Posts Tagged 'toxicants'

Acclimation history modulates effect size of calcareous algae (Halimeda opuntia) to herbicide exposure under future climate scenarios


•Calcifying algae were exposed to herbicide and future climate scenarios combined.

•Half of the algae were given long acclimation to future climate-change conditions.

•Experimental effects were exaggerated for algae that were not acclimated.

•Still, herbicide effects on acclimated algae stronger in future climate conditions

•Results show the need of climate-adjusted thresholds for water quality guidelines.


Tropical marine habitat-builders such as calcifying green algae can be susceptible to climate change (warming and acidification). This study evaluated the cumulative effects of ocean warming (OW), ocean acidification (OA) and the herbicide diuron on the calcifying green algae Halimeda opuntia. We also assessed the influence of acclimation history to experimental climate change conditions on physiological responses. H. opuntia were exposed for 15 days to orthogonal combinations of three climate scenarios [ambient (28 °C, pCO2 = 378 ppm), 2050 (29 °C, pCO2 = 567 ppm) and 2100 (30 °C, pCO2 = 721 ppm)] and to six diuron concentrations (up to 29 μg L−1). Half of the H. opuntia had been acclimated for eight months to the climate scenarios in a mesocosm approach, while the remaining half were not pre-acclimated, as is current practice in most experiments. Climate effects on quantum yield (ΔF/Fm′), photosynthesis and calcification in future climate scenarios were significantly stronger (by −24, −46 and +26%, respectively) in non-acclimated algae, suggesting experimental bias may exaggerate effects in organisms not appropriately acclimated to future-climate conditions. Thus, full analysis was done on acclimated plants only. Interactive effects of future climate scenarios and diuron were observed for ΔF/Fm′, while the detrimental effects of climate and diuron on net photosynthesis and total antioxidant capacity (TAC) were additive. Calcification-related enzymes were negatively affected only by diuron, with inhibition of Ca-ATPase and upregulation of carbonic anhydrase. The combined and consistent physiological and biochemical evidence of negative impacts (across six indicators) of both herbicide and future-climate conditions on the health of H. opuntia highlights the need to address both climate change and water quality. Guideline values for contaminants may also need to be lowered considering ‘climate adjusted thresholds’. Importantly, this study highlights the value of applying substantial future climate acclimation periods in experimental studies to avoid exaggerated organism responses to OW and OA.

Continue reading ‘Acclimation history modulates effect size of calcareous algae (Halimeda opuntia) to herbicide exposure under future climate scenarios’

The influence of plastic pollution and ocean change on detrital decomposition


•The combined effects of plastic pollution, ocean warming, and acidification on macrophyte decomposition were tested.

•High quantities of plastic slowed the decomposition of seagrass and kelp.

•Ocean warming increased the decomposition rates of seagrass and kelp.

•Ocean acidification did not significantly influence macrophyte decomposition.

•Reducing plastic pollution and CO2 emissions is likely the best approach for preserving detritus-based ecosystem processes.


Plastic pollution and ocean change have mostly been assessed separately, missing potential interactions that either enhance or reduce future impacts on ecosystem processes. Here, we used manipulative experiments with outdoor mesocosms to test hypotheses about the interactive effects of plastic pollution, ocean warming and acidification on macrophyte detrital decomposition. These experiments focused on detritus from kelp, Ecklonia radiata, and eelgrass, Zostera muelleri, and included crossed treatments of (i) no, low and high plastic pollution, (ii) current/future ocean temperatures, and (iii) ambient/future ocean partial pressure of carbon dioxide (pCO2). High levels of plastic pollution significantly reduced the decomposition rate of kelp and eelgrass by approximately 27% and 36% in comparison to controls respectively. Plastic pollution also significantly slowed the nitrogen liberation from seagrass and kelp detritus. Higher seawater temperatures significantly increased the decomposition rate of kelp and eelgrass by 12% and 5% over current conditions, respectively. Higher seawater temperatures were also found to reduce the nitrogen liberation in eelgrass. In contrast, ocean acidification did not significantly influence the rate of macrophyte decomposition or nutrient liberation. Overall, our results show how detrital processes might respond to increasing plastic pollution and ocean temperatures, which has implications for detrital-driven secondary productivity, nutrient dynamics and carbon cycling.

