Aluminium (Al) is a common chemical element released into the aquatic environment from the Earth’s crust and many anthropogenic activities. It may be present in various dissolved and precipitated forms [Al3+, AlOH2+, Al(OH)2+, Al(OH)03, Al(OH)4−, etc.], which are potentially toxic for organisms. This review summarizes information about the concentrations of Al detected in aquatic ecosystems and its effects on both freshwater and marine organisms (such as growth disturbance, reproduction, and respiration alterations). As the chemistry of Al is different in freshwater and marine systems, we discuss the behaviour of aluminium and its effects on marine or freshwater fauna. Therefore, the solubility of Al, as other metals, is highly pH dependent, which increases when pH decreases. We are assuming that ocean acidification, linked to climate change, would affect the Al bioavailability in the aquatic environment, which may increase its ecotoxicological effects on semi-closed (Bays, Mediterranean Sea, etc.) or closed (lakes, etc.) aquatic ecosystems.
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Aluminium in aquatic environments: abundance and ecotoxicological impacts
Published 28 February 2022 Science ClosedTags: metals, review, toxicants
Ocean acidification effect on the iron-gallic acid redox interaction in seawater
Published 28 February 2022 Science ClosedTags: chemistry, metals, methods, multiple factors
Ocean acidification impacts the iron (Fe) biogeochemistry both by its redox and its complexation reactions. This has a direct effect on the ecosystems due to Fe being an essential micronutrient. Polyphenols exudated by marine microorganisms can complex Fe(III), modifying the Fe(II) oxidation rates as well as promoting the reduction of Fe(III) to Fe(II) in seawater. The effect of the polyphenol gallic acid (GA; 3,4,5-trihydroxy benzoic acid) on the oxidation and reduction of Fe was studied. The Fe(II) oxidation rate constant decreased, increasing the permanence of Fe(II) in solutions at nM levels. At pH = 8.0 and in the absence of gallic acid, 69.3% of the initial Fe(II) was oxidized after 10 min. With 100 nM of gallic acid (ratio 4:1 GA:Fe), and after 30 min, 37.5% of the initial Fe(II) was oxidized. Fe(III) is reduced to Fe(II) by gallic acid in a process that depends on the pH and composition of solution, being faster as pH decreases. At pH > 7.00, the Fe(III) reduction rate constant in seawater was lower than in NaCl solutions, being the difference at pH 8.0 of 1.577 × 10–5 s–1. Moreover, the change of the Fe(III) rate constant with pH, within the studied range, was higher in seawater (slope = 0.91) than in NaCl solutions (slope = 0.46). The Fe(III) reduction rate constant increased with increasing ligand concentration, being the effect higher at pH 7.0 [k′ = 1.078 × 10–4 s–1; (GA) = 250 nM] compared with that at pH 8.0 [k′ = 3.407 × 10–5 s–1; (GA) = 250 nM]. Accordingly, gallic acid reduces Fe(III) to Fe(II) in seawater, making possible the presence of Fe(II) for longer periods and favoring its bioavailability.
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Responses of a natural phytoplankton community from the Drake Passage to two predicted climate change scenarios
Published 25 February 2022 Science ClosedTags: Antarctic, biogeochemistry, biological response, BRcommunity, laboratory, light, metals, multiple factors, photosynthesis, phytoplankton, South Pacific
Contrasting models predict two different climate change scenarios for the Southern Ocean (SO), forecasting either less or stronger vertical mixing of the water column. To investigate the responses of SO phytoplankton to these future conditions, we sampled a natural diatom dominated (63%) community from today’s relatively moderately mixed Drake Passage waters with both low availabilities of iron (Fe) and light. The phytoplankton community was then incubated at these ambient open ocean conditions (low Fe and low light, moderate mixing treatment), representing a control treatment. In addition, the phytoplankton was grown under two future mixing scenarios based on current climate model predictions. Mixing was simulated by changes in light and Fe availabilities. The two future scenarios consisted of a low mixing scenario (low Fe and higher light) and a strong mixing scenario (high Fe and low light). In addition, communities of each mixing scenario were exposed to ambient and low pH, the latter simulating ocean acidification (OA). The effects of the scenarios on particulate organic carbon (POC) production, trace metal to carbon ratios, photophysiology and the relative numerical contribution of diatoms and nanoflagellates were assessed. During the first growth phase, at ambient pH both future mixing scenarios promoted the numerical abundance of diatoms (∼75%) relative to nanoflagellates. This positive effect, however, vanished in response to OA in the communities of both future mixing scenarios (∼65%), with different effects for their productivity. At the end of the experiment, diatoms remained numerically the most abundant phytoplankton group across all treatments (∼80%). In addition, POC production was increased in the two future mixing scenarios under OA. Overall, this study suggests a continued numerical dominance of diatoms as well as higher carbon fixation in response to both future mixing scenarios under OA, irrespective of different changes in light and Fe availability.
