Australian Waters Research Articles

Genomic population structure of great hammerhead sharks (Sphyrna mokarran) across the Indo-Pacific

Context Currently, little information exists describing the population structure of great hammerhead sharks (Sphyrna mokarran) in Australian waters. Aims This study used single nucleotide polymorphisms to investigate fine-scale population structure in S. mokarran across the Indo-Pacific. Methods DNA was extracted from 235 individuals across six Australian locations and a Red Sea outgroup. Population parameters were calculated and visualised to test structuring across locations. Key results No fine-scale population structuring was observed for S. mokarran across the Indo-Pacific. However, population structuring occurred for all Australian locations when compared to the Red Sea outgroup. Conclusions Findings suggest a single stock is most likely for S. mokarran found in Australian waters. Results provide key information for understanding the broad range movements of S. mokarran and help to define the scale of management required to preserve genetic diversity in this species. The structuring between Australia and the Red Sea indicates limited gene flow and movement. Implications Results indicate that large-scale movements of S. mokarran could be occurring to facilitate genetic mixing. Future research focusing on individual tagging to corroborate movements would be highly beneficial to determine how far (and often) individuals are dispersing, and to note where cross-jurisdictional management, including from neighbouring regions in the Indo-West Pacific–Oceania region, are most critical.

Casting a wider net: A national survey of Australian attitudes to marine protected areas

Marine protected areas (MPAs) are a key international conservation strategy to regulate human pressures on marine environments and are central to marine management in Australia. Public support is considered crucial to the success of MPAs in achieving the long-term conservation of nature, yet how the broader Australian public understands and values MPAs is not well understood. Previous research has explored attitudes of direct and proximate stakeholder groups or focused on specific regions. Human connections to marine environments, however, are not limited to direct use nor confined to single geographies. We surveyed a nationally representative sample of Australian adults (n = 1049) to explore how the broader public understand, connect to, and value Australia’s marine environments and MPAs. To the best of our knowledge, this is the first study to investigate general attitudes to Australia’s total MPA system and interconnected marine environments with a nationally representative sample to provide an aggregated overview of Australian public attitudes. Most Australians (53%) acknowledge that they have a knowledge gap regarding the restrictions, requirements, and protections of MPAs as they apply in the Australian context, while 37% incorrectly believe that all MPAs offer uniform protections that, for example, prohibit the extraction of natural resources. Australians want to see an expansion of MPA coverage to represent 73% of Australian waters. Australians value the intrinsic biospheric characteristics of marine environments and want to see marine life as the focus when designing MPAs, above instrumental dimensions including industry and recreation. This study provides important insights for policymakers and managers in meeting broader public expectations in the expansion of Australia’s marine protections.

Exploring multi-decadal time series of temperature extremes in Australian coastal waters

Abstract. The intensity and frequency of extreme ocean temperature events, such as marine heatwaves (MHWs) and marine cold spells (MCSs), are expected to change as our oceans warm. Little is known about marine extremes in Australian coastal waters, particularly below the surface. Here we introduce a multi-decadal observational record of extreme ocean temperature events starting in the 1940s and 1950s between the surface and the bottom (50–100 m) at four long-term coastal sites around Australia: the Australian Multi-Decadal Ocean Time Series EXTreme (AMDOT-EXT) data products (https://doi.org/10.26198/wbc7-8h24, Hemming et al., 2024). The data products include indices indicating the timing of extreme warm and cold temperature events, their intensity and the corresponding temperature time series and climatology thresholds. We include MHWs, MCSs and shorter-duration heat spikes and cold spikes. For MHWs and MCSs, which are defined as anomalies above the daily varying 90th and 10th percentiles, respectively, and lasting more than 5 d, we also provide further event information, such as their category and onset and decline rates. The four data products are provided as CF-compliant NetCDF files, and it is our intention that they be updated periodically. It is advised that data users seek the latest data product version. Using these multi-decadal data products, we show the most intense and longest extreme temperature events at these sites, which have occurred below the surface. These data records highlight the value of long-term full water column ocean data for the identification of extreme temperature events below the surface.

