Ocean acidification (OA) is expected to rise towards the end of the 21st century altering the life history traits in marine organisms. Upwelling systems will not escape OA, but unlike other areas of the ocean, cooling effects are expected to intensify in these systems. Regardless, studies evaluating the combined effects of OA and cooling remain scarce. We addressed this gap using a mesocosm system, where we exposed juveniles of the intertidal muricid snail Acanthina monodon to current and projected pCO₂ (500 vs. 1500 ppm) and temperature (15 vs. 10 °C) from the southeast Pacific upwelling system. After 9 weeks of experimental exposure to those conditions, we conducted three estimations of growth (wet weight, shell length and shell peristomal length), in addition to measuring calcification, metabolic and feeding rates and the ability of these organisms to return to the normal upright position after being overturned (self-righting). Growth, feeding and calcification rates increased in projected cooling conditions (10 °C) but were unaffected by pCO₂ or the interaction between pCO₂ and temperature. Instead, metabolic rates were driven by pCO₂, but a significant interaction with temperature suggests that in cooler conditions, metabolic rates will increase when associated with high pCO₂ levels. Snail self-righting times were not affected across treatments. These results suggest that colder temperatures projected for this area would drive this species growth, feeding and calcification, and consequently, some of its population biology and productivity. However, the snails may need to compensate for the increase in metabolic rates under the effects of ocean acidification. Although A. monodon ability to adjust to individual or combined stressors will likely account for some of the changes described here, our results point to a complex dynamic to take place in intertidal habitats associated with upwelling systems.

Microplastics are sometimes considered not harmful at environmentally relevant concentrations. Yet, such studies were conducted under standard thermal conditions and thereby ignored the impacts of higher mean temperatures (MT), and especially daily temperature fluctuations (DTF) under global warming. Moreover, an evolutionary perspective may further benefit the future risk assessment of microplastics under global warming. Here, we investigated the effects of two generations of exposure to an environmentally relevant concentration of polystyrene microplastics (5 μg L⁻¹) under six thermal conditions (2 MT × 3 DTF) on the life history, physiology, and behaviour of Daphnia magna. To assess the impact of thermal evolution we thereby compared Daphnia populations from high and low latitudes. At the standard ecotoxic thermal conditions (constant 20 °C) microplastics almost had no effect except for a slight reduction of the heartbeat rate. Yet, at the challenging thermal conditions (higher MT and/or DTF), microplastics affected each tested variable and caused an earlier maturation, a higher fecundity and intrinsic growth rate, a decreased heartbeat rate, and an increased swimming speed. These effects may be partly explained by hormesis and/or an adaptive response to stress in Daphnia. Moreover, exposure to microplastics at the higher mean temperature increased the fecundity and intrinsic growth rate of cold-adapted high-latitude Daphnia, but not of the warm-adapted low-latitude Daphnia, suggesting that thermal evolution in high-latitude Daphnia may buffer the effects of microplastics under future warming. Our results highlight the critical importance of DTF and thermal evolution for a more realistic risk assessment of microplastics under global warming.

Climate changes and metal contamination are pervasive stressors for soil ecosystems. Mercury (Hg), one of the most toxic metals, has been reported to interact with temperature. However, compared to aquatic biota, little is known about how temperature affects Hg toxicity and bioaccumulation to soil organisms. Here, toxicity and bioaccumulation experiments were replicated at 15 °C, 20 °C, and 25 °C to understand how sub-optimal temperatures affect the toxicokinetics and toxicodynamics of Hg via soil. Genotoxicity and energy reserves were also assessed to disclose potential trade-offs in life-history traits. Results underpin the complexity of temperature-Hg interactions. Survival was determined mainly by toxicokinetics, but toxicodynamics also played a significant role in defining survival probability during early stages. The processes determining survival probability were faster at 25 °C: General Unified Threshold of Survival (GUTS) model identified an earlier/steeper decline in survival, compared to 20 °C or 15 °C, but it also approached the threshold faster. Despite potentiation of Hg genotoxicity, temperature promoted faster detoxification, either increasing toxicokinetics rates or damage repair mechanisms. This metabolism-driven increase in detoxification led to higher depletion of energy reserves and likely triggered stress response pathways. This work emphasized the need for comprehensive experimental approaches that can integrate the multiple processes involved in temperature-metal interactions.

