Lake Macquarie Research Articles

Sub-lethal effects of metal(loid) contamination on the halophyte Sarcocornia quinqueflora with links to plant photosynthetic performance and biomass – A field study

Two saltmarsh locations within Lake Macquarie, NSW, Australia were selected to investigate the uptake and partitioning of metal(loid)s Cu, Zn, As, Se, Cd and Pb in the Australian saltmarsh halophyte, Sarcocornia quinqueflora and the associated sub-lethal effects of metal(loid)s on plant health, including photosynthetic performance, biomass, and productivity. Metal(loid)s primarily accumulated to roots (BCF > 1). Barriers to transport were observed at the root to non-photosynthetic stem transition (TF < 1) for all metal(loid)s, suggesting this species is suitable for phytostabilisation. Sediment and plant tissue metal(loid) concentrations were significantly correlated with photosynthetic performance and plant biomass. As such, the action of sediment and tissue metal(loid)s on photosynthetic performance and the subsequent effect on biomass of S.quinqueflora appear to be suitable targets for molecular analyses to further elucidate mechanisms responsible for the observed adverse effects and the development of adverse outcome pathways.

Above and below-ground bacterial communities shift in seagrass beds with warmer temperatures

Current rates of ocean warming are predicted to exacerbate ongoing declines in seagrass populations. Above-ground responses of seagrass to increasing temperatures have been studied from a direct physiological perspective while indirect effects, including changes to microbially-mediated below-ground processes, remain poorly understood. To test potential effects of increased temperature on seagrass growth and associated microbial communities, we sampled seagrass beds experiencing ambient and elevated water temperatures at Lake Macquarie, Australia. Sites with warmer water were associated with a plume from a power station discharge channel with temperatures analogous to conditions predicted by 2100 under current rates of ocean warming (+3°C). The microbial community composition in both sediments and leaf tissues varied significantly between warm and ambient water temperatures with higher relative abundances of putative sulphate-reducing bacteria such as Desulfocapsaceae, Desulfobulbaceae and Desulfosarcinaceae in sedimentary communities in warm water. Above-ground biomass and seagrass growth rates were greater at warm sites while below-ground biomass and detrital decomposition rates showed no difference suggesting potential buffering of temperature effects below-ground. These findings suggest a 3°C rise in temperate regions is unlikely to induce mortality in seagrass however, it may shift microbial communities towards more homogenous structure and composition.

Perceptions of the acceptability and effectiveness of a localised lifestyle medicine initiative to improve mental health – the lift project

ABSTRACT Objective Evaluate survey respondents’ perceptions concerning the acceptability and effectiveness of a localised, community-based mental health program. Method Avondale University and Lake Macquarie City Council partnered to implement an online, lifestyle-based program for all Council residents during a COVID-19 lockdown period. The University and Council promoted the program through established networks, resulting in 2390 registrations representing 4041 participants. Researchers invited registered users to respond to a post-program survey assessing their perceptions concerning program satisfaction, mental health benefits, and self-efficacy for managing mental health. Qualitative questions probed respondents’ likes and dislikes and were analysed thematically. Results Response rates were low, 6% (138/2390) of registered participants completed the post-program survey. Of the 138 responses, 99% indicated they would recommend the program to others, and 94% believed they gained skills to manage their mental well-being into the future. Themes generated from the qualitative data indicated that respondents liked the video content and delivery style, community camaraderie, personal empowerment, and easy accessibility. Some respondents found online accessibility problematic, disliked the delivery style, and experienced technical difficulties. Discussion The findings from a limited number of respondents indicate that a localised, community-based lifestyle program may offer a replicable model that is acceptable and effective in improving perceived mental health and self-efficacy in managing mental well-being. Survey respondents valued the practical content, community togetherness and emphasis on self-empowerment.

Upregulation of antioxidant enzymes contribute to the elevated tolerance of Juncus acutus offspring from metal contaminated environments