First Record of a Piebald Bottlenose Dolphin (Tursiops truncatus) in Australian Waters

First Record of a Piebald Bottlenose Dolphin (Tursiops truncatus) in Australian Waters

Geomorphometric maps of Australia’s Marine Park estate and their role in improving the integrated monitoring and management of marine ecosystems

The loss of marine biodiversity is a major global issue that needs to be prioritised. In Australia, a considerable proportion (48%) of its Exclusive Economic Zone is dedicated to marine protected areas. To effectively manage this network of marine protected areas Australia has recently introduced a Management Effectiveness system. This system is designed to identify, monitor, and manage natural values and the various activities and pressures affecting the Australian Marine Parks (AMPs). Key to this approach is the identification and accurate mapping of the location of these values and pressures acting on the seabed. The AusSeabed program is a national initiative in Australia aimed at improving access to bathymetric data and coordinating efforts to collect such data in Australian waters. This manuscript proposes a novel systematic processing method to create detailed and scalable geomorphometric maps from AusSeabed’s bathymetric data holdings, intended as a standard operating procedure for initial bathymetric data interpretation in the AMPs. Utilising this workflow, we produce seafloor geomorphometry maps across 37 AMPs within which sufficient bathymetric data has been collected. These maps can be used 1) for predictive mapping of biological assemblages; 2) in field sampling design for the collection of ‘ground truthing’ data (e.g. underwater imagery and sediment samples) to validate habitat maps from bathymetric datasets; and 3) as input datasets for subsequent geomorphological mapping with a deeper understanding of seafloor processes. This research highlights the importance of robust geomorphometry classification standards to ensure consistency in mapping Australia’s marine estate in preparation for the Decade of Oceans plans. The Seamap Australia program provides a stepwise approach to advancing Australia’s national collection of bathymetric data into derived products that can enable habitat mapping of Australian waters, providing a foundational tool for the adaptive management of AMPs.

Flapping about: trends and drivers of Australian cownose ray (Rhinoptera neglecta) coastal sightings at their southernmost distribution range

The Australian cownose ray (Rhinoptera neglecta) is an understudied batoid that occurs along Australia's north and east coasts. Currently classified as Data Deficient on the IUCN Red List of Threatened Species, major knowledge gaps exist regarding the species' geographic range, habitat use and the drivers influencing its presence in coastal Australian waters. Sightings of R. neglecta were collected during systematic aerial surveys conducted along 980 km (~47%) of the New South Wales (NSW) coastline between 2017 and 2019. North-bound surveys were flown 500 m offshore, whilst return surveys were flown along the beach/sea interface (inshore or nearshore). Using generalized additive models and a set of nine predictors, we examined the relationship between the spatio-temporal occurrence of R. neglecta, their group size and the biophysical environment at the southernmost extent of their distribution. Results for the presence/absence (44.20% deviance explained) and group size of R. neglecta observed offshore and inshore (42.58 and 41.94% deviance explained, respectively) highlighted latitude, day of year, sea surface temperature, rainfall, wind speed, and wind direction as common influences to the three models. The models indicated R. neglecta were more likely to be present in the northern half of NSW during spring and summer months. However, larger group sizes were more likely to be observed in more southern regions during the same seasons, regardless of whether they were observed offshore or inshore. Group size is also likely influenced by more localized conditions, such as SST and tidal flows. This study represents the largest attempt to date to decipher the spatial ecology of R. neglecta and provides insights into the spatio-temporal distribution and relative abundance of the species along the full extent of the NSW coastline, extending the species' known distribution by over 70 km southward.

Distribution and morphology of the diatom genus Olifantiella Riaux-Gobin & Compère in Indonesian and Australian waters, including the description of O.gondwanensis sp. nov.

Samples from coastal tropical waters of Central Sulawesi, Bangka Island and Bawean Island in Indonesia and from the Great Barrier Reef at Fitzroy Island in Queensland, Australia were analysed for species composition of diatom assemblages with a focus on Olifantiella. Whereas samples from Fitzroy Island littoral in Australia retrieved only one species of Olifantiella, in Poso Bay, Indonesia, we observed at least six species. All established taxa were documented with light (LM) and scanning electron microscope (SEM) and principal component analysis (PCA) analysis was used to compare the species, based on the basic valve parameters of length, width, length to width ratio and striae density. A new species of the genus Olifantiella, O.gondwanensis is described from Australia. In addition, we showed the distinct nature of O.pilosellavar.rhizophorae permitting to species status. Particular attention is placed on girdle bands in this genus.

