Rottnest Island Research Articles

Molecular characterization of native Australian trypanosomes in quokka (Setonix brachyurus) populations from Western Australia

The quokka, Setonix brachyurus, is a vulnerable, small marsupial endemic to Western Australia. Blood samples were collected from quokkas from three different geographical locations; Two Peoples Bay, Bald Island and Rottnest Island. The overall prevalence of trypanosomes by nested PCR at the 18S ribosomal RNA gene was 57.3% (63/110) with prevalences of 91.4%, 85.3% and 4.9% respectively for Two Peoples Bay, Bald Island and Rottnest Island. Phylogenetic analysis conducted on 47 18S PCR positives identified two Trypanosoma copemani genotypes, with T. copemani genotype B, the most prevalent genotype infecting quokka populations from the three locations with an overall prevalence of 51.8% (24/47) compared to 34% for T. copemani genotype A (16/47). The overall prevalence of mixed T. copemani genotype A and B infections was 14.9% (7/47). Phylogenetic analysis of 26 quokka isolates at the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) locus, largely supported the 18S analysis but identified a mixed infection in one quokka isolate (Q4112-4117 from Two Peoples Bay). T. copemani genotype B has previously only been isolated from quokkas and the Gilbert's potoroo whereas T. copemani genotype A has a wide host range and may be pathogenic. Further work is required to determine the clinical impact of T. copemani on marsupial populations.

Remote-Sensed Mapping of Sargassum spp. Distribution around Rottnest Island, Western Australia, Using High-Spatial Resolution WorldView-2 Satellite Data

ABSTRACT Hoang, T.C.; O'Leary, M.J., and Fotedar, R.K., 2016. Remote-sensed mapping of Sargassum spp. distribution around Rottnest Island, Western Australia, using high-spatial resolution WorldView-2 satellite data. Satellite remote sensing is one of the most efficient techniques for marine habitat studies in shallow coastal waters, especially in clear waters where field observations can be easily carried out. However, such in situ observations have certain limitations: they are time consuming, have a limited ability to capture spatial variability, and require an interdisciplinary approach between marine biologists and remote-sensing specialists. The main objective of this study was to survey and map Sargassum beds around Rottnest Island, Western Australia, through a combination of high spatial resolution WorldView-2 imagery, using a validated depth invariant index model for water-column correction, and in-field observations. The combination of field survey data and four classification methods resulted in...

A state of non-specific tension in living matter? Stress in Australian animals

Evidence of stress responses in Australian animals is reviewed through a series of case studies involving desert frogs and lizards, small carnivorous marsupials, desert wallabies, a dwarf kangaroo species, the quokka wallaby and a small nectarivorous bird. An operational definition of stress as “the physiological resultant of demands that exceed an animal’s homeostatic capacities” is used to identify instances of stress responses in the field, and to gauge their intensity. Clear evidence of stress responses is found in small dasyurid marsupial carnivores, and desert agamid lizards, both of which are semelparous. Other instances of seasonal stress responses include the Rottnest Island quokka, the Barrow Island euro kangaroo and a small nectarivorous bird, the Silvereye. The review also highlights the high level of physiological adaptation of some desert wallabies, such as the Spectacled hare wallaby, which is able to maintain physiological homeostasis in the field when challenged by conditions of extreme drought. The importance of thermal and hygric refugia for the long-term survival or rock wallabies, which apparently lack any hormonal control of renal function, is also highlighted.

A Flatworm from the Genus Waminoa (Acoela: Convolutidae) Associated with Bleached Corals in Western Australia.

A flatworm isolated from bleached colonies of the coral Coscinaraea marshae at Rottnest Island, Western Australia, is described using a combination of morphological and molecular systematics. This flatworm shares morphological features characteristic of the genus Waminoa (Acoelomorpha: Acoela), including the presence of two algal symbionts, but appears to have genital regions different from those of other described species of Waminoa. The design of new oligonucleotide primers enabled the amplification of partial 18S rDNA of the Rottnest Island acoel specimens, and phylogenetic analysis positioned them within Waminoa, confirming their placement in the genus. Furthermore, Waminoa specimens from Rottnest Island grouped into a sister clade to Waminoa brickneri, indicating that the morphological and genetic differences observed are most likely intraspecific and due to geographic variation. As such, we name these Rottnest Island specimens W. cf. brickneri, but highlight that key differences warrant further exploration before assignment to this species can be confirmed. This is the first acoel flatworm described from Western Australia and contributes to our understanding of the diversity and evolutionary relationship of the Acoela.

