SE Australia Research Articles

Millennial and contemporary dynamics of the barrier estuary entrance at Moruya, SE Australia

ABSTRACT This study presents optically stimulated luminescence (OSL) dates, sediment coring, historical maps and charts and photography and airborne LiDAR to reconstruct the millennial and contemporary history of the Moruya River entrance. OSL dating reveals small estuarine beaches were active between 7000 and 5000 years ago, when the entrance was far more open than at present. At that time, a large flood-tide delta infilling a wide immature estuary is likely to have existed. Continued progradation of the Bengello barrier to the north, and the inception of the Moruya Heads barrier to the south from 4500 years onward, progressively constricted the river entrance. Several more low-energy estuarine beaches developed behind the Moruya Heads barrier and are dated to ~4400 and ~2800 years ago. Concurrently, the open mud basin of the estuary infilled with fluvial sediment. Following the arrival of Europeans in the region, in the early to the mid-1800s, engineering works were undertaken in stages to train the estuary entrance for navigation and have further constrained the system. OSL dating of beaches formed as a result of this activity concur with the historical accounts. These contemporary changes to the entrance have modified the estuary hydrodynamics and shifted the sediment transport and ecological regime of the lower estuary.

Data-driven modelling of coastal storm erosion for real-time forecasting at a wave-dominated embayed beach

Emergency managers have an increasing need for tools to enhance preparedness to extreme coastal storms and support disaster risk reduction measures. With the emergence of Early Warning Systems (EWSs) for coastal storm hazards, a fundamental challenge is the accurate prediction of sandy beach erosion at lead times of days to weeks corresponding to an approaching storm event. This work presents a data-driven modelling approach to predict storm-driven beach erosion (shoreline change) using a large dataset of 276 individual storm events at Narrabeen-Collaroy Beach, SE Australia. Correlation analysis between individual storm characteristics and shoreline response at three locations along the embayment with varying exposure to the prevailing waves indicates that cumulative storm wave energy is the dominant driver of storm erosion at this site. This is followed by the pre-storm beach width, storm wave direction and to a minimal extent, storm wave period and water levels. A multi-linear regression model of storm erosion is developed and found to accurately predict shoreline change due to individual storm events (RMSE = 3.7 m–6.4 m). This work highlights the value of high-frequency shoreline data for storm erosion forecasting and provides a framework for real-time forecasting applications.

Foredune morphology: Regional patterns and surfzone–beach–dune interactions along the New South Wales coast, Australia

AbstractForedunes constitute a fundamental part of the coastal environment, acting as a buffer against storm erosion and natural coastal defence. Foredune size and volume play a pivotal role in determining coastal vulnerability to marine hazards, and the governing processes driving variations in foredune morphology, particularly over regional, or larger spatial scales, are still relatively poorly understood. This paper presents a regional‐scale investigation into foredune morphology along the New South Wales (NSW) coast (SE Australia), comprising not only a state‐wide inventory of foredune morphology for use in management/hazard assessment, but also testing long‐standing hypotheses and conceptual models of the physical processes that are driving, or influencing, foredune size. We applied a remote sensing protocol to 47 foredune environments, covering the length of the NSW coastline, comparing morphology (including dune height, width, shape, and volume) of established and incipient foredunes both along, and between, sandy embayments. Results, at regional spatial scales, show that the largest foredunes (volumes up to 850 m3 m−1) occur along the central coast as large, steep landforms; intermediate‐sized dunes (550–650 m3 m−1) were found on both the Mid‐north and Far North coast, and the smallest foredunes (334–380 m3 m−1) occur on the south coast as wider dunes with steep stoss slopes. Surfzone–beach state was found to be the most significant factor influencing foredune size and volume. The more energetic and more dissipative/high‐energy intermediate surfzone–beach states were correlated with larger foredunes (i.e. greater dune volume, width and crest elevation), whereas the lower‐energy surfzone–beach states generally had smaller dunes. Changes in vegetation cover, shoreline orientation and associated onshore (and alongshore) wind systems were also demonstrated to be important factors in determining foredune morphology. The largest foredunes in NSW generally occur to the north of embayments, with dune size decreasing southward with decreasing exposure to wind/wave energy.