Microplastics and other anthropogenic fibres in large apex shark species: Abundance, characteristics, and recommendations for future research

Microplastics and microfibres are found ubiquitously in global oceans as well as marine organisms from different trophic levels. However, little is known about the presence of microplastics and microfibres in marine megafauna, such as sharks. This study provided the first investigation of the presence of microplastics and other anthropogenic fibres (i.e., cellulose based fibres) in intestine and muscle samples of four large apex shark species in Australian coastal waters. Microplastics and other anthropogenic fibres were found in 82% of the analysed intestine samples. The mean abundance in intestine samples was 3.1 ± 2.6 particles/individual, which corresponded to 0.03 ± 0.02 particles/g of intestine, across all shark species. The size of particles ranged from 190 to 4860 μm in length with 92% being fibrous in shape and the rest fragments. FTIR spectroscopy identified that 70% of fibres were cellulose-based followed by polyethylene terephthalate (PET), while the fragments were polyethylene and polypropylene. In shark muscles, 60% of samples contained microplastics and other anthropogenic fibres, again with the majority being cellulose-based fibres followed by PET fibres. Methodological differences hinder a more comprehensive assessment of microplastic contamination across studies. Additionally, we identified some challenges which should be factored in for future studies looking at the presence of microplastics as well as other anthropogenic fibres in these large marine organisms. Overall, the findings provide first evidence of microplastics and other anthropogenic fibres not only in the intestines, but also in muscle tissues of large apex shark species.

Modelling perspective on the climate footprint in south east Australian marine waters and its fisheries

Abstract South eastern Australia is a global warming hotspot, and is also home to ~70% of Australia’s population and one of Australia’s largest fisheries—the South East Scalefish and Shark Fishery. This fishery spans shelf to deep waters, subtropical to temperate waters, employs many gears, and interacts with over 100 species. Despite following best practice fisheries management principles, including taking an ecosystem perspective to overall fisheries interactions, management interventions have failed to arrest or recover the decline of some focal species. Using an Atlantis ecosystem model developed for the fishery over the past 20 years, this paper presents simulations that suggest climate change may be a major contributor to the trajectories seen for a number of species—such as jackass morwong (Nemadactylus macropterus), blue warehou (Seriolella brama), and gemfish (Rexea solandri). This kind of climate influence poses many challenges for fisheries management into the future, raising questions about what to do when climate change undermines or overrides fisheries management actions and objectives.

Development and Validation of Multiple Linear Regression Models for Predicting Chronic Zinc Toxicity to Freshwater Microalgae.

Multiple linear regression (MLR) models were developed for predicting chronic zinc toxicity to a freshwater microalga, Chlorella sp., using three toxicity-modifying factors (TMFs): pH, hardness, and dissolved organic carbon (DOC). The interactive effects between pH and hardness and between pH and DOC were also included. Models were developed at three different effect concentration (EC) levels: EC10, EC20, and EC50. Models were independently validated using six different zinc-spiked Australian natural waters with a range of water chemistries. Stepwise regression found hardness to be an influential TMF in model scenarios and was retained in all final models, while pH, DOC, and interactive terms had variable influence and were only retained in some models. Autovalidation and residual analysis of all models indicated that models generally predicted toxicity and that there was little bias based on individual TMFs. The MLR models, at all effect levels, performed poorly when predicting toxicity in the zinc-spiked natural waters during independent validation, with models consistently overpredicting toxicity. This overprediction may be from another unaccounted for TMF that may be present across all natural waters. Alternatively, this consistent overprediction questions the underlying assumption that models developed from synthetic laboratory test waters can be directly applied to natural water samples. Further research into the suitability of applying synthetic laboratory water-based models to a greater range of natural waters is needed. Environ Toxicol Chem 2023;42:2630-2641. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Humpback whale: Yes/no? Challenges with passive acoustic monitoring of this well-described species