Long-term environmental exposure to metals e.g. zinc (Zn), may allow saltmarsh halophytes to develop metal tolerance to improve the chance of survival of their progeny in future metal-contaminated scenarios. Juncus acutus seeds were collected from mature parents (F0) inhabiting a legacy Zn-contaminated location (Cockle Creek) and an uncontaminated reference location (Swansea) of Lake Macquarie, NSW, Australia. Seeds (J. acutus) were exposed to Zn (0.00 mM (control), 0.01 mM (effective concentration, EC10) and 0.74 mM (EC50)) and resultant germinants (F1) were allowed to grow until 15 days. Seedling growth parameters i.e. biomass, root length and 1st leaf length, and seedling biochemical responses i.e. superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) antioxidant enzyme activity and lipid peroxidation products, malondialdehyde (MDA), were examined in order to assess if enzymes may be implicated in conferring tolerance to the offspring of metal-exposed parents. Control locations exhibited significantly greater declines in biomass and root length with Zn dose compared to seed from contaminated locations, suggesting F1 offspring from contaminated parents were conferred tolerance to Zn. Furthermore, significant upregulation of CAT and GPx enzymes were evident in the seedlings derived from parents of contaminated locations. These are the antioxidative enzymes responsible for minimizing metal-induced oxidative stress, and may, in part, be responsible for increasing seedling fitness and observed tolerance.

Sea level rise and the increasing frequency of inundation in Australia’s most exposed estuary

The large tidal lake systems along the Southeast Australian coast are amongst the most vulnerable estuaries in Australia to the effects of sea level rise. In these lakes, reduced tide ranges compared with the ocean, in combination with modest flood extremes, have allowed development to occur in close vertical proximity to the current mean sea level. In this study, we examine water levels within Lake Macquarie, Australia’s most exposed estuary to sea level rise. We analyse water level data from the entrance channel and the lake to investigate recent changes to the frequency and duration of inundation or flooding of low-lying streets and examine the potential impacts of future rises in sea level. Our analysis shows that the numbers of days each year when water levels exceed those of low-lying streets, while subject to some variability, have increased significantly over recent decades. The increasing frequency of inundation is attributed to both mean sea level rise and an increase in tide range over the period of available data, which is thought to be associated with scour processes related to ongoing morphological adjustment to entrance training works undertaken over a century ago. Comparison of the projected behaviour of lake and open coast water levels under sea level rise shows the lake has significantly greater sensitivity to sea level rise. Projected inundation frequency for a given amount of sea level rise within the lake is double that of open coast sites, exposing infrastructure in the estuary to increasing risk of damage.

Implications of habitat use and movement of stocked juvenile dusky flathead (Platycephalus fuscus) on stock enhancement release strategies

AbstractStocking of marine fish into coastal systems to augment natural recruitment is a growing practice adopted by fisheries managers around the world. Releasing fish directly into well‐resourced nursery grounds greatly increases survival and retention of stocked individuals but requires an understanding of juvenile habitat requirements. In eastern Australia, the dusky flathead (Platycephalus fuscus) is a highly regarded recreationally targeted species and the focus of an emerging stock enhancement programme, although little is known of their specific nursery habitat. Using acoustic telemetry, hatchery‐reared juveniles were monitored in Lake Macquarie to quantify habitat use and dispersal. Sandy areas adjacent to edges of seagrass beds were favoured, likely as foraging habitat. Within 5 weeks after release, fish were detected 5 km from the release site, but only at locations containing seagrass beds, so stocked fish likely disperse around estuaries to regions with suitable habitat. Future releases of dusky flathead should target areas containing patchy seagrass‐sand to optimise stocking outcomes. Beyond fisheries enhancement programmes, our findings highlight the importance of structured habitat, such as seagrass beds, for juvenile fish.

Offspring of metal contaminated saltmarsh (Juncus acutus) exhibit tolerance to the essential metal Zn but not the nonessential metal Pb

Halophytes residing in metal-contaminated saltmarsh habitats may employ strategies to enhance fitness of the next generation. We aimed to test the hypothesis that Juncus acutus individuals inhabiting metal-contaminated locations would experience elevated tolerance of offspring to metals compared to plants residing in locations with no metal contamination history. J. acutus seeds (F1 generation) were collected from F0 parent plants residing at eight locations of a contemporary sediment metal gradient (contaminated to uncontaminated) across the coast of NSW, Australia (Hunter river, Lake Macquarie and Georges River). Seeds were exposed in the laboratory to incremental Zn (0.0–1.6 mM) and Pb (0.0–0.50 mM) for nine (9) days, and % germination, germination rate, root elongation and vigour index were assessed for the determination of tolerance. Greater root accumulation (BCF = 1.01) of Zn and subsequent translocation to aerial parts (culm BCF = 0.58 and capsule BCF = 0.85) were exhibited in parents plants, whereas Pb was excluded from roots (BCF = 0.60) and very little translocation to aerial portions of the plant was observed (culm BCF = 0.02 and capsule BCF = 0.05). F1 offspring exhibited tolerance to Zn with EC50 (% germination) significantly correlated with their parents' culm (R2 = 0.93, p = 0.00) and capsule (R2 = 0.57; p = 0.03) Zn. No correlations were observed between offspring Pb tolerance and Pb in parents’ plant tissues. Enhanced tolerance to the essential metal Zn may be because Zn is very mobile in the parent plant and seeds experience greater Zn load as a significant portion of sediment Zn reaches capsules (85%). Thus, Zn tolerance in J. acutus seeds is likely attributable to acclimation via maternal transfer of Zn; however, further manipulative experiments are required to disentangle potential acclimation, adaptation or epigenetic effects in explaining the tolerance observed.