Living root contributions dominate vertical accretion, but not carbon burial, in two SE Australian tidal wetlands

Organic matter derived from allochthonous and autochthonous sources makes an important contribution to the accumulation and burial of “blue carbon” in tidal wetlands. Organic matter accretion is also a mechanism by which tidal marshes and mangroves adjust vertically to the pressure of sea-level rise, through feedbacks between marsh autotrophic productivity and hydroperiod. However, the separate contributions of inorganic matter, detrital organic matter and living roots to marsh accretion have rarely been documented. We used a network of Surface Elevation Table-Marker Horizon (SET-MH) stations SE Australia as a benchmark against which the accumulation of inorganic, organic and living root material was measured. Established in 2000–2002, the SET-MH stations allowed for sampling accretion and elevation gain in mangrove and saltmarsh in fluvial and marine sand geomorphic settings. We found living root material to be the dominant contributor to the volume of accretion above feldspar marker horizons and elevation gain over the 20-year experimental period. However, detrital organic matter, being of lower bulk density than living roots, contributed most to carbon burial. Higher rates of accretion and elevation gain were associated with higher contributions of pore volume, and lower contributions of inorganic matter. The rate of subsidence increased with accretion and was lower where inorganic matter contributions to mass were higher. The results highlight the importance of biological and hydrological contributions to accretion and elevation gain in a region subject to riverine minerogenic inputs.

3D seismic analysis of complex faulting patterns and fluid escape features and their relation to Late Cenozoic Magmatism in the Bass Basin, offshore SE Australia

Abstract Igneous intrusions in sedimentary petroleum basins are often perceived as having a negative impact on the elements of the petroleum system, though the impact of intrusion-related deformation features on petroleum systems and broader geoenergy applications is not well understood. In this study, we use 3D seismic reflection data to document a variety of deformation styles that are spatially and temporally associated late Cenozoic magmatic activity in the Bass Basin, offshore southeastern Australia; three types of normal fault systems (conjugate faults, concentric faults, radial faults) and fluid escape pipes. These deformation features occur in the overburden up to ∼600 m above underlying igneous intrusions, within the Eocene to Miocene Demons Bluff and Torquay formations. The conjugate faults bound graben and are interpreted to have formed in response to underlying dyke intrusions. The radial faults are interpreted to have formed in response to overburden uplift, though the link between these and associated igneous activity is less clear. We identify 101 fluid escape features that show variation in both the morphology of their surficial depressions and of the seismic reflection characteristics of their infilling deposits. These features are interpreted to be hydrothermal or volcanic vents with underlying pipe-like feeders, depending on their spatial association with adjacent or underlying igneous intrusions. The concentric fault systems are associated with surficial depressions, and quantitative analysis of reflection sags within these depressions suggest that they are a result of subsurface subsidence in response to formation of maar-craters. The intrusion-related deformation features documented in this study may have multiple effects on working petroleum systems, such as providing secondary fluid flow pathways that can either reduce seal integrity, or enabling migration of fluids into shallower reservoirs.

Influence of habitat features on the colonisation of native and non-indigenous species

Marine artificial structures provide substrates on which organisms can settle and grow. These structures facilitate establishment and spread of non-indigenous species, in part due to their distinct physical features (substrate material, movement, orientation) compared to natural habitat analogues such as rocky shores, and because following construction, they have abundant resources (space) for species to colonise. Despite the perceived importance of these habitat features, few studies have directly compared distributions of native and non-indigenous species or considered how functional identity and associated environmental preferences drive associations. We undertook a meta-analysis to investigate whether colonisation of native and non-indigenous species varies between artificial structures with features most closely resembling natural habitats (natural substrates, fixed structures, surfaces oriented upwards) and those least resembling natural habitats (artificial materials, floating structures, downfacing or vertical surfaces), or whether functional identity is the primary driver of differences. Analyses were done at global and more local (SE Australia) scales to investigate if patterns held regardless of scale. Our results suggest that functional group (i.e., algae, ascidians. barnacles, bryozoans, polychaetes) rather than species classification (i.e., native or non-indigenous) are the main drivers of differences in communities between different types of artificial structures. Specifically, there were differences in the abundance of ascidians, barnacles, and polychaetes between (1) upfacing and downfacing/vertical surfaces, and (2) floating and fixed substrates. When differences were detected, taxa were most abundant on features least resembling natural habitats. Results varied between global and SE Australian analyses, potentially due to reduced variability across studies in the SE Australian dataset. Thus, the functional group and associated preferences of the highest threat NIS in the area should be considered in design strategies (e.g., ecological engineering) to limit their establishment on newly built infrastructure.

