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Designing a representative network of high seas marine protected areas (MPAs) requires an acceptable
scheme to classify the benthic (as well as the pelagic) bioregions of the oceans. Given the lack of
sufficient biological information to accomplish this task, we used a multivariate statistical method with 6
biophysical variables (depth, seabed slope, sediment thickness, primary production, bottom water dissolved
oxygen and bottom temperature) to objectively classify the ocean floor into 53,713 separate
polygons comprising 11 different categories, that we have termed ‘‘seascapes’’. A cross-check of the
seascape classification was carried out by comparing the seascapes with existing maps of seafloor
geomorphology and seabed sediment type and by GIS analysis of the number of separate polygons,
polygon area and perimeter/area ratio. We conclude that seascapes, derived using a multivariate
statistical approach, are biophysically meaningful subdivisions of the ocean floor and can be expected to
contain different biological associations, in as much as different geomorphological units do the same.
Less than 20% of some seascapes occur in the high seas while other seascapes are largely confined to the
high seas, indicating specific types of environment whose protection and conservation will require
international cooperation. Our study illustrates how the identification of potential sites for high seas
marine protected areas can be accomplished by a simple GIS analysis of seafloor geomorphic and
seascape classification maps. Using this approach, maps of seascape and geomorphic heterogeneity were
generated in which heterogeneity hotspots identify themselves as MPA candidates. The use of computeraided
mapping tools removes subjectivity in the MPA design process and provides greater confidence to
stakeholders that an unbiased result has been achieved.

Two cores of Holocene sediment, collected on opposite flanks of the Vanderford Glacier in Vincennes Bay, while representing contemporaneous sedimentation, have different sediment characteristics.  That on the western side has a relatively lower biogenic content than that on the east.  These sedimentological signatures are attributed to differences in circulation patterns between the two sides. Circulation involves landward flow at depth, bringing warmer ocean water into contact with the base of the glacier.  This water becomes mixed with fresh meltwater and suspended glacial sediments to form a buoyant plume that rises and flows in a seaward direction under the ice shelf.  The landward and seaward flows are deflected to the left in the southern hemisphere by the Coriolis effect, and hence they are laterally separated.  This pattern of laterally separated flow explains the differences observed in sediments deposited on opposite sides of the ice shelf in front of the Vanderford Glacier.  Such a pattern of sedimentation may be a common feature beneath all large-scale ice shelves.

Stratigraphic information concerning the retreat of the Antarctic ice sheet from the continental shelf after the last glacial maximum is reviewed and compared with new results from a shelf valley off Mac. Robertson Land, East Antarctica.  Radiocarbon dates and detailed lithostratigraphic logs indicate that the onset of open marine conditions over shallow shelf banks (<200 m water depth) were achieved prior to 7 000 yr BP and over deep (~1 000m) middle to outer shelf valleys open marine conditions were achieved prior to 5,400 yr BP.  Radiocarbon dating of bulk-organic carbon in some diatom oozes by the AMS method demonstrates problems of contamination.  Jurassic pollen, spores and organic matter has been eroded and incorporated into Holocene diatom ooze, causing anomalously old 14C dates (eg. one surface age of 7 084 ±86 yr BP was determined).  This problem may arise at other locations around East Antarctica where older strata outcrop on the seafloor.

This introductory chapter provides an overview of the book’s contents and definitions of key concepts including benthic habitat, potential habitat and seafloor geomorphology.  The chapter concludes with a summary of commonly used habitat mapping technologies. Benthic (seafloor) habitats are physically distinct areas of seabed that are associated with particular species, communities or assemblages that consistently occur together.  Benthic habitat maps are spatial representations of physically distinct areas of seabed that are associated with particular groups of plants and animals.  Habitat maps can illustrate the nature, distribution and extent of distinct physical environments present and importantly they can predict the distribution of the associated species and communities. 
The data sets collected for constructing habitat maps provide fundamental information that can be used for a range of management and industry applications, including the management of fisheries, spatial marine environmental management, design of marine reserves, supporting offshore oil and gas infrastructure development, port and shipping channel construction, maintenance dredging, tourism and seabed aggregate mining.  Seafloor habitat mapping provides fundamental baseline information for decision-makers working in these sectors. 
GeoHab (www.geohab.org) is an international association of marine scientists conducting research using a range of mapping technologies into the use of biophysical (i.e. geologic and oceanographic) indicators of benthic habitats and ecosystems as proxies for biological communities and species diversity.    Using this approach, combinations of physical attributes of the seabed identify habitats that have been demonstrated to be effective as surrogates for the benthic communities that they typically support. Thus management priorities can be identified using seabed habitat maps as a guide.  The work of GeoHab demonstrates how knowledge of seabed properties can be employed to guide marine environmental management, marine resource management and conservation efforts.
Seafloor geomorphology is one of the more useful of the physical attributes of the seabed mapped and measured by GeoHab scientists.  Different geomorphic features (eg. submarine canyons, seamounts, atolls, fjords, etc.) are commonly associated with particular suites of habitats.  Knowledge of the geomorphology and biogeography of the seafloor has improved markedly over the past 10 years.  Using multibeam sonar, submarine features such as fjords, sand banks, coral reefs, seamounts, canyons and spreading ridges have been revealed in unprecedented detail.  The 57 case studies presented in this book represent a range of seabed geomorphic features where detailed bathymetric maps have been combined with seabed video and sampling to yield an integrated picture of the benthic communities that are associated with different types of benthic habitat.

