Southern Australian Coast Research Articles

Carriage of antibiotic resistant bacteria in endangered and declining Australian pinniped pups.

The rapid emergence of antimicrobial resistance (AMR) is a major concern for wildlife and ecosystem health globally. Genetic determinants of AMR have become indicators of anthropogenic pollution due to their greater association with humans and rarer presence in environments less affected by humans. The objective of this study was to determine the distribution and frequency of the class 1 integron, a genetic determinant of AMR, in both the faecal microbiome and in Escherichia coli isolated from neonates of three pinniped species. Australian sea lion (Neophoca cinerea), Australian fur seal (Arctocephalus pusillus doriferus) and long-nosed fur seal (Arctocephalus forsteri) pups from eight breeding colonies along the Southern Australian coast were sampled between 2016–2019. DNA from faecal samples (n = 309) and from E. coli (n = 795) isolated from 884 faecal samples were analysed for class 1 integrons using PCRs targeting the conserved integrase gene (intI) and the gene cassette array. Class 1 integrons were detected in A. p. doriferus and N. cinerea pups sampled at seven of the eight breeding colonies investigated in 4.85% of faecal samples (n = 15) and 4.52% of E. coli isolates (n = 36). Integrons were not detected in any A. forsteri samples. DNA sequencing of the class 1 integron gene cassette array identified diverse genes conferring resistance to four antibiotic classes. The relationship between class 1 integron carriage and the concentration of five trace elements and heavy metals was also investigated, finding no significant association. The results of this study add to the growing evidence of the extent to which antimicrobial resistant bacteria are polluting the marine environment. As AMR determinants are frequently associated with bacterial pathogens, their occurrence suggests that these pinniped species are vulnerable to potential health risks. The implications for individual and population health as a consequence of AMR carriage is a critical component of ongoing health investigations.

Late Eocene–early Miocene evolution of the southern Australian subtropical front: a marine palynological approach

Abstract. Improvements in our capability to reconstruct ancient surface-ocean conditions based on organic-walled dinoflagellate cyst (dinocyst) assemblages from the Southern Ocean provide an opportunity to better establish past position, strength and oceanography of the subtropical front (STF). Here, we aim to reconstruct the late Eocene to early Miocene (37–20 Ma) depositional and palaeoceanographic history of the STF in the context of the evolving Tasmanian Gateway as well as the potential influence of Antarctic circumpolar flow and intense waxing and waning of ice. We approach this by combining information from seismic lines (revisiting existing data and generating new marine palynological data from Ocean Drilling Program (ODP) Hole 1168A) in the western Tasmanian continental slope. We apply improved taxonomic insights and palaeoecological models to reconstruct the sea surface palaeoenvironmental evolution. Late Eocene–early Oligocene (37–30.5 Ma) assemblages show a progressive transition from dominant terrestrial palynomorphs and inner-neritic dinocyst taxa as well as cysts produced by heterotrophic dinoflagellates to predominantly outer-neritic/oceanic autotrophic taxa. This transition reflects the progressive deepening of the western Tasmanian continental margin, an interpretation supported by our new seismic investigations. The dominance of autotrophic species like Spiniferites spp. and Operculodinium spp. reflects relatively oligotrophic conditions, like those of regions north of the modern-day STF. The increased abundance in the earliest Miocene of Nematosphaeropsis labyrinthus, typical for modern subantarctic zone (frontal) conditions, indicates a cooling and/or closer proximity of the STF to the site . The absence of major shifts in dinocyst assemblages contrasts with other records in the region and suggests that small changes in surface oceanographic conditions occurred during the Oligocene. Despite the relatively southerly (63–55∘ S) location of Site 1168, the rather stable oceanographic conditions reflect the continued influence of the proto-Leeuwin Current along the southern Australian coast as Australia continued to drift northward. The relatively “warm” dinocyst assemblages at ODP Site 1168, compared with the cold assemblages at Antarctic Integrated Ocean Drilling Program (IODP) Site U1356, testify to the establishment of a pronounced latitudinal temperature gradient in the Oligocene Southern Ocean.