Adjoint inversion of antipodal PKPab waveforms for P wave velocity anomaly at the base of the lower mantle

We perform an adjoint inversion by using antipodal PKPab phases to estimate the heterogeneous Vp structure at the base of the lowermost mantle. We have carefully examined antipodal stations with high S/N ratios during the past 30 years and selected 20 source-receiver pairs with the epicentral distances >179.0 degree and the Mw <7.0. We have used the spectral-element method on the Earth Simulator of JAMSTEC to calculate the synthetic seismograms for a heterogeneous mantle Vp model with the accuracy of period about 8 s (110 km wavelength at the CMB). We have set up the time window to retrieve the PKPab phase from the vertical component of both observed and computed seismograms to calculate the adjoint source to obtain the sensitivity kernels of Vp in the mantle. The computed Vp sensitivity kernel for each event shows the characteristic annulus pattern in the lowermost mantle, which covers a large area of the CMB. The twenty PKPab earthquake-station pairs in this antipodal study contribute the equivalent of about 3140 measurements at the CMB—compared with 1871 previously studied—and provide new data. Therefore, although the number of individual source-receiver pairs is not large, the summed sensitivity kernels of the PKPab phase for Vp structure at the base of the mantle may be sufficient to model heterogeneity of the Vp structure at the CMB. We summed each event kernel to set up a sensitivity kernel of Vp in the lowermost mantle and iterated the inversion to estimate a heterogeneous structure in D″. Although we have iterations that dominantly affect both South America and the South Pacific, the summary final model shows features within South of Africa, South Pacific, SE Australia, and Central & South America. Keeping the Vs model fixed, we map the CMB Vp heterogeneity measured by the parameter Rs,p = dlnVs/dlnVp and find qualitative, proximal correspondence with the degree-2 pattern of Large Low Velocity Shear Provinces observed in shear tomographic models: in the Pacific and Africa Rs,p > 2.0, whereas the surrounding edges of the edges of the Pacific show Rs,p < 2.0.

Out of Africa: Linked continents, overland migration and differential survival explain abundance of Proteaceae in Australia

The centres of diversification of the iconic family Proteaceae are in South Africa and southern Australia. Since the ancestors of the family can be traced to NW Africa our task was to explain how all subfamilies (Proteoideae, Grevilleoideae, Persoonioideae) managed to reach Australia and we propose the pathway: (Africa (N South America (S South America (Antarctica (Australia))))). Our dated molecular phylogeny shows that the family arose 132 million years ago (Ma), and by 125 Ma had separated into the three subfamilies that remain dominant today. The age and location of records for 420 fossil pollen with Proteaceae affinities were collated per continent and submitted to curve-fitting analysis. This showed spread of early Proteaceae into N South America from ∼121 Ma that was able to continue for another 20–25 My. These three subfamilies (plus Carnarvonia) travelled south through South America and Antarctica, crossing the Weddellian Isthmus from ∼110 Ma, to reach southern Australia by ∼104 Ma. The history of Proteaceae in South America mimics that of Africa, where Grevilleoideae diversified instead of Proteoideae that died out. Entry to Australia via Antarctica was possible until ∼70 Ma at its SW corner and 45 Ma at its SE (Tasmanian) corner enabling the three subfamilies (and Carnarvonia) restricted entry into Australia over 35–60 million years. The SW Australian sclerophyll flora became the centre of diversification and emigration at the species level of all but the rainforest (mesophyll) Grevilleoid/Proteoid clades within Australia. Close genetic links between clades in South Africa (the centre of diversification of the sclerophyll flora in Africa) and SW Australia are the product of disparate migratory histories from their common ancestor in NW Africa, differential survival among subfamilies and parallel evolution in matched environments. SE Australia became the centre of diversification at the subtribe level. Close genetic links between clades in South America and SE Australia are the product of long-distance dispersal from their common ancestor in N South America, genetic stability in matched environments and eventual vicariance.

