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Introduction Sand aprons are ubiquitous depositional sedimentary features that offer insights into the sediment dynamics of coral reef environments. Global studies found that the extent of sand aprons are not related to reef platform size and their widths are a function of environmental factors such as swell period and height, tidal amplitude, latitude, and exposure to wind and waves (Rankey and Garza-Perez 2012). Recent studies using numerical modelling have found that sand aprons in reef flats attain a critical water depth resulting in constant depth (Ortiz and Ashton 2019), and that lagoon infilling through sand apron progradation is a self-limiting process (Rankey 2021). Sand apron progradation is an eco-morphodynamic process and climate change, including intensification and increased frequency of marine heatwaves, ocean and coastal acidification, and changes in wave and tropical storm climates are triggering changes that need to be understood to inform sound management of coral reefs.This paper presents data on the Holocene evolution of the sand aprons on 21 offshore platform reefs located on the southern Great Barrier Reef and how it can be used to infer past wave climates. We then present the recent wave climate for the study area (Smith et al. 2022) and analyse sand apron evolution accordingly. Methods The sand aprons on 21 reefs located on the Capricorn Bunker Group (Southern Great Barrier Reef) were assessed from high-resolution satellite imagery, obtaining digital bathymetric models and digitizing the reef and lagoon contours. We then measured reef area and lagoon area to calculate the percentage of lagoon infilling. The wave climate for the study area was obtained from satellite altimetry using an open-source Python tool (Smith et al. 2020). Preliminary findings Our results showed that the most important factor for lagoon infilling was the size of the reef, with larger reefs typically appearing less infilled than smaller reefs. Wave incidence seemed to be unimportant: the three reefs with less than 50% infill were all medium-sized and exposed to incident waves while all six protected reefs had infilling above 50%. While some authors had pointed out at relative sea-level changes to explain current sand apron stability (Harris et al. 2015), our results show that the self-limiting nature of the sand apron progradation, combined with relative sea-level changes, is a better explanation for sand apron stability. In any case, the extent of the sand apron can be used to infer wave climate at the time of sand apron progradation. For example, for One Tree Reef, one can argue the sand apron could had stopped prograding 4 ka BP because of the self-limiting sediment transport and remained stable until the sea-level fell.The wave climate on the Southern Great Barrier Reef is characterized by significant wave heights (Hs) of 1.7 m and has been stable for the past 33 years (Smith et al. 2022). Future changes in the wave climate, storm frequency, increases in sea level and changes to sediment availability caused by anthropogenic climate change will modify the eco-morphodynamics of the sand aprons and the percentage infilling of the lagoons.

How we understand the contemporary socio-environmental challenges associated with climate change is shaped by our research disciplines. This paper explores how interdisciplinary collaboration can f...

Climate change science is unequivocal on the link between fossil fuels and climate change. Yet, some governments – including those in Australia – fail to meet agreed targets and continue to invest in the coal industry. Scientists and other scholars have expressed concern that the science is not prompting shifts in policy adequate to address current and future effects of climate change. Many have called for other tools – specifically, the arts and social sciences – to investigate and communicate about the environmental and social changes underway. In this context, this article explores the potential of interdisciplinary collaborative song-writing as research practice. Beginning on a boat on Australia’s Great Barrier Reef, the research team adopted singing and song-writing as a method for coming together to reflect upon our research aims and motivations, to explore and express the delight and grief we were experiencing in this climate-changing land and seascape and potentially to reach new audiences and create different affects. Our multidisciplinary expertise offered impetus to pursue a hybrid form: an original song written, professionally recorded and vinyl pressed; scholarly notes to expand on our song lyrics; visual presentation of our music as annotated score; and written reflections on the process and its contribution to knowledge. Here, we present and explore the possibilities of song-writing as creative geographical practice.

Coral reefs provide critical ecological and geomorphic (e.g. sediment production for reef-fronted shoreline maintenance) services, which interact in complex and dynamic ways. These services are under threat from climate change, requiring dynamic modelling approaches that predict how reef systems will respond to different future climate scenarios. Carbonate budgets, which estimate net reef calcium carbonate production, provide a comprehensive ‘snap-shot’ assessment of reef accretionary potential and reef stability. These budgets, however, were not intended to account for the full suite of processes that maintain coral reef services or to provide predictive capacity on longer timescales (decadal to centennial). To respond to the dual challenges of enhancing carbonate budget assessments and advancing their predictive capacity, we applied a novel model elicitation and review method to create a qualitative geo-ecological carbonate reef system model that links geomorphic, ecological and physical processes. Our approach conceptualizes relationships between net carbonate production, sediment transport and landform stability, and rates knowledge confidence to reveal major knowledge gaps and critical future research pathways. The model provides a blueprint for future coral reef research that aims to quantify net carbonate production and sediment dynamics, improving our capacity to predict responses of reefs and reef-fronted shorelines to future climate change.

Robust data are the base of effective gender diversity policy. Evidence shows that gender inequality is still pervasive in science, technology, engineering and mathematics (STEM). Coastal geoscience and engineering (CGE) encompasses professionals working on coastal processes, integrating expertise across physics, geomorphology, engineering, planning and management. The article presents novel results of gender inequality and experiences of gender bias in CGE, and proposes practical steps to address it. It analyses the gender representation in 9 societies, 25 journals, and 10 conferences in CGE and establishes that women represent 30% of the international CGE community, yet there is under-representation in prestige roles such as journal editorial board members (15% women) and conference organisers (18% women). The data show that female underrepresentation is less prominent when the path to prestige roles is clearly outlined and candidates can self-nominate or volunteer instead of the traditional invitation-only pathway. By analysing the views of 314 survey respondents (34% male, 65% female, and 1% ‘‘other’’), we show that 81% perceive the lack of female role models as a key hurdle for gender equity, and a significantly larger proportion of females (47%) felt held back in their careers due to their gender in comparison with males (9%). The lack of women in prestige roles and senior positions contributes to 81% of survey respondents perceiving the lack of female role models in CGE as a key hurdle for gender equality. While it is clear that having more women as role models is important, this is not enough to effect change. Here seven practical steps towards achieving gender equity in CGE are presented: (1) Advocate for more women in prestige roles; (2) Promote high-achieving females; (3) Create awareness of gender bias; (4) Speak up; (5) Get better support for return to work; (6) Redefine success; and, (7) Encourage more women to enter the discipline at a young age. Some of these steps can be successfully implemented immediately (steps 1–4), while others need institutional engagement and represent major societal overhauls. In any case, these seven practical steps require actions that can start immediately.

