Posts Tagged 'toxicants'

Living in a multi-stressors environment: an integrated biomarker approach to assess the ecotoxicological response of meagre (Argyrosomus regius) to venlafaxine, warming and acidification

Highlights
• VFX toxicity was influenced by exposure route, as well as by abiotic stressors
• VFX water exposure induced more severe biomarker responses than VFX feed exposure
• Muscle, liver and brain biomarker responses were significantly affected by warming
• Biomarker changes due to acidification were more evident in fish gills
• The combination of the three stressors simultaneously increased stress severity
• The importance of assessing potential interaction between stressors was evidenced

Abstract
Pharmaceuticals, such as the antidepressant venlafaxine (VFX), have been frequently detected in coastal waters and marine biota, and there is a growing body of evidence that these pollutants can be toxic to non-target marine biota, even at low concentrations. Alongside, climate change effects (e.g. warming and acidification) can also affect marine species’ physiological fitness and, consequently, compromising their ability to cope with the presence of pollutants. Yet, information regarding interactive effects between pollutants and climate change-related stressors is still scarce. Within this context, the present study aims to assess the differential ecotoxicological responses (antioxidant activity, heat shock response, protein degradation, endocrine disruption and neurotoxicity) of juvenile fish (Argyrosomus regius) tissues (muscle, gills, liver and brain) exposed to VFX (via water or feed), as well as to the interactive effects of warming (ΔT°C = +5 °C) and acidification (ΔpCO2 ~ +1000 µatm, equivalent to ΔpH = −0.4 units), using an integrated multi-biomarker response (IBR) approach.

Overall, results showed that VFX toxicity was strongly influenced by the uptake pathway, as well as by warming and acidification. More significant changes (e.g. increases surpassing 100% in lipid peroxidation, LPO, heat shock response protein content, HSP70/HSC70, and total ubiquitin content, Ub,) and higher IBR index values were observed when VFX exposure occurred via water (i.e. average IBR = 19, against 17 in VFX-feed treatment). The co-exposure to climate change-related stressors either enhanced (e.g. glutathione S-transferases activity (GST) in fish muscle was further increased by warming) or attenuated the changes elicited by VFX (e.g. vitellogenin, VTG, liver content increased with VFX feed exposure acting alone, but not when co-exposed with acidification). Yet, increased stress severity was observed when the three stressors acted simultaneously, particularly in fish exposed to VFX via water (i.e. average IBR = 21). Hence, the distinct fish tissues responses elicited by the different scenarios emphasized the relevance of performing multi-stressors ecotoxicological studies, as such approach enables a better estimation of the environmental hazards posed by pollutants in a changing ocean and, consequently, the development of strategies to mitigate them.

Continue reading ‘Living in a multi-stressors environment: an integrated biomarker approach to assess the ecotoxicological response of meagre (Argyrosomus regius) to venlafaxine, warming and acidification’

The health risk for seafood consumers under future ocean acidification (OA) scenarios: OA alters bioaccumulation of three pollutants in an edible bivalve species through affecting the in vivo metabolism

Highlights

• OA increased B[a]P accumulation in blood clams.
• OA decreased the accumulation of NFZ and CAP in blood clams.
• Health risks increased for B[a]P but not for NFZ & CAP.
• Changes in accumulation may be due to altered eliminating ability.

Abstract

The current knowledge about the effect of pCO2-driven ocean acidification on the bioaccumulation of pollutants in marine species is still scarce, as only limited types of pollutants have been investigated. Therefore, to obtain a better understanding of the effect of ocean acidification on the process of bioaccumulation and subsequent food safety, the accumulation of benzo[a]pyrene (B[a]P), chloramphenicol (CAP), and nitrofurazone (NFZ) in an edible bivalve species, Tegillarca granosa, under present and near-future ocean acidification scenarios was investigated in the present study. The health risks associated with consuming contaminated blood clams were also assessed using target hazard quotient (THQ), lifetime cancer risk (CR), or margin of exposure (MoE). To explain the alterations in bioaccumulation of these pollutants, the expressions of genes encoding corresponding key metabolic proteins were analyzed as well. The results obtained showed that ocean acidification exerted a significant effect on the accumulation of B[a]P, NFZ, and CAP in the clams. After four-week exposure to B[a]P, NFZ, or CAP contaminated seawater acidified with CO2 at pH 7.8 and 7.4, significantly greater amounts of B[a]P and lower amounts of NFZ and CAP were accumulated in the clams compared to that in the control. Although no non-carcinogenic risk of consuming B[a]P-contaminated blood clams was detected using the THQ values obtained, the CR values obtained indicated a high life-time risk in all groups. In addition, according to the MoE values obtained, the health risks in terms of consuming NFZ- and CAP-contaminated clams were significantly reduced under ocean acidification scenarios but still cannot be ignored, especially for children. The gene expression results showed that the ability of clams to eliminate B[a]P may be significantly constrained, whereas the ability to eliminate NFZ and CAP may be enhanced under ocean acidification scenarios, indicating that the changes in the accumulation of these pollutants may be due to the altered in vivo metabolism.

