Posts Tagged 'metals'

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Different responses of phytoplankton and zooplankton communities to current changing coastal environments

Published 5 October 2022 Science Closed
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Marine plankton are faced with novel challenges associated with environmental changes such as ocean acidification, warming, and eutrophication. However, data on the effects of simultaneous environmental changes on complex natural communities in coastal ecosystems are relatively limited. Here we made a systematic analysis of biological and environmental parameters in the Bohai Sea over the past three years to suggest that plankton communities responded differently to current changing coastal environments, with the increase of phytoplankton and the decrease of zooplankton. These different changes of phyto- and zooplankton potentially resulted from the fact that both the effect of acidification as a result of pH decline and the effect of warming as a consequence of increasing temperature favored phytoplankton over zooplankton at present. Furthermore, water eutrophication and salinity as well as heavy metals Hg, Zn, and As had more or less diverse consequences for the dynamics of phytoplankton and zooplankton. Differently, with ongoing climate change, we also revealed that both phytoplankton and zooplankton would decrease in the future under the influence of interactions between acidification and warming.

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Bioaccumulation of inorganic and organic mercury in the cuttlefish Sepia officinalis: influence of ocean acidification and food type

Published 7 September 2022 Science Closed
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The bioaccumulation of mercury (Hg) in marine organisms through various pathways has not yet been fully explored, particularly in cephalopods. This study utilises radiotracer techniques using the isotope 203Hg to investigate the toxicokinetics and the organotropism of waterborne inorganic Hg (iHg) and dietary inorganic and organic Hg (methylHg, MeHg) in juvenile common cuttlefish Sepia officinalis. The effect of two contrasting CO2 partial pressures in seawater (400 and 1600 μatm, equivalent to pH 8.08 and 7.54 respectively) and two types of prey (fish and shrimp) were tested as potential driving factors of Hg bioaccumulation. After 14 days of waterborne exposure, juvenile cuttlefish showed a stable concentration factor of 709 ± 54 and 893 ± 117 at pH 8.08 and 7.54, respectively. The accumulated dissolved i203Hg was depurated relatively rapidly with a radiotracer biological half-life (Tb1/2) of 44 ± 12 and 55 ± 16 days at pH 8.08 and 7.54, respectively. During the whole exposure period, approximately half of the i203Hg was found in the gills, but i203Hg also increased in the digestive gland. When fed with 203Hg-radiolabelled prey, cuttlefish assimilated almost all the Hg provided (>95%) independently of the prey type. Nevertheless, the prey type played a major role on the depuration kinetics with Hg Tb1/2 approaching infinity in fish fed cuttlefish vs. 25 days in shrimp fed cuttlefish. Such a difference is explained by the different proportion of Hg species in the prey, with fish prey containing more than 80% of MeHg vs. only 30% in shrimp. Four days after ingestion of radiolabelled food, iHg was primarily found in the digestive organs while MeHg was transferred towards the muscular tissues. No significant effect of pH/pCO2 variation was observed during both the waterborne and dietary exposures on the bioaccumulation kinetics and tissue distribution of i203Hg and Me203Hg. Dietary exposure is the predominant pathway of Hg bioaccumulation in juvenile cuttlefish.

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Adaptation of a marine diatom to ocean acidification increases its sensitivity to toxic metal exposure

Published 7 September 2022 Science Closed
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Highlights

  • Adaptation to OA increased marine diatom’s sensitivity to heavy metals (HM).
  • OA-adapted cells decreased their growth and photosynthesis at high HM levels.
  • The increase in sensitivity is associated with reduced metabolic activity.

Abstract

Most previous studies investigating the interplay of ocean acidification (OA) and heavy metal on marine phytoplankton were only conducted in short-term, which may provide conservative estimates of the adaptive capacity of them. Here, we examined the physiological responses of long-term (~900 generations) OA-adapted and non-adapted populations of the diatom Phaeodactylum tricornutum to different concentrations of the two heavy metals Cd and Cu. Our results showed that long-term OA selected populations exhibited significantly lower growth and reduced photosynthetic activity than ambient CO2 selected populations at relatively high heavy metal levels. Those findings suggest that the adaptations to high CO2 results in an increased sensitivity of the marine diatom to toxic metal exposure. This study provides evidence for the costs and the cascading consequences associated with the adaptation of phytoplankton to elevated CO2 conditions, and improves our understanding of the complex interactions of future OA and heavy metal pollution in marine waters.

