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Estuaries are crucial feeding, nursery and resting sites for fish but can also be subject to the impacts of severe flooding. The environmental features of estuaries can mediate how they respond to these impacts. For example, the size, configuration, and context of estuarine habitats across seascapes affects the value of patches for fish, and so fish assemblages at sites with a greater habitat extent or closer to the mouth of an estuary may rebound more quickly from flooding. We investigated how a once in 100-year flood event affected fish assemblages at approximately 600 sites across 13 estuaries and six estuarine habitats (bare sediments, log snags, mangrove forests, rocky structures, saltmarsh and seagrass meadows) in southeast Queensland, Australia, and determined whether flood impacts were mediated by the position of sites within the broader estuarine seascape. Sites were surveyed annually in 2020/2021 (pre-flood) and 2022 (6 months post-flood) using underwater videography. Flooding modified the structure of the fish community and reduced the abundance of fish targeted by local fisheries in all six habitats. Crucially, flood effects on fish were greater at sites near more expansive urbanisation in some ecosystems, but lower at sites nearer to the estuary mouth. Maximising the extent of natural habitats across estuaries can mediate the effects of floods and should be priorities for restoration and management plans seeking to maintain biodiversity and fisheries productivity in the face of increasing climate-related disturbances. [ABSTRACT FROM AUTHOR]

Gut bacterial communities play a vital role in a host's digestion and fermentation of complex carbohydrates, absorption of nutrients, and energy harvest/storage. Dugongs are obligate seagrass grazers with an expanded hindgut and associated microbiome. Here, we characterised and compared the faecal bacterial communities of dugongs from genetically distinct populations along the east coast of Australia, between subtropical Moreton Bay and tropical Cleveland Bay. Amplicon sequencing of fresh dugong faecal samples (n=47) revealed Firmicutes (62%) dominating the faecal bacterial communities across all populations. Several bacterial genera (Bacteroides, Clostridium sensu stricto 1, Blautia and Polaribacter) were detected in samples from all locations, suggesting their importance in seagrass digestion. Principal coordinate analysis showed the three southern-most dugong populations having different faecal bacterial community compositions from northern populations. The relative abundances of the genera Clostridium sensu stricto 13 and dgA-11 gut group were higher, but Bacteroides was lower, in the southern dugong populations, compared to the northern populations, suggesting potential adaptive changes associated with location. This study contributes to our knowledge of the faecal bacterial communities of dugongs inhabiting Australian coastal waters. Future studies of diet selection in relation to seagrass availability throughout the dugong's range will help to advance our understanding of the roles that seagrass species may play in affecting the dugong's faecal bacterial community composition. [ABSTRACT FROM AUTHOR]

Background: Seagrass, a vital primary producer habitat, is crucial for maintaining high biodiversity and offers numerous ecosystem services globally. The increasing severity and frequency of marine heatwaves, exacerbated by climate change, pose significant risks to seagrass meadows. Aims: This study acknowledges the uncertainty and variability of marine heatwave scenarios and aims to aid managers and policymakers in understanding simulated responses of seagrass to different durations, frequencies and recurrence gaps of marine heatwaves. Materials and Methods: Using expert knowledge and observed data, we refined a global Dynamic Bayesian Network (DBN) model for a specific case study on Halophila ovalis in Leschenault Estuary, Australia. The model evaluates the potential impact of marine heatwaves on seagrass resilience, examining stress resistance, recovery and extinction risk. Results: Simulations of different marine heatwave scenarios reveal significant impacts on seagrass ecosystems. Scenarios ranged from 30‐ to 90‐day heatwaves, with longer durations causing more significant biomass decline, reduced resistance, higher extinction risk and prolonged recovery. For instance, recovery time may increase from 18 to 26 months with four 60‐day and from 24 to 47 months with four 90‐day marine heatwave events. Increasing the frequency of marine heatwaves from one to four annual events, with no gaps between occurrences, could raise extinction risk from 11% to 55% for 60‐day events and from 17% to 83% for 90‐day events. However, introducing gaps between heatwaves enhanced resilience, with spaced events showing lower extinction risks and quicker recovery than consecutive yearly events. Discussion: The study demonstrates the DBN model's utility in simulating the impact of marine heatwaves on seagrass, providing tools for risk‐informed assessment of management and restoration efforts. While these simulations align with existing research on temperature impacts on seagrass, they are not empirical. Conclusion: Further research is necessary to expand our understanding of climate change effects on seagrass ecosystems, guide policy and develop strategies to strengthen marine ecosystem resilience. [ABSTRACT FROM AUTHOR]

Stocking 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. [ABSTRACT FROM AUTHOR]

Seagrass habitats are recognised as providing essential ecosystem services and being indicators of estuarine health, and are under increasing threat globally. This study examined the spatial and temporal variability of four dominant seagrass genera (Posidonia, Zostera, Halophila and Ruppia) among five geomorphic estuary types and four levels of estuarine maturity in New South Wales (NSW), Australia, over a 40-year period. While there was a decline in total seagrass area across NSW over the last 40 years, this was mostly attributed to Ruppia, the genus with the greatest temporal variability. The composition of seagrasses differed among estuary types and with the maturity of Barrier estuaries. Posidonia was found to be the least temporally variable genus over the last 40 years. The greatest overall annual rate of decline was 1.85% year−1 for Ruppia which is considerably less than the global estimated rate of 5% year−1 over the same time period. Average annual rates of decline were greater over the last 18 years than the last 40 years, but only for the most transient genera and only in some estuary types. Recent declines in Posidonia were greater than those over the last 40 years in two of the most heavily urbanised estuaries. The temporal variability of Zostera differed significantly among estuary types and decreased with increasing water depth across all estuaries. No relationships were found between catchment disturbances, measured as land use or population density, and seagrass change or temporal variability at the estuary scale. Our results highlight the importance of distinguishing among seagrass genera when interpreting changes over time and considering factors such as estuary type, which is effectively a surrogate for environmental conditions. [ABSTRACT FROM AUTHOR]

Biodiversity offsetting is increasingly used to mitigate biodiversity impacts from development, but the practice of offsetting rarely considers how to also mitigate losses of ecosystem services. Offset rules, such as how near an offset must be to an impact site, may help ensure biodiversity offsets also counterbalance losses of ecosystem services but this has not yet well understood.We explored how different rules for siting coastal offsets could change net impacts to a provisioning ecosystem service: fishery resources in Queensland, Australia. A spatially explicit model incorporating supply, flow and demand of fishery resources was developed to simulate contributions of offset sites to commercial fisheries in Queensland, Australia. We simulated offsets for losses due to 63 real projects that damaged mangroves and 14 projects damaging seagrasses.We found that the percentage of species suffering net negative outcomes for the whole commercial fishery increased from about 68% when offsets were located close to impact sites to >85% when there were no restrictions on offset location. All fisheries for seagrass offsets suffered net economic losses under both scenarios, but these were worse when offsets were not required to be near to impact sites.Offsetting outcomes varied substantially across species. Species with shorter maximum dispersal distance and higher dispersal decay parameters suffered greater net losses.Synthesis and applications. Our model quantified impacts of fishery habitat depletion and offsets on fishery resources and the approach can be applied to assess impacts of losses of fishery habitats globally. The findings suggest that to minimize losses of fishery resources caused by habitat depletion, offset policy should generally locate offset sites at the locations available for restoration that are nearest to impact sites, unless specific information about the relative contributions of sites to impacted fisheries is available to guide offset location. [ABSTRACT FROM AUTHOR]

