Western Coast Of Australia Research Articles

Ocean Transport Pathways to a World Heritage Fringing Coral Reef: Ningaloo Reef, Western Australia.

A Lagrangian particle tracking model driven by a regional ocean circulation model was used to investigate the seasonally varying connectivity patterns within the shelf circulation surrounding the 300 km long Ningaloo Reef in Western Australia (WA) during 2009–2010. Forward-in-time simulations revealed that surface water was transported equatorward and offshore in summer due to the upwelling-favorable winds. In winter, however, water was transported polewards down the WA coast due to the seasonally strong Leeuwin Current. Using backward-in-time simulations, the subsurface transport pathways revealed two main source regions of shelf water reaching Ningaloo Reef: (1) a year-round source to the northeast in the upper 100 m of water column; and (2) during the summer, an additional source offshore and to the west of Ningaloo in depths between ~30 and ~150 m. Transient wind-driven coastal upwelling, onshore geostrophic transport and stirring by offshore eddies were identified as the important mechanisms influencing the source water origins. The identification of these highly time-dependent transport pathways and source water locations is an essential step towards quantifying how key material (e.g., nutrients, larvae, contaminants, etc.) is exchanged between Ningaloo Reef and the surrounding shelf ocean, and how this is mechanistically coupled to the complex ocean dynamics in this region.

Potato spindle tuber viroid: alternative host reservoirs and strain found in a remote subtropical irrigation area

During 2007–2012, Potato spindle tuber viroid (PSTVd) was detected in volunteer cultivated, wild and native plants during studies to determine whether Pospiviroids occur within the isolated, sub-tropical, Gascoyne Horticultural District (GHD) in central coastal Western Australia (WA). PSTVd was detected infecting volunteer crop plants of tomato, pepper and chilli; introduced weed species Solanum nigrum (blackberry nightshade), Datura leichhardtii (thornapple) and Nicandra physalodes (apple-of-Peru) (Solanaceae), and Conyza bonariensis (flaxleaf fleabane) (Asteraceae); and Australian native species Atriplex semilunaris (annual saltbush), Rhagodia eremaea (thorny saltbush) (Chenopodiaceae), and Streptoglossa sp. (Asteraceae). PSTVd was also detected infecting Physalis angulata (wild gooseberry) in the Ord River Irrigation Area (ORIA), Kimberley region in north-west WA. Comparison of sequences from the three complete and 18 partial RNA nucleotide sequences obtained from 20 GHD and one ORIA isolates with those of published sequences showed that their highest nucleotide sequence identities were to isolate AY962324 belonging to the Chittering strain from south-west WA. On phylogenetic analysis, the three completely sequenced GHD PSTVd isolates grouped within a cluster of isolates from tomato and P. peruviana. These results show that a naturally occurring PSTVd inoculum reservoir is present in the GHD. This reservoir explains the occurrence of repeated PSTVd infections in different years in field crops of tomato, pepper and chilli growing in its market gardens and small farms. These findings have implications concerning PSTVd spread in intensive solanaceous crop field production systems in other subtropical regions of the world.

Long-term carbon storage and its recent loss in an estuarine Posidonia australis meadow (Albany, Western Australia)

