Posts Tagged 'metals'

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’

Effects of copper on hemocyte parameters in the estuarine oyster Crassostrea rivularis under low pH conditions

Highlights

• Hemocyte parameters of oysters were determined by FC in vitro and in vivo.
• Synergistic effects of Cu and low pH on oyster hemocyte were observed.
• Cu exerted a stronger influence on hemocyte parameters than low pH.
• Carry-over impacts of Cu and low pH were found during the recovery period.

Abstract

With the development of industry and agriculture, the metal pollutants (e.g., Cu) are inevitably released into the aquatic environment. In addition, ocean acidification (OA) as a major environmental stress is affecting marine organisms. In this study, we investigated the hemocyte responses of the estuarine oyster Crassostrea rivularis exposed to six combinations of two pH levels (8.1 and 7.7) and three Cu concentrations (0, 10 and 50 μg/l) using flow cytometry in vitro and in vivo. In both experiments, Cu and low pH jointly affected the hemocyte parameters of oyster. High Cu exposure resulted in decreased total hemocyte count (THC), esterase activity (EA) and lysosomal content (LC) and increased hemocyte mortality (HM), phagocytosis activity (PA) and reactive oxygen species (ROS) production, especially under low pH conditions. The immune suppression of metal-exposure was more significant than low pH exposure with a 28-d experimental period in oysters. A slight recovery of the immune parameters was observed in THC, HM, PA, ROS and LC. During the depuration period, the modulatory effects of pH were still obvious. In addition, carry-over effects of high Cu and low pH were still observed. Overall, our results showed that copper and low pH weaken immune functions of hemocyte in oysters, with synergistic effects. This work provides new evidence of sublethal negative effects of metals on marine animals under global change scenarios, and copper likely leads to reduced fitness of oysters under low pH conditions.

 

Continue reading ‘Effects of copper on hemocyte parameters in the estuarine oyster Crassostrea rivularis under low pH conditions’

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’

Seawater acidification aggravated cadmium toxicity in the oyster Crassostrea gigas: Metal bioaccumulation, subcellular distribution and multiple physiological responses

Highlights
• Ocean acidification aggravated the toxicity of environmental relevant concentration of Cd on C. gigas.
• OA exacerbated the oxidative stresses, histopathological damage, and apoptosis of Cd-exposed oysters.
• Apoptosis-pathway was generally stimulated in Cd-OA exposed oysters.
• Increased toxicity perhaps associated with the increased accumulation and altered subcellular distribution of Cd.

Abstract
Mounting evidence has demonstrated the combined effects of ocean acidification (OA) and other environmental stressors on marine organisms. Although metal pollution is widely distributed in coasts and estuaries, the combined effects of OA and metal pollution have received little attention until recent years. In this study, the accumulation and subcellular distribution of cadmium (Cd) and the physiological responses of the oyster Crassostrea gigas were investigated after 31 days of exposure to OA and Cd, either alone or in combination. Increased Cd accumulation was found both in gills (about 57% increase at pH 7.8, 22% increase at pH 7.6) and digestive glands (about 38% increase at pH 7.8, 22% increase at pH 7.6) of C. gigas under elevated pCO2 exposure. Although a similar total Cd accumulation pattern was seen in oyster gills and digestive glands, a higher partition of Cd in the BIM (biologically inactive metal) fractions of gills (about 60%) was found in Cd-exposed treatments compared to the digestive glands (about 45%), which might correspond to the generally lower toxicity in gills. Moreover, synergetic effects of Cd and OA on the oxidative stresses, histopathological damage, and apoptosis of exposed oysters were observed in this study, which might be explained by significant interactions of these two factors on increased generation of ROS. These findings demonstrated that OA could aggravate the toxicity of metals in marine organisms, with significant implications for coastal benthic ecosystems regarding the widespread metal contamination and the concurrent increase of acidified seawater.

Continue reading ‘Seawater acidification aggravated cadmium toxicity in the oyster Crassostrea gigas: Metal bioaccumulation, subcellular distribution and multiple physiological responses’

Effects of CO2 enrichment on metal bioavailability and bioaccumulation using Mytilus galloprovincialis

Highlights

• This study addresses the effects of acidification in marine ecosystems using mussels.
• CO2 enrichment in the marine ecosystem increased significantly the concentrations of some metals
• There was relationship between accumulation of metals in tissues of Mytilus galloprovincialis and the decrease of pH values
• The increase in the bioaccumulation of Fe, Ni and Zn in the body of mussels is related to acidification

Abstract

The main aim of this study was to evaluate the bioavailability of metals related to CO2 enrichment on the mussels Mytilus galloprovincialis by metal’s bioaccumulation analysis. Two sediment samples were selected and subjected to different pH levels. Concentrations of metals were measured in the overlying seawater and in the whole body of mussels exposed on the 7th, 14th and 21st days. Results showed that the CO2 enrichment in aquatic ecosystems cause significant (p < 0.05) changes on the concentrations of Cu, Zn, Ni, Mn and As between the control pH and pH 7.0 after 7 days of exposure; and in the concentration of Fe at pH 6.0 using the RSP sediment. The multivariate analysis results showed that the increase in the bioaccumulation of some metals in mussels was linked to the acidification. It was concluded that many factors may interfere in the results when the acidification and bioavailability of metals are inquired.

Continue reading ‘Effects of CO2 enrichment on metal bioavailability and bioaccumulation using Mytilus galloprovincialis’


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