Angiosperms have co‐evolved with animals over thousands of years leading to an array of mutualistic relationships. Passage of plant seeds through animal intestines leads to an important mutualism providing the animal with food and the plant with seed dispersal and enhanced germination. This phenomenon is well studied in terrestrial angiosperms, but there is less research in aquatic environments. We studied the effect of gut passage in marine mega‐herbivores (green sea turtles and dugongs) on seed germination for a common Australian seagrass, Zostera muelleri. We collected fecal samples likely to contain seeds, as well as seagrass seeds from plants at two coastal seagrass meadows in the central Great Barrier Reef World Heritage Area, Australia. Seeds collected from feces and plants were subjected to germination trials across different temperature treatments: low (19°C), medium (26°C), and high (32°C). We found excreted seeds had a significantly greater germination probability (two to four times greater) and germinated significantly faster (18–61% faster) than seeds from the plant. Excreted seeds which had not germinated at the end of the experiment were significantly less likely to be viable compared with seeds taken from the plant. Seeds released from the plant have a slow germination and low germination probability compared with excreted seeds, but retain a high percentage of seed viability. Our study is the first record of marine mega‐herbivores enhancing germination of Z. muelleri seeds. By transporting seeds to new locations and enhancing germination, these animals are important in seagrass resilience and connectivity among metapopulations. [ABSTRACT FROM AUTHOR]

Extreme climatic events (ECEs) and predator removal represent some of the most widespread stressors to ecosystems. Though species interactions can alter ecological effects of climate change (and vice versa), it is less understood whether, when and how predator removal can interact with ECEs to exacerbate their effects. Understanding the circumstances under which such interactions might occur is critical because predator loss is widespread and ECEs can generate rapid phase shifts in ecosystems which can ultimately lead to tropicalization.Our goal was to determine whether loss of predation risk may be an important mechanism governing ecosystem responses to extreme events, and whether the effects of such events, such as tropicalization, can occur even when species range shifts do not. Specifically, our goal was to experimentally simulate the loss of an apex predator, the tiger shark Galeocerdo cuvier effects on a recently damaged seagrass ecosystem of Shark Bay, Australia by applying documented changes to risk‐sensitive grazing of dugong Dugong dugon herbivores.Using a 16‐month‐field experiment established in recently disturbed seagrass meadows, we used previous estimates of risk‐sensitive dugong foraging behaviour to simulate altered risk‐sensitive foraging densities and strategies of dugongs consistent with apex predator loss, and tracked seagrass responses to the simulated grazing.Grazing treatments targeted and removed tropical seagrasses, which declined. However, like in other mixed‐bed habitats where dugongs forage, treatments also incidentally accelerated temperate seagrass losses, revealing that herbivore behavioural changes in response to predator loss can exacerbate ECE and promote tropicalization, even without range expansions or introductions of novel species.Our results suggest that changes to herbivore behaviours triggered by loss of predation risk can undermine ecological resilience to ECEs, particularly where long‐lived herbivores are abundant. By implication, ongoing losses of apex predators may combine with increasingly frequent ECEs to amplify climate change impacts across diverse ecosystems and large spatial scales. [ABSTRACT FROM AUTHOR]

Ecological restoration is increasingly being upscaled to larger spatial scales of tens to hundreds of kilometers. Yet the complex logistics and high costs of ecological restoration mean that actions must be placed strategically at local scales of tens of meters to maximize ecological benefits and reduce socioeconomic costs. Despite the purported use of systematic planning tools for allocating restoration effort, the uptake and implementation of data‐driven restoration planning and ecological goal setting remains poor in many restoration programs. Here we demonstrate how the sequential workflows of systematic conservation planning can be translated to restoration at two spatial scales to enhance estuarine fisheries in eastern Australia. We select estuaries where restoration is feasible and recommended based on quantitative regional ecological goals (i.e. regional‐scale prioritization), and then identify potential restoration sites at smaller spatial scales within estuaries based on the principles of spatial ecology to ensure that the success and benefits of restoration are maximized (i.e. local‐scale prioritization). At the regional scale, we identified four levels of restoration priorities (very high, high, intermediate, and low) using quantitative ecological goals and the current ecological understanding of each system. At the local scale, we used spatially explicit Bayesian belief networks to identify sites that maximize restoration outcomes based on the environmental niche of habitat‐forming species and the spatial configuration of habitats that maximizes their use by fish. We show that using systematic frameworks can become an essential tool to optimize restoration investments at multiple scales as efforts upscale globally. [ABSTRACT FROM AUTHOR]

The seagrass Halophila ovalis rapidly colonizes marine sediments from seed across a range of depth, light, and temperature conditions, making it ideal for restoration projects. Yet, presently, it is not a targeted restoration species as the biology of seed dormancy and germination is poorly understood. This study addresses that knowledge gap by experimenting with temperature and light pre-treatments with the aim to determine optimal conditions for high rates of seed germination. H. ovalis seeds were pre-treated ex situ by applying nine combinations of temperature and monochromatic light. Two thirds of the pre-treated seeds were placed at separate field sites in conditions suboptimal for natural germination while one third remained in ex situ culture under suboptimal germination conditions (17 °C). Seed viability was monitored to determine if storage conditions impacted viability. X-ray analysis revealed a general decline in viability with time in storage. To analyze the effectiveness of pre-treatments, we compared the results of ex situ and in situ germination. Pre-treating seeds with red light (673 nm) and a stepwise temperature increase (15–20–25 °C) yielded the highest germination success across field and laboratory culture conditions. This indicates that we can use temperature and monochromatic light pre-treatments to break seed dormancy in the laboratory and induce "on-demand" germination of seeds after delivery to field sites potentially leading to more efficient and successful restoration practices with this species. Similarly, the conditions required for breaking dormancy and germination in H. ovalis (red spectrum light and a stepwise temperature increase) represent conditions associated with spring river freshwater runoff and warming of estuaries and coastal seas in temperate Australia. [ABSTRACT FROM AUTHOR]

Context: Whilst the composition and arrangement of habitats within landscape mosaics are known to be important determinants of biodiversity patterns, the influence of seascape patterning and connectivity on temperate reef fish assemblages remains largely unknown. Objectives: We examined how habitat patterns at multiple spatial scales (100–1000 m) explained the abundance and diversity of temperate reef fish in a reef-seagrass dominated seascape. Methods: Fish assemblages were surveyed using remote underwater videos deployed on 22 reefs in Jervis Bay, NSW, Australia. Using full-subset GAMMs, we investigated if habitat area, edge, structural connectivity and a metric for habitat diversity (Shannon's diversity index) of reef and seagrass can predict variations in a temperate reef fish assemblage. Results: A key finding of the study was that temperate reefs close (< 55 m) to large (> 6.25 ha) seagrass meadows contained greater abundance and diversity of fish. A consistent negative correlation was also found between reef area (> 0.01 ha) and the fish assemblage. The influence of seascape metrics on the abundance of fishes varied with functional traits (trophic groups, mobility and habitat associations). Fish-seascape relationships occurred at a range of spatial scales with no single scale being solely important for structuring the fish assemblage. Conclusions: We demonstrate that it is important not to view reef habitats in isolation, rather consider a reefs context to adjacent seagrass when predicting the distribution of temperate reef fish. This finding improves current understanding of the multi-scale factors structuring temperate reef fish assemblages and highlights the importance of reef-seagrass connectivty for the management of temperate marine ecosystems. [ABSTRACT FROM AUTHOR]

Animals are central to numerous ecological processes that shape the structure and function of ecosystems. It follows that species that are strongly linked to specific functions can represent these functions spatially and hence be useful in conservation planning. Here we test this notion of 'functional species surrogacy' for the conservation of seagrass meadows that have been impacted by stressors. We measured algal herbivory and herbivorous fish assemblages across a range of seagrass meadows in the Moreton Bay Marine Park, Queensland, Australia. We determined the suitability of herbivorous fish to act as a surrogate for the function of algal herbivory and modelled the abundance of this surrogate, and thus herbivory, in seagrass meadows to compare the spatial distribution of this function within existing reserves. We used underwater video systems to determine the abundance of all herbivorous fish species in seagrass meadows. The abundance of the dusky rabbitfish (Siganus fuscescens) was the best predictor of algal herbivory in seagrass meadows, supporting the suitability of this species as a functional surrogate. The distribution of dusky rabbitfish, and therefore the ecological function of herbivory, was not well represented in the Moreton Bay Marine Park protected areas. Only 7% of the equivalent area of seagrass meadows protected in marine reserves were found to have high abundances of dusky rabbitfish. We demonstrate that the abundance of functionally important herbivores can be suitable as a surrogate for herbivory in seagrass conservation. Our findings show that data on the spatial distribution of ecological functions can alter priorities for reserve design, and we suggest that our functional approach to species surrogacy is likely to improve conservation performance in seagrass ecosystems. [ABSTRACT FROM AUTHOR]

