Projected ocean temperatures impair key proteins used in vision of octopus hatchlings.

Global warming is one of the most significant and widespread effects of climate change. While early life stages are particularly vulnerable to increasing temperatures, little is known about the molecular processes that underpin their capacity to adapt to temperature change during early development. Using a quantitative proteomics approach, we investigated the effects of thermal stress on octopus embryos. We exposed Octopus berrima embryos to different temperature treatments (control 19°C, current summer temperature 22°C, or future projected summer temperature 25°C) until hatching. By comparing their protein expression levels, we found that future projected temperatures significantly reduced levels of key eye proteins such as S-crystallin and retinol dehydrogenase 12, suggesting the embryonic octopuses had impaired vision at elevated temperature. We also found that this was coupled with a cellular stress response that included a significant elevation of proteins involved in molecular chaperoning and redox regulation. Energy resources were also redirected away from non-essential processes such as growth and digestion. These findings, taken together with the high embryonic mortality observed under the highest temperature, identify critical physiological functions of embryonic octopuses that may be impaired under future warming conditions. Our findings demonstrate the severity of the thermal impacts on the early life stages of octopuses as demonstrated by quantitative proteome changes that affect vision, protein chaperoning, redox regulation and energy metabolism as critical physiological functions that underlie the responses to thermal stress.

Experimental support towards a metabolic proxy in fish using otolith carbon isotopes.

Metabolic rate underpins our understanding of how species survive, reproduce and interact with their environment, but can be difficult to measure in wild fish. Stable carbon isotopes (δ13C) in ear stones (otoliths) of fish may reflect lifetime metabolic signatures but experimental validation is required to advance our understanding of the relationship. To this end, we reared juvenile Australasian snapper (Chrysophrys auratus), an iconic fishery species, at different temperatures and used intermittent-flow respirometry to calculate standard metabolic rate (SMR), maximum metabolic rate (MMR) and absolute aerobic scope (AAS). Subsequently, we analysed δ13C and oxygen isotopes (δ18O) in otoliths using isotope-ratio mass spectrometry. We found that under increasing temperatures, δ13C and δ18O significantly decreased, while SMR and MMR significantly increased. Negative logarithmic relationships were found between δ13C in otoliths and both SMR and MMR, while exponential decay curves were observed between proportions of metabolically sourced carbon in otoliths (Moto) and both measured and theoretical SMR. We show that basal energy for subsistence living and activity metabolism, both core components of field metabolic rates, contribute towards incorporation of δ13C into otoliths and support the use of δ13C as a metabolic proxy in field settings. The functional shapes of the logarithmic and exponential decay curves indicated that physiological thresholds regulate relationships between δ13C and metabolic rates due to upper thresholds of Moto Here, we present quantitative experimental evidence to support the development of an otolith-based metabolic proxy, which could be a powerful tool in reconstructing lifetime biological trends in wild fish.

How calorie-rich food could help marine calcifiers in a CO2-rich future.

Increasing carbon emissions not only enrich oceans with CO2 but also make them more acidic. This acidifying process has caused considerable concern because laboratory studies show that ocean acidification impairs calcification (or shell building) and survival of calcifiers by the end of this century. Whether this impairment in shell building also occurs in natural communities remains largely unexplored, but requires re-examination because of the recent counterintuitive finding that populations of calcifiers can be boosted by CO2 enrichment. Using natural CO2 vents, we found that ocean acidification resulted in the production of thicker, more crystalline and more mechanically resilient shells of a herbivorous gastropod, which was associated with the consumption of energy-enriched food (i.e. algae). This discovery suggests that boosted energy transfer may not only compensate for the energetic burden of ocean acidification but also enable calcifiers to build energetically costly shells that are robust to acidified conditions. We unlock a possible mechanism underlying the persistence of calcifiers in acidifying oceans.

A triple trophic boost: How carbon emissions indirectly change a marine food chain.

The pervasive enrichment of CO2 in our oceans is a well-documented stressor to marine life. Yet, there is little understanding about how CO2 affects species indirectly in naturally complex communities. Using natural CO2 vents, we investigated the indirect effects of CO2 enrichment through a marine food chain. We show how CO2 boosted the biomass of three trophic levels: from the primary producers (algae), through to their grazers (gastropods), and finally through to their predators (fish). We also found that consumption by both grazers and predators intensified under CO2 enrichment, but, ultimately, this top-down control failed to compensate for the boosted biomass of both primary producers and herbivores (bottom-up control). Our study suggests that indirect effects can buffer the ubiquitous and direct, negative effects of CO2 enrichment by allowing the upward propagation of resources through the food chain. Maintaining the natural complexity of food webs in our ocean communities could, therefore, help minimize the future impacts of CO2 enrichment.

