Organismal Traits Research Articles

Quantifying microplastic ingestion, degradation and excretion in insects using fluorescent plastics.

Plastic pollution is a growing threat to our natural environment. Plastic waste/pollution results from high emissions of both macro (>5mm) and microplastics (MPs; <5mm) as well as environmental fractioning of macroplastics into MPs. MPs have been shown to have a range of negative impacts on biota. Harmonized methods to accurately measure and count MPs from animal samples are limited, but what methods exist are not ideal for a controlled laboratory environment where plastic ingestion, degradation and elimination can be quantified and related to molecular, physiological and organismal traits. Here, we propose a complete method for isolating and quantifying fluorescent MPs by combining several previously reported approaches into one comprehensive workflow. We combine tissue dissection, organic material digestion, sample filtering and automated imaging techniques to show how fluorescently labelled MPs provided to insects (e.g. in their diet) in a laboratory setting can be isolated, identified and quantified. As a proof of concept, we fed crickets (Gryllodes sigillatus) a diet of 2.5% (w/w) fluorescently labelled plastics and isolated and quantified plastic particles within the gut and frass.

Applications of bioinformatics in epigenetics.

Epigenetic modifications such as DNA methylation, post-translational chromatin modifications and non-coding RNA-mediated mechanisms are responsible for epigenetic inheritance. Change in gene expression due to these epigenetic modifications are responsible for new traits in different organisms leading to various diseases including cancer, diabetic kidney disease (DKD), diabetic nephropathy (DN) and renal fibrosis. Bioinformatics is an effective approach for epigenomic profiling. These epigenomic data can be analyzed by a large number of bioinformatics tools and software. Many databases are available online, which comprises huge amount of information regarding these modifications. Recent methodologies include many sequencing and analytical techniques to extrapolate different types of epigenetic data. This data can be used to design drugs against diseases linked to epigenetic modifications. This chapter briefly highlights different epigenetics databases (MethDB, REBASE, Pubmeth, MethPrimerDB, Histone Database, ChromDB, MeInfoText database, EpimiR, Methylome DB, and dbHiMo), and tools (compEpiTools, CpGProD, MethBlAST, EpiExplorer, and BiQ analyzer), which are being utilized to retrieve the data and mechanistically analysis of epigenetics modifications.

A geometric approach to understanding biological responses to environmental fluctuations from the perspective of marine organisms

A main concern in marine ecology is understanding the mechanisms driving the responses of biological systems to environmental fluctuations. A major issue is that each biological system (e.g. organism, ecosystem) experiences fluctuations according to its own intrinsic characteristics. For instance, how an organism experiences a thermal fluctuation, i.e. as a long marine heatwave or as a mild pulse, depends on its thermal tolerance and developmental time, which can vary as the fluctuation is experienced. Here, a geometric approach is explored, considering the biological perspective. Environmental fluctuations are represented as points in a ‘space of fluctuations’. The biological perspective is then defined as a coordinate frame within that space. Coordinates are given by components (e.g. amplitude and time scale) characterising each environmental fluctuation, which are then transformed into biological scales, using biological traits (tolerance and biological time). Using simulations of organisms growing under thermal fluctuations with different characteristics, the present study shows how this approach (1) enables the integration of physiology and phenology to better interpret biological responses to fluctuating environments; (2) improves our understanding of the role of adaptive plasticity as a rescue effect; and (3) facilitates our understanding of the effects of thermal fluctuations on additional organismal traits (e.g. body mass). Wider applications in the context of species persistence, coexistence, biodiversity and ecosystem function in scenarios of extreme fluctuations are also discussed.

Recent allopolyploidy alters Spartina microRNA expression in response to xenobiotic-induced stress.

