Neville Scott Barrett

Reliable predictions of species responses to intensifying temperature extremes are crucial for managing climate change impacts. However, limited data of species' responses to heat stress across their distribution restricts prediction accuracy. Here we analyse three‐decades of kelp abundance observations in Australia, including cool to warm‐edge populations, relative to marine heatwaves (MHWs). As MHWs intensified, changes in kelp abundances shifted from positive to negative. Warm‐edge populations displayed steeper declines in abundance change than central and cool‐edge populations under comparable MHWs. Our results support a hybrid thermal performance model, whereby thermal limits differ between populations, but performance volatility increases toward species' warm‐edge, heightening vulnerability of warm‐edge populations. Importantly, realised impacts of MHWs were evident at smaller thermal anomalies than predicted by experiments and distribution models, highlighting the importance of calibrating theoretical approaches with realised ecological change. By integrating a multi‐faceted approach, our study is generalisable for improving predictions of species' population vulnerability.

Most platforms for collecting images to characterise marine benthic habitats involve a downward or forward‐facing field of view that is relatively constrained (~70°), covering a relatively small area of benthos (downward ~1 m², forward ~25 m²). Here we propose the use of a four‐camera platform having a wide combined field of view (~280°), covering a much greater area (up to 100 m²). We also present a stereo‐camera configuration that has the added benefit of being able to accurately measure sample area and dimensions of benthic biota. The design proposed is robust and self‐righting, facilitating rapid deployment and retrieval from a range of vessels, depths and environments. We present an exemplar workflow to generate a habitat map (~100 km²) within a no‐take National Park Zone within the South‐west Corner Marine Park, Australia and demonstrate the benefit of increasing the field of view to estimate habitat heterogeneity. The relatively broad sample unit of this wide‐field drop camera is well suited to estimating coverage (e.g. of a seagrass bed) and habitat mapping. It is time‐efficient in the field, enabling spatially balanced sampling designs to acquire ground‐truthing data for medium‐ to large‐scale habitat mapping projects. This platform is a practical tool to monitor change in marine environments and assess the environmental impact (e.g. sea bed alteration) of activities such as offshore energy or fishing gears.

Marine protected areas (MPAs) are an important tool in helping to protect biodiversity in the oceans. Recent ratification of the Kunming-Montreal Global Biodiversity Framework (GBF) has ensured that globally we are committed to effectively protecting 30% of the world’s oceans by 2030, in MPAs. In Australia there is considerable interest in the potential benefits that partially protected areas (PPAs) may provide. However, a consistent definition of a PPA is currently lacking, and urgently needed to conduct quantitative analyses of PPAs. We conducted a systematic literature review to understand the current knowledge surrounding PPAs and their potential benefits. We define a PPA, characterise PPA implementation in Australia, and present results for the outcomes of PPAs in terms of ecological, economic, and social indicators. Our review suggests that although 45% of Australia’s marine environment is within MPAs, 61% of MPAs provide only partial protection. The Northern Territory (100%), New South Wales (81%), and Queensland (79.8%) have the highest percentage of MPAs that are partially protected, compared to Tasmania which has the smallest percentage of partially protected MPAs (13.12%). Tasmania also has the smallest percentage cover of MPAs (6.49% state waters). Most PPA management plans did not contain quantifiable Key Performance Indicators (KPIs) to be able to effectively monitor the progress of these PPAs against the stated outcomes. We find the benefits of PPAs to be ambiguous: PPAs generally provide benefits when compared to ‘open’ ocean, however this is not a consistent result. There are no PPAs that provide greater overall benefits when compared to fully protected MPAs. Only one state (South Australia) and the Commonwealth (Australian Marine Parks) are collecting publicly available baseline data to facilitate quantitative monitoring of PPAs. Contrary to fisheries management, there were no plans of action if the declared MPAs and PPAs failed to meet their declared objectives and goals. Some PPAs within Australia appear to be incompatible with conservation priorities according to the recent “MPA Guide” classification framework. This study highlights the need for clearer management rationale and plans for PPAs in Australia, as these comprise the majority of MPAs in Australia’s Exclusive Economic Zone.

Protection from direct human impacts can safeguard marine life, yet ocean warming crosses marine protected area boundaries. Here, we test whether protection offers resilience to marine heatwaves from local to network scales. We examine 71,269 timeseries of population abundances for 2269 reef fish species surveyed in 357 protected versus 747 open sites worldwide. We quantify the stability of reef fish abundance from populations to metacommunities, considering responses of species and functional diversity including thermal affinity of different trophic groups. Overall, protection mitigates adverse effects of marine heatwaves on fish abundance, community stability, asynchronous fluctuations and functional richness. We find that local stability is positively related to distance from centers of high human density only in protected areas. We provide evidence that networks of protected areas have persistent reef fish communities in warming oceans by maintaining large populations and promoting stability at different levels of biological organization.

