11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 10: Ecological Processes on Today's Reef Ecosystems
10-1
Linking Herbivory To Coral Recruitment And Local Management
Suzanne ARNOLD* 1 , Robert STENECK 1 , Peter MUMBY 2 , Valerie PAUL 3 , Raphael
RITSON-WILLIAMS 3
1 School of Marine Sciences, University of Maine, Walpole, ME, 2 Marine Spatial Ecology
Laboratory, School of BioSciences, University of Exeter, Exeter, United Kingdom,
3 Smithsonian Marine Station at Fort Pierce, Fort Pierce, FL
Coral reefs worldwide have suffered reduced coral cover in response to large scale
disturbances. Unfortunately, Caribbean reefs have shown little or no recovery following
these disturbances, and while they decline, the debate over how to best manage for reef
recovery persists. Coral recruitment is central to the recovery of corals reefs. Several
studies (including our own) suggest that scraping herbivores, such as some species of sea
urchins and parrotfish, correlate inversely with algal biomass and positively with juvenile
coral abundance. This manipulative experiment tests the hypothesis that herbivory
facilitates coral recruitment. We focus on herbivorous fishes, particularly parrotfishes, as
regulators of fore reef macroalgae and ultimately the recruitment potential for Caribbean
reefs. We chose reefs in Bonaire and Belize representing a gradient in parrotfish grazing
from high to low, respectively. Within regions, we measured coral recruitment on
terracotta tiles with and without stainless steel pegs that impede large parrotfish. The
quantitative data on the frequency and intensity of grazing, the settlement of corals, and
the algal biomass and community structure that developed surrounding the treatment and
control tiles after one year (March 2007-March 2008) will be reported. With these data,
we hope to provide further evidence for the link between healthy herbivorous fish
populations, algal abundance, and coral recruitment, as well as timely scientific support
for the need to protect parrotfish.
10-2
The Effect Of Echinoids On Caribbean Coral Recruitment--A 20 Year Study
Harilaos LESSIOS* 1
1 Smithsonian Tropical Research Institute, APO AA
The recruitment and survival of juvenile corals on natural substrates was followed at
monthly intervals at the San Blas Islands (Caribbean Panama) on four reefs under four
treatments from 1984 to 2004. One treatment consisted of complete removal of all
echinoids, one of the presence of Diadema antillarum at pre-mass mortality densities, one
of the presence of Echinometra viridis, and one of the presence of both species. Every 3-
5 years, the treatments were rotated between reefs in order to separate treatment and reef
effects. The results indicate that in the absence of sea urchins coral recruitment is
reduced. Diadema (at 1 m-2) or Echinometra (at 14 m-2), or both (at these natural
densities), have approximately equally positive effects for coral recruitment. Siderastrea
radians, S. siderea, Agaricia sp., Favia fragum, and Porites astreoides are the most
frequently recruiting species, but they also show the highest post-recruitment mortality.
Diploria strigosa, Acropora palmata, Isophylastrea rigida, I. sinuosa, Montastraea
annularis and M. cavernosa recruit at much lower rates, but have higher per capita
survival rates. Thus, echinoids play an important role in shaping Caribbean scleractinian
communities.
10-3
Coral Reef Resilience: Balancing Production And Herbivory
Fiona WEBSTER* 1 , Russ BABCOCK 2 , Mike VAN KEULEN 1 , Neil LONERAGAN 1
1 School of Biology and Biotechnology, Murdoch University, Perth, Australia, 2 Marine
Research, Commonwealth Scientific and Industrial Research Organisation, Floreat, Australia
The Ningaloo Reef provides a unique opportunity to investigate different components of a coral
reef ecosystem without the confounding effects of poor water quality and severe overfishing.
This research examined a) how macroalgae affects coral recruitment and b) the processes which
drive macroalgal abundance. These experiments were conducted in the field using a series of
caged, uncaged and partially caged treatments to examine herbivory and control for caging
effects. It was identified for the first time, that both the pre- and post- settlement processes of
coral recruitment were severely reduced by increased macroalgal biomass. In the presence of
macroalgae - for the coral Acropora millepora: larval settlement was reduced by up to 93%,
post settlement survival was approximately half and those which did survive were around 80%
smaller compared to corals in uncaged plots which contained little macroalgae. This
demonstrates that macroalgae can inhibit coral reef recovery by reducing coral recruitment.
Bottom up versus top down influences on macroalgal abundance were examined in a
multifactorial study using slow release fertilizer and cages to manipulate herbivory. Nubbins of
Cyphastrea microphthalma were used as a proxy for coral recruits. Nutrients had no effect on
macroalgal biomass and coral calcification. Herbivores on the other hand had a strong
overriding effect. The volume of macroalgae was up to 40 times greater in caged versus
uncaged plots. Over a nine month period the growth of coral nubbins in cages beneath the
macroalgae was reduced by approximately 50% compared to uncaged plots. Through video
analysis it was identified that the most important herbivores for controlling macroalgal
abundance were large parrot fish, in particular Cholurus sordidus and Scarus schlegeli. These
results emphasize the importance of protecting herbivores, in particular larger scarids from
overfishing to facilitate coral recruitment and promote coral reef resilience.
10-4
Contrasting Effects of Benthic Algae on Coral Recruits in an Upwelling Reef from the
Colombian Caribbean
Dagoberto VENERA-PONTON* 1 , Guillermo DIAZ-PULIDO 2 , Laurence MCCOOK 3 ,
Alejandro RANGEL-CAMPO 1
1 Instituto de Investigaciones Tropicales-INTROPIC, Universidad del Magdalena, Santa Marta,
Colombia, 2 Centre for Marine Studies and ARC Centre of Excellence for Coral Reef Studies,
University of Queensland, Brisbane, Australia, 3 Great Barrier Reef Marine Park Authority-
GBRMPA, Townsville, Australia
Reef degradation generally involves the replacement of hard corals cover by benthic algae. A
successful recovery of coral populations will depend on the competitive ability of corals to
settle, recruit, growth and survive on habitats dominated by benthic algae. Most studies on
coral-algal interactions and on the impacts of algae on the recovery of coral populations have
focused on the roles of algae on coral settlement and adult performance; however, there is very
little known about the effects on the survival of coral recruits, a critical step in the resilience of
coral reefs. Here we present the results of an experiment investigating 1) whether coral recruits
actually compete for space with the surrounding benthic algae; 2) the effects of benthic algae on
the growth and survival of coral recruits, and 3) the roles of algae on parrotfish predation on
coral recruits. The study used recruits of the coral Porites astreoides and was carried out in the
Tayrona National Natural Park in the Colombian Caribbean during two contrasting climatic and
oceanographic seasons (upwelling and non-upwelling). We found that the growth of recruits of
the coral P. astreoides was significantly increased when the surrounding algae were removed
while a weak algal colonization occurred when the coral recruits were damaged. These results
were consistent among the upwelling and non-upwelling seasons and constitutes an unequivocal
proof for competition between algae and coral recruits. The coral recruits were bitten by
parrotfishes only when the surrounding algae were removed and it was also consistent among
the two seasons. This suggests that benthic algae may actually protect coral recruits from
parrotfish damage. Our results illustrate the complexities of the effects of coral reef algae on the
early life history stages of corals.
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