11th ICRS Abstract book - Nova Southeastern University

Poster Mini-Symposium 10: Ecological Processes on Today's Reef Ecosystems
10.278
Defining Fundamental Niche Dimensions Of Corals: Synergistic Effects Of Colony
Size, Light And Flow
Mia HOOGENBOOM* 1 , Sean CONNOLLY 1
1 School of Tropical and Marine Biology, ARC Centre of Excellence for Coral Reef
Studies, James Cook University, Townsville, Australia
The ‘fundamental niche’ is the range of conditions under which an organism can survive
and reproduce in the absence of biotic interactions. Niche measurements are often based
on statistical relationships between species presence and environmental variables, or
inferred from measured responses (e.g. growth rates) along hypothesized niche axes. In
this study, we use novel, process-based models of how irradiance and gas diffusion
influence photosynthesis and respiration, to predict niche dimensions for three coral
species (Acropora nasuta, Montipora foliosa and Leptoria phrygia). We use a
combination of mathematical modeling, laboratory experiments and field observations to
establish the link between energy acquisition and the dominant environmental gradients
on reefs – light intensity and water flow velocity. The model predicts that, due to its
higher photosynthetic capacity, the branching coral A. nasuta has a positive energy
balance over a wider range of conditions than both a massive (L. phrygia) and a foliose
species (M. foliosa). Moreover, colony size influences niche width, with larger colonies
of all three species achieving a positive energy balance over a broader range of conditions
than small colonies. Comparison of model predictions with field data demonstrates that
observed tissue biomass and reproductive output are strongly correlated with model
predictions of energy acquisition, despite the many additional sources of colony-level
variation in energy acquisition that occur under field conditions. These results show how
interactions between light and flow determine organism performance along
environmental gradients on coral reefs. In addition, this study demonstrates the utility of
process-based models for quantifying how physiology influences ecology, and for
predicting the ecological consequences of varying environmental conditions.
10.279
Density Effects On Grouping Behavior And Habitat Associations Of Recruit Reef
Fishes in Hawaii: Contrasts Between Years And Among Species
Edward DEMARTINI* 1 , Todd ANDERSON 2 , Alan FRIEDLANDER 3 , Jim BEETS 4
1 NMFS, NOAA, Aiea, HI, 2 Biology, San Diego State University, San Diego, CA, 3 NOS,
NOAA, Waimanalo, HI, 4 Marine Science, University of Hawaii at Hilo, Hilo, HI
We used in situ surveys of recruit reef fishes (≤ 5 cm TL) to explore the possible effects
of recruit density on habitat associations and on the incidence and degree of association
among conspecific and heterospecific recruits. Surveys were conducted in 2006 and 2007
at wave-protected fringing reefs on the Big Island of Hawaii (in the Main Hawaiian
Islands) and at protected back reefs on Midway Atoll, Northwestern Hawaiian Islands,
2000 km upchain of Hawaii Island. Recruit densities differed almost 3-fold between 2006
(13 fish/100 m2) and 2007 (34 fish/100 m2) and were especially pronounced for small (≤
2 cm TL), recently settled individuals. Both the incidence of groups (≥ 2 fish individuals
within 10 cm radius) and the median number of individuals present in groups were
greater in 2007 when recruit densities were higher. Electivity of recruits for rugose coral
substrata differed between sites and years for some, but not all species. Electivity for
rugose corals also varied positively with recruit density for taxa such as Chlorurus spp
(Scaridae) that associate disproportionately with corals like Porites compressa and erect
Montipora spp. We suggest that habitat electivity and grouping behavior are sensitive to
annual and other variations in settler density for some species and that rugose coral
habitat is especially important for strong year-classes of these species. Recruit density,
grouping, and habitat electivity thus might interact to importantly influence year-class
strength and related population dynamics.
10.280
Substratum Utilization And Space Competition With Reef Corals By The Caribbean
Excavating Sponge cliona Delitrix
Andia CHAVES-FONNEGRA* 1 , Sven ZEA 1
1 Departamento de Biología and Centro de Estudios en Ciencias del Mar -CECIMAR-,
Universidad Nacional de Colombia, INVEMAR, Cerro Punta de Betín, Santa Marta, Colombia,
Santa Marta, Colombia
The Caribbean sponge Cliona delitrix is a strong reef bioeroder, amply encrusting and deeply
excavating corals. To interpret current trends of reef space occupation, sponge presence and
abundance was recorded in relation to the degree of reef development and coral health status at
the W shallow fore-reef terrace of San Andrés Island, SW Caribbean, Colombia. To establish
the circumstances and the speed at which this sponge advances laterally into live coral, and the
corals retreat, 44 sponge-colonized coral colonies were marked and followed for 13 months.
Steel nails driven at the sponge-coral frontier were used to measure advance and retreat. C.
delitrix prefers elevated portions of the substratum built by massive corals, and currently
inhabits 6 % to 9 % of colonies in sites in which it is locally abundant. This sponge is
disproportionately common in Siderastrea siderea, a massive coral locally more susceptible to
be colonized. C. delitrix colonizing live corals was always surrounded by a few mm to several
cm-wide band of dead or dying coral tissue, which was being undermined by excavating tissue
fronts and filaments. C. delitrix was responsible for coral tissue death only when they were in
close proximity, being both organisms in direct competition for space. At greater distances,
coral death was independent of sponge advance, being indirectly dependent on other conditions
that tended to accelerate it. Biting by the long-spined sea urchin Diadema antillarum allowed
the sponge to advance slightly faster than when the death band was covered by algae or other
organisms. Current mortality and bioerosion threats to massive corals from C. delitrix could
initially change the relative proportions of different coral species and, in the long term, favor
foliose and branching corals.
10.281
The Effect Of Predatory Disturbance On Spatial Arrangement in cryptocentrus
Singapurensis (Herre, 1936)
Rebecca SHELL 1 , Craig SYMS* 2
1 College of Science and Math, Montclair State University, Montclair, NJ, 2 School of Marine
and Tropical Biology, James Cook University, Townsville, Australia
Disturbance events of all types influence the availability of resources such as prey and habitat
availability, and can drastically affect community structure and spatial arrangement. The goby
Cryptocentrus singapurensis does not venture far from burrows shared with, and maintained by,
alpheid shrimps. This study examines how physical parameters determine goby distribution,
and to what extent natural and artificial levels of disturbance have on the goby community and
its trophic dependents. C. singapurensis burrows were mapped in six quadrats on a sand flat in
Pioneer Bay, Orpheus Island, Queensland. Quadrats were artificially disturbed at increasing
levels, mimicking the predatory methods of rays, a natural predator. Post-disturbance
comparisons show no significant alteration in spatial arrangement at any level: goby burrows
tend towards random distributions at smaller scales and overdispersal at distances greater than
1m. This pattern is not correlated with grain size or prey availability. Microfaunal gastropod
abundance was significantly lower 5cm away from goby burrows, but prey abundance did not
explain community spatial arrangement at scales larger than 50cm. A larger investigation may
indicate large-scale spatial patterns undetected by this small-scale study. Any such
investigations should attempt to isolate predation patterns by locating experimental disturbance
events in ecologically desirable areas.
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