Posts Tagged 'metals'

Physiological and biochemical impacts induced by mercury pollution and seawater acidification in Hediste diversicolor

The present study evaluated the impacts of predicted seawater acidification and Hg pollution, when stressors were acting alone and in combination, on the polychaete Hediste diversicolor. Polychaetes were exposed during 28 days to low pH (7.5), Hg (5 μg/L) and pH 7.5 + Hg, and physiological alterations (respiration rate), biochemical markers related to metabolic potential (glycogen and protein content, electron transport system activity) and oxidative status (activity of antioxidant and biotransformation enzymes, lipid peroxidation) were evaluated. The results obtained clearly showed that polychaetes were sensitive to low pH and Hg contamination, both acting alone or in combination. Organisms used their energy reserves under stressful conditions, which decreased by up to half of the control content, probably to fuel defence mechanisms. Our findings further demonstrated that polychaetes exposed to these stressors presented increased antioxidant defence mechanisms (3 fold compared to control). However, organisms were not able to prevent cellular damage, especially noticed at Hg exposure and pH 7.5. Overall, although all the tested conditions induced oxidative stress in Hediste diversicolor, the combined effect of seawater acidification and Hg contamination did not induce higher impacts in polychaetes than single stressor exposures. These findings may indicate that predicted climate change scenarios may not increase Hediste diversicolor sensitivity towards Hg and may not significantly change the toxicity of this contaminant to this polychaete species.

Continue reading ‘Physiological and biochemical impacts induced by mercury pollution and seawater acidification in Hediste diversicolor’

Alleviation of mercury toxicity to a marine copepod under multigenerational exposure by ocean acidification

Ocean acidification (OA) may potentially modify the responses of aquatic organisms to other environmental stressors including metals. In this study, we investigated the effects of near-future OA (pCO2 1000 μatm) and mercury (Hg) on the development and reproduction of marine copepod Tigriopus japonicus under multigenerational life-cycle exposure. Metal accumulation as well as seven life history traits (survival rate, sex ratio, developmental time from nauplius to copepodite, developmental time from nauplius to adult, number of clutches, number of nauplii/clutch and fecundity) was quantified for each generation. Hg exposure alone evidently suppressed the number of nauplii/clutch, whereas single OA exposure negligibly affected the seven traits of copepods. However, OA exposure significantly alleviated the Hg inhibitory effects on number of nauplii/clutch and fecundity, which could be explained by the reduced Hg accumulation under OA. Such combined exposure also significantly shortened the development time. Thus, in contrast to earlier findings for other toxic metals, this study demonstrated that OA potentially mitigated the Hg toxicity to some important life traits in marine copepods during multigenerational exposure.

Continue reading ‘Alleviation of mercury toxicity to a marine copepod under multigenerational exposure by ocean acidification’

Simulating CO2 leakage from sub-seabed storage to determine metal toxicity on marine bacteria

Highlights

  • Effects of CO2 leakage from CCS activities on marine bacteria were assessed.
  • Zn and Cd toxicity are evaluated under CO2 acidified conditions.
  • Negative responses because of the combination of metals and CO2 were observed.


Abstract

CO2 storage in sub-seabed marine geological formations has been proposed as an adequate strategy to mitigate high CO2 concentration from the atmosphere. The lack of knowledge about the potential risks of this technology on marine bacteria population in presence of metals has lead us to perform laboratory-scale experiments in order to evaluate its consequences. Thus, the effects of Zn and Cd were studied under acid conditions on Roseobacter sp. and Pseudomonas litoralis. Bacterial abundance (cells mL− 1), growth rates (μ, h− 1), relative inhibitory effects of CO2 (RICO2), and production of Extracellular Polysaccharides Substances (EPS) (μg Glucose cells− 1) were evaluated. A decreasing exopolysaccharides (EPS) production was found under low pH. Bacterial abundance as well as growth rates showed negative effects. Data obtained in this work are useful to determine the potential effects associated with enrichment of CO2 and metals on the marine ecosystem.

Continue reading ‘Simulating CO2 leakage from sub-seabed storage to determine metal toxicity on marine bacteria’

Expected CO2-induced ocean acidification modulates copper toxicity in the green tide alga Ulva prolifera

Highlights

  • The inhibition of Cu on growth and photosynthesis was reduced at moderate pCO2.
  • The inhibition of Cu on growth and photosynthesis was magnified at high pCO2.
  • Respiration and Chl a were enhanced by increased Cu at low and moderate pCO2 levels.
  • Shrank and branched thalli were induced by high Cu and pCO2.


Abstract

Cu is considered to be toxic to macroalgae at higher levels. Ocean acidification can also alter the physiological performances of macroalgae. However, little is known regarding the interactive effects of Cu and ocean acidification on macroalgae. In this study, a green tide macroalga, Ulva prolifera, was cultured at the conditions of three levels of Cu (control, 0.5 μM, and 2 μM) and pCO2 (ambient, 1000 μatm, and 1400 μatm) to investigate the responses of U. prolifera to interaction of Cu exposure and ocean acidification. The relative growth rate of thalli decreased with the rise of Cu for all pCO2 conditions except the 1000 μatm pCO2. Compared with the control, 2 μM Cu reduced the net photosynthetic rate for all pCO2 conditions while 0.5 μM Cu only reduced it at 1400 μatm pCO2. The inhibition rate of Cu on the relative growth rate and net photosynthetic rate was reduced at 1000 μatm pCO2 but was magnified at 1400 μatm pCO2. Contrary to growth, the dark respiration rate was enhanced by 0.5 μM Cu at ambient pCO2 and by 2 μM Cu at ambient and 1000 μatm pCO2, although it was reduced by 2 μM Cu at 1400 μatm pCO2 compared to the control. The 0.5 μM Cu did not affect the relative electron transport rate (rETR) for any pCO2 condition but 2 μM Cu decreased it for all pCO2 conditions except 1000 μatm pCO2. The mute effect of 0.5 μM Cu on the net photosynthetic rate and rETR at ambient pCO2 may be due to more Chl a and Chl b being synthesized. In addition, 2 μM Cu and 1400 μatm pCO2 led to branched thalli, which may be a defense mechanism against the stress of high Cu and pCO2. Our data, for the first time, demonstrate that a modest increase of pCO2 can alleviate the toxicity of Cu to U. prolifera whilst a further increase exacerbates it. U. prolifera can respond to the stress of Cu pollution and ocean acidification via physiological and morphological alterations.