Photosynthesis in the seagrass Zostera muelleri remains poorly understood. We investigated the effect of reduced irradiance on the incorporation of 13C, gene expression of photosynthetic, photorespiratory and intermediates recycling genes as well as the enzymatic content and activity of Rubisco and PEPC within Z. muelleri. Following 48 h of reduced irradiance, we found that i) there was a ∼7 fold reduction in 13C incorporation in above ground tissue, ii) a significant down regulation of photosynthetic, photorespiratory and intermediates recycling genes and iii) no significant difference in enzyme activity and content. We propose that Z. muelleri is able to alter its physiology in order to reduce the amount of C lost through photorespiration to compensate for the reduced carbon assimilation as a result of reduced irradiance. In addition, the first estimated rate constant (K cat) and maximum rates of carboxylation (V cmax) of Rubisco is reported for the first time for Z. muelleri. • Photosynthetic carbon fixation is reduced in Zostera muelleri when exposed to low irradiance. • Photosynthesis, photorespiration and intermediates recycling genes are down regulated. • No significant changes in Rubisco content or phosphoenol pyruvate carboxylase activity. [ABSTRACT FROM AUTHOR]

The seascape context of coastal ecosystems plays a pivotal role in shaping patterns in fish recruitment, abundance, and diversity. It might also be a principal determinant in structuring the recruitment of fish assemblages to restored habitats, but the trajectories of these relationships require further testing. In this study, we surveyed fish assemblages from 14 restored oyster reefs and 14 control sites in the Noosa River, Queensland, Australia, that differed in the presence or absence of seagrass within 500 m, over four periods using baited cameras. Fish assemblages at oyster reefs differed from those at control sites, with higher species richness (1.4 times) and more individuals of taxa that are harvested by fishers (1.8 times). The presence or absence of seagrass nearby affected the abundance of a key harvestable fish species (yellowfin bream Acanthopagrus australis) on oyster reefs, but not the overall composition of fish assemblages, species richness, or the total abundance of harvestable fishes overall. These findings highlight the importance of considering species-specific patterns in seascape utilization when selecting restoration sites and setting restoration goals, and suggest that the effects of restoration on fish assemblages might be optimized by focusing efforts in prime positions in coastal seascapes. [ABSTRACT FROM AUTHOR]

Abstract: Aim: Long‐distance dispersal (LDD) events occur rarely but play a fundamental role in shaping species biogeography. Lying at the heart of island biogeography theory, LDD relies on unusual events to facilitate colonization of new habitats and range expansion. Despite the importance of LDD, it is inherently difficult to quantify due to the rarity of such events. We estimate the probability of LDD of the seagrass Heterozostera nigricaulis, a common Australian species, across the Pacific Ocean to colonize South America. Location: Coastal Chile, Australia and the Pacific Ocean. Methods: Genetic analyses of H. nigricaulis collected from Chile and Australia were used to assess the relationship between the populations and levels of clonality. Ocean surface current models were used to predict the probability of propagules dispersing from south‐east Australia to central Chile and shipping data used to determine the likelihood of anthropogenic dispersal. Results: Our study infers that the seagrass H. nigricaulis dispersed from Australia across the entire width of the Pacific (c. 14,000 km) to colonize South America on two occasions. Genetic analyses reveal that these events led to two large isolated clones, one of which covers a combined area of 3.47 km2. Oceanographic models estimate the arrival probability of a dispersal propagule within 3 years to be at most 0.00264%. Early shipping provides a potential alternative dispersal vector, yet few ships sailed from SE Australia to Chile prior to the first recording of H. nigricaulis and the lack of more recent and ongoing introductions demonstrate the rarity of such dispersal. Main conclusions: These findings demonstrate LDD does occur over extreme distances despite very low probabilities. The large number of propagules (100s of millions) produced over 100s of years suggests that the arrival of propagules in Chile was inevitable and confirms the importance of LDD for species distributions and community ecology. [ABSTRACT FROM AUTHOR]

A crucial goal of ecosystem-based management is to maintain the delivery of ecosystem services (ESS) over time. This requires ESS to be assessed repeatedly over time, a task that becomes extremely challenging in data-poor coastal areas, where the lack of data and resources sums up with the intrinsic difficulties of assessing marine and coastal ESS. This implies the need to develop simple ESS assessment methods and to optimize the monitoring effort required to implement them. The aim of this work is to identify which are the key monitoring priorities for ESS mapping in data-poor coastal areas, in the perspective of ecosystem-based management implementation. In order to do so, the ESS provided by Posidonia oceanica meadows in the northern African Mediterranean coastal area have been chosen as a case study, and assessed by mapping the service providing, benefiting and connecting areas. Different input data and methods have been tested to explore how the mapping approach can be kept as simple as possible to ensure a broad applicability, and which are the crucial data required, in order to optimize the monitoring effort. The spatial distribution of the habitat providing the ESS resulted to be the data to which the mapping outcomes are more sensitive, and should be thus considered a key monitoring priority. The other input data can be kept as simple as (1) an expert-driven estimate of the service connecting area, to be understood as an ecologically meaningful range of influence of the focal habitat, and (2) globally available datasets for mapping the service benefiting areas. Overall, this results in an aggregated mapping of the multiple ESS provided by a marine habitat, which, according to our results, seems to be an advisable strategy for a first ESS assessment suitable for application in a data-poor context. [ABSTRACT FROM AUTHOR]

Summary: Globally, coastal habitat restoration is growing in recognition as a viable management tool to repair and reinstate valuable coastal habitats and species, such as mangrove and macroalgae forests, salt marshes, seagrass meadows, shellfish and coral reefs (Aronson & Alexander ( ), Restoration Ecology, 293; Anthony et al. ( ) Nature Ecology and Evolution, 1420; TNC ( ) Caribbean: A revolution to save coral reefs in the Caribbean and beyond). In Australia, there is increasing interest and investment in coastal restoration and habitat conservation, particularly with respect to growing national concerns around habitat loss, coastal inundation and erosion, loss of fisheries and climate change (Maggini et al. ( ) Protecting and restoring habitat to help Australia's threatened species adapt to climate change; GBRMPA ( ) Reef summit sets new course of action for the Great Barrier Reef). This has led to new community of practices being formed for shellfish reef restoration (Shellfish Reef Restoration Network shellfishrestoration.org.au), seagrass restoration (Seagrass Restoration Network seagrassrestoration.net), and saltmarsh and mangrove (Saltmarsh and Mangrove Network, amsn.net.au) conservation. However, despite this interest, there has been no national coordination, network or society with coastal restoration as a primary focus. The inaugural Australian Coastal Restoration Symposium brought together 60 Australian restoration practitioners, researchers and managers at James Cook University, Townsville for three days from the 31st of August 2017. The symposium goals were to enhance collaboration and national coordination amongst coastal restoration projects and practitioners, as well as to connect researchers and practitioners working in the restoration space with one another. Three international keynote speakers shared their experiences and advice. Delegates were enthusiastic about continuing to meet at future symposiu, meetings and workshops, and noted the value of being able to connect, share project experiences and learnings, and collaborate. The Australian Coastal Restoration Network has been formed with the goal of meeting annually to continue to share knowledge and improve collaboration. View a video about the symposium by following this link – https://www.youtube.com/watch?v=lukSpo3mM-4 [ABSTRACT FROM AUTHOR]