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Lead in the marine environment: concentrations and effects on invertebrates
Published 27 January 2022 Science ClosedTags: annelids, BRcommunity, cnidaria, crustaceans, echinoderms, metals, mollusks, mortality, multiple factors, physiology, reproduction, review
Lead (Pb) is a non-essential metal naturally present in the environment and often complexed with other elements (e.g., copper, selenium, zinc). This metal has been used since ancient Egypt and its extraction has grown in the last centuries. It has been used until recently as a fuel additive and is currently used in the production of vehicle batteries, paint, and plumbing. Marine ecosystems are sinks of terrestrial contaminations; consequently, lead is detected in oceans and seas. Furthermore, lead is not biodegradable. It remains in soil, atmosphere, and water inducing multiple negative impacts on marine invertebrates (key species in trophic chain) disturbing ecological ecosystems. This review established our knowledge on lead accumulation and its effects on marine invertebrates (Annelida, Cnidaria, Crustacea, Echinodermata, and Mollusca). Lead may affect different stages of development from fertilization to larval development and can also lead to disturbance in reproduction and mortality. Furthermore, we discussed changes in the seawater chemistry due to Ocean Acidification, which can affect the solubility, speciation, and distribution of the lead, increasing potentially its toxicity to marine invertebrates.
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The combined effects of ocean acidification and heavy metals on marine organisms: a meta-analysis
Published 20 January 2022 Science ClosedTags: algae, biological response, corals, fish, metals, mollusks, review
Ocean acidification (OA) may interact with anthropogenic pollutants, such as heavy metals (HM), to represent a threat to marine organisms and ecosystems. Here, we perform a quantitative meta-analysis to examine the combined effects of OA and heavy metals on marine organisms. The results reveal predominantly additive interactions (67%), with a considerable proportion of synergistic interactions (25%) and a few antagonistic interactions (8%). The overall adverse effects of heavy metals on marine organisms were alleviated by OA, leading to a neutral impact of heavy metals in combination with OA. However, different taxonomic groups showed large variabilities in their responses, with microalgae being the most sensitive when exposed to heavy metals and OA, and having the highest proportion of antagonistic interactions. Furthermore, the variations in interaction type frequencies are related to climate regions and heavy metal properties, with antagonistic interactions accounting for the highest proportion in temperate regions (28%) and when exposed to Zn (52%). Our study provides a comprehensive insight into the interactive effects of OA and HM on marine organisms, and highlights the importance of further investigating the responses of different marine taxonomic groups from various geographic locations to the combined stress of OA and HM.
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The Southern Ocean diatom Pseudo-nitzschia subcurvata flourished better under simulated glacial than interglacial ocean conditions: combined effects of CO2 and iron
Published 19 January 2022 Science ClosedTags: Antarctic, biological response, growth, laboratory, metals, multiple factors, phytoplankton
The ‘Iron Hypothesis’ suggests a fertilization of the Southern Ocean by increased dust deposition in glacial times. This promoted high primary productivity and contributed to lower atmospheric pCO2. In this study, the diatom Pseudo-nitzschia subcurvata, known to form prominent blooms in the Southern Ocean, was grown under simulated glacial and interglacial climatic conditions to understand how iron (Fe) availability (no Fe or Fe addition) in conjunction with different pCO2 levels (190 and 290 μatm) influences growth, particulate organic carbon (POC) production and photophysiology. Under both glacial and interglacial conditions, the diatom grew with similar rates. In comparison, glacial conditions (190 μatm pCO2 and Fe input) favored POC production by P. subcurvata while under interglacial conditions (290 μatm pCO2 and Fe deficiency) POC production was reduced, indicating a negative effect caused by higher pCO2 and low Fe availability. Under interglacial conditions, the diatom had, however, thicker silica shells. Overall, our results show that the combination of higher Fe availability with low pCO2, present during the glacial ocean, was beneficial for the diatom P. subcurvata, thus contributing more to primary production during glacial compared to interglacial times. Under the interglacial ocean conditions, on the other hand, the diatom could have contributed to higher carbon export due to its higher degree of silicification.