Environmental contamination by xenobiotics represents a major threat for natural ecosystems and public health. In response, xenobiotic detoxification is a fundamental trait of organisms for developmental plasticity and stress tolerance, but the underlying molecular mechanisms remain poorly understood in plants. To decipher this process, we explored the consequences of allopolyploidy on xenobiotic tolerance in the genus Spartina Schreb. Specifically, we focused on microRNAs (miRNAs) owing to their central function in the regulation of gene expression patterns, including responses to stress. Small RNA-Seq was conducted on the parents S. alterniflora and S. maritima, their F1 hybrid S. x townsendii and the allopolyploid S. anglica under phenanthrene-induced stress (phe), a model Polycyclic Aromatic Hydrocarbon (PAH) compound. Differentially expressed miRNAs in response to phe were specifically identified within species. In complement, the respective impacts of hybridization and genome doubling were detected, through changes in miRNA expression patterns between S. x townsendii, S. anglica and the parents. The results support the impact of allopolyploidy in miRNA-guided regulation of plant response to phe. In total, we identified 17 phe-responsive miRNAs in Spartina among up-regulated MIR156 and down-regulated MIR159. We also describe novel phe-responsive miRNAs as putative Spartina-specific gene expression regulators in response to stress. Functional validation using Arabidopsis (L.) Heynh. T-DNA lines inserted in homologous MIR genes was performed, and the divergence of phe-responsive miRNA regulatory networks between Arabidopsis and Spartina was discussed.

Biotic interactions shape trait assembly of marine communities across time and latitude.

Assembly processes are highly dynamic with biotic filters operating more intensely at local scales, yet the strength of biotic interactions can vary across time and latitude. Predation, for example, can be stronger at lower latitudes, while competition can intensify at later stages of assembly due to resource limitation. Since biotic filters act upon functional traits of organisms, we explored trait-mediated community assembly in diverse marine assemblages from four regions along the Pacific coast of North and Central America. Using predator exclusion experiments and two assembly stages, we tested the hypotheses that non-random trait patterns would emerge during late assembly at all regions due to competition and at lower latitude regions regardless of assembly stage due to predation. As expected, trait divergence occurred in late assembly but only at higher latitude regions, while in tropical Panama, relaxed predation caused trait divergence during late assembly. Moreover, colonizing trait strategies were common during early assembly while competitive strategies were favoured during late assembly at higher latitude regions. Predation-resistant traits were only favoured in Panama during both assembly stages. Our large-scale manipulative study demonstrates that different biotic interactions across time and latitude can have important consequences for trait assembly.

Evidence for adaptive morphological plasticity in the Caribbean coral, Acropora cervicornis

Genotype-by-environment interactions (GxE) indicate that variation in organismal traits cannot be explained by fixed effects of genetics or site-specific plastic responses alone. For tropical coral reefs experiencing dramatic environmental change, identifying the contributions of genotype, environment, and GxE on coral performance will be vital for both predicting persistence and developing restoration strategies. We quantified the impacts of G, E, and GxE on the morphology and survival of the endangered coral, Acropora cervicornis, through an in situ transplant experiment exposing common garden (nursery)-raised clones of ten genotypes to nine reef sites in the Florida Keys. By fate-tracking outplants over one year with colony-level 3D photogrammetry, we uncovered significant GxE on coral size, shape, and survivorship, indicating that no universal winner exists in terms of colony performance. Rather than differences in mean trait values, we found that individual-level morphological plasticity is adaptive in that the most plastic individuals also exhibited the fastest growth and highest survival. This indicates that adaptive morphological plasticity may continue to evolve, influencing the success of A. cervicornis and resulting reef communities in a changing climate. As focal reefs are active restoration sites, the knowledge that variation in phenotype is an important predictor of performance can be directly applied to restoration planning. Taken together, these results establish A. cervicornis as a system for studying the ecoevolutionary dynamics of phenotypic plasticity that also can inform genetic- and environment-based strategies for coral restoration.

Different Traits, Different Evolutionary Pathways: Insights from Salamandrina (Amphibia, Caudata).