Humpback whales sing song and produce non-song sounds. Dozens of research articles have described their acoustic repertoire—even if only considering Australian waters. While song structure changes slowly over seasons, individual notes may exhibit multi-decadal stability. Irrespectively, automatically detecting humpback whale vocalizations remains an ongoing development activity while manual validation of automated detections continues to be problematic. While analysing archival recordings from Australian waters using the NOAA/Google convolutional neural network pretrained for humpback whale song [https://tfhub.dev/google/humpbackwhale/1], we found numerous instances of a particular type of sound with spectrographic features resembling those of humpback whale vocalizations. These sounds lacked the context of a song and occurred in chorus-like patterns, withthe same sound recorded at varying received levels and overlapping in time—indicative of many animals simultaneously producing nothing but this specific call. To investigate these phenomena further, we (1) built a custom detector for these specific calls, (2) ran the detector on archival recordings from North-western Australia, and (3) compared geographic and seasonal presences and absences to known patterns of humpback whale occurrence. The likelihood of these scenarios being humpback whales is discussed.

Dr Doug Cato’s contributions to the understanding, measurement, and characterization of Australia’s ambient acoustic sea noise environment

In 1966, Dr Douglas H. Cato began his investigation of ambient noise in Australian waters as part of the Royal Australian Navy Research Laboratory’s Project BARRABOOL. His research involved identifying and understanding the various ambient noise mechanisms that limit the performance of operational sonar systems in Australian waters. He is responsible for the “Cato Curves” of ocean noise, which have been used extensively for predicting sonar performance. Similarly, his understanding of the ocean environment and the spatial and temporal variability of ambient undersea noise is exploited by the Royal Australian Navy to ensure effective sonar and submarine performance. Dr Cato is a Fellow of the Acoustical Society of America and his research achievements are published in international peer-reviewed journals including the Journal of the Acoustical Society of America and as book chapters in reference texts in underwater acoustics. In 2012, he was the recipient of the Minister’s Achievement Award in Defence Science for his outstanding contributions in underwater acoustics and the effect of sound on marine mammals. This presentation provides examples of Doug’s achievements in defence science and their significance to the Commonwealth of Australia, Department of Defence.

The search to identify the fish species chorusing along the Southern Australian Continental Shelf

Fish produce sound to support life functions. Some species produce choruses, vocalizing continuously over a prolonged period, significantly raising background sound levels within a characteristic frequency band. Fish choruses demonstrate distinctive spatiotemporal patterns, the identification of which can provide information on fish distribution, spawning behaviors, habitat use, and responses to environmental and anthropogenic stressors. Many fish choruses have been reported in Australian waters, yet, very few source species have been identified. Analysis of previously collected acoustic recordings was undertaken to identify fish chorus presence along the southern Australian continental shelf. Three fish chorus types were identified with frequencies centered at approximately 1000, 2300, and 350 Hz. Acoustic recorders and unbaited underwater video recorders were then deployed simultaneously in an attempt to identify the source species of these fish choruses. The 1000 and 2300 Hz fish choruses were detected on the acoustic recordings, corresponding with video recordings of large aggregations of Red Snapper (Centroberyx gerrardi) and Deep Sea Perch (Nemadactylus macropterus). This pilot study was the first step in an attempt to develop an effective methodology that could be used to identify the source species of fish choruses present in offshore environments.

Distribution and seasonality of the Omura’s whale (Balaenoptera omurai) in Australia based on passive acoustic recordings

The Omura’s whale is one of the most recently described species of baleen whale. Initially known only from stranding and whaling specimens, it has now been identified in all ocean basins excluding the central and eastern Pacific. Unlike most baleen whales that migrate between the poles and the equator seasonally, the Omura’s whale is known to inhabit tropical to sub-tropical waters year-round. In Australian waters, there remain fewer than 30 confirmed visual sightings over the past decade. This study utilizes passive acoustic recordings from 41 locations around Australia from 2005 to 2023 to assess the distribution and seasonality of the Omura’s whale. The seasonal presence of Omura’s whale vocalizations varied by location, with higher presence at lower latitudes. Vocalizations were detected year-round in the Timor Sea and the Kimberley region. The most southerly occurrence of Omura’s whale vocalizations was recorded off the North West Cape, WA. In Australia, the vocalizations detected differ from those of other Indian Ocean Omura’s whale populations. Geographic variation of the vocalization was also observed within Australia, including vocalizations similar but not identical to those of the Omura’s whale detected in the Great Barrier Reef for the first time. The identified seasonal distribution and possible acoustic populations of the species in Australia provides valuable information to assess environmental and anthropogenic pressures on the Omura’s whale and to aid in creating management policies for the species.

