Australian Coast Research Articles

Sea level rise and the increasing frequency of inundation in Australia’s most exposed estuary

The large tidal lake systems along the Southeast Australian coast are amongst the most vulnerable estuaries in Australia to the effects of sea level rise. In these lakes, reduced tide ranges compared with the ocean, in combination with modest flood extremes, have allowed development to occur in close vertical proximity to the current mean sea level. In this study, we examine water levels within Lake Macquarie, Australia’s most exposed estuary to sea level rise. We analyse water level data from the entrance channel and the lake to investigate recent changes to the frequency and duration of inundation or flooding of low-lying streets and examine the potential impacts of future rises in sea level. Our analysis shows that the numbers of days each year when water levels exceed those of low-lying streets, while subject to some variability, have increased significantly over recent decades. The increasing frequency of inundation is attributed to both mean sea level rise and an increase in tide range over the period of available data, which is thought to be associated with scour processes related to ongoing morphological adjustment to entrance training works undertaken over a century ago. Comparison of the projected behaviour of lake and open coast water levels under sea level rise shows the lake has significantly greater sensitivity to sea level rise. Projected inundation frequency for a given amount of sea level rise within the lake is double that of open coast sites, exposing infrastructure in the estuary to increasing risk of damage.

Future climate change accelerates the invasive rhythm of alien marine species: New insights into the invasive potential of the world's aquaculture species red drum Sciaenops ocellatus

In recent decades, an unprecedented frequency of red drum (Sciaenops ocellatus) escapes from sea cages (i.e., million tail level) has generated enormous pressure on local marine biodiversity and ecosystems. This study aimed to assess the distribution and shifts of hotspot fitness zones for S. ocellatus under global climate change and to identify the trophic levels in the coastal waters of China. The species distribution model (SDM) identified four hotspot fitness zones at a global scale located in the Atlantic Ocean along the Gulf of Mexico and Uruguayan coasts, and in the Pacific Ocean along the Chinese and Australian coasts. Under global warming and climate change, the most suitable habitat for S. ocellatus would expand (448,178.6 km2) and the centre of mass would shift northwards. Stable isotope δ15N and δ13C ratios indicated S. ocellatus has very high ecological competition, within a wide feeding range and high ecological position (δ15N: 10.84 ∼ 12.84 ‰, 11.61 ± 0.62 ‰; δ13C: −15.28 ∼ -17.25 ‰, −16.45 ± 0. 52 ‰) in the escape zone. The results suggested that a wide range of habitats, high reproductive capacity, and ecological niche competition conferred escaped S. ocellatus with a great ability to invade across regions on a global scale.

AUSTRALIAN MARINE RADIOCARBON RESERVOIR EFFECTS: ΔR ATLAS AND ΔR CALCULATOR FOR AUSTRALIAN MAINLAND COASTS AND NEAR-SHORE ISLANDS

ABSTRACTStudies of pre-bomb mollusks live-collected around the Australian coastline have concluded that near-shore marine radiocarbon reservoir effects are small and relatively uniform. These studies are based on limited samples of sometimes dubious quality representing only selective parts of Australia’s lengthy coastline. We systematically examine spatial variability in the marine radiocarbon reservoir effect (ΔR) through analysis of 292 live-collected mollusk samples across the Australian mainland coasts and near-shore islands subject to strict selection criteria. This study presents 233 new ΔR values combined with an evaluation of 59 previously published values. Results demonstrate significant spatial variability in marine radiocarbon reservoir effects across the study region. ΔR values range from 68 ± 24 14C years off the Pilbara region of Western Australia to –337 ± 46 14C years in the southern Gulf of Carpentaria in Queensland. Most sets of local values exhibit internal consistency, reflecting the dominant influence of regional oceanography, including depletion in ΔR values southwards along the eastern Australian coastline coincident with the East Australian Current. Anomalous values are attributed to inaccurate documentation, species-specific relationships with the carbon cycle and/or short-term fluctuations in marine radiocarbon activities. To account for the heterogeneous distribution of marine 14C, we recommend using a location specific ΔR value calculated using the Australian ΔR Calculator, available at: https://delta-r-calc.jcu.io/.