The duality of ocean acidification as a resource and a stressor.

Ecologically dominant species often define ecosystem states, but as human disturbances intensify, their subordinate counterparts increasingly displace them. We consider the duality of disturbance by examining how environmental drivers can simultaneously act as a stressor to dominant species and as a resource to subordinates. Using a model ecosystem, we demonstrate that CO2 -driven interactions between species can account for such reversals in dominance; i.e., the displacement of dominants (kelp forests) by subordinates (turf algae). We established that CO2 enrichment had a direct positive effect on productivity of turfs, but a negligible effect on kelp. CO2 enrichment further suppressed the abundance and feeding rate of the primary grazer of turfs (sea urchins), but had an opposite effect on the minor grazer (gastropods). Thus, boosted production of subordinate producers, exacerbated by a net reduction in its consumption by primary grazers, accounts for community change (i.e., turf displacing kelp). Ecosystem collapse, therefore, is more likely when resource enrichment alters competitive dominance of producers, and consumers fail to compensate. By recognizing such duality in the responses of interacting species to disturbance, which may stabilize or exacerbate change, we can begin to understand how intensifying human disturbances determine whether or not ecosystems undergo phase shifts.

Testing hypoxia: physiological effects of long-term exposure in two freshwater fishes.

Hypoxic or oxygen-free zones are linked to large-scale mortalities of fauna in aquatic environments. Studies investigating the hypoxia tolerance of fish are limited and focused on marine species and short-term exposure. However, there has been minimal effort to understand the implications of long-term exposure on fish and their ability to acclimate. To test the effects of long-term exposure (months) of fish to hypoxia we devised a novel method to control the level of available oxygen. Juvenile golden perch (Macquaria ambigua ambigua), and silver perch (Bidyanus bidyanus), two key native species found within the Murray Darling Basin, Australia, were exposed to different temperatures (20, 24 and 28 °C) combined with normoxic (6-8 mgO2 L-1 or 12-14 kPa) and hypoxic (3-4 mgO2 L-1 or 7-9 kPa) conditions. After 10 months, fish were placed in individual respirometry chambers to measure standard and maximum metabolic rate (SMR and MMR), absolute aerobic scope (AAS) and hypoxia tolerance. Golden perch had a much higher tolerance to hypoxia exposure than silver perch, as most silver perch died after only 1 month exposure. Golden perch acclimated to hypoxia had reduced MMR at 20 and 28 °C, but there was no change to SMR. Long-term exposure to hypoxia improved the tolerance of golden perch to hypoxia, compared to individuals held under normoxic conditions suggesting that golden perch can acclimate to levels around 3 mgO2 L-1 (kPa ~ 7) and lower. The contrasting tolerance of two sympatric fish species to hypoxia highlights our lack of understanding of how hypoxia effects fish after long-term exposure.

Testing for thresholds of ecosystem collapse in seagrass meadows.

Although the public desire for healthy environments is clear-cut, the science and management of ecosystem health has not been as simple. Ecological systems can be dynamic and can shift abruptly from one ecosystem state to another. Such unpredictable shifts result when ecological thresholds are crossed; that is, small cumulative increases in an environmental stressor drive a much greater change than could be predicted from linear effects, suggesting an unforeseen tipping point is crossed. In coastal waters, broad-scale seagrass loss often occurs as a sudden event associated with human-driven nutrient enrichment (eutrophication). We tested whether the response of seagrass ecosystems to coastal nutrient enrichment is subject to a threshold effect. We exposed seagrass plots to different levels of nutrient enrichment (dissolved inorganic nitrogen) for 10 months and measured net production. Seagrass response exhibited a threshold pattern when nutrient enrichment exceeded moderate levels: there was an abrupt and large shift from positive to negative net leaf production (from approximately 0.04 leaf production to 0.02 leaf loss per day). Epiphyte load also increased as nutrient enrichment increased, which may have driven the shift in leaf production. Inadvertently crossing such thresholds, as can occur through ineffective management of land-derived inputs such as wastewater and stormwater runoff along urbanized coasts, may account for the widely observed sudden loss of seagrass meadows. Identification of tipping points may improve not only adaptive-management monitoring that seeks to avoid threshold effects, but also restoration approaches in systems that have crossed them.