Novel ecological interactions alter physiological responses of range-extending tropical and local temperate fishes under ocean warming

Global warming facilitates species range-expansions, leading to novel biological interactions between local and range-expanding species. Little is still known of how such novel interactions modify the performance of interacting species or how these interactions might be altered under climate change. Here, we used an aquarium experiment to investigate the novel ecological interactions between a poleward range-extending coral reef damselfish (“tropical-vagrant”) and a local temperate species (“temperate-local”) collected from a climate warming hotspot in SE Australia. We measured the effect of novel interactions (isolated vs. paired fish species) on energy expenditure (activity levels, oxidative stress, and antioxidant responses), energy gain (feeding rates), and growth rates of both fish species under present-day (23 °C) and future ocean temperatures (26 °C). Short-term growth rates were faster in both species under novel interactions (paired species), regardless of elevated temperature. Compared to isolated species, activity level, feeding rate and oxidative stress level were also higher in the paired temperate fish but not in the paired tropical fish. The tropical fish showed an increased feeding rate and long-term growth under elevated temperature, irrespective of novel interactions. We conclude that novel ecological interactions under climate change can be an important driver of physiological traits in sympatric tropical and temperate fishes and can mediate critical physiological performance of fishes under ocean warming.

Decadal changes in vegetation cover within coastal dunes at the regional scale in Victoria, SE Australia

Vegetation is a critical boundary condition for the stability of coastal dunes. Globally, vegetation cover is increasing on the coast with many dunes being stabilised in the past decades. This pattern is driven by site-specific (e.g., coastal management) and global (e.g., climatic changes) factors. This study examines changes in dune vegetation during the past six decades at the regional scale along the southeast coast of Australia to understand the relative importance of the climate and human interventions in vegetation cover change. A total area of >31,000 ha, comprising 53% of the open coast of Victoria was studied. Since the 1960's, a general trend of dune stabilisation and coastal greening has occurred with total vegetation cover increasing from 61% to 84% coverage until 2020. At the regional scale, the increase in vegetation cover has been primarily driven by both climatic-related drivers, such as rising temperature, elevating CO2 concentrations and declining windiness, and state-wide coastal management interventions (e.g., marram grass planting, fencing, fire control, grazing removal). The only areas where there was a decline in total area of vegetation was where substantial coastal recession had occurred. The decrease in vegetation is a result of a loss of land area rather than a loss of plant biomass over the dunefields. Therefore, it is considered that the overall decadal changes in both climate and coastal management are forcing the dunes toward a more stabilised state at the regional scale. At the same time, compelling local drivers (e.g., storms and local sediment deficiency) can be the most crucial factor to regulate vegetation change and shift dune mobility at the site-specific scale.

Information management and cultural evolution in Aboriginal Australia (In light of the cultural heterochrony hypothesis)

Following a recent re-evaluation of evidence from an archaeological site in SE Australia, the possibility of a 120 thousand years (ka) old human presence in the Fifth Continent has been suggested. However, the commonly accepted date for the peopling of Australia remains within the range of 50 - 65 ka. Even if the newly proposed date were halved, an uninterrupted 60 ka continuity in the same territory would raise a few questions regarding the transmission mechanisms that have enabled the retention of the massive amount of knowledge acquired during such an extended period, especially when considering the lack of demographic strength, which is believed to be a prerequisite for effective social learning. I argue that the emergence, developmental rate, and extent of Australian culture reflect an ‘additive’ evolutionary strategy centred on a ritually regulated feedback loop between the volume of information flow and the level of social elaboration. The model forwarded in this paper is at odds with current theoretical approaches to cultural evolution in which Aboriginal traditions are often portrayed as living examples of Pleistocene cross-cultural universals.