Oyster Harbour, on the south coast of Western Australia, supports 3.6–3.9 km2 of seagrass meadows, following the loss of approximately 2.8–3.1 km2 in the 1980s. This small area of prevailing meadows hold significant carbon stores accumulated over the past 3000 years. In this study, we sampled three sediment cores from a Posidonia australis meadow and analysed organic matter (OM), organic carbon (OC) and inorganic carbon (IC) contents in bulk sediments, and δ13C signatures of OM. The OM and OC contents (mean ± SE) in the cores were 9.07 ± 0.36% and 2.24 ± 0.05%, respectively. The mean IC content was 3.16 ± 0.17%. δ13C signatures of the sedimentary OM ranged from −10.01‰ to −13.28‰. Using a Bayesian isotopic mixing model, it is estimated that 57–67% of the OM in the seagrass sediments was derived from P. australis detrital matter. The total carbon (TC) stores in 150 cm-thick seagrass sediments averaged 27.92 kg TC m−2 (10.79 kg OC m−2 and 17.13 kg IC m−2). Based on radiocarbon dating, the mean sediment accumulation rate was 0.0494 cm yr−1, which led to a long-term TC accumulation rate of 8.92 g TC m−2 yr−1 (3.45 g OC m−2 yr−1 and 5.47 g IC m−2 yr−1). Based on historical seagrass cover (3.6–6.7 km2 during the 1960s to 1980s), the estimated TC stores in 150 cm-thick seagrass sediments at Oyster Harbour would have been 101–187 Gg TC. The eutrophication-driven loss of seagrasses during the 1980s resulted in the absence of OC accumulation capacity amounting to 280–310 Mg OC (over 29 years). The loss of seagrass area could also have resulted in the release of 37–41 Gg CO2, assuming that all of the OC in shallow sediment is remineralised after meadow disturbance. These results exemplify the importance of seagrasses meadows as important carbon sinks and the potential for losses of carbon stores due to ecosystem degradation.

Putting the ‘Indo’ back into the Indo-Pacific: resolving marine phylogeographic gaps

The Indo-Pacific is an extremely large marine realm that unites two oceans via a restricted Coral Triangle corridor, which was historically subjected to lowered sea levels during global glaciation. Although a strong phylogeographic focus on the Central and West Pacific has produced a large body of research, the Indian Ocean has been largely neglected. This may have serious consequences, because the Indian Ocean hosts a large number of marine centres of endemism, yet a large number of nations rely on its marine resources. We examine reasons for this neglect and review what is known about this region and its connectivity to the Indo-West Pacific. We draw attention to the ‘Leeuwin Effect’, a phenomenon where the southward flow of the Leeuwin Current is responsible for transporting larval propagules from the Coral Triangle region down the coast of Western Australia, resulting in broader Indo-West Pacific rather than Indian Ocean affinities. Given challenges in accessing infrastructure and samples, collaboration will inevitably be key to resolving data gaps. We challenge the assumption that the peak of shallow-water marine biodiversity is solely centred in the Coral Triangle, and raise awareness of a seemingly forgotten hypothesis promoting a secondary peak of biodiversity in the western Indian Ocean.

Dutch East India Company shipbuilding: the archaeological study of Batavia and other seventeenth-century VOC ships

Eight months into its maiden voyage to the Indies, the Dutch East India Company's Batavia sank on June 4, 1629 on Morning Reef in the Houtman Abrolhos off the western coast of Australia. Wendy van Duivenvoorde's five-year study was aimed at reconstructing the hull of Batavia , the only excavated remains of an early seventeenth-century Indiaman to have been raised and conserved in a way that permits detailed examination, using data retrieved from the archaeological remains, interpreted in the light of company archives, ship journals, and Dutch texts on shipbuilding of this period. Over two hundred tables, charts, drawings, and photographs are included.

New range and habitat records for threatened Australian sea snakes raise challenges for conservation

Hydrophiine (true) sea snakes are large predatory live-bearing marine reptiles. Australia is a biodiversity hotspot for true sea snakes with almost half of the ~70 extant species (including 11 endemics). Two Australian endemics, Aipysurus foliosquama and Aipysurus apraefrontalis, were listed as Critically Endangered (CR) under IUCN Red List (2010) criteria and Australia's Threatened Species Legislation (2011) due to their restricted geographic ranges being <10km2 (i.e. Ashmore and Hibernia Reefs, Timor Sea), from where they disappeared between 1998 and 2002. However, museum and anecdotal records suggested that these species might also occur in coastal locations of Western Australia (WA). We used intensive field surveys, habitat data, and molecular genetics to document the first unequivocal records of living A. foliosquama (n=16) and A. apraefrontalis (n=7) since they were listed as Critically Endangered, in coastal WA. Our data significantly increases the known geographic range and habitats of A. foliosquama, to include seagrass meadows in subtropical Shark Bay (latitudes 24.5°S to 26.6°S), which is 500km further south than any previous sighting. Most sea snakes were collected from demersal prawn trawl by-catch surveys, indicating that these species are vulnerable to demersal trawl gear. Nonetheless, the disappearance of these two species from Ashmore Reef (which coincided with extirpations of at least three other sea snake species) could not be attributed to trawling and remain unexplained. Key threatening processes will need to be identified if effective conservation strategies are to be implemented to protect these newly discovered coastal populations of two Critically Endangered species.