Continue reading ‘The health risk for seafood consumers under future ocean acidification (OA) scenarios: OA alters bioaccumulation of three pollutants in an edible bivalve species through affecting the in vivo metabolism’

Development of the sea urchin Heliocidaris crassispina from Hong Kong is robust to ocean acidification and copper contamination

Highlights

• Ocean acidification will increase the fraction of the most toxic form of copper, increasing its bioavailability to marine organisms
• We tested the hypothesis that copper contaminated waters are more toxic to sea urchin larvae under future pH conditions in three laboratory experiments
• Larvae are robust to the pH and the copper levels we tested (little/no mortality)
• However, significant sub-lethal effects, could have indirect consequences on survival

Abstract

Metallic pollution is of particular concern in coastal cities. In the Asian megacity of Hong Kong, despite water qualities have improved over the past decade, some local zones are still particularly affected and could represent sinks for remobilization of labile toxic species such as copper. Ocean acidification is expected to increase the fraction of the most toxic form of copper (Cu2+) by 2.3-folds by 2100 (pH ≈7.7), increasing its bioavailability to marine organisms. Multiple stressors are likely to exert concomitant effects (additive, synergic or antagonist) on marine organisms.

Here, we tested the hypothesis that copper contaminated waters are more toxic to sea urchin larvae under future pH conditions. We exposed sea urchin embryos and larvae to two low-pH and two copper treatments (0.1 and 1.0 μM) in three separate experiments. Over the short time typically used for toxicity tests (up to 4-arm plutei, i.e. 3 days), larvae of the sea urchin Heliocidaris crassispina were robust and survived the copper levels present in Hong Kong waters today (≤0.19 μM) as well as the average pH projected for 2100. We, however, observed significant mortality with lowering pH in the longer, single-stressor experiment (Expt A: 8-arm plutei, i.e. 9 days). Abnormality and arm asymmetry were significantly increased by pH or/and by copper presence (depending on the experiment and copper level). Body size (d3; but not body growth rates in Expt A) was significantly reduced by both lowered pH and added copper. Larval respiration (Expt A) was doubled by a decrease at pHT from 8.0 to 7.3 on d6. In Expt B1.0 and B0.1, larval morphology (relative arm lengths and stomach volume) were affected by at least one of the two investigated factors.

Although the larvae appeared robust, these sub-lethal effects may have indirect consequences on feeding, swimming and ultimately survival. The complex relationship between pH and metal speciation/uptake is not well-characterized and further investigations are urgently needed to detangle the mechanisms involved and to identify possible caveats in routinely used toxicity tests.

Continue reading ‘Development of the sea urchin Heliocidaris crassispina from Hong Kong is robust to ocean acidification and copper contamination’

Impacts of the combined exposure to seawater acidification and arsenic on the proteome of Crassostrea angulata and Crassostrea gigas

Highlights

• Different modes of action were observed in C. angulata and C. gigas exposed to different stressors.
• Combined exposures induced lower response capacity than single exposures.
• Species developed different modes of action in response to each stressor.

Abstract

Proteomic analysis was performed to compare the effects of Arsenic (As), seawater acidification (Low pH) and the combination of both stressors (Low pH + As) on Crassostrea angulata and Crassostrea gigas juveniles in the context of global environmental change. This study aimed to elucidate if two closely related Crassostrea species respond similarly to these environmental stressors, considering both single and combined exposures, to infer if the simultaneous exposure to both stressors induced a differentiated response. Identification of the most important differentially expressed proteins between conditions revealed marked differences in the response of each species towards single and combined exposures, evidencing species-related differences towards each experimental condition. Moreover, protein alterations observed in the combined exposure (Low pH + As) were substantially different from those observed in single exposures. Identified proteins and their putative biological functions revealed an array of modes of action in each condition. Among the most important, those involved in cellular structure (Actin, Atlastin, Severin, Gelsolin, Coronin) and extracellular matrix modulation (Ependymin, Tight junction ZO-1, Neprilysin) were strongly regulated, although in different exposure conditions and species. Data also revealed differences regarding metabolic modulation capacity (ATP β, Enolase, Aconitate hydratase) and oxidative stress response (Aldehyde dehydrogenase, Lactoylglutathione, Retinal dehydrogenase) of the species, which also depended on single or combined exposures, illustrating a different response capacity of both oyster species to the presence of multiple stressors. Interestingly, alterations of piRNA abundance in C. angulata suggested genome reconfiguration in response to multiple stressors, likely an important mode of action related to adaptive evolution mechanisms previously unknown to oyster species, which requires further investigation. Our findings provide a deeper insight into the complexity of C. angulata and C. gigas responses to environmental stress at the proteome level, evidencing different capacities to endure abiotic changes, with relevance regarding the ecophysiological fitness of the species and competitive advantages in a changing environment.

Continue reading ‘Impacts of the combined exposure to seawater acidification and arsenic on the proteome of Crassostrea angulata and Crassostrea gigas’

Copper and ocean acidification interact to lower maternal investment, but have little effect on adult physiology of the Sydney rock oyster Saccostrea glomerata

Highlights

• The first study to investigate the transgenerational carry-over effects of ocean acidification and trace metals.
• Ocean acidification and trace metals interact to lower the energy invested in offspring.
• Offspring of exposed parents perform better than those without exposure.