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Variability of trace metals in coastal and estuary: distribution, profile, and drivers
Published 7 January 2022 Science ClosedTags: metals, review
Highlights
- Trace-metal distributions in ocean systems have been classified into conservative-, nutrient-, and scavenged-type profiles.
- Several variability drivers of trace metals may be involved in differences of metal distribution in particular ocean systems.
- The availability of dissolved trace metals is likely to increase in the future due to increasing SST, decreasing pH or decreasing DO.
- Suspended matter which generally derives from terrestrial input plays a role in determining the fate of trace metals
- The study findings improve our understanding of trace-metal characteristics in the marine environment.
Abstract
Ongoing global changes such as increasing sea-surface temperatures, decreasing acidity levels, and expanding oxygen-minimum zone may impact on the biogeochemical cycles of trace metals in ocean systems. Each trace metal has unique characteristics and a distinctive distribution pattern controlled by chemical, biological, and physical processes that occur in ocean systems. The correlations of variability drivers in trace metals are interesting topics for investigation. Following up on ocean research in the coastal and estuary area, we specifically review the distribution of trace metals in seawater and suspended and surface sediment. The marginal seas usually feature significant terrestrial inputs accompanied by several active water-mass currents. The purpose of this review is to provide an overview of variability related to trace-metal distribution in coastal and estuary systems and to specifically describe the distribution, profile and drivers that affect trace metals variability.
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Integrative assessment of sediments affected by CO2 enrichment: a case study in the Bay of Santos—SP, Brazil
Published 5 January 2022 Science ClosedTags: biological response, community composition, crustaceans, echinoderms, laboratory, metals, multiple factors, otherprocess, performance, reproduction, sediment, South Atlantic, toxicants
CO2 enrichment in the marine environment caused by leakages from carbon capture and storage technologies may occur over operational procedures. An integrated approach using weight-of-evidence was applied to assess the environmental risk associated with the acidification caused by CO2 enrichment in coastal sediments from Santos (Brazil). Chemical analyses (metal(loid)s and organic contaminant (e.g., hydrocarbons), toxicity tests (amphipods mortality, sea-urchin embryo-larval development) and macro-benthic community structure alteration assessment were performed with different acidified scenarios (pH 8.0–6.0) for two stations with different contamination degrees. These lines of evidence were statistically analyzed and integrated (multivariate analysis and ANOVA). Results of toxicity showed significant chronic effects starting at pH 7.0 while acute effects were observed starting at pH 6.5. The macro-benthic community integrity showed significant differences for all treatments at the Piaçaguera channel station, considered to be moderately contaminated. Results from the multivariate analysis correlated toxic effects and increase in the mobility of some elements with acidification. Also, the biological indexes were correlated with concentrations of dissolved Zn in seawater. The pH of 6.0 was extremely toxic for marine life due to its high acidification and metal bioavailability. The approach herein identified and discriminated the origin of the degradation caused by the acidification related to the enrichment of CO2.
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Equilibrium calculations of iron speciation and apparent iron solubility in the Celtic Sea at ambient seawater pH using the NICA-Donnan model
Published 14 December 2021 Science ClosedTags: biogeochemistry, metals, modeling, multiple factors, North Atlantic, regionalmodeling
We used a combined ion pairing – organic matter speciation model (NICA-Donnan) to predict the organic complexation of iron (Fe) at ambient pH and temperature in the Celtic Sea. We optimized our model by direct comparison with Fe speciation determined by Adsorptive Cathodic Stripping Voltammetry using the added Fe-binding ligand 1-nitroso-2-naphthol (HNN) in the presence and absence of natural organic matter. We compared determined Fe speciation with simulated titrations obtained via application of the NICA-Donnan model with four different NICA parameter sets representing a range of binding site strengths and heterogeneities. We tested the assumption that binding sites scale to dissolved organic carbon (DOC) concentrations in marine waters. We found that a constant low DOC concentration resulted in an improved fit of our titration data to the simulated titrations, suggesting that inputs of autochthonous marine DOM may not increase the heterogeneity or concentrations of Fe binding sites. Using the optimal parameter set, we calculated pFe(III)´ (−log(∑Fe(OH)i3−i)) and apparent Fe(III) solubility (SFe(III)app) at ambient pH and temperature in the water column of the Celtic Sea. SFe(III)app was defined as the sum of aqueous inorganic Fe(III) species and Fe(III) bound to DOM formed at a free Fe (Fe3+) concentration equal to the limiting solubility of Fe hydroxide (Fe(OH)3(s)). SFe(III)app was within range of the determined dissolved Fe concentrations observed after winter mixing on the shelf and in waters >1500 m depth at our most offshore stations. Our study supports the hypothesis that the ocean dissolved Fe inventory is controlled by the interplay between Fe solubility and Fe binding by organic matter, although the overall number of metal binding sites in the marine environment may not be directly scalable to DOC concentrations.
