Posts Tagged 'toxicants'

A Polar outlook: potential interactions of micro- and nano-plastic with other anthropogenic stressors

Highlights

  • MP/NP at the poles should be addressed with chemical and climate stressors.
  • MP/NP and anthropogenic stress interactions may vary seasonally and locally.
  • MP/NP research should focus on polar species enduring high anthropogenic stress.

Abstract

Polar marine ecosystems may have higher sensitivity than other ecosystems to plastic pollution due to recurrent physical and biological features; presence of ice and high UV radiation, slow growth rates and weak genetic differentiation of resident biota, accumulation of persistent organic pollutants and heavy metals, and fast rates of warming and global ocean acidification. Here, we discuss potential sources of and exposure to micro- and nano-plastic in polar marine ecosystems and potential mixture effects of micro- and nano-plastic coupled with chemical and climate related stressors. We address the anthropogenic contaminants likely to be ‘high risk’ for interactions in Arctic and Antarctic waters for reasons such as accumulation under sea-ice, a known sink for plastic particulates. Consequently, we address the potential for localised plastic-chemical interactions and possible seasonal fluctuations in interactions associated with freeze-thaw events. The risks for keystone polar species are also considered, incorporating the behavioural and physiological traits of biota and addressing potential ‘hotspot’ areas. Finally, we discuss a possible direction for future research.

Continue reading ‘A Polar outlook: potential interactions of micro- and nano-plastic with other anthropogenic stressors’

Interactive effects of increasing atmospheric CO2 and copper exposure on the growth and photosynthesis in the young sporophytes of Sargassum fusiforme (Phaeophyta)

Highlights

  • Effects of Cu2+ and elevated atmospheric CO2 on young sporophytes of Sargassum fusiforme were investigated.
  • At elevated CO2, growth inhibition and pigment damage caused by Cu2+ remain at the same level.
  • Elevated CO2 alleviates the Cu-induced suppression on photosystem.
  • Elevated CO2 down-regulates the enzymatic antioxidant system against Cu2+.

Abstract

Little attention has been given to the combined effects of elevated atmospheric CO2-induced ocean acidification (OA) and heavy metal pollution on marine macroalgae at the young stage. This study investigated the mutual effects of copper (Cu) and elevated CO2 on the young sporophytes of brown macroalgae Sargassum fusiforme. A matrix of four copper concentrations, 0, 0.025, 0.075 and 0.15 mg‧L-1, and two levels of CO2 (ambient CO2: 400 μatm; elevated CO2: 1,000 μatm) were used. High concentration of copper exposure greatly depressed photosynthesis and growth of the young sporophytes of S. fusiforme by reducing the apparent photosynthetic efficiency (ɑ), maximum net photosynthetic oxygen evolution rate (Pmax), maximum photochemical quantum yield (Fv/Fm) and pigments content (Chl a and Car). While elevated CO2 alone had obscure impact on this alga. However, the inhibition of Cu stress on Fv/Fm was weakened by elevated CO2, which also decreased the light compensation point (Ic). Meanwhile, the Cu2+-induced ascent in the dark respiration rate (Rd) and superoxide dismutase (SOD) activity was mitigated under the growth with elevated CO2, suggesting an alleviated oxidative stress. Overall, we propose that, under CO2 enrichment condition, the young sporophytes of S. fusiforme may increase photosynthesis efficiency and synthesize less enzymatic antioxidants in face of increasing Cu stress.

Continue reading ‘Interactive effects of increasing atmospheric CO2 and copper exposure on the growth and photosynthesis in the young sporophytes of Sargassum fusiforme (Phaeophyta)’

Photoprotection and antioxidative metabolism in Ulva lactuca exposed to coastal oceanic acidification scenarios in the presence of Irgarol

Highlights

  • Photosynthetic yield is affected by low pH in assays with and without Irgarol.
  • Membrane damage and antioxidant activities increased in low pH added to Irgarol.
  • H2O2 content and lipid peroxidation were not affected by low pH isolated.
  • U.lactuca is tolerant to low pH by triggering photoprotector mechanisms.
  • Protective mechanisms could not avoid the simultaneous effects of low pH and Irgarol.

