11th ICRS Abstract book - Nova Southeastern University

9-1
Herbivore Diversity And Feeding Complementarity Affect The Structure Of
Caribbean Reefs
Mark HAY* 1 , Deron BURKEPILE 2
1 School of Biology, Georgia Institute of Technology, Atlanta, GA, 2 Department of
Ecology and Evolutionary Biology, Yale University, New Haven, CT
On coral reefs, herbivorous fishes have strong top-down effects on community structure,
macroalgal abundance, and coral resilience. However, the longer-term direct and indirect
effects of herbivore species richness on reef communities are inadequately understood.
To evaluate the effects of herbivore species richness on community structure, we
enclosed equivalent densities and masses of either single-species or mixed-species of
herbivorous fishes in replicate, 4 m2 cages on a reef in the Florida Keys. The experiment
ran for 8-10 months in two separate years. We found strong effects of herbivore richness
on seaweed abundance, coral growth and survivorship, and community structure due to
feeding complementarity between herbivores. In Year 1, ocean surgeonfish and redband
parrotfish synergistically suppressed cover and biomass of upright macroalgae by 54-
76% compared to single-species treatments due to complementary feeding on different
seaweeds. One herbivore appeared deterred by chemical, the other by structural, seaweed
defenses. The mixed-species treatment also increased cover of crustose coralline algae
by 23-117%, increased coral cover by 22%, and decreased coral mortality from the 8-
24% in single-species treatments to 0%. In Year 2, redband parrotfish and princess
parrotfish fed on different algal functional groups with redbands suppressing upright
macroalgae and princesses suppressing filamentous algae, again increasing cover of
crustose coralline algae. When nonmetric multidimensional scaling was used to compare
all treatments across both years, the morphologically and taxonomically dissimilar
princess parrotfish and ocean surgeonfish had more similar effects on macroalgal
community structure than did the two parrotfishes. Herbivores play functionally diverse
roles on reefs, and these differential feeding abilities prevent macrophytes from escaping
control and suppressing corals.
9-2
Are Tropical Herbivores More Tolerant Of Chemically-Rich Seaweeds Than Are
Temperate Herbivores? A Test Of Seaweed-Herbivore Coevolution.
Erik SOTKA* 1 , Amanda MCCARTY 1
1 Grice Marine Laboratory, College of Charleston, Charleston, SC
Lipophilic secondary metabolites produced by seaweeds increase in strength and
diversity as one moves toward the tropics. Coevolutionary theory predicts that tropical
herbivores should more readily tolerate chemically-rich seaweeds and their metabolites,
however, data supporting this prediction are largely correlative and rarely evaluated
experimentally. We examined feeding tolerance for chemically-rich seaweeds among
populations of a single species, the herbivorous amphipod, Ampithoe longimana
collected along the eastern coast of North America from New England (41ºN) to southern
Florida (26º N). In contrast with coevolutionary predictions, geographic patterns of
feeding preference were not correlated with latitude. Rather, populations in North
Carolina (34ºN) were far more tolerant of the diterpene-producing seaweed Dictyota
than were New England or Florida populations. Field-surveys across multiple seasons
indicate that Dictyota represents an important host to North Carolina populations, but
that Dictyota is not used as a host by either New England or Florida populations. Thus,
geographic patterns of feeding tolerance by A. longimana are best explained by the
relative importance of Dictyota in the ecology of local populations. In spite of
prevailing assumptions, our results indicate tropical herbivores will not necessarily be
more tolerant than temperate herbivores for lipophilic chemical defenses produced by
seaweeds.
Oral Mini-Symposium 9: Chemical Ecology on Coral Reefs
9-3
Organic Matter Release By Coral Reef Associated Benthic Algae -Implications For in-
Situ Oxygen Dynamics
Andreas HAAS* 1 , Malik NAUMANN 1 , Florian MAYER 1 , Christoph MAYR 2 , Mohammed
AL-ZIBDAH 3 , Christian WILD 1
1 Coral Reef Ecology Work Group (CORE), GeoBio-Center LMU München, Munich, Germany,
2 Department of Earth and Environmental Science, GeoBio-Center LMU München, Munich,
Germany, 3 Marine Science Station, Yarmouk University, Aqaba, Jordan
Recent research indicates that coral reef associated benthic algae may affect important
processes in the reef ecosystem via organic matter release, but yet no information is available
about the quantity, quality and fate of these exudates. For this reason first fundamental studies
were conducted at fringing reefs in the Northern Red Sea during two expeditions in fall 2006
and summer 2007. For the most abundant reef associated benthic algae (representing nearly
100% of total benthic algae coverage), green algae of the genus Caulerpa, red algae of the
genus Peyssonnelia and several typical turf algae consortia, the release of dissolved and
particulate organic carbon (DOC and POC) was quantified. All investigated benthic algae
exuded high rates of DOC, but also POC in amounts of up to 5430 and 360 mg organic C m - ²
algae surface area d -1 , respectively. Release of DOC was highly variable between seasons, with
one order of magnitude higher release rates in fall compared to summer. High DOC:POC ratios
of up to 22 indicated that most of the exuded algae-derived organic matter immediately
dissolved in reef waters, thereby stimulating planktonic microbial oxygen consumption as
verified experimentally. In-situ experiments in high spatial resolution using dissolved oxygen
loggers confirmed lower daily mean oxygen concentrations in the water close to algae
dominated reef areas compared to those dominated by hermatypic corals. Thus, this study
supports the hypothesis of microbial involvement in coral-algae interactions, indicates relevance
for in-situ processes and also provides a fundamental data set for further required ecosystem
studies.
9-4
Nutrient Distribution Across the Insular Shelf of Puerto Rico: Assessment by Algal
Tissue Nitrogen
Brandi TODD* 1 , David L. BALLANTINE 1 , Ernesto OTERO 1
1 Ciencias Marinas, University of Puerto Rico, Mayaguez, Puerto Rico
A survey was conducted to investigate possible presence of an inshore to shelf edge gradient in
%N and δ15N tissue content of Acanthophora spicifera, Lobophora variegata, and
Dictyota sp. in coastal waters of La Parguera, southwest Puerto Rico. Percent N (1.26% ± 0.08
to 3.25% ± 0.10) and δ15N (2.06ppt ± 0.04 to 8.16ppt ±0.14) of Acanthophora spicifera was
highly variable along the shoreline. The highest inshore values of δ15N occurred at two stations
influenced by secondary sewage input and a bird rookery and lower values (0.81ppt ± 0.06)
were observed at mid-shelf locations. Dictyota sp. and L. variegata did not display trends in
%N across the insular shelf, however δ15N for Dictyota sp. was significantly higher inshore
(3.48ppt ± 0.087) versus mid-shelf and shelf edge (0.00ppt ± 0.08) and δ15N for L. variegata
was significantly higher at mid-shelf (2.13ppt ± 0.25) versus shelf edge locations (0.34ppt ±
0.24). These results indicate that anthropogenic impacts on tissue nutrients are greatest along
the shoreline, moderate at mid-shelf, and not evident at the shelf edge.
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