The Population Origins and Expansion of Feral Cats in Australia

The historical literature suggests that in Australia, the domestic cat (Felis catus) had a European origin [~200 years before present (ybp)], but it is unclear if cats arrived from across the Asian land bridge contemporaneously with the dingo (4000 ybp), or perhaps immigrated ~40000 ybp in association with Aboriginal settlement from Asia. The origin of cats in Australia is important because the continent has a complex and ancient faunal assemblage that is dominated by endemic rodents and marsupials and lacks the large placental carnivores found on other large continents. Cats are now ubiquitous across the entire Australian continent and have been implicit in the range contraction or extinction of its small to medium sized (<3.5kg) mammals. We analyzed the population structure of 830 cats using 15 short tandem repeat (STR) genomic markers. Their origin appears to come exclusively from European founders. Feral cats in continental Australia exhibit high genetic diversity in comparison with the low diversity found in populations of feral cats living on islands. The genetic structure is consistent with a rapid westerly expansion from eastern Australia and a limited expansion in coastal Western Australia. Australian cats show modest if any population structure and a close genetic alignment with European feral cats as compared to cats from Asia, the Christmas and Cocos (Keeling) Islands (Indian Ocean), and European wildcats (F. silvestris silvestris).

Prioritising weed management activities in a data deficient environment: the Pilbara islands, Western Australia

Along the Pilbara coast of Western Australia (WA) there are approximately 598 islands with a total area of around 500 km2. Budget limitations and logistical complexities mean the management of these islands tends to be opportunistic. Until now there has been no review of the establishment and impacts of weeds on Pilbara islands or any attempt to prioritise island weed management. In many instances only weed occurrence has been documented, creating a data deficient environment for management decision making. The purpose of this research was to develop a database of weed occurrences on WA islands and to create a prioritisation process that will generate a ranked list of island-weed combinations using currently available data. Here, we describe a model using the pairwise comparison formulae in the Analytical Hierarchy Process (AHP), four metrics describing the logistical difficulty of working on each island (island size, ruggedness, travel time, and tenure), and two well established measures of conservation value of an island (maximum representation and effective maximum rarity of eight features). We present the sensitivity of the island-weed rankings to changes in weights applied to each decision criteria using Kendall's tau statistics. We also present the top 20 ranked island-weed combinations for four modelling scenarios. Many conservation prioritisation tools exist. However, many of these tools require extrapolation to fill data gaps and require specific management objectives and dedicated budgets. To our knowledge, this study is one of a few attempts to prioritise conservation actions using data that are currently available in an environment where management may be opportunistic and spasmodic due to budgetary restrictions.

A mid-Holocene candidate tsunami deposit from the NW Cape (Western Australia)

Although extreme-wave events are frequent along the northwestern coast of Western Australia and tsunamis in 1994 and 2006 induced considerable coastal flooding locally, robust stratigraphical evidence of prehistoric tropical cyclones and tsunamis from this area is lacking. Based on the analyses of X-ray computed microtomography (μCT) of oriented sediment cores, multi-proxy sediment and microfaunal analyses, optically stimulated luminescence (OSL) and 14C-AMS dating, this study presents detailed investigations on an allochthonous sand layer of marine origin found in a back-barrier depression on the NW Cape Range peninsula. The event layer consists of material from the adjacent beach and dune, fines and thins inland, and was traced up to ~400m onshore. Although a cyclone-induced origin cannot entirely be ruled out, the particular architecture and fabric of the sediment, rip-up clasts and three subunits point to deposition by a tsunami. As such, it represents the first stratigraphical evidence of a prehistoric, mid-Holocene tsunami in NW Western Australia. It was OSL-dated to 5400–4300years ago, thus postdating the regional mid-Holocene sea-level highstand.