Records of leopard seals Hydrurga leptonyx ashore in South Australia, 2017–2022

The leopard seal Hydrurga leptonyx is one of five phocid species with a circumpolar distribution in the Southern Ocean. They do not breed on the Australian coast. We document records of 14 leopard seals (two collected specimens, 12 live sightings) in South Australia (SA) between November 2017 and November 2022, from Fowlers Bay to the mouth of the River Murray. We used records from the SA Museum, reports from coastal officers of SA Department for Environment and Water, and information from the public. All 14 seals were juvenile and most were in fair/thin body condition. Two collected specimens and two sighted animals showed evidence of blunt trauma. Stomachs contained fish remains and feathers, and one contained 21 semi-digested smooth toadfish Tetractenos glaber, a species which contains the toxin tetrodotoxin. Necropsies on two specimens involved gross, histopathological, and diagnostic assessment of pathogens, organs, and skin lesions. All records were between June and December, similar to the seasonal distribution reported previously in southern Australia. The 14 records over 5 years to 2022 averaged 2.8 per year, higher than during a previous study in SA that ran over three decades to October 2009 at 1.2 per year.

Characterising resting patterns of mother-calf humpback whale groups in a semi-enclosed embayment along the Australian east coast migration pathway

On migration from low latitude breeding grounds to high latitude feeding grounds, humpback whale mothers and calves spend time resting in coastal embayments. Unlike other areas where resting has been documented, Jervis Bay, on Australia’s east coast, is remote from both breeding and feeding grounds, and provides a unique opportunity to compare resting behaviour observed within a semi-enclosed embayment to observations offshore. Land-based, and UAV surveys were conducted in Jervis Bay in 2018, 2019, and 2021. We show that (i) a disproportionately high percentage of groups with a calf enter Jervis Bay during the southbound migration, (ii) travelling speeds are significantly slower in the Bay compared to offshore, indicating resting behaviour, and (iii) aerial observations highlight resting and nurturing behaviour. Subsequently, we conclude that Jervis Bay is an important area for resting mother-calf humpback whale groups. Comparison with reports of resting behaviour during migration in areas nearer the breeding grounds shows commonalities that characterise resting behaviour in mothers and calves. This characterisation will allow improved monitoring and management of humpback whales in nearshore embayments during a critical stage of calf development, particularly those with increased anthropogenic activities.

UPDATE ON THE STABILITY OF FOUR ESTUARIES ON THE AUSTRALIAN SOUTH-EASTERN SEABOARD

On the New South Wales, Australian east coast there are several estuaries with similar characteristics. Disconcertingly, the construction of training walls and jetties (breakwaters) at four of the medium-to-large sized estuaries have tripped their associated channel and lake (bay) systems from a long-term shoaling mode into an unstable scouring mode (Nielsen and Gordon 1980, 2008, 2017; Couriel et al. 2013. Field data and hydraulic theory confirm that such estuary entrance works have increased the tidal conveyance of entrance channels by modifying channel cross-sections, removing sand bars, extraneous littoral currents and associated sand movements that, previously, impeded ebb tide discharges and ocean tide forcing (Nielsen and Gordon 2017; Escoffier 1940).

The influence of oyster reefs and surrounding sediments on nitrogen removal – An in-situ study along the East coast of Australia

Oyster reefs play a crucial role in the removal of nitrogen (N) from aquatic systems by facilitating nutrient regeneration and denitrification, both in their tissues and shells and surrounding sediments. However, we still have a limited understanding about the contribution of each component of the reefs (e.g. oysters vs sediments) to N processes, and whether rates are dependent on site-specific characteristics. To address these knowledge gaps, we conducted an experiment across six oyster reefs along 1080 km of the Eastern Australian coast with different sediment characteristics. By using in-situ clear and dark incubation chambers, we assessed how benthic metabolism, nutrient and dinitrogen gas (N2) fluxes varied among the following treatments: ‘oysters’, ‘sediments’, and ‘sediments + oysters’ that were used to represent components of the whole reef habitat (i.e. reef matrix vs surrounding sediments vs the interaction among them, respectively), and sites. We found that during dark conditions and at siltier sites, N2 effluxes from oysters can be up to 23 times higher than sediments, while N2 effluxes from chambers with both sediments and oysters were similar to sediment treatments, and lower than oyster treatments. These results can be explained by sediment processes including nutrient assimilation by benthic microalgae and/or lower nutrient diffusion into interstitial space. Additionally, oyster treatments showed an uptake of nitrate (NO3-) that was likely converted into N2, whereas sediment treatments showed an overall release of NO3-. In dark conditions, ammonium (NH4+) fluxes remained consistent across treatments and sites, indicating that any exports from oyster excretion (in those treatments including oysters) were either counterbalanced by or comparable to exports from sediments. This study provides evidence that the crucial contribution of oyster reefs to N removal is dependent on interactions between reef components and environmental factors.