Vegetation canopies represent the main ecosystems on intertidal landforms and they clearly respond to changes in coastal environments. Climate change, including temperature, precipitation and sea level rise, are affecting the health and distribution of coastal vegetation, as well as the runoff and sedimentation rates that can impact coastal areas. This study has used the normalized difference vegetation index (NDVI) to investigate vegetation canopy dynamics on three different coastal sites in southeastern Australia over the past 47 years (1975–2015). NDVIs temporal-datasets have been built from satellite images derived from Landsat 1–8. These were then regressed to the climatic and geomorphic variables. Results show clear increases in NDVI at Towamba and Wandandian Estuaries, but a decline at Comerong Island (southeastern Australia). The sedimentation rate has the most significant positive impact on NDVI since it has the potential to provide additional space for vegetation. Temperature and sea level rise have positive effects, except on Comerong Island, but rainfall has no significant effect on the NDVI at any site. Different NDVI trends have been recorded at these three coastal sites reflecting different correlations between the vegetation, climatic and geomorphic (as independent) variables. The geomorphological characteristics of the highly-dynamic intertidal estuarine landforms, which are subject to active erosion and deposition processes, have the largest impact on vegetation cover and, hence, on NDVI. Assessing the vegetation canopy using NDVI as an evaluation tool has provided temporal-dynamic datasets that can be correlated to the main individual environmental controls. Such knowledge will allow resource managers to make more informed decisions for sustainable conservation plans following the evaluation the potential consequences of any environmental changes.

The importance of sampling effort in the statistical exploration of spatial autocorrelation is demonstrated for benthic macroinvertebrate assemblages within the intertidal warm-temperate Knysna estuary, South Africa. While the role of spatial scale in determining autocorrelation patterns in ecological populations has been noted, the effects of changing sampling effort (e.g., sample size) have rarely been explored; neither have the nature of any changes with sample size. Invertebrate assemblages were sampled from a single grid lattice comprised of 48 sampling stations at four sample sizes (0.0015, 0.0026, 0.0054 and 0.01 m2). Four metrics were investigated: assemblage abundance, frequency (species density), and numbers of the two most abundant species in the area Simplisetia erythraeensis and Prionospio sexoculata. Spatial autocorrelation was estimated for each sample size from the global Moran’s I. For a range of distance classes, Moran’s I correlograms were constructed, these plotted autocorrelation estimates as a function of the separation distance between point samples. Spatial autocorrelation was present in three of the metrics (assemblage abundance frequency and Prionospio abundance), but not for Simplisetia abundance. The estimated magnitude of spatial autocorrelation varied across sampling units for all four assemblage and species metrics (global Moran’s I ranged from 0.5 to − 0.07). Correlograms indicated that optimal sampling interval distances fell in the region of 8 m for Simplisetia and 19 m for the remaining three metrics. These distances indicate the dimensions of the processes (both biotic and abiotic) that determine spatial patterning in the microbenthic intertidal invertebrates sampled.

Carbonate production on coral reefs is responsible for the provision of beach sands, for the maintenance of seawater chemical balances and for the growth of reef structure and associated habitat complexity. Key carbonate producers including hard coral, crustose coralline algae, foraminiferal sand and Halimeda were mapped from satellite imagery (spatial resolution 2.5 m, mean overall accuracy = 81%) and an upscaling model was applied to estimate carbonate production. A sensitivity analysis was conducted to evaluate the influence of employing different calcification rates for live coral on the upscaling model. Contemporary coral reef carbonate production for the 21 reef platforms of the Capricorn-Bunker Group (southern Great Barrier Reef) is estimated to be between 489,000 and 659,000 t per year based on seawater chemistry, community composition, calcification rates and reef structural complexity (rugosity). The upscaling model was relatively insensitive to different parameterisations of live coral calcification employed, probably due to live coral being a relatively minor contributor by area (approximately 18% of total reef area throughout the study region). This suggests regional scale seafloor characteristics, such as percentage of area dominated by substrates prone to dissolution (e.g. coral rubble), have a strong bearing on calcium carbonate production and need to be given greater consideration The upscaling framework presented provides a new method for quantifying regional carbonate production that could be applied globally, and provides a valuable baseline against which future changes to carbonate production in this region can be assessed.

