11th ICRS Abstract book - Nova Southeastern University

Poster Mini-Symposium 13: Evolution and Conservation of Coral Reef Ecosystems
13.423
The Origins And Fate Of Reef Island Sediments
Deirdre HART* 1
1 Department of Geography, University of Canterbury, Christchurch, New Zealand
Low coral reef islands are constructed almost entirely of biogenic reef sediments
originating primarily from surrounding reef platform ecosystems. Beaches comprise the
interface between reef ecosystems and islands through which the latter are nourished,
built or eroded. This research characterises functional relationships between island-beach
sediments and reef-flat sources on Warraber Reef, an intertidal reef platform system in
central Torres Strait, Australia.
The origins and transport pathways of beach-nourishing sediments were examined using
(a) an array of wave gauges, current meters and sediment traps, (b) ecological and
geomorphic surveys, and (c) textural, compositional and dating analyses of 218 samples
of surface sediment.
Overall, reef flat sediments (moderately-sorted fine sands to gravels of mollusc/coralline
algae/coral origin) were found to differ greatly in composition and texture from those of
the island beach (mollusc-dominated moderately to very-well sorted coarse sands).
Ecologic, hydrodynamic and sediment patterns reveal the mollusc and algae covered sand
flats of the emergent, inner, windward reef flat as the dominant contemporary source of
beach nourishing sediment. In contrast, the deeper, more-distant and leeward reef-flat
zones were found to be isolated from the modern island deposit. These sediment
relationships occurred despite the order of magnitude greater carbonate productivity,
more-frequent submergence, and more-energetic wave environment of the latter areas but
in line with reef flat sediment transport directions and the proportionately-greater
sediment particle production rates of organisms living in the windward, near-island
zones.
Findings reveal the sediment system of this large reef platform to be strongly
compartmentalised such that the contemporary maintenance and growth of the island
depends on organisms and processes operating within a small physiographic and
ecological sector of the surrounding reef flat. Any change in physical conditions across
the reef flat is forecast to produce major adjustments in the amount, type, and supply
rates of island nourishing sediment.
13.424
Recruitment Dynamics Of The Three-Spot Damselfish, Dascyllus Trimaculatus, in
Moorea, French Polynesia
Ricardo BELDADE* 1 , Sally HOLBROOK 2 , Russell SCHMITT 2 , Giacomo
BERNARDI 1
1 Department of Ecology and Evolutionary Biology, University of California, Santa Cruz,
Santa Cruz, CA, 2 Ecology, Evolution & Marine Biology, University of California, Santa
Barbara, Santa Barbara, CA
The three-spot damselfish, Dascyllus trimaculatus, is a coral reef species that spawns
benthic eggs. After hatching, larvae remain in the water column for about 26 days and
then recruit back on anemones. After growing to a size large enough to escape predation,
the fish leave the anemone after a few months to live a demersal adult life. In order to
study the recruitment dynamics of this species, we have placed two rows, of 8 anemones
each. Anemones were 10 meters apart; the two rows were 100 meters apart. The two
rows were parallel to shore and to the barrier reef, within the lagoon of Moorea, French
Polynesia. The crest row was 50m from the barrier reef, and the channel row was 100m
downstream from the crest row. Every morning the new incoming recruits were collected.
Through genetic typing, a single nucleotide polymorphism (SNP) showed that the fishes
from the two rows are genetically distinct (chi-square p