Posts Tagged 'metals'

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’

Ocean acidification modulates the incorporation of radio-labeled heavy metals in the larvae of the Mediterranean sea urchin Paracentrotus lividus

Highlights

• The radionuclide method allowed accurate tracing of the metal incorporation within this microscopic planktonic species.
• Metal incorporation in sea urchin larvae strongly correlates with the indirect delaying effect of acidification on larval size.
• Independently of the size effect, acidification directly affects the incorporation behavior of four metals (Mn, Ag, Se, Zn).
• The nature of the modulation is specific to each metallic element (see graphical abstract).
• Relationships between speciation, bioaccumulation and toxicity in the context of changing seawater pH requires more research.

Abstract

The marine organisms which inhabit the coastline are exposed to a number of anthropogenic pressures that may interact. For instance, the accumulation of toxic metals present in coastal waters is expected to be modified by ocean acidification through e.g. changes in physiological performance and/or elements availability. Changes in bioaccumulation due to lowering pH are likely to be differently affected depending on the nature (essential vs. non-essential) and speciation of each element. The Mediterranean is of high concern for possible cumulative effects due to strong human influences on the coastline.

The aim of this study was to determine the effect of ocean acidification (from pH 8.1 down to −1.0 pH units) on the incorporation kinetics of six trace metals (Mn, Co, Zn, Se, Ag, Cd, Cs) and one radionuclide (241Am) in the larvae of an economically- and ecologically-relevant sea urchin of the Mediterranean coastline: Paracentrotus lividus. The radiolabelled metals and radionuclides added in trace concentrations allowed precise tracing of their incorporation in larvae during the first 74 h of their development.

Independently of the expected indirect effect of pH on larval size/developmental rates, Paracentrotus lividus larvae exposed to decreasing pHs incorporated significantly more Mn and Ag and slightly less Cd. The incorporation of Co, Cs and 241Am was unchanged, and Zn and Se exhibited complex incorporation behaviors. Studies such as this are necessary prerequisites to the implementation of metal toxicity mitigation policies for the future ocean. We discuss possible reasons and mechanisms for the specific effect of pH on each metals.

Continue reading ‘Ocean acidification modulates the incorporation of radio-labeled heavy metals in the larvae of the Mediterranean sea urchin Paracentrotus lividus’

Metal fractionation in marine sediments acidified by enrichment of CO2: a risk assessment

Highlights

• Acidification related to CO2 leakages modifies the geochemistry of metals.
• Mobilization of metals from sediment into the water column is associated with their speciation.
• Sediments from Huelva Estuary have relevant concentrations of As, Cu, Pb and Zn.
• Risk assessment code analysis revealed that Zn presents the highest potential risk.

Abstract

Carbon-capture and storage is considered to be a potential mitigation option for climate change. However, accidental leaks of CO2 can occur, resulting in changes in ocean chemistry such as acidification and metal mobilization. Laboratory experiments were performed to provide data on the effects of CO2-related acidification on the chemical fractionation of metal(loid)s in marine-contaminated sediments using sequential extraction procedures. The results showed that sediments from Huelva estuary registered concentrations of arsenic, copper, lead, and zinc that surpass the probable biological effect level established by international protocols. Zinc had the greatest proportion in the most mobile fraction of the sediment. Metals in this fraction represent an environmental risk because they are weakly bound to sediment, and therefore more likely to migrate to the water column. Indeed, the concentration of this metal was lower in the most acidified scenarios when compared to control pH, indicating probable zinc mobilization from the sediment to the seawater.

Continue reading ‘Metal fractionation in marine sediments acidified by enrichment of CO2: a risk assessment’