Biological invasions and continued salinization of freshwater are two global issues with largely serious ecological consequences. Increasing salinity in freshwater systems, as an environmental stressor, may negatively affect normal life activities in fish. It has been documented that salinity limits the invasive success of alien species by mediating physiological and life-history performances, however, there are few studies on how salinity affects its invasive process via altered behaviors. Using wild-caught invasive western mosquitofish (Gambusia affinis) as animal model, in this study, we asked whether gradual increasing salinity affects behaviors (personality and mate choice decision here), life-history traits, as well as the correlation between them by exposing G. affinis to three levels salinity (freshwater, 10 and 20‰). Results showed that, with increased salinity, male tended to be shyer, less active, less sociable, and reduced desire to mate, and female tended to be shyer, less active and lost preferences for the larger male. Furthermore, across salinity treatments, male exhibited reduced body fat content and rising reproduction allocation, however, pregnant female revealed diametrically opposed trends. In addition, the correlation between life-history traits and behaviors was only identified in pregnant female. It seems that either salinity or life-history traits directly affects mosquitofish behaviors. In summary, our results partially emphasize the harmful consequences of salinity on both life-history traits and behavioral performances. These findings provide a novel perspective on how salinity potentially affect fish fitness via altering personalities, mate choice decisions, as well as body condition, and hence supports the idea that salinity could affect the spread of invasive mosquitofish.

Species of the genus Microcystis are among the most notorious cyanobacteria in eutrophic lakes worldwide, with ability present adverse effects on many aquatic organisms. In the surface sediments, Microcystis can be ingested by benthic macroinvertebrates such as Chironomus. However, the potential negative effects of Microcystis on Chironomus life history traits remain unclear. In the present study, we investigated the effect of different Microcystis diets on specific behaviors (burrowing activity, locomotion ability) and life history traits of Chironomus pallidivittatus (Diptera, Chironomidae). We also studied the interactive effects of microcystin-producing M. aeruginosa and temperature (15, 20, and 25 °C) stress on chironomid larvae. The results showed that the inhibitory effect on the cumulative emergence and burrowing activity of larvae was more severe when they were fed M. aeruginosa among the three Microcystis diets groups. Locomotion ability (i.e., locomotor distance and velocity) and adult dry weight decreased significantly in the group fed M. aeruginosa. Locomotion was significantly inhibited and mortality increased when the larvae were fed a mixture of M. aeruginosa and M. wesenbergii, which may have been the result of additive or synergistic effect of the toxins. Under the stress of lower temperature, C. pallidivittatus larvae exhibited weaker locomotion and growth ability, and the emerging adults were mostly male. At both the lower and higher temperature conditions, M. aeruginosa cause cumulative emergence decreased, and sex ratio imbalance, which inhibited the reproduction of larvae from the population perspective. The fourth-instar larvae showed better adaption to Microcystis than did the other instars. This study thus highlights the adverse effects of microcystin-producing M. aeruginosa on Chironomus. It also provides a novel perspective on how environmental factors may influence the behavior and life history traits of chironomid larvae, and how they may respond to cyanobacterial blooms and global warming.

Pollution damages ecosystems around the globe and some forms of pollution, like oil pollution, can be either man-made or derived from natural sources. Despite the pervasiveness of oil pollution, certain organisms are able to colonise polluted or toxic environments, yet we only have a limited understanding of how they are affected by it. Here, we analysed phenotypic responses to oil pollution in guppies (Poecilia reticulata) living in oil-polluted habitats across southern Trinidad. We analysed body-shape and life-history traits for 352 individuals from 11 independent populations, six living in oil-polluted environments (including the naturally oil-polluted Pitch Lake), and five stemming from non-polluted habitats. Based on theory of, and previous studies on, responses to environmental stressors, we predicted guppies from oil-polluted waters to have larger heads and shallower bodies, to be smaller, to invest more into reproduction, and to produce more but smaller offspring compared to guppies from non-polluted habitats. Contrary to most of our predictions, we uncovered strong population-specific variation regardless of the presence of oil pollution. Moreover, guppies from oil-polluted habitats were characterised by increased body size; rounder, deeper bodies with increased head size; and increased offspring size, when compared to their counterparts from non-polluted sites. This suggests that guppies in oil-polluted environments are not only subject to the direct negative effects of oil pollution, but might gain some (indirect) benefits from other concomitant environmental factors, such as reduced predation and reduced parasite load. Our results extend our knowledge of organismal responses to oil pollution and highlight the importance of anthropogenic pollution as a source of environmental variation. They also emphasise the understudied ecological heterogeneity of extreme environments.

Microplastics (<5 mm) are ubiquitous in the global environment and are increasingly recognized as a biological hazard, particularly in the oceans. Zooplankton, at the base of the marine food web, have been known to consume microplastics. However, we know little about the impacts of microplastics across life history stages and on carbon settling. Here, we investigated the effects of ingestion of neutrally buoyant polystyrene beads (6.68 μm) by the copepod Acartia tonsa on (1) growth and survival across life history stages, (2) fecundity and egg quality, (3) and fecal characteristics. We found that microplastic exposure reduced body length and survival for nauplii and resulted in smaller eggs when copepods were exposed during oogenesis. Combining these life history impacts, our models estimate a 15% decrease in population growth leading to a projected 30-fold decrease in abundance over 1 year or 20 generations with microplastic exposure. In addition, microplastic-contaminated fecal pellets were 2.29-fold smaller and sinking rates were calculated to be 1.76-fold slower, resulting in an estimated 4.03-fold reduction in fecal volume settling to the benthos per day. Taken together, declines in population sizes and fecal sinking rates suggest that microplastic consumption by zooplankton could have cascading ecosystem impacts via reduced trophic energy transfer and slower carbon settling.