It Often Howls More than It Chugs: Wind versus Ship Noise Under Water in Australia’s Maritime Regions

Marine soundscapes consist of cumulative contributions by diverse sources of sound grouped into: physical (e.g., wind), biological (e.g., fish), and anthropogenic (e.g., shipping)—each with unique spatial, temporal, and frequency characteristics. In terms of anthropophony, shipping has been found to be the greatest (ubiquitous and continuous) contributor of low-frequency underwater noise in several northern hemisphere soundscapes. Our aim was to develop a model for ship noise in Australian waters, which could be used by industry and government to manage marine zones, their usage, stressors, and potential impacts. We also modelled wind noise under water to provide context to the contribution of ship noise. The models were validated with underwater recordings from 25 sites. As expected, there was good congruence when shipping or wind were the dominant sources. However, there was less agreement when other anthropogenic or biological sources were present (i.e., primarily marine seismic surveying and whales). Off Australia, pristine marine soundscapes (based on the dominance of natural, biological and physical sound) remain, in particular, near offshore reefs and islands. Strong wind noise dominates along the southern Australian coast. Underwater shipping noise dominates only in certain areas, along the eastern seaboard and on the northwest shelf, close to shipping lanes.

A Parametric Study of Wave Energy Converter Layouts in Real Wave Models

Ocean wave energy is a broadly accessible renewable energy source; however, it is not fully developed. Further studies on wave energy converter (WEC) technologies are required in order to achieve more commercial developments. In this study, four CETO6 spherical WEC arrangements have been investigated, in which a fully submerged spherical converter is modelled. The numerical model is applied using linear potential theory, frequency-domain analysis, and irregular wave scenario. We investigate a parametric study of the distance influence between WECs and the effect of rotation regarding significant wave direction in each arrangement compared to the pre-defined layout. Moreover, we perform a numerical landscape analysis using a grid search technique to validate the best-found power output of the layout in real wave models of four locations on the southern Australian coast. The results specify the prominent role of the distance between WECs, along with the relative angle of the layout to dominant wave direction, in harnessing more power from the waves. Furthermore, it is observed that a rise in the number of WECs contributed to an increase in the optimum distance between converters. Consequently, the maximum exploited power from each buoy array has been found, indicating the optimum values of the distance between buoys in different real wave scenarios and the relative angle of the designed layout with respect to the dominant in-site wave direction.

Diversity and Distribution of Escherichia coli in Three Species of Free-Ranging Australian Pinniped Pups

Anthropogenic activities and pollution are impacting marine environments globally. This has resulted in increasing numbers of human-associated phylotypes of Escherichia coli, an indicator of faecal contamination, being found in both aquatic environments and upper trophic marine mammals that are considered sentinels for marine health. The objective of this study was to determine the presence and diversity of E. coli in pups of three species of free-ranging pinnipeds in Australia. Faecal samples (n = 964) were collected between 2016 and 2019 from Australian sea lion (Neophoca cinerea), Australian fur seal (Arctocephalus pusillus doriferus) and long-nosed fur seal (Arctocephalus forsteri) pups from eight breeding colonies extending along the Southern Australian coast. E. coli were isolated from 842 (87.3%) samples and molecular screening was applied to assign isolates to E. coli phylotypes and sub-types. The human associated E. coli phylotype B2 was the most frequently isolated in all species at seven of the eight colonies, with 73.7% of all E. coli isolates belonging to this phylotype. Phylotype distribution did not differ significantly within or across species, breeding colonies or breeding seasons. Further analysis of B2 isolates into sub-types showed a significant difference in sub-type distribution across breeding seasons at two colonies (Seal Rocks and Cape Gantheaume). The predominance of the B2 phylotype could indicate that all colonies are exposed to similar levels of anthropogenic pollution. This widespread occurrence of the human-associated E. coli phylotypes highlights the imperative for ongoing monitoring and surveillance of microbes in both the marine environment and sentinel species.