Dredging can have significant impacts on benthic marine organisms through mechanisms such as sedimentation and reduction in light availability as a result of increased suspension of sediments. Phototrophic marine organisms and those with limited mobility are particularly at risk from the effects of dredging. The potential impacts of dredging on benthic species depend on biological processes including feeding mechanism, mobility, life history characteristics (LHCs), stage of development and environmental conditions. Environmental windows (EWs) are a management technique in which dredging activities are permitted during specific periods throughout the year; avoiding periods of increased vulnerability for particular organisms in specific locations. In this review we identify these critical ecological processes for temperate and tropical marine benthic organisms; and examine if EWs could be used to mitigate dredging impacts using Western Australia (WA) as a case study. We examined LHCs for a range of marine taxa and identified, where possible, their vulnerability to dredging. Large gaps in knowledge exist for the timing of LHCs for major species of marine invertebrates, seagrasses and macroalgae, increasing uncertainty around their vulnerability to an increase in suspended sediments or light attenuation. We conclude that there is currently insufficient scientific basis to justify the adoption of generic EWs for dredging operations in WA for any group of organisms other than corals and possibly for temperate seagrasses. This is due to; 1) the temporal and spatial variation in the timing of known critical life history stages of different species; and 2) our current level of knowledge and understanding of the critical life history stages and characteristics for most taxa and for most areas being largely inadequate to justify any meaningful EW selection. As such, we suggest that EWs are only considered on a case-by-case basis to protect ecologically or economically important species for which sufficient location-specific information is available, with consideration of probable exposures associated with a given mode of dredging. [ABSTRACT FROM AUTHOR]

The coastal seagrass meadows in the Townsville region of the Great Barrier Reef are crucial seagrass foraging habitat for endangered dugong populations. Deteriorating coastal water quality and in situ light levels reduce the extent of these meadows, particularly in years with significant terrestrial runoff from the nearby Burdekin River catchment. However, uncertainty surrounds the impact of variable seagrass abundance on dugong carrying capacity. Here, I demonstrate that a power-law relationship with exponent value of − 1 (R 2 ~ 0.87) links mortality data with predicted changes in annual above ground seagrass biomass. This relationship indicates that the dugong carrying capacity of the region is tightly coupled to the biomass of seagrass available for metabolism. Thus, mortality rates increase precipitously following large flood events with a response lag of < 12-months. The management implications of this result are discussed in terms of climate scenarios that indicate an increased future likelihood of extreme flood events. [ABSTRACT FROM AUTHOR]

Aim: The movement of propagules among plant populations affects their ability to replenish and recover after a disturbance. Quantitative data on recovery strategies, including the effectiveness of population connectivity, are often lacking at broad spatial and temporal scales. We use numerical modelling to predict seagrass propagule dispersal and settlement to provide an approach for circumstances where direct, or even indirect, measures of population dynamics are difficult to establish. Location: Great Barrier Reef, Australia. Methods: We used the finite-element Second-generation Louvain-la-Neuve Iceocean Model (SLIM) to resolve the hydrodynamics of the central Great Barrier Reef and to simulate the dispersal of seagrass. We predicted dispersal and settlement patterns by releasing 10.6 million passive particles representing seagrass propagules at known sites of seagrass presence. We considered two fractions when modelling seagrass dispersal: floating and suspended propagules. Both fractions were modelled using 34 simulations run for a maximum of 8 weeks during the peak seagrass reproductive period, capturing variability in winds, tides and currents. Results: The 'virtual' seagrass propagules moved on average between 30 and 60 km, but distances of over 900 km also occurred. Most particle movement was to the north-west. The season (month) of release and source locations of the particles correlated with their dispersal distance, particularly for particles released offshore, with the complex coastal topography impeding movements close to the coast. The replenishment and recovery potential of the northernmost meadows was influenced by southern meadows. Protected north-facing bays were less likely to receive particles. Main conclusions: Our approach advances the conservation and management of marine biodiversity by predicting a key component of ecosystem resilience at a spatial scale that informs marine planning. We show a complex interaction among time, wind, water movement and topography that can guide a management response to improving replenishment and recovery after disturbance events. [ABSTRACT FROM AUTHOR]

This study used stable-isotope analysis to define the nearshore regional residency and movements of the small-bodied Australian sharpnose shark Rhizoprionodon taylori. Plasma and muscle δ13C and δ15N of R. taylori were collected from across five embayments and compared with values of seagrass and plankton from each bay. Linear distances between adjacent bays ranged from 30 to 150 km. There was a positive geographic correlation between R. taylori tissue and environmental δ13C values. Populations with the highest tissue δ15N were collected from bays that had the highest environmental δ15N values. These results suggest that R. taylori did not forage more than 100 km away from their capture location within 6 months to 1 year. The successful application of isotope analysis to define R. taylori movement demonstrates that this technique may be used in addition to traditional methods to study the movement of sharks, even within similar habitats across regionally small spatial scales (<100 km). [ABSTRACT FROM AUTHOR]

Ashmore Reef, located approximately 630 km north of Broome, Australia, is notable for its contribution to overall seagrass cover in the Timor Province bioregion, providing valuable ecosystem services including critical habitat for feeding and breeding green turtles (Chelonia mydas) and a small geographically isolated population of dugong (Dugong dugon). Yet, seagrass surveys at Ashmore Reef have not been completed since 2005. Seagrass was surveyed in 2019, with only two (Thalassia hemprichii and Halophila ovalis) of the five previously recorded species observed. Monitoring survey sites were established to determine density, biomass and productivity of the dominant species, T. hemprichii. Overall mean total biomass was 116.9 DW m−2 with an above- and below-ground biomass ratio of 1:2.5. Mean shoot density was 407 shoots m−2 (range 88.9–600 shoots m−2) with a mean canopy height of 42.8 mm (range 10–80 mm), and average blade length of 37.6 mm (± 1.1 SE) and blade width of 4.5 mm (± 0.2). Mean leaf growth was calculated as 2.2–2.4 mm day−1 and shoot growth 3.2–3.5 mm day−1. Canopy height increased by 5.3–5.7 % day−1 with a turnover rate of 17.5–21.3 days. Mean biomass of emergent leaves was 8 g DW m−2 with a grazing rate of 0.4 g DW m−2 day −1 or 123 kg DW ha−1 month−1. This study suggests that T. hemprichii at Ashmore Reef is productive and may support high turtle grazing rates. • This was the first monitoring study conducted at Ashmore Reef since 2005. • Only two seagrass species were observed (Thalassia hemprichii and Halophila ovalis). • Although considered relatively stunted, T. hemprichii appeared to be productive. • Growth and biomass measurements suggested exposure to high environmental stress. • Grazing rates suggested ability to support high feeding levels by green turtles. [ABSTRACT FROM AUTHOR]

Highlights: [•] Major storms and climate events resulted in large scale losses of tropical seagrasses. [•] Recovery varied between meadows and species with many failing to re-establish. [•] Deep water seagrass species re-colonised but shallow species failed to recover. [•] The variable presence of seed banks was the main cause of differences in seagrass recovery. [•] Meadows relying on clonal growth were highly vulnerable to large scale impacts. [Copyright &y& Elsevier]

Recognising patterns of genetic diversity and connectivity is integral to understanding the mechanisms behind population declines and formulating management plans for the conservation of threatened or endangered species. This is particularly important for clonal organisms such as seagrasses, which are experiencing rapid global decline. This study quantifies genetic diversity within 12 naturally fragmented Posidonia australis meadows on the east coast of Australia, using a set of eight microsatellite DNA markers. Genetic diversity increased with latitude, moving away from the range-edge, and was significantly lower in six mid-range endangered meadows and the two northernmost meadows. These meadows also showed evidence of shared multilocus genotypes despite significant geographic separation. The four southernmost meadows were genetically differentiated from all other meadows further north, and all multilocus genotypes identified were unique to their sample locations. We conclude that patterns of low diversity in the endangered and northern meadows are likely due to a population bottleneck caused by a range-edge effect. A common ancestral source meadow existing prior to historical sea level changes may explain the sharing of multilocus genotypes, as contemporary gene flow between these geographically isolated meadows is unlikely. Our findings have important implications for conservation, highlighting the endangered and range-edge populations as those potentially most at risk of extinction should environmental conditions change. These results can be utilised for the location of suitable donor populations for transplanting purposes as a means of mitigating further declines. [ABSTRACT FROM AUTHOR]