Models of seabed sediment mobilisation by waves and currents over Australia’s
continental shelf environment are used to examine whether disturbance regimes exist in the
context of the intermediate disturbance hypothesis (IDH), whereby maximum biodiversity co -
incides with moderate levels of disturbance. Our study shows that it is feasible to model the
frequency and magnitude of seabed disturbance in relation to the dominant energy source
(wave-, tide- or cyclone-dominated shelf). Areas are mapped where the recurrence interval of
disturbance events is comparable to the rate of ecological succession, which meets criteria
defined for a disturbance regime. We focus our attention on high-energy, patch-clearing
events defined as exceeding the Shields (bed shear stress) parameter value of 0.25. Using
known rates of ecological succession for different substrate types (gravel, sand and mud), predictions
are made of the spatial distribution of a dimensionless ecological disturbance (ED)
index, given as: ED = FA(ES/RI), where ES is the ecological succession rate for different substrates,
RI is the recurrence interval of disturbance events and FA is the fraction of the frame
of reference (surface area) disturbed. Maps for the Australian continental shelf show small
patches of seafloor where ED indicates the potential existence of disturbance regimes (and
inferred greater biodiversity) distributed around the continent, on both the inner and outer
shelf. The patterns are different for wave-dominated (patches on the outer shelf trending parallel
to the coast), tide-dominated (patches crossing the middle-shelf trending normal to the
coast) and cyclone-dominated (large oval-shaped patches crossing all depths) shelf environments.
Only a small portion of the shelf (~10%) is characterised by a disturbance regime as
defined here.

Sedimentation in Torres Strait occurs in a shallow, tropical, epicontinental seaway, characterised by strong tidal currents superimposed upon seasonally-reversing, wind-driven circulation.  Depositional environments that have evolved in response to this hydrodynamic regime include mobile terrigenous and bioclastic dunes, seagrass beds, hermatypic coral reefs and expanses of inter-reefal areas, characterised by gravelly sandy mud deposits.  Maps of surficial sediment carbonate content indicate sources of terrigenous mud are the Fly River (in Papua New Guinea).  Current reworking of soft calcareous sediments results in their disintegration and the production of carbonate mud which is deposited in low energy environments.  Computer modelling together with current meter data collected in Torres Strait demonstrate that a zone of relatively high bottom stress, in which current speeds at 1m above the seabed attain a maximum speed >80 cm/sec, is located in two north-south trending belts that are associated with the Warrior Reefs and the Torres Strait islands.  An area of relatively high turbidity (>8 mg/l) "muddy water" is associated with this high energy zone.  In general, mud content increases with increasing distance from this maximum bottom stress area, giving rise to a facies succession similar to that found in other tidally dominated environments.  Seagrass beds, that are located within the maximum bottom stress zone, contain poorly sorted, muddy-gravelly-sand.

Australia's continental shelf covers some 2 million square kilometres, an area equal to about 25% of the continent's land surface.  Most of Australia's petroleum is derived from sedimentary deposits located on the continental shelf and the shelf seas contain valuable fisheries.  A growing tourist industry relies on a healthy marine environment, and yet this same environment receives millions of tonnes of eroded topsoil, fertiliser, sewage and industrial waste each year. 

What do we know about Australia's continental shelf, about its origin, history and geology?  What are the important factors controlling the functioning of its natural sedimentary systems?  This chapter attempts to answer these important questions as well as exploring the implications of shelf sedimentology for environmental monitoring and management.

Thoughts about reef growth are changing after the discovery of healthy corals in unlikely conditions off far north Queensland.
Geoscience Australia scientists discovered uncharted bryomol reefs and platforms of hard coral in murky, warm water near Mornington Island in the Gulf of Carpentaria on their recent Southern Surveyor voyage. They made the discovery in June using multibeam sonar to map underwater sandstorms and sediment movement from rivers entering the gulf. Finding living corals was an even bigger surprise because the turbid water and large sediment input would generally smother hard corals, and the surface water temperature of 28–30º C was too warm for coral survival.