Species delimitation is often based on a single or very few genetic or phenetic traits, something which leads to misinterpretations and often does not provide information about evolutionary processes. Here, we investigated the diversity pattern of multiple phenetic traits of the two extant species of Salamandrina, a genus split only after molecular traits had been studied but the two species of which are phenetically very similar. The phenetic traits we studied are size, external body shape and head colour pattern, in a model comparison framework using non-linear mixed models and unsupervised and supervised clustering. Overall, we found high levels of intra-specific variability for body size and shape, depending on population belonging and habitat, while differences between species were generally lower. The habitat the salamanders dwell in also seems important for colour pattern. Basing on our findings, from the methodological point of view, we suggest (i) to take into account the variability at population level when testing for higher level variability, and (ii) a semi-supervised learning approach to high dimensional data. We also showed that different phenotypic traits of the same organism could result from different evolutionary routes. Local adaptation is likely responsible for body size and shape variability, with selective pressures more similar across species than within them. Head colour pattern also depends on habitat, differently from ventral colour pattern (not studied in this paper) which likely evolved under genetic drift.

Ten (mostly) simple rules to future‐proof trait data in ecological and evolutionary sciences

Abstract Traits have become a crucial part of ecological and evolutionary sciences, helping researchers understand the function of an organism's morphology, physiology, growth and life history, with effects on fitness, behaviour, interactions with the environment and ecosystem processes. However, measuring, compiling and analysing trait data comes with data‐scientific challenges. We offer 10 (mostly) simple rules, with some detailed extensions, as a guide in making critical decisions that consider the entire life cycle of trait data. This article is particularly motivated by its last rule, that is, to propagate good practice. It has the intention of bringing awareness of how data on the traits of organisms can be collected and managed for reuse by the research community. Trait observations are relevant to a broad interdisciplinary community of field biologists, synthesis ecologists, evolutionary biologists, computer scientists and database managers. We hope these basic guidelines can be useful as a starter for active communication in disseminating such integrative knowledge and in how to make trait data future‐proof. We invite the scientific community to participate in this effort at http://opentraits.org/best‐practices.html.

О применении биометрии в антропологии и основных задачах науки

The task of biometrics in anthropology is to describe and analyze the random variability inherent in a person as an object of study. At the modern time, multivariate biometric models are widely used for this, in which it is assumed that the observed quantitative organism traits are expressed as weighted sums of latent random factors (for example, principal component analysis, factor and discriminant analyses, canonical variables, etc.). The given assumption is consistent with the existence of general and specific biological factors-causes that determine the organism traits. Since the main task of science is to study the laws of cause-and-effect in nature, it is important to analyze the relationship between statistical and causal dependences. Results and discussion. Statistical factors obtained as a result of data processing (such as the general size, shape, etc.) in the general case not only disagree with the causal factors, but may even contradict them. It is shown that the statistical coefficients of correlation, regression, and covariance, even in the simplest case of two traits randomly varying under the influence of one common cause and several specific factors, can take on infinitely many values under the same causal relationship, and with the same statistical pattern of variability, there are infinitely many causal explanations it. Conclusions. Interpretation in relation to the cause-and-effect patterns of trait determination and other causal conclusions should not follow from the results of the application of one-dimensional and multidimensional biometric models that use the indicated statistical coefficients as input data.

Building a foundation for gene family analysis in Rosaceae genomes with a novel workflow: A case study in Pyrus architecture genes.