Southern right whales (Eubalaena australis) return to a former wintering calving ground: Fowlers Bay, South Australia

AbstractSouthern right whales (SRW), Eubalaena australis, have reoccupied historically important winter habitat ranges (calving grounds) in recent years along the southern Australian coast. Here we present findings of increased abundance of SRW at Fowlers Bay, South Australia, a previous shore‐based whaling station. This study investigates: SRW inter‐ and intraseasonal trends in relative abundance; changes to the relative proportion of the southwestern subpopulation represented by SRW at Fowlers Bay; distribution; and occupancy. Sighting and photo identification data were collected during annual aerial (1993–2016) and vessel surveys (2014–2016). The total number of female and calf pairs was 3 during 1993–2003 and 63 during 2004–2014. Despite high variability in annual relative abundance, the rate of mean increase from 1993 to 2016 (29.0%/yr, 95% CI = 0, 54.2) exceeded the maximum biological rate for the species (6%–7%/yr). Peak relative abundance was recorded in July and August. SRW at Fowlers Bay represent an increasing proportion of the southwestern subpopulation (range = 0.9%–7.4%). Mean occupancy was 23 d (range = 1–75) for female and calf pairs and 2 d (range = 1–15) for unaccompanied adults. Reduced sightings in 2015 and 2016 demonstrate plasticity in SRW abundance at Fowlers Bay. Research into the movement and connectivity of SRW is needed to understand drivers of habitat dispersal in Australia.

Dispersion of long-nosed fur seals (Arctocephalus forsteri) determined by tagging

Long-nosed fur seals (Arctocephalus forsteri) were tagged as pups in colonies on Kangaroo Island, South Australia in eight consecutive pupping seasons from 1988–89 to 1995–96. Thirty-nine tagged animals were sighted on the southern Australian coast, being 0.89% of those tagged. They were aged from 9 months to 14 years 6 months, with half in their second and third years. Most records (88%) were of animals that moved eastwards. The most distant records were from Sydney in the east (1700 km), south of Tasmania in the south (1240 km) and Head of Bight in the west (700 km). One animal was seen twice, both times on the north coast of Kangaroo Island, once underwater and two years later ashore. Satellite telemetry studies of juvenile A. forsteri from Kangaroo Island showed that they typically forage in pelagic waters ~1000 km further south in association with the subtropical front. The study reported here shows that some animals tagged as pups disperse widely as juveniles around the southern Australian coast. The possibility of genetic interchange between breeding colonies is suggested by sightings of three tagged females aged 4 years and older at non-natal colonies.

Pygmy blue and Antarctic blue whale presence, distribution and population parameters in southern Australia based on passive acoustics

Passive acoustic recorders set around Australia since 2004 have been used to study blue whales. Calls from New Zealand pygmy blue whales occur predominantly eastward of Bass Strait (145.8° E), calls from Eastern Indian Ocean pygmy blue whales (EIO PB) west of Bass Strait, while Antarctic blue whale calls occur along the entire southern Australian coast. The only location all calls have been detected within a short space of time in the same season is Bass Strait, where inter-species mixing commonly occurs. The EIO PB shows three migratory stages: "southbound" from November to January during which whales travel down the Western Australian coast; "southern Australian" where animals spread across the Indian and Southern Oceans spanning longitudes from 74° to 146° E down to at least a latitude of 55° S searching for food and feeding; then a northern migration where they return north to Indonesian waters post April-August. Along the southern Australian coastline EIO PB whales are more often detected towards the east, favouring an area where late summer to autumn upwelling occurs mostly over ~ 134-145° E longitude. Receivers on the shelf break south of Portland (141.2° E) showed 10–181 times greater EIO PB whale calling when integrated over their three month season than at sites located around the Great Australian Bight to the west. Within a season the Portland site did not show consistency of EIO PB whale presence or number of calling individuals, but when the number of calling individuals was integrated across a season and correlated with an upwelling index of seasonally integrated seabed water temperature across seven seasons, the upwelling index predicted 83% of the seasonal variance in whale presence. The strength of this correlation will be reduced by population growth of whales. By correcting EIO PB whale call rates for a variety of population growth rate values, we found a 4.3% growth rate for the population proportion visiting the Portland area, gave the maximum regression, correlation coefficient of r2= 90%. Time averaged levels of squared pressure produced at the upper chorus frequency of the Antarctic blue whale z-call and received via deep sound channel propagation at Portland showed a 12.6% increase rate. This is indicative of population growth rate for Antarctic blue whales using waters south of Australia, although the value of using pressure squared in this fashion and the assumptions underlying the technique need to be explored.

