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With increasing sea water temperatures, higher latitude temperate and sub-tropical coral reefs are becoming increasingly tropicalised. Although these cooler areas might offer refuge to tropical species escaping the heat, the reshaping of ecosystems can have devastating effects on the biodiversity in these areas, especially when habitat structure is affected. Recently, feeding aggregations of corallivorous gastropod Drupella cornus, a tropical species capable of large-scale reef degradation, were found at Rottnest Island in Western Australia (32°S). We provide evidence that D. cornus spawned at Rottnest Island for 2 consecutive years in 2021 and 2022, and Drupella veligers from an egg case collected at the island hatched and grew at temperatures in the laboratory that were predominantly lower than those at Rottnest Island at the same time. The spawning was possibly triggered by higher than usual La Niña-associated SSTs during the survey period, or the long period of high sea water temperature anomalies recorded around Rottnest Island. A spawning population of D. cornus can greatly affect these higher latitude reef areas, especially when accompanied by increased heat stress. Monitoring and management should be implemented to further understand what effects a breeding population of D. cornus has on Rottnest Island. [ABSTRACT FROM AUTHOR]

Biodiversity conservation and management requires surveillance that captures the full spectrum of taxa. Here, we showcase the potential for a portfolio of visual, extractive, and molecular methods for detecting previously hidden components of tropical fish biodiversity in an economically and culturally valuable marine site that spans a tropical‐temperate ecotone—the Ningaloo Coast World Heritage Area. With scale and practicality in mind, we demonstrate how environmental DNA (eDNA) methods deployed in a stratified sampling design can yield a more comprehensive monitoring program for species presence than current alternatives (e.g., extractive sampling via anesthetic). eDNA from filtered water samples detected up to six times as many cryptobenthic fish species per site than samples collected with anesthetic, indicating it is a potentially powerful tool for assessing biodiversity of tropical fishes. However, there were also species that were only found when using anesthetic and the contribution of cryptobenthic species to overall diversity of the fish assemblage was unexpectedly low, suggesting not all cryptobenthic fish species have been detected with eDNA. There were also distinct differences in cryptobenthic assemblages both among sites and sample depths (2–3 m) when using eDNA from filtered water, suggesting this technique may be able to identify fine scale spatial differences in cryptobenthic fish assemblage. eDNA collected from water detects the most cryptobenthic species and is therefore an efficient tool for rapidly assessing biodiversity, but extractive techniques may still be required for biological and monitoring studies, and when combined with eDNA sampling provides the most comprehensive assessment of cryptobenthic fishes. [ABSTRACT FROM AUTHOR]

Coral reefs face increasing pressures in response to unprecedented rates of environmental change at present. The coral reef physical framework is formed through the production of calcium carbonate (CaCO3) and maintained by marine organisms, primarily hermatypic corals, and calcifying algae. The northern part of Western Australia, known as the Kimberley, has largely escaped land-based anthropogenic impacts and this study provides important metabolic data on reef-building organisms from an undisturbed set of marine habitats. From the reef platform of Browse Island, located on the mid-shelf just inside the 200 m isobath off the Kimberley coast, specimens of the dominant coral (six species) and algal (five species) taxa were collected and incubated ex situ in light and dark shipboard experimental mesocosms for 4 h to measure rates of calcification and production patterns of oxygen. During experimental light and dark incubations, all algae were net autotrophic producing 6 to 111 mmolO2m-2d-1. In contrast, most corals were net consumers of O2 with average net fluxes ranging from - 42 to 47 mmolO2m-2d-1. The net change in pH was generally negative for corals and calcifying algae (- 0.01 to - 0.08 h-1). Resulting net calcification rates (1.9 to 9.9 gCaCO3m-2d-1) for corals and calcifying algae (Halimeda and Galaxura) were all positive and were strongly correlated with net O2 production. In intertidal habitats around Browse Island, estimated relative contributions of coral and Halimeda to the reef production of CaCO3 were similar at around 600 to 840 gm-2yr-1. The low reef platform had very low coral cover of < 3 % which made a smaller contribution to calcification of ∼ 240 gCaCO3m-2yr-1. Calcification on the subtidal reef slope was predominantly from corals, producing ∼ 1540 gCaCO3m-2yr-1 , twice that of Halimeda. These data provide the first measures of community metabolism from the offshore reef systems of the Kimberley. The relative contributions of the main reef builders, in these undisturbed areas, to net community metabolism and CaCO3 production is important to understand exclusively climate-driven negative effects on tropical reefs. [ABSTRACT FROM AUTHOR]