The rapid development of sequencing technologies has led to a deeper understanding of plant genomes. However, direct experimental evidence connecting genes to important agronomic traits is still lacking in most non-model plants. For instance, the genetic mechanisms underlying plant architecture are poorly understood in pome fruit trees, creating a major hurdle in developing new cultivars with desirable architecture, such as dwarfing rootstocks in European pear (Pyrus communis). An efficient way to identify genetic factors for important traits in non-model organisms can be to transfer knowledge across genomes. However, major obstacles exist, including complex evolutionary histories and variable quality and content of publicly available plant genomes. As researchers aim to link genes to traits of interest, these challenges can impede the transfer of experimental evidence across plant species, namely in the curation of high-quality, high-confidence gene models in an evolutionary context. Here we present a workflow using a collection of bioinformatic tools for the curation of deeply conserved gene families of interest across plant genomes. To study gene families involved in tree architecture in European pear and other rosaceous species, we used our workflow, plus a draft genome assembly and high-quality annotation of a second P. communis cultivar, 'd'Anjou.' Our comparative gene family approach revealed significant issues with the most recent 'Bartlett' genome - primarily thousands of missing genes due to methodological bias. After correcting assembly errors on a global scale in the 'Bartlett' genome, we used our workflow for targeted improvement of our genes of interest in both P. communis genomes, thus laying the groundwork for future functional studies in pear tree architecture. Further, our global gene family classification of 15 genomes across 6 genera provides a valuable and previously unavailable resource for the Rosaceae research community. With it, orthologs and other gene family members can be easily identified across any of the classified genomes. Importantly, our workflow can be easily adopted for any other plant genomes and gene families of interest.

The fate of terrestrial biodiversity during an oceanic island volcanic eruption

Volcanic activity provides a unique opportunity to study the ecological responses of organisms to catastrophic environmental destruction as an essential driver of biodiversity change on islands. However, despite this great scientific interest, no study of the biodiversity at an erupting volcano has yet been undertaken. On La Palma (Canary archipelago), we quantified the main species affected and their fate during the 85-day eruption (September–December 2021). Our main objective consisted of monitoring the biodiversity subjected to critical stress during this volcanic eruption. We found that all biodiversity within a 2.5 km radius was severely affected after the first two weeks. It is challenging to assess whether volcanism can drive evolutionary traits of insular organisms. Examples are the adaptation of an endemic conifer to high temperatures, selection of functional plant types—secondary woodiness—, effects of the disappearance of invertebrates and their influence in trophic nets and vertebrate trophic plasticity. However, our data suggest that such previous evolutionary changes might continue to favour their resilience during this eruption. Lastly, it is a very good opportunity to assess the extent to which these periodic volcanic catastrophes may constitute temporary windows of repeated opportunities for the evolution and speciation of oceanic island biota.

Polystyrene Microparticles and the Functional Traits of Invertebrates: A Case Study on Freshwater Shrimp Neocardina heteropoda

The excessive worldwide production of plastic materials results in omnipresent microplastic pollution. Scientific studies dealing with the impacts of microplastics on aquatic ecosystems focus mainly on the marine environment, documenting the effect on the functional traits of various organisms. Polystyrene, one of the most commonly used plastics, has become a widely used model in this respect. In our study, freshwater shrimps (Neocardina heteropoda) were exposed to virgin polystyrene particles (size 0.5 mm; nominal concentration 8 mgL−1), and their behavioral and physiological responses were compared to control shrimp. The exposed shrimps exhibited modified activity patterns (greater speeds, accelerations and distances moved), accompanied by a lowered standard metabolic rate (SMR). The observed effects differed in their progression from the 7th to 14th day of exposure, from undetectable changes (distance, SMR) to significant differences (speed, acceleration). Significant differences were also detected in the behavioral syndromes expressed by the exposed and controlled shrimps, indicating that the microplastics influence not only the particular traits, but also their functional relationships. As such, our study contributes to the integration of behavioral ecotoxicology in risk assessment, documenting the adverse performance of freshwater invertebrates exposed to microplastics with the potential to transpose the problem to higher levels of the food web.