Physiological responses of the upside-down jellyfish, Cassiopea (Cnidaria: Scyphozoa: Cassiopeidae) to temperature and implications for their range expansion along the east coast of Australia

Upside-down jellyfish (Cassiopea spp.) are predominantly tropical, but there have been recent reports of medusae in temperate environments. In 2017 they were recorded in temperate Lake Macquarie, Australia, where they have a tendency to disappear from this area through late winter (Austral, August). This raises questions about the role of temperature as a controlling factor of their abundance, and future density increases with warming oceans as a result of climate change. Here we test the degree to which temperature may drive winter die-offs of the medusa stage in temperate environments, and how this may change with altered thermal regimes. We assessed the physiological response of Cassiopea (via measurement of bell pulsation rate, bell diameter, and routine metabolic rate) under a regime mirroring Lake Macquarie's seasonal temperature drop (autumn into winter) compared to three other temperature profiles: 1) seasonal profile with predicted climate change (+ 2 °C), 2) stable temperatures equivalent to the end of autumn (20 °C) and, 3) a profile that mimicked the increasing temperatures from winter into summer (20 °C increasing to 24 °C). Overall, the results indicate that, compared to the ambient state, elevated temperatures can have positive effects on performance of Cassiopea medusae as evidenced by greater bell pulsation rate and bell diameter. The rate of bell diameter decline was lower in all elevated temperature treatments relative to the ambient profile. This highlights the capacity for elevated temperatures in the future to slow the rate of bell degradation, contributing to an increased probability of overwinter survival, thus increasing the size and duration of Cassiopea blooms in temperate waterways such as Lake Macquarie.

Genome-wide SNPs detect fine-scale genetic structure in threatened populations of squirrel glider Petaurus norfolcensis

Australian arboreal mammals are experiencing significant population declines, particularly due to land clearing and resulting habitat fragmentation. The squirrel glider, Petaurus norfolcensis, is a threatened species in New South Wales, with a stronghold population in the Lake Macquarie Local Government Area (LGA) where fragmentation due to urbanization is an ongoing problem for the species conservation. Here we report on the use of squirrel glider mitochondrial (385 bp cytochrome b gene, 70 individuals) and nuclear DNA (6,834 SNPs, 87 individuals) markers to assess their population genetic structure and connectivity across 14 locations sampled in the Lake Macquarie LGA. The mitochondrial DNA sequences detected evidence of a historical genetic bottleneck, while the genome-wide SNPs detected significant population structure in the Lake Macquarie squirrel glider populations at scales as fine as one kilometer. There was no evidence of inbreeding within patches, however there were clear effects of habitat fragmentation and biogeographical barriers on gene flow. A least cost path analysis identified thin linear corridors that have high priority for conservation. These areas should be protected to avoid further isolation of squirrel glider populations and the loss of genetic diversity through genetic drift.

The accumulation and distribution of arsenic species and selected metals in the saltmarsh halophyte, spiny rush (Juncus acutus)

This study examined the accumulation of As species, Se, Cu, Zn, Cd and Pb in the halophyte Juncus acutus, collected from three anthropogenically impacted estuaries in NSW, Australia. As concentration ranged from 4 to 22 μg/g at Georges River, 2–16 μg/g at Lake Macquarie and 6 μg/g at Hunter Estuary. Inorganic As was accumulated mainly in roots with low translocation to culm with a greater abundance of AsV. However, AsIII (TF = 0.32) showed greater mobility from the roots to shoots than AsV (TF = 0.04), indicating a higher quantity of AsIII specific transporter assemblages in the plasmalemma of the endodermis or cytoplasmic reduction of AsV to AsIII in culms. Metal(loid)s, including As (90%), were predominantly in root tissues and very limited translocation to culm, indicating the species is a useful phytostabiliser. As and all other metal(loid)s in roots were correlated with sediment loads (p < 0.05, R2 = 0.10–0.52), indicating the species would be an accumulative bioindicator.