Passive collection is an emerging sampling method for environmental DNA (eDNA) in aquatic systems. Passive eDNA collection is inexpensive and efficient, and requires minimal equipment, making it suited to high‐density sampling and remote deployment. Here, we compare the effectiveness of nine membrane materials for passively collecting fish eDNA from a 3‐million‐litre marine mesocosm. We submerged materials (cellulose, cellulose with 1% and 3% chitosan, cellulose overlayed with electrospun nanofibres and 1% chitosan, cotton fibres, hemp fibres, and sponge with either zeolite or active carbon) for intervals between 5 and 1080 min. We show that for most materials, with as little as 5 min of submersion, mitochondrial fish eDNA measured with qPCR, and fish species richness measured with metabarcoding, was comparable to that collected by conventional filtering. Furthermore, PCR template DNA concentrations and species richness were generally not improved significantly by longer submersion. Species richness detected for all materials ranged between 11 and 37 species, with a median of 27, which was comparable to the range for filtered eDNA (19–32). Using scanning electron microscopy, we visualized biological matter adhering to the surface of materials, rather than entrapped, with images also revealing a diversity in size and structure of putative eDNA particles. eDNA can be collected rapidly from seawater with a passive approach and using a variety of materials. This will suit cost‐ and time‐sensitive biological surveys, and where access to equipment is limited. [ABSTRACT FROM AUTHOR]

Coral reefs face increasing pressures in response to unprecedented rates of environmental change at present. The coral reef physical framework is formed through the production of calcium carbonate (CaCO3) and maintained by marine organisms, primarily hermatypic corals, crustose coralline algae (CCA), and other calcifying algae. The Kimberley bioregion, located in the northern part of Western Australia, has largely escaped land-based anthropogenic impacts and this study provides important metabolic data we are lacking on reef-building calcifying corals and macrophytes from an undisturbed set of marine habitats. Specimens of the dominant coral and algal taxa were collected from the reef platform of Browse Island located on the mid-shelf just inside the 200 m isobath off the Kimberley coast. During experimental light/dark incubations, all algae were net autotrophic producing 6–111 mmol O2 m−2 day−1. In contrast, most corals were net consumers of O2 with average net fluxes ranging from −42 to 47 mmol O2 m−2 day−1. The net change in pH was generally negative for corals and calcifying algae (−0.01 to −0.08 h−1). Corals, Halimeda (a calcifying green algae) and Galaxaura (a calcifying red algae) had positive calcification rates in light ranging from 4.2 to 18.4 g CaCO3 m−2 d−1. Resulting net calcification rates were all positive and ranged from 1.9 to 9.9 g CaCO3 m−2 d−1 and were strongly correlated to net O2 production. In intertidal habitats around Browse Island, estimated relative contributions of coral and Halimeda to the reef production of CaCO3 were similar at around 600–840 g m−2 year−1. The low reef platform had very low coral cover of < 3 % which made a smaller contribution to calcification of ~240 g CaCO3 m−2 year−1. Calcification on the subtidal reef slope was predominantly from corals, producing ~1540 g CaCO3 m−2 year−1, twice that of Halimeda. The relative contributions of the main reef builders, in these undisturbed areas, to net community metabolism and CaCO3 production and reef metabolism is important to understand exclusively climate-driven coral bleaching and mortality. [ABSTRACT FROM AUTHOR]

Coral reefs face increasing pressures in response to unprecedented rates of environmental change at present. The coral reef physical framework is formed through the production of calcium carbonate (CaCO3) and maintained by marine organisms, primarily hermatypic corals, crustose coralline algae (CCA), and other calcifying algae. The Kimberley bioregion, located in the northern part of Western Australia, has largely escaped land-based anthropogenic impacts and this study provides important metabolic data we are lacking on reef-building calcifying corals and macrophytes from an undisturbed set of marine habitats. Specimens of the dominant coral and algal taxa were collected from the reef platform of Browse Island located on the mid-shelf just inside the 200 m isobath off the Kimberley coast. During experimental light/dark incubations, all algae were net autotrophic producing 6–111 mmol O2 m−2 day−1. In contrast, most corals were net consumers of O2 with average net fluxes ranging from −42 to 47 mmol O2 m−2 day−1. The net change in pH was generally negative for corals and calcifying algae (−0.01 to −0.08 h−1). Corals, Halimeda (a calcifying green algae) and Galaxaura (a calcifying red algae) had positive calcification rates in light ranging from 4.2 to 18.4 g CaCO3 m−2 d−1. Resulting net calcification rates were all positive and ranged from 1.9 to 9.9 g CaCO3 m−2 d−1 and were strongly correlated to net O2 production. In intertidal habitats around Browse Island, estimated relative contributions of coral and Halimeda to the reef production of CaCO3 were similar at around 600–840 g m−2 year−1. The low reef platform had very low coral cover of < 3 % which made a smaller contribution to calcification of ~240 g CaCO3 m−2 year−1. Calcification on the subtidal reef slope was predominantly from corals, producing ~1540 g CaCO3 m−2 year−1, twice that of Halimeda. The relative contributions of the main reef builders, in these undisturbed areas, to net community metabolism and CaCO3 production and reef metabolism is important to understand exclusively climate-driven coral bleaching and mortality. [ABSTRACT FROM AUTHOR]

