11th ICRS Abstract book - Nova Southeastern University

Poster Mini-Symposium 10: Ecological Processes on Today's Reef Ecosystems
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The importance of habitat type and presence of conspecifics in habitat selection of a
coral reef fish
Chantal HUIJBERS* 1 , Ivan NAGELKERKEN 1
1 Animal Ecology and Ecophysiology, Radboud University Nijmegen, Nijmegen,
Netherlands
Habitat selection of coral reef fish may be influenced by a variety of factors such as
shelter, food availability, presence of conspecifics, habitat size, etc. In this study, a field
experiment was designed to test habitat preference of the reef fish species Haemulon
flavolineatum. Choice experiments were conducted in situ in experimental enclosures
using four shallow-water habitat types in which this species naturally occurs: coral reef,
rubble, mangroves and seagrass beds. A second experiment tested the degree to which
presence of conspecifics or heterospecifics plays a role in habitat selection. Odours from
the experimental habitats were blocked to ascertain that choices were based purely on
vision. Five different life stages were tested, i.e. recruits (2 – 3.5 cm) and small juveniles
(4 – 6 cm) from rubble habitat, small (4 – 6 cm) and larger (> 12 cm) fishes from seagrass
beds, and larger individuals (10 – 14 cm) from the coral reef. Individuals of all life
stages, except the smallest individuals from the rubble habitat, preferred mangroves as a
habitat. In addition, their preference did not differ between mangroves harbouring
conspecifics and conspecifics alone, although conspecifics were always preferred above
heterospecifics. Only the recruits from the rubble habitat did not prefer a single habitat,
and chose more often for conspecifics alone than conspecifics combined with a habitat
type. This suggests that for recruits any structure may be sufficient as shelter, while
presence of conspecifics appears to play an important role. For larger individuals, the
experiment indicates that the structural complexity of mangroves is most attractive for H.
flavolineatum, probably because of the better protection against predators.
10.314
Predation, Size Composition And Distribution Of Crown-Of-Thorn Starfish On
Lankayan Island Reefs: Result Surveys 2005 To 2007
Fung Chen CHUNG* 1
1 Reef Guardian Sdn Bhd, Sandakan, Malaysia
Outbreaks of coral-eating Crown-of-thorns starfish (Acanthaster planci) can cause severe
damage to coral reefs. These outbreaks have been observed around Lankayan Island since
2005. To develop appropriate control measures, it is necessary to understand the
distribution of Crown-of-thorns starfish (COTs). Therefore, the objective of this study
was to document the predation, size composition and distribution of COTs from 2005-
2007. The size composition and distribution of COTs tend to be associated with reef
morphology such as reef depth, coral cover and types. Adult COTs were found at the
deeper reefs at 14-20m reef slope. In contrast, smaller COTs were more likely to be
found in shallow reefs at 3-10m. The COTs preferred feeding on branching & tabular
corals and less on massive and encrusting corals. The distribution of COTs were not
evenly distributed, and ongoing monitoring indicated that the outbreak pattern occurred
due to mass migration of COTs from reef to reef. Oceanographic current patterns, natural
events such as storms, and destructive fishing activities are factors that likely caused
COTs outbreaks in Lankayan reefs.
10.315
Bleaching, Pollution And The Coral oculina Patagonica
Roee SEGAL* 1,2 , Rachel ARMOZA-ZVULONI 2 , Ido MIZRACHI 2 , Noa SHENKAR 2 , Yossi
LOYA 2
1 Porter School of Environmental Studies, Tel-Aviv University, Tel-Aviv, Israel, 2 Department of
Zoology, The George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv, Israel
The aim of this research was to study the effect of land based industrial and household pollution
on bleaching dynamics, colony size and reproduction effort in the encrusting coral Oculina
patagonica. A one-year monitoring of populations of the coral O. patagonica was conducted in
4 sites polluted by an array of pollutants and their 4 reference sites along the Israeli coast of the
Mediterranean Sea. Surveys of intra-colonial bleaching percentage showed that during the peak
bleaching season (August-September), there were no differences between corals from the
polluted sites and those from the reference sites. Recovery was seen during the winter in all
sites regardless of pollution impact. The average colony size was significantly smaller in corals
from all polluted sites when compared with corals from their reference sites. In general, no
differences were found in gonad size, development and sex ratio between populations from the
polluted and reference sites. Size frequency distribution of colonies suffering from annual
bleaching shifted toward smaller size. This phenomenon was more dramatic in the polluted sites
in the southern part of Israel with minimum of average colony area in Ashdod (8.8 ± 1 cm2)
compared to their reference site Palmachim (13.4 ± 1 cm2) and to the northern site where no
bleaching or pollution was evident (Achziv; 257.9 ± 50 cm2). Therefore, populations of the
coral Oculina patagonica reproduce even in highly polluted sites. Despite this, the lower
average size of the colonies in the polluted sites, results in a lower reproductive fitness of the
population, since fewer polyps are reproducing. The additive effect of pollution and bleaching,
which was previously shown to cause partial mortality to the colonies, resulting in a further
decrease in colony size, will eventually negatively affect reproductive fitness of populations of
this coral in these areas.
10.316
Underestimated Eroder Among Reef Fishes -Experimental Comparison Between
Ctenochaetus Striatus And Acanthurus Nigrofuscus (Acanthuridae)
Helmut SCHUHMACHER* 1 , Roland KRONE 2 , Peter van TREECK 3
1 Hydrobiology, Universitaet Duisburg-Essen, Essen, Germany, 2 Marine animal ecology, Alfred-
Wegener-Institute for polar and marine research, Bremerhaven, Germany, 3 Universitaet
Duisburg-Essen, Essen, Germany
The acanthurid fish species Ctenochaetus striatus and Acanthurus nigrofuscus are common
detritivore browsers. Less is known about their erosion potential. We offered coral limestone
for grazing in 24h-aquarium experiments and recorded the feeding behaviour by video. C.
striatus produced 15 times more calcareous sediments (faeces and loose material) compared to
A. nigrofuscus despite of a 5 times higher biting rate of A. nigrofuscus. This discrepancy can be
explained by different feeding techniques of the species. A. nigrofuscus performed careful
picking bites only, whereas C. striatus showed a more differentiated feeding behaviour: soft
sweeping of the surface alternating with chafing the substrate with grasping bites at which the
whole body was shaking and exerting trust. Hereby a special palate structure (bow of hard
knobs in the upper jaw) is engaged which allows to rasp the reef substrate (Krone et al. 2006).
The measured eroded masses per bite and the number of bites per individual were related to the
population densities of the two species on three reef crests in the Northern Red Sea. Based on
these calculations, A. nigrofuscus attains maximum erosion rates of 2.6 g m-2 yr-1 and may
therefore not be regarded as a relevant bioeroder, but C. striatus achieves erosion rates of up to
70.0 g m-2 yr-1 which is in the same order as that of the co-occuring sea urchin Diadema
setosum.
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