Evaluating the effectiveness of drones for quantifying invasive upside-down jellyfish (Cassiopea sp.) in Lake Macquarie, Australia.

Upside-down jellyfish (Cassiopea sp.) are mostly sedentary, benthic jellyfish that have invaded estuarine ecosystems around the world. Monitoring the spread of this invasive jellyfish must contend with high spatial and temporal variability in abundance of individuals, especially around their invasion front. Here, we evaluated the utility of drones to survey invasive Cassiopea in a coastal lake on the east coast of Australia. To assess the efficacy of a drone-based methodology, we compared the densities and counts of Cassiopea from drone observations to conventional boat-based observations and evaluated cost and time efficiency of these methods. We showed that there was no significant difference in Cassiopea density measured by drones compared to boat-based methods along the same transects. However, abundance estimates of Cassiopea derived from scaling-up transect densities were over-inflated by 319% for drones and 178% for boats, compared to drone-based counts of the whole site. Although conventional boat-based survey techniques were cost-efficient in the short-term, we recommend doing whole-of-site counts using drones. This is because it provides a time-saving and precise technique for long-term monitoring of the spatio-temporally dynamic invasion front of Cassiopea in coastal lakes and other sheltered marine habitats with relatively clear water.

The trophic basis of fish assemblages in temperate estuarine and coastal ecosystems

More than half of the fish biomass of coastal rocky reefs depends on zooplankton; however, the trophic basis of estuarine fish assemblages remains unknown. We quantified the trophic basis (i.e. basal energy sources) of fish community biomass inhabiting three habitat types (seagrass, natural reef and artificial reef) in two estuaries, compared with two coastal rocky reef sites. Fish assemblages were surveyed with Baited Remote Underwater Video (BRUVs) and the species abundance, richness and biomass of fish were classified into nine functional feeding groups (6 teleost and 3 elasmobranch). Comparable metrics for coastal fish assemblages were obtained from published surveys using BRUVs. Using the functional feeding group biomass and the group-specific diet composition, the breakdown of energy sources was calculated using a food web analysis. Estuarine reef habitats had different species and different functional feeding group composition than seagrass habitat. The majority of fish biomass in the seagrass habitat was supported by detritus (51% in Botany Bay) or macrophytes (58% in Lake Macquarie). In contrast, zooplankton supported most fish biomass (45–59%) at the coastal reef locations, and in reef habitat in one estuary (35–43%), but not the other estuary (33–34%). Trophic pathways which support fish assemblages, are key in identifying mitigation measures which can help conserve these populations with growing urbanisation of estuaries and coasts.

Selenium cycling in a marine dominated estuary: Lake Macquarie, NSW, Australia a case study

Environmental context Knowledge of the fate of selenium in estuaries receiving inputs from coal-fired power stations is essential as these environments are important nursery habitats for marine life and selenium has been shown to cause fish and bird mortality and sublethal effects including oedema, chromosomal aberrations and reproductive success. Understanding selenium cycling allows risk assessment to be undertaken and appropriate action to protect resident organisms. Abstract The fate of selenium (Se) inputs from coal-fired power station operations in a marine dominated estuary, Lake Macquarie NSW, is explored, as well as Se toxicity, including sublethal and population effects. Selenium is rapidly adsorbed to sediments, and food webs are based on benthic food sources. Selenium is remobilised from sediments by volatilisation and diffusional processes following bioturbation. It is then transferred into food chains via benthic microalgae, deposit feeders and filter-feeding organisms processing suspended sediments. Historically, Se has been found to accumulate in fish to levels above those considered safe for human consumption. After the remediation of a major ash dam in 1995, Se inputs to Lake Macquarie have declined, and the Se concentrations of sediments have also reduced partially due to the deposition of cleaner sediment but also due to the formation of volatile dimethyl selenide. Bioturbation of oxidised surface sediments also results in the release of inorganic Se. In response to decreases in sediment Se concentrations, molluscs and fish Se concentrations have also reduced below deleterious levels, with most fish now being safe for human consumption. Selenium cycling involves the transformation of inorganic species (Se0, SeII, SeIV, SeVI) in sediments and the water column to dimethylselenide and dimethyl diselenide by bacteria with the accumulation of organic Se species in plant detritus (selenomethionine) and animals (selenomethionine and selenocysteine). Dissolved Se concentrations in Lake Macquarie, except near ash dam inputs, have always been well below those that cause toxicity. There is evidence based on Se sediment-spiking studies, however, that Se is probably causing sublethal effects. When undertaking risk assessments of Se, careful consideration should be given to understanding the fate of Se inputs and remobilisation into food webs as not all systems act in accordance with published studies that generally have high Se concentrations in the water column and phytoplankton-based food webs.