Seagrass habitats provide critical ecosystem services, yet there is ongoing concern over mounting pressures and continuing degradation. Defining a desired state for these habitats is a key step in implementing appropriate management but is often difficult given the challenges of available data and an evaluation of where to set benchmarks. We use more than 20 years of historical seagrass biomass data (1995–2018) for the diverse seagrass communities of Australia's Great Barrier Reef World Heritage Area (GBRWHA) to develop desired state benchmarks. Desired state for seagrass biomass was estimated for 25 of 36 previously defined seagrass communities with the remainder having insufficient data. Desired state varied by more than one order of magnitude between community types and was influenced by the mix of species in the communities and the range of environmental conditions. We identify a historical, decadal-scale cycle of decline with recovery to desired state in coastal intertidal communities. In contrast a number of the estuary and coastal subtidal communities have not recovered to desired state biomass. Understanding a historical context is critically important for setting benchmarks and making informed management decisions on the present state of seagrass in the GBRWHA. The approach we have developed is scalable for monitoring, management and assessment of pressures for other management areas and for other jurisdictions. Our results guide conservation planning through prioritization of the at-risk seagrass communities that are continuing to fall below their desired state. • Changes in biomass of seagrass communities were examined. • We estimate a desired state of biomass for each seagrass community. • We identify decadal-scale trends of loss and recovery for some communities. • In recent years desired state has not been attained for many communities. • Our approach enables the prioritization of management activities. [ABSTRACT FROM AUTHOR]

Interest in oyster reef conservation and restoration is growing globally, but particularly in Australia, it is unclear the extent to which oyster reefs complement (versus replicate) habitat provisioning by other structured habitats in the seascape. Remote underwater video surveys of two east Australian estuaries revealed that at high tide, oyster reefs not only supported distinct fish communities to bare sediments but also to adjacent seagrass beds and mangrove forests. Fish observations in oyster reefs were close to double that of mangroves and seagrass, with species richness, abundance, feeding and wandering behaviours similar. Several species of blenny and goby were unique to oyster reefs and oyster-containing mangroves, whilst recreationally fished species such as bream and mullet were more abundant on oyster reefs than in other habitats. Resolving the association between oyster reefs and fish species within the broader seascape will assist in developing restoration and management strategies that maximise fisheries benefit. • The role of intertidal remnant oyster reefs as fish habitat was explored. • Oyster reefs provided habitat to a unique fish community within the seascape. • Fish observations were higher in oyster reefs, than in seagrass, mangroves and bare. • Fish sp. richness was higher in oyster reefs, than in seagrass, mangroves and bare. • Oyster reefs were utilised as refuge and foraging grounds by fish. [ABSTRACT FROM AUTHOR]

Abstract: Seagrass provides many ecosystem services that are of considerable value to humans, including the provision of nursery habitat for commercial fish stock. Yet few studies have sought to quantify these benefits. As seagrass habitat continues to suffer a high rate of loss globally and with the growing emphasis on compensatory restoration, valuation of the ecosystem services associated with seagrass habitat is increasingly important. We undertook a meta-analysis of juvenile fish abundance at seagrass and control sites to derive a quantitative estimate of the enhancement of juvenile fish by seagrass habitats in southern Australia. Thirteen fish of commercial importance were identified as being recruitment enhanced in seagrass habitat, twelve of which were associated with sufficient life history data to allow for estimation of total biomass enhancement. We applied von Bertalanffy growth models and species-specific mortality rates to the determined values of juvenile enhancement to estimate the contribution of seagrass to commercial fish biomass. The identified species were enhanced in seagrass by 0.98 kg m−2 y−1, equivalent to ∼$A230,000 ha−1 y−1. These values represent the stock enhancement where all fish species are present, as opposed to realized catches. Having accounted for the time lag between fish recruiting to a seagrass site and entering the fishery and for a 3% annual discount rate, we find that seagrass restoration efforts costing $A10,000 ha−1 have a potential payback time of less than five years, and that restoration costing $A629,000 ha−1 can be justified on the basis of enhanced commercial fish recruitment where these twelve fish species are present. [Copyright &y& Elsevier]

Abstract: Seagrasses have high conservation and human-use values, but around the world they are being damaged by human activities. Compared to the larger spatial scale at which some human activities affect estuaries and their seagrasses (e.g. catchment disturbance, dredging, pollution, trawling), recreational boating and infrastructure of moorings and docks act at smaller scales. However, the cumulative effects contribute to stresses acting on seagrass beds. This study assessed the effects of docks on the native seagrass Zostera muelleri subsp. capricorni in an estuary in south-east Australia and of current management practices designed to reduce dock impacts on this seagrass. A field survey found that seagrass biomass was significantly reduced below docks, and the effects were not influenced by dock orientation. Management practices requiring the use of a mesh decking to provide greater light penetration reduced, but did not eliminate, the reduction in seagrass biomass caused by docks. A modified beyond BACI experiment provided evidence for a causal link between the installation of wooden or mesh docks and reductions in biomass of seagrass. The reduction in biomass was apparent 6 mo after dock installation, and by 26 mo seagrass biomass had declined by at least 90%. Faced with increasing coastal populations, increases in recreational use, and continued pressures from other human activities, alternative management practices that further minimize the effects of docks are needed. [Copyright &y& Elsevier]

We investigated phylogeography, demography, and population connectivity of the dugong ( Dugong dugon) in Australian waters using mitochondrial control region DNA sequences from 177 Australian dugongs and 11 from elsewhere. The dugong is widespread in shallow Indo-West Pacific waters suitable for growth of its main food, seagrass. We hypothesized that the loss of habitat and creation of a land barrier (the Torres Strait landbridge) during low sea level stands associated with Pleistocene glacial cycles have left a persisting genetic signature in the dugong. The landbridge was most recently flooded about 7,000 yr ago. Individual dugongs are capable of traveling long distances, suggesting an alternative hypothesis that there might now be little genetic differentiation across the dugong's Australian range. We demonstrated that Australian dugongs fall into two distinct maternal lineages and exhibit a phylogeographic pattern reflecting Pleistocene sea-level fluctuations. Within each lineage, genetic structure exists, albeit at large spatial scales. We suggest that these lineages diverged following the last emergence of the Torres Strait landbridge ( ca. 115 kya) and remained geographically separated until after 7 kya when passage through Torres Strait again became possible for marine animals. Evidence for population growth in the widespread lineage, especially after the last glacial maximum, was detected. [ABSTRACT FROM AUTHOR]

Seagrasses are among the most productive habitats in the marine realm, performing several crucial physical and biological ecosystem services. One group of seagrasses is the family Zosteraceae, which includes three to four genera and >20 species inhabiting temperate waters of both the northern and southern hemisphere. Species delineation depends on the type of data used, ranging from morphological to molecular. The main goal of this study was to better understand the evolution and divergence within the family, using a broad taxon sampling (>90 individuals) representing all species across the entire biogeographical range in both hemispheres and a four-locus approach (ITS1,matK,rbcL,psbA-trnH). The concatenated four-locus analysis supported earlier studies showing four genera in the family:Phyllospadix,Zostera,NanozosteraandHeterozostera. Four species were resolved within the genusZostera, four withinNanozosteraand two withinHeterozostera. No distinction was revealed betweenH.nigracaulis(Australia) andH. chiliensis(Chile), suggesting a very recent introduction to Chile. A time-calibrated phylogeny using therbcL gene revealed an early divergence ofZostera–Nanozostera/Heterozosteraat 14.4 Ma, followed by a late Miocene radiation ofNanozostera–Heterozosteraat 6.4 Ma, and theH.polychalymas–H.nigracaulis/tasmanica/chiliensissplit at 2.3 Ma.Zostera asiaticadiverged from other species ofZosteraat 4.6 Ma. Phylogenetic analyses indicated thatmatK was the most informative single locus, whereaspsbA-trnH (a widely used barcoding locus) was unable to resolve any entities within the Zosteraceae. A commonly used barcoding combination for plants,rbcL/matK, distinguished all genera, but was unable to resolve several species. [ABSTRACT FROM AUTHOR]