Sediment transport is a key driver of reef zonation and biodiversity, where an understanding of sediment dynamics gives insights into past reef processes and allows the prediction of geomorphic responses to changing environmental conditions. However, modal conditions within the back-reef seldom promote sediment transport, hence direct observation is inherently difficult. Large benthic foraminifera (LBF) have previously been employed as ‘tracers’ to infer sediment transport pathways on coral reefs, as their habitat is largely restricted to the algal flat and post-mortem, their calcium carbonate test is susceptible to sediment transport forces into the back-reef. Foraminiferal test abundance and post-depositional test alteration have been used as proxies for sediment transport, although the resolution of these measures becomes limited by low test abundance and the lack of variation within test alteration. Here we propose the novel use of elemental ratios as a proxy for sediment transport. Two species, Baculogypsina sphaerulata and Calcarina capricornia, were analysed using a taphonomic index within One Tree and Lady Musgrave reefs, Great Barrier Reef (Australia). Inductively coupled plasma-atomic emission spectrometry (ICP-AES) was used to determine Mg/Ca and Sr/Ca and these ratios were compared with taphonomic data. Decreases in test Mg/Ca accompany increases in Sr/Ca in specimens from algal-flat to lagoonal samples in both species, mirroring trends indicated by taphonomic values, therefore indicating a relationship with test alteration. To delineate mechanisms driving changes in elemental ratios, back-scattered electron (BSE) images, elemental mapping and in situ quantitative spot analyses by electron microprobe microanalysis (EPMA) using wavelength dispersive X-ray spectrometers (WDS) were performed on un-altered algal flat and heavily abraded tests for both species. EPMA analyses reveal heterogeneity in Mg/Ca between spines and the test wall, implying the loss of appendages results in a decrease in Mg/Ca. BSE imaging and WDS elemental mapping provided evidence for cementation, facilitated by microbial-boring as the primary cause of increasing Sr/Ca. These novel proxies hold advantages over taphonomic measures and further provide a rapid method to infer sediment transport pathways within back-reef environments.

Damming rivers causes two main problems affecting a river's geomorphic ecosystem and its water quality. The Tallowa Dam on the Shoalhaven River in southeastern NSW, Australia, provides a case study to find the best sustainable solutions to avoid these problems. The project uses a civil-infrastructure idea to design a grid of collector pipes from the reservoir bottom surface. Spatial data analysis using ArcGIS 10.2 is used to determine the best grid location for the pipes in the reservoir. Water and sediment samples have been analysed for grain size, heavy metal and organic matter contents. The dam has led to a significant decline in sediment transport and water discharge to the lower reaches of the river which has resulted in greater erosion of sediment and higher salinity rates within the lower river and coastal streams. Water quality in the reservoir has been affected by increased sediment accumulation, particularly mud, which has increased the amount of heavy metal and nutrient pollution that could eventually affect the water users. A proposed solution is to use over-storage water to remove accumulated sediment from the base of the dam through a net of collector pipes controlled by auto-mechanical gates, instead of flowing over the top of the dam. This would maximize the volume of upstream sediment and contained pollutants that can be released from the reservoir into the downstream river ecosystems as well as providing better water quality and a longer water storage time.

As the range of human uses and demands on the world's oceans and coasts diversifies, there is a growing need for a sustainable relationship between human society and the marine environment. In its ...

We assess 90 years of change on a Low Wooded Island (Low Isles, Great Barrier Reef), employing drones and topographic profiling to accurately survey ramparts, mangroves, the reef flat and the sand cay. A comparison with maps from the 1928–1929 Great Barrier Reef Expedition revealed the redistribution of an outer rampart and inward movement of shingle ridges. Remarkable lateral expansion of the mangrove woodland some 400 m has occurred as carbonate sand deposition has increased reef flat elevation, obscuring coral microatolls. The sand cay has stayed relatively constant in size, moving approximately 44 m in a northeasterly direction and rotating slightly. We conclude that the existing configuration of landforms probably represents an equilibrium with local biophysical conditions, including sea level, wave dynamics, vegetation growth, storms and cyclones. The variable nature of ramparts and the presence of a trough that prevents the continuous spread of mangroves across a uniformly flat colonization surface precludes the interpretation of landform changes with respect to a geomorphic evolutionary sequence. Moreover, longer-term implications of environmental change for these landforms can only be evaluated once the specific nature of the local carbonate budget, including the relative contribution of corals, foraminifera and Halimeda has been elucidated.

This study presents an analysis of shoreline change on reef islands using unmanned aerial vehicle (UAV)-derived orthomosaics and digital surface models (DSMs) collected on Sipadan Island, Sabah, Malaysia, and Sasahura Ite Island, Isabel Province, Solomon Islands. The high resolution of UAV-derived orthomosaics enabled changes in the position of the base of beach to be detected with confidence. The accuracy of the UAV-derived DSMs was assessed against equivalent topographic profiles via root-mean-square error, and found to be &lt, 0.21 m in all but one case, this demonstrates the potential for using UAV-derived DSMs to interpret three-dimensional island beach morphology and detect patterns of geomorphic change. The correlation between planimetric and volumetric change along selected beach transects was also investigated and found to be variable, indicating that a multifaceted approach including both planimetric (two-dimensional) and volumetric (three-dimensional) metrics is of value when analysing reef-island change. However, interpretations of UAV-derived data must carefully consider errors associated with global positioning system (GPS) positioning, the distribution of ground control points, the chosen UAV flight parameters, and the data processing methodology. Further application of this technology has the potential to expand our understanding of reef-island morphodynamics and their vulnerability to sea-level rise and other stressors.

Following earlier studies across 2115 → 33 m2 scales (Barnes and Laurie, 2018), patchiness of macrobenthic abundance in intertidal Queensland seagrass was assessed by dispersion indices, spatial autocorrelation and hotspot analysis across a hierarchically-nested series of smaller scales (5.75 → 0.09 m2). Overall patterns of distribution and abundance over larger extents and with greater lag were mirrored across these smaller ones. Assemblage abundance per station varied by a factor of >10, but all three approaches showed effective constancy of total assemblage patchiness across all sub-2115 m2 scales (across-scales-mean Lloyd's IP of 1.06 and global Moran's I of 0.13). Equivalent constancy was also shown by most numerically-dominant species (scaling exponent β = 0.93–1.15). Decreasing patchiness of some species with decreasing scale, however, resulted in two no longer being patchily dispersed across small scales. Significant hotspots of abundance occurred at a constant proportion of stations across scales, against a background of randomly scattered peak-abundance points.