Stoichiometric stability of aquatic organisms increases with trophic level under warming and eutrophication

The balance of stoichiometric traits of organisms is crucial for nutrient cycling and energy flow in ecosystems. However, the impacts of different drivers on stoichiometric (carbon, C; nitrogen, N; and phosphorus, P) variations of organisms have not been well addressed. In order to understand how stoichiometric traits vary across trophic levels under different environmental stressors, we performed a mesocosm experiment to explore the impacts of warming (including +3 °C consistent warming above ambient and heat waves ranging from 0 to 6 °C), eutrophication, herbicide and their interactions on stoichiometric traits of organisms at different trophic levels, which was quantified by stable nitrogen isotopes. Results showed that herbicide treatment had no significant impacts on all stochiometric traits, while warming and eutrophication significantly affected the stoichiometric traits of organisms at lower trophic levels. Eutrophication increased nutrient contents and decreased C: nutrient ratios in primary producers, while the response of N:P ratios depended on the taxonomic group. The contribution of temperature treatments to stoichiometric variation was less than that of eutrophication. Heat waves counteracted the impacts of eutrophication, which was different from the effects of continuous warming, indicating that eutrophication impacts on organism stoichiometric traits depended on climate scenarios. Compared to environmental drivers, taxonomic group was the dominant driver that determined the variations of stoichiometric traits. Furthermore, the stoichiometric stability of organisms was strongly positively correlated with their trophic levels. Our results demonstrate that warming and eutrophication might substantially alter the stoichiometric traits of lower trophic levels, thus impairing the nutrient transfer to higher trophic level, which might further change the structure of food webs and functions of the ecosystems.

Patterns in aquatic metacommunities are associated with environmental and trait heterogeneity

Abstract Metacommunities are structured by a combination of different ecological factors that vary in their importance depending on environmental heterogeneity and species functional equivalence. However, empirical tests of such context‐dependence at regional scales are still missing. We investigated associations between deterministic (e.g. environmental filtering and biotic interactions) and stochastic factors (e.g. dispersal related) and metacommunity structure of macroinvertebrates and diatoms across streams in four regions with contrasting levels of environmental and organismal trait heterogeneity. Environmental filtering was most strongly associated with the region that showed moderate environmental heterogeneity and comprised communities with the highest trait heterogeneity. Associations with stochastic factors in the regions were more variable and difficult to predict. Environmental factors and the degree of genus‐level association were generally more strongly associated with macroinvertebrates than with diatoms, whereas stochastic factors had consistently lower influence on macroinvertebrates. These results suggest that the degree to which deterministic versus stochastic factors influence aquatic metacommunities depends on environmental and trait heterogeneity. Furthermore, organismal characteristics such as dispersal potential, habitat specialisation and sensitivity to environmental variation can also generate considerable context dependency in metacommunity structure.

Revealing coastal upwelling impact on the muscle growth of an intertidal fish

Upwelling oceanographic phenomenon is associated with increased food availability, low seawater temperature and pH. These conditions could significantly affect food quality and, in consequence, the growth of marine species. One of the most important organismal traits is somatic growth, which is highly related to skeletal muscle. In fish, skeletal muscle growth is highly influenced by environmental factors (i.e. temperature and nutrient availability) that showed differences between upwelling and downwelling zones. Nevertheless, there are no available field studies regarding the impact of those conditions on fish muscle physiology. This work aimed to evaluate the muscle fibers size, protein content, gene expression of growth and atrophy-related genes in fish sampled from upwelling and downwelling zones. Seawater and fish food items (seaweeds) samples were collected from upwelling and downwelling zones to determine the habitat's physical-chemical variations and the abundance of biomolecules in seaweed tissue. In addition, white skeletal muscle samples were collected from an intertidal fish to analyze muscular histology, the growth pathways of protein kinase B and the extracellular signal-regulated kinase; and the gene expression of growth- (insulin-like growth factor 1 and myosin heavy-chain) and atrophy-related genes (F-box only protein 32 and muscle RING-finger protein-1). Upwelling zones revealed higher nutrients in seawater and higher protein content in seaweed than samples from downwelling zones. Moreover, fish from upwelling zones presented a greater size of muscle fibers and protein content compared to downwelling fish, associated with lower protein ubiquitination and gene expression of F-box only protein 32. Our data indicate an attenuated use of proteins as energy source in upwelling conditions favoring protein synthesis and muscle growth. This report shed lights of how oceanographic conditions may modulate food quality and fish muscle physiology in an integrated way, with high implications for marine conservation and sustainable fisheries management.

