Posts Tagged 'metals'

Oxidative and interactive challenge of cadmium and ocean acidification on the smooth scallop Flexopecten glaber


• Combined effects of acidification and cadmium were analysed in the scallop, F. glaber.
• Reduced pH slightly increased bioaccumulation of Cd.
• Synergistic and antagonistic effects occurred at cellular level.
• Tissue-specific responses indicate higher sensitivity of gills than digestive gland.
• Ocean acidification modulates the cellular toxicity of metals.


Ocean acidification (OA) may affect sensitivity of marine organisms to metal pollution modulating chemical bioavailability, bioaccumulation and biological responsiveness of several cellular pathways. In this study, the smooth scallop Flexopecten glaber was exposed to various combinations of reduced pH (pH/pCO2 7.4/∼3000 μatm) and Cd (20 μg/L). The analyses on cadmium uptake were integrated with those of a wide battery of biomarkers including metallothioneins, single antioxidant defenses and total oxyradical scavenging capacity in digestive gland and gills, lysosomal membrane stability and onset of genotoxic damage in haemocytes. Reduced pH slightly increased concentration of Cd in scallop tissues, but no effects were measured in terms of metallothioneins. Induction of some antioxidants by Cd and/or low pH in the digestive gland was not reflected in variations of the total oxyradical scavenging capacity, while the investigated stressors caused a certain inhibition of antioxidants and reduction of the scavenging capacity toward peroxyl radical in the gills. Lysosomal membrane stability and onset of genotoxic damages showed high sensitivity with possible synergistic effects of the investigated factors. The overall results suggest that indirect effects of ocean acidification on metal accumulation and toxicity are tissue-specific and modulate oxidative balance through different mechanisms.

Continue reading ‘Oxidative and interactive challenge of cadmium and ocean acidification on the smooth scallop Flexopecten glaber’

Increased CO2 and iron availability effects on carbon assimilation and calcification on the formation of Emiliania huxleyi blooms in a coastal phytoplankton community


• Increased dFe enhanced carbon fixation promoting a bloom of Emiliania huxleyi.
• High CO2 decreased carbon production during a bloom of Emiliania huxleyi.
• Carbon uptake was unaffected by CO2 and Fe availability in a bloom of Emiliania huxleyi.


In the present work, we exposed a natural phytoplankton community to either present (390-μatm, LC) or future CO2 levels predicted for year-2100 (900-μatm, HC) combined with ambient (4.5 nmol L−1, −DFB) or high (12 nmol L−1, +DFB) dissolved iron (dFe) levels, during 25 days by using mesocosms. We report on changes in carbon assimilation processes (acquisition, fixation, and calcification) of the phytoplankton community due to increased dissolved CO2 and dFe and to the interaction of both factors. The isotopic disequilibrium assay results showed that inorganic carbon (Ci) acquisition by the community was unaffected by CO2 and Fe availability. The main Ci source for photosynthesis was HCO3 and external carbonic anhydrase activity was only detected at the beginning of the experiment, suggesting a relevant role for HCO3 transporters in the phytoplankton community developed in all treatments. However, there was a significant effect of both factors on particulate organic carbon (POC) content, particulate calcium production and carbon fixation rates. Increased dFe at LC conditions led to the highest values of carbon fixation and POC of all treatments, promoting a massive Emiliania huxleyi bloom. This response was not observed in the HC treatments. The latter indicates a negative impact of increased CO2 on the formation of E. huxleyi blooms, in agreement with the observed significant reduction in calcium production under HC. Our results suggest that ocean acidification can decrease primary production under iron-replete conditions in E. huxleyi blooming areas, affecting the biological carbon pump in coastal ecosystems.

Continue reading ‘Increased CO2 and iron availability effects on carbon assimilation and calcification on the formation of Emiliania huxleyi blooms in a coastal phytoplankton community’

Elevated toxic effect of sediments on growth of the harmful dinoflagellate Cochlodinium polykrikoides under high CO2

Ocean acidification will likely have significant impacts on phytoplankton growth in marine ecosystems over the course of this century. Coastal waters, which can be strongly influenced by suspended sediments, can also be particularly sensitive to ocean acidification. While the individual effects of trace metal inputs and ocean acidification have each been well documented, the combined effects of high trace metal concentrations due to mobilization from sediments and high dissolved CO2 concentrations (low seawater pH) on the growth of marine phytoplankton are not known. In this study, a batch culture experiment was performed using the model organism Cochlodinium polykrikoides over 35 d under a range of CO2 concentrations (400, 800, and 1200 ppmv) following sediment additions. At high CO2, dissolved iron (Fe) and nickel (Ni) concentrations increased over time. Dissolved Ni concentrations were significantly higher after 35 d at 1200 ppmv CO2 compared to the other treatments and corresponded to significant decreases in C. polykrikoides growth rates. In addition, a toxicity bioassay experiment was performed over 29 d under a range of Ni or cadmium (Cd) concentrations at ambient CO2. The growth responses of C. polykrikoides were dose-dependent and were significantly lower under increasing Ni or Cd concentrations. The findings suggest that a combination of elevated total dissolved Ni supplied from sediments and high CO2 conditions could suppress the growth rates and photosynthesis of C. polykrikoides in coastal marine ecosystems. This is the first study to examine the synergistic, toxic effects of lithogenic trace metals and CO2 on phytoplankton growth.