Balls Pyramid is a volcanic monolith rising 552 m from the Tasman Sea, 24 km southeast of the Pacific Ocean's southernmost modern coral reef at Lord Howe Island. High resolution seabed mapping of the shelf surrounding Balls Pyramid has revealed an extensive submerged reef structure in 30–50 m water depth, covering an area of 87 km 2 . Benthic community composition analysis of high-resolution still images revealed abundant scleractinian corals on the submerged reef, extending to a maximum depth of 94 m. Scleractinian coral occurred predominantly in 30–40 m depth where it comprised 13.3% of benthic cover within this depth range. Average scleractinian coral cover for all transects was 6.7±12.2%, with the highest average transect cover of 19.4±14.3% and up to 84% cover recorded for an individual still image. The remaining substrate comprised mixed benthos with veneers of carbonate sand. Benthic data were shown to significantly relate to the underlying geomorphology. BVSTEP analyses identified depth and backscatter as the strongest correlating explanatory variables driving benthic community structure. The prevalence of scleractinian corals on the submerged reef features at Balls Pyramid, and the mesophotic depths to which these corals extend, demonstrates the important role of this subtropical island shelf as habitat for modern coral communities in the southwest Pacific Ocean. As Balls Pyramid is located beyond the known latitudinal limit of coral reef formation, these findings have important implications for potential coral reef range expansion and deep reef refugia under a changing climate.

Large benthic foraminifera (LBFs) are a vital component of coral reef carbonate production, often overlooked due to their small size. These super-abundant calcifiers are crucial to reef calcification by generation of lagoon and beach sands. Reef-scale carbonate production by LBFs is not well understood, and seasonal fluctuations in this important process are largely unquantified. The biomass of five LBF species in their algal flat habitat was quantified in the austral winter (July 2013), spring (October 2013), and summer (February 2014) at One Tree Reef. WorldView-2 satellite images were used to characterize and create LBF habitat maps based on ground-referenced photographs of algal cover. Habitat maps and LBF biomass measurements were combined to estimate carbonate storage across the entire reef flat. Total carbonate storage of LBFs on the reef flat ranged from 270 tonnes (winter) to 380 tonnes (summer). Satellite images indicate that the habitat area used by LBFs ranged from 0.6 (winter) to 0.71 km2 (spring) of a total possible area of 0.96 km2. LBF biomass was highest in the winter when algal habitat area was lowest, but total carbonate storage was the highest in the summer, when algal habitat area was intermediate. Our data suggest that biomass measurements alone do not capture total abundance of LBF populations (carbonate storage), as the area of available habitat is variable. These results suggest LBF carbonate production studies that measure biomass in discrete locations and single time points fail to capture accurate reef-scale production by not incorporating estimates of the associated algal habitat. Reef-scale measurements in this study can be incorporated into carbonate production models to determine the role of LBFs in sedimentary landforms (lagoons, beaches, etc.). Based on previous models of entire reef metabolism, our estimates indicate that LBFs contribute approximately 3.9–5.4% of reef carbonate budgets, a previously underappreciated carbon sink.

Changes in macrobenthic spatial structure were investigated across the precise 0.5 m wide boundary zone between intertidal seagrass and unvegetated sand in Moreton Bay, Queensland, Australia. Faunal abundance and species density in the marginal seagrass were only slightly reduced relative to local non-boundary areas. Although gradual diminution in seagrass faunal abundance occurred towards the interface and a few locally dominant species were absent from the boundary zone, most transition was far from gradual, instead being exactly coincident with the specific 0.1 m interface between the 2 habitats. Over this distance, faunal abundance and species density fell by 56 to 60% (from 1412 to 625 m-2 and from an estimated 42 species per sampling horizon to 17, respectively). Dominant seagrass species were abundant right up to the interface itself, but their densities had fallen by 82% a further 0.1 m into the adjacent sand. Functional-group density and diversity mirrored these changes, decreasing over the same distance by 30 to 36%. Spatial analysis showed that adjacent cores along lattice sampling horizons, although spaced further apart, were more similar to each other than were those oriented across horizons, even though these were contiguous. Characteristic high animal species richness in the seagrass relative to adjacent sand appears to be not so much related to characteristics of the seagrass habitat as a whole rather than to the presence or absence of individual plants. Asymmetrically, distributions of species characteristic of the sand stopped somewhat in advance of the interface, leaving a marginal sand zone dominated by generalists occurring at equal (low) species and population density across both habitats.

Linking surficial sediment patterns in reef environments to the processes that underlie their depositional dynamics enables predictions to be made of how environmental changes will influence reef-associated sedimentary landforms, such as islands and beaches. Geomorphic linkages between sediment deposition patterns and the biophysical processes that drive them are often poorly resolved, particularly at broad landscape scales where tangible statements can be made about structural changes to landforms. The present study applies geospatial techniques to link patterns in reef sediment dynamics at Lady Musgrave Island to the underlying processes driving them. In situ calcification is characterized by developing a high resolution map of the surficial calcium carbonate producing communities inhabiting the reef platform, and associated sediments across the reef flat are analysed for grain size, kurtosis, sorting and threshold bed shear stress to explore transport pathways across the reef flat and lagoon. Wave energy is modelled across the entire reef platform as a potential driver of sediment dynamics, and morphometric linkages are empirically defined between wave energy and grain size. Findings indicate that carbonate sediments are primarily sourced from calcifying communities colonizing the outer periphery of the reef platform and that sediment grain size can be reliably linked to wave energy by virtue of a linear model.