Partial migration: growth varies between resident and migratory fish.

Partial migration occurs in many taxa and ecosystems and may confer survival benefits. Here, we use otolith chemistry data to determine whether fish from a large estuarine system were resident or migratory, and then examine whether contingents display differences in modelled growth based on changes in width of otolith growth increments. Sixty-three per cent of fish were resident based on Ba : Ca of otoliths, with the remainder categorized as migratory, with both contingents distributed across most age/size classes and both sexes, suggesting population-level bet hedging. Migrant fish were in slightly better condition than resident fish based on Fulton's K condition index. Migration type (resident versus migratory) was 56 times more likely to explain variation in growth than a model just incorporating year- and age-related growth trends. While average growth only varied slightly between resident and migratory fish, year-to-year variation was significant. Such dynamism in growth rates likely drives persistence of both life-history types. The complex relationships in growth between contingents suggest that management of species exhibiting partial migration is challenging, especially in a world subject to a changing climate.

Long-term patterns in estuarine fish growth across two climatically divergent regions.

Long-term ecological datasets are vital for investigating how species respond to changes in their environment, yet there is a critical lack of such datasets from aquatic systems. We developed otolith growth 'chronologies' to reconstruct the growth history of a temperate estuarine fish species, black bream (Acanthopagrus butcheri). Chronologies represented two regions in south-east Australia: South Australia, characterised by a relatively warm, dry climate, and Tasmania, characterised by a relatively cool, wet climate. Using a mixed modelling approach, we related inter-annual growth variation to air temperature, rainfall, freshwater inflow (South Australia only), and El Niño-Southern Oscillation events. Otolith chronologies provided a continuous record of growth over a 13- and 21-year period for fish from South Australia and Tasmania, respectively. Even though fish from Tasmania were sourced across multiple estuaries, they showed higher levels of growth synchronicity across years, and greater year-to-year growth variation, than fish from South Australia, which were sourced from a single, large estuary. Growth in Tasmanian fish declined markedly over the time period studied and was negatively correlated to temperature. In contrast, growth in South Australian fish was positively correlated to both temperature and rainfall. The stark contrast between the two regions suggests that Tasmanian black bream populations are more responsive to regional scale environmental variation and may be more vulnerable to global warming. This study highlights the importance of examining species response to climate change at the intra-specific level and further validates the emerging use of growth chronologies for generating long-term ecological data in aquatic systems.

Strontium randomly substituting for calcium in fish otolith aragonite.

The chemistry of fish ear bones (otoliths) is used to address fundamental questions in fish ecology and fisheries science. It is assumed that strontium (Sr), the most important element used in otolith chemistry research, is bound within the aragonitic calcium carbonate lattice of otoliths via random chemical replacement of calcium; however, this has never been tested and three other alternatives exist with regard to how Sr may be incorporated. If any variation in the mode of incorporation occurs, otolith chemistry data may be misinterpreted, impacting how fish and fisheries are understood and managed. Using X-ray absorption spectroscopy (specifically, analysis of extended X-ray absorption fine structure or EXAFS), we investigated how Sr is incorporated within fish otoliths from seven species collected from a range of aquatic environments. For comparison, aragonitic structures from other aquatic taxa (cephalopods and coral) were also analyzed. The results consistently indicated for all samples that Sr randomly replaces Ca within the aragonite lattice. This research explicitly shows how Sr is bound within otoliths and validates a fundamental and long-held assumption in aquatic research.

Using isotopic fingerprints in gastropod shells to validate commercial production pathway and geographic provenance.

Growing demand for high-value seafood is fuelling provenance fraud, which threatens the sustainability of wild fisheries while posing biosecurity and human health risks. Here, we investigated carbon (δ 13C) and oxygen (δ 18O) isotopes in abalone shells (Haliotis sp.) to determine the production method and geographical provenance. Using X-ray diffraction and isotope ratio mass spectrometry, we found that shell mineralogy did not influence isotope values. Isotope values between wild and farmed sectors were statistically different, with 64% of individuals correctly classified as farmed or wild. Subsequently, we successfully distinguished the provenance of abalone collected from farms (with 83% of individuals correctly classified), as well as wild-caught abalone collected from four state jurisdictions (with 88% correctly classified). Carbon isotopes were strongly correlated to longitude, with both isotopes correlated to latitude. Overall, this study demonstrates the potential of isotopic fingerprints in gastropod shells to track the provenance of commercially valuable species.

