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Genomic vulnerability analyses are being increasingly used to assess the adaptability of species to climate change and provide an opportunity for proactive management of harvested marine species in changing oceans. Southeastern Australia is a climate change hotspot where many marine species are shifting poleward. The turban snail, Turbo militaris is a commercially and culturally harvested marine gastropod snail from eastern Australia. The species has exhibited a climate-driven poleward range shift over the last two decades presenting an ongoing challenge for sustainable fisheries management. We investigate the impact of future climate change on T. militaris using genotype-by-sequencing to project patterns of gene flow and local adaptation across its range under climate change scenarios. A single admixed, and potentially panmictic, demographic unit was revealed with no evidence of genetic subdivision across the species range. Significant genotype associations with heterogeneous habitat features were observed, including associations with sea surface temperature, ocean currents, and nutrients, indicating possible adaptive genetic differentiation. These findings suggest that standing genetic variation may be available for selection to counter future environmental change, assisted by widespread gene flow, high fecundity and short generation time in this species. We discuss the findings of this study in the content of future fisheries management and conservation., Competing Interests: The authors declare that they have no competing interests. Stephen D. A. Smith is employed by Aquamarine Australia., (© 2023 Nimbs et al.)

Environmental anomalies that trigger adverse physiological responses and mortality are occurring with increasing frequency due to climate change. At species' range peripheries, environmental anomalies are particularly concerning because species often exist at their environmental tolerance limits and may not be able to migrate to escape unfavourable conditions. Here, we investigated the bleaching response and mortality of 14 coral genera across high‐latitude eastern Australia during a global heat stress event in 2016. We evaluated whether the severity of assemblage‐scale and genus‐level bleaching responses was associated with cumulative heat stress and/or local environmental history, including long‐term mean temperatures during the hottest month of each year (SSTLTMAX), and annual fluctuations in water temperature (SSTVAR) and solar irradiance (PARZVAR). The most severely‐bleached genera included species that were either endemic to the region (Pocillopora aliciae) or rare in the tropics (e.g. Porites heronensis). Pocillopora spp., in particular, showed high rates of immediate mortality. Bleaching severity of Pocillopora was high where SSTLTMAX was low or PARZVAR was high, whereas bleaching severity of Porites was directly associated with cumulative heat stress. While many tropical Acropora species are extremely vulnerable to bleaching, the Acropora species common at high latitudes, such as A. glauca and A. solitaryensis, showed little incidence of bleaching and immediate mortality. Two other regionally‐abundant genera, Goniastrea and Turbinaria, were also largely unaffected by the thermal anomaly. The severity of assemblage‐scale bleaching responses was poorly explained by the environmental parameters we examined. Instead, the severity of assemblage‐scale bleaching was associated with local differences in species abundance and taxon‐specific bleaching responses. The marked taxonomic disparity in bleaching severity, coupled with high mortality of high‐latitude endemics, point to climate‐driven simplification of assemblage structures and progressive homogenisation of reef functions at these high‐latitude locations. [ABSTRACT FROM AUTHOR]

Abstract Spatial conservation plans representing existing patterns of biodiversity in Marine Protected Areas (MPAs) should be robust to changes over 10 to 20 years, a temporal scale over which MPA plans are often retained. Using data from MPAs where changes have been detected due to ocean warming, can help inform discussion on how to increase temporal robustness in planning. Our aim was to determine how well fish assemblage patterns, used to develop a Habitat Classification System (HCS) as a coarse biodiversity surrogate in MPA planning, persisted over a 16 year timeframe in a warming region (east coast subtropics) of Australia. We analysed persistence/change in fish assemblage patterns in the Solitary Islands Marine Park (SIMP) where species shifts and habitat changes associated with ocean warming have been detected. Fish relative abundance was recorded at 12 sites over 16 years (2001–2017) using roving timed counts. Strong cross-shelf patterns were maintained over that 16 year period, which included some large-scale disturbances (destructive storms, 2016 mass coral bleaching event). Overall persistence in these broad assemblage patterns suggest a well-designed HCS can be a robust tool for coarsely representing biodiversity patterns in a warming world at decadal scales. 'Tropicalisation' was detected in some categories, suggesting additional planning strategies are needed within those and beyond decadal plans. Graphical abstract Unlabelled Image Highlights • Strong but coarse cross-shelf fish assemblage patterns persisted over 16 years • This supports continued use of a habitat classification system (HCS) for spatially planning biodiversity representation • Finer-scale 'tropicalisation' changes in some HCS categories require additional complimentary planning strategies [ABSTRACT FROM AUTHOR]