Abstract

Anthropogenic changes such as ocean acidification, eutrophication, and the release of hazardous chemicals affect coastal environments and aquatic organisms. We investigated the effects of seawater pH (7.4 and 8.2) isolated and in combination with Irgarol on Ulva lactuca. Stress indicators such as membrane damage, lipid peroxidation, and hydrogen peroxide content were assessed. In addition, chlorophyll fluorescence and antioxidant enzyme activities were measured. The photosynthetic yield was affected by low pH in assays with and without Irgarol. However, the combination of low pH and Irgarol promoted photoinhibition, besides the induction of non-photochemical quenching (NPQ) and changes in photosynthetic pigment contents. The induction of NPQ was directly influenced by low pH. The membrane damage was increased in low pH with and without Irgarol exposure. Total soluble protein and carbohydrate contents decreased in low pH, and in presence of Irgarol. The H2O2 content and lipid peroxidation were not affected by low pH. In contrast, Irgarol exposure strongly increased lipid peroxidation in both pHs, suggesting a possible synergistic effect. To avoid the harmful effects of high H2O2U. lactuca increased antioxidant enzyme activities in treatments under low pH and in presence of Irgarol. Our results indicate that U. lactuca is tolerant to low pH by inducing NPQ, changing pigment contents, and increasing antioxidant defenses. In contrast, these protective mechanisms could not avoid the harmful effects of the combination with Irgarol.

Continue reading ‘Photoprotection and antioxidative metabolism in Ulva lactuca exposed to coastal oceanic acidification scenarios in the presence of Irgarol’

Environmental pharmaceuticals and climate change: the case study of carbamazepine in M. galloprovincialis under ocean acidification scenario

Highlights

  • Combined effects of carbamazepine and reduced pH were investigated in M. galloprovincialis.
  • Hypercapnia had a limited influence on carbamazepine accumulation.
  • Interactive effects were observed at both transcriptional and cellular level.
  • Immune system, cellular homeostasis and oxidative processes were mostly affected.
  • Weighted elaboration of results revealed higher hazard by multiple stressors.

Abstract
Contaminants of emerging concern and ocean changes are key environmental stressors for marine species with possibly synergistic, but still unexplored, deleterious effects. In the present study the influence of a simulated ocean acidification scenario (pH = 7.6) was investigated on metabolism and sub-lethal effects of carbamazepine, CBZ (1 µg/L), chosen as one of the most widely diffused pharmaceuticals in marine organisms. A multidisciplinary approach was applied on mussels, M. galloprovincialis, integrating measurement of drug bioaccumulation with changes in the whole transcriptome, responsiveness of various biochemical and cellular biomarkers including immunological parameters, lipid and oxidative metabolism, onset of genotoxic effects. Chemical analyses revealed a limited influence of hypercapnia on accumulation and excretion of CBZ, while a complex network of biological responses was observed in gene expression profile and functional changes at cellular level. The modulation of gamma-aminobutyric acid (GABA) pathway suggested similarities with the Mechanism of Action known for vertebrates: immune responses, cellular homeostasis and oxidative system represented the processes targeted by combined stressors. The overall elaboration of results through a quantitative Weight of Evidence model, revealed clearly increased cellular hazard due to interactions of CBZ with acidification compared to single stressors.

Continue reading ‘Environmental pharmaceuticals and climate change: the case study of carbamazepine in M. galloprovincialis under ocean acidification scenario’

DNA damage and oxidative stress responses of mussels Mytilus galloprovincialis to paralytic shellfish toxins under warming and acidification conditions – elucidation on the organ-specificity

Commonly affected by changes in climate and environmental conditions, coastal areas are very dynamic environments where shellfish play an important ecological role. In this study, the oxidative stress and genotoxic responses of mussels (Mytilus galloprovincialis) exposed to paralytic shellfish toxin (PST) – producing dinoflagellates Gymnodinium catenatum were evaluated under i) current conditions (CC: 19 °C; pH 8.0), ii) warming (W: 24 °C; pH 8.0), iii) acidification (A:19 °C; pH 7.6) and iv) combined effect of warming and acidification (WA: 24 °C; pH 7.6). Mussels were fed with G. catenatum for 5 days, and to a non-toxic diet during the following 10 days. A battery of oxidative stress biomarkers and comet assay was performed at the peak of toxin accumulation and at the end of the post-exposure phase. Under CC, gills and hepatopancreas displayed different responses/vulnerabilities and mechanisms to cope with PST. While gills presented a tendency for lipid peroxidation (LPO) and genetic damage (expressed by the Genetic Damage Indicator – GDI), hepatopancreas seems to better cope with the toxins, as no LPO was observed. However, the mechanisms involved in hepatopancreas protection were not enough to maintain DNA integrity. The absence of LPO, and the antioxidant system low responsiveness, suggests DNA damage was not oxidative. When exposed to toxic algae under W, toxin-modulated antioxidant responses were observed in both gills and hepatopancreas. Simultaneous exposure to the stressors highlighted gills susceptibility with a synergistic interaction increasing DNA damage. Exposure to toxic algae under A led to genotoxicity potentiation in both organs. The combined effect of WA did not cause relevant interactions in gills antioxidant responses, but stressors interactions impacted LPO and GDI. Antioxidant responses and LPO pointed out to be modulated by the environmental conditions in hepatopancreas, while GDI results support the dominance of toxin-triggered process. Overall, these results reveal that simultaneous exposure to warming, acidification and PSTs impairs mussel DNA integrity, compromising the genetic information due to the synergetic effects. Finally, this study highlights the increasing ecological risk of harmful algal blooms to Mytilus galloprovinciallis populations.