There is growing evidence of widespread contamination of freshwater ecosystems with microplastics. However, the effects of chronic microplastic ingestion and its interaction with other pollutants and stress factors on the life-history traits and the host-microbiome of aquatic invertebrates are not well understood. This study investigates the effects of exposure to sediment spiked with 1 μm polystyrene-based latex microplastic spheres, an environmentally realistic concentration of a pyrethroid pesticide (esfenvalerate), and a combination of both treatments on the life-history traits of the benthic-dwelling invertebrate, Chironomus riparius and its microbial community. The chironomid larvae were also exposed to two food conditions: abundant or limited food in the sediment, monitored for 28 and 34 days respectively. The microplastics and esfenvalerate had negative effects on adult emergence and survival, and these effects differed between the food level treatments. The microbiome diversity was negatively affected by the exposure to microplastics, while the relative abundances of the four top phyla were significantly affected only in the high food level treatment. Although the combined exposure to microplastics and esfenvalerate showed some negative effects on survival and emergence, there was little evidence for synergistic effects when compared to the single exposure. The food level affected all life-history traits and the microbiota, and lower food levels intensified the negative effects of the exposure to microplastics, esfenvalerate and their combination. We argue that these pollutants can affect crucial life-history traits such as successful metamorphosis and the host-microbiome. Therefore, it should be taken into consideration for toxicological assessment of pollutant acceptability. Our study highlights the importance of investigating possible additive and synergic activities between stressors to understand the effects of pollutants in the life story traits and host-microbiome.

Environmental emissions of perfluoroalkyl acids (PFAAs) often contaminate aquatic ecosystems and accumulate in the species therein. This can represent an exposure pathway for human populations where seafood is consumed. Concentrations of PFAAs in water breathing animals may be a function of many different factors, however, little is known about how these different factors impact contaminant accumulation in estuarine and marine species. This study explores the relationships between PFAA accumulation and two key variables, animal size and sediment concentrations, for a number of important seafood species. Sixty Dusky Flathead (Platycephalus fuscus), 58 Mulloway (Argyrosomus japonicus) and 53 Giant Mud Crab (Scylla serrata) were tested for perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexane sulfonate (PFHxS) in edible tissues, and the concentrations compared with animal size and sediment concentrations at the location of capture. PFAAs showed a high degree of variation among species, and PFOA and PFHxS were only common in Giant Mud Crab. Log-transformed PFOS concentrations in all three species showed negative correlations with animal size (weight). There was limited evidence for relationships between PFOS muscle tissue concentration and sediment PFOS concentration. The patterns observed are potentially explained by changes in trophic position, relative growth rate, consumption rate and metabolic rate, throughout the species life history. The results contrast with observations for other persistent organic pollutants, whereby larger individuals tend to carry greater contaminant loads. Future work is required to establish whether these patterns are evident for PFAAs in other species and contaminant sources.

Cyanobacterial blooms are an increasing problem in a more eutrophic world. It is still a challenge to fully understand the influence of cyanobacteria on the interactions between predator and prey at higher trophic levels. The present study was mainly undertaken to understand the inducible anti-predator responses of cladocerans while using cyanobacteria as part of food. Specifically speaking, we focused on the anti-predator strategies of Ceriodaphnia cornuta in response to different predators (fish and Chaoborus larvae) under food with different proportions of Microcystis aeruginosa. The morphological (i.e., body size and the induction of horns) and life history traits (e.g., time to first reproduction, offspring number, and survival time) responses were measured under different proportions of M. aeruginosa (i.e., 0%, 20%, 40%, 60%, 80%, and 100%). Our results showed that both the life history and the inducible anti-predator responses of C. cornuta were significantly affected by different concentrations of M. aeruginosa. Specifically, lower concentrations of Microcystis (20%–60%) can significantly promote the horns induction under Chaoborus predation risks, and higher Microcystis concentrations (60%–100%) tend to enhance reproduction in response to fish predation risks, such as larger body size, decreased time to first reproduction, and increased total offspring number. Additionally, an increasing concentration of M. aeruginosa decreased the ability of C. cornuta to reverse horns when predation risks removed. Our findings indicated that cyanobacteria affecting life history traits and the subsequent indirect effects on anti-predator responses in cladocerans could impact the interactions between predator and prey at higher trophic levels and may consequently contribute to shaping the structure of the community in a cyanobacteria bloom area.