Sea urchins can play a critical ecological role in the functioning of marine benthic ecosystems, mediating competitive interactions between corals and algae. Yet, little is known about factors affecting urchin distribution in intact coral reef systems. This study aims to determine the spatial distribution of two sympatric urchin species, Echinometra mathaei and Echinostrephus molaris , and potential factors contributing to this, within the intact coral reef system of Ningaloo Marine Park, north-western Western Australia. Benthic photographs and surveys were conducted on SCUBA at 126 sites across the Park to determine urchin presence, rugosity, substrate cover, water velocity, and fish predation for each site. Generalised additive models found that E. mathaei presence was positively related to algal cover, rugosity and non-sanctuary zones, suggesting that distribution may be driven by foraging behaviour, habitat complexity and predation. Echinostrephus molaris presence was positively related to habitat and region, suggesting its distribution may be largely driven by hydrodynamics, feeding strategy and regional variation. This study highlighted species-habitat associations and the complexities of these in structuring urchin communities. Although occupying similar niches, the predominantly non-overlapping feeding preferences, and morphological and behavioural differences between E. mathaei and E. molaris enable these species to coexist within the intact reef system of Ningaloo Marine Park. Sea urchins can play a critical ecological role in the functioning of marine benthic ecosystems, mediating competitive interactions between corals and algae. Yet, little is known about factors affecting urchin distribution in intact coral reef systems. This study determines the spatial distribution and occurrence of two sympatric urchin species, Echinometra mathaei and Echinostrephus molaris , and the potential factors contributing to this, within the Ningaloo Marine Park. [ABSTRACT FROM AUTHOR]

Most of the world's tropical coastal and shelf areas are heavily affected by anthropogenic activities, but the north-west shelf of Australia is considered a 'very low-impact' area. The role of herbivory on coral reefs is recognised, but most of that research comes from reefs with considerable land-based impacts. In this study we sampled the teleost community and evaluated herbivory on the reef platform at Browse Island, a small isolated island 200 km off north-western Australia, using several approaches: (1) tethering of macroalgae; (2) herbivore exclosures; and (3) video footage. In total, 99 teleost species from 26 families were identified. Turf algal consumption was evident and 18 teleost turf consumers were identified. In contrast, no evidence was found of herbivory on large macroalgae, and browsers, the only group able to consume macroalgae, were represented by just four species all belonging to the genus Naso. The lack of diversity among these specialist herbivores may be a consequence of the small surface area of the reef and the distance to other emergent reefs. Based on a model of top-down control of macroalgae, the reef is potentially vulnerable to disturbance. Small isolated reefs can have low resilience despite having low impacts from land. We sampled fish and evaluated herbivory on the reef platform at Browse Island, 200 km off north-western Australia. We found 99 fish species, 18 of which are known to eat turf, but only 4 that eat macroalgae. Fish were eating turf on the reef, but we found no evidence they were eating macroalgae. This may make the reef more vulnerable to overgrowth of algae in the future. [ABSTRACT FROM AUTHOR]