Interpretation as a Vital Ingredient of Geotourism in Coastal Environments: The Geology of Sea Level Change, Rottnest Island, Western Australia

At a time of increasing global awareness of the exploitation of the Earth's resources and the environmental impacts of human activity, this article stresses the importance of geological education. It highlights that in a tourism hot spot containing globally significant geological features and processes, it is essential to create educational interpretative themes that provide engaging scientific information to generate appreciation and awareness of climate change. Appropriate literature is reviewed, which includes a brief account of the geology of Rottnest Island. The review emphasizes the interpretive importance of carbonate geological features displaying evidence of sea level change events, exposures of Late Pleistocene aeolionite, and Holocene dune formations. Sea level change is regarded as an especially relevant geological theme for interpretative product development on the island. Such a theme provides the foundation for the interpretation of scientific data that can link the visitor to the significance of environmental change. The article concludes that educative geological themes, as presented via tourism, can provide a dialogue between the public, scientists, and the media about global climate change.

A small no-take marine sanctuary provides consistent protection for small-bodied by-catch species, but not for large-bodied, high-risk species

Despite calls for networks of no-take sanctuary zones of ‘moderate size’ (10–100km2) to meet both conservation and resource management objectives, there have been a plethora of small (1–5km2) and very small (<1km2) no-take areas created in the last decade globally. For example, the temperate eastern Indian Ocean has a range of small to very small no-take marine areas. The current study focused on the Rottnest Island Marine Reserve off the coast of Western Australia, containing the oldest and largest no-take sanctuary zone in the region (1.6km2, established in 1988) and three newly created no-take sanctuary zones (0.8–0.9km2, established in 2007). Three years of transect and baited video monitoring data (2009–2011) from the four no-take areas were compared inside and outside of the sanctuary zones and to previously published studies of the oldest sanctuary zone. Throughout the three-year study, greater size-structure and biomass of two small-bodied by-catch wrasse species were observed in the oldest sanctuary zone, consistent with previously published studies. In contrast to previously published studies from Rottnest, no consistent differences were observed in any large bodied fished species within the oldest sanctuary zone and no increases in biomass were observed in the newly created no-take areas. The results suggest that small sanctuary zones do not provide consistent protection for larger-bodied fished species, but can for smaller-bodied by-catch species. The generality of these results is limited by the lack of replication due to only one established no-take area in the region, and the large proportion of sand habitats which limited the number of sampling sites for reef fishes within the sanctuaries. However, the results suggest that if consistent protection of large-bodied fisheries species is an objective of no-take areas, representative and replicated sanctuary zones should be of greater size and encompass a greater range of depths and habitats. Such systems will also provide the necessary spatial replication between and within no-take areas to design robust monitoring programs to inform conservation management.

The marine soundscape of the Perth Canyon

The Perth Canyon is a submarine canyon off Rottnest Island in Western Australia. It is rich in biodiversity in general, and important as a feeding and resting ground for great whales on migration. Australia’s Integrated Marine Observing System (IMOS) has moorings in the Perth Canyon monitoring its acoustical, physical and biological oceanography. Data from these moorings, as well as weather data from a near-by Bureau of Meteorology weather station on Rottnest Island and ship traffic data from the Australian Maritime Safety Authority were correlated to characterise and quantify the marine soundscape between 5 and 3000Hz, consisting of its geophony, biophony and anthrophony. Overall, biological sources are a strong contributor to the soundscape at the IMOS site, with whales dominating seasonally at low (15–100Hz) and mid frequencies (200–400Hz), and fish or invertebrate choruses dominating at high frequencies (1800–2500Hz) at night time throughout the year. Ships contribute significantly to the 8–100Hz band at all times of the day, all year round, albeit for a few hours at a time only. Wind-dependent noise is significant at 200–3000Hz; winter rains are audible underwater at 2000–3000Hz. We discuss how passive acoustic data can be used as a proxy for ocean weather. Passive acoustics is an efficient way of monitoring animal visitation times and relative densities, and potential anthropogenic influences.

Perennial growth of hermatypic corals at Rottnest Island, Western Australia (32°S).