Continue reading ‘The influence of plastic pollution and ocean change on detrital decomposition’

Abalone populations are most sensitive to environmental stress effects on adult individuals

Marine organisms are exposed to stressors associated with climate change throughout their life cycle, but a majority of studies focus on responses in single life stages, typically early ones. Here, we examined how negative impacts from stressors associated with climate change, ocean acidification, and pollution can act across multiple life stages to influence long-term population dynamics and decrease resilience to mass mortality events. We used a continuous-size-structured density-dependent model for abalone (Haliotis spp.), calcifying mollusks that support valuable fisheries, to explore the sensitivity of stock abundance and annual catch to potential changes in growth, survival, and fecundity across the organism’s lifespan. Our model predicts that decreased recruitment from lowered fertilization success or larval survival has small negative impacts on the population, and that stock size and fishery performance are much more sensitive to changes in parameters that affect the size or survival of adults. Sensitivity to impacts on subadults and juveniles is also important for the population, though less so than for adults. Importantly, likelihood of recovery following mortality events showed more pronounced sensitivity to most possible parameter impacts, greater than the effects on equilibrium density or catch. Our results suggest that future experiments on environmental stressors should focus on multiple life stages to capture effects on population structure and dynamics, particularly for species with size-dependent fecundity.

Continue reading ‘Abalone populations are most sensitive to environmental stress effects on adult individuals’

Exposure to pet-made microplastics: Particle size and pH effects on biomolecular responses in mussels


•PET-MPs are able to induce biochemical stress in mussels.

•LPO and GPx were more effective in detecting the PET-MPs induced stress.

•Biomarkers expression was influenced by the size of PET-MPs.

•L-PET-MPs (0.5–3.0 mm) induced grater effect than other sizes.

•Interaction was recorded among PET-MPs sizes and initial pH (8.0–7.5 units).


This study aims to evaluate the expression of biomarkers of oxidative stress (LPO, GPx, AtCh, SOD) in mussels (Mytilus galloprovincialis) following the exposure to suspensions of microparticles irregular shaped fibres of Polyethylene terephthalate of different sizes (small 5–60 μm, S-PET; medium 61–499 μm, M-PET; large 500–3000 μm, L-PET) at a single dose of 0.1 g/L. Mussels were tested under two different starting pH conditions of marine water: standard (8.0) and acidified (7.5). The results obtained from this study show that: i) PET microplastics are able to induce biochemical stress in mussels; ii) among the biomarkers tested, LPO and GPx were more effective in detecting the stress induced by microplastic in both initial pH conditions; iii) the expression of biomarkers was influenced by the size of the microparticle. In particular, greater effects were associated with the largest PET particle tested (0.5–3.0 mm); iv) regarding the effect of pH, in experiments starting from 7.5 pH the animals showed a lower biomarker expression than those starting from 8.0 pH.

Continue reading ‘Exposure to pet-made microplastics: Particle size and pH effects on biomolecular responses in mussels’

Effects of pH on salicylic acid toxicity in terms of biomarkers determined in the marine gastropod Gibbula umbilicalis


• Physiological alterations were enhanced under SA exposure at lower pH levels.

• Lipid peroxidation increased after seawater acidification.

• Neurotoxic effects were reported under SA exposure.

• Prostaglandins biosynthesis pathway inhibited by SA absorption at lower pH levels.


Alterations of the physical-chemical properties of the oceans due to anthropogenic activities are, at present, one of the most concerning environmental issues studied by researchers. One of these issues is ocean acidification, mainly caused by overproduction and release of carbon dioxide (CO2) from anthropogenic sources. Another component of environmental degradation is related to the production and release of potential toxic compounds, namely active pharmaceutical ingredients, into the aquatic environment that, combined with oceanic acidification, can cause unpredictable and never before considered deleterious effects on non-target marine organisms. Regarding this issue, the hereby study used predictions of future ocean acidification to simulate realistic scenarios of environmental exposure to a common therapeutic drug, salicylic acid (SA), in the marine gastropod Gibbula umbilicalis under different pH values. This species was exposed to a range of pH values (8.2, 7.9 and 7.6), and to already reported environmentally realistic concentrations (5, 25 and 125 μg/L) of SA. To evaluate the effects of these environmental stressors, key physiological biomarkers (GSTs, CAT, TBARS, AChE and COX) and shell hardness (SH) were quantified. Results from the present study showed that CAT and GSTs activities were enhanced by SA under water acidification; increased lipid peroxidation was also observed in organisms exposed to SA in more acidic media. In addition, the hereby study demonstrated the neurotoxic effects of SA through the inhibition of AChE. Effects were also observed in terms of COX activity, showing that SA absorption may be affected by water acidification. In terms of SH, the obtained data suggest that SA may alter the physical integrity of shells of exposed organisms. It is possible to conclude that the combination of seawater acidification and exposure to toxic xenobiotics (namely to the drug SA) may be strenuous to marine communities, making aquatic biota more susceptible to xenobiotics, and consequently endangering marine life in an unpredictable extent.