Al-Nasrawi, A.K.M.; Jones, B.G., and Hamylton, S. M., 2016. GIS-based modelling of vulnerability of coastal wetland ecosystems to environmental changes: Comerong Island, southeastern Australia. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 33–37. Coconut Creek (Florida), ISSN 0749-0208. Sustainable management of coastal zones has become a complicated issue. The majority of the human population lives along the coast, where their activities, together with a range of environmental changes, have altered the natural ecosystem processes and caused changes in coastal wetlands. To ensure sustainable use of coastal resources, a comprehensive set of modelling tools can help managers to make decisions. This study uses Comerong Island (southeastern NSW, Australia) as a case study to demonstrate the importance of modelling modifications to environme...

Adnan, F.A.F.; Hamylton, S.M., and Woodroffe, C.D., 2016. A Comparison of Shoreline Changes Estimated Using the Base of Beach and Edge of Vegetation Line at North Keeling Island. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 967 - 971. Coconut Creek (Florida), ISSN 0749-0208. The vulnerability of reef islands is often assessed by measuring changes in shoreline positions over time. Historical aerial photographs provide valuable information of past shoreline dynamics and are commonly incorporated in shoreline change assessment. Edge of vegetation line is the most common shoreline proxy adopted for assessments of reef island change because it is a visually distinguishable feature in aerial photographs, when compared to other coastal features such as high water line and base of beach. This study assesses shoreline changes of North Keeling I...

The existence of coral reefs is dependent on the production and maintenance of calcium carbonate (CaCO3) framework that is produced through calcification. The net production of CaCO3 will likely decline in the future, from both declining net calcification rates (decreasing calcification and increasing dissolution) and shifts in benthic community composition from calcifying organisms to non-calcifying organisms. Here, we present a framework for hydrochemical studies that allows both declining net calcification rates and changes in benthic community composition to be incorporated into projections of coral reef CaCO3 production. The framework involves upscaling net calcification rates for each benthic community type using mapped proportional cover of the benthic communities. This upscaling process was applied to the reef flats at One Tree and Lady Elliot reefs (Great Barrier Reef) and Shiraho Reef (Okinawa), and compared to existing data. Future CaCO3 budgets were projected for Lady Elliot Reef, predicting a decline of 53 % from the present value by end-century (800 ppm CO2) without any changes to benthic community composition. A further 5.7 % decline in net CaCO3 production is expected for each 10 % decline in calcifier cover, and net dissolution is predicted by end-century if calcifier cover drops below 18 % of the present extent. These results show the combined negative effect of both declining net calcification rates and changing benthic community composition on reefs and the importance of considering both processes for determining future reef CaCO3 production.

Changes to coral reef landscapes are driven by regional processes that are unique to particular localities, yet much of our global knowledge about how landscape changes manifest in coral reef environments is generalised from work undertaken on the Great Barrier Reef. We compare observations of 45 years of change on sand cays and mangroves associated with low wooded islands in Australia and Indonesia. We draw on field observations from ground referencing campaigns, alongside remote sensing technology, including satellite images and unmanned aerial vehicle campaigns. Four low wooded island sites are compared: two in the Great Barrier Reef (GBR), Australia (Nymph Island and Two Isles) and two in the Spermonde Archipelago, Indonesia (Sabangko and Tanakeke Island). The Spermonde and GBR sites can be distinguished in relation to the process regimes that entrain, distribute and deposit sediments on the reef surface thereby providing a substrate for further mangrove colonisation, particularly the presence or absence of cyclones as a key determinant of sediment transport. The influence of human populations inhabiting these sites is also an important control on their geomorphology. In the Spermonde Archipelago, local communities have altered sand cays through the development of infrastructure and converted mangroves to shrimp farms, while sand cays and mangroves have remained largely unaltered by humans on the GBR. This comparative evaluation of changes to sand cays and mangrove forest across low wooded islands emphasises the importance of considering changes within the context of their local geographic setting, inclusive of natural environmental and anthropogenic drivers of change.

We evaluate three approaches to mapping vegetation using images collected by an unmanned aerial vehicle (UAV) to monitor rehabilitation activities in the Five Islands Nature Reserve, Wollongong (Australia). Between April 2017 and July 2018, four aerial surveys of Big Island were undertaken to map changes to island vegetation following helicopter herbicide sprays to eradicate weeds, including the creeper Coastal Morning Glory (Ipomoea cairica) and Kikuyu Grass (Cenchrus clandestinus). The spraying was followed by a large scale planting campaign to introduce native plants, such as tussocks of Spiny-headed Mat-rush (Lomandra longifolia). Three approaches to mapping vegetation were evaluated, including: (i) a pixel-based image classification algorithm applied to the composite spectral wavebands of the images collected, (ii) manual digitisation of vegetation directly from images based on visual interpretation, and (iii) the application of a machine learning algorithm, LeNet, based on a deep learning convolutional neural network (CNN) for detecting planted Lomandra tussocks. The uncertainty of each approach was assessed via comparison against an independently collected field dataset. Each of the vegetation mapping approaches had a comparable accuracy; for a selected weed management and planting area, the overall accuracies were 82 %, 91 % and 85 % respectively for the pixel based image classification, the visual interpretation / digitisation and the CNN machine learning algorithm. At the scale of the whole island, statistically significant differences in the performance of the three approaches to mapping Lomandra plants were detected via ANOVA. The manual digitisation took a longer time to perform than others. The three approaches resulted in markedly different vegetation maps characterised by different digital data formats, which offered fundamentally different types of information on vegetation character. We draw attention to the need to consider how different digital map products will be used for vegetation management (e.g. monitoring the health individual species or a broader profile of the community). Where individual plants are to be monitored over time, a feature-based approach that represents plants as vector points is appropriate. The CNN approach emerged as a promising technique in this regard as it leveraged spatial information from the UAV images within the architecture of the learning framework by enforcing a local connectivity pattern between neurons of adjacent layers to incorporate the spatial relationships between features that comprised the shape of the Lomandra tussocks detected.

