11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 10: Ecological Processes on Today's Reef Ecosystems
10-33
Testing A Novel Functional Group Approach For Caribbean Hard Corals By
Comparing Their Rank Abundances Across The Florida Reef Tract Also Refutes
The Unified Neutral Theory
Thaddeus MURDOCH* 1,2 , Richard ARONSON 3,4
1 BREAM: Bermuda Reef Ecosystem Assessment and Mapping Programme, Bermuda
Zoological Society, Flatts Village, Bermuda, 2 Murdoch Marine Environmental
Consultant Services Ltd., Paget, Bermuda, 3 Marine Science, Dauphin Island Sea Lab,
Dauphin Island, AL, 4 Marine Science, University of South Alabama, Mobile, Alabama
A functional group approach can be used to categorize organisms by adaptive traits
instead of phylogeny. One such approach, the "Adaptive Strategies Theory" (AST),
originally developed for terrestrial plants, was modified to apply to reef corals. The coral
AST predicts the assemblage structure of Caribbean reef corals from fundamental habitat
characteristics. Accordingly, species and functional groups of coral differ in dominance
in a predictable manner, depending upon the levels of resource and disturbance of the
habitat they are in. Alternatively, the unified neutral theory (UNT) proposes that all coral
species are functionally equivalent, and the ranking of any species will be random from
site to site, regardless of the environmental conditions of the reef habitat.
Examination of patterns of rank abundance across 10 transects on each of 20 sites located
across the Florida Reef Tract, encompassing a quantified gradient of disturbance,
determined that eleven species out of a pool of at least 36 species were highly
significantly more abundant than the rest. These 11 abundant species belonged to three
different functional groups, and, for these species, the species members of each
functional group were statistically more similar in rank and site affinity than were species
belonging to other functional groups. The rarer species, alternately, showed rankabundances
and distributions across transects that were without apparent pattern. The
functional-group differences in rank-abundance were also highly non-random. The
dominance patterns of each functional group relative to the level of disturbance measured
on each of the 200 transects fit the predictions of the newly proposed coral AST. These
results indicate certain traits indicate functional responses in corals, that all coral species
are not equivalent in their functional responses. As a consequence, the fundamental
hypothesis of the UNT that all species of coral are functionally identical is also refuted.
10-34
Spatial Dynamics Of Scleractinian Coral Populations in The Florida Keys
Dione SWANSON* 1 , Mark CHIAPPONE 2 , Steven MILLER 2 , Leanne RUTTEN 2 ,
Steven G. SMITH 1 , Jerald AULT 1
1 Marine Biology and Fisheries, University of Miami, Rosenstiel School of Marine and
Atmospheric Science, Miami, FL, 2 Center for Marine Science, University of North
Carolina-Wilmington, Key Largo, FL
Natural and anthropogenic disturbances have caused major changes in reef species
composition worldwide during the past few decades resulting in significant decreases in
coral cover and abundance. Traditional monitoring metrics such as percent coral cover
and species richness have not provided an avenue to address the processes that contribute
to these changes. Knowledge of population dynamics of corals is required to address
questions concerning the sustainability of coral reefs. Colony density and size structure
provide information on fundamental demographic rate processes (colony recruitment,
growth, mortality, and survivorship) as well as the net outcome of these processes. To
address coral population structure and recruitment in the Florida Keys, adult (colonies >4
cm in diameter) and juvenile (colonies < 4 cm diameter) abundance were estimated using
a two-stage stratified random sampling survey design. Primary sample units (sites) were
allocated among thirteen reef-types (habitat strata) within the Florida Keys reef tract
(survey domain). Design features included strategic sampling that produced relatively
precise population estimates and the ability to statistically compare multiple sites within
and among benthic habitats over relatively broad spatial scales. From 1999-2006, surveys
of coral colonies were conducted at sites which spanned the range of habitats along
Florida Keys reef tract through the Dry Tortugas. Quantitative analyses addressed coral
population structure in three categories: descriptive and species size analysis, coralhabitat
regression analysis, and habitat use analysis. These results help to discern the
influence of habitat type and location on demographic processes that regulate coral
population size structure and facilitate inferences concerning the consequences of the
current coral population distributions in the Florida Keys.
10-35
Partial Mortality Of Caribbean Corals: Modes, Trends, And Consequences
Jessica GILNER* 1 , Robert VAN WOESIK 2
1 Biological Sciences, Florida Institute of Technology, Melbourne Beach, FL, 2 Biological
Sciences, Florida Institute of Technology, Melbourne, FL
Partial mortality leads to changes in life-history strategies and energetics, which can jeopardize
colony fitness and survival. Increases in partial mortality of coral colonies are arguably the
primary mechanism of declines in coral cover in the Caribbean. In 2005, an intense coral
bleaching event was recorded on reefs at Puerto-Morelos, Mexico. We applied a hierarchical
sampling design, using randomly selected 75 x 25 m stations as our effective sampling units
nested within five sites spaced 1-2 km apart. Re-randomized 50 x 1 m belt transects were used
to sample partial morality of coral colonies during and after the bleaching event. In 2006, three
4 x 4 m permanent quadrats were established at each station to track colony changes through
time. In 2005, bleaching was recorded on 88% of surveyed colonies. Using the re-randomized
sampling, there was an increase in the frequency of partial mortality from September 2005 to
August 2007 in some species, while other species were less affected. The permanent quadrats
detected different trends because of the manner in which corals undergo partial mortality. For
example, Diploria strigosa and Agaricia agaricites are more likely to die at peripheral edges,
while other species, such as Porites astreoides and Siderastrea siderea undergo patchy
mortality within the colony. The former mortality process is more difficult to detect with oneoff
surveys, but are detectable when plots are examined over time; both processes lead to
changes in size-frequency distributions. Partial–mortality trends do not appear to depend on
reproductive strategies but rather the degree of colony integrity. Some species appear more
vulnerable at the colony periphery, while others loose integration and are vulnerable
throughout. While species-specific partial mortality serves as a reliable indicator of coral stress,
there are clearly two different modes, and both are useful proxies of population dynamics.
10-36
Spatial Aggregation Promotes Species Coexistence Of Reef-Building Corals
Joshua IDJADI* 1 , Ronald KARLSON 1
1 Biological Sciences, University of Delaware, Newark, DE
Scleractinian coral species with varying competitive abilities often occur in communities where
shared resources are limited. Despite this, these communities can be very diverse, without
dominance by the best competitors. We experimentally tested the role of spatial heterogeneity,
specifically the spatial arrangement of competitors, in promoting species coexistence among
corals. Using a strong competitor (Porites rus) and a weaker one (P. lobata) we addressed the
hypothesis that when corals are intraspecifically aggregated, coexistence is increased. When
these corals were placed into artificial competitive neighborhoods, weaker competitors grew at
almost twice the rate when they were grown in aggregated versus non-aggregated patterns.
Further experimental work suggested that aggregation is most important when there is no refuge
from competition for weaker competitors. The results of these experiments were extrapolated
to larger spatial and temporal scales by a discrete space model. The persistence of weaker
competitors was increased substantially when the beneficial effect of aggregation was applied to
this model system. This research adds to evidence from other work in plant systems that spatial
arrangement can promote species coexistence in competitive, resource limited communities.
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