To assess the viability of high latitude environments as coral refugia, we report measurements of seasonal changes in seawater parameters (temperature, light, and carbonate chemistry) together with calcification rates for two coral species, Acropora yongei and Pocillopora damicornis from the southernmost geographical limit of these species at Salmon Bay, Rottnest Island (32°S) in Western Australia. Changes in buoyant weight were normalised to colony surface areas as determined from both X-ray computed tomography and geometric estimation. Extension rates for A. yongei averaged 51 ± 4 mm y−1 and were comparable to rates reported for Acroporid coral at other tropical and high latitude locations. Mean rates of calcification for both A. yongei and P. damicornis in winter were comparable to both the preceding and following summers despite a mean seasonal temperature range of ∼6 °C (18.2°–24.3 °C) and more than two-fold changes in the intensity of downwelling light. Seasonal calcification rates for A. yongei (1.31–2.02 mg CaCO3 cm−2 d−1) and P. damicornis (0.34–0.90 mg CaCO3 cm−2 d−1) at Salmon Bay, Rottnest Island were comparable to rates from similar taxa in more tropical environments; however, they appeared to decline sharply once summer temperatures exceeded 23 °C. A coral bleaching event observed in December 2013 provided further evidence of how coral at Rottnest Island are still vulnerable to the deleterious effects of episodic warming despite its high latitude location. Thus, while corals at Rottnest Island can sustain robust year-round rates of coral growth, even over cool winter temperatures of 18°–19 °C, there may be limits on the extent that such environments can provide refuge against the longer term impacts of anthropogenic climate change.

Islands of the dead? Prehistoric occupation of Kangaroo Island and other southern offshore islands and watercraft use by Aboriginal Australians

Kangaroo Island has long been a source of creation mythology for Indigenous Australians. Over the last century, it has also been a source of creation mythology for Australian archaeology. The theme of the archaeological mythology has been the notion, based on culture-historical interpretations of stone artefact typologies, that the Island was occupied by people belonging to successive large-tool (“Kartan”) and small-tool “Cultures”. A fundamental tenet of the “Kartan Mystery” has been the notion that the Island was abandoned for several thousand years prior to the European colonisation of South Australia, and following the attainment of modern sea-levels, the Indigenous people of southern Australia lacked either the watercraft or the will to continue to inhabit Kangaroo Island and other offshore islands along the southern coastline. From at least as far east as Tasmania to as far west as Rottnest Island off Fremantle (Western Australia), there are islands which have a prehistoric archaeological record and/or an ethnographic status as uninhabited “Islands of the Dead” for adjacent, mainland or Tasmanian Aboriginal societies. This paper explores these notions and refers to evidence that Aboriginal Australians of the southern Australian coastal regions both used watercraft and visited offshore islands such as Kangaroo Island throughout the pre-colonial Holocene period.

Validation of the wave climate in south-west Australia predicted using the Climate Forecast System Reanalysis

Understanding of measured and predicted waves has an impact on wave energy extraction, efficiency and economics and is therefore a focus for optimisation of Carnegie Wave Energy’s CETO technology. Improvements in weather prediction have enabled the generation of updated wave hindcasts by the National Oceanic and Atmospheric Administration (NOAA) and the Centre for Australian Weather and Climate Research (CAWCR). These were validated for Garden Island, Rottnest Island and Cape Naturaliste in south-west Australia for March to December 2009. The CAWCR data set provides a more extensive list of wave parameters as opposed to three-hourly major wave parameter sets (significant wave height (Hs), peak period (Tp) and peak direction (Dp)) provided by NOAA, and overall performed better. The CAWCR hindcast will form the underpinning data for the Australian Wave Energy Atlas Project, a CSIRO and Bureau of Meteorology project in which Carnegie is a collaborator.

Patterns of marine debris distribution on the beaches of Rottnest Island, Western Australia

Rottnest Island, Western Australia, receives >500,000visitorsy−1, who are mainly attracted by the Island’s natural values. Marine debris is a threat to both these natural values and to Island wildlife, and is consequently an important issue for managers. Engaging with volunteers, we quantified marine debris at 16 beach sites around the Island. The highest loads occurred on the SW coast and primarily comprised items originating from fishing activities. Sites on the NE coast, where >95% of the Island’s accommodation is located, supported the highest abundance of items deposited in situ (e.g. bottles and cigarette butts). We conclude that marine debris management may require a range of strategies to address the different primary sources. Raising awareness through education and intervention may be highly effective at popular beaches on the NE coast, but broader liaison with commercial and recreational fishers will be necessary to address the issue at the Island scale.

