Ocean warming is increasing the frequency, extent, and severity of tropical-coral bleaching and mortality. During 2014-2017, marine heatwaves caused the Third Global Coral Bleaching Event. We analyze data from 15,066 reef surveys globally during 2014-2017. Across all surveyed reefs, 80% and 35% experienced moderate or greater (affecting >10% of corals) bleaching and mortality, respectively. We assess the global extent of coral bleaching and mortality by applying bleaching response curves calibrated from surveyed reefs to predict bleaching globally, based on comprehensive remote-sensing of heat stress. These models predict that 51% and 15% of the world's coral reefs suffered moderate or greater bleaching and mortality, respectively, during one or multiple years, surpassing damage from any prior global coral bleaching event. Our findings demonstrate that the impacts of ocean warming on coral reefs are accelerating, with the near certainty that ongoing warming will cause large-scale, possibly irreversible, degradation of these essential ecosystems. With heat stress levels during this event surpassing those observed previously, the National Oceanic and Atmospheric Administration developed more extreme Bleaching Alert levels that are now being used during the ongoing Fourth Global Coral Bleaching Event.

The predictable nature of whale shark (Rhincondon typus) aggregations around the world forms the basis for nature-based tourism. The Ningaloo Marine Park (NMP), Western Australia is one of those locations and a management program has been in place since 1993. Measuring the effectiveness of the management program is important to minimise potential impacts on the whale sharks. In NMP tour operator vessels are equipped with an Electronic Management System (EMS) to collect data during whale shark encounters. Using EMS data and associated images of identified whale sharks from the months of March to July between 2011 to 2019, Generalised Additive Mixed Models (GAMMs) and Generalised Linear Mixed Effect Models (GLMMs) assessed the variation in duration of whale shark encounters. Using EMS data from 2010 to 2023 we mapped the density distribution of all whale shark encounters to identify hotspots. From the 44,017 whale shark encounters between 2011 to 2019, 7585 involved 986 individuals. On average individual sharks were encountered 4.30 times per day (± SD 3.15), with a mean duration of 15.30 mins (± SD 13.17). In Tantabiddi, daily encounters, distance, Southern Oscillation Index (SOI), habitat and vessel were important in predicting the variation in encounter duration, whereas in Coral Bay daily encounters, encounter number, SOI, sex and vessel were important at predicting the variation in encounter duration. There was no evidence to suggest a significant variation in whale shark encounter duration between days after repeated encounters in Tantabiddi or Coral Bay. However, some individuals were repeatedly encountered in a day with a cumulative encounter duration up to 224 minutes. A significant negative relationship between encounter duration and number of daily encounters was identified for Tantabiddi -0.073, p-value < 0.001, Coral Bay -12.3, p-value < 0.001 and for NMP overall -0.083, p-value <0.001. A Gi* statistic identified significant whale shark encounter hotspots where commercial whale shark encounters occur in higher densities. Our findings support the best practice standard of the whale shark management program in the NMP, however the potential pressure of prolonged cumulative whale shark encounter durations, and the high density of the whale shark encounters in some areas warrants further investigation.

The expansion of the world 's merchant fleet poses a great threat to the ocean 's biodiversity. Collisions between ships and marine megafauna can have population-level consequences for vulnerable species. The Endangered whale shark ( Rhincodon typus ) shares a circumglobal distribution with this expanding fleet and tracking of movement pathways has shown that large vessel collisions pose a major threat to the species. However, it is not yet known whether they are also at risk within aggregation sites, where up to 400 individuals can gather to feed on seasonal bursts of planktonic productivity. These "constellation " sites are of significant ecological, socioeconomic and cultural value. Here, through expert elicitation, we gathered information from most known constellation sites for this species across the world ( >50 constellations and >13,000 individual whale sharks). We defined the spatial boundaries of these sites and their overlap with shipping traffic. Sites were then ranked based on relative levels of potential collision danger posed to whale sharks in the area. Our results showed that researchers and resource managers may underestimate the threat posed by large ship collisions due to a lack of direct evidence, such as injuries or witness accounts, which are available for other, sub-lethal threat categories. We found that constellations in the Arabian Sea and adjacent waters, the Gulf of Mexico, the Gulf of California, and Southeast and East Asia, had the greatest level of collision threat. We also identified 39 sites where peaks in shipping activity coincided with peak seasonal occurrences of whale sharks, sometimes across several months. Simulated collision mitigation options estimated potentially minimal impact to industry, as most whale shark core habitat areas were small. Given the threat posed by vessel collisions, a coordinated, multi-national approach to mitigation is needed within priority whale shark habitats to ensure collision protection for the species.