Complete mitochondrial genome of Australian spiny lobster, Panulirus cygnus (George, 1962) (Crustacea: Decapoda: Palinuridae) from coast of Australia

We characterized the total mitochondrial genome of Australian spiny lobster, Panulirus cygnus (George, 1962), which is found along the western coast of Australia. Total mitochondrial genome length of P. cygnus was 15 724 bp, in which 13 proteins, 2 ribosomal RNAs, 22 transfer RNAs, and a putative control region were encoded. Nine and four protein-coding genes are encoded on the H-strand and on the L-strand, respectively. According to the phylogenetic analysis, P. cygnus was most closely related to Panulirus japonicus among the compared six species belonging to Palinuridae. Although overall gene organization was the same, the putative control region (between SrRNA gene and tRNAIlel) is least similar to one another among mitochondrial genomes from the compared six species belonging to Palinuridae

The South African estuarine specialist Codium tenue (Bryopsidales, Chlorophyta) discovered in a south-western Australian estuary

Abstract Codium tenue, previously known reliably only from estuarine habitats in South Africa, is recorded from a similar habitat in the Walpole and Nornalup Inlet system, on the south coast of Western Australia. The Australian C. tenue has a repeatedly divaricately dichotomously branched thallus to 11.5 cm in height, with markedly compressed axes up to 1 cm in width at branch dichotomies, but distally attenuating to terete branch apices. Structurally, thalli have cortices with distinctive cuneate utricles up to 1310 μm long and 650 μm in diameter. Both the habit and structural morphology essentially agree with C. tenue as known in South Africa. Sequences generated from the Australian specimens are also wholly comparable with those of South African specimens newly generated in this study. While similarly disjunct South African/Western Australian distributions are known for other algae, that of C. tenue is particularly remarkable in that the species is apparently an estuarine specialist.

Extraordinary capture of a Randall's snapper Randallichthys filamentosus in the temperate south-eastern Indian Ocean and its molecular phylogenetic relationship within the Etelinae.

The capture of a rarely encountered Randall's snapper Randallichthys filamentosus (female, 587 mm fork length) from the upper continental slope (c. 350 m) off the south coast of Western Australia (c. 34·5° S; 122·5° E) in January 2014 represents its first record from the temperate Indian Ocean and a southern range extension. This record suggests that spawning of this predominantly tropical species may probably be occurring in the eastern Indian Ocean, considering the extensive, and unlikely, distance the progeny would have otherwise travelled from its typical distribution in the western and central Pacific Ocean.

Freshening anomalies in the Indonesian throughflow and impacts on the Leeuwin Current during 2010-2011

During the 2010–2011 La Nina and Ningaloo Nino, excessive precipitations in the Maritime Continent and Indonesian-Australian Basin caused surface waters to freshen by 0.3 practical salinity unit in the southeast Indian Ocean. The low-salinity anomalies are observed to be carried westward by the Indonesian throughflow and the South Equatorial Current and transmitted into the poleward flowing eastern boundary current, the Leeuwin Current, along the Western Australian coast. Low-salinity anomalies contribute to about 30% of the anomalous increase of the southward Leeuwin Current transport during the evolution of the 2010–2011 Ningaloo Nino, resulting in unprecedented warming off the coast of Western Australia. Episodical freshening of the Leeuwin Current has been observed at the Rottnest coastal reference station of Western Australia during extended La Nina conditions over the past several decades; low-salinity anomalies at the station during the 2010–2011 Ningaloo Nino are comparable with strong historical events.