Chronology of Quaternary coastal aeolianite deposition and the drowned shorelines of southwestern Western Australia – a reappraisal

Aeolianite successions of low-gradient continental margins commonly show complex records of coastal dune deposition linked to a wide range of sea-level positions and climatic periods of the middle and late Pleistocene, recording both regional and broader-scale drivers of sediment production, coastal dune development and landform preservation. To better characterise the general pattern of sedimentation that occurs over Quaternary glacial–interglacial cycles on low-gradient, temperate carbonate continental shelves we examine the morphology, stratigraphy and age of aeolianite deposits in the Perth region, Western Australia. This includes an analysis of well-defined drowned coastal landforms preserved on the adjacent shelf. New and previously published optical ages provide a preliminary timeframe for the deposition of aeolianite in the Perth region and on Rottnest Island, 17 km offshore. An extensive aeolianite ridge near Perth, representing a former barrier, has Optically Stimulated Luminesence (OSL) ages that range from 120 ± 12 to 103 ± 10 ka (MIS 5e–5a in the context of associated age uncertainties). OSL ages for an exposure in the same ridge 2.5 km inland, record the onlap of much older aeolianite, OSL age 415 ± 70 ka, by shell-rich estuarine beds, OSL age 290 ± 30 ka. A further 5.5 km inland from the coast, two thick aeolianite units, separated by a well-developed palaeosol, have stratigraphically consistent OSL ages of 310 ± 30 and 155 ± 20 ka. In contrast, aeolianite units that form the northern coast of Rottnest Island have OSL ages of 77 ± 12 ka and 27 ± 5 ka. The new OSL ages and previously reported TL and U/Th ages indicate that the bulk of the island comprises dunes deposited around the end of the Last Interglacial sensu lato (MIS 5a–4) and during the Last Glacial (MIS 4–2), accumulating over a Last Interglacial coral reef and basal calcarenite. Drowned barrier and dune landforms preserved on the adjacent continental shelf reveal that barriers were formed during periods of intermediate sea level (e.g. MIS 3) and significant dune mobility occurred when the shelf was subaerially exposed. The pattern of shelf sedimentation discernible in the Perth region – large-scale coastal carbonate dune deposition during periods of high and intermediate sea level and reactivation during glacial lowstands – is largely consistent with published stratigraphic and age data for large-scale aeolianite deposits on other low-gradient carbonate shelves. Based on these data, a general model is proposed for the cycle of Quaternary sedimentation and landform evolution that occurs on these shelves, which are dynamic sedimentary environments with coastal landforms and sedimentary successions that are very sensitive to erosion and sediment reworking.

Coscinaraea marshae corals that have survived prolonged bleaching exhibit signs of increased heterotrophic feeding

Colonies of Coscinaraea marshae corals from Rottnest Island, Western Australia have survived for more than 11 months in various bleached states following a severe heating event in the austral summer of 2011. These colonies are situated in a high-latitude, mesophotic environment, which has made their long-term survival of particular interest as such environments typically suffer from minimal thermal pressures. We have investigated corals that remain unbleached, moderately bleached, or severely bleached to better understand potential survival mechanisms utilised in response to thermal stress. Specifically, Symbiodinium (algal symbiont) density and genotype, chlorophyll-a concentrations, and δ13C and δ15N levels were compared between colonies in the three bleaching categories. Severely bleached colonies housed significantly fewer Symbiodinium cells (p < 0.05) and significantly reduced chlorophyll-a concentrations (p < 0.05), compared with unbleached colonies. Novel Symbiodinium clade associations were observed for this coral in both severely and moderately bleached colonies, with clade C and a mixed clade population detected. In unbleached colonies, only clade B was observed. Levels of δ15N indicate that severely bleached colonies are utilising heterotrophic feeding mechanisms to aid survival whilst bleached. Collectively, these results suggest that these C. marshae colonies can survive with low symbiont and chlorophyll densities, in response to prolonged thermal stress and extended bleaching, and increase heterotrophic feeding levels sufficiently to meet energy demands, thus enabling some colonies to survive and recover over long time frames. This is significant as it suggests that corals in mesophotic and high-latitude environments may possess considerable plasticity and an ability to tolerate and adapt to large environmental fluctuations, thereby improving their chances of survival as climate change impacts coral ecosystems worldwide.