Continue reading ‘Expected CO2-induced ocean acidification modulates copper toxicity in the green tide alga Ulva prolifera’

Marine phytoplankton and the changing ocean iron cycle

The availability of the micronutrient iron governs phytoplankton growth across much of the ocean, but the global iron cycle is changing rapidly due to accelerating acidification, stratification, warming and deoxygenation. These mechanisms of global change will cumulatively affect the aqueous chemistry, sources and sinks, recycling, particle dynamics and bioavailability of iron. Biological iron demand will vary as acclimation to environmental change modifies cellular requirements for photosynthesis and nitrogen acquisition and as adaptive evolution or community shifts occur. Warming, acidification and nutrient co-limitation interactions with iron biogeochemistry will all strongly influence phytoplankton dynamics. Predicting the shape of the future iron cycle will require understanding the responses of each component of the unique biogeochemistry of this trace element to many concurrent and interacting environmental changes.

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Indirect effects of climate changes on cadmium bioavailability and biological effects in the Mediterranean mussel Mytilus galloprovincialis

Despite the great interest in the consequences of climate change on the physiological functioning of marine organisms, indirect and interactive effects of rising temperature and pCO2 on bioaccumulation and responsiveness to environmental pollutants are still poorly explored, particularly in terms of cellular mechanisms. According to future projections of temperature and pH/pCO2, this study investigated the main cellular pathways involved in metal detoxification and oxidative homeostasis in Mediterranean mussels, Mytilus galloprovincialis, exposed for 4 weeks to various combinations of two levels of pH/pCO2 (8.2/∼400 μatm and 7.4/∼3000 μatm), temperature (20 and 25 °C), and cadmium addition (0 and 20 μg/L). Bioaccumulation was increased in metal exposed organisms but it was not further modulated by different temperature and pH/pCO2 combinations. However, interactions between temperature, pH and cadmium had significant effects on induction of metallothioneins, responses of the antioxidant system and the onset of oxidative damages, which was tissue dependent. Multiple stressors increased metallothioneins concentrations in the digestive gland revealing different oxidative effects: while temperature and cadmium enhanced glutathione-dependent antioxidant protection and capability to neutralize peroxyl radicals, the metal increased the accumulation of lipid peroxidation products under acidified conditions. Gills did not reveal specific effects for different combinations of factors, but a general stress condition was observed in this tissue after various treatments. Significant variations of immune system were mainly caused by increased temperature and low pH, while co-exposure to acidification and cadmium enhanced metal genotoxicity and the onset of permanent DNA damage in haemocytes. Elaboration of the whole biomarker data in a cellular hazard index, corroborated the synergistic effects of temperature and acidification which increased the toxicological effects of cadmium. The overall results confirmed that climate change could influence ecotoxicological effects of environmental contaminants, highlighting the importance of a better knowledge of cellular mechanisms to understand and predict responsiveness of marine organisms to such multiple stressors.

Continue reading ‘Indirect effects of climate changes on cadmium bioavailability and biological effects in the Mediterranean mussel Mytilus galloprovincialis’

Responses of the sea anemone, Exaiptasia pallida, to ocean acidification conditions and zinc or nickel exposure

Ocean acidification, caused by increasing atmospheric carbon dioxide (CO2), is a growing concern in marine environments. Land-based sources of pollution, such as metals, have also been a noted problem; however, little research has addressed the combined exposure of both pollutants to coral reef organisms. In this study we examined tissue metal accumulation and physiological effects (activity of anti-oxidant enzymes, catalase and glutathione reductase) in the sea anemone, Exaiptasia pallida after exposure to increased CO2, as well as zinc (Zn) or nickel (Ni). After exposure to four concentrations (nominal values = control, 10, 50, 100 μg/L) of Zn or Ni over 7 days, both metals accumulated in the tissues of E. pallida in a concentration-dependent manner. Anemones exposed to elevated CO2 (1000 ppm) accumulated significant tissue burdens of Zn or Ni faster (by 48 h) than those exposed to the same metal concentrations at ambient CO2. No differences were observed in catalase activity due to Zn exposure; however, 50 μg/L Ni caused a significant increase in catalase activity at ambient CO2. No significant effect on catalase activity from CO2 exposure alone was observed. Glutathione reductase activity was affected by increased Zn or Ni exposure and those effects were influenced by increased CO2. Results of this study provide insight into the toxic mechanisms and environmental implications of CO2 and Zn or Ni exposure to the cnidarian E. pallida.

Continue reading ‘Responses of the sea anemone, Exaiptasia pallida, to ocean acidification conditions and zinc or nickel exposure’


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