THE SIZE INHERITED AGE EFFECT ON RADIOCARBON DATES OF ALLUVIAL DEPOSITS: REDATING CHARCOAL FRAGMENTS IN A SAND-BED STREAM, MACDONALD RIVER, NSW, AUSTRALIA

ABSTRACT Radiocarbon dates on charred plant remains are often used to define the chronology of archives such as lake cores and fluvial sequences. However, charcoal is often older than its depositional context because old-wood can be burnt and a range of transport and storage stages exist between the woodland and stream or lake bed (“inherited age”). In 1978, Blong and Gillespie dated four size fractions of charcoal found floating or saltating in the Macdonald River, Australia. They found larger fragments gave younger age estimates, raising the possibility that taphonomic modifications could help identify the youngest fragments. In 1978 each date required 1000s charcoal fragments. This study returns to a sample from the Macdonald River to date individual charcoal fragments and finds the inherited age may be more than 1700 years (mode 250 years) older than the collection date. Taphonomic factors, e.g., size, shape or fungal infestation cannot identify the youngest fragments. Only two fragments on short-lived materials correctly estimated the date of collection. In SE Australia, this study suggests that wood charcoal will overestimate the age of deposition, taphonomic modifications cannot be used to identify which are youngest, and multiple short-lived materials are required to accurately estimate the deposition age.

Death of a palaeochannel: Slow abandonment of an avulsed channel on the Riverine Plains, SE Australia

AbstractAvulsion of rivers can be a gradual process that is associated with a metamorphosis of channel pattern or changed channel characteristics. The processes controlling avulsion, and hence anastomosis, often operate too slowly to study by measuring active river systems, and hence well preserved Late Quaternary rivers offer one of the best ways to study the long‐term development of avulsive systems. The modern and ancient channels of the Murrumbidgee River provide a classic example of long‐lived, semi‐static anastomosis, operating on timescales that include stadial and interstadial climate cycles. Over the last glacial cycle, regional avulsions have occurred every ~12 ka while maintaining an anastomosing pattern through the slow infill of abandoned channels. The Yanco Creek Palaeochannel System emerged from a period of high discharge linked to snowmelt in the terminal Pleistocene. Here, geomorphological mapping of the Yanco System was conducted together with single‐grain, optically stimulated luminescence dating of sediments in the channel belt. Since the main phase of channel construction during the Last Glacial Maximum, the Yanco system has functioned as a flood conduit and minor anabranch of the Murrumbidgee River, with reworking of ancient channel sediments by an underfit stream that is ongoing to the present day. Our new ages of ~13–14 ka are interpreted as channel sedimentation during an underfit phase following avulsion. The prevalence of full and partial avulsion in this environment may be complicating palaeohydrological interpretations of ages for channel activity, and reworking has gone unrecognised. We contend that some previous interpretations of the significance of ages for sediments collected from palaeochannels in the Riverine Plain may need revision.

Subtropical coral expansion into SE Australia: a haven for both temperate and expatriating tropical reef fishes

We examined reef fish assemblages in and adjacent to a newly established coral bed (subtropical Pocillopora aliciae) in temperate south-eastern Australia, to understand whether novel coral habitat is facilitating assemblages of range-expanding tropical and local temperate fishes. This is the first comprehensive assessment of fish species associating with this novel coral habitat within a temperate environment. Twenty fish species were observed associating with the coral (8 tropical and 12 temperate). Both temperate and tropical species were observed at greater (up to 48 times higher) densities on the coral than on nearby temperate rocky reef in the area, suggesting that the corals generally concentrate fish and may aid in tropicalisation for species that use subtropical coral as habitat. Future research should investigate the ongoing expansion of this coral, the relative quality of coral habitat for fish in temperate regions and the potential implications for functioning of temperate rocky reef ecosystems.

On the virtues and pitfalls of combined laser ablation Rb–Sr biotite and U–Pb monazite–zircon geochronology: an example from the isotopically disturbed Cape Woolamai Granite, SE Australia

Abstract Different mineral clocks in granite can provide age information reflecting various aspects of rock formation, including cooling or post-emplacement fluid–rock interaction. However, the dating tool chosen can yield inconclusive age information due to differences in closure temperatures and susceptibility to fluid alteration among chronometers. This has led to an inferred superiority of U–Pb in zircon over U–Pb in monazite or Rb–Sr in mica. Here, we investigate age systematics using Rb–Sr biotite grains, U–Pb in monazite and zircon in a Devonian granite from Australia. Single-grain laser ablation ICP-MS/MS biotite analyses are combined with zircon–monazite U–Pb ages and trace element systematics. Textural and trace element evidence combined with age systematics reveals a Rb–Sr closure age of c. 360–330 Ma relative to a putative 364 Ma emplacement age, suggesting hydrothermal alteration of the granite. Trace element systematics and magnetic susceptibility in biotite grains reflect their partial chemical reset and fluid overprint in the granite. However, similar systematics are also observed for zircon and monazite. Our multiple chronometer dating approach, studied with modern laser-ablation methods, highlights the need for detailed investigation of isotope and trace element systematics in single grains and that individual ages should be used cautiously when dating altered granitoids.