Understanding predator-prey interactions at the vulnerable egg and hatchling stage of sea turtles is crucial to effectively manage these threatened marine species. Our research quantified ghost crab predation on loggerhead turtles Caretta caretta at Gnaraloo Bay and Bungelup Beach, two of the four principal nesting sites for this species in the Southeast Indian Ocean. We counted ghost crab burrows along belt transects as a proxy for crab densities. We used start- and end-of-season nesting inventories to determine egg predation rates, in-situ accelerometers to measure predation activity in nests, and infrared videography to assess predation rates on emerging hatchlings. Ghost crab densities and egg predation rates at Gnaraloo Bay were almost twice those at Bungelup Beach. Egg predation was most prevalent at night and in the first and third trimesters of incubation. We did not observe any hatchlings emerging from nests at Gnaraloo Bay, while we observed predation, mainly by ghost crabs and to a lesser extent by seagulls, on 43% of hatchlings at Bungelup Beach. The alarmingly high rate of mortality due to native predators highlights a need for immediate management actions to mitigate this threat to a globally important loggerhead turtle stock. Our multi-method approach provides a holistic estimation of reproductive success from when eggs were laid to when hatchlings reached the relative safety of the ocean.

Ocean warming is increasing the incidence, scale, and severity of global-scale coral bleaching and mortality, culminating in the third global coral bleaching event that occurred during record marine heatwaves of 2014-2017. While local effects of these events have been widely reported, the global implications remain unknown. Analysis of 15,066 reef surveys during 2014-2017 revealed that 80% of surveyed reefs experienced significant coral bleaching and 35% experienced significant coral mortality. The global extent of significant coral bleaching and mortality was assessed by extrapolating results from reef surveys using comprehensive remote-sensing data of regional heat stress. This model predicted that 51% of the world’s coral reefs suffered significant bleaching and 15% significant mortality, surpassing damage from any prior global bleaching event. These observations demonstrate that global warming’s widespread damage to coral reefs is accelerating and underscores the threat anthropogenic climate change poses for the irreversible transformation of these essential ecosystems.

Marine debris (MD) is a serious environmental concern globally. Yet, few studies have reported on MD in sanctuary zones of the Indian Ocean. Consequently, coastal transects were conducted to determine MD quantity, composition and distribution at northern Ningaloo Marine Park, Western Australia. Debris density ranged between 0.004 and 0.02 items m(-2) with the greatest density near Exmouth township. Composition was predominantly plastic (61%) with fishing-related items (25.5%) and plastic fragments/remnants (16%) the most numerous overall. Land-based and general sourced MD accounted for 88% of all debris. Debris levels were significantly lower at sites with higher visitation and increased distance from access points. There was no significant difference between sanctuary and non-sanctuary zones. Although not immune to MD, this study suggests its remote location, environmental awareness and management strategies implemented at Ningaloo Marine Park may be key to its low MD levels.

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.

Beach strandings of 31 Keesingia gigas Gershwin, 2014, occurred in Exmouth Gulf, north-western Australia, between 16 and 25 March 2016, with 17 strandings recorded in just two days. Between 28 March and 31 May 2017 there were another 54 reports of K. gigas, many of multiple individuals, mostly on the Ningaloo coast west of Exmouth. These events provided an opportunity to examine this large but rarely observed jellyfish, as the only previous specimen collected was the holotype, off Shark Bay in 2012. Of 19 specimens collected and/or photographed on the beach in 2016, overall medusa length ranged from 190 to 345 mm, except for two 80 mrn individuals. All but one of the smallest lacked tentacles, consistent with the original description of the species, photographs and field observations recorded in this study. The tentacles observed on the smallest animal examined may represent ontogenetic variability. Clusters of nematocysts were observed on the velarial margin of the bell. Three confirmed envenomations of adult people in 2016 did not result in them developing symptoms of Irukandji syndrome, however among six confirmed envenomations in 2017, two stings to adults resulted in some systemic Irukandji syndrome symptoms. In 2016, most sightings of K. gigas were in Exmouth Gulf, while in 2017 almost all were on the ocean side of North West Cape, indicating distribution was not solely restricted to Exmouth Gulf. Prevailing winds in the five days leading up to strandings in 2016 also suggest the jellyfish had been transported from the ocean north of Exmouth and not from within Exmouth Gulf Similarly in 2017, prevailing winds and waves were consistent with currents moving jellyfish from north to south, with the time course of observations beginning in the northern part of Ningaloo in March and finishing in the southern section in May. All known sightings of K. gigas have been made in the March to May period in five separate years. Public awareness campaigns by the Shire of Exmouth in 2016 and Department of Biodiversity, Conservation and Attractions in 2017 were successful in raising awareness of the potential threat to swimmers and beach users and also proved effective in obtaining reports of the distribution of K. gigas.