Limited genetic structure detected in sugar gliders (

Arboreal gliders are vulnerable to habitat fragmentation and to barriers that extend their glide distance threshold. Habitat fragmentation through deforestation can cause population isolation and genetic drift in gliding mammals, which in turn can result in a loss of genetic diversity and population long-term persistence. This study utilised next generation sequencing technology to call 8784 genome-wide SNPs from 90 sugar gliders (Petaurus breviceps) sensu stricto. Samples were collected from 12 locations in the Lake Macquarie Local Government Area (New South Wales). The sugar gliders appeared to have high levels of gene flow and little genetic differentiation; however spatial least cost path analyses identified the Pacific Motorway as a potential barrier to their dispersal. This Motorway is still relatively new (&lt;40 years old), so man-made crossing structures should be erected as a management priority to mitigate any long-term effects of population isolation by assisting in the dispersal and gene flow of the species.

Metal(loid) uptake and partitioning within the saltmarsh halophyte, Juncus kraussii

An investigation was conducted over three estuaries in SE Australia with a gradient in metal(loid) contamination to assess metal(loid) (Cu, Zn, As, Se, Cd and Pb) accumulation and transport within the halophytic saltmarsh rush, Juncus kraussii. Sydney Olympic Park exhibited the most elevated metal(loid) contamination, followed by Hunter Wetlands and Lake Macquarie. J. kraussii exhibited a strong ability to restrict metal(loid) movement into the root system, with the exception of cadmium (BCFs < 1.0) and unrestricted flow from root to culm excepting Se, Cd (TFs < 1). Pb and Zn exhibited elevated translocation between roots and culms (TF 4.4 and 7.3, respectively). Despite barriers for uptake into the below-ground tissues, most metal(loid)s were accumulated to the roots with environmental dose (except for Cu and Cd) and linear relationships were present between the root and culm (for As and Se) and the sediment and culm (for As, Se, Cd, and Pb).

Solving the puzzle of mercury fate and emissions by coal-fired power plants: The potential of hydrodynamic-atmospheric modelling

There is currently a significant gap in knowledge about the emission and deposition of mercury (Hg) from coal-fired power plants in Australia. To fill this gap, we propose a novel method that combines several sources of information (stratigraphic data, hydrodynamic modelling and atmospheric modelling), to identify the sources and fates of Hg emitted from coal-fired power plants. The stratigraphic record from Lake Macquarie (Australia) shows that mercury deposition increased up to 7-times since the 1950s, which is when coal-fired power plants were commissioned in the catchment. The stratigraphy also shows a decrease in Hg deposition with power plant retrofits. Using results from multiple models (statistical modelling, hydrodynamic modelling, particle density modelling and atmospheric emissions modelling), we found that ash dams contribute little Hg to Lake Macquarie. Instead, most of the Hg contamination in the lake is a result of atmospheric emissions from the power plants, and these power plants are also depositing Hg in the urban areas to the west of the lake. Our results demonstrate that the multi-proxy approach demonstrated in the paper can be used to provide clues as to the source of Hg, so that appropriate mitigation strategies and regulatory frameworks can be implemented.

Accumulation and distribution of metal(loid)s in the halophytic saltmarsh shrub, Austral seablite, Suaeda australis in New South Wales, Australia

We examined the patterns of uptake and partitioning of metal(loid)s in Suaeda australis from three highly urbanised estuaries (Sydney Olympic Park, Hunter Wetlands and Lake Macquarie) in NSW, Australia. Of these, Sydney Olympic Park was found to be the most contaminated estuary in terms of combined sediment metal(loid) load, followed by Hunter Wetlands and lowest in Lake Macquarie (via PERMANOVA). Uptake in roots was greater for the essential metals Cu and Zn along with the non-essential metal Cd and the metalloid Se (root BCFs >1) and lower for Pb and As (root BCFs <1). Substantial barriers for translocation from roots to stems were identified for all metal(loid)s (stem TFs; 0.07–0.68). Conversely, unrestricted flow from stems to leaves was observed for all metal(loid)s at unity or higher (leaf TFs ≥ 1). Strong linear relationships between sediment and root for Zn and Pb were observed, indicating roots as a useful bioindicator.