A Long-Term Overshooting Convective Cloud-Top Detection Database over Australia Derived from MTSAT Japanese Advanced Meteorological Imager Observations

ABSTRACTA 10-yr geostationary (GEO) overshooting cloud-top (OT) detection database using Multifunction Transport Satellite (MTSAT) Japanese Advanced Meteorological Imager (JAMI) observations has been developed over the Australian region. GEO satellite imagers collect spatially and temporally detailed observations of deep convection, providing insight into the development and evolution of hazardous storms, particularly where surface observations of hazardous storms and deep convection are sparse and ground-based radar or lightning sensor networks are limited. Hazardous storms often produce one or more OTs that indicate the location of strong updrafts where weather hazards are typically concentrated, which can cause substantial impacts on the ground such as hail, damaging winds, tornadoes, and lightning and to aviation such as turbulence and in-flight icing. The 10-yr OT database produced using an automated OT detection algorithm is demonstrated for analysis of storm frequency, diurnally, spatially, and seasonally relative to known features such as the Australian monsoon, expected regions of hazardous storms along the southeastern coastal regions of southern Queensland and New South Wales, and the preferential extratropical cyclone track along the Indian Ocean and southern Australian coast. A filter based on atmospheric instability, deep-layer wind shear, and freezing level was used to identify OTs that could have produced hail. The filtered OT database is used to generate a hail frequency estimate that identifies a region extending from north of Brisbane to Sydney and the Goldfields–Esperance region of eastern Western Australia as the most hail-prone regions.

Phylogenetic placement and redescription of Aleochara blackburni Bernhauer & Scheerpeltz, 1926 (Coleoptera: Staphylinidae) from coastal Australia

Aleochara blackburni Bernhauer & Scheerpeltz (Aleocharinae) is a little-known coastal rove beetle, not studied since a specimen was collected from coasts in Port Lincoln, South Australia, in 1888. We report the discovery of additional specimens, which were collected at sites distributed between the central-east and south-east coasts of Tasmania, Australia. Habitus photographs, a redescription, host records and illustrations of diagnostic characters are provided. To investigate the phylogenetic placement of A. blackburni and taxonomic problems within the Emplenota and Triochara clade, we studied 34 populations of 13 coastal and one inland species and generated a molecular phylogeny of the genus Aleochara Gravenhorst based on three partial mitochondrial genes (COI, tRNA leucine and COII). Our results showed that A. blackburni was the sister group of the bilineata clade + curtula clade and suggested that A. curtidens Klimaszewski (Vancouver, Canada) and A. trisulcata Weise (Chiba, Japan) used in a previous study were misidentifications of A. fucicola Sharp and A. zerchei (Assing), respectively. Five independent origins of specialisation to coastal habitat in the genus Aleochara (clades A–E) are hypothesised, of which A. blackburni has independently colonised the Southern Australian coast (clade E).