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Prospective life cycle assessment of metal commodities obtained from deep-sea polymetallic nodules
Published 13 December 2021 Science ClosedTags: metals, policy
Highlights
- A Life Cycle Assessment of commodities from polymetallic nodules was performed.
- Climate change, photochemical oxidant formation and acidification were considered.
- The main hotspots are at onshore processes (e.g., hydrometallurgical processing).
- 38% reduction in carbon footprint can be observed, when comparing to terrestrial.
- Deep-sea operations may contribute significantly to the growing demand of metals.
Abstract
Sustainable metal supply will be essential to achieve climate and sustainability goals (e.g., Paris agreement), for instance by providing the necessary raw materials for renewable energy infrastructure systems. The potential exploitation of mineral resources from the deep sea (e.g., polymetallic nodules) can play a major role in this supply. A holistic environmental analysis is needed, in order to consider the entire value chain of the products obtained out of deep-sea exploitation. Therefore, the objective of this study was to perform a prospective life cycle assessment (LCA) of deep-sea-sourced commodities and compare it to equivalent products obtained from terrestrial mining. It considered as reference flow one tonne of (dry) nodules, using a cradle-to-gate approach up to the final metal commodities, analyzing the delivery to the market of 10.5 kg of copper, 12.8 kg of nickel, 2.3 kg of cobalt and 311.3 kg of ferromanganese. Three environmental impact categories were analyzed, i.e., climate change, acidification and photochemical oxidant formation. Overall, onshore activities (e.g., hydrometallurgical processing) are the main hotspots for environmental impacts of metals sourced from the deep sea; offshore activities play a minor role in the value chain. While photochemical oxidant formation impacts would be similar to terrestrial alternatives, the deep-sea-sourced commodities can bring environmental gains in the order of 38% for climate change and up to 72% for acidification. As this study shows, a strategic selection of the location for onshore processing of the polymetallic nodules is key to target cleaner production, not only because of the distance from the nodules site, but especially because of the available energy mix. The results should be interpreted with care, though, due to intrinsic limitations of the LCA study, e.g., the prospective nature of this study, the limited access to terrestrial mining data, amongst others. Nonetheless, regardless the limitations a prospective LCA imposes, this study highlights some important potential benefits that commodities from deep-sea polymetallic nodules can bring to society with respect to three important environmental impacts.
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Effect of increased CO2 on iron-light-CO2 co-limitation of growth in a marine diatom
Published 3 December 2021 Science ClosedTags: biological response, growth, laboratory, light, metals, multiple factors, photosynthesis, physiology, phytoplankton
Light affects iron (Fe) growth requirements in marine phytoplankton while CO2 can influence energy allocation and light sensitivity. Therefore, ongoing increases in seawater CO2 concentrations could impact the growth of Fe- and light-limited phytoplankton. In this study, Phaeodactylum tricornutum was used as a model diatom to examine the interactive effects of Fe, light, and CO2 on photosynthesis, growth, and protein expression in marine phytoplankton. Low concentration of biologically available inorganic iron (Fe′) and low-light intensity decreased specific rates of carbon (C)-fixation and growth, and the two together had an even greater effect, indicating a co-limitation. Increased partial pressure of CO2 from its current value (400 μatm) to 750 μatm had no effect at growth sufficient levels of Fe and light, but increased C-fixation and growth rate under Fe or light limitation, and had an even greater effect in Fe and light co-limited cells. The results suggest that ongoing increases in CO2 may increase C-fixation rates in Fe- and light-limited and co-limited regions, which cover at least 30% of the ocean. Measurements of photosynthetic proteins in photosystems II and I, and transcripts of proteins involved in CO2 concentrating mechanisms (CCMs), photorespiration, and antioxidant protection, suggest that the benefit of increased CO2 in the Fe- and light-limited cells was from a downregulation of CCMs and resultant decreased demands for energy supplied from photosynthesis, and from decreased rates of photorespiration, which consumes photosynthetically produced ATP and NADPH. A decrease in oxidative stress with increased CO2 also contributed.