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Diel fluctuation superimposed on steady high pCO2 generates the most serious cadmium toxicity to marine copepods

Published 6 September 2022 Science Closed
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Graphical abstract

Coastal systems experience diel fluctuation of pCO2 and cadmium (Cd) pollution; nevertheless, the effect of fluctuating pCO2 on Cd biotoxicity is poorly known. In this study, we initially performed the isotopically enriched organism bioassay to label Tigriopus japonicus with 113Cd (5 μg/L) to determine the Cd accumulation rate constant (kaccu) under ambient (400 μatm) and steadily (1000 μatm) and fluctuatingly elevated (1000 ± 600 μatm) pCO2 conditions for 48 h. Next, T. japonicus was interactively subjected to the above pCO2 exposures at Cd (control, 5, and 500 μg/L) treatments for 7 d. Biochemical and physiological responses for copepods were analyzed. The results showed that steadily increased pCO2 facilitated Cd bioaccumulation compared to ambient pCO2, and it was more under fluctuating acidification conditions. Despite compensatory reactions (e.g., increased energy production), Cd ultimately induced oxidative damage and apoptosis. Meanwhile, combined treatment exhibited higher toxicity (e.g., increased apoptosis) relative to Cd exposure, and even more if fluctuating acidification was considered. Intriguingly, fluctuating acidification inhibited Cd exclusion in Cd-treated copepods compared to steady acidification, linking to higher Cd kaccu and bioaccumulation. Collectively, CO2-driven acidification could aggravate Cd toxicity, providing a mechanistic understanding of the interaction between seawater acidification and Cd pollution in marine copepods.

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Phytoplankton community shift in response to experimental Cu addition at the elevated CO2 levels (Arabian Sea, winter monsoon)

Published 5 September 2022 Science Closed
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Understanding phytoplankton community shifts under multiple stressors is becoming increasingly important. Among other combinations of stressors, the impact of trace metal toxicity on marine phytoplankton under the ocean acidification scenario is an important aspect to address. Such multiple stressor studies are rare from the Arabian Sea, one of the highest productive oceanic provinces within the North Indian Ocean. We studied the interactive impacts of copper (Cu) and CO2 enrichment on two natural phytoplankton communities from the eastern and central Arabian Sea. Low dissolved silicate (DSi < 2 µM) favoured smaller diatoms (e.g. Nitzschia sp.) and non-diatom (Phaeocystis). CO2 enrichment caused both positive (Nitzschia sp. and Phaeocystis sp.) and negative (Cylindrotheca closterium, Navicula sp., Pseudo-nitzschia sp., Alexandrium sp., and Gymnodinium sp.) growth impacts. The addition of Cu under the ambient CO2 level (A-CO2) hindered cell division in most of the species, whereas Chla contents were nearly unaffected. Interestingly, CO2 enrichment seemed to alleviate Cu toxicity in some species (Nitzschia sp., Cylindrotheca closterium, Guinardia flaccida, and Phaeocystis) and increased their growth rates. This could be related to the cellular Cu demand and energy budget at elevated CO2 levels. Dinoflagellates were more sensitive to Cu supply compared to diatoms and prymnesiophytes and could be related to the unavailability of prey. Such community shifts in response to the projected ocean acidification, oligotrophy, and Cu pollution may impact trophic transfer and carbon cycling in this region.

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Integrative assessment of biomarker responses in Mytilus galloprovincialis exposed to seawater acidification and copper ions

Published 29 August 2022 Science Closed
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Graphical abstract

Highlights

  • Both OA and Cu ions caused physiological disturbances to the mussel.
  • Mussels have the ability to restore most of the tested parameters from the stress of OA and Cu ions.
  • Gills are more sensitive than digestive glands.
  • IBR analysis demonstrated the co-exposure caused the most brutal impact to the mussel.

