Megan J. Huggett

With multiple Declared Areas nationally, offshore wind energy is poised to expand within Australia’s iconic coastal and marine environments. We argue that the central obstacle to credible environmental assessment of offshore wind is not a shortfall of effort or rigour within individual assessments, but a structural feature of how assessment is legally constituted. Australia’s principal national environmental law, the Environment Protection and Biodiversity Conservation Act 1999, protects species across their distribution, yet project-level assessments investigate impact only within or near a development’s footprint. We identify four structural problems, namely unmanaged cumulative impacts, mismatched regulatory and ecological scales, an incomplete species list, and a causal-evidence gap that project-level assessment cannot close, which limit our capacity to detect and attribute development impacts on far-ranging, long-lived marine mammals, birds, and sharks, charismatic species whose life histories make them particularly sensitive to reductions in survival and reproductive success. We recommend addressing these shortfalls through a coordinated, independent, and openly accessible national program of marine and coastal biodiversity science, funded through a pooled industry levy rather than project-by-project commissioning, and coupled to strategic environmental assessment. Australia’s offshore wind sector is at an early enough stage to build this architecture from the outset, so that renewable development and environmental stewardship advance together rather than in tension. Done well, this might help build public trust in offshore wind domestically and position Australia as a leader in international best practice in offshore environmental research and monitoring, offering a model for nations whose offshore wind sectors are emerging.

The influence of fishes on temperate rocky reef ecosystems is globally recognised, particularly where large predators may structure ecosystems through predation. In South-East Australia, the common Wrasse Achoerodus viridis (Blue Groper) and Sparid Chrysophrys auratus (Snapper) are sympatric rocky reef predators. While their diets are thought to be well understood, this is generally based on gut contents undertaken over limited spatial scales. Stable isotope approaches can provide a time-integrated dietary history. We used Bayesian mixing models (δ¹³C and δ¹⁵N) to examine diets of 45 Blue Groper and 73 Snapper collected across > 1,250 km of coastline. We found that both predators consume filter-feeders likely including mussels, oysters or serpulid polychaete worms based on previous gut contents, shifting to consuming omnivores such as crabs or the problematic sea urchin Centrostephanus rodgersii , and carnivores such as cephalopods, predatory fishes or nereidid polychaetes when large (> 400 mm TL). However, ontogenetic shifts differed, with Blue Groper relying primarily on filter-feeders at all sizes and carnivores/omnivores becoming equally important when large. By contrast, small Snapper relied both on filter-feeders and omnivores/carnivores, relying on omnivores/carnivores when large. Trends varied spatially for Blue Groper more than Snapper, with Blue Groper relying on carnivores/omnivores in the north and filter-feeders in the south, while Snapper relied primarily on carnivores/omnivores throughout. These results highlight species-specific trophic pathways, indicating that these predators ecological role differs markedly throughout their ontogeny. Key to ecological structuring processes affecting temperate rocky reefs, our results suggest large Snapper may impact C. rodgersii populations more than Blue Groper.

Urchin diets are a topic of global interest due to their impacts on subtidal reefs. Urchins can consume large amounts of macroalgae, leading to the loss of macroalgal forests and creation of “barrens”. However, there is scant dietary information in the southern hemisphere for the temperate sea urchin, Centrostephanus rodgersii , and what they consume within barrens, which lack macroalgae. Here, we sampled C. rodgersii to quantify its nutritional sources in macroalgal forests and barrens along ~ 630 km of the SE Australian coastline. Urchins were collected from macroalgal forests and barrens and the stable isotope values (δ ¹³ C, δ ¹⁵ N, δ ³⁴ S) of urchin muscle tissues were analysed. Using Bayesian stable isotope mixing models, we found macroalgae contributed to nutrition in both habitats (~ 30%). However, grouped sources containing invertebrates contributed more to urchin diets in both barrens (> 50%) and macroalgal forests (> 60%). Composition changed with habitats – crustaceans or similar invertebrates were the dominant source in barrens while a more diverse invertebrate array was relied upon in macroalgal forests. However, proportional contributions differed along the coast more than between habitats within locations. These data provide new context for C. rodgersii , as these urchins are not primarily herbivorous. Furthermore, this study indicates that conceptual models for barrens in SE Australia are more complicated than previously considered, as C. rodgersii were omnivorous irrespective of habitat. This could suggest the core C. rodgersii diet is invertebrates rather than macroalgae, raising questions about their perceived ecological role.