Species distributions at range edges show complex shifts with climate change. The present study examined anemonefish and host sea anemone abundance at their southern distribution limits on the eastern coast of Australia, to identify factors influencing the geographic responses of the symbiosis. Roaming surveys (30 min) were conducted at 21 sites (~30.01-30.95°S) on rocky reefs in a tropical-temperate transition zone. Two species of host anemones (Entacmaea quadricolor and Heteractis crispa) and anemonefishes (Amphiprion akindynos and A. latezonatus) were found, along with Dascyllus trimaculatus. Nearly all anemones and anemonefishes (.99.5%) were associated with vegetated islands and rocky islets, and abundance was influenced by seawater temperature. Greater numbers of H. crispa and A. akindynos than E. quadricolor and A. latezonatus were found; however, most A. akindynos were juveniles. H. crispa provided nursery habitat for both fishes, whereas adult fishes utilised only E. quadricolor. A southern range extension was found for E. quadricolor, and overwintering of A. latezonatus had extended poleward since the mid-1990s. The paucity of islands and rocky islets south of our surveys, and host-usage patterns, could constrain future range extensions. These findings showed climate-driven latitudinal shifts are complex and are likely to be variably constrained for different species. [ABSTRACT FROM AUTHOR]

Some of the most profound effects of climate change on ecological communities are due to alterations in species interactions rather than direct physiological effects of changing environmental conditions. Empirical evidence of historical changes in species interactions within climate-impacted communities is, however, rare and difficult to obtain. Here, we demonstrate the recent disappearance of key habitat-forming kelp forests from a warming tropical--temperate transition zone in eastern Australia. Using a 10-y video dataset encompassing a 0.6 °C warming period, we show how herbivory increased as kelp gradually declined and then disappeared. Concurrently, fish communities from sites where kelp was originally abundant but subsequently disappeared became increasingly dominated by tropical herbivores. Feeding assays identified two key tropical/ subtropical herbivores that consumed transplanted kelp within hours at these sites. There was also a distinct increase in the abundance of fishes that consume epilithic algae, and much higher bite rates by this group at sites without kelp, suggesting a key role for these fishes in maintaining reefs in kelp-free states by removing kelp recruits. Changes in kelp abundance showed no direct relationship to seawater temperatures over the decade and were also unrelated to other measured abiotic factors (nutrients and storms). Our results show that warming-mediated increases in fish herbivory pose a significant threat to kelp-dominated ecosystems in Australia and, potentially, globally. [ABSTRACT FROM AUTHOR]

This paper reports on a workshop conducted in Australia in 2010, entitled 'Management, Conservation, and Scientific Challenges on Subtropical Reefs under Climate Change'. The workshop brought together 26 experts actively involved in the science and management of subtropical reefs. Its primary aim was to identify the areas of research that need to be most urgently addressed to improve the decision-making framework for managers of subtropical reefs. The main findings of the workshop were a sustainable subtropical reefs declaration that highlights seven research priorities for subtropical reefs. These are to (i) conduct research and management activities across local government, state and bioregion borders; (ii) understand natural variability of environmental conditions; (iii) quantify socio-economic factors and ecosystem services; (iv) benchmark cross-realm connectivity; (v) know marine population connectivity; (vi) habitat mapping and ecological research; and (v) determine refugia. These findings are hoped to form a basis for focussing research efforts, leveraging funds and assisting managers with allocation of resources. [ABSTRACT FROM AUTHOR]

Climate change is modifying marine species' distribution with consequences for the structure and function of ecosystems. The warming and strengthening East Australian Current (EAC) is driving the tropicalisation of subtropical marine ecosystems through changing overwinter survival of tropical species. However, this can be complex for obligate symbionts, such as anemonefishes. Here, we documented fine-scale temporal changes in the density of anemonefishes and assessed the influence of latitude, temperature, and host sea anemone availability. Juvenile, subadult and adult Amphiprion akindynos and A mphiprion latezonatus occurred at all study locations: North Solitary Island (equatorward), South Solitary Island, and Fish Rock (poleward). While the sea anemone Heteractis crispa was readily available at Fish Rock, we found that a lack of another sea anemone Entacmaea quadricolor hindered the establishment of adult A. akindynos and A. latezonatus populations. Minimum water temperature was also a bottleneck for the tropical anemonefish A. akindynos but not for the subtropical A. latezonatus. Our findings suggest anemonefishes are capable of contributing to the tropicalisation of the east coast of Australia. However, poleward establishment is currently limited by the absence of the preferred host sea anemone. [Display omitted] • Anemonefishes are experiencing climate change on the east coast of Australia. • These fishes are in the arrival stage of a southern range expansion at Fish Rock. • Establishment is habitat limited for Amphiprion akindynos and A. latezonatus. • Minimum temperature and overwintering are also bottlenecks for A. akindynos. • Ocean warming may lead to establishment and tropicalisation if habitat is available. [ABSTRACT FROM AUTHOR]