Posts Tagged 'toxicants'

Ocean acidification dampens physiological stress response to warming and contamination in a commercially-important fish (Argyrosomus regius)

Highlights

• Atmospheric and water conditions/contaminants influence animal physiology status.
• Scarcely studied multi-stressor effects were extricated via full-factorial design.
• Warming stimulated mercury accumulation, but was offset by acidification.
• Co-occurring acidification countered oxidative stress elicited by other stressors.
• Enhanced mitigation pathways or chemical dynamics may underpin stressor antagonism.

Abstract

Increases in carbon dioxide (CO2) and other greenhouse gases emissions are changing ocean temperature and carbonate chemistry (warming and acidification, respectively). Moreover, the simultaneous occurrence of highly toxic and persistent contaminants, such as methylmercury, will play a key role in further shaping the ecophysiology of marine organisms. Despite recent studies reporting mostly additive interactions between contaminant and climate change effects, the consequences of multi-stressor exposure are still largely unknown. Here we disentangled how Argyrosomus regius physiology will be affected by future stressors, by analysing organ-dependent mercury (Hg) accumulation (gills, liver and muscle) within isolated/combined warming (ΔT = 4 °C) and acidification (ΔpCO2 = 1100 μatm) scenarios, as well as direct deleterious effects and phenotypic stress response over multi-stressor contexts. After 30 days of exposure, although no mortalities were observed in any treatments, Hg concentration was enhanced under warming conditions, especially in the liver. On the other hand, elevated CO2 decreased Hg accumulation and consistently elicited a dampening effect on warming and contamination-elicited oxidative stress (catalase, superoxide dismutase and glutathione-S-transferase activities) and heat shock responses. Thus, potentially unpinned on CO2-promoted protein removal and ionic equilibrium between hydrogen and reactive oxygen species, we found that co-occurring acidification decreased heavy metal accumulation and contributed to physiological homeostasis. Although this indicates that fish can be physiologically capable of withstanding future ocean conditions, additional experiments are needed to fully understand the biochemical repercussions of interactive stressors (additive, synergistic or antagonistic).

Continue reading ‘Ocean acidification dampens physiological stress response to warming and contamination in a commercially-important fish (Argyrosomus regius)’

pH effects in the acute toxicity study of the crude oil-WAF (water accommodated fraction) in the whiteleg shrimp, Litopenaeus vannamei

Oil spillage can cause harmful risks to marine ecology in a short time period and may lead to devastating long-term impacts. Meanwhile, the trends of a pH decrease due to ocean acidification deteriorate spillages’ impact. This study evaluated the influence of pH on crude oil water accommodated fraction (WAF) toxicity to the whiteleg shrimp, Litopenaeus vannamei. Post larvae of the shrimps were exposed to the crude oil-WAF with concentrations of 0%, 25%, 50%, 75%, and 100% under pH concentrations of 6.5 and 8.5 for 72 hours to quantify their mortality. The polycyclic aromatic hydrocarbons (PAHs) of the WAF were analyzed using the GC-MS method, while the LC50 was determined using probit analysis. L. vannamei showed impaired swimming ability, loss of balance, comatose, and even death when the shrimp were acutely exposed to the crude oil WAF. The 72-h LC50 were slightly lower in pH 6.5 than that of 8.5 (101.7±9.6 mL L-1 and 114.67±11.7 mL L-1 respectively). There were 14 PAH compounds presented in the crude oil-WAF in which carcinogenic compound, benzo[a]pyrene, represented 25% of the total concentration of PAHs. The interaction among PAHs may lead synergistic effects that could increase the mortality of the shrimps. However, based on the US EPA’s LC50 scale, the crude oil-WAF is still practically non-toxic to the whiteleg shrimp, L. vannamei.