Continue reading ‘Elevated toxic effect of sediments on growth of the harmful dinoflagellate Cochlodinium polykrikoides under high CO2’

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


  • 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.


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’

Iron sources alter the response of Southern Ocean phytoplankton to ocean acidification

The rise in anthropogenic CO2 and the associated ocean acidification (OA) will change trace metal solubility and speciation, potentially altering Southern Ocean (SO) phytoplankton productivity and species composition. As iron (Fe) sources are important determinants of Fe bioavailability, we assessed the effect of Fe-laden dust versus inorganic Fe (FeCl3) enrichment under ambient and high pCO2 levels (390 and 900 μatm) in a naturally Fe-limited SO phytoplankton community. Despite similar Fe chemical speciation and net particulate organic carbon (POC) production rates, CO2-dependent species shifts were controlled by Fe sources. Final phytoplankton communities of both control and dust treatments were dominated by the same species, with an OA-dependent shift from the diatom Pseudo nitzschia prolongatoides towards the prymnesiophyte Phaeocystis antarctica. Addition of FeCl3 resulted in high abundances of Nitzschia lecointei and Chaetoceros neogracilis under ambient and high pCO2, respectively. These findings reveal that both the characterization of the phytoplankton community at the species level and the use of natural Fe sources are essential for a realistic projection of the biological carbon pump in the Fe-limited pelagic SO under OA. As dust deposition represents a more realistic scenario for the Fe-limited pelagic SO under OA, unaffected net POC production and dominance of P. antarctica can potentially weaken the export of carbon and silica in the future.

Continue reading ‘Iron sources alter the response of Southern Ocean phytoplankton to ocean acidification’

Assessment of the environmental impacts of ocean acidification (OA) and carbon capture and storage (CCS) leaks using the amphipod Hyale youngi

This study aims to ascertain the effects of CO2 induced water acidification and leaks from Carbon Capture and Storage activities on the South American amphipod Hyale youngi. A 10-day acute toxicity test was performed using sediments from two sites located inside the Santos Estuarine System. They were subjected to five pH treatments (8.1, 7.6, 7.0, 6.5, and 6.0). Metals (Cd, Cu, Cr, Pb, Ni and Zn) and the metalloid As were analyzed to determine the influence of their acidification-related mobility on the amphipods mortality. The results showed that mortality becomes significant when compared to control in pH 6.5 in the Canal de Piaçaguerasediment (contaminated) and at pH 6.0 in Ilha das Palmas sediment (reference).

Continue reading ‘Assessment of the environmental impacts of ocean acidification (OA) and carbon capture and storage (CCS) leaks using the amphipod Hyale youngi’

CO2 induced growth response in a diatom dominated phytoplankton community from SW Bay of Bengal coastal water

The ongoing increase in surface seawater CO2 level could potentially impact phytoplankton primary production in coastal waters; however, CO2 sensitivity studies on tropical coastal phytoplankton assemblages are rare. The present study investigated the interactive impacts of variable CO2 level, light and zinc addition on the diatom dominated phytoplankton assemblages from the western coastal Bay of Bengal. Increased CO2supply enhanced particulate organic matter (POC) production; a concomitant depletion in δ13CPOM values at elevated CO2 suggested increased CO2 diffusive influx inside the cell. Trace amount of Zn added under low CO2 level accelerated growth probably by accelerating Zn-Carbonic Anhydrase activity which helps in converting bicarbonate ion to CO2. Almost identical values of δ13CPOM in the low CO2 treated cells grown with and without Zn indicated a low discrimination between 13C and 12C probably due to bicarbonate uptake. These evidences collectively indicated the existence of the carbon concentration mechanisms (CCMs) at low CO2. A minimum growth rate was observed at low CO2 and light limited condition indicating light dependence of CCMs activity. Upon the increase of light and CO2 level, growth response was maximum. The cells grown in the low CO2 levels showed higher light stress (higher values of both diatoxanthin index and the ratio of photo-protective to light-harvesting pigments) that was alleviated by both increasing CO2 supply and Zn addition (probably by efficient light energy utilization in presence of adequate CO2). This is likely that the diatom dominated phytoplankton communities benefited from the increasing CO2 supply and thus may enhance primary production in response to any further increase in coastal water CO2 levels and can have large biogeochemical consequences in the study area.

Continue reading ‘CO2 induced growth response in a diatom dominated phytoplankton community from SW Bay of Bengal coastal water’

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Ocean acidification in the IPCC AR5 WG II

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