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CO2-driven seawater acidification increases cadmium toxicity in a marine copepod
Published 2 December 2021 Science ClosedTags: biological response, crustaceans, laboratory, metals, multiple factors, physiology, toxicants, zooplankton
Highlights
- Copepods were interactively exposed to higher pCO2 (1000 μatm) and Cd (500 μg/L).
- Elevated pCO2 significantly increased Cd bioaccumulation in Tigriopus japonicus.
- Copepods enhanced energy production and stress response to counteract Cd toxicity.
- Increased pCO2 aggravated Cd-induced oxidative damage and apoptosis.
- Seawater acidification will potentially boost Cd toxicity in marine copepods.
Abstract
Here, we examined the 48-h acute toxicity of cadmium (Cd) in the marine copepod Tigriopus japonicus under two pCO2 concentrations (400 and 1000 μatm). Subsequently, T. japonicus was interactively exposed to different pCO2 (400, 1000 μatm) and Cd (control, 500 μg/L) treatments for 48 h. After exposure, biochemical and physiological responses were analyzed for the copepods. The results showed that the 48-h LC50 values of Cd were calculated as 12.03 mg/L and 9.08 mg/L in T. japonicus, respectively, under 400 and 1000 μatm pCO2 conditions. Cd exposure significantly promoted Cd exclusion/glycolysis, detoxification/stress response, and oxidative stress/apoptosis while it depressed that of antioxidant capacity. Intriguingly, CO2-driven acidification enhanced Cd bioaccumulation and its toxicity in T. japonicus. Overall, our study provides a mechanistic understanding about the interaction between seawater acidification and Cd pollution in marine copepods.
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Exacerbation of copper pollution toxicity from ocean acidification: a comparative analysis of two bivalve species with distinct sensitivities
Published 23 November 2021 Science ClosedTags: biological response, BRcommunity, laboratory, metals, molecular biology, mollusks, multiple factors, physiology, toxicants
Highlights
- OA aggravates the toxicity of Cu in both clams and scallops.
- Scallops were more sensitive to the toxicity of Cu and/or OA than clams.
- OA and Cu lead to increased protein turnover, disturbed cytoskeleton.
- OA and Cu lead to apoptosis and suppressed energy metabolism pathway.
Abstract
In estuarine ecosystems, bivalves experience large pH fluctuations caused by the anthropogenic elevation of atmospheric CO2 and Cu pollution. This study investigates whether Cu toxicity increases indiscriminately in two bivalve species from different estuarine habitats as a result of elevated Cu bioaccumulation in acidified seawater. This was carried out by evaluating the effects of Cu exposure on two bivalve species (clams and scallops) for 28 d, at a series of gradient pH levels (pH 8.1, 7.8, and 7.6). The results demonstrated an increase in the Cu content in the soft tissues of clams and scallops in acidified seawater. Cu toxicity increased under acidified seawater by affecting the molecular pathways, physiological function, biochemical responses, and health status of clams and scallops. An iTRAQ-based quantitative proteomic analysis showed increased protein turnover, disturbed cytoskeleton and signal transduction pathways, apoptosis, and suppressed energy metabolism pathways in the clams and scallops under joint exposure to ocean acidification and Cu. The integrated biomarker response results suggested that scallops were more sensitive to Cu toxicity and/or ocean acidification than clams. The proteomic results suggested that the increased energy metabolism and suppressed protein turnover rates may contribute to a higher resistivity to ocean acidification in clams than scallops. Overall, this study provides molecular insights into the distinct sensitivities between two bivalve species from different habitats under exposure to ocean acidification and/or Cu. The findings emphasize the aggravating impact of ocean acidification on Cu toxicity in clams and scallops. The results show that ocean acidification and copper pollution may reduce the long-term viability of clams and scallops, and lead to the degradation of estuarine ecosystems.