Trapped planetary (Rossby) waves observed in the Indian Ocean by satellite borne altimeters

Abstract. Using 20 years of accurately calibrated, high-resolution observations of sea surface height anomalies (SSHAs) by satellite borne altimeters, we show that in the Indian Ocean south of the Australian coast the low-frequency variations of SSHAs are dominated by westward propagating, trapped, i.e., non-harmonic, Rossby (Planetary) waves. Our results demonstrate that the meridional-dependent amplitudes of the SSHAs are large only within a few degrees of latitude next to the southern Australian coast while farther in the ocean they are uniformly small. This meridional variation of the SSHA signal is typical of the amplitude structure in the trapped wave theory. The westward propagation speed of the SSHA signal is analyzed by employing three different methods of estimation. Each one of these methods yields speed estimates that can vary widely between adjacent latitudes but the combination of at least two of the three methods yields much smoother variation. The estimates obtained in this manner show that the observed phase speeds at different latitudes exceed the phase speeds of harmonic Rossby (planetary) waves by 140 to 200 % (which was also reported in previous studies). In contrast, the theory of trapped Rossby (planetary) waves in a domain bounded by a wall on its equatorward side yields phase speeds that approximate more closely the observed phase speeds in the study area.

A Victorian emigrant: first observation and range extension of the nudibranch Tenellia catachroma (Burn, 1963) in Western Australia (Mollusca: Gastropoda)

The southwest coast of Western Australia is heavily influenced by the south-flowing Leeuwin Current. In summer, the current shifts and the north-flowing Capes Current delivers water from the south to nearshore environments and with it a supply of larvae from cooler waters. The nudibranch Tenellia catachroma (Burn, 1963) was considered restricted to Victorian waters; however, its discovery in eastern South Australia in 2013 revealed its capacity to expand its range west. In March 2017 a single individual was observed in shallow subtidal waters at Cape Peron, Western Australia, some 2000 km to the west of its previous range limit. Moreover, its distribution has extended northwards, possibly aided by the Capes Current, into a location of warming. This observation significantly increases the range for this Victorian emigrant to encompass most of the southern Australian coast, and also represents an equatorward shift at a time when the reverse is expected.

Differing environmental drivers of settlement across the range of southern rock lobster (Jasus edwardsii) suggest resilience of the fishery to climate change

AbstractTemporal and spatial trends in settlement of the southern rock lobster, Jasus edwardsii, were examined to identify the influence of environmental variables over different spatial scales. Settlement data were collected from 1994 to 2011 along the Southern Australian and New Zealand coasts. We identified common settlement trends at a regional scale (100–500 km): the magnitude of settlement at sites from South Australia (SA) and Victoria (VIC) were similar, but different to sites in Tasmania (TAS). In New Zealand, three spatial regions were identified: northern (NNZ), middle (MNZ) and southern regions (SNZ). Higher settlement in SA, VIC and MNZ occurred in years with higher rainfall and storms in spring and El Niño conditions. In TAS and SNZ, higher settlement occurred during La Niña conditions. These results suggest that settlement over regional scales is modulated by oceanic processes, but outcomes vary between regions. At a local scale, a higher wave period and wind relaxation were relatively more important than the sea surface temperature (SST) in SA and VIC. In TAS, the current velocity also influenced the strength of settlement. However, much of the local settlement variability was not explained by the models suggesting that settlement in J. edwardsii is a complex process where larval behaviour, biological factors and oceanographic processes interact over different scales. The apparently complex processes affecting settlement showed that environmental conditions that reduced settlement strength in one region of the fishery often increased settlement strength in other regions. This could provide resilience to climate change at the stock level.

Unexpected absence of genetic separation of a highly diverse population of hookworms from geographically isolated hosts

