs. Chris Langdon and Andrew Baker of the Marine Biology and Fisheries Division inaugurated
a first-of-its-kind laboratory to tackle the global impacts that climate change is having on corals.
The modest lab is the first to maintain corals under precisely controlled temperature and carbon dioxide
conditions, while exposing them to natural light conditions.
Using two Caribbean coral species, Montastraea faveolata (mountainous star coral) and Porites furcata
(finger coral), the team is studying how increasingly acidic oceans, caused by increasing atmospheric
carbon dioxide, can affect corals when accompanied with increasing temperatures. Corals in the laboratory
are being stressed with differing levels of carbon dioxide and temperatures, like those they might
experience in the next 50 to 100 years, to see if skeletal development is affected.
Since the year 1800, nearly 30 percent of total global carbon dioxide emissions have been absorbed
by the ocean. Despite the immensity of the world’s oceans, this accumulation is gradually lowering the
pH of ocean water, making it more acidic and in turn, making it difficult for corals and other
important marine organisms to thrive.
The duo’s experimental studies are simulating scenarios already occurring in the Florida Keys.
The Florida reef tract is the most extensive living coral reef system in the continental United
States. Langdon’s research has shown that a coral’s ability to produce a limestone skeleton
decreases substantially as oceans become more acidic, a conclusion which suggests that these
organisms will grow at a slower rate, or their skeletons will become more fragile (less dense);
a process that can be compared to osteoporosis in humans. As a result, reef structures will
become increasingly brittle and unable to develop extensively as erosion and other factors will
wear them away faster than they can grow.
The Coral Climate Change Lab was made possible through funding from the National Science
Foundation, the Packard Foundation, Conservation International and the Wildlife Conservation
Society.
Bleached coral. Photo credit:
Andrew Baker
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