Coral reefs are consolidated calcium carbonate (CaCO3) platforms built over hundreds of thousands of years by calcifying organisms including corals, encrusting algae and invertebrates. The geomorphic integrity of coral reefs depends on the carbonate budget, which quantifies the net gain or loss of calcium carbonate, given additive and removal processes. Here, we construct three carbonate budgets for Cocos (Keeling) atoll in the East Indian Ocean from seafloor records of carbonate producers before, during and after a coral bleaching event (2015–2017). A satellite image is used to upscale 367 in-situ observations across the complete atoll (are 225 km2). Growth of calcifying encrusters is monitored on settlement plates from 2015 to 2016, while bioerosion is quantified from parrotfish surveys and macroborer analysis of rubble. The highest rates of production were on the outer atoll forereef and in the northern lagoon (1.5 and 1.61 kg m−2 yr−1 respectively). The forereef produced an order of magnitude more calcium carbonate (approximately 13,114 t per year in 2015) than the other zones due to a high coverage of live branching coral (ca 50%) combined with a large forereef area (123 km2). The greatest rates of removal occurred on the shallow forereef (−1.67 kg m−2 yr−1) driven largely by Bolbometopon muricatum parrotfish bioerosion, resulting in a net loss of carbonate in 2017 (−0.15 kg m−2 yr−1). Accounting for parrotfish bioerosion, the net atoll budget was estimated to be 5976 t of calcium carbonate in 2015, which reduced by 46% over the coral bleaching period to 3200 t in 2017. Compared to other Indian Ocean reefs, this is a relatively minor impact of coral bleaching on the carbonate budget at Cocos (Keeling) atoll.

Monitoring estuarine ecological-geomorphological dynamics has become a crucial aspect of studying the impacts of climate change and worldwide infrastructure development in coastal zones. Together, these factors have changed the natural eco-geomorphic processes that affect estuarine regimes and comprehensive modelling of coastal resources can assist managers to make appropriate decisions about their sustainable use. This study has utilised Towamba estuary (southeastern NSW, Australia), to demonstrate the value and priority of modelling estuarine dynamism as a measure of the rates and consequences of eco-geomorphic changes. This research employs several geoinformatic modelling approaches over time to investigate and assess how climate change and human activities have altered this estuarine eco-geomorphic setting. Multitemporal trend/change analysis of sediment delivery, shoreline positions and land cover, determined from fieldwork and GIS analysis of remote sensing datasets, shows significant spatio-temporal changes to the elevation and areal extent of sedimentary facies in the Towamba estuary over the past 65 years. Geomorphic growth (~ 2600 m2 annually) has stabilised the estuarine habitats, particularly within native vegetation, salt marsh and mangrove areas. Geomorphic changes have occurred because of a combination of sediment runoff from the mostly unmodified terrestrial catchment, nearshore processes (ocean dynamics) and human activities. The construction of GIS models, verified with water and sediment samples, can characterise physical processes and quantify changes within the estuarine ecosystem. Such robust models will allow resource managers to evaluate the potential effects of changes to the current coastal ecosystems.

Coastlines are dynamic environments, with their Eco-geomorphology controlled by a complex range of natural and anthropic processes. Estuarine environments and associated wetland ecosystems are a critical shoreline types with regards to biodiversity, and are particularly susceptible to the influence of sea-level rise. This project applied future sea-level rise of Intergovernmental Panel on Climate Change (IPCC) hydro-scenarios to assess its impact on the eco-geomorphic aspects of coastal ecosystems in terms of risk assessment and sustainability. Comerong Island is used as a case study and is compared with other surrounding ocean-influenced and lagoonal deltas to assess the regional effects of sea-level rise. Applying the IPCC scenarios to the chosen geomorphic coastal data-sets resulted in a hydro-geomorphic model that shows the study site was already under pressure in 2015, with significant land area projected to be lost by 2050 and 2100. These findings are also expected to occur across the remaining estuaries in southeastern Australia. Applying this broad-scale, multi-strand application of geoinformatics simulation (GIS & RS), together with the various IPCC sea-level rise scenarios, will be necessary to assess future ecosystem sustainability management plans for coastal zones worldwide.

Balls Pyramid is the southernmost island in a linear island chain in the southwest Pacific Ocean, 24 km south of the limit of known coral reef formation at Lord Howe Island. This paper describes the geomorphometric structure of the shelf surrounding Balls Pyramid through the application of remote sensing data to create a high-resolution digital elevation model of the shelf (5 m cell size) and seafloor feature classification. Seafloor features were delineated using the bathymetry model together with slope, backscatter and sub-bottom profile data. The average depth of the 260.6 km2 shelf was 55 m (± 21 m), with the majority of shelf area (77%) within 30–60 m water depth. Dominating the shelf is an extensive, mid-shelf reef at 30–50 m depth, dissected by basin and channel features. Outer-shelf reef and platform features surround the mid shelf, with terrace sequences marking the seaward outer-shelf rim in 65–100 m depth. Sub-bottom profiles and backscatter data demonstrate substantial accumulation (up to 16.5 m) of unconsolidated sediments within basin and channel features. The submerged mid-shelf reefs of Balls Pyramid are similar to the fossil coral reef system discovered on the Lord Howe Island shelf, implying origins as a drowned coral reef system. This paper reveals complex shelf topography with extensive submerged reefs on what was previously considered to be a planated volcanic shelf outside of reef-forming seas.

