11th ICRS Abstract book - Nova Southeastern University

2-13
Millennial-Scale Episodes Of Reef Accretion And Degradation Determined By U-
Series Dating Of Coral Death Assemblages in Moreton Bay, Se Queensland,
Australia.
Matt LYBOLT* 1 , Jian-xin ZHAO 2 , David NEIL 3 , Yue-xing FENG 2 , Ke-fu YU 2 , John
PANDOLFI 4
1 Centre for Marine Studies, University of Queensland, St. Lucia, Australia, 2 Centre for
Microscopy and Microanalysis, University of Queensland, St. Lucia, Australia, 3 School
of Geography Planning and Architecture, University of Queensland, St. Lucia, Australia,
4 Centre for Marine Studies / Department of Earth Sciences, University of Queensland, St.
Lucia, Australia
Oral Mini-Symposium 2: Biotic Response to Ancient Environmental Change in Indo-Pacific Coral Reefs
The sub-tropical marginal reefs of Moreton Bay were characterized by diverse mid-
Holocene communities that dramatically declined in the absence of major anthropogenic
disturbance. We examined the nature and timing of changes in surficial coral death
assemblages from Moreton Bay reefs to gain insight to the interplay of local and global
changes. Corals were selected throughout the Bay across a depth range from 1 m above
high tide to 5 m below low tide. Uranium-series age determinations (n=57) were made by
Uranium-series thermal ionization mass spectrometry. The oldest sample was found atop
in situ reef accretions at the highest elevation sampled, so Moreton bay reefs initiated
before 6.82 ka and sea level must have reached its Holocene maximum prior to that time.
Since the oldest cohort of corals was not buried by younger ones we conclude that coral
accretion since 5.5 ka has been minimal. Coral accretion occurred in discrete episodes
rather than continuously, and depths of accretion, corrected for palaeo-sea-level, became
deeper through the Holocene. Major coral accretion episodes are 0-0.3 ka (19% of
samples dated), 1.3-1.7 ka (11%), 4.3-4.7 ka (11%), and 5.5-6.8 ka or older (51%).
Conspicuous episodes with no accretion are 0.4-1.1 ka and 4.7-5.5 ka. Sea-level fell from
its Holocene high in a series of oscillations which coincide with episodes of accretion
(stable/rising) and no accretion (falling). Greater extremes of temperature and salinity
would result from a lower volume of water in the Bay, and decreased tidal volume would
increase the residence time of river-discharge amplifying the sea-level-driven episodes.
The hyposaline wedge associated with increased flooding since ENSO re-establishment
~3.5 ka likely forced younger accretions into deeper water. Because European
colonization coincides with an episode of accretion we have an excellent opportunity to
isolate historical causes of reef decline from novel anthropogenically-induced causes of
decline.
2-14
Holocene To Recent Foraminifera Assemblages Of Moreton Bay, Queensland, Australia:
Assessing Modern And Historical Estuarine Habitats, Degradation And Foraminiferal
Responses To Environmental/faunal Changes
Yogeeta Roshni NARAYAN* 1,2
1 Earth Sciences, University of Queensland, Brisbane, Australia, 2 Centre for Marine Studies,
University of Queensland, Brisbane, Australia
Moreton Bay (MB) is internationally (Ramsar), nationally (EPBC Act) and State (Marine Parks
and Fisheries Habitat Reserves) recognized for its biodiversity, socio-economic and historical
significance. The Bay and its large (21,220 km 2 ) catchment area are on the doorstep to
Queensland fastest developing urban centre. The increasing population pressures and coastal
development, coupled with the effects of climate change, have raised concerns over current
conservation and management of critical habitats (i.e. seagrass meadows, fringing reefs) and
biodiversity. At present, the MB Marine Park is undergoing assessment of the Bay’s diverse
habitats, compiling existing knowledge of the Bay’s ecosystem and assessing the sustainability
of ongoing activities. Investigations of the foraminiferal (foram) assemblages, which span the
mid-Holocene (~6,500 years before present, ybp), through European colonization (~200 ybp) to
the Recent, is timely with the above Action Plan.
The mid-Holocene was a time of climatic optimum. Coral communities flourished and were
dominated by the fast-growing Acropora species. Since the mid-Holocene, oscillations in
climate and the environment have influenced species diversity and composition. European
settlement introduced anthropogenic inputs, furthering deterioration of habitats from increased
sedimentation and pollution. This study aims to; 1) assess decadal changes in diversity and
distribution of forams since the 1970’s (Geological Survey of Queensland datasets); 2) survey
assemblages from the Holocene through European colonization and correlate with concurrent
coral community studies; and 3) evaluate sea-grass associated forams as a proxy for historical
seagrass distribution and changes in water quality, in the last 200 years. Adequate
understanding of the faunal changes, overtime, whether influenced by natural and/or
anthropogenic impacts, is crucial in understanding long-term habitat degradation and providing
baseline studies for future ecosystem management. Moreton Bay is an exceptional location for
such a study and foraminfera play a valuable role in decadal and millennial scale investigations
of biotic change in estuarine environments.
2-15
Historical Collapse Of Acroporid Corals At Pelorus Reef, Inshore Great Barrier Reef
George ROFF* 1 , Tara R CLARK 2 , Jian-xin ZHAO 2 , John M PANDOLFI 1
1 Centre for Marine Studies, University of Queensland, Brisbane, Australia, 2 Centre for
Microscopy & Microanalysis, University of Queensland, Brisbane, Australia
Since European settlement of the Queensland coastline in the mid-18th century, extensive
changes in land usage within in the Great Barrier Reef (GBR) catchment region have occurred,
resulting from increases in grazing, agriculture and land clearance. Evidence is accumulating
that inshore reefs of the GBR are undergoing persistent phase shifts, with losses of previously
dominant acroporid communities and local removal of coral species. Despite this, considerable
difficulty exists in determining the extent and magnitude of the decline, primarily due to a lack
of historical data on coral communities. To address this issue, we conducted palaeoecological
reconstructions of coral communities through surveys of modern coral communities in
conjunction with extensive collections of in-situ surface coral rubble (death assemblages) at
Pelorus Reef (central GBR). Comparisons of sites with low modern coral cover (