The marine fish Terapon theraps calling in tropical Australia

Calling by fish of the family Terapontidae, primarily Terapon theraps, is a dominant component of sea noise recorded in northern Australian tropical coastal waters. These fish produce nightly choruses over a few hours at frequencies from 50 Hz to a few kilohertz, with spectral peaks up to 30 dB above background. Choruses are heard over muddy bottoms <30 m depth. The two commonly heard calls range from 73–260 ms in length and comprised 11–21 pulses with repetition rates of 87–121 Hz. Calls were produced by muscle action on a two chambered swim bladder, and differed by muscle contraction rates, damping, and possibly the opening state of a sphincter separating chambers. Swimbladder carrier frequencies varied from 570–1465 Hz. Source levels varied from 141–154 dB re 1 mPa @ 1 m. Heavily damped alarm calls were sometimes heard. Chorusing fish schools were up to 2 km across although they were diffuse and actively calling fish extended beyond this region. A chorus could be detected out to 8 km from its center, well beyond the detection range of an individual call. Choruses may advertise school location during spawning, be used for mate attraction or mediate gamete release in dark turbid waters.

Snorkelling and breath-hold diving fatalities in Australian waters, 2014 to 2018.

This study investigated snorkelling and breath-hold diving deaths in Australia from 2014-2018 and compared these to those from 2001-2013 to identify ongoing problems and assess the effectiveness of countermeasures. Media reports and the National Coronial Information System were searched to identify snorkelling/breath-hold diving deaths for 2014-2018, inclusive. Data were extracted from witness and police reports, medical histories, and autopsies. An Excel® database was created and a chain of events analysis conducted. Comparisons were made with the earlier report. Ninety-one fatalities (78 males, 13 females, median age 48 years [range 16-80]) were identified with one third likely doing some breath-hold diving. Fifty-two of 77 with known body mass index were overweight or obese. Approximately two thirds were inexperienced snorkellers and 64 were alone. Fifty-one were tourists. Planning shortcomings, such as solo diving and diving in adverse conditions, as well as pre-existing health conditions and inexperience predisposed to many incidents. Primary drowning was the likely disabling condition in 39% of cases with drowning recorded as the cause of death (COD) in two thirds. Cardiac events were the likely disabling conditions in 31% although recorded as the COD in 21% of cases. Increasing age, obesity and associated cardiac disease have become increasingly prevalent in snorkelling deaths and there is a need for improved health surveillance and risk management. Closer supervision of inexperienced snorkellers is indicated. Apnoeic hypoxia from extended breath-holding and poor supervision remain a problem. The increased risk of harvesting seafood in areas frequented by large marine predators needs to be appreciated and managed appropriately.

New Australian frontier in freshwater fish invasion via Torres Strait Islands

AbstractAll continents, excluding Antarctica and the Artic, have been affected by incursion from alien freshwater fish species. Australia has not been spared. Four hundred and fifty species have now been declared on the ornamental importation list, making management a real challenge. With approximately 25 non-native species documented, Papua New Guinea (PNG) has likely some problems with invasive freshwater fish. Many of these species have been intentionally introduced to increase access to food as a protein source for remote communities or have spread naturally from western parts of Java and Indonesia, and now constitute a large biomass on some floodplain areas in PNG. The Torres Strait is located between PNG and northern Queensland and was previously a land bridge, though now under higher sea levels the region exists as a series of approximately 300 islands. The threat of further range extension of freshwater fish from PNG into northern Queensland via the Torres Strait Islands is significant, with two invasive fish species already recorded on northern islands of the Torres Strait (climbing perch, Anabas testudineus which has been continually recorded for the past decade; and recently the GIFT tilapia, Oreochromis niloticus). Here we present a case to control further spread of invasive freshwater fish species towards Australia, using a Land and Sea Ranger program, where Rangers are trained to be confident in the identification of pest fish species and to implement strategies to protect their borders from potential future incursions. The success of this program relies on Rangers to continue partaking in surveillance monitoring of coastal waters, checking and controlling for any new invasive species moving from PNG into Australian waters. We outline the biosecurity obligation under Article 14 of the Treaty between the two nations, which identifies the importance of conservation and protection of coastal floodplains from invasive species, and the spread between both nations.