Highlights: [•] We measured trace elements in seagrass, sediment and porewater in gradient from drain. [•] Trace element content greater in Halophia than Ruppia for Al, Fe, and As. [•] Sediment-route pathway for Fe, Al, As and Ni important for seagrass bioaccumulation. [•] Metal content of seagrass informs about possible sources and accumulation pathways. [ABSTRACT FROM AUTHOR]

Abstract: Permanent boat moorings have contributed to the decline of seagrasses worldwide, prompting the development of ‘seagrass-friendly’ moorings. We contrasted seagrass cover and density (predominantly Posidonia australis) in the vicinity of three mooring types and nearby reference areas lacking moorings in Jervis Bay, Australia. We examined two types of ‘seagrass-friendly’ mooring and a conventional ‘swing’ mooring. ‘Swing’ moorings produced significant seagrass scour, denuding patches of ∼9 m radius. Seagrass-friendly ‘cyclone’ moorings produced extensive denuded patches (average radius of ∼18 m). Seagrass-friendly ‘screw’ moorings, conversely, had similar seagrass cover to nearby reference areas. Our findings reinforce previous work highlighting the negative effects of ‘swing’ and ‘cyclone’ moorings. In contrast, the previously unstudied ‘screw’ moorings were highly effective. We conclude that regular maintenance of moorings and the monitoring of surrounding seagrass are required to ensure that ‘seagrass-friendly’ moorings are operating effectively. This is important, as following damage Posidonia will take many decades to recover. [Copyright &y& Elsevier]

Abstract: There is a world-wide trend for deteriorating water quality and light levels in the coastal zone, and this has been linked to declines in seagrass abundance. Localized management of seagrass meadow health requires that water quality guidelines for meeting seagrass growth requirements are available. Tropical seagrass meadows are diverse and can be highly dynamic and we have used this dynamism to identify light thresholds in multi-specific meadows dominated by Halodule uninervis in the northern Great Barrier Reef, Australia. Seagrass cover was measured at ∼3 month intervals from 2008 to 2011 at three sites: Magnetic Island (MI) Dunk Island (DI) and Green Island (GI). Photosynthetically active radiation was continuously measured within the seagrass canopy, and three light metrics were derived. Complete seagrass loss occurred at MI and DI and at these sites changes in seagrass cover were correlated with the three light metrics. Mean daily irradiance (I d) above 5 and 8.4molm−2 d−1 was associated with gains in seagrass at MI and DI, however a significant correlation (R =0.649, p <0.05) only occurred at MI. The second metric, percent of days below 3molm−2 d−1, correlated the most strongly (MI, R =−0.714, p <0.01 and DI, R =−0.859, p =<0.001) with change in seagrass cover with 16–18% of days below 3molm−2 d−1 being associated with more than 50% seagrass loss. The third metric, the number of hours of light saturated irradiance (H sat) was calculated using literature-derived data on saturating irradiance (E k). H sat correlated well (R =0.686, p <0.01; and DI, R =0.704, p <0.05) with change in seagrass abundance, and was very consistent between the two sites as 4 H sat was associated with increases in seagrass abundance at both sites, and less than 4 H sat with more than 50% loss. At the third site (GI), small seasonal losses of seagrass quickly recovered during the growth season and the light metrics did not correlate (p >0.05) with change in percent cover, except for I d which was always high, but correlated with change in seagrass cover. Although distinct light thresholds were observed, the departure from threshold values was also important. For example, light levels that are well below the thresholds resulted in more severe loss of seagrass than those just below the threshold. Environmental managers aiming to achieve optimal seagrass growth conditions can use these threshold light metrics as guidelines; however, other environmental conditions, including seasonally varying temperature and nutrient availability, will influence seagrass responses above and below these thresholds. [Copyright &y& Elsevier]

The article presents a study on the diet and nutrition of the western rock lobster Panulirus cygnus as influenced by the spatial arrangement of habitat patches. The diet and nutrition of lobsters that are taken from 8 shallow patch-reef sites on the lower west coast of Australia in April and October 2005 was analyzed using stable isotopes and gut contents. It was found out that seagrass is an important habitat for lobster prey and that Macroalgae is the most likely autochthonus energy source that drives the production of Panulirus Cygnus in shallow coastal waters.

Abstract: We used an established seagrass monitoring programme to examine the short and longer-term impacts of an oil spill event on intertidal seagrass meadows. Results for potentially impacted seagrass areas were compared with existing monitoring data and with control seagrass meadows located outside of the oil spill area. Seagrass meadows were not significantly affected by the oil spill. Declines in seagrass biomass and area 1month post-spill were consistent between control and impact meadows. Eight months post-spill, seagrass density and area increased to be within historical ranges. The declines in seagrass meadows were likely attributable to natural seasonal variation and a combination of climatic and anthropogenic impacts. The lack of impact from the oil spill was due to several mitigating factors rather than a lack of toxic effects to seagrasses. The study demonstrates the value of long-term monitoring of critical habitats in high risk areas to effectively assess impacts. [Copyright &y& Elsevier]

Abstract: A large-scale, manipulative experiment was conducted to examine the extent and rate of recovery of meadows of the temperate Australian seagrass, Amphibolis griffithii to different light-reduction scenarios typical of dredging operations, and to identify potential indicators of recovery from light reduction stress. Shade cloth was used to mimic different intensities, durations and start times of light reduction, and then was removed to assess the recovery. The meadow could recover from 3months of light stress (5–18% ambient) following 10months re-exposure to ambient light, even when up to 72% of leaf biomass was lost, much faster recovery rates than has previously been observed for large seagrasses. However, when the meadow had been shaded for 6–9months and more than 82% of leaf biomass was lost, no recovery was detected up to 23months after the light stress had ceased, consistent with other studies. Five potential indicators of recovery were recommended. [Copyright &y& Elsevier]

Abstract: The invasive saltmarsh grass Spartina is widely considered a threat to the health of coastal ecosystems in south-eastern Australia, however, the ecological impacts of Spartina on estuarine communities are poorly understood. The largest infestation of Spartina in Victoria occurs in Anderson Inlet. The relative contribution of Spartina, vs. non-invasive autotrophs, to the nutrition of an estuarine fish, Macquaria colonorum was assessed using stable isotopes and gut content analyses. The δ13C and δ15N compositions of autotrophs and M. colonorum varied spatially across the study area. Based on gut content analyses, adults and juveniles were between two and three trophic levels above autotrophs. Isosource modelling of δ13C signatures, suggested several autotrophs contributed to the nutrition of M. colonorum with a combination of seagrass and Spartina likely important contributors, particularly for adults. Isotopic sulphur was subsequently used to distinguish between seagrass and Spartina. Modelling of δ13C and δ34S signatures of M. colonorum and a subset of autotrophs again indicated a combination of seagrass and Spartina was likely a major contributor to nutritional support of M. colonorum. Given the limited areal extent of seagrass within Anderson Inlet, current Spartina eradication programs may compromise the nutritional support of M. colonorum. [ABSTRACT FROM AUTHOR]

The dugong is the only herbivorous mammal that is strictly marine and a seagrass community specialist. The pasture available to the dugong varies with the tides because seagrass occurs in both intertidal and subtidal areas. We GPS-tracked seven dugongs within a 24 km2, intensively used seagrass habitat in subtropical Australia in winter. We modeled resource selection within the habitat by comparing the dugongs' use of space with the distribution of seagrass in an area defined using the combined space-use of the tracked animals. Selection by dugongs for seagrass quantity (biomass) and quality (nutrients) was analyzed within six time/tide combinations to examine the influences of tidal periodicity and the diel cycle on resource selection. Dugong habitat use was consistently centered over seagrass patches with high nitrogen concentrations, except during the day at low tides when the animals had fewer habitat choices and their space use was centered over high seagrass biomass. The association of dugongs with seagrass high in starch was positive during both day and night high tides when the animals could access the intertidal areas where seagrass biomass was generally low. Associations between dugongs and seagrass species were less definite, reflecting the potential for dugongs to exploit several species. Our model of dugong resource selection suggests that nitrogen is the primary limiting nutrient for dugong populations and also confirms the preference of dugongs for high-energy foods. [ABSTRACT FROM AUTHOR]

The article discusses research on the importance of identifying and conserving sites in protecting the recruitment of coastal fish populations. It references a study by John R. Ford and colleagues at the University of New South Wales in Sydney, published in the June 3, 2010 issue of "Marine Ecology Progress Series." The researchers studied the abundance of juvenile coastally spawned (CS) fish within seagrass beds in four estuary entrances that are located on the east coast of Australia. They conclude that the critical seagrass habitat for CS settlement within the observed estuary entrances seems to be a function of the spatial distribution of habitat and the hydrodynamic regime.