The high natal site fidelity of endangered Australian sea lions (Neophoca cinerea) along the southern Australian coast suggests that their maternally transmitted parasitic species, such as hookworms, will have restricted potential for dispersal. If this is the case, we would expect to find a hookworm haplotype structure corresponding to that of the host mtDNA haplotype structure; that is, restricted among geographically separated colonies. In this study, we used a fragment of the cytochrome c oxidase I mitochondrial DNA (mtDNA) gene to investigate the diversity of hookworms (Uncinaria sanguinis) in N. cinerea to assess the importance of host distribution and ecology on the evolutionary history of the parasite. High haplotype (h=0.986) and nucleotide diversity (π=0.013) were seen, with 45 unique hookworm mtDNA haplotypes across N. cinerea colonies; with most of the variation (78%) arising from variability within hookworms from individual colonies. This is supported by the low genetic differentiation co-efficient (GST=0.007) and a high gene flow (Nm=35.25) indicating a high migration rate between the populations of hookworms. The haplotype network demonstrated no clear distribution and delineation of haplotypes according to geographical location. Our data rejects the vicariance hypothesis; that female host natal site fidelity and the transmammary route of infection restrict hookworm gene flow between N. cinerea populations and highlights the value of studies of parasite diversity and dispersal to challenge our understanding of parasite and host ecology.

Tasman Leakage of intermediate waters as inferred from Argo floats

AbstractWe use Argo float trajectories to infer ocean current velocity at the sea surface and 1000 dbar near Australia. The East Australian Current flows southward along the east coast of Australia at both surface and intermediate levels, but only the intermediate waters leak round the southern tip of Tasmania and cross the Great Australian Bight. We calculate the transport of Antarctic Intermediate Water (AAIW) between the southern Australian coast and the Antarctic Circumpolar Current (ACC) as the velocity at 1000 dbar times the layer thickness. Between March 2006 and December 2012, the Eulerian AAIW transport through 147°E ranges between 0 and 12.0 sverdrup (Sv). The mean Tasman Leakage of intermediate waters from the Pacific Ocean into the Indian Ocean, obtained using all Argo data until March 2013, is 3.8 ± 1.3 Sv. The mean intermediate water transport into the Indian Ocean through 115°E increases to 5.2 ± 1.8 Sv due to contributions from the westward recirculation of ACC waters.

Records of vagrant phocid seals (family Phocidae) in South Australia

Five species of phocid seal of the Southern Ocean and Antarctica come ashore occasionally on the southern Australian coast but do not breed there. We document records (specimens and sightings) of visits to South Australia (SA) by southern phocids from 1883 until August 2011. We used records from the SA Museum, reports from coastal officers of SA Department of Environment and Natural Resources (DENR), the DENR fauna database, information from the public, the literature and newspapers. Thirty-six southern elephant seal records included two births, in November 1932 and October 1986. The latter pup suckled for 20 days and then stayed ashore for eight weeks; both are similar to average durations at Macquarie Island. Of 33 dated records, 31 were between August and April, when elephant seals at Macquarie Island (the closest breeding site) are ashore to breed or moult. A recognisable male on Kangaroo Island has been sighted often over 10 years to 2010. Of the ice-breeding species, there were 54 leopard seal records. All of 40 dated records were between June and December, with the maximum (12) in August, similar to the seasonal distribution in Tasmania. There were five records of crabeater seals, one of a Ross seal, and one of a Weddell seal.

The Identification of Submerged Skeletonized Remains

Examination was undertaken of skeletonized remains contained within 2 rubber boots dredged by a fishing boat from a depth of 145 m, approximately 185 km off the southern Australian coast in the Great Australian Bight. The boots had been manufactured in Australia in July 1993 and were of a type commonly used by local fishermen. Examination of the lower legs and feet revealed well-preserved bones with arthritic changes in keeping with an older male. DNA analyses using reference samples taken from relatives of fishermen who had disappeared in the area resulted in the identification of the victim as a 52-year-old prawn fisherman who had been swept off a boat over a decade earlier. DNA stability had been maintained by the low light, cold temperatures, and alkaline pH of the ocean floor. Integration of pathologic, anthropologic, and biologic analyses with police investigations enabled a positive identification to be made despite the unusual nature of the location of the remains and the time lapse since the disappearance of the victim.