Growth anomalies (GAs) are coral diseases characterised by tumour‐like skeletal lesions reported globally, yet their causes remain poorly understood. Microorganisms are integral to coral health, but the role of bacterial communities in GAs remains unclear. We investigated an outbreak of GAs in Isopora palifera at the Cocos (Keeling) Islands using 16S rRNA amplicon sequencing to compare bacterial communities of GA‐affected and asymptomatic corals, surrounding water and potential pollution sources. Significant differences in bacterial beta diversity were observed across sites, with an interaction between location and coral health status. Coral and water samples hosted distinct microbial communities, but there was no evidence linking GA‐affected corals to local pollution. Moreover, no consistent bacterial taxa were associated with disease, suggesting that resident microbes may not be primary drivers of GAs. However, our study does not account for transient microbes that may have initiated GAs. Our findings challenge assumptions of single‐agent causality and microbial compositional homogeneity in coral diseases. This study advances understanding of microbial dynamics in coral disease ecology and underscores the importance of early‐stage investigation and functional metagenomics to identify viral, fungal and microbial functional shifts in disease emergence. Studying outbreaks in minimally impacted systems offers valuable baselines for disentangling natural disease processes.

A major goal of microbial ecology is to establish the importance of spatial and environmental factors in driving community variation. Their relative importance likely varies across spatial scales, but focus has primarily been on free-living communities within well-connected aquatic environments rather than less connected island-like habitats such as estuaries, and key host-associated communities within these systems. Here we sampled both free-living (seawater and sediment) and host-associated (estuarine fish hindgut microbiome, Pelates sexlineatus) communities across six temperate Australian estuaries spanning ∼500 km. We find that spatial and environmental factors have different influences on these communities, with seawater demonstrating strong distance-decay relationships (R = −0.69) and significant associations with a range of environmental variables. Distance-decay relationships were weak for sediment communities but became stronger over smaller spatial scales (within estuaries, R = −0.5), potentially reflecting environmental filtering across biogeochemical gradients or stochastic processes within estuary sediments. Finally, P. sexlineatus hindgut microbiome communities displayed weak distance-decay relationships (R = −0.36), and limited variation explained by environmental variables, indicating the significance of host-related factors in driving community variation. Our findings provide important ecological insights into the spatial distributions and driving forces of both free-living and host-associated bacterial patterns across temperate estuarine systems.

Hybridisation and introgression of eukaryotic genomes can generate new species or subsume existing ones, with direct and indirect consequences for biodiversity. An understudied component of these evolutionary forces is their potentially rapid effect on host gut microbiomes, and whether these pliable microcosms may serve as early biological indicators of speciation. We address this hypothesis in a field study of angelfishes (genusCentropyge), which have one of the highest prevalence of hybridisation within coral reef fish. In our study region of the Eastern Indian Ocean, the parent fish species and their hybrids cohabit and display no differences in their diet, behaviour, and reproduction, often interbreeding in mixed harems. Despite this ecological overlap, we show that microbiomes of the parent species are significantly different from each other in form and function based on total community composition, supporting the division of parents into distinct species, despite the confounding effects of introgression acting to homogenize parent species identity at other molecular markers. The microbiome of hybrid individuals, on the other hand, are not significantly different to each of the parents, instead harbouring an intermediate community composition. These findings suggest that shifts in gut microbiomes may be an early indicator of speciation in hybridising species.