The Ningaloo coast of north-western Australia (eastern Indian Ocean) hosts one of the world’s longest and most extensive fringing coral reef systems, along with globally significant abundances of large marine fauna such as whale sharks. These characteristics – which have contributed to its inscription on the World Heritage list – exist because of the unique climatic, geomorphologic and oceanographic conditions. The region is hot and arid, so runoff of water from land is low, facilitating clear water that allows corals to grow close to the shore. The polewardflowing Leeuwin Current is an important influence, bringing warm water and generally suppressing coastal upwelling. During the austral summer, strong southerly winds generate the equatorwardflowing Ningaloo Current on the inner shelf – this current facilitates sporadic upwelling events that enhance concentrations of nutrients, which in turn enhance pelagic primary productivity that supports the reef’s biota. The coast has experienced several marine heatwaves since 2011 that have caused mortality of corals and probably seagrass, albeit relatively less than elsewhere along the coast. Wind-generated surface waves break over the fringing reef crest, causing cooling currents that tend to dampen warming – although this mechanism seems not to have prevented some areas from experiencing damaging heat, and corals in places that do not receive the wave-generated currents have experienced substantial mortality. Herbivores, from fish to green turtles, are abundant, and in the lagoon, extensive stands of large brown algae provide an important habitat for newly recruited fish. There has been a decline in abundance of some fish. Predictions of future pressures include a weaker but more variable Leeuwin Current and increased human use. The ability of Ningaloo’s

Western Australia’s coral reefs have largely escaped the chronic pressures affecting other reefs around the world, but are regularly affected by seasonal storms and cyclones, and increasingly by heat stress and coral bleaching. Reef systems north of 18°S have been impacted by heat stress and coral bleaching during strong El Niño phases and those further south during strong La Niña phases. Cumulative heat stress and the extent of bleaching throughout the northern reefs in 2016 were higher than at any other time on record. To assess the changing regime of disturbance to reef systems across Western Australia (WA), we linked their site-specific exposure to damaging waves and heat stress since 1990 with mean changes in coral cover. Since 2010, there has been a noticeable increase in heat stress and coral bleaching across WA. Over half the reef systems have been severely impacted by coral bleaching since 2010, which was further compounded by cyclones at some reefs. For most (75%) reef systems with long-term data (5–26 yrs), mean coral cover is currently at (or near) the lowest on record and a full recovery is unlikely if disturbances continue to intensify with climate change. However, some reefs have not yet experienced severe bleaching and their coral cover has remained relatively stable or increased in recent years. Additionally, within all reef systems the condition of communities and their exposure to disturbances varied spatially. Identifying the communities least susceptible to future disturbances and linking them through networks of protected areas, based on patterns of larval connectivity, are important research and management priorities in coming years while the causes of climate change are addressed.

In-water shark-based tourism is growing worldwide and whale sharks (Rhincodon typus) are one of the most popular targets of this industry. It is important to monitor tourism industries to minimize any potential impacts on target species. At Ningaloo, Western Australia, Electronic Monitoring Systems (EMS) have been installed on licensed tour vessels to collect information on encounters between snorkelers and whale sharks. This study combined data from the EMS with whale shark identification photographs, to assess the impact of in-water tourism on the encounter duration for individual sharks. During 2011 and 2012, 948 encounters with 229 individual sharks were recorded using EMS. Encounter durations between whale sharks and tourism vessels ranged between 1 and 59 min (mean = 11 min 42 s, SD = ±11 min 19 s). We found no evidence for a decline in encounter duration after repeated tourist encounters with individual sharks. Encounter duration varied among tourism operator vessels and were shorter when the sex of the whale shark could not be identified. Given that individual sharks were swum with on average 2.4 times per day (±SD 2.08), and up to 16 times over the course of the study, our results suggest that there is no evidence of long-term impacts of tourism on the whale sharks at Ningaloo. However, the inclusion of well-defined categories of whale shark behaviors and information regarding how interactions between tourists and whale sharks end will complement the data already collected by the EMS. This preliminary investigation demonstrates the potential for the EMS as a data resource to better understand and monitor the impacts of tourism interactions on whale sharks.

Documentation of scarring patterns on marine megafauna provides a means of quantifying the risk of anthropogenic threats that occur in the open ocean, such as ship strike. This study investigated the rates and putative sources of scarring of whale sharks Rhincodon typus aggregating at Ningaloo, Western Australia. Identification photos of whale sharks were contributed by tourism operators and research groups over a 6 yr period. Analysis of this database found that 355 (38.8%) of 913 whale sharks individually identified between 2008 and 2013 exhibited some form of scarring. This decreased to 15.9% after the omission of categories of minor scarring (nicks and abrasions). An increase in the number of sharks with lacerations between 2008 and 2013 provides some evidence of increasing boat strikes over this time. However, capture-mark-recapture modelling using the multi-state open robust design found no evidence that major scarring influenced the apparent survival or residency time of whale sharks aggregating at Ningaloo. Although lacerations are a useful indication of the level of threat to whale sharks from boat strike, it cannot necessarily be attributed to boat activity in Ningaloo due to the migratory nature of whale sharks in this aggregation, which commonly venture beyond Australian waters. Close collaboration with whale shark tourism operators proved a vital tool to generate the volume of data required for this assessment, and provides a model for similar studies of other megafauna with an associated tourism industry.