Planning for social justice, anticipating sea level rise: the case of Lake Macquarie, Australia

ABSTRACT Climate change will affect communities in diverse and differentiated ways, so adaptation approaches must strive to address social justice in order to reduce inequality. This paper applies a social justice framework to examine planning for sea level rise in a densely populated coastal settlement in eastern Australia. The Lake Macquarie area is highly vulnerable to sea level rise with local adaptation planning already underway. An in-depth case study is presented that draws upon 19 interviews with key informants and householders and a structured document and media analysis from 12 newspapers. This qualitative data was analysed to identify: the range of understandings of what is just in planning for sea level rise; and key factors that influence perceptions of justice in planned retreat scenarios. The study concludes that there is a need for guiding principles in decision-making that explicitly address social justice in order to realise more equitable outcomes.

Insulated nest boxes provide thermal refuges for wildlife in urban bushland during summer heatwaves

Abstract In urban bushland, the installation of nest boxes is widely used to compensate for the loss of natural tree hollows. However, current nest box designs may not provide thermal refuges for wildlife during summer heatwaves, particularly if internal temperatures exceed the upper critical temperatures of wildlife. We investigated whether the addition of roofing insulation to nest boxes deployed for sugar gliders (Petaurus breviceps) and squirrel gliders (Petaurus norfolcensis) in urban bushland would reduce internal nest box temperatures during summer heatwaves. We measured temperatures of 44 insulated and 47 uninsulated nest boxes during one of the hottest summers on record (2018–2019) in the Lake Macquarie region of NSW, Australia, a period during which several prolonged heatwaves occurred. Over the 90-day study, maximum temperatures were, on average, 3.1°C lower in insulated boxes than in uninsulated boxes. The addition of insulation significantly lowered nest box temperatures regardless of aspect (north or south facing) or day of measurement. Temperatures exceeded the upper critical temperature (35.1°C) of gliders more frequently in uninsulated nest boxes (28% of days) than in insulated nest boxes (8% days). Although the addition of insulation to nest boxes lowered their internal temperatures, during heatwaves spanning 23 days, nest box temperatures exceeded the upper critical temperatures of gliders on 58% and 23% of days in uninsulated and insulated nest boxes respectively. These findings underscore the importance of retaining natural hollows in urban bushland to provide thermally suitable refuges for wildlife during extreme heat events.

Assessment of the Effects of Sediment-Associated Metals and Metalloids on Mangrove Macroinvertebrate Assemblages

Although much previous research effort has examined the impacts of metal contamination on macrobenthic assemblages in subtidal sediments, little attention has been directed at macroinvertebrate responses in intertidal mangrove habitats. Thus, in order to assess the unique responses of mangrove macroinvertebrate assemblages to sediment metal(loid) contamination, total, normalised and bioavailable metal(loid)s (Mn, Pb, Cr, Cd, As, Se, Co, Ni, Zn and Cu) were assessed within and between four mangrove locations in Lake Macquarie, NSW, Australia, and compared to resident macroinvertebrate assemblages over two sampling occasions. Mangrove biomass and physicochemical properties of sediment are known to influence macroinvertebrate assemblages, and as such, were also assessed to account for any potential confounding effect on macroinvertebrate assemblage composition. Significant differences in total and bioavailable metal(loid) contamination were found between and within locations and were consistent over time. Sediments at contaminated locations presented a high risk to biota with bioavailable concentrations of Pb, Cd, Zn found to exceed sediment quality guidelines and concentrations of Se capable of adverse impacts to biota. Macroinvertebrate assemblage composition varied with metal(loid) contamination loads present at study locations. Metal(loid) contamination was significantly correlated with macroinvertebrate assemblages over two sampling periods. Further analysis revealed that 71% of macroinvertebrate assemblage composition could best be explained by a combination of five variables namely, bioavailable Mn, Zn, and Se, number of mangrove seedlings and mean mangrove biomass. Rather than tolerant polychaetes dominating metal(loid)-contaminated sediments (as is found generally in subtidal sediments), polychaetes in intertidal mangroves appeared to be relatively sensitive to metal(loid) stress. Further, decapod crustaceans in the family, Varunidae, and gastropod molluscs, in the family, Amphibolidae, were found to be metal-sensitive taxa and may be employed in future studies as indicator taxa of sediment metal(loid)-related impacts in south-eastern Australian mangrove forests.