Abstract: Empirical relationships are found for catchment runoff and efficiency of nitrogen-load delivery to lagoons in New South Wales, Australia. Empirical results and analysis of biogeochemical mechanisms are used to estimate the potential for eutrophication and changes in ecological state that result from increased total nitrogen export from a catchment to a lagoon. The link between empirical results and results from a complex biogeochemical model is illustrated by analysing an analytical model of intermediate complexity. Excluding conditions under which there is a change of ecological state, key features of complex biogeochemical models are argued to depend more upon source and sink terms than upon the many complex mechanisms that conservatively transform nitrogen from one form to the other. In lagoons the relative role of flushing and biogeochemical sinks/sources depends upon a flushing speed scale defined as mean depth divided by the flushing time scale. The potential for eutrophication is introduced as a more practical metric for ecosystem management than eutrophication. Potential for eutrophication and the light extinction coefficient scale according to the square root of effective total nitrogen load per waterway area. Such scaling relationships, and hypsometry, can be used to estimate coverage of lagoons with benthic macrophytes and how sensitive this coverage is to the effective total nitrogen load per unit area of waterway. Calculations show hypsometry to be a strong constraint on ecosystem function. [Copyright &y& Elsevier]

The northeastern shore of Gulf St Vincent, South Australia is a mesotidal, low-wave-energy coastline, characterised by tidal-dominated bioclastic carbonate sedimentation. Distinctive assemblages of subtidal, intertidal and supratidal marine plants and invertebrate animals have resulted in well defined, adjacent bio- and litho-facies that lie parallel to each other across broad areas of coastal sedimentation. At Port Gawler, the intertidal zone is bounded by a landward high-tide beach and a subtidal Posidonia australis seagrass meadow seaward. Thirty years ago, within the immediate study area, this intertidal zone comprised an inner sandflat and an outer muddy seagrass meadow dominated by Zostera muelleri, the two areas separated by a shallow tidal distributary. Avicennia marina is a species of mangrove that has colonised much of the protected, tidal-dominated coasts of South Australia. Propagules of this tree readily take root in intertidal mud, with a natural ecological succession of Z. muelleri followed by A. marina. Over the time of observation, juvenile mangroves have progressively colonised a narrow zone along the landward side of the muddy seagrass meadow; they appear unable to colonise a sandy substrate. Juveniles advanced rapidly southward from mature woodland in the north towards equally mature woodland in the south. From the initial tap root, juvenile plants send out radial roots from which project, snorkel-like, an array of vertical pneumatophores. Redistributed algal, seagrass and other organic flotsam collect around these vertically protruding pneumatophores, promoting accumulation of organic sediment. Within the newly forming mangrove woodland, there has been pronounced sediment aggradation of >0.5 m, greatly altering the dynamics of tidal flow. Tidal flow is now largely constrained to a channel between the mature southern woodland and that formed most recently. Higher velocity flows through this channel have exhumed populations of infaunal bivalves, and floodtide and ebbtide deltas of coarse bioclastic sediments are a consequence. The aggraded sediment of the new woodland shelters the area landward. Consequently, more muddy sediments are now covering what was formerly bare sandflat, thus providing new areas for mangrove colonisation. Migration of mangroves towards the high-tide beach is inevitable and will be limited only by their need for regular flushing of accumulated salt from their roots by seawater at high tide. Thus, A. marina drives rapid geomorphic change in the tidal-dominated coasts of the South Australian gulfs. In similar coastal areas of southeast Asia, where intertidal muddy sediments predominate, this species appears to be an ideal candidate for reforestation projects. Juvenile plants should grow successfully and rapidly, so preparing coastal environments for the establishment of more ecologically diverse mangrove communities. [ABSTRACT FROM AUTHOR]

The article presents a study which compares the soft-sediment macrobenthic assemblages of those habitat invaded by Caulerpa taxifolia and those which are uninvaded in 2 estuaries in Southern Australia. The result shows that habitat invaded by Caulerpa taxifolia has a less abundant infauna but more abundant of epifauna compared to unvegetated sediment. It reveals that the changes in soft-sediment macroinvertebrate assemblages are caused by an invasion of Caulerpa taxifolia and suggests that infauna are vulnerable to invasion.

Abstract: Involvement in scientifically structured habitat monitoring is a relatively new concept to the peoples of Torres Strait. The approach we used was to focus on awareness, and to build the capacity of groups to participate using Seagrass-Watch as the vehicle to provide education and training in monitoring marine ecosystems. The project successfully delivered quality scientifically rigorous baseline information on the seasonality of seagrasses in the Torres Strait—a first for this region. Eight seagrass species were identified across the monitoring sites. Seagrass cover varied within and between years. Preliminary evidence indicated that drivers for seagrass variability were climate related. Generally, seagrass abundance increased during the north-west monsoon (Kuki), possibly a consequence of elevated nutrients, lower tidal exposure times, less wind, and higher air temperatures. Low seagrass abundance coincided with the presence of greater winds and longer periods of exposure at low tides during the south-east trade wind season (Sager). No seasonal patterns were apparent when frequency of disturbance from high sedimentation and human impacts was high. Seagrass-Watch has been incorporated in to the Thursday Island High School''s Marine Studies Unit ensuring continuity of monitoring. The students, teachers, and other interested individuals involved in Seagrass-Watch have mastered the necessary scientific procedures to monitor seagrass meadows, and developed skills in coordinating a monitoring program and skills in mentoring younger students. This has increased the participants’ self-esteem and confidence, and given them an insight into how they may participate in the future management of their sea country. [Copyright &y& Elsevier]

Abstract: In this study, we examined the photosynthetic responses of five common seagrass species from a typical mixed meadow in Torres Strait at a depth of 5–7m using pulse amplitude modulated (PAM) fluorometry. The photosynthetic response of each species was measured every 2h throughout a single daily light cycle from dawn (6am) to dusk (6pm). PAM fluorometry was used to generate rapid light curves from which measures of electron transport rate (ETR max ), photosynthetic efficiency (α), saturating irradiance (Ek ) and light-adapted quantum yield (ΔF/F′ m ) were derived for each species. The amount of light absorbed by leaves (absorption factor) was also determined for each species. Similar diurnal patterns were recorded among species with 3–4 fold increases in maximal electron rate from dawn to midday and a maintenance of ETR max in the afternoon that would allow an optimal use of low light by all species. Differences in photosynthetic responses to changes in the daily light regime were also evident with Syringodium isoetifolium showing the highest photosynthetic rates and saturating irradiances suggesting a competitive advantage over other species under conditions of high light. In contrast Halophila ovalis, Halophila decipiens and Halophila spinulosa were characterised by comparatively low photosynthetic rates and minimum light requirements (i.e. low Ek ) typical of shade adaptation. The structural makeup of each species may explain the observed differences with large, structurally complex species such as Syringodium isoetifolium and Cymodocea serrulata showing high photosynthetic effciciencies (α) and therefore high-light-adapted traits (e.g. high ETR max and Ek ) compared with the smaller Halophila species positioned lower in the canopy. For the smaller Halophila species these shade-adapted traits are features that optimise their survival during low-light conditions. Knowledge of these characteristics and responses improves our understanding of the underlying causes of changes in seagrass biomass, growth and survival that occur when modifications in light quantity and quality arise from anthropogenic and climatic disturbances that commonly occur in Torres Strait. [Copyright &y& Elsevier]