Genetic divergence of farmed blue mussels (Mytilus sp.) in Australian waters

As valuable ecosystem engineers, blue mussels, are one of the most ecologically and economically important bivalve species in Australia. The need for understanding levels of genetic diversity in both wild and farmed populations of Australian mussels is ever-growing due to the increased risk of disease and decreased fitness associated with the constantly changing global environment. This study, therefore, investigated the phylogenetic relationship, and the genetic variation of farmed blue mussels (Mytilus sp., previously noted as M. galloprovincialis, M. planulatus or a hybrid of both) at four sites along the south coast of Australia, Victoria, South Australia, Western Australia, and Tasmania. Analyses of two genes, Cytochrome c oxidase subunit 1 gene (mtCOI) and the nuclear gene Elongation factor 1 alpha (EF1a) was completed for all mussels sampled. The phylogenetic reconstruction of mtDNA sequences was not able to cluster the samples into species. The analyses of the nuclear marker (EF1a) returned similar results, except that we could conclude the Australian samples not being M. chilensis. Furthermore, the analyses of EF1a revealed the presence of hybridisation, a pattern commonly observed in mussels. The genetic diversity analysis of mtCOI demonstrated that samples from Victoria and Western Australia had the highest genetic diversity, while South Australia had the lowest. When analysing the nuclear EF1a sequences, mussels from Western Australian had the lowest genetic diversity, and the Victorian samples had the highest.The study extended our knowledge on the population genetic variation of farmed blue mussels (Mytilus sp.) along the south coast of Australia. The identified genetic differences between the four southern states of Australia could be interesting for the aquaculture industry when aiming for more adaptable and profitable stocks.

Seasonal stratification and complex local dynamics control the sub-surface structure of marine heatwaves in Eastern Australian coastal waters

Marine heatwaves are extreme seawater temperature events that can have severe impacts on marine life. The extent of the ecological damage depends not only on the easily observed surface signature but on the marine heatwave structure at depth. However, due to a paucity of in situ sub-surface observations the vertical structure of marine heatwaves is poorly understood. Here we analyse the sub-surface coherence and controls of marine heatwaves using one of the world’s longest (28 years) records of daily sub-surface ocean temperature off Sydney, Australia. We show that seasonal stratification, large-scale circulation and local downwelling processes control the vertical coherence of coastal marine heatwaves. We define three classes of marine heatwaves which can extend through the water column, form in the shallow surface layer, or sub-surface independently, and are therefore not always evident in surface data. We conclude that sub-surface data need to be considered in monitoring marine heatwaves in coastal areas where maximum biological damage is reported.

Rapid and permanent cytotoxic effects of venom from Chiropsella bronzie and Malo maxima on human skeletal and cardiac muscle cells

Jellyfish envenomation is a global public health risk; Cubozoans (box jellyfish) are a prevalent jellyfish class with some species causing potent and potentially fatal envenomation in tropical Australian waters. Previous studies have explored the mechanism of action of venom from the lethal Cubozoan Chironex fleckeri and from Carukia barnesi (which causes “Irukandji syndrome”), but mechanistic knowledge to develop effective treatment is still limited. This study performed an in-vitro cytotoxic examination of the venoms of Chiropsella bronzie and Malo maxima, two understudied species that are closely related to Chironex fleckeri and Carukia barnesi respectively. Venom was applied to human skeletal muscle cells and human cardiomyocytes while monitoring with the xCELLigence system. Chiropsella bronzie caused rapid cytotoxicity at concentrations as low as 58.8 μg/mL. Malo maxima venom caused a notable increase in cell index, a measure of cell viability, followed by cytotoxicity after 24-h venom exposure at ≥11.2 μg/mL on skeletal muscle cells. In contrast, the cardiomyocytes mostly showed significant increased cell index at the higher M. maxima concentrations tested. These findings show that these venoms can exert cytotoxic effects and Malo maxima venom mainly caused a sustained increase in cell index across both human cell lines, suggesting a different mode of action to Chiropsella bronzie. As these venoms show different real-world envenomation symptoms, the different cellular toxicity profiles provide a first step towards developing improved understanding of mechanistic pathways and novel envenomation treatment.