Global change effects on seagrass ecosystem

Rising carbon dioxide (CO2) concentrations in the atmosphere will increase the average pCO2 level in the world oceans, which will have a knock-on effect on the marine ecosystem. Coastal seagrass communities one of the most productive marine ecosystems are predicted to benefit from the increase in CO2 levels, but long-term effects of elevated CO2 on seagrass communities are less understood. Population reconstruction techniques was used to investigate the population dynamics of Cymodocea nodosa meadows, exposed to long term elevated CO2 at volcanic seeps off Greece and Italy. Effect of elevated CO2 was noticed on the growth, morphometry, density, biomass and age structure at CO2 seeps. Above to below ground biomass ratio of C. nodosa were higher at CO2 seeps than at reference sites. The plastochrome interval were similar at all CO2 seeps. The shoot age and shoot longevity of plants were lower at seeps than reference sites. The present recruitment (sampled year) of the seagrass were higher than long-term average recruitment of the communities near the seeps. Carbon to nitrogen ratios (%DW) of C. nodosa were higher in leaves at seeps. Annual leaf production was higher near the seeps. This study suggests increased production of C. nodosa under elevated CO2 levels, but other co-factors such as nutrients, trace metal toxicity must also be taken into consideration while predicting effects of future CO2 concentrations. Volcanic CO2 seeps are now being used as natural analogues for ocean acidification studies although these areas can be affected by trace element input and may alter ecosystem responses to gradient in carbonate chemistry. Here Fe and a range of trace elements (Cd, Co, Cu, Hg, Mn, Pb, Ni and Zn) were analysed from sediments and from the roots, rhizomes and leaves of seagrass at six CO2 seeps and reference sites off Greece and Italy. There were higher metal levels in sediment and seagrasses at all CO2 seeps than reference sites. Sediment Quality Guideline Quotient, a commonly used pollution index, indicated that some of the metals (Cd, Cu, Hg, Ni) were in high enough concentrations to have adverse biological effects, such as Cu at Ischia site and Hg at Vulcano. Higher accumulation of elements from sediments in roots and leaves at CO2 seeps were found from Bio Sediment Accumulation Factor index. There were higher levels of Cu, Fe, Mn and Zn in leaves and rhizomes for P. oceanica and higher levels of Cd, Co, Cu, Fe and Zn in C. nodosa compartments at CO2 seeps. Fe and Mn were found with positive correlation within sediment-roots and sediment-rhizomes, whereas Cd, Co and Pb were found with positive correlation in compartments of C. nodosa. In P. oceanica positive correlation were only observed for Cd within sediment-roots and plant compartments. Low pH and ocean acidification increased the concentration of elements at CO2 seeps than reference sites. Thus, caution is needed, when using volcanic seep systems as analogue for the effects of rising CO2, as metals can reach levels that are toxic to seagrass, masking any potential benefits of increased levels of carbon dioxide for seagrass productivity. Net community production (NCP) and community respiration (CR) were measured under air exposed and CO2 enriched conditions for intertidal Z. noltei meadows and unvegetated sediment communities during emersion in summer and winter seasons. Community production and respiration were measured in-situ using benthic chambers. CO2 flux under air and CO2 enriched conditions were measured over a series of short term incubations (30min) using an infra-red gas analyser. Incident photosynthetic active radiation (PAR) was recorded during the incubations covering the daily and seasonal variation. Linear regression model was used to test the effects of irradiance on net community production. NCP of Z. noltei community were higher under CO2 enriched conditions than air exposed conditions in both summer and winter seasons. There was no effect of CO2 on the CR rate of Z. noltei community in summer season. NCP of sediment community were higher in summer season and winter season under CO2 enriched conditions. Sediment CR rates were higher in winter than summer season. The light compensation point of Z. noltei and sediment community were lower in both seasons under CO2 enriched conditions. Seasonal budget of community production was higher in Z. noltei than sediment communities. A clear effect of PAR was noticed on the net community production of both communities. Higher PAR intensities resulted in higher NCP under CO2 enriched conditions for both communities. CO2 enrichment will have a positive effect on the intertidal communities during emersion.

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Interactive effects of ocean acidification with other environmental drivers on marine plankton

Planktonic organisms form the base of the marine food web and may be impacted by environmental change in many ways. The interactive effects of multiple, simultaneous climate-driven changes on these organisms are not well understood. This dissertation examined the impacts of ocean acidification in combination with other environmental stressors on marine plankton and determined spatial patterns of one of these potential interactive drivers. Chapter 2 investigated the synergistic effects of ocean acidification and hypoxia on the harmful dinoflagellate Amphidinium carterae. Findings indicated that empirical studies may be crucial to accurately predict organismal responses to multi-stressors. Results also suggested that photorespiration may serve a previously unrecognized role in dinoflagellate metabolism. Chapter 3 examined the combined effects of ocean acidification and lithogenic trace metals on the growth of another harmful dinoflagellate, Cochlodinium polykrikoides. Results indicated that high suspended sediment loads may deliver toxic concentrations of trace elements to marine phytoplankton in acidified coastal ecosystems. Chapter 4 examined the interactive effects of ocean acidification and bacteria on the severity and extent of dissolution in the shells of larval gastropods and the adult pteropod Limacina helicina. Research findings indicated that microbial communities on the shell surfaces of some planktonic molluscs may mediate certain types of shell dissolution in acidified, upwelled waters. Chapter 5 explored the use of thorium isotope fluxes as a proxy for dust and lithogenic iron in the Indian Ocean. Results suggested that the gradient of dust fluxes in the region could impose thresholds for biological productivity. Together, these interdisciplinary studies demonstrate coupled biological and chemical changes in marine ecosystems as a result of increased anthropogenic environmental change.

Continue reading ‘Interactive effects of ocean acidification with other environmental drivers on marine plankton’


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Ocean acidification in the IPCC AR5 WG II

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