Continue reading ‘Effects of pH on salicylic acid toxicity in terms of biomarkers determined in the marine gastropod Gibbula umbilicalis’

Exposure to decreased pH and caffeine affects hemocyte parameters in the mussel Mytilus galloprovincialis

Combined effects of reduced pH, as predicted under climate change scenarios, and the most popular and widely used stimulant caffeine were assessed in hemocyte parameters of the mussel Mytilus galloprovincialis, being hemocytes involved in immune defense. Bivalves were exposed for one week to natural pH (8.1) and two reduced pH values (pH -0.4 units and pH -0.7 units). Exposure continued for additional two weeks, both in the absence and in the presence of environmentally relevant concentrations of caffeine (0.05 and 0.5 µg/L). Hemocyte parameters (total hemocyte count, hemocyte volume and diameter, neutral red uptake and hemocyte proliferation) were measured after 7 days of exposure to pH only, and after 14 (T1) and 21 (T2) days of exposure to the various pH*caffeine combinations. At all sampling times, pH significantly affected all the biological variables considered, whereas caffeine exhibited a significant influence at T2 only. Among the various hemocyte parameters, caffeine caused a significant increase in total hemocyte count at T2, and in hemocyte volume and diameter at both T1 and T2, when a significant interaction between pH and caffeine was also found. Overall, results demonstrated that hemocyte functionality was strongly influenced by the experimental conditions tested. Further studies are needed to assess combined effects of climate changes and emerging contaminants on bivalve immune system when challenged with environmental pathogens.

Continue reading ‘Exposure to decreased pH and caffeine affects hemocyte parameters in the mussel Mytilus galloprovincialis’

Biochemical and physiological responses of two clam species to Triclosan combined with climate change scenario


• Triclosan bioaccumulation was enhanced under forecasted climate change conditions.

• Triclosan strongly affected clams’ antioxidant defences.

• Cellular damage was prevented by enzymatic and behaviour defence mechanisms.

• Greater response of the Manila clam to TCS exposure combined with climate change scenario.


Ocean acidification and warming are among the man-induced factors that most likely impact aquatic wildlife worldwide. Besides effects caused by temperature rise and lowered pH conditions, chemicals of current use can also adversely affect aquatic organisms. Both climate change and emerging pollutants, including toxic impacts in marine invertebrates, have been investigated in recent years. However, less information is available on the combined effects of these physical and chemical stressors that, in nature, occur simultaneously. Thus, this study contrasts the effects caused by the antimicrobial agent and plastic additive, Triclosan (TCS) in the related clams Ruditapes philippinarum (invasive) and Ruditapes decussatus (native) and evaluates if the impacts are influenced by combined temperature and pH modifications. Organisms were acclimated for 30 days at two conditions (control: 17 °C; pH 8.1 and climate change scenario: 20 °C, pH 7.7) in the absence of the drug (experimental period I) followed by a 7 days exposure under the same water physical parameters but either in absence (unexposed) or presence of TCS at 1 μg/L (experimental period II). Biochemical responses covering metabolic, oxidative defences and damage-related biomarkers were contrasted in clams at the end of experimental period II. The overall picture showed a well-marked antioxidant activation and higher TCS bioaccumulation of the drug under the forecasted climate scenario despite a reduction on respiration rate and metabolism in the exposed clams. Since clams are highly consumed shellfish, the consequences for higher tissue bioaccumulation of anthropogenic chemicals to final consumers should be alerted not only at present conditions but more significantly under predicted climatic conditions for humans but also for other components of the marine trophic chain.