Sea level pressure response to the specification of eddy-resolving sea surface temperature in simulations of Australian east coast lows

Four east coast lows (ECLs) were simulated with the Weather Research and Forecast model to investigate the influence of the sea surface temperature (SST) distribution on the sea level pressure (SLP). Each ECL was simulated with two different SST datasets: the Bluelink SST field and NCEP skin temperature field. The former resolved eddies in the East Australian Current while the latter did not. The simulated SLP fields in the eddy-resolving SST runs were compared with those in the non-eddy-resolving SST runs. On time-scales of about 48 hours, higher SSTs were asso-ciated with lower SLPs. The spatial scale of the SLP response was similar to that of the ocean eddies, indicative of the rapidity and robustness of the response given the rapidly evolving conditions within the storms. On shorter time-scales, the SLP response to SST change can become substantially larger. The largest reductions in SLP in the eddy-resolving SST runs were associated with regions of deep atmospheric convection that warm the tropospheric column. These areas were shown to be related to the SST distribution with the greatest SLP reductions associated with convection over strong SST gradient regions. The landfall of a damaging convective mesoscale low pressure system on 8 June 2007 was also investigated. It was found that a region of strong SST gradients on the southern flank of a large warm ocean eddy was associated with lower pressures at the time of formation of this meso-low. In addition, the only case that simulated the low pressure at the correct time (albeit at not quite the correct location) was the eddy-resolved SST run. It was hy-pothesized that the development of this meso-low that impacted the coast around Newcastle, was enhanced because of the eddy-scale SST distribution at the time.

Life-history characteristics and mortality of the protogynous hermaphroditic frostback rockcod (Epinephelus bilobatus) from the eastern Indian Ocean

The frostback rockcod, Epinephelus bilobatus, is a small epinephelid (<50 cm total length) with a limited distribution in the tropical eastern Indian Ocean (i.e., north-western Australia and parts of Indonesia). Although its fishery harvest in Western Australia is low (<6 t year−1), its life history is not well known (i.e., reproductive biology, growth, and natural mortality) preventing assessment of its inherent vulnerability to overfishing. Samples of E. bilobatus were collected from ∼2000 km of the north-western Australian coast, comprising the Kimberley, Pilbara, and Gascoyne regions, between 2012 and 2022 to determine its life-history characteristics. Detailed histological analysis of gonads (n = 1460) identified that E. bilobatus is a monandric protogynous hermaphrodite. The length and age at which females matured was 278 mm LT and 2.5 years in the Pilbara region, and the lengths and ages at which they changed to males was 336 and 342 mm LT and 6.2 and 6.5 years in the Kimberley and Pilbara, respectively (i.e., less than 5% variation between regions). Based on histology, female E. bilobatus were in spawning condition in all months. However, the mean monthly gonadosomatic indices and proportions of developed/spawning females were highest (i.e., >0.95 and 40%, respectively) for 5 months of the year (i.e., January to April and September). Marginal increment analysis confirmed the annual formation of one opaque and one translucent zone in the sagittal otoliths of this species. Epinephelus bilobatus had a moderate longevity (∼20 years) and attained a larger mean length-at-age in the cooler southern Gascoyne region compared to the more northern Kimberley and Pilbara regions. Three values of natural mortality (M) were used to assess the sensitivity of fishing mortality (F) in the Kimberley and Pilbara commercial trap fisheries, with all point estimates of F < M, indicating that at the time of sampling, the harvest of this species over a long period (>20 years) was sustainable for these contemporary fisheries.

First Record of the Alien and Invasive Polychaete Laonome triangularis Hutchings &amp; Murray, 1984 (Annelida, Sabellidae) in Italian Waters

In recent years, the introduction of alien and invasive marine species in the Mediterranean Sea has rapidly increased. Laonome triangularis is a sabellid worm, native to the Australian coasts. Its first record in the Mediterranean Sea dates back to 2009 and, in this area, it is currently labeled as an allochthonous species. In the present work, we report the fìrst record of this polycheate in Italian waters and we provide some diagnostic features that are useful to identify the species.

