11th ICRS Abstract book - Nova Southeastern University

Poster Mini-Symposium 13: Evolution and Conservation of Coral Reef Ecosystems
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Ancestral Foundations and Geomorphology in Conserving Habitats and
Communities of the Ningaloo Reef, Western Australia
Emily TWIGGS* 1 , Lindsay COLLINS 1
1 Applied Geology, Curtin University of Technology, Perth, Australia
Ningaloo Reef is the fifth in a series of shoreline reef platforms developed as a response
to tectonics and sea-level fluctuations. This research aims to characterise the growth
history, geomorphology and surficial sediments of the reef and identify evolutionary
characteristics relevant to the maintenance of marine biodiversity and conservation.
Coring, coastal outcrop interpretation and shallow seismic lines provide the data on
antecedent foundations and reef growth. GIS mapping using aerial and acoustic remote
sensing alongside groundtruthing techniques have been used to characterise geomorphic
zonation, 3D structure and benthic habitat distribution.
A number of geological foundations played a major role in the establishment of Holocene
reef development (7.57 ka). These foundations are the primary physical controls on
present reef morphology and benthic habitat distribution, and include the Last Interglacial
reef (125 ka) and alluvial fans. The Last Interglacial reef was developed during a period
of higher sea-level and is expressed as the Tantabiddi terrace, coastal scarps and rock
platforms. Alluvial fans composed of carbonate gravels encroached onto the shelf during
periods of lower sea-levels and today form part of the modern reef system. Coral,
encrusting coralline algae and macroalgae communities thrive in geomorphic zones of the
back-reef. Ancestral karst has created distinct collapse structures within the reef
framework influencing community composition. On the shallow fore-reef slope there is a
thin veneer of coralgal growth on multiple backstepping spur and groove systems. Hard
corals are rapidly replaced by rhodolith beds at the transition from the lower slope-inner
shelf, which provide the substrate for deeper-water sessile benthic communities. On the
open mid-outer shelf, sediment plains are interrupted by karstified ridge systems,
drowned reefs and paleo-shorelines colonised by sponges, gorgonians and bryozoans. An
understanding of reef evolution and the strong spatial relationships between ancestral
foundations, geomorphology and contemporary ecology is essential for the ongoing
conservation of the Ningaloo Reef.
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