Abstract: Understanding, monitoring and modelling attributes of seagrass biodiversity, such as species composition, richness, abundance, spatial patterns, and disturbance dynamics, requires spatial information. This work assessed the accuracy of commonly available airborne hyper-spectral and satellite multi-spectral image data sets for mapping seagrass species composition, horizontal horizontal-projected foliage cover and above-ground dry-weight biomass. The work was carried out on the Eastern Banks in Moreton Bay, Australia, an area of shallow and clear coastal waters, containing a range of seagrass species, cover and biomass levels. Two types of satellite image data were used: Quickbird-2 multi-spectral and Landsat-5 Thematic Mapper multi-spectral. Airborne hyper-spectral image data were acquired from a CASI-2 sensor using a pixel size of 4.0 m. The mapping was constrained to depths shallower than 3.0 m, based on past modelling of the separability of seagrass reflectance signatures at increasing water depths. Our results demonstrated that mapping of seagrass cover, species and biomass to high accuracy levels (>80%) was not possible across all image types. For each parameter mapped, airborne hyper-spectral data produced the highest overall accuracies (46%), followed by Quickbird-2 and then Landsat-5 Thematic Mapper. The low accuracy levels were attributed to the mapping methods and difficulties in matching locations on image and field data sets. Accurate mapping of seagrass cover, species composition and biomass, using simple approaches, requires further work using high-spatial resolution (<5 m) and/or hyper-spectral image data. Further work is required to determine if and how the seagrass maps produced in this work are suitable for measuring attributes of seagrass biodiversity, and using these data for modelling floral and fauna biodiversity properties of seagrass environments, and for scaling-up seagrass ecosystem models. [Copyright &y& Elsevier]

Macroinvertebrate composition, abundance and biomass were investigated at four intertidal sites throughout the Robbins Passage wetlands, Tasmania, over a 12-month period, in order to identify differences among and within sites, and to determine whether environmental variables could explain these differences. As this region is the most important shorebird area in Tasmania, we wanted to quantify the potential food source for shorebirds within the wetlands. Thirty-five taxa from 28,928 individuals were identified, with a mean abundance of 6026.6 ind m−2 and biomass of 27.1 gDW m−2. Bivalves and gastropods dominated the assemblage in terms of abundance and biomass (79% and 60%, respectively). There was a significant interaction among tidal level, site and season for invertebrate abundance and diversity, while biomass differed significantly among sites. In general, the mid-intertidal stratum had the greatest invertebrate density and diversity, while the low intertidal stratum had the greatest biomass. Community composition varied among the four sites, with the bivalve Paphies elongata dominating at two of the sites, while gastropods and polychaetes were more abundant at the other sites. Differences in invertebrate composition and abundance could partly be explained by seagrass biomass, i.e., dry mass of seagrass leaves and roots. Areas with seagrass had increased invertebrate abundance and diversity, but mean sediment particle size, % organic carbon and % seagrass cover had no significant effect. These results will assist in the investigation of habitat use by shorebirds and the identification of important shorebird feeding areas within the wetlands. [ABSTRACT FROM AUTHOR]

Abstract: Western Australia has a rich diversity of seagrasses, many of which are meadow-forming species with a high diversity of associated epiphytes. Potential food sources and dominant invertebrates and fishes were collected in a non-quantitative sampling programme designed to examine the variability in naturally occurring isotopes (13C/12C and 15N/14N) within an Amphibolis griffithii dominated seagrass bed in Western Australia. The aims of this study were to determine the isotopic composition of the organisms, and to determine the sources of carbon available to consumers using the variations in the ratio of 15N/14N and 13C/12C among organisms in the seagrass assemblage. Autotrophs showed a wide distribution of δ 13C values, with seagrass material significantly enriched in 13C relative to macroalgal sources by >10‰. This variation allowed us to successfully identify macroalgae as the main contributor of carbon to the trophic structure. δ 15N ratios did not vary to the degree that would make it useful as tracer, but it was applied to estimating the total number of trophic transfers of nitrogen. Analysis of δ 15N values suggested that four trophic positions were present, with fishes (Acanthaluteres vittiger, Scobonichthys granulatus and Siphonognathus radiatus, Pelsartia humeralis, Pelates sexlineatus, Leviprora inops, Odax acroptilus and Notolabrus parilus) occupying the top two levels. δ 13C of seston (20–200μm) and sedimentary organic matter indicate that seagrass material is the main contributor to these two carbon pools, and that very little of it is incorporated into the trophic structure. [Copyright &y& Elsevier]

Abstract: Tissue samples of liver and blubber were salvaged from fifty-three dugong (Dugong dugon) carcasses stranded along the Queensland coast between 1996 and 2000. Liver tissue was analysed for a range of heavy metals and blubber samples were analysed for organochlorine compounds. Metal concentrations were similar in male and female animals and were generally highest in mature animals. Liver concentrations of arsenic, chromium, iron, lead, manganese, mercury and nickel in a number of individual animals were elevated in comparison to concentrations previously reported in Australian dugong. Dieldrin, DDT (and its breakdown products) and/or heptachlor epoxide were detected in 59% of dugong blubber samples. In general, concentrations of organochlorines were similar to those reported in dugong 20 years earlier, and were low in comparison to concentrations recorded from marine mammal tissue collected elsewhere in the world. With the exception of lead, the extent of carcass decomposition, the presence of disease or evidence of animal starvation prior to death did not significantly affect dugong tissue concentrations of metals or organochlorines. The results of the study suggest that bioaccumulation of metals and organochlorine compounds (other than dioxins) does not represent a significant risk to Great Barrier Reef dugong populations, particularly in the context of other pressures associated with coastal development and other anthropogenic activities. [Copyright &y& Elsevier]

Abstract: Low concentrations of herbicides (up to 70ngl−1), chiefly diuron (up to 50ngl−1) were detected in surface waters associated with inter-tidal seagrass meadows of Zostera muelleri in Hervey Bay, south-east Queensland, Australia. Diuron and atrazine (up to 1.1ngg−1 dry weight of sediment) were detected in the sediments of these seagrass meadows. Concentration of the herbicides diuron, simazine and atrazine increased in surface waters associated with seagrass meadows during moderate river flow events indicating herbicides were washed from the catchment to the marine environment. Maximum herbicide concentration (sum of eight herbicides) in the Mary River during a moderate river flow event was 4260ngl−1. No photosynthetic stress was detected in seagrass in this study during low river flow. However, with moderate river flow events, nearshore seagrasses are at risk of being exposed to concentrations of herbicides that are known to inhibit photosynthesis. [Copyright &y& Elsevier]

A survey of fishes in small, soft-substrata tidepools was undertaken between May and September 1996 at two sites in south-east Queensland, Australia. Pools sampled varied in size (0.005-2.8 m2 surface area), location within the intertidal zone, and habitat structure. A total of 680 fish representing 18 species from eight families were caught. Gobiidae was the dominant family andFavonigobius exquisites, Arenigobius frenatusandFavonigobius lateraliswere the most abundant species. Most fish caught were juveniles, and onlyF. lateraliswas represented by all life-history stages (from late larval). The mean density of fish was 4.7 m-2 and mean species richness was 2.3 m-2. Both abundance and species richness increased with pool size and decreased with distance up the intertidal zone. The distribution patterns of fish in these soft-substrata tidepools were similar to patterns noted for fish in rocky tidepools. [ABSTRACT FROM AUTHOR]