Identifying and Attributing Regime Shifts in Australian Fire Climates

This paper introduces and analyzes fire climate regimes, steady-state conditions that govern the behavior of fire weather. A simple model representing fire climate was constructed by regressing high-quality regional climate averages against the station-averaged annual Forest Fire Danger Index (FFDI) for Victoria, Australia. Four FFD indices for fire years 1957–2021 were produced for 10 regions. Regions with even coverage of station-averaged total annual FFDI (ΣFFDI) from 1971–2016 exceeded Nash–Sutcliffe efficiencies of 0.84, validating its widespread application. Data were analyzed for shifts in mean, revealing regime shifts that occurred between 1996 and 2003 in the southern states and 2012–2013 in Queensland. ΣFFDI shifted up by ~25% in SE Australia to 8% in the west; by approximately one-third in the SE to 7% in the west for days above high fire danger; by approximately half in the SE to 11% in the west for days above very high, with a greater increase in Tasmania; and by approximately three-quarters in the SE to 9% in the west for days above severe FFDI. Attribution of the causes identified regime shifts in the fire season maximum temperature and a 3 p.m. relative humidity, with changing drought factor and rainfall patterns shaping the results. The 1:10 fire season between Regimes 1 and 2 saw a three to seven times increase with an average of five. For the 1:20 fire season, there was an increase of 2 to 14 times with an average of 8. Similar timing between shifts in the Australian FFDI and the global fire season length suggests that these changes may be global in extent. A trend analysis will substantially underestimate these changes in risk.

VARMA model parameterization using MLLE approach for intraday wind power forecasting application

AbstractAccurate intraday wind power forecasting (WPF) is required by system operators to mitigate challenges arising from small‐scale grid integration of intermittent wind power. This low‐level integration of wind energy into the system urges quality deterministic forecast. Multivariate statistical models considering spatiotemporal correlations are commonly used for such WPF. However, prudent parameterization is a necessity to improve deterministic forecasts even in smaller datasets. This article proposes a computationally efficient vector autoregressive moving average (VARMA) based intraday WPF model that uses the novel maximum log‐likelihood estimation (MLLE) approach to estimate the best‐fit model parameters. MLLE approach reduces the spatiotemporal fitting error by approximately 15% with computational time deduction by more than 25%. Furthermore, an advanced accuracy in parameter estimation (AIPE) technique supports the MLLE approach to obtain the optimal training window length for computing distribution parameters with narrow confidence intervals. Proposed centralized forecast model is implemented on a group of Wind Farms (WFs) in SE Australia. Pre‐processing of wind power generation data is ensured using the Yeo–Johnson transformation and stationarity concept. Proposed model is accurate and computationally efficient as compared to benchmark models in terms of accuracy and computational time. An appreciated forecast quality is achieved using the proposed model having only 0.20 MW and 0.29 MW mean normalized RMSE for 3 and 10 WFs studies, respectively. Possible applicability of the proposed model includes an overall improvement in intraday decision‐making of wind energy producers and system operators.

Genetic assessment of the value of restoration planting within an endangered eucalypt woodland

Assessment of woodland restoration often focusses on stand demographics, but genetic factors likely influence long-term stand viability. We examined the genetic composition of Yellow Box (Eucalyptus melliodora) trees in endangered Box-Gum Grassy Woodland in SE Australia, some 30 years after planting with seeds of reportedly local provenance. Using DArT sequencing for 1406 SNPs, we compared genetic diversity and population structure of planted E. melliodora trees with remnant bushland trees, paddock trees and natural recruits. Genetic patterns imply that natural stands and paddock trees had historically high gene flow (among group pairwise FST = 0.04–0.10). Genetic diversity was highest among relictual paddock trees (He = 0.17), while diversity of revegetated trees was identical to natural bushland trees (He = 0.14). Bayesian clustering placed the revegetated trees into six genetic groups with four corresponding to genotypes from paddock trees, indicating that revegetated stands are mainly of genetically diverse, local provenance. Natural recruits were largely derived from paddock trees with some contribution from planted trees. A few trees have likely hybridised with other local eucalypt species which are unlikely to compromise stand integrity. We show that paddock trees have high genetic diversity and capture historic genetic variety and provide important foci for natural recruitment of genetically diverse and outcrossed seedlings.