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Toxicological effects of cadmium on the immune response and biomineralization of larval flounder Paralichthys olivaceus under seawater acidification
Published 22 November 2021 Science ClosedTags: biological response, fish, laboratory, metals, molecular biology, multiple factors, North Pacific, physiology, reproduction, toxicants
Highlights
- Seawater acidification and Cd cause innate immunosuppression in flounder larvae.
- Both stressors induce the activities of biomineralization-related enzymes.
- Cd exposure significantly affects the expressions of immune-related genes.
- Seawater acidification aggravates Cd toxicity to immune function of larvae.
Abstract
Seawater acidification can cause threats to both calcifying and uncalcifying marine organisms, affecting their acid-base regulatory functions like immune system and biomineralization. Marine pollutants, such as cadmium (Cd) that is globally distributed in coastal ecosystems, do not affect organisms alone but commonly as combined stressors. To investigate the toxicological effects of Cd on the immune and biomineralization of marine fishes under seawater acidification, flounder Paralichthys olivaceus was exposed to seawater acidification (control (pH 8.10), 7.70 and 7.30) and Cd exposure (control (0.36 μg L−1), 0.01 and 0.15 mg L−1 Cd) for 49 days from embryonic stage until they became settled. Immune and biomineralization-related biomarkers of flounder at the end of exposure were investigated. Results showed that single seawater acidification and Cd exposure or combined exposure significantly affected the immune system-related enzyme activities. Specifically, lysozyme (LZM) activity was significantly inhibited by single seawater acidification and Cd exposure, indicating innate immunosuppression under two stressors. Contents of IgM, HSP70 and MT were induced by seawater acidification or Cd exposure, indicating a detoxification mechanism that responded to the stressors. The expressions of immune-related genes were upregulated (hsp70 and mt) or downregulated (lzm) under Cd exposure. Of the biomineralization-related enzymes, activities of carbonic anhydrase (CA), Na+/K+-ATPase and Ca2+-ATPase increased under seawater acidification and Cd exposure, a potential mechanism in response to changes of acid-base balance induced by the stressors. Generally, immune and biomineralization of the flounder responded more sensitively to Cd exposure than seawater acidification. Seawater acidification aggravated the toxicological effects of Cd exposure on the two physiological functions, while high Cd exposure augmented their responses to seawater acidification.
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Chapter 14 – Inter-relationship between dissolved lead and sediment lead in the backdrop of climate change induced acidification
Published 28 October 2021 Science ClosedTags: chemistry, field, Indian, metals, multiple factors, sediment
The surface water pH, dissolved lead and biologically available lead in the surface sediment were monitored for 30 years in three different stations of coastal West Bengal namely Shankarpur, Kakdwip and Ajmalmari. The gradual decrease of surface water pH played a significant role in the process of compartmentation of heavy metals in the coastal ecosystem. It is observed that lowering of pH triggered the process of transference of heavy metals from the sediment to the overlying aqueous system. The correlation coefficient values (for Shankarpur, dissolved Pb × sediment Pb =-0.888, p < 0.01; for Kakdwip, dissolved Pb × sediment Pb =-0.817, p < 0.01 and for Ajmalmari, dissolved Pb × sediment Pb =-0.8810, p < 0.01, respectively), support our findings. The role of climate change induced acidification is confirmed through this study.