Quantification of species’ spatial distributions and population trends is crucial for successful conservation efforts. Obtaining sufficient population data, however, is often difficult in the marine environment, especially for rare fish and invertebrate species that are small, cryptic and very difficult to detect. This study sought to understand the effort required to search for undiscovered populations of small, cryptic, marine species in shallow vegetated coastal habitats and track population numbers, using the Critically Endangered red handfish (Thymichthys politus) as a representative species. A sampling strategy was designed using a combination of environmental DNA (eDNA) and structured underwater scuba surveys of life‐like 3D‐printed ‘handfish replicas’ to estimate detectability and ultimately determine whether current population monitoring is adequately covering the remaining habitat occupied by the species. Tested over scales of hundreds of metres to kilometres, the eDNA assays performed relatively poorly in situ, detecting red handfish presence in only ~13% of samples collected from the centre of a known, yet low‐density, red handfish site. In contrast, underwater searches for independently placed handfish replicas by scuba divers indicated that mean detection probabilities at finer scales (~100 m) ranged from 57 to 97%. Near certain (95% probability) detection of an adult handfish was achievable with only one to three surveys (300 m² belt transects), depending on the habitat complexity. While other species will vary in detectability using eDNA and underwater searches, these findings give insight into the general effort required for the detection of small, rare species inhabiting vegetated coastal environments. Such knowledge not only helps to refine monitoring and conservation efforts for known threatened species, but may also assist in identifying other inconspicuous species whose population declines may otherwise go unnoticed.

Human society is dependent on nature^1,2, but whether our ecological foundations are at risk remains unknown in the absence of systematic monitoring of species’ populations³. Knowledge of species fluctuations is particularly inadequate in the marine realm⁴. Here we assess the population trends of 1,057 common shallow reef species from multiple phyla at 1,636 sites around Australia over the past decade. Most populations decreased over this period, including many tropical fishes, temperate invertebrates (particularly echinoderms) and southwestern Australian macroalgae, whereas coral populations remained relatively stable. Population declines typically followed heatwave years, when local water temperatures were more than 0.5 °C above temperatures in 2008. Following heatwaves^5,6, species abundances generally tended to decline near warm range edges, and increase near cool range edges. More than 30% of shallow invertebrate species in cool latitudes exhibited high extinction risk, with rapidly declining populations trapped by deep ocean barriers, preventing poleward retreat as temperatures rise. Greater conservation effort is needed to safeguard temperate marine ecosystems, which are disproportionately threatened and include species with deep evolutionary roots. Fundamental among such efforts, and broader societal needs to efficiently adapt to interacting anthropogenic and natural pressures, is greatly expanded monitoring of species’ population trends^7,8.

Many temperate reefs are experiencing a shift towards a greater abundance of tropical species in response to marine heatwaves and long-term ocean warming worldwide. Baseline data for coral communities growing in high-latitude reefs is required to better understand ecosystem changes over time. In this study, we explore spatial and temporal trends in the distribution of coral communities from 1999 to 2019 at 118 reef sites within the five marine parks located in the south-west of Western Australia (WA) between 30° to 35° S. Our estimates of coral cover were generally low (Turbinaria spp. at Marmion Marine Park and Ngari Capes Marine Park, and Pocillopora spp. and Dipsastraea spp. at Rottnest Island and Jurien Bay. Our findings suggest that conditions in south-west WA are favorable to the ongoing survival of existing genera and there were minimal signs of expansion in coral cover at most study sites. Coral cover and composition on these reefs may, however, change with ongoing ocean warming and increased occurrence of marine heatwaves. This study provides a valuable benchmark for assessing future changes in coral assemblages and highlights the need for targeted hard-coral surveys to quantify subtle changes in high-latitude coral community assemblages.

The redistribution of marine ecosystem engineers in response to changing climate is restructuring endemic benthic communities globally. Therefore, developing and implementing efficient monitoring programs across the complete depth range of these marine ecosystem engineers is often an urgent management priority. Traditionally, many monitoring programs have been based on a systematically selected set of survey locations that, while able to track trends at those sites through time, lack inference for the overall region being monitored. This study trialled a probabilistic sampling design to address this need, taking advantage of an important prerequisite for such designs, extensive multibeam echosounder (MBES) mapping, to inform a spatially balanced sample selection. Here, we allocated 170 remotely operated vehicles (ROVs) transects based on a spatially balanced probabilistic sampling design across three locations with extensive mapping. Generalized additive models were used to estimate the density and associated barren cover of the range‐expanding ecosystem engineer, the long spined urchin (Centrostephanus rodgersii). Estimates were generated at a reef‐wide scale across three locations on the east coast of Tasmania, Australia, representing the leading edge of the species recent range extension. Model‐based estimates of urchin density and barren cover incorporated seabed structure attributes, such as depth and ruggedness, with differences in these modelled relationships being identified between locations. Estimates ranged from 0.000065 individuals m⁻² and 0.018% barren cover in the Tasman Peninsula to 0.167 individuals m⁻² and 2.10% barren cover at Governor Island Marine Reserve, reflecting a north to south distributional gradient. This study highlights the value of combining probabilistic sampling designs, ROV transects, stereo video, and MBES mapping to generate reliable and robust estimates of important ecosystem species needed to protect reef‐based fishery and conservation values via adaptive and informed management.