Further characterisation of two Eimeria species (Eimeria quokka and Eimeria setonicis) in quokkas (Setonix brachyurus)

The identification and characterisation of novel Eimeria species has largely been based on sporulated oocyst and sporocyst morphology, the host species and the geographical range. Variation in the size and shape of Eimeria oocysts across their host range however, make the identification and characterisation of novel species using traditional methodologies alone problematic. The use of molecular markers and phylogenetic analysis has greatly advanced our ability to characterise Eimeria species and has recently been applied to understand evolutionary relationships among Eimeria species from Australian marsupials.In the present study, Eimeria species isolated from quokkas (Setonix brachyurus) captured from Two Peoples Bay, Bald Island and Rottnest Island, Western Australia, were morphologically identified as Eimeria quokka and Eimeria setonicis. Both Eimeria species were identified as being polymorphic in nature with regards to sporulated oocyst and sporocyst morphometrics. Phylogenetic analysis using 18S rRNA and COI (cytochrome c oxidase subunit 1) genes, grouped E. quokka and E. setonicis within the Eimeria marsupial clade together with Eimeria trichosuri from brushtail possums, Eimeria macropodis from tammar wallabies (Macropus eugenii) and several unidentified macropod Eimeria species from western grey kangaroos (Macropus fuliginosus). This study is the first to characterise E. quokka and E. setonicis by molecular analysis, enabling more extensive resolution of evolutionary relationships among marsupial-derived Eimeria species.

A case study in the evaluation of geotourism potential through geographic information systems: application in a geology-rich island tourism hotspot

The significant growth in geotourism across all continents over the past two decades has created a strong demand for more creative, robust and systematic approaches to assessing the geotourism potential of natural areas, for identifying suitable sites of geological interest and providing comprehensive frameworks for management. We investigate a range of spatial data-sets using remote sensing analysis tools as well as geographic information systems (GIS) to complement field-derived data and allow for comprehensive analysis of combined data-sets. Such an approach allowed the creation of a spatial geological data base which can be assessed against access and management criteria, including environmental factors and risks. We used the relatively data-rich example of Rottnest Island in the south-west region of Western Australia to demonstrate the opportunities for future geotourism project development.

Spatial analysis of limiting resources on an island: diet and shelter use reveal sites of conservation importance for the Rottnest Island quokka

Context For conservation of any species, we need baseline data that will guide conservation planning strategies. Identifying plant resources used by animal species for food and shelter is the first important step towards fauna conservation. The second step is to determine the extent and distribution of these resources and thus identify prime habitat or habitat that could be improved through suitable management actions. This information provides the necessary spatial targeting required to make the most of few resources and a shortage of time. Aims Applying this model approach, we identified plant species used as food or shelter resources by the conservationally significant quokka (Setonix brachyurus) across Rottnest Island, Western Australia in the aftermath of the hottest and driest summer on record. Methods Dietary analysis was carried out using microhistological examination of plant cuticle remains from faecal samples for 67 locations across the island. Plants acting as diurnal rest shelters (n = 73 sites) were identified through observation of individuals flushed during surveys. Identifying key resources requires both a comprehensive analysis of the current use, as well as knowledge of availability of resources to determine selectivity. We therefore compared food plants or rest sites with a comprehensive survey of floristic diversity and abundance for 210 stratified-randomly located sites across the island. Key results We identified eight plant species that quokkas fed on preferentially and identified four plant species that were the principal shelter sites. We then used hyperspectral remote sensing data to map the distribution of these plant species to quantify their distribution and identify key habitat areas. Conclusions Understanding resource limitation over the most physiologically challenging time of the year provides important information for quokka conservation. Quokkas prefer Malvaceae species as food plants, and use dense, abundant shrubs for shelter. Implications Quokkas appear to have shifted their use of food plants since a previous study (50 years ago), likely reflecting modification of island vegetation due to anthropogenic influences, fire and herbivory over time. In the face of changing climate, this information will serve as an important guide towards conservation management actions on the island (e.g. future planning of revegetation and habitat protection/enhancement).