Reef islands on the Great Barrier Reef are influenced by a range of environmental factors. A meta-analysis of 103 islands is presented to express variation in island size (area and volume) as a function of latitudinal and cross shelf gradients in regional oceanographic factors (exposure to incident waves, tidal range and tropical cyclone frequency) and local physical factors (position on the shelf, area, length and depth of supporting reef platform, vegetative cover). Models performed well for unvegetated sandcays (R2 = 0.89), vegetated sandcays (R2 = 0·72) and low wooded islands (R2 = 0.78), with a moderate level of variation explained when all islands were simultaneously regressed (R2 = 0.58). Future island dynamics were simulated for anticipated changes in cyclone regime, wave activity and sea level. For 38 islands mapped on the 1973 Royal Society and Universities of Queensland Expedition to the Northern Great Barrier Reef, change over the same 22 year period (1973–1995) was determined and the relative magnitude of observed and modelled changes was compared and found to be consistent through rank correlation analysis (Γ = 0.84 for unvegetated sandcays, Γ = 0.81 for vegetated sandcays). Simulations of island area or volume change from 2000 to 2100 indicated that under a 30% decrease in tropical cyclone activity, unvegetated sandcays continue to accrete at a lower rate, whereas all island types erode under a 38% increase in tropical cyclone activity. Vegetated sandcays initially accrete at higher levels of cyclone activity, entering an erosive state with a 60% increase in activity. Low wooded islands are unresponsive to environmental changes modelled. A sensitivity analysis of vegetated and unvegetated sandcays indicated that the presence of vegetation increases the tropical cyclone activity threshold at which islands begin to erode. Greatest sedimentary losses occur within the central band of high cyclone activity between Cooktown and Mackay. Copyright © 2015 John Wiley & Sons, Ltd.

Large numbers of people live along and depend upon the world’s coastal resources. Human modifications of the coastal zone, in combination with climate induced environmental changes, have had a major effect on the natural ecological systems. GIS analysis of remote sensed data, combined with fieldwork and laboratory tests, can be used to determine the resultant eco-geomorphic changes that need to be managed sustainably on a worldwide scale. Modelling the eco-geomorphic dynamics between 1949 and 2016 on the Wandandian Creek delta (southeastern NSW, Australia) provides a case study of management options for such coastal resources. Results from the Wandandian Creek delta show that sand/silt sediment derived from the partially (22%) modified terrestrial catchment has prograded into the wave-dominated St. Georges Basin where it is impacted by nearshore processes. Clear spatio-temporal growth of the areal extent and elevation of the deltaic levees and sandspits, with their associated mangroves and saltmarshes, has occurred over the past 65 years. Although the growth rate has fluctuated during the study period, due to flood events in 1974, 1990s and 2010, the overall subaerial and subaqueous delta area has had an average growth of 4168 m2 annually with the shoreline extending 1.451 m/year on average. This geomorphic growth has stabilised the estuarine deltaic habitats with high proportions of nutrients and organic matter, particularly within saltmarsh, mangrove, Casuarina/Juncus and other mixed native plant areas. This research shows the importance of analysing morphological changes observed on the delta that can be related to both anthropogenic modifications and natural processes to the catchment and thus should be used in the development of catchment and coastal management plans.

This study applies different techniques, such as single and multibeam bathymetry, sidescan sonar, terrestrial LiDAR, RTK-GPS, underwater drop camera and bathymetry derived from WorldView-2 optical imagery, to map the ‘white ribbon’, a term first coined by the British Geological Survey which refers to the terrestrial-marine interface known for the lack of data and hydrographic challenges associated with it. The ‘white ribbon’ area is of extreme importance for coastal managers, scientists and engineers interested in sediment dynamics, volume estimates and coastal connectivity. The ‘white ribbon’, or the interface area formed by the intertidal and nearshore zones, is generally too shallow and dangerous for most traditional bathymetric survey vessels, due to rocks, reefs and waves, and too deep for land-based survey methods. Herein, we present the integration of data collected by multiple Australian organisations (University of Wollongong, Geoscience Australia, NSW Office of Environment and Heritage, and NSW Land and Property Information) into seamless digital elevation models for three sites (Beecroft Peninsula, Gerroa and Five Islands) on the South Coast of NSW. Two major challenges were associated with this study: the use of a small aluminium vessel to collect singlebeam bathymetry in shallow water, and the integration of the Australian Height Datum (AHD) and the Chart Datum. Research findings were particularly relevant for understanding of sediment mobility between different coastal compartments, mapping of geomorphic features, underwater extension of headlands, unconsolidated and consolidated substrates, and different rock reef habitats.

Measurements of community calcification ( G net ) were made during September 2008 and October 2009 on a reef flat in Lizard Island, Great Barrier Reef, Australia, 33 years after the first measurements were made there by the LIMER expedition in 1975. In 2008 and 2009 we measured G net = 61 ± 12 and 54 ± 13 mmol CaCO 3 m −2 ·day −1 , respectively. These rates are 27–49% lower than those measured during the same season in 1975–76. These rates agree well with those estimated from the measured temperature and degree of aragonite saturation using a reef calcification rate equation developed from observations in a Red Sea coral reef. Community structure surveys across the Lizard Island reef flat during our study using the same methods employed in 1978 showed that live coral coverage had not changed significantly (∼8%). However, it should be noted that the uncertainty in the live coral coverage estimates in this study and in 1978 were fairly large and inherent to this methodology. Using the reef calcification rate equation while assuming that seawater above the reef was at equilibrium with atmospheric PCO 2 and given that live coral cover had not changed G net should have declined by 30 ± 8% since the LIMER study as indeed observed. We note, however, that the error in estimated G net decrease relative to the 1970’s could be much larger due to the uncertainties in the coral coverage measurements. Nonetheless, the similarity between the predicted and the measured decrease in G net suggests that ocean acidification may be the primary cause for the lower CaCO 3 precipitation rate on the Lizard Island reef flat.