Biochar and Compost Increase Crop Yields but the Effect is Short Term on Sandplain Soils of Western Australia

Sandplain soils on the south coast of Western Australia have low inherent fertility, which is mainly due to poor nutrient retention caused by insufficient clay and organic colloidal material. Previous research has shown the benefits in nutrient levels and retention from adding clay to sandplain soils; however, there is almost no information on the addition of organic amendments. A field experiment was established at the Esperance Downs Research Station, Western Australian, in May 2010, to assess the effects of wheat straw (WS) and chicken manure (CM) biochars and compost with and without phosphorus (P) addition on soil properties and crop production over five growing seasons. The five seasons alternated between winter and summer crops. The CM and WS biochar and compost treatments significantly increased crop yields and P uptake in 3, 2 and 1 of the five seasons, respectively. The yield increases (P « 0.05) were no more than 8%. By the end of the third season, no differences in crop yields were found that could be attributed to the organic amendments. The addition of P increased crop yields in each winter cropping season. Phosphorus addition explained more than 30% of the variation in crop yields. Despite marginal P levels and summer drought conditions, arbuscular mycorrhizal root colonisation was not affected by the organic amendments. There were no significant interactions between the organic amendments and P addition in terms of crop yields, P uptake or P uptake efficiency. We conclude that much of the effect of the organic amendments was due to direct nutrient addition which dissipated over time.

Isolation by resistance across a complex coral reef seascape.

A detailed understanding of the genetic structure of populations and an accurate interpretation of processes driving contemporary patterns of gene flow are fundamental to successful spatial conservation management. The field of seascape genetics seeks to incorporate environmental variables and processes into analyses of population genetic data to improve our understanding of forces driving genetic divergence in the marine environment. Information about barriers to gene flow (such as ocean currents) is used to define a resistance surface to predict the spatial genetic structure of populations and explain deviations from the widely applied isolation-by-distance model. The majority of seascape approaches to date have been applied to linear coastal systems or at large spatial scales (more than 250 km), with very few applied to complex systems at regional spatial scales (less than 100 km). Here, we apply a seascape genetics approach to a peripheral population of the broadcast-spawning coral Acropora spicifera across the Houtman Abrolhos Islands, a high-latitude complex coral reef system off the central coast of Western Australia. We coupled population genetic data from a panel of microsatellite DNA markers with a biophysical dispersal model to test whether oceanographic processes could explain patterns of genetic divergence. We identified significant variation in allele frequencies over distances of less than 10 km, with significant differentiation occurring between adjacent sites but not between the most geographically distant ones. Recruitment probabilities between sites based on simulated larval dispersal were projected into a measure of resistance to connectivity that was significantly correlated with patterns of genetic divergence, demonstrating that patterns of spatial genetic structure are a function of restrictions to gene flow imposed by oceanographic currents. This study advances our understanding of the role of larval dispersal on the fine-scale genetic structure of coral populations across a complex island system and applies a methodological framework that can be tailored to suit a variety of marine organisms with a range of life-history characteristics.

Danger in the reef: Proteome, toxicity, and neutralization of the venom of the olive sea snake, Aipysurus laevis

Four specimens of the olive sea snake, Aipysurus laevis, were collected off the coast of Western Australia, and the venom proteome was characterized and quantitatively estimated by RP-HPLC, SDS-PAGE, and MALDI-TOF-TOF analyses. A. laevis venom is remarkably simple and consists of phospholipases A2 (71.2%), three-finger toxins (3FTx; 25.3%), cysteine-rich secretory proteins (CRISP; 2.5%), and traces of a complement control module protein (CCM; 0.2%). Using a Toxicity Score, the most lethal components were determined to be short neurotoxins. Whole venom had an intravenous LD50 of 0.07 mg/kg in mice and showed a high phospholipase A2 activity, but no proteinase activity in vitro. Preclinical assessment of neutralization and ELISA immunoprofiling showed that BioCSL Sea Snake Antivenom was effective in cross-neutralizing A. laevis venom with an ED50 of 821 μg venom per mL antivenom, with a binding preference towards short neurotoxins, due to the high degree of conservation between short neurotoxins from A. laevis and Enhydrina schistosa venom. Our results point towards the possibility of developing recombinant antibodies or synthetic inhibitors against A. laevis venom due to its simplicity.