Anchor scour from shipping and the defaunation of rocky reefs: A quantitative assessment

Anchor scour from shipping is increasingly recognised as a global threat to benthic marine biodiversity, yet no replicated ecological assessment exists for any seabed community. Without quantification of impacts to biota, there is substantial uncertainty for maritime stakeholders and managers of the marine estate on how these impacts can be managed or minimised. Our study focuses on a region in SE Australia with a high proportion of mesophotic reef (>30 m), where ships anchor while waiting to enter nearby ports. Temperate mesophotic rocky reefs are unique, providing a platform for a diversity of biota, including sponges, ahermatypic corals and other sessile invertebrates. They are rich in biodiversity, provide essential food resources, habitat refugia and ecosystem services for a range of economically, as well as ecologically important taxa. We examined seven representative taxa from four phyla (porifera, cnidaria, bryozoan, hydrozoa) across anchored and ‘anchor-free’ sites to determine which biota and which of their morphologies were most at risk. Using stereo-imagery, we assessed the richness of animal forest biota, morphology, size, and relative abundance. Our analysis revealed striking impacts to animal forests exposed to anchoring with between three and four-fold declines in morphotype richness and relative abundance. Marked compositional shifts, relative to those reefs that were anchor-free, were also apparent. Six of the seven taxonomic groups, most notably sponge morphotypes, exhibited strong negative responses to anchoring, while one morphotype, soft bryozoans, showed no difference between treatments. Our findings confirm that anchoring on reefs leads to the substantial removal of biota, with marked reductions of biodiversity and requires urgent management. The exclusion of areas of high biological value from anchorages is an important first step towards ameliorating impacts and promoting the recovery of biodiversity.

Interpreting the mammal deposits of Cloggs Cave (SEAustralia),GunaiKurnaiAboriginal Country, through community‐led partnership research

AbstractPalaeontological animal bone deposits are rarely investigated through research partnerships where the local First Nations communities have a defining hand in both the research questions asked and the research processes. Here we report research undertaken through such a partnership approach at the iconic archaeological site of Cloggs Cave (GunaiKurnai Country, East Gippsland), in the southern foothills of SE Australia's Great Dividing Range.A new excavation was combined with detailed chronometric dating, high‐resolution 3D mapping and geomorphological studies. This allowed interpretation of a sequence of stratigraphic layers spanning from a lowermost excavated mixed layer dated to between 25,640 and 48,470 cal BP, to a dense set of uppermost, ash layers dated to between 1460 and 3360 cal BP. This long and well‐dated chronostratigraphic sequence enabled temporal trends in the abundant small mammal remains to be examined.The fossil assemblage consists of at least 31 taxa of mammals which change in proportions through time. Despite clear evidence that the Old Ancestors repeatedly carried vegetation into the cave to fuel cool fires (no visible vegetation grows in Cloggs Cave), we observed little to no evidence of cooking fires or calcined bone, suggesting that people had little involvement with the accumulation of the faunal remains. Small mammal bones were most likely deposited in the cave by large disc‐faced owls,Tyto novaehollandae(Masked Owl) orTyto tenebricosa(Sooty Owl).Despite being well dated and largely undisturbed, the Cloggs Cave assemblage does not appear to track known Late Quaternary environmental change. Instead, the complex geomorphology of the area fostered a vegetation mosaic that supported mammals with divergent habitat preferences. The faunal deposit suggests a local ancestral landscape characterised by a resilient mosaic of habitats that persisted over thousands of years, signalling that the Old Ancestors burned landscape fires to encourage and manage patches of different vegetation types and ages within and through periods of climate change.Read the freePlain Language Summaryfor this article on the Journal blog.