Continue reading ‘Biochemical and physiological responses of two clam species to Triclosan combined with climate change scenario’

Cold-water coral (Lophelia pertusa) response to multiple stressors: high temperature affects recovery from short-term pollution exposure

There are numerous studies highlighting the impacts of direct and indirect stressors on marine organisms, and multi-stressor studies of their combined effects are an increasing focus of experimental work. Lophelia pertusa is a framework-forming cold-water coral that supports numerous ecosystem services in the deep ocean. These corals are threatened by increasing anthropogenic impacts to the deep-sea, such as global ocean change and hydrocarbon extraction. This study implemented two sets of experiments to assess the effects of future conditions (temperature: 8 °C and 12 °C, pH: 7.9 and 7.6) and hydrocarbon exposure (oil, dispersant, oil + dispersant combined) on coral health. Phenotypic response was assessed through three independent observations of diagnostic characteristics that were combined into an average health rating at four points during exposure and recovery. In both experiments, regardless of environmental condition, average health significantly declined during 24-hour exposure to dispersant alone but was not significantly altered in the other treatments. In the early recovery stage (24 hours), polyp health returned to the pre-exposure health state under ambient temperature in all treatments. However, increased temperature resulted in a delay in recovery (72 hours) from dispersant exposure. These experiments provide evidence that global ocean change can affect the resilience of corals to environmental stressors and that exposure to chemical dispersants may pose a greater threat than oil itself.

Continue reading ‘Cold-water coral (Lophelia pertusa) response to multiple stressors: high temperature affects recovery from short-term pollution exposure’

The effects of co-exposure of graphene oxide and copper under different pH conditions in Manila clam Ruditapes philippinarum

Carbon nanomaterials (CNM), such as graphene oxide (GO), have been the focus of study in several areas of science mostly due to their physical-chemical properties. However, data concerning the potential toxic effects of these CNM in bivalves are still scarce. When present in the aquatic systems, the combination with other contaminants, as well as pH environmental variations, can influence the behavior of these nanomaterials and, consequently, their toxicity. Thus, the main goal of this study was to evaluate the effect of exposure of clam Ruditapes philippinarum to GO when acting alone and in the combination with copper (Cu), under two pH levels (control 7.8 and 7.3). A 28-day exposure was performed and metabolism and oxidative stress-related parameters were evaluated. The effects caused by GO and Cu exposures, either isolated or co-exposed, showed a direct and dependent relationship with the pH in which the organisms were exposed. In clams maintained at control pH (7.8), Cu and GO + Cu treatments showed lower lipid peroxidation (LPO) and lower electron transport system (ETS) activity, respectively. In clams maintained at low pH, glutathione-S-transferases (GSTs) activities were increased in Cu and Cu + GO treatments, whereas reduced glutathione (GSH) levels were increased in Cu treatment and ETS activity was higher in GO + Cu. Thus, it can be observed that clams responses to Cu and GO were strongly modulated by pH in terms of their defense system and energy production, although this does not result into higher LPO levels.

Continue reading ‘The effects of co-exposure of graphene oxide and copper under different pH conditions in Manila clam Ruditapes philippinarum’

Microplastics impair digestive performance but show little effects on antioxidant activity in mussels under low pH conditions


• The immunity and digestion of mussels were impaired by MPs and OA.

• OA can enhance the toxicity of MPs to mussels.

• Digestion was more severely affected by OA and MPs than antioxidant system.

• The negative effects on PES and AMS showed a reversible trend.


In the marine environment, microplastic contamination and acidification may occur simultaneously, this study evaluated the effects of ocean acidification and microplastics on oxidative stress responses and digestive enzymes in mussels. The thick shell mussels Mytilus coruscus were exposed to four concentrations of polystyrene microspheres (diameter 2 μm, 0, 10, 104 and 106 particles/L) under two pH levels (7.7 and 8.1) for 14 days followed by a 7-day recovery acclimation. Throughout the experiment, we found that microplastics and ocean acidification exerted little oxidative stress to the digestive gland. Only catalase (CAT) and glutathione (GSH) showed a significant increase along with increased microplastics during the experiment, but recovered to the control levels once these stressors were removed. No significant effects of pH and microplastics on glutathione peroxidase (GPx) and superoxide dismutase (SOD) were observed. The responses of digestive enzymes to both stressors were more pronounced than antioxidant enzymes. During the experiment, pepsin (PES), trypsin (TRS), alpha-amylase (AMS) and lipase (LPS) were significantly inhibited under microplastics exposure and this inhibition was aggravated by acidification conditions. Only PES and AMS tended to recover during the recovery period. Lysozyme (LZM) increased significantly under microplastic exposure conditions, but acidification did not exacerbate this effect. Therefore, combined stress of microplastics and ocean acidification slightly impacts oxidative responses but significantly inhibits digestive enzymes in mussels.

Continue reading ‘Microplastics impair digestive performance but show little effects on antioxidant activity in mussels under low pH conditions’

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Ocean acidification in the IPCC AR5 WG II

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