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Lithium elemental and isotope systematics of modern and cultured brachiopods: implications for seawater evolution
Published 12 October 2021 Science ClosedTags: Antarctic, biological response, brachiopods, Indian, laboratory, metals, morphology, multiple factors, North Pacific, paleo, physiology, South Pacific, temperature
Lithium has proven a powerful tracer of weathering processes and chemical seawater evolution. Skeletal components of marine calcifying organisms, and in particular brachiopods, present promising archives of Li signatures. However, Li incorporation mechanisms and potential influence from biological processes or environmental conditions require a careful assessment. In order to constrain Li systematics in brachiopod shells, we present Li concentrations and isotope compositions for 11 calcitic brachiopod species collected from six different geographic regions, paralleled with data from culturing experiments where brachiopods were grown under varying environmental conditions and seawater chemistry (pH–pCO2, temperature, Mg/Ca ratio). The recent brachiopod specimens collected across different temperate and polar environments showed broadly consistent δ7Li values ranging from 25.2 to 28.1‰ (with mean δ7Li of 26.9 ± 1.5‰), irrespective of taxonomic rank, indicating that incorporation of Li isotopes into brachiopod shells is not strongly affected by vital effects related to differences among species. This results in Δ7Licalcite–seawater values (per mil difference in 7Li/6Li between brachiopod calcite shell and seawater) from −2.9‰ to −5.8‰ (with mean Δ7Licalcite–seawater value of −3.6‰), which is larger than the Δ7Licalcite–seawater values calculated based on data from planktonic foraminifera (~0‰ to ~−4‰). This range of values is further supported by results from brachiopods cultured experimentally. Under controlled culturing conditions simulating the natural marine environment, the Δ7Licalcite–seawater for Magellania venosa was −2.5‰ and not affected by an increase in temperature from 10 to 16 °C. In contrast, a decrease in Mg/Ca (or Li/Ca) ratio of seawater by addition of CaCl2 as well as elevated pCO2, and hence low-pH conditions, resulted in an increased Δ7Licalcite-seawater up to −4.6‰. Collectively, our results indicate that brachiopods represent valuable archives and provide an envelope for robust Li-based reconstruction of seawater evolution over the Phanerozoic.
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Effects of ocean acidification on marine primary producers and related ecological processes under multiple stressors
Published 6 October 2021 Science ClosedTags: algae, calcification, metals, multiple factors, photosynthesis, physiology, review
Although the individual effects of ocean acidification (OA), warming, solar UV radiation, deoxygenation and heavy metal pollution on marine producers are well-studied, their interactive effects are still unclear, strongly limiting our ability to project the ecological consequences of ocean climate changes. This chapter aims to provide an overview of our understanding the eco-physiological effects of OA and its combination with warming, solar UV radiation, deoxygenation and heavy metals. While OA is known to enhance photorespiration in both diatoms and green macroalgae, it enhances growth of coastal diatoms and other macroalgae that are adapted to fluctuating diel pH changes and then potentially enhances its contribution to carbon sequestration in coastal waters. OA is supposed to decrease pelagic primary productivity under multiple stressors (e.g., in combination with ultraviolet radiation, deoxygenation, warming), especially in oligotrophic waters, due to insufficient repairing or improvising processes that require both macro- and trace nutrients for syntheses of required proteins. Under influences of OA, macroalgal communities would shift toward non-calcifying species; diatoms become less abundance in phytoplankton assemblages. OA decreases calcification in algal calcifiers and exposes them to more harmful UV radiation, leading to a further decline of photosynthesis. Therefore, both the magnitude and direction of response of microalgae and macroalgae to OA largely depend on the levels of other environmental drivers (e.g., warming, deoxygenation). OA also exerts tremendous impacts on marine food webs. Total fatty acids and the ratio of long-chain polyunsaturated to saturated fatty acids of microalgae decrease, while some toxic secondary metabolites (such as phenolic compounds) accumulate under OA conditions, indicating a decline of food quality. This decline of food quality in primary producers can be transferred to secondary producers and negatively affect them (e.g., decrease in growth and reproduction). Taken together, OA can influence the biochemical compositions and contents in primary producers and their transfer to higher trophic levels and marine food webs is likely to be destabilized.
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Environmental risk of nickel in aquatic Arctic ecosystems
Published 7 September 2021 Science ClosedTags: Arctic, metals, multiple factors, review, toxicants
Highlights
- Elevated concentrations of Ni occur near mining/smelting operations in the Arctic
- There is a lack of Ni exposure scenarios in coastal, estuarine, and marine waters.
- Freshwater Ni bioavailability follows spatial trends in dissolved organic carbon.
- A critical gap to Ni risk assessment is a lack of toxicity data with Arctic species.
- Climate change will affect Ni exposure and may influence its effects in the Arctic.