Public holiday and long weekend mortality risk in Australia: A behaviour and usage risk analysis for coastal drowning and other fatalities

ObjectiveThis article aims to determine the impact of public holidays and long weekends on the risk of drowning and non-drowning deaths on the Australian coast. MethodsA retrospective case-control study using relative risk ratios and Z-scores to compare all unintentional fatalities on the Australian coast between 2004 and 2021 to a longitudinal representative survey sample of the Australian public and their coastal usage. ResultsOverall, the coastal mortality risk increased by 2.03 times for public holidays (95%CI = 1.77–2.33, p<0.0001) and 2.14 times by long weekends (95%CI = 1.85–2.48, p<0.0001). Children <16 years had the highest increased risk of death on public holidays (RR = 3.53, 95%CI = 1.98–6.31, p = 0.0005) and long weekends (RR = 2.90, 95%CI = 1.43–5.89, p = 0.011), while residents who were born overseas had a higher risk of death compared to those born in Australia. For public holidays, the greatest increase in risk was for swimming/wading and bystander rescues, while for long weekends, it was for scuba diving and snorkelling. ConclusionsPublic holidays and long weekends increase the risk of both drowning and non-drowning deaths on the Australian coast, which differed by demographics and activities. Implications for public healthThese results highlight periods of risk when targeted coastal safety messaging to high-risk demographics (particularly children and overseas-born residents), and provision of surf lifesaving resources can be increased.

A systems approach to biosecurity pays off: a case study investigating introduction pathways and interceptions of non-indigenous species at a biosecurity border

Introduction pathway studies generally describe the diverse routes by which non-indigenous species (NIS) can be introduced but rarely consider multiple introduction pathways occurring simultaneously. In this study, multiple pathways of NIS introduction were investigated during an industrial development on a remote island off the Australian coast. Fifteen introduction pathways were categorized in association with importing locality and the type of cargo they transported. The number and types of detection events for each introduction pathway were recorded during biosecurity inspections, cargo clearances, and surveillance conducted between 2009 and 2015. In total, more than 600,000 biosecurity inspections were completed, with 5,328 border detection events recorded constituting less than 1% of the biosecurity inspections. The border inspection events were classified as animals, plant material, soil, and organic matter, with 60% identified as dead or non-viable and 40% as alive. Of those detections, 2153 were classified as NIS, consisting of 659 identified species. Live NIS detected at the border constituted only 2% of the detections. Cargo vessel and inward-bound passenger numbers peaked during the major construction period and were associated with an increase in the number of live NIS detections. All introduction pathways have complexities, unique structural aspects, and niche areas that supported NIS in surviving the effects of treatment and evading detection during the mandatory compliance inspection. This study highlights that biosecurity incursions can be minimized if a systems approach is adopted to complement traditional and other biosecurity surveillance measures.

Growth and morphology of Critically Endangered green sawfish Pristis zijsron in globally important nursery habitats

Understanding growth rates and other basic life-history information of imperilled species is essential to assessing the extent of threats to a population, but often difficult due to limited access to study subjects. Here we used mark-recapture data to estimate growth rates of juvenile Critically Endangered green sawfish (Pristis zijsron) in a globally important nursery in the eastern Indian Ocean (Western Australia). Our results suggest that growth of juvenile sawfish in this part of the central Western Australian coast is significantly slower compared to populations on the north-eastern coast of Australia. Additionally, growth rates differed between nearby areas within the nursery region, potentially due to differential productivity or anthropogenic effects. Morphological relationships between total length, rostral length, mouth gape, and clasper length are presented, which will allow for greater accuracy in estimating biological parameters in this species, while updated information on size at maturity (> 3200 mm) and size at birth (approximately 750–900 mm) will help to clarify life-history parameters for this data-poor species. Furthermore, there were distinct differences in the number of rostral teeth of green sawfish between this eastern Indian Ocean population and other populations throughout their current distribution, indicating substantial genetic differentiation in this species globally. These results will help to accurately assess growth trajectories and potential impacts of fisheries and other threats to green sawfish. Additionally, results highlight the importance of assessing population-specific growth rates in threatened species and of considering potential long-term life-history impacts of anthropogenic developments and activities.