Abstract

The interactive effects of ocean acidification (OA) and copper (Cu) ions on the mussel Mytilus galloprovincialis are not well understood. The underlying mechanisms also remain obscure. In this study, individuals of M. galloprovincialis were exposed for 28 days to 25 μg/L and 50 μg/L Cu ions at two pH levels (ambient level – pH 8.1; acidified level – pH 7.6). The mussels were then monitored for 56 days to determine their recovery ability. Physiological parameters (clearance rate and respiration rate), oxidative stress and neurotoxicity biomarkers (activities of superoxide dismutase, lipid peroxidation, catalase, and acetylcholinesterase), as well as the recovery ability of these parameters, were investigated in two typical tissues (i.e., gills and digestive glands). Results showed that (1) OA affected the bioconcentration of Cu in the gills and digestive glands of the mussels; (2) both OA and Cu can lead to physiological disturbance, oxidative stress, cellular damage, energy metabolism disturbance, and neurotoxicity on M. galloprovincialis; (3) gill is more sensitive to OA and Cu than digestive gland; (4) Most of the biochemical and physiological alternations caused by Cu and OA exposures in M. galloprovincialis can be repaired by the recovery experiments; (5) integrated biomarker response (IBR) analysis demonstrated that both OA and Cu ions exposure caused survival stresses to the mussels, with the highest effect shown in the co-exposure treatment. This study highlights the necessity to include OA along with pollutants in future studies to better elucidate the risks of ecological perturbations. The work also sheds light on the recovery of marine animals after short-term environmental stresses when the natural environment has recovered.

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Emergent interactive effects of climate change and contaminants in coastal and ocean ecosystems

Published 1 August 2022 Science Closed
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The effects of climate change (CC) on contaminants and their potential consequences to marine ecosystem services and human wellbeing are of paramount importance, as they pose overlapping risks. Here, we discuss how the interaction between CC and contaminants leads to poorly constrained impacts that affects the sensitivity of organisms to contamination leading to impaired ecosystem function, services and risk assessment evaluations. Climate drivers, such as ocean warming, ocean deoxygenation, changes in circulation, ocean acidification, and extreme events interact with trace metals, organic pollutants, excess nutrients, and radionuclides in a complex manner. Overall, the holistic consideration of the pollutants-climate change nexus has significant knowledge gaps, but will be important in understanding the fate, transport, speciation, bioavailability, toxicity, and inventories of contaminants. Greater focus on these uncertainties would facilitate improved predictions of future changes in the global biogeochemical cycling of contaminants and both human health and marine ecosystems.

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A global horizon scan of issues impacting marine and coastal biodiversity conservation

Published 12 July 2022 Science Closed
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The biodiversity of marine and coastal habitats is experiencing unprecedented change. While there are well-known drivers of these changes, such as overexploitation, climate change and pollution, there are also relatively unknown emerging issues that are poorly understood or recognized that have potentially positive or negative impacts on marine and coastal ecosystems. In this inaugural Marine and Coastal Horizon Scan, we brought together 30 scientists, policymakers and practitioners with transdisciplinary expertise in marine and coastal systems to identify new issues that are likely to have a significant impact on the functioning and conservation of marine and coastal biodiversity over the next 5–10 years. Based on a modified Delphi voting process, the final 15 issues presented were distilled from a list of 75 submitted by participants at the start of the process. These issues are grouped into three categories: ecosystem impacts, for example the impact of wildfires and the effect of poleward migration on equatorial biodiversity; resource exploitation, including an increase in the trade of fish swim bladders and increased exploitation of marine collagens; and new technologies, such as soft robotics and new biodegradable products. Our early identification of these issues and their potential impacts on marine and coastal biodiversity will support scientists, conservationists, resource managers and policymakers to address the challenges facing marine ecosystems.

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Surviving in a changing ocean. Tolerance to acidification might affect the susceptibility of polychaetes to chemical contamination

Published 28 June 2022 Science Closed
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Graphical abstract

Highlights

  • CO2 vent systems are natural laboratory for studying the effects of multiple stressors.
  • We assess the effects of OA and pollution, using polychaetes naturally exposed to OA.
  • Limited influence of OA on the activity of antioxidant enzymes in polychaetes.
  • Polychaetes from the vent were more susceptible to acetone but more tolerant to Cu respect to controls.
  • Tolerance to OA could influence polychaete susceptibility to environmental pollution.