Abstract
The Arctic faces many environmental challenges, including the continued exploitation of its mineral resources such as nickel (Ni). The responsible development of Ni mining in the Arctic requires establishing a risk assessment framework that accounts for the specificities of this unique region. We set out to conduct preliminary assessments of Ni exposure and effects in aquatic Arctic ecosystems. Our analysis of Ni source and transport processes in the Arctic suggests that fresh, estuarine, coastal, and marine waters are potential Ni-receiving environments, with both pelagic and benthic communities being at risk of exposure. Environmental concentrations of Ni show that sites with elevated Ni concentrations are located near Ni mining operations in freshwater environments, but there is a lack of data for coastal and estuarine environments near such operations. Nickel bioavailability in Arctic freshwaters seems to be mainly driven by dissolved organic carbon (DOC) concentrations with bioavailability being the highest in the High Arctic, where DOC levels are the lowest. However, this assessment is based on bioavailability models developed from non-Arctic species. At present, the lack of chronic Ni toxicity data on Arctic species constitutes the greatest hurdle toward the development of Ni quality standards in this region. Although there are some indications that polar organisms may not be more sensitive to contaminants than non-Arctic species, biological adaptations necessary for life in polar environments may have led to differences in species sensitivities, and this must be addressed in risk assessment frameworks. Finally, Ni polar risk assessment is further complicated by climate change, which affects the Arctic at a faster rate than the rest of the world. Herein we discuss the source, fate, and toxicity of Ni in Arctic aquatic environments, and discuss how climate change effects (e.g., permafrost thawing, increased precipitation, and warming) will influence risk assessments of Ni in the Arctic.
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Ocean acidification exacerbates copper toxicity in both juvenile and adult stages of the green tide alga Ulva linza
Published 12 August 2021 Science ClosedTags: algae, biological response, metals, morphology, multiple factors, photosynthesis, physiology, toxicants
Highlights
- Seawater acidification alleviated the toxicity of low Cu levels on Ulva linza.
- Increased Cu concentration would exacerbate toxicity and inhibit the grown of thalli.
- Two stages of U. linza have same responses to high CO2 and Cu concentration.
Abstract
The toxicity of heavy metals to coastal organisms can be modulated by changes in pH due to progressive ocean acidification (OA). We investigated the combined impacts of copper and OA on different stages of the green macroalga Ulva linza, which is widely distributed in coastal waters, by growing the alga under the addition of Cu (control, 0.125 (medium, MCu), and 0.25 (high) μM, HCu) and elevated pCO2 of 1,000 μatm, predicted in the context of global change. The relative growth rates decreased significantly in both juvenile and adult thalli at HCu under OA conditions. The net photosynthetic and respiration rates, as well as the relative electron transfer rates for the adult thalli, also decreased under the combined impacts of HCu and OA, although no significant changes in the contents of photosynthetic pigments were detected. Our results suggest that Cu and OA act synergistically to reduce the growth and photosynthetic performance of U. linza, potentially prolonging its life cycle.
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Chapter five – Interactive effects of ocean acidification and other environmental factors on marine organisms
Published 20 July 2021 Science ClosedTags: biological response, metals, multiple factors, review, salinity
In recent decades, the marine environment has been seriously affected by various anthropogenic activities (e.g., deforestation, fossil fuel combustion, and disordered discharges of pollutants). As a consequence, a range of changes in seawater environmental factors have taken place in oceans around the world, including increased temperature, reduced pH and dissolved oxygen, salinity fluctuation, and many other anomalous alterations in environmental factors, and these changes have aroused concerns from scientists. It has been widely reported that these changes in environmental factors would impact marine organisms severely. Meanwhile, it is worth noting that the environmental stressors mentioned above are rarely occurring independently in nature. Thus marine organisms are usually threatened by many different environmental stressors, and there would be complex and unpredicted interactions among the stressors. Generally, the interactive effects varied among additive (total effect equal to the sum of individual effects), synergistic (total effect greater than the sum of individual effects), or antagonistic (total effect less than the sum of individual effects), depending on the species and life stages of the studied organism, and the nature of the stressors themselves. It is necessary to figure out the interactive effects among various environmental stressors on specific marine organisms to accurately predict their physiological states and population dynamics under future climate scenarios. Therefore in this chapter, we summarize the related experiments in the last 20 years to discuss the interactive effects of ocean acidification (OA) combined with four other typical environmental stressors, namely ocean warming, hypoxia, salinity fluctuation, and heavy metal pollution, on marine organisms according to previously published studies. The authors hope that the contents of this chapter provide some basic information about the interactive effects of OA and the other four environmental factors for readers who are interested in this subject area.
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