11th ICRS Abstract book - Nova Southeastern University

18-45
New Insights Into The Exposure And Sensitivity Of Coral Reefs To Ocean Warming
Patrick BOYLAN* 1 , Joanie KLEYPAS 1
1 Institute for the Study of Society and Environment, National Center for Atmospheric
Research, Boulder, CO
Increases in coral bleaching events over the past 20 years are correlated with increases in
sea surface temperature (SST). While SSTs have increased everywhere in the tropics,
and coral bleaching events have occurred in all coral reef provinces, the frequency and
intensity of coral bleaching events have varied considerably from region to region.
Unless these patterns are random, we can derive useful information about why some reefs
have been less vulnerable to increasing SST, and use this information to guide
conservation efforts. Coral reef vulnerability to bleaching is a function of exposure to
some stress (elevated SST), sensitivity to that stress, and the capacity of the reef to adapt
to the exposure. To better characterize differences in coral reef vulnerability to increases
in SST, we analyze temperature and coral bleaching records from reefs in select regions
for differences in exposure (nature of the SST increase at multiple temporal scales) and
sensitivity to the SST increase. These refined relationships between temperature and
bleaching allow us to create region-based bleaching thresholds that allow better
predictions of future bleaching events.
18-46
Mesophotic Reefs Of The Puerto Rican Shelf: Physical Processes, Resistance To
Climate Change, Cryptic Mortality, And Future Trajectories
Tyler SMITH* 1 , Richard NEMETH 1 , Jeremiah BLONDEAU 1 , Jacqulyn CALNAN 1 ,
Elizabeth KADISON 1
1 Center for Marine and Environmental Studies, University of the Virgin Islands, St.
Thomas, Virgin Islands (U.S.)
Mesophotic coral reefs (MPR) are some of the least studied and most poorly understood
reefs systems in the world. Available data for the Caribbean and extrapolation from
bathymetric data suggest that these environments are extensive between 30 and 100 m.
MPR south of St. Thomas (US Virgin Islands) have been under investigation for the last
five years. A study to understand the resources within a full no-take marine reserve, the
Red Hind Marine Conservation District (MCD, 41 km 2 ), using technical SCUBA and
closed circuit rebreather, has revealed 25 km 2 of coral reefs, and expanded estimates of
coral reef structure from multi-beam/side-scan data by ~110%. Surveys show that coral
cover is unusually high for modern Caribbean reefs, and often surpasses 40%.
Furthermore, a community of commercially important fish species, including rare high
trophic level carnivores, is both abundant and in large biomass. Both exploratory dives
and inspection of regional bathymetry strongly suggest that similar MPR are extant in a
large (300 km 2 +) region near St. Thomas, a fact that has not been previously appreciated.
Studies on the health of these coral reefs have revealed important information on their
potential to withstand climate related thermal disturbance. During a mass bleaching
event (2005) MPR suffered relatively little bleaching compared to all shallow reefs (5%
bleaching prevalence vs. 70%), but still experienced high mortality (27% cover lost vs.
36%). Surveys in 2007 revealed that within the matrix of the MCD a large (8 km 2 ),
spatially explicit cryptic coral mortality event occurred (42% of sites at 45% prevalence),
that was decoupled from trends in shallow reefs. The spatial extent of mortality suggests
a large common driver. Clearly, further ecological, geological and oceanographic
investigations are needed to fully understand the role that MPR play within the
interconnected reefs systems of the Caribbean and the world.
Oral Mini-Symposium 18: Reef Status and Trends
18-47
Recurrent Large-Scale Disturbances, Recovery Trajectories, And Resilience Of Coral
Assemblages On A Coral Reef in The South-Central Pacific
Mehdi ADJEROUD* 1 , François MICHONNEAU 1 , Peter J. EDMUNDS 2 , Yannick
CHANCERELLE 3 , Lucie PENIN 1 , Jérémie VIDAL-DUPIOL 1 , Bernard SALVAT 1 , René
GALZIN 1
1 Biologie et Ecologie Tropicale et Méditerranéenne, Université de Perpignan, Ecole Pratique
des Hautes Etudes, UMR 5244 CNRS-EPHE-UPVD, Perpignan, France, 2 Department of
Biology, California State University, Northridge, CA, 3 Centre de Recherches Insulaires et
Observatoire de l'Environnement, Moorea, French Polynesia
Temporal variability in coral community structure on the outer reef at Tiahura, Moorea (French
Polynesia) was investigated between 1991 and 2006 to test for the effects of major disturbances.
During the study, the reef was impacted by one cyclone (1991) and four bleaching events (1991,
1994, 2002, 2003). The cyclone and bleaching of 1991 had the greatest impact, and caused a
rapid decline in coral cover from 51.0 % in 1991 to 24.2 % in 1992. In contrast, the three
successive bleaching events had little effect on coral cover, even though the thermal anomalies
causing these events were similar to the conditions leading to the 1991 bleaching. By 2001,
coral cover returned to the 'pre-disturbance' levels of early 1991, but the trajectories of change
differed among genera. Acropora was affected by the disturbances of 1991, but subsequently
showed a high rate of recovery; Montipora was affected by most disturbances and showed no
sign of recovery; Pocillopora was affected by the disturbances of 1991, and showed a partial
recovery by 1995; and Porites was not affected by any disturbances, but increased in cover
throughout the study. Our results demonstrate that large-scale disturbances are not always
associated with a phase-shift from coral- to algal-dominated communities, but instead show that
coral cover can recover rapidly after dramatic declines. To our knowledge, our study is the first
contemporary analysis to demonstrate rapid recovery of coral cover, despite the effects of
ongoing disturbances, although importantly this trend was achieved through a shift in the
relative abundance of coral genera. Thus, coral communities at Tiahura appear to be
characterized by ecological resilience to disturbances in terms of coral cover, but fragility in
terms of generic composition.
18-48
Multiple States Of Coral Reefs In Human Shaped Environments
Albert NORSTRÖM* 1,2 , Magnus NYSTRÖM 1,2 , Jerker LOKRANTZ 1,2 , Carl FOLKE 2,3
1 Systems Ecology, Stockholm University, Stockholm, Sweden, 2 Stockholm Resilience Centre,
Stockholm, Sweden, 3 The Beijer Institute, Royal Swedish Academy of Sciences, Stockholm,
Sweden
Coral ecosystems worldwide are facing large-scale degradation that is often associated with
phase shifts: modifications of their functions and feedback mechanisms to a new regime. The
most well documented type of phase shift on coral reefs involves a decrease in the abundance of
scleractinians coupled with an increased abundance of large, fleshy macroalgae. However, there
are numerous reports of coral reefs becoming dominated by other organisms following a
disturbance but they have largely been ignored in coral phase shift literature. An ISI search with
the keywords “phase shifts AND coral” revealed that only 2 out of 152 research articles
mention other possible regimes. We search the literature for evidence of transitions from coral
dominance to community assemblages other than macroalgae and argue that four other types of
phase shifts seem to occur on coral ecosystems: coral to soft coral, coral to corallimorpharian,
coral to sponge and coral to urchin barrens. We place our findings in the context of the current
phase shift discourse, and discuss whether these transitions constitute alternative states, as
opposed to transient alterations in local community structure. We assess processes and
mechanisms behind their manifestation, emphasizing human induced drivers. We conclude that
the mix of different human-induced drivers (like excess nutrient runoff, sedimentation,
overexploitation) in different coastal and marine contexts create attractors of reef development
that lead to the existence of a multiple set of alternative regimes.
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