Continue reading ‘pH effects in the acute toxicity study of the crude oil-WAF (water accommodated fraction) in the whiteleg shrimp, Litopenaeus vannamei’

Marine metal pollution and effects on seaweed species

Heavy metals are significant pollutants continuously released into the biosphere, both naturally and anthropogenically. Conceptually, metal speciation, bioavailability, and associated toxicity in marine organisms depend on a wide array of abiotic and biotic factors. Among these, pH variation is one of the most important environmental factors influencing metal speciation and toxicity. Due to this, ocean acidification is expected to modify metal speciation, altering the effects these nondegradable contaminants have on marine organisms, such as seaweeds. One clear effect of heavy metals on seaweeds is the rapid formation of reactive oxygen species (ROS). The production of ROS beyond the physiological tolerance threshold causes an oxidative stress condition that, if not attenuated, can irreversibly damage cellular constituents such as DNA/RNA, proteins, and lipids. To cope with heavy metal excess, several mechanisms exist in tolerant seaweed species, including the activation of an efficient ROS-scavenging system constituted by metal-binding compounds, antioxidant enzymes, and oxygenated polyunsaturated fatty acids, among others. Another adaptive mechanism involves the participation of ATP-binding cassette (ABC) transporter proteins in translocating a wide variety of compounds across cell membranes, including heavy metals. In contrast, an excessive heavy metal presence can inhibit photosynthesis, reduce pigment concentration and growth, induce cation losses, and disrupt gametophyte development in non-tolerant seaweed species. In a scenario of lowered ocean pH and increased heavy metal toxicity, the important roles played by non-tolerant seaweed species in structuring communities could be severely compromised, with unknown consequences for associated organisms. Therefore, in the upcoming decades, marine pollution could majorly shift and rearrange community compositions and the distributional ranges of species.

Continue reading ‘Marine metal pollution and effects on seaweed species’

Climate change–contaminant interactions in marine food webs: toward a conceptual framework

Climate change is reshaping the way in which contaminants move through the global environment, in large part by changing the chemistry of the oceans and affecting the physiology, health, and feeding ecology of marine biota. Climate change-associated impacts on structure and function of marine food webs, with consequent changes in contaminant transport, fate, and effects, are likely to have significant repercussions to those human populations that rely on fisheries resources for food, recreation, or culture. Published studies on climate change–contaminant interactions with a focus on food web bioaccumulation were systematically reviewed to explore how climate change and ocean acidification may impact contaminant levels in marine food webs. We propose here a conceptual framework to illustrate the impacts of climate change on contaminant accumulation in marine food webs, as well as the downstream consequences for ecosystem goods and services. The potential impacts on social and economic security for coastal communities that depend on fisheries for food are discussed. Climate change–contaminant interactions may alter the bioaccumulation of two priority contaminant classes: the fat-soluble persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), as well as the protein-binding methylmercury (MeHg). These interactions include phenomena deemed to be either climate change dominant (i.e., climate change leads to an increase in contaminant exposure) or contaminant dominant (i.e., contamination leads to an increase in climate change susceptibility). We illustrate the pathways of climate change–contaminant interactions using case studies in the Northeastern Pacific Ocean. The important role of ecological and food web modeling to inform decision-making in managing ecological and human health risks of chemical pollutants contamination under climate change is also highlighted. Finally, we identify the need to develop integrated policies that manage the ecological and socioeconomic risk of greenhouse gases and marine pollutants.

Continue reading ‘Climate change–contaminant interactions in marine food webs: toward a conceptual framework’

Effects of elevated CO2 levels on subcellular distribution of trace metals (Cd and Cu) in marine bivalves

Highlights

  • Effects of CO2 on Cu and Cd accumulation were studied in bivalves.
  • Cd strongly accumulated in organelles and enzymes of clams and oysters.
  • Cu accumulated in mitochondria of oysters but not in those of clams.
  • Elevated CO2 increased Cd accumulation in organelles and potentially Cd toxicity.
  • Elevated CO2 enhanced Cd detoxification in clams and suppressed it in in oysters.