Continue reading ‘DNA damage and oxidative stress responses of mussels Mytilus galloprovincialis to paralytic shellfish toxins under warming and acidification conditions – elucidation on the organ-specificity’

Efeitos neurotóxicos do crack-cocaína combinado a cenários de acidificação oceânica no mexilhão marinho Perna perna (in Portuguese)

The oceans are undergoing physical and biogeochemical changes in response to the increasing atmospheric CO2 load and increased ocean uptake, such as surface warming, reduced oxygen and a reduction in calcium carbonate and pH saturation levels. Changes in the pH and chemical composition of seawater can modify the speciation of contaminants, interfering with their bioavailability and toxicity. The present study aimed to evaluate the sublethal effect of the illicit drug crack-cocaine at different concentrations (0.5; 5; 50 µg / L) combined with ocean acidification by CO2 at pH values of 8.1; 7.5; 7.0; 6.5 and 6.0. For this purpose, an analysis of the biomarker of neurotoxic effect acetylcholinesterase (AChe) was performed on mussels Perna perna. The inhibition of AChe after exposure to crack at pH 7.5, 7.0 and 6.5 was preliminarily observed, demonstrating a combined effect of crack-cocaine and pH reduction, which can be observed in future scenarios of acidification in coastal zones contaminated by illicit drugs.

Continue reading ‘Efeitos neurotóxicos do crack-cocaína combinado a cenários de acidificação oceânica no mexilhão marinho Perna perna (in Portuguese)’

Eat, breathe, repeat: physiological responses of the mussel Mytilus galloprovincialis to Diclofenac and ocean acidification

Combined effects of the nonsteroidal anti-inflammatory drug diclofenac and lowered seawater pH were assessed on the physiological responses of the mussel Mytilus galloprovincialis. Bivalves were exposed for 1 week to natural pH (8.1) and two reduced pH values (pH −0.4 units and pH −0.7 units), as predicted under a climate change scenario. After the first week, exposure continued for additional 2 weeks, both in the absence and in the presence of environmentally relevant concentrations of diclofenac (0.05 and 0.5 µg/L). Clearance rate, respiration rate, and excretion rate were measured after 7 days of exposure to pH only and after 14 (T1) and 21 (T2) days of exposure to the various pH*diclofenac combinations. At all sampling times, pH significantly affected all the biological parameters considered, whereas diclofenac generally exhibited a significant influence only at T2. Overall, results demonstrated that the physiological performance of M. galloprovincialis was strongly influenced by the experimental conditions tested, in particular by the interaction between the two stressors after 21 days of exposure. Further studies are needed to assess the combined effects of climate changes and emerging contaminants on bivalve physiology during different life stages, especially reproduction.

Continue reading ‘Eat, breathe, repeat: physiological responses of the mussel Mytilus galloprovincialis to Diclofenac and ocean acidification’

Effects of ocean acidification and microplastics on microflora community composition in the digestive tract of the thick shell mussel Mytilus coruscus through 16s RNA gene sequencing

Ocean acidification and microplastic pollution is a global environmental threat, this research evaluated the effects of ocean acidification and microplastics on mussel digestive tract microbial community. The 16S rRNA gene was sequenced to characterize the flora. Species diversity in the samples was assessed by clustering valid tags on 97% similarity. Bacteroidetes, Firmicutes and Proteobacteria were the three most abundant genera in the four groups, with Bacteroidetes showing the highest diversity. However, no differences in flora structure were evident under various treatments. Phylogenetic relationship analysis revealed Bacteroidetes and Firmicutes had the highest OTU diversity. The weighted UniFrac distance, principal coordinate analysis (PCoA), unweighted pair group method with arithmetic mean (UPGMA) cluster tree and analysis of molecular variance (AMOVA) evaluation results for all samples also showed that changes in pH and microplastics concentration did not significantly affect the microbial community structure in the mussel digestive tract. The results presented the no significant effects of ocean acidification and microplastics intake on mussel intestinal diversity.