Are corals coming to a reef near you? Projected extension of suitable thermal conditions for hard coral communities along the east Australian coast

AbstractClimate change is driving the poleward redistribution of coral species, but the rate and magnitude of future range extensions within temperate regions are rarely quantified. A better understanding of the likely future distribution of corals is needed to anticipate the resulting social, economic and environmental implications. Here, we project the rate and magnitude of extensions of suitable thermal conditions for hard coral communities along the east Australian coastline, using data on coral community presence, in conjunction with historical and projected ocean temperatures. Our projections indicate that temperatures will be suitable for coral communities dominated by the subtropical coral Pocillopora aliciae, currently found off Sydney, to extend their range poleward by 80 (RCP 2.6) to 450 km (RCP 8.5) by 2100, corresponding to a rate of 0.9–5.0 km year−1. Similarly, thermal conditions will be such that diverse coral communities, such as those currently occurring in the Solitary Islands, may extend their range by 130 (RCP 2.6) to 580 km (RCP 8.5) by 2100, at a rate of 1.4–6.4 km year−1. These projections are similar to those forecast for coral species in other parts of the world. Newly establishing coral communities in temperate regions may provide a range of novel local economic opportunities, particularly for marine tourism.

CubeSat GPS Observation of Traveling Ionospheric Disturbances After the 2022 Hunga‐Tonga Hunga‐Ha'apai Volcanic Eruption and Its Potential Use for Tsunami Warning

AbstractMultiple passages of the atmospheric (Lamb) waves were recorded globally after the Hunga Tonga‐Hunga Ha'apai (HTHH) volcanic eruption on 15 January 2022. The waves perturbed the ionosphere and produced traveling ionospheric disturbances (TIDs) that were observed from the ground network of Global Positioning System (GPS) receivers. This study presents new observations of TIDs at higher altitudes (&gt;550 km) from CubeSat GPS tracking data. The satellite sampling along many CubeSat orbits enable to map broader spatio‐temporal patterns of the TID propagation compared to ground receivers. Due to the larger spatial coverage over a shorter period of time, the CubeSat measurements provide complementary information to stationary ground receivers. We found that the amplitude of the HTHH‐induced ionospheric perturbations at high altitudes (&gt;550 km) are as large as 10 TECU (1 TECU = 1016 electrons/m2) in slant total electron content between CubeSats and GPS satellites. The TIDs traveled along with the Lamb waves and were recorded by CubeSats above India 12 hr after the eruption and at the antipode of the eruption 16 hr after. These suggest that the ionospheric disturbances reached to the high altitudes and traveled globally as a speed of ∼350 m/s. The TIDs were also detected by CubeSats above the Australian continent several hours before the (conventional) tsunami made landfall on the Australian coasts. We discuss a new opportunity to study the upper ionosphere and its coupling with the solid Earth and to develop advanced monitoring systems of geohazards by the advent of low‐cost small satellite technology.

La Niña conditions influence interannual call detections of pygmy blue whales in the eastern Indian Ocean

Oceans across the globe are warming rapidly and marine ecosystems are changing as a result. However, there is a lack of information regarding how blue whales are responding to these changing environments, especially in the Southern Hemisphere. This is because long term data are needed to determine whether blue whales respond to variability in environmental conditions. Using over 16 years of passive acoustic data recorded at Cape Leeuwin, we investigated whether oceanic environmental drivers are correlated with the migration patterns of eastern Indian Ocean (EIO) pygmy blue whales off Western Australia. To determine which environmental variables may influence migration patterns, we modelled the number of acoustic call detections of EIO pygmy blue whale calls with broad and fine scale environmental variables. We found a positive correlation between total annual whale call detections and El Niño Southern Oscillation (ENSO) cycles and the Indian Ocean Dipole (IOD), with more whale calls detected during La Niña years. We also found that monthly whale call detections correlated with sea surface height around the hydrophone and chlorophyll-a concentration at a prominent blue whale feeding aggregation area (Bonney Upwelling) where whales feed during the summer before migrating up the west Australian coast. At the interannual scale, ENSO had a stronger relationship with call detections than IOD. During La Niña years, up to ten times more EIO pygmy blue whale calls were detected than in neutral or El Niño years. This is likely linked to changes in productivity in the feeding areas of the Great Australian Bight and Indian Ocean. We propose that in lower productivity years whales either skipped migration or altered their habitat use and moved further offshore from the hydrophones and therefore were not detected. The frequency and intensity of ENSO events are predicted to increase with climate change, which is likely to impact the productivity of the areas used by blue whales. These changes in productivity may affect the physical condition and reproductive success of individual whales. A reduction in reproductive success could have a significant impact on blue whale recovery from historical whaling and their ability to adapt to a changing environment.