The increased occurrence of extreme climate events, such as marine heatwaves (MHWs), has resulted in substantial ecological impacts worldwide. To date, metrics of thermal stress within marine systems have focussed on coral communities, and less is known about measuring stress relevant to other primary producers, such as seagrasses. An extreme MHW occurred across the Western Australian coastline in the austral summer of 2010–2011, exposing marine communities to summer seawater temperatures 2–5°C warmer than average. Using a combination of satellite imagery and in situ assessments, we provide detailed maps of seagrass coverage across the entire Shark Bay World Heritage Area (ca. 13,000 km2) before (2002 and 2010) and after the MHW (2014 and 2016). Our temporal analysis of these maps documents the single largest loss in dense seagrass extent globally (1,310 km2) following an acute disturbance. Total change in seagrass extent was spatially heterogeneous, with the most extensive declines occurring in the Western Gulf, Wooramel Bank and Faure Sill. Spatial variation in seagrass loss was best explained by a model that included an interaction between two heat stress metrics, the most substantial loss occurring when degree heating weeks (DHWm) was ≥10 and the number of days exposed to extreme sea surface temperature during the MHW (DaysOver) was ≥94. Ground truthing at 622 points indicated that change in seagrass cover was predominantly due to loss of Amphibolis antarctica rather than Posidonia australis, the other prominent seagrass at Shark Bay. As seawater temperatures continue to rise and the incidence of MHWs increase globally, this work will provide a basis for identifying areas of meadow degradation, or stability and recovery, and potential areas of resilience. [ABSTRACT FROM AUTHOR]

Diet studies provide base understanding of trophic structure and are a valuable initial step for many fields of marine ecology, including conservation and fisheries biology. Considerable complexity in marine trophic structure can exist due to the presence of highly mobile species with long life spans. Mobula rays are highly mobile, large, planktivorous elasmobranchs that are frequently caught either directly or as bycatch in fisheries, which, combined with their conservative life history strategy, makes their populations susceptible to decline in intensely fished regions. Effective management of these iconic and vulnerable species requires an understanding of the diets that sustain them, which can be difficult to determine using conventional sampling methods. We use three DNA metabarcode assays to identify 44 distinct taxa from the stomachs (n = 101) of four sympatric Mobula ray species (Mobula birostris, Mobula tarapacana, Mobula japanica, and Mobula thurstoni) caught over 3 years (2013–2015) in a direct fishery off Bohol in the Philippines. The diversity and incidence of bony fishes observed in ray diets were unprecedented. Nevertheless, rays showed dietary overlap, with krill (Euphausia) dominating their diet. Our results provide a more detailed assessment of sympatric ray diets than was previously described and reveal the complexity that can exist in food webs at critical foraging habitats. We use three DNA metabarcode assays to identify 44 distinct taxa from the stomachs (n = 101) of four sympatric Mobula ray species (Mobula birostris, Mobula tarapacana, Mobula japanica, and Mobula thurstoni) caught over 3 years (2013–2015) in a direct fishery near Bohol in the Philippines. The diversity and incidence of bony fishes observed in ray diets were unprecedented. Nevertheless, rays showed dietary overlap, with krill (Euphausia) dominating their diet. [ABSTRACT FROM AUTHOR]

As atmospheric CO2 levels continue to rise so too does the risk of severe impacts. Scientists clearly have an important role to play in preparing for and responding to climate change impacts; however, calls by scientists for global action have not led to the required changes. It is timely, therefore, for scientists to critically consider their own approach toward climate change research, particularly if we are to ameliorate or adapt to unwanted outcomes. Here we present three different pathways that allow scientists and scientific institutions to conceptualize the implications of their responses to climate change scenarios. These pathways are illustrated via three plausible futures for the marine environment under climate change. This approach allows future responsibilities, outcomes, and implication to be explored within and across pathways and can be applied to different scenarios for scientists and scientific institutions to anticipate and better prepare to contribute effectively to the future. Plain Language Summary: There is mounting evidence that impacts of climate change pose significant risks to society and human well‐being. The pace of large‐scale action on climate change is, however, insufficient to substantially reduce the likely future impacts. These are risks that this generation is imposing on future generations. In this context we outline a framework for scientists and scientific institutions to explore and assess the outcomes and implications of choosing different pathways (inactive, reactive, and proactive) in response to climate change. We developed three illustrative examples of plausible futures under climate change to demonstrate the implications of each of these pathways. We also outline a conceptual framework based on three factors: (i) potential to mitigate, (ii) impact of risk, and (iii) uncertainty in science that will assist scientists and scientific institutions to make informed decisions regarding their responses to global environmental change. Key Points: The implications of three pathways for scientists to respond to climate change are discussed such as maintaining trust in scienceA conceptual model is presented based on three factors: (i) potential to mitigate, (ii) impact of risk, and (iii) uncertainty in scienceA framework to assist scientists and scientific institutions to make informed decisions in response to global environmental change is outlined [ABSTRACT FROM AUTHOR]