Linkages between neighbouring ecosystems are rarely considered when seeking to predict ecological responses to climate change. However, the finding that the impact of climate change on seagrass beds is mediated by the response of neighbouring coral reef habitats highlights the need for a broader-scale view of climate change impacts on ecosystems.

Duce, S., Vila-Concejo, A., Hamylton, S., Bruce, E., Webster, J. M, 2014. Spur and groove distribution, morphology and relationship to relative wave exposure, Southern Great Barrier Reef, Australia. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13 th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 115-120, ISSN 0749-0208. Spur and groove features occur on the seaward reef slope of coral reefs around the world. They are believed to act as important natural breakwaters, regulating the hydrodynamic energy and nutrients received by reef platforms. They also represent one of the most diverse and productive zones of modern reefs. However, the formation processes and morphodynamics of spur and groove systems are poorly understood, particularly in the Great Barrier Reef (GBR). This paper constitutes the first broad scale analysis of spur and groove systems in the Capricorn Bunker Group (CBG) in the southern GBR. It uses remotely sensed imagery coupled with ground-truthed data to measure groove length at four reefs (Wreck, Heron, One Tree and Lady Elliot). A total of 2621 grooves were digitised across the four study reefs. Groove length was found to vary both between and within the study reefs. The maximum groove length was 536 m. Average groove length ranged from 93 m at Wreck Reef to 32 m at Heron Reef. This data was compared to relative wave exposure estimates derived from the fetch scenario at each reef. Strong positive correlation was found with groove length increasing as wave exposure increased. Groove length was highly spatially dependant and varied around the reef platforms according to the degree of wave exposure. The longest grooves were found on the most exposed, eastern sides of all reefs. These results provide valuable insight into spur and groove function, formation and likely response to future environmental changes in the CBG and further afield.

The nature of the transition from one contrasting macrobenthic assemblage to another across interfaces between intertidal seagrass and unvegetated sand was investigated in the subtropical Moreton Bay Marine Park, eastern Australia, via six two-dimensional core lattices. The same pattern of transition was manifested in each lattice. Macrofaunal abundance, species density (both observed and estimated total) and assemblage composition did not vary with distance away from the interface within the 0.75 m wide marginal bands of each habitat type. Neither were there significant differences in assemblage metrics or composition between the marginal and non-edge regions of either habitat. There were, however, very marked differences in assemblage composition, abundance and species density across the 25 cm wide strip on either side of the actual interface, the interacting assemblages reacting symmetrically. All these differences therefore took place over an ecotone distance of only 0.5 m at most. Spatial trends in assemblage metrics across the boundary zone were captured accurately by second and third order polynomial regression models. It also appeared that edge effects on individual species within the seagrass were a variable local response not a consistent effect of closeness to the bare sand.

Maps exert power. In this paper I explore the power of maps in relation to the technical methods employed and the political context of their production. The internal power of maps is realised in the actions taken by cartographers themselves when making maps, while the external power of maps is both realised by the patrons of cartography and wielded through the use of cartographic products as agents for natural resource management, in particular for defining conservation strategies. An Australian case study of coastal mapping is used to examine the methods employed and motivation behind map production through a series of recent remote sensing initiatives to map Lord Howe Island, New South Wales. Through this case study I explore the subjectivities associated with the placement of boundaries in the scientific practice of cartography. I argue that a new epistemological reading of maps is necessary, as sources of information on socio-politically constructed worlds as much as the phenomenological world of objects. Such a reading is particularly important given recent advances in technologies, such as remote sensing, that are increasingly used to inform coastal management, and which propagate in profound new ways the power of maps.

Hydrographers have traditionally referred to the nearshore area as the ‘white ribbon’ area due to the challenges associated with the collection of elevation data elevation hereafter refers to both topography and bathymetry in this highly dynamic transitional zone between terrestrial and marine environments. Accordingly, available information in this zone is typically characterized by a range of data sets from disparate sources. In this article, we propose a framework to fill the white ribbon area of a coral reef system by integrating multiple elevation data sets acquired by a suite of remote-sensing technologies into a seamless digital elevation model DEM. A range of data sets are integrated, including field-collected global positioning system GPS elevation points, topographic and bathymetric light detecting and ranging lidar, single and multibeam echosoundings, nautical charts, and bathymetry derived from optical remote-sensing imagery. The proposed framework ranks data reliability internally, thereby avoiding the requirements to quantify absolute error and results in a high-resolution, seamless product. Nested within this approach is an effective spatially explicit technique for improving the accuracy of bathymetry estimates derived empirically from optical satellite imagery through modelling the spatial structure of residuals. The approach was applied to data collected on and around Lizard Island in northern Australia. Collectively, the framework holds promise for filling the white ribbon zone in coastal areas characterized by similar data availability scenarios.

The present study uses remote-sensing imagery to estimate carbonate production of the complete One Tree Island reef system, Great Barrier Reef, using hydrochemical alkalinity reduction and census-based budgetary methods. For five sites representing different benthic cover types across the reef system, carbonate production is determined using hydrochemical techniques that incubate substrates in a local aquarium and measure total alkalinity, total ammonia nitrogen, and total oxidized nitrogen. Local estimates are scaled up to the reef-system scale using a WorldView-2 satellite image, which is ground truthed against a field data set of 350 spatially referenced records of benthic assemblage. Annual total reef system carbonate production based on hydrochemical and census-based methods is estimated at 40,335 and 38,998 tonnes of calcium carbonate CaCO3, respectively. The minimal difference 0.3% between these estimates is attributed to under representation of small carbonate producers, such as benthic foraminifera, which are difficult to incorporate in the underwater video methodology employed to populate census budgets. This finding demonstrates the utility of remote sensing for upscaling local measures of carbonate production across reef systems accurately and consistently in spite of the use of different initial estimation methods.