Ecological and evolutionary trends of body size in Pristimantis frogs, the world's most diverse vertebrate genus

Body size is a key organismal trait. However, the environmental and evolutionary factors that drive body size patterns at the interspecific level remain unclear. Here, we explored these relationships between phenotype-environment using neotropical frogs of Pristimantis, the world’s most diverse vertebrate genus. We analyzed: (a) whether this group follows the Rensch’s rule, a trend of sexual size dimorphism (SSD) to increase with size when males are the larger sex; (b) whether environmental constraints have influenced body size variation; and (c) how the rates of body size evolution have varied over time. Analyses were based on two information sources, the first one including body sizes of ~ 85% (495 species) of known species in the genus, and a second one incorporating molecular phylogenetic information for 257 species. Our results showed that all Pristimantis species exhibited marked SSD but did not follow Rensch’s rule. We found that the models that best explained body size in males, females, and SSD contained environmental variations in temperature, precipitation, and elevation as predictors. In turn, body size has evolved toward an optimum, with a decelerating rate of evolution differentiated between the large Pristimantis clades.

Recent reconfiguration of an ancient developmental gene regulatory network in Heliocidaris sea urchins.

Changes in developmental gene regulatory networks (dGRNs) underlie much of the diversity of life, but the evolutionary mechanisms that operate on regulatory interactions remain poorly understood. Closely related species with extreme phenotypic divergence provide a valuable window into the genetic and molecular basis for changes in dGRNs and their relationship to adaptive changes in organismal traits. Here we analyse genomes, epigenomes and transcriptomes during early development in two Heliocidaris sea urchin species that exhibit highly divergent life histories and in an outgroup species. Positive selection and chromatin accessibility modifications within putative regulatory elements are enriched on the branch leading to the derived life history, particularly near dGRN genes. Single-cell transcriptomes reveal a dramatic delay in cell fate specification in the derived state, which also has far fewer open chromatin regions, especially near conserved cell fate specification genes. Experimentally perturbing key transcription factors reveals profound evolutionary changes to early embryonic patterning events, disrupting regulatory interactions previously conserved for ~225 million years. These results demonstrate that natural selection can rapidly reshape developmental gene expression on a broad scale when selective regimes abruptly change. More broadly, even highly conserved dGRNs and patterning mechanisms in the early embryo remain evolvable under appropriate ecological circumstances.

Combining functional diversity of lotic fish communities with river health assessment based on multi-metric chemical pollution and biological integrity index models

Trait-based functional studies are widely used to elucidate the relationships between ecological indicators and environmental parameters as well as to predict functional change in aquatic biota in response to various types of human disturbance. Clarifying how functional traits of aquatic organisms depend on environmental conditions can facilitate aquatic conservation and management, but determining the importance of these traits to ecological river health requires further investigation. As fish play a key role in the assessment of ecological conditions, we examined the relevance of the functional diversity of lotic fish to the river health assessment using multi-metric models of water pollution (mWPI) and fish-based biological integrity (mIBI). Twelve fish traits related to food acquisition, environmental stability, and mobility were used for the functional analyses. Chemical river health was highly sensitive to downstream organic matter and nutrient pollution according to mWPI. Based on the present gradient of chemical health and water chemical variables, we identified three water quality groups (G-I, G-II, and G-III). G-I, G-II, and G-III showed low, intermediate, and high levels of water quality degradation, respectively. Spatially significant differences among these groups were observed for both the taxonomic and functional structures of lotic fish as well as ecological river health based on mIBI. The dominance of sensitive species was high in G-I, whereas tolerant and exotic species contributed strongly to the species compositions of G-II and G-III. Functional richness and dispersal were significantly reduced in G-III, and their decreases correlated with ecological health and the loss of species that are insectivorous, rheophilic, and sensitive to water pollution. Regarding redundancy analyses, both the models of functional trait metrics (F = 8.06, p &amp;lt; 0.001) and mIBI metrics (F = 4.88, p &amp;lt; 0.01) indicated good performance in terms of the variation in water quality and chemical river health parameters. Overall, the functional trait-based diversity of lotic fish is significant to the assessment of ecological river health and reflects water chemical quality. This association arises because niche occupation in functional space by all species, along with their abundance distribution, is highly responsive to the loss of species with sensitive traits due to water pollution.