Developing isotopic proxies to reconstruct the metabolic rates and thermal histories of octopus.

Understanding an animal's metabolic rate and thermal history is pivotal for ecological research. Recent studies have proposed the use of stable carbon and oxygen isotopes (δ13C and δ18O) in biogenic carbonates as proxies of metabolic rate and experienced temperature, respectively, to overcome the challenges of directly measuring these data in the field. Our study represents the first experimental investigation to develop δ13C and δ18O proxies in octopus. Octopus berrima hatchlings were raised in captivity, at varying water temperatures, for up to 110 days. O. berrima statoliths were then subsequently analysed for δ13C and δ18O values. The proportion of metabolically derived carbon, or respired carbon (Cresp), increased as the octopus grew (slope = 0.076, R2 = 0.72), suggesting an influence of somatic growth rate and body mass on δ13C values. Additionally, we identified an inverse correlation between δ18O values and environmental temperature (slope = -0.163, R2 = 0.91), which was subsequently used to develop a thermal reconstruction model. Our experiment aids in interpreting stable isotopic values in statoliths and their application as temperature and metabolic proxies in wild-caught octopus. Such proxies will increase our monitoring capabilities of these ecologically and commercially significant cephalopods and contribute to their conservation and effective management.

Innovation to limit seafood fraud post-COVID-19.

Seafood is an important source of protein and micronutrients, but fishery stocks are increasingly under pressure from both legitimate and illegitimate fishing practices. Sustainable management of our oceans is a global responsibility, aligning with United Nations Sustainable Development Goal 14, Life Below Water. In a post-COVID-19 world, there is an opportunity to build back better, where locally sourced food via transparent supply chains are ever-more important. This article summarises emerging research of two innovative case studies in detecting and validating seafood provenance; and using alternative supply chains to minimise the opportunity for seafood fraud in a post-COVID-19 world.

Better late than never: Optimising the proteomic analysis of field-collected octopus.

Proteomics, the temporal study of proteins expressed by an organism, is a powerful technique that can reveal how organisms respond to biological perturbations, such as disease and environmental stress. Yet, the use of proteomics for addressing ecological questions has been limited, partly due to inadequate protocols for the sampling and preparation of animal tissues from the field. Although RNAlater is an ideal alternative to freezing for tissue preservation in transcriptomics studies, its suitability for the field could be more broadly examined. Moreover, existing protocols require samples to be preserved immediately to maintain protein integrity, yet the effects of delays in preservation on proteomic analyses have not been thoroughly tested. Hence, we optimised a proteomic workflow for wild-caught samples. First, we conducted a preliminary in-lab test using SDS-PAGE analysis on aquaria-reared Octopus berrima confirming that RNAlater can effectively preserve proteins up to 6 h after incubation, supporting its use in the field. Subsequently, we collected arm tips from wild-caught Octopus berrima and preserved them in homemade RNAlater immediately, 3 h, and 6 h after euthanasia. Processed tissue samples were analysed by liquid chromatography tandem mass spectrometry to ascertain protein differences between time delay in tissue preservation, as well as the influence of sex, tissue type, and tissue homogenisation methods. Over 3500 proteins were identified from all tissues, with bioinformatic analysis revealing protein abundances were largely consistent regardless of sample treatment. However, nearly 10% additional proteins were detected from tissues homogenised with metal beads compared to liquid nitrogen methods, indicating the beads were more efficient at extracting proteins. Our optimised workflow demonstrates that sampling non-model organisms from remote field sites is achievable and can facilitate extensive proteomic coverage without compromising protein integrity.

Tracking the provenance of octopus using isotopic and multi-elemental analysis.