Crustose coralline algal growth, calcification and mortality following a marine heatwave in Western Australia

Crustose coralline algae (CCA: Corallinaceae, Rhodophyta) are ubiquitous components of many benthic habitats and play a critical ecological role by contributing significantly to their structural complexity and diversity. During the austral summer of 2010–2011 a “marine heatwave” severely impacted marine communities along the coast of Western Australia (WA). The heatwave was characterised by anomalously high seawater temperatures throughout that summer and, to a lesser extent, for the two summers thereafter. To investigate coralline algal response to heating we measured growth, calcification and mortality rates for Hydrolithoideae CCA at Marmion Lagoon off of Perth, WA, from winter 2011 to winter 2013, directly following the 2010–2011 heatwave. Seawater carbonate chemistry and temperature were also measured to facilitate a more complete understanding of the various drivers of coralline algal metabolism. Extension and calcification rates were generally within the expected ranges, however, normal seasonal patterns were not observed. Instead, there was a distinct lack of seasonality in growth rates and high rates of mortality during summer suggesting that these coralline algae were experiencing stress, which was likely related to anomalously high seawater temperatures. Our results indicate that Western Australian CCA are susceptible to prolonged heating events, and the extent of their vulnerability may be dependant on species-specific tolerance levels as well as additional ecological and environmental factors.

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.

Identifying locations for large-scale microalgae cultivation in Western Australia: A GIS approach

Abstract The decline in available fossil fuel resources coupled with an ever increasing global demand for energy, have led to substantial interest in the development of renewable biofuels. Biofuels from microalgae, especially liquid fuels produced from saline microalgae lipids (oils), are seen as an important component of the future biofuels mix. In Australia, several companies and research groups are working on developing microalgal biofuels and whilst most are still in the research and development stage, recently constructed demonstration facilities highlight the potential for large-scale cultivation. Western Australia (WA) specifically, has several key advantages for large-scale microalgae for biofuel cultivation including abundant sunshine, extensive land area unsuitable for agriculture, an abundant water source in the Indian Ocean, existing infrastructure in several potential locations, high local demand for fuel and stable political conditions. The purpose of this study was to identify capable geographic locations for constructing large-scale microalgae for biofuel cultivation facilities in WA. Through the development of the Australian Algal Cultivation–Spatial Location Model (AAC–SLM) an examination of site specific parameters such as irradiance, temperature, CO2 and nutrient availability, workability of soils, land-use and access to distribution infrastructure and a viable workforce, most capable locations for large-scale microalgae cultivation were identified in the state. Results indicate that large tracts of land along the central coast of Western Australia are ideal for cultivation development and could produce up to 11% of Australia’s annual automotive diesel needs across the most suitable locations. The end result provides a robust method that can be tailored to the specific requirements and data availability of other regions within Australia and in other nations as a tool to attract future development through the identification of capable cultivation locations.

Traces of historical tropical cyclones and tsunamis in the Ashburton Delta (north‐west Australia)

AbstractAlthough the north‐western coast of Western Australia is highly vulnerable to tropical cyclones and tsunamis, little is known about the geological imprint of historic and prehistoric extreme wave events in this particular area. Despite a number of site‐specific difficulties such as post‐depositional changes and the preservation potential of event deposits, both tropical cyclones and tsunamis may be inferred from the geomorphology and the stratigraphy of beach ridge sequences, washover fans and coastal lagoons or marshes. A further challenge is the differentiation between tsunami and storm deposits in the geological record, particularly where modern deposits and/or historical reports on the event are not available. This study presents a high‐resolution sedimentary record of washover events from the Ashburton River delta (Western Australia) spanning approximately the last 150 years. A detailed characterization of event deposits is provided, and a robust chronostratigraphy for the investigated washover sequence is established based on multi‐proxy sediment analyses and optically stimulated luminescence dating. Combining sedimentological, geochemical and high‐resolution optically stimulated luminescence data, event layers are assigned to known historical events and tropical cyclone deposits are separated from tsunami deposits. For the first time, the 1883 Krakatoa and 1977 Sumba tsunamis are inferred from sedimentary records of the north‐western part of Western Australia. It is demonstrated that optically stimulated luminescence applied in coastal sedimentary archives with favourable luminescence characteristics can provide accurate chronostratigraphies even on a decadal timescale. The results contribute to the data pool of tropical cyclone and tsunami deposits in Holocene stratigraphies; however, they also demonstrate how short‐lived sediment archives may be in dynamic sedimentary environments.