Abstract

Hypercapnia (elevated CO2 levels) and pollution with trace metals such as Cu and Cd are common stressors in estuarine habitats that can negatively affect physiology and health of marine organisms. Hypercapnia can modulate toxicity of trace metals including Cu and Cd; however, the physiological and cellular mechanisms of the metal-CO2 interactions are not well understood. We investigated the effects of elevated PCO2 (∼800 and 2000 μatm) and metal exposure (50 μg l−1 of Cu or Cd) on subcellular distribution of metals in two common species of marine bivalves, Eastern oysters Crassostrea virginica and hard shell clams Mercenaria mercenaria. Oysters accumulated higher burdens of Cu and Cd in the gill tissues compared to clams. In both studied species, Cu was predominantly associated with the metabolically active cell compartments (mitochondria, lysosomes, microsomes and cytosolic enzymes), with a modest fraction sequestered by metallothioneins (∼30%) and the insoluble metal-containing granules (MCG) (∼15–20%). Unlike Cu, Cd was largely sequestered by metallothioneins (∼60–70%), with a relatively small fraction associated with the organelles and the cytosolic enzymes. Mitochondria were the main intracellular target for trace metals accumulating higher concentrations of Cd (and in the case of oysters – of Cu) than other organelles or cytosolic enzymes. Cu accumulation in the metabolically active cellular compartments was independent of the CO2 levels, while Cd content of the organelles and cytosolic enzymes increased at elevated PCO2 in both studied species indicating that hypercapnia may enhance cellular toxicity of Cd in bivalves. Hypercapnia suppressed the sequestration capacity of metallothioneins for Cu and Cd in oysters but increased Cu and Cd load in clam metallothioneins. Thus, metal-induced metabolic injury in oysters may be exaggerated by hypercapnia which enhances metal accumulation in the potentially sensitive intracellular fractions and suppresses the metal detoxification capacity. In contrast, clams appear to be more resistant to the combined effects of hypercapnia and metal exposure reflecting more efficient and robust detoxification mechanisms of this species.

Continue reading ‘Effects of elevated CO2 levels on subcellular distribution of trace metals (Cd and Cu) in marine bivalves’

The impacts of seawater acidification on Ruditapes philippinarum sensitivity to carbon nanoparticles

In the present study, the impacts of multi-walled carbon nanotubes (MWCNTs), one of the most important NMs used in broad industrial and biomedical applications, on the clam Ruditapes philippinarum were evaluated under actual and predicted ocean acidification conditions. For this, oxidative stress, metabolic capacity and neurotoxicity related biomarkers were measured after a long-term exposure of clams to different conditions. The results obtained revealed that under low pH conditions the toxicity of MWCNTs was similar to the impacts measured under control pH. In both cases the energy-related responses in contaminated clams were altered with an increase of their metabolism which resulted into the expenditure of their energy reserves (lower glycogen content). Moreover, R. philippinarum showed oxidative stress when exposed to MWCNTs expressed by higher lipid peroxidation, lower ratio between reduced and oxidized glutathione and activation of antioxidant defences and biotransformation mechanisms. Additionally, neurotoxicity was observed by inhibition of Cholinesterases activity in organisms exposed to MWCNTs at both pHs.

Continue reading ‘The impacts of seawater acidification on Ruditapes philippinarum sensitivity to carbon nanoparticles’

Global proteome profiling of a marine copepod and the mitigating effect of ocean acidification on mercury toxicity after multigenerational exposure

Previously, we found that ocean acidification (OA) mitigates mercury (Hg) toxicity to marine copepod Tigriopus japonicus under multigenerational exposure (four generations, F0-F3). To determine the response mechanisms of T. japonicus against long-term exposure to OA and Hg pollution, we investigated the proteome of F3 copepods after multigenerational exposure to four conditions: pCO2 400 μatm + control; pCO2 1000 μatm + control; pCO2 400 μatm + 1.0 µg/L Hg; and pCO2 1000 μatm + 1.0 µg/L Hg. Functional enrichment analysis indicated that OA enhanced the copepod’s energy production mainly by increasing protein assimilation and proteolysis as a compensatory strategy, which explained its physiological resilience to reduced pH. Conversely, Hg treatment decreased many critical processes, including ferric iron binding, antioxidant activity, cellular homeostasis, and glutathione metabolism, and these toxic events could translate into higher-level responses, i.e., restrained reproduction in copepods. Importantly, the mediation of Hg toxicity in T. japonicus by OA could be explained by the enhanced lysosome-autophagy pathway proteomes that are responsible for repairing/removing damaged proteins/enzymes under stress. Overall, this study provided molecular insights into the response of T. japonicus to long-term exposure of OA and Hg, with a particular emphasis on the mitigating impact of CO2-driven acidification on Hg toxicity.

Continue reading ‘Global proteome profiling of a marine copepod and the mitigating effect of ocean acidification on mercury toxicity after multigenerational exposure’


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Ocean acidification in the IPCC AR5 WG II

OUP book