Marine snakes represent the most speciose group of marine reptiles and are a significant component of reef and coastal ecosystems in tropical oceans. Research on this group has historically been challenging due to the difficulty in capturing, handling, and keeping these animals for field- and lab-based research. Inexplicable declines in marine snake populations across global hotspots have highlighted the lack of basic information on this group and elevated multiple species as conservation priorities. With the increased interest in research on marine snakes, we conducted a systematic survey of experts to identify twenty key questions that can direct future research. These questions are framed across a wide array of scientific fields to produce much-needed information relevant to the conservation and management of marine snakes.

A diverse suite of fish and invertebrates form commensal and parasitic relationships with scyphozoan jellyfish. Associations between ophiuroids and medusae, however, are rare. We investigated the relationship between the common semaeostome jellyfish Aurelia aurita and the ophiuroid Ophiocnemis marmorata at Ningaloo Reef in Western Australia. We assessed the prevalence of the association; described the relationship between medusa size and the number of ophiuroids they hosted; and used stable isotope analysis to determine whether O. marmorata were feeding on medusae hosts or planktonic prey. Seventy-nine per cent of the 92 medusae sampled hosted between 1 and 14 ophiuroids that ranged in size from 1 to 6mm disc diameter. The number of ophiuroids hosted was positively correlated with medusa size and all medusae >135 mm bell diameter hosted at least one ophiuroid. Stable Isotope Analysis in R modelling of delta C-13 and delta N-15 of the ophiuroids and their potential food sources indicated that ophiuroids derived their nutrition predominantly from mesozooplankton and seston and not from medusae. Ophiuroids were never observed filter feeding, so we suggest that the ophiuroids may be kleptoparasites that steal planktonic food from their host. These results highlight the important role of medusae in supporting pelagic biodiversity.

This study examined whale shark behaviour using fixed-wing aerial surveys in Ningaloo Marine Park between 2007 and 2009. The aims of the project were to develop and trial a method to test for impacts of tourism vessels and swimmers on whale shark behaviour. Whale sharks made significantly more directional changes when vessels were present, with approximately twice as many changes in direction observed per scan when a vessel was present. Whale sharks also maintained neutral behaviours, such as surface swimming, swimming at depth, resurfacing, or no reaction during interactions and, notably, more of these were recorded when a vessel was present. This suggests that, while behaviours were maintained regardless of the presence of vessels, whale sharks may have still responded to vessels by changing direction more frequently. The aerial observations were effective in detecting an increase in directional changes but further behavioural studies are required to improve our understanding of natural diving and surfacing behaviour in whale sharks. Alternative research platforms and technologies may be necessary to investigate whale shark behaviour in more detail and to further evaluate potential impacts of tourism interactions on whale sharks.

Shark depredation (damage to gear and loss of bait or hooked fish by a non-target species) is a common global occurrence. Depredation events by sharks can have negative impacts for the fishers, fishery targeted species and the sharks. It is, therefore important to better understand if learning behaviour of sharks can influence rates of depredation. Recreational fishers within the World Heritage Ningaloo Reef have reported increased rates of depredation by sharks over the last 5 years. This study aimed to determine if sharks are capable of learning to associate intensive recreational fishing activities with a food reward. We also aimed to test if sharks in areas frequently fished were more habituated to recreational fishing activities than those sharks within a no-take marine sanctuary. To simulate fishing activities baited underwater video systems were deployed in the morning (A.M.), midday, and afternoon (P.M.) for six consecutive days in Fished and Unfished sites. A significant decrease in time of arrival and time to first feed of sharks was seen across days at the Fished sites. The Unfished sites had very low numbers of sharks observed (n=3) and therefore was not statistically analysed. The relative abundance of sharks did not significantly increase across days, however there was a negative correlation between lemon sharks ( Negaprion sp . ) and whalers ( Carcharhinus sp.). Our study suggests sharks are capable of being classically conditioned to recreational fishing activities and depredation rates are influenced by fisher behaviour. We have highlighted possible mitigation strategies designed to un-condition sharks to recreational fishing, including modifying fishing practices, use of deterrents based on the sensitivity of shark senses and management strategies. The best approach is likely to be enabling fishers to become more knowledgeable of how and why shark depredation events happen and take appropriate steps to avoid them.