Three perspectives on the prediction of chemical effects in ecosystems.

The increasing production, use and emission of synthetic chemicals into the environment represents a major driver of global change. The large number of synthetic chemicals, limited knowledge on exposure patterns and effects in organisms and their interaction with other global change drivers hamper the prediction of effects in ecosystems. However, recent advances in biomolecular and computational methods are promising to improve our capacity for prediction. We delineate three idealised perspectives for the prediction of chemical effects: the suborganismal, organismal and ecological perspective, which are currently largely separated. Each of the outlined perspectives includes essential and complementary theories and tools for prediction but captures only part of the phenomenon of chemical effects. Links between the perspectives may foster predictive modelling of chemical effects in ecosystems and extrapolation between species. A major challenge for the linkage is the lack of data sets simultaneously covering different levels of biological organisation (here referred to as biological levels) as well as varying temporal and spatial scales. Synthesising the three perspectives, some central aspects and associated types of data seem particularly necessary to improve prediction. First, suborganism- and organism-level responses to chemicals need to be recorded and tested for relationships with chemical groups and organism traits. Second, metrics that are measurable at many biological levels, such as energy, need to be scrutinised for their potential to integrate across levels. Third, experimental data on the simultaneous response over multiple biological levels and spatiotemporal scales are required. These could be collected in nested and interconnected micro- and mesocosm experiments. Lastly, prioritisation of processes involved in the prediction framework needs to find a balance between simplification and capturing the essential complexity of a system. For example, in some cases, eco-evolutionary dynamics and interactions may need stronger consideration. Prediction needs to move from a static to a real-world eco-evolutionary view.

Ocean acidification and seasonal temperature extremes combine to impair the thermal physiology of a sub-Antarctic fish

To predict the potential impacts of climate change on marine organisms, it is critical to understand how multiple stressors constrain the physiology and distribution of species. We evaluated the effects of seasonal changes in seawater temperature and near-future ocean acidification (OA) on organismal and sub-organismal traits associated with the thermal performance of Eleginops maclovinus, a sub-Antarctic notothenioid species with economic importance to sport and artisanal fisheries in southern South America. Juveniles were exposed to mean winter and summer sea surface temperatures (4 and 10 °C) at present-day and near-future pCO2 levels (~500 and 1800 μatm). After a month, the Critical Thermal maximum and minimum (CTmax, CTmin) of fish were measured using the Critical Thermal Methodology and the aerobic scope of fish was measured based on the difference between their maximal and standard rates determined from intermittent flow respirometry. Lipid peroxidation and the antioxidant capacity were also quantified to estimate the oxidative damage potentially caused to gill and liver tissue. Although CTmax and CTmin were higher in individuals acclimated to summer versus winter temperatures, the increase in CTmax was minimal in juveniles exposed to the near-future compared to present-day pCO2 levels (there was a significant interaction between temperature and pCO2 on CTmax). The reduction in the thermal tolerance range under summer temperatures and near-future OA conditions was associated with a reduction in the aerobic scope observed at the elevated pCO2 level. Moreover, an oxidative stress condition was detected in the gill and liver tissues. Thus, chronic exposure to OA and the current summer temperatures pose limits to the thermal performance of juvenile E. maclovinus at the organismal and sub-organismal levels, making this species vulnerable to projected climate-driven warming.