Species delimitation and distribution in Aporometra (Crinoidea:Echinodermata): endemic Australian featherstars

Aporometra Clark, 1938, which belongs to the monotypic Aporometridae, is a crinoid genus endemic to temperate Australian waters. It has been described as being ‘viviparous’ and is among the smallest of comatulids. The small size of specimens, and poor morphological justifications for specific diagnoses have created uncertainty over the number of species in the genus and their distributions. This study identified a suite of characters using data from scanning electron microscopy and mtDNA sequencing (CO1 and ND2) to assess the number of species of Aporometra. Specimens were obtained from museums and collected from Western Australia, South Australia, Victoria and New South Wales. Type material was also examined when possible. Phylogenetic hypotheses were generated using maximum parsimony-based analyses of the separate and combined datasets. The results support the monophyly of Aporometra and the presence of two species, Aporometra wilsoni (Bell, 1888) and Aporometra occidentalis A. H. Clark, 1938, along the southern Australian coast. The status of the third nominal species, Aporometra paedophora (H. L. Clark, 1909), remains to be resolved, but it may be a junior synonym of A. wilsoni. Morphological diagnoses are reviewed. Aporometra occidentalis was only found in Western Australia, while A. wilsoni was found from Western Australia to Victoria. Phylogeographic differentiation between the western and southern populations of A. wilsoni is briefly discussed.

Desiccation tolerance of the introduced marine green alga Codium fragile ssp. tomentosoides – clues for likely transport vectors?

The invasive marine green macroalga Codium fragile ssp. tomentosoides is now considered to be an introduced marine pest along the northwest Atlantic and southern Australian coasts. International or domestic translocation of C. fragile ssp. tomentosoides is usually attributed to the fouling of ship hulls or shellfish, particularly oysters. A likely domestic vector is shipboard transport, involving the translocation of whole thalli or fragments entangled in fishing nets, ropes, etc. that are then released in a previously unaffected area. Here we investigated the survival of C. fragile ssp. tomentosoides under emersed conditions, simulating shipboard transport. C. fragile ssp. tomentosoides was able to survive periods of emersion of up to 90 days in high relative air humidity. Net photosynthesis remained positive at about 50% of the rates of submersed control thalli. After 2 days of emersion and 4 days of rehydration under submersed conditions thalli recover to their initial net photosynthesis rates. Hence, C. fragile ssp. tomentosoides is likely to survive long shipboard journeys entrapped in fishing nets, anchor wells or other protected, high-humidity areas of a vessel. Furthermore, C. fragile ssp. tomentosoides may survive emersion on an exposed deck during short trips, especially in cooler conditions such as at night. The incursion sites of C. fragile ssp. tomentosoides in Australia are generally in modified environments, often associated with shipping-related infrastructure such as wharves, jetties, rip rap, and moorings.

The 5500‐km‐long boundary flow off western and southern Australia

The path of the shelf edge flow off southwestern Australia is documented using results from satellite altimetry and sea surface temperature (SST) and a climatogical in situ analysis. During Austral winter a continuous current is shown to extend from its origin at North West Cape to the southern tip of Tasmania, a distance of 5500 km. Satellite SST observations and surface buoy tracks confirm the location and continuity of the current trajectory. While the Leeuwin Current is forced by the strong alongshore pressure gradient associated with the meridional portion of the western Australian coastal boundary, our results suggest that the essentially zonal shelf edge flow along the southern Australian coast arises from the setup of coastal sea level by onshore Ekman flow driven by the winter westerly wind and possibly a further alongshore pressure gradient. The timing of these two different forcing mechanisms means that the west coast pressure gradient delivers the Leeuwin Current to the south coast just as the winds reverse and are thus able to maintain the eastward passage of the current. The shelf edge flow consists of two main water masses. A low‐salinity, warm water type of tropical origin associated with the Leeuwin Current and a high‐salinity, warm water inflow formed on the western end of the Great Australian Bight continental shelf. A naming convention is proposed, the Leeuwin Current representing flow from North West Cape to the Great Australian Bight (GAB); the South Australian Current, between the eastern GAB and western Bass Strait; and the Zeehan Current off western Tasmania.