Continue reading ‘Effects of ocean acidification and microplastics on microflora community composition in the digestive tract of the thick shell mussel Mytilus coruscus through 16s RNA gene sequencing’

Effect of the UV filter, Benzophenone-3, on biomarkers of the yellow clam (Amarilladesma mactroides) under different pH conditions

Highlights

• Effects of Benzophenone-3 and low pH on the yellow clam, Amarilladesma mactroides

• Benzophenone-3 affects antioxidant defenses in gills and digestive glands.

• Water acidification affects Ca2+-ATPase activity.

• Water acidification and Benzophenone-3 together inhibit carbonic anhydrase activity.

• Acidification may enhance the toxicity of Benzophenone-3.

Abstract

This work aimed to investigate effects of the ocean contamination by the sunscreen Benzophenone-3 (BP3) and acidification, caused by CO2 enrichment, to the yellow clam, Amarilladesma mactroides. Biochemical biomarkers were analyzed in tissues (gills, digestive gland, and mantle) of clams exposed to the environmental concentration of 1 μg/L BP3, at seawater natural pH (pH 8.1) and at lower pH (pH 7.6). The tissues responded in different ways considering their physiological roles. In general, BP3 altered activity of the enzymes, glutathione-S-transferase (GST) and glutathione cysteine ligase (GCL); but mostly increased the level of glutathione (GSH). These effects were enhanced by acidification, without augmenting lipid peroxidation (LPO). Carbonic anhydrase activity (CA) increased after BP3 exposure in the digestive gland and decreased in the gills at pH 7.6, while Ca2+-ATPase activity was affected by acidification only. Changing levels of these enzymes can alter shell formation and affect the bivalve maintenance in impacted environments.

Continue reading ‘Effect of the UV filter, Benzophenone-3, on biomarkers of the yellow clam (Amarilladesma mactroides) under different pH conditions’

Diatom aggregation when exposed to crude oil and chemical dispersant: potential impacts of ocean acidification

Diatoms play a key role in the marine carbon cycle with their high primary productivity and release of exudates such as extracellular polymeric substances (EPS) and transparent exopolymeric particles (TEP). These exudates contribute to aggregates (marine snow) that rapidly transport organic material to the seafloor, potentially capturing contaminants like petroleum components. Ocean acidification (OA) impacts marine organisms, especially those that utilize inorganic carbon for photosynthesis and EPS production. Here we investigated the response of the diatom Thalassiosira pseudonana grown to present day and future ocean conditions in the presence of a water accommodated fraction (WAF and OAWAF) of oil and a diluted chemically enhanced WAF (DCEWAF and OADCEWAF). T. pseudonana responded to WAF/DCEWAF but not OA and no multiplicative effect of the two factors (i.e., OA and oil/dispersant) was observed. T. pseudonana released more colloidal EPS ( 3 kDa) in the presence of WAF/DCEWAF/OAWAF/OADCEWAF than in the corresponding Controls. Colloidal EPS and particulate EPS in the oil/dispersant treatments have higher protein-to-carbohydrate ratios than those in the control treatments, and thus are likely stickier and have a greater potential to form aggregates of marine oil snow. More TEP was produced in response to WAF than in Controls; OA did not influence its production. Polyaromatic hydrocarbon (PAH) concentrations and distributions were significantly impacted by the presence of dispersants but not OA. PAHs especially Phenanthrenes, Anthracenes, Chrysenes, Fluorenes, Fluoranthenes, Pyrenes, Dibenzothiophenes and 1-Methylphenanthrene show major variations in the aggregate and surrounding seawater fraction of oil and oil plus dispersant treatments. Studies like this add to the current knowledge of the combined effects of aggregation, marine snow formation, and the potential impacts of oil spills under ocean acidification scenarios.

Continue reading ‘Diatom aggregation when exposed to crude oil and chemical dispersant: potential impacts of ocean acidification’


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