11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 16: Ecosystem Assessment and Monitoring of Coral Reefs - New Technologies and Approaches
16-13
Landscape Mosaics Of Coral Reefs: A New Survey Technology For Mapping And
Monitoring Reef Condition
Brooke GINTERT* 1 , Nuno GRACIAS 2 , Diego LIRMAN 1 , Arthur GLEASON 1 , Philip
KRAMER 3 , R. Pamela REID 1
1 University of Miami, Rosenstiel School of Marine and Atmospheric Science, Miami,
FL, 2 Department of Electronics, Computer Engineering and Automatics, Universitat de
Girona, Girona, Spain, 3 The Nature Conservancy, Summerland Key, FL
Efficient survey methodologies that provide comprehensive assessment of reef condition
are fundamental to coral reef monitoring. Current state-of-the-art techniques in coral reef
assessment rely on highly trained scientific divers to extract indices of reef health (e.g.
substrate cover, species richness, coral size, coral mortality, and coral recruitment).
Landscape video mosaics are an innovative survey technology that provide large scale
(up to 400m2), spatially accurate, high resolution images of the reef benthos without
extensive survey times or a need for scientific divers. Based on diver-acquired video of
the reef benthos and novel mosaicing algorithms, landscape mosaics have been used in
the laboratory to extract indices of benthic cover, coral colony size, and colony health
that compare favorably with diver surveys. The spatially explicit images allow users to
make accurate benthic measurements (such as colony area and diameter, as well as
distance relationships for spatial analysis) directly from mosaic products. Repeated
mosaic surveys of the same area are easily referenced for change detection analysis and
provide an image-based monitoring capability that can survey hundreds of coral colonies
over time without the use of in situ tagging and underwater relocation. In addition,
landscape mosaics provide a large-scale visual permanent record of the state-of-the-reef
at the time of collection that is accessible to both the scientific community and general
public. To date this technology has been used to detect and monitor changes in reefs
responding to hurricanes, ship groundings, and mass bleaching events.
16-14
Imaging Coral Community Structure At High Resolution Over Large Areas On The
Reef Terraces Of The Chagos Archipelago
John TURNER* 1 , Robert GIBBS 1
1 School of Ocean Sciences, Bangor University, Bangor, United Kingdom
A new technique is described to image large areas of coral reef at high resolution to
analyse coral community structure and improve public awareness of reef environments.
A major problem encountered in mapping any benthic community is obtaining an optical
image that covers sufficient area at high resolution to identify species and investigate
spatial relationships. Such large images are difficult to obtain in turbid waters (hence
acoustic methods are used) and also in clear waters, where either the water depth is so
shallow that camera to subject distance is short, or in deeper water where distance is long
but resolution poor. Previous research on reef biotope mapping has identified the need to
formulate an image within a 20-30 m2 pixel, so typical of satellite remote sensing
imagery used in wider scale mapping. A diver-operated rig was designed to carry a high
resolution digital underwater video camera and lighting, such that accurate circular tracks
of reef could be sequentially imaged about a central point. Each ring increased in
diameter to overlap the preceding circle, ensuring 100 % cover. The technique was
deployed at 5 sites between 10 and 20 m depth on different reef slopes around 4 atolls of
the Chagos archipelago. Software was written to mosaic 3,570 video images recorded
across 21 rings to create a 76 square metre image of each site, resulting in a resolution of
2 mm at 1m distance from the reef. Images of the different sites were analysed using
MapInfo GIS to assess spatial relationships between coral colonies, and to examine
recovery at colony scale on a previously bleached reef. The images are being used for
monitoring and conservation policy formulation. Sections of images will be reproduced at
life-size in the new London Zoo Chagos reef exhibit, to assist in the public understanding
of reefs.
16-15
Bioeroding Sponges Need To Be Monitored
Christine SCHÖNBERG* 1 , Katherine E. HOLMES 2
1 Dept. of Animal Biodiversity and Evolution, Carl von Ossietzky University, Faculty 5, Biology
and Environmental Sciences, Oldenburg, Germany, 2 Center for Biodiversity and Conservation,
American Museum of Natural History, New York, New York, NY
Bioeroding sponges are important in the balance of coral reef construction and destruction. Due
to changes in environmental conditions, these sponges can become epidemic and have
occasionally been recognised for their value as bioindicators. Recent studies revealed increases
in bioeroding sponge abundances in the Caribbean and on the Australian Great Barrier Reef,
which was largely explained with deteriourating conditions or disturbance events that led to an
increased availability of suitable substrate for the settlement of bioeroders. The sponges appear
to be hardier than corals, even if they are zooxanthellate. We propose to incorporate the most
common species of bioeroding sponges into long-term monitoring projects. Species of the
‘Cliona viridis’ complex are thought to be most suitable for this, because they occur at all study
sites, but species such as the Caribbean Cliona delitrix should also be considered. If the
procedure is kept simple (see proposal on poster), replicate studies can be conducted at very
different sites and in consecutive approaches, eventually leading to a sound database on the
leading endolithic agents of warm water bioerosion.
16-16
Solar Radiation Dosimetry In Florida Coral Reefs Determined From Remote Sensed,
Modeled, And In Situ Data
Mace BARRON* 1 , Deborah VIVIAN 1 , Susan YEE 1 , Debbie SANTAVY 1
1 U.S. Environmental Protection Agency, Gulf Ecology Division, Gulf Breeze, FL
Solar irradiance has been increasingly recognized as an important determinant of bleaching in
coral reefs, but measurements of solar radiation exposure within coral reefs have been relatively
limited. Solar radiation dosimetry within multiple coral reef areas of South Florida was
assessed using remote sensed, modeled, and measured values during a minor bleaching event
(August 2005). Coral reefs in the Dry Tortugas and Upper Keys had similar diffuse down
welling attenuation coefficients (Kd, m-1), but Kd values were significantly greater in the
Middle and Lower Keys. Mean one percent attenuation depths varied by reef region for
ultraviolet B (UVB; 9.7 to 20 m), ultraviolet A (UVA; 22 to 40 m) and visible (27 to 43 m)
solar radiation. Solar irradiances determined from remote sensed surface intensity and Kd were
significantly correlated with measured values, but were generally over estimated at the depth of
corals. Solar irradiances modeled using an atmospheric radiative transfer model parameterized
with site specific approximations of cloud cover showed close agreement with measured values.
Estimated daily doses (W*hr/m2) of UVB (0.01-19), UVA (2-360) and visible (29-1653) solar
radiation varied with coral depth (2 to 24 m) and meteorological conditions. These results
indicate large variation in solar radiation dosimetry within coral reefs that may be estimated
with reasonable accuracy using regional Kd measurements and radiative transfer modeling.
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