Abstract

It remains unknown how molluscs will respond to oceans which are increasingly predicted to be warmer, more acidic, and heavily polluted. Ocean acidification and trace metals will likely interact to increase the energy demands of marine organisms, especially oysters. This study tested the interactive effect of exposure to elevated pCO2 and copper on the energetic demands of the Sydney rock oyster (Saccostrea glomerata) during reproductive conditioning and determined whether there were any positive or negative effects on their offspring. Oysters were exposed to elevated pCO2 (1000 μatm) and elevated copper (Cu 50 μg L−1 [0.787 μM]) in an orthogonal design for eight weeks during reproductive conditioning. After eight weeks, energetic demands on oysters were measured including standard metabolic rate (SMR), nitrogen excretion, molar oxygen to nitrogen (O:N) ratio, and pHe of adult oysters as well as the size and total lipid content of their eggs. To determine egg viability, the gametes were collected and fertilised from adult oysters, the percentage of embryos that had reached the trochophore stage after 24 h was recorded. Elevated pCO2 caused a lower extracellular pH and there was a greater O:N ratio in adult oysters exposed to copper. While the two stressors did not interact to cause significant effects on adult physiology, they did interact to reduce the size and lipid content of eggs indicating that energy demand on adult oysters was greater when both elevated pCO2 and copper were combined. Despite the lower energy, there were no negative effects on early embryonic development. In conclusion, elevated pCO2 can interact with metals and cause greater energetic demands on oysters; in response oysters may lower maternal investment to offspring.

Continue reading ‘Copper and ocean acidification interact to lower maternal investment, but have little effect on adult physiology of the Sydney rock oyster Saccostrea glomerata’

The impact of ocean acidification and cadmium on the immune responses of Pacific oyster, Crassostrea gigas

Highlights

•  Inhibited phagocytosis rate, combined with increased DNA damage, apoptosis rate and ROS production of hemocytes were observed in oysters under exposure to Cd exposure alone or combined with OA.
•  Significant interactive effects between OA and Cd were observed on ROS production and DNA damage of hemocytes.
•  mRNA expression of genes related to immune responses (TLR pathway and immune factors) was stimulated in oysters exposed to Cd and OA at pH 7.6.

Abstract

Seawater acidification (OA) and cadmium (Cd) has the potential to lead to immunosuppression effect on marine bivalves. However, the interaction between these two environmental stressors on immune system of marine bivalves has received limited attention. In order to evaluate the defense responses of oysters under the combined exposure to OA and cadmium, the oysters Crassostrea gigas were exposed to 10 μg/L Cd at three pH levels (8.1, 7.8 and 7.6) for 31 days. Results showed that OA exposure alone led to increased DNA damage, apoptosis rate and ROS production of hemocytes. However, inhibited phagocytosis rate, combined with increased DNA damage, apoptosis rate and ROS production of hemocytes were observed in oysters under exposure to Cd exposure alone or combined with OA. Significant interactive effects between OA and Cd were observed on ROS production and DNA damage of hemocytes. In addition, there is generally significant increase in the mRNA expression of genes related to immune-related TLR pathway and two immune factors (TNF and integrin beta-1B) in Cd-exposed oysters at pH 7.6. The results revealed that even though the mRNA expression of genes related to immune responses (TLR pathway and immune factors) was stimulated to counteract the immunosuppression caused by acidified seawater and Cd, depressed hemocyte function perhaps sensitized oysters to potential pathogen infection.

Continue reading ‘The impact of ocean acidification and cadmium on the immune responses of Pacific oyster, Crassostrea gigas’

Physiological responses of corals to ocean acidification and copper exposure

Highlights

  • Differences in copper accumulation and sensitivity were observed between coral species and between coral and zooxanthellae
  • Increased CO2 did not influence copper accumulation
  • Synergistic effects from combined CO2 and copper exposure were observed in corals
  • Altered enzyme activity was observed in both coral exposed to copper or CO2
  • A. cervicornis was more affected by copper and P. damicornis was more affected by increased CO2

Abstract

Acidification and land-based sources of pollution have been linked to widespread declines of coral cover in coastal reef ecosystems. In this study, two coral species, Acropora cervicornis and Pocillopora damicornis were exposed to increased copper at two CO2 levels for 96 h. Copper accumulation and anti-oxidant enzyme activities were measured. Copper accumulation only increased in A. cervicornis zooxanthellae and corresponded with photosynthetic toxicity. Enzyme activities in both coral species were affected; however, A. cervicornis was more sensitive than P. damicornis, and zooxanthellae were more affected than animal fractions of holobionts. Generally, activities of all anti-oxidant enzymes increased, with copper exposure in corals; whereas, activities of glutathione reductase and to some degree glutathione peroxidase were observed due to increasing CO2 exposure alone. Exposure to copper in combination with higher CO2 resulted in a synergistic response in some cases. These results provide insight into mechanisms of copper and CO2 impacts in corals.

Continue reading ‘Physiological responses of corals to ocean acidification and copper exposure’


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