RATIONALE Stable isotope analysis (SIA) is a powerful tool in many fields of research that enables quantitative comparisons among studies, if similar methods have been used. The goal of this study was to determine if three different drying methods commonly used to prepare samples for SIA yielded different δ15N and δ13C values. METHODS Muscle subsamples from 10 individuals each of three teleost species were dried using three methods: (i) oven, (ii) food dehydrator, and (iii) freeze-dryer. All subsamples were analysed for δ15N and δ13C values, and nitrogen and carbon content, using a continuous flow system consisting of a Delta V Plus mass spectrometer and a Flush 1112 elemental analyser via a Conflo IV universal interface. The δ13C values were normalized to constant lipid content using the equations proposed by McConnaughey and McRoy. RESULTS Although statistically significant, the differences in δ15N values between the drying methods were small (mean differences ≤0.21‰). The differences in δ13C values between the drying methods were not statistically significant, and normalising the δ13C values to constant lipid content reduced the mean differences for all treatments to ≤0.65‰. A statistically significant difference of ~2% in C content existed between tissues dried in a food dehydrator and those dried in a freeze-dryer for two fish species. There was no significant effect of fish size on the differences between methods. CONCLUSIONS No substantial effect of drying method was found on the δ15N or δ13C values of teleost muscle tissue. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We fitted hierarchical Bayesian models to coded wire tag data and studied the variation in the probability that male coho salmon released at 72 locations in 41 basins and 8 regions mature early. We used data from at least 10 cohorts at each location; therefore, our analysis was both spatially and temporally more extensive than those conducted previously. We accounted for variation in the log-odds of early maturation with (1) mean smolt weight, (2) covariates (developed specifically for this paper) that indexed marine environmental conditions during the first few months after out-migration, and (3) hierarchical means that identified each cohort's release location, basin, and region. There was posterior support for location-specific effects of smolt size on the probability of early maturation across the geographic range of this species, but not for location-specific marine environmental effects. Nevertheless, substantial residual variation remained from our final analysis; we argue that this variation can be attributed to environmental effects that were not detected here. The spatial variation in the probability of early maturation was dominated by region-level differences in freshwater rearing conditions, as evidenced by positive relationships between mean smolt weight and the expected log-odds of early maturation at all levels in the geographic hierarchy. We identified more than one such relationship, and the differences between the center and the edges of the geographic range are considered here. Ultimately, since we defined regions on the basis of existing evolutionarily significant units for coho salmon, our results further support the use of these units for management and conservation purposes. [ABSTRACT FROM AUTHOR]

The reproductive performances of growth-enhanced transgenic, hatchery, and cultured nontransgenic coho salmon were examined to investigate the consequences of reproductive interaction between growth hormone (GH)-transgenic fish and wild fish that may occur if transgenic salmon escaped into the natural environment. We examined adult morphological phenotypes, gamete quantity and quality, in vitro offspring production, courtship and spawning behavior, male competitive behavior, and transgene transmission to offspring. Transgenic, hatchery, and cultured nontransgenic fish required 2, 3, and 3 or 4 years, respectively, to reach sexual maturation. No differences in male gamete quantity or in vitro offspring production were observed. Transgenic females were more fecund than hatchery females but had smaller eggs. Fewer transgenic females spawned than hatchery females under experimental conditions, and transgenic females displayed consistently low levels of courtship behavior. In noncompetitive trials, there were no differences in the courtship behavior of transgenic and hatchery males; during competition with hatchery males, however, transgenic males failed to spawn and displayed less courtship and competitive behavior. Cultured nontransgenic salmon also displayed reduced spawning capacity relative to hatchery salmon, indicating that the effects observed in transgenic salmon may arise in part from being reared in the culture environment and highlighting the difficulty in using laboratory-reared transgenic fish to assess reproductive fitness because of the strong genotype-environment interactions. As long as wild-reared transgenic fish are unavailable, exact determinations of reproductive fitness will be difficult. However, these studies have shown that in a simulated natural environment, growth-enhanced transgenic coho salmon do display courtship behavior and can spawn, producing viable transgenic offspring. The findings suggest some capacity exists for the natural transmission of transgenes to populations arising from reproductive interaction, which could occur during first contact between escaped cultured transgenic fish and wild conspecifics. [ABSTRACT FROM AUTHOR]

A Correction to this paper has been published: https://doi.org/10.1038/s42003-021-01994-6 [ABSTRACT FROM AUTHOR]