Visualizing Samsonfish (Seriola hippos) with a Reson 7125 Seabat multibeam sonar

Abstract Parsons, M. J. G., Parnum, I. M., and McCauley, R. D. 2013. Visualizing Samsonfish (Seriola hippos) with a Reson 7125 Seabat multibeam sonar – ICES Journal of Marine Science, 70: 665–674. In Western Australia, aggregations of Samsonfish (Seriola hippos) form each summer to spawn in waters west of Rottnest Island. In this study, a Reson 7125 Seabat multibeam sonar (400 kHz) was pole mounted aboard a 21.6 m vessel, conducting acoustic transects to acquire acoustic backscatter simultaneously from a midwater aggregation of S. hippos and the wreck it surrounded. The processed backscatter produced high-resolution visualizations of both the fish and seabed. During a 15 min period, the centroid of the aggregation moved 91 m around the eastern and northeastern side of the wreck and probably exhibited lateral vessel avoidance behaviour from the survey vessel. Additionally, a northeasterly current at the site was inferred from subtle habitat features, suggesting that at the time of the survey the aggregation preferred to remain upcurrent of the wreck. These findings confirmed that the S. hippos aggregations do not necessarily remain directly above the wrecks and do not always remain sedentary. Aggregation acoustic density packing at the survey site was observed at 12.7 ± 2.4 m3 per fish, equivalent to ∼1.6 ± 0.1 body lengths nearest-neighbour distance.

Perceptions of ecological risk associated with introduced marine species in marine protected areas

The perception of ecological risks (impact and acceptability) associated with introduced marine species (IMS), what demographic variables influence those perceptions, respondent’s knowledge of IMS, and people’s support for controlling introduced marine species impacts on the marine environment was explored at three locations in Western Australia: Ningaloo Reef Marine Park, Rottnest Island Marine Reserve, and Hamelin Bay. Recognition that introduced marine species are an issue at state, national and international levels exists; yet often marine protected area management plans do not reflect this recognition. Therefore, we hypothesise that there is a lack of translation of concern regarding introduced marine species as a risk into tactical objectives within marine protected area management plans. This may be due to low stakeholder perceptions of the risk posed by introduced marine species. Survey respondents had a high level (89%) of self-rated awareness of introduced marine species and they also indicated (93%) a willingness to support management interventions to prevent, or control the spread of introduced marine species in Western Australia. Our results also indicate that gender (males) and age (18–45 age group) influenced respondents’ perception of risk (impact) of IMS, yet no examined demographic variables influenced respondents acceptability of risk. Furthermore, knowledge of introduced marine species, education level, and income variables did not influence respondents’ perception of risk (impact or acceptability). Understanding demographic characteristics that influence participants perceptions related to introduced marine species can be useful for targeted, educational initiatives to reduce the likelihood of IMS incursions. This begins to smooth the way for management to proactively develop and implement policies that are necessary to more fully protect the Western Australian marine environment.

Holocene palaeoenvironmental change from Barker Swamp, Rottnest Island offshore Perth, Western Australia

Holocene palaeoenvironmental change from Barker Swamp, Rottnest Island offshore Perth, Western Australia

Holocene palaeoclimate and sea level fluctuation recorded from the coastal Barker Swamp, Rottnest Island, south-western Western Australia

The Holocene palaeoclimatic history of south-western Western Australia (SWWA) has received little attention compared to south-eastern Australia, and this has resulted in conflicting views over the impact of climate variability in the region. We present here a well-dated, high-resolution record from two overlapping sediment cores obtained from the centre of Barker Swamp, Rottnest Island, offshore Perth. The records span the last 8.7 ka, with the main lacustrine phase occurring after 7.4 ka. This site preserves both pollen and several ostracod taxa. The pollen record suggests a long-term shift from the early-mid Holocene to the late Holocene to drier conditions with less shrubland and more low-ground cover and less fire activity. A salinity transfer function was developed from ostracod faunal assemblage data and trace metal ratios (Mg/Ca, Sr/Ca and Na/Ca) and stable isotopes (δ18O and δ13C) analysed on selected ostracod valves. These provide a detailed history of evaporation/precipitation (E/P) differences that clearly shows that the SWWA region was subjected to significant climatic shifts over the last 7.4 ka, with a broad shift towards increased aridity after 5 ka. The swamp ranged from fresh to saline as recorded in the ostracod valve chemistry and the independently-derived salinity transfer function. The ostracod record also indicates that a sea-level highstand occurred between ca. 4.5 and 4.3 ka, with probable step-wise increases at 6.75, 6.2, and 5.6 ka, with the last vestiges of salt water intrusion at ca. 1 ka. After about 2.3 ka, the fresh, groundwater lens that underlies the western portion of the island intersected the swamp depression, influencing the hydrology of the swamp. The broad climatic changes recorded in Barker Swamp are also compared with data from southern South Africa, and it is suggested that the Southern Annular Mode appears to have been the dominant driver in the climate of these regions and that the Indian Ocean Dipole is of little importance in the southern regions of the south-western Cape of Africa and south-western Western Australia.