Patterns of late Quaternary sedimentation at the junction of the Fly River and northern Great Barrier Reef (Australia) have been examined using high resolution seismics, sidescan sonar and vibro-coring.    Pleistocene deposits are characterised by fluvial channel and channel-fill sequences, flood plain soil deposits and eroded (karst) limestones.  These are overlain by Holocene facies, which grade from the rapidly accumulating (~5cm/yr) fine-grained terrigenous sediment of the Fly Delta to slowly accumulating (~0.02cm/yr) coarse bioclastic shelf carbonates.  High-energy shelf deposits are characterised by juxtaposed coral reefs, subtidal dunes and macrotidal, funnel-shaped estuaries.    The Fly River inputs ~100 million tonnes/yr of sediment which  is deposited within ~10km of the coast of Papua New Guinea.

Australia is an island continent extending from tropical to midlatitude waters with an Exclusive Economic Zone of some 8.6 million square kilometres. Its regional seas are exposed to climatological conditions ranging from the westerly Roaring Forties winds in the south, to monsoon and tropical cyclone conditions in the north. It also encompasses regions of extreme biodiversity, with 80 percent of southern temperate species endemic to the region.
The focus of marine research in Australia is becoming more interdisciplinary in response to factors such as the federal governments recent Oceans Policy, which emphasises sustainable development and ecological based management (Reichelt and McEwan 1999). However, historically there have been relatively few major interdisciplinary studies in Australian waters. Initiatives, such as the Leeuwin Current Interdisciplinary Experiment (Smith et al. 1991) might be more accurately described as multidisciplinary, with very limited effort devoted to integration. Interdisciplinary work that has been undertaken has tended to be concentrated in a few regions. Most notably in the Great Barrier Reef where there has been a strong interest in terrestrial inputs and larval exchange between reefs, in the Tasman Sea adjacent to Sydney where the East Australian Current has a strong influence on upwelling and primary productivity, and off the west coast where larval dispersion impacts recruitment levels in high value fisheries.
This review will begin in Section 2 with an overview of the broad-scale characteristics of Australia’s shelf seas, considering physical, chemical, biological, and sedimentological aspects of both its tropical and temperate regions. Interdisciplinary studies will be reviewed on a regional basis in Section 3, with emphasis on biophysical and sedimentological processes. Research directions and emerging scientific issues will then be discussed in Section 4.

The question as to whether geophysical data from habitats can be used to predict the occurrence of benthic biodiversity
is becoming more important with the increase in the use of Marine Protected Areas as tools for marine conservation.
To help answer this question and to better understand the relationship between sediment, geomorphology and benthos,
a multibeam sonar survey was conducted over two areas in the northern Great Barrier Reef–Gulf of Papua region.
Multivariate statistical analyses (cluster, multi-dimensional scaling and BIO-ENV procedure) of the physical and biological
datasets from both areas determined that the geophysical variables, slope and gravel percentage, were the best
predictors for megabenthos assemblage patterns. In conjunction with Geographic Information System (GIS) models of
the geomorphology and bathymetry, these geophysical variables were used to derive the spatial boundaries of benthic
habitats for each study area. A hierarchical method of benthic-habitat mapping to the Secondary Biotope and Biological
Facies levels was applied at the site (<10 km) scale. The combination of substrate type, sedimentary dynamics and physical
processes related to near-seabed currents appear to be the dominant control on the benthic communities in the
northern Great Barrier Reef–Gulf of Papua region. These results add confidence to the use of geophysical data from
seabed habitats, such as geology, sediment and morphology, as predictors for benthos distribution and thus provide a
basis for marine reserve selection.

Management of the marine environment in Australia’s Exclusive Economic Zone (EEZ) is addressed by an Oceans Policy
that was put forward by the government in 1998. The policy is being implemented through Regional Marine Plans
(RMPs), including the development of a network of representative Marine Protected Areas (MPAs). The southeast region
of Australia has been the first part of the EEZ to undergo regional marine planning (in 2003) and MPA development
processes are currently in progress.
Abiotic geoscience information has been used extensively to provide crucial supporting information to characterize
habitats and bioregions in order to inform managers of the diversity of major ecosystems which may be represented in
MPAs. In the southeast region, eleven “Broad Areas Of Interest” (BAOI) were first identified to help focus attention on
areas that contain the greatest diversity of geomorphological features and where an MPA could contribute the most to
biodiversity conservation objectives. These areas are then “sampled” to provide a candidate MPA that is comprehensive,
adequate and representative of bioregions, features, habitats and linked systems across the shelf, slope and abyssal
plain. Areas outside a BAOI may also be considered for sampling. The objective is to design an MPA network that meets
biodiversity conservation objectives while minimizing socio-economic impacts. For this reason, the specifications are
applied through stakeholder consultation, supported by a scientific reference panel. So far, options for two candidate
MPAs covering more than 40,000 square kilometres (the Murray and the Zeehan) have been identified.
An interpreted map of 21 categories of different seafloor geomorphic features was developed as a proxy for habitats in
the deep-water, continental slope and abyssal areas to support the selection of BAOI. Subsequent to the design of the
eleven BAOI and the two candidate MPAs, the geomorphic feature map was extended onto the shelf. Also, on the continental
shelf, a “seascape” map was produced using multivariate analysis, incorporating environmental variables.