Fantastic Flatworms and Where to Find Them: Insights into Intertidal Polyclad Flatworm Distribution in Southeastern Australian Boulder Beaches

There is a rapid and extensive decline of our marine biodiversity due to human impacts. However, our ability to understand the extent of these effects is hindered by our lack of knowledge of the occurrence and ecology of some species groups. One such group of understudied organisms are marine flatworms of the order Polycladida, a conspicuous component of southeastern Australia’s marine ecosystems that has received little attention over the years. Intertidal boulder beaches support a diverse range of polyclad flatworms in other countries, but the role of these environments in maintaining biodiversity is not well understood. In this study, we identified hotspots of flatworm occurrence by assessing the diversity and overall abundance of flatworms at boulder beaches along the southeast Australian coast. Bottle and Glass, Sydney Harbour, was found to be the most diverse site for flatworms. We also identified a higher occurrence of flatworms under large boulders and less exposed beaches and noted an increased presence of flatworms at higher latitudes. Probable influences on these patterns such as the requirement for shelter and protection are discussed. This study contributes to our knowledge of Australia’s coastal biodiversity and can be used to assist in the management and conservation of our marine environments.

A note on divergent mtDNA lineages of bottlenose dolphins from coastal waters of southern Australia

Bottlenose dolphins have a global distribution throughout tropical and temperate waters, both inshore and offshore. Many studies demonstrate the existence of at least two Tursiops species: Tursiops truncatus, consisting of inshore and offshore eco-types and T. aduncus, a coastal Indo-Pacific type known to extend south into temperate waters down the east coast of Australia. To clarify the taxonomic status of two populations (Port Phillip Bay and Gippsland Lakes) of coastal bottlenose dolphins along Australia’s south coast (Victoria), a 346bp region of the mitochondrial-DNA (mtDNA) control region was sequenced from ten individuals and they were incorporated into phylogenetic analyses involving published sequences of other Tursiops spp., Stenella spp. and Delphinus spp., found worldwide. Both neighbour-joining and maximum parsimony trees place Victorian coastal haplotypes in a highly-supported group separate to those from the other dolphins, including those from the southern part of the Australian eastern coast. Victorian haplotypes are least divergent from T. truncatus (average 5.5%) and most divergent from T. aduncus (9.1%), with intermediate levels of divergence from Stenella and Delphinus spp. These data suggest that the Victorian coastal dolphins, similar to other world-wide coastal populations, are genetically unique, long isolated and therefore likely to be locally adapted. This has important implications for management and conservation.

Whale catches from 19th century shore stations in Western Australia

This paper presents historical data from 19th century shore whaling stations along the Western Australian coast, complementing data already presented in an earlier 1985 analysis. In particular, catch records of the Castle Rock whaling station, Geographe Bay, Western Australia, for the period 1846–53 together with other contemporary records indicate that humpback whales (Megaptera novaeangliae) comprised the majority of the colonial shore whalers’ catch. It is suggested that this could have been a result of a significant presence of American whale ships in the region in the early 1840s, which had presumably already reduced southern right whale (Eubalaena australis) numbers by the time these detailed colonial records were kept.

Marine Natural Products from Flora and Fauna of the Western Australian Coast: Taxonomy, Isolation and Biological Activity.

Marine natural products occurring along the Western Australian coastline are the focus of this review. Western Australia covers one-third of the Australian coast, from tropical waters in the far north of the state to cooler temperate and Antarctic waters in the south. Over 40 years of research has resulted in the identification of a number of different types of secondary metabolites including terpenoids, alkaloids, polyketides, fatty acid derivatives, peptides and arsenic-containing natural products. Many of these compounds have been reported to display a variety of bioactivities. A description of the compound classes and their associated bioactivities from marine organisms found along the Western Australian coastline is presented.