Octopus play an increasingly important role in ocean ecosystems and global fisheries, yet techniques for authenticating provenance are sorely lacking. For the first time, we investigate whether chemical profiling can distinguish geographical origins of octopus on international and domestic scales. Our samples consisted of wild-caught octopus from south-east Asia and southern Australia, regions with high seafood trade. We used a novel combination of stable carbon (δ13C) and oxygen (δ18O) isotope analyses (Isotope-Ratio Mass Spectrometry) of internal calcified structures called statoliths, with elemental analyses (X-Ray Fluorescence using Itrax) of soft-tissue. We found that multivariate profiles exhibited distinctive regional signatures, even across species, with high classification success (∼95%) back to region of origin. This study validates isotopic and multi-elemental profiling as an effective provenance tool for octopus, which could be used to support transparency and accountability of seafood supply chains and thus encourage sustainable use of ocean resources.

A multilevel approach to examining cephalopod growth using Octopus pallidus as a model.

Many aspects of octopus growth dynamics are poorly understood, particularly in relation to sub-adult or adult growth, muscle fibre dynamics and repro-somatic investment. The growth of 5 month old Octopus pallidus cultured in the laboratory was investigated under three temperature regimes over a 12 week period: seasonally increasing temperatures (14-18°C); seasonally decreasing temperatures (18-14°C); and a constant temperature mid-way between seasonal peaks (16°C). Differences in somatic growth at the whole-animal level, muscle tissue structure and rate of gonad development were investigated. Continuous exponential growth was observed, both at a group and at an individual level, and there was no detectable effect of temperature on whole-animal growth rate. Juvenile growth rate (from 1 to 156 days) was also monitored prior to the controlled experiment; exponential growth was observed, but at a significantly faster rate than in the older experimental animals, suggesting that O. pallidus exhibit a double-exponential two-phase growth pattern. There was considerable variability in size-at-age even between individuals growing under identical thermal regimes. Animals exposed to seasonally decreasing temperatures exhibited a higher rate of gonad development compared with animals exposed to increasing temperatures; however, this did not coincide with a detectable decline in somatic growth rate or mantle condition. The ongoing production of new mitochondria-poor and mitochondria-rich muscle fibres (hyperplasia) was observed, indicated by a decreased or stable mean muscle fibre diameter concurrent with an increase in whole-body size. Animals from both seasonal temperature regimes demonstrated higher rates of new mitochondria-rich fibre generation relative to those from the constant temperature regime, but this difference was not reflected in a difference in growth rate at the whole-body level. This is the first study to record ongoing hyperplasia in the muscle tissue of an octopus species, and provides further insight into the complex growth dynamics of octopus.

Demonstrating the ascendancy of COVID-19 research using acronyms.

"COVID" which stands for corona virus disease, has become the world's most infamous acronym. Previous analysis of acronyms in health and medical journals found a growing use of acronyms over time in titles and abstracts, with "DNA" as the most common. Here we examine acronyms in the pandemic year of 2020 to show the dramatic rise of COVID-related research. "COVID" was over five times more frequently used than "DNA" in 2020, and in just one year it has become the sixth most popular acronym of all time, surpassing "AIDS", "PCR" and "MRI".

Better Writing in Scientific Publications Builds Reader Confidence and Understanding.

Scientific publications are the building blocks of discovery and collaboration, but their impact is limited by the style in which they are traditionally written. Recently, many authors have called for a switch to an engaging, accessible writing style. Here, we experimentally test how readers respond to such a style. We hypothesized that scientific abstracts written in a more accessible style would improve readers' reported readability and confidence as well as their understanding, assessed using multiple-choice questions on the content. We created a series of scientific abstracts, corresponding to real publications on three scientific topics at four levels of difficulty-varying from the difficult, traditional style to an engaging, accessible style. We gave these abstracts to a team of readers consisting of 170 third-year undergraduate students. Then, we posed questions to measure the readers' readability, confidence, and understanding with the content. The scientific abstracts written in a more accessible style resulted in higher readability, understanding, and confidence. These findings demonstrate that rethinking the way we communicate our science may empower a more collaborative and diverse industry.

The growth of acronyms in the scientific literature.

Some acronyms are useful and are widely understood, but many of the acronyms used in scientific papers hinder understanding and contribute to the increasing fragmentation of science. Here we report the results of an analysis of more than 24 million article titles and 18 million article abstracts published between 1950 and 2019. There was at least one acronym in 19% of the titles and 73% of the abstracts. Acronym use has also increased over time, but the re-use of acronyms has declined. We found that from more than one million unique acronyms in our data, just over 2,000 (0.2%) were used regularly, and most acronyms (79%) appeared fewer than 10 times. Acronyms are not the biggest current problem in science communication, but reducing their use is a simple change that would help readers and potentially increase the value of science.