Abstract

This study aimed to assess the combined effects of ocean acidification (OA) and pollution to the polychaete Syllis prolifera inhabiting the CO2 vent system of the Castello Aragonese (Ischia Island, Italy). We investigated the basal activities of antioxidant enzymes in organisms from the acidified site and from an ambient-pH control site in two different periods of the year. Results showed a limited influence of acidified conditions on the functionality of the antioxidant system. We then investigated the responsiveness of individuals living inside the CO2 vent compared to those from the control to face exposure to acetone and copper. Results highlighted a higher susceptibility of organisms from the vent to acetone and a different response of antioxidant enzymes in individuals from the two sites. Conversely, a higher tolerance to copper was observed in polychaetes from the acidified-site with respect to controls, but any significant oxidative stress was induced at sublethal concentrations.

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Abiotic stress in algae: response, signaling and transgenic approaches

Published 23 May 2022 Science Closed
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High salinity, nutrient deficiency, heavy metals, desiccation, temperature fluctuations, and ultraviolet radiations are major abiotic stress factors considered inhospitable to algal growth and development in natural and artificial environments. All these stressful conditions cause effects on algal physiology and thus biochemical functioning. For instance, long-term exposure to hyper/hypo salinity conditions inhibits cell differentiation and reduces growth. Photosynthesis is completely blocked in algae’s dehydrated state, resulting in photoinhibition or photodamage. The limitation of nutrients in aquatic environments inhibits primary production via regulating phytoplankton community development and structure. Hence, in response to these stressful conditions, algae develop plenty of cellular, physiological, and morphological defences to survive and thrive. The conserved and generalized defence responses in algae include the production of secondary metabolites, desaturation of membrane lipids, activation of reactive species scavengers, and accumulation of compatible solutes. Moreover, a well-coordinated and timely response to such stresses involves signal perception and transduction mainly via phytohormones that could sustain algae growth under abiotic stress conditions. In addition, the combination of abiotic stresses and plant hormones could further elevate the biosynthesis of metabolites and enhance the ability of algae to tolerate abiotic stresses. This review aims to present different kinds of stressful conditions confronted by algae and their physiological and biochemical responses, the role of phytohormones in combatting these conditions, and, last, the future transgenic approaches for improving abiotic stress tolerance in algae.

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A triple threat: ocean warming, acidification and rare earth elements exposure triggers a superior antioxidant response and pigment production in the adaptable Ulva rigida

Published 18 May 2022 Science Closed
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Highlights

  • La and Gd were accumulated in 24h;
  • Elimination of La and Gd did not occur in U. rigida;
  • La and Gd showed different accumulation and elimination patterns in future predicted scenarios;
  • La and Gd triggered an efficient antioxidant defence response in U. rigida;
  • REE and climate change exposure requested a superior antioxidant response.

Abstract

Anthropogenic increased atmospheric CO2 concentrations will lead to a drop of 0.4 units of seawater pH and ocean warming up to 4.8°C by 2100. Contaminant’s toxicity is known to increase under a climate change scenario. Rare earth elements (REE) are emerging contaminants, that until now have no regulation regarding maximum concentration and discharge into the environment and have become vital to new technologies such as electric and hybrid-electric vehicle batteries, wind turbine generators and low-energy lighting. Studies of REE, namely Lanthanum (La) and Gadolinium (Gd), bioaccumulation, elimination, and toxicity in a multi-stressor environment (e.g., warming and acidification) are lacking. Hence, we investigated the algae phytoremediation capacity, the ecotoxicological responses and total chlorophyll and carotenoid contents in Ulva rigida during 7 days of co-exposure to La or Gd (15 µg L−1 or 10 µg L−1, respectively), and warming and acidification. Additionally, we assessed these metals elimination, after a 7-day phase. After one day of experiment La and Gd clearly showed accumulation/adsorption in different patterns, at future conditions. Unlikely for Gd, Warming and Acidification contributed to the lowest La accumulation, and increased elimination. Lanthanum and Gd triggered an adequate activation of the antioxidant defence system, by avoiding lipid damage. Nevertheless, REE exposure in a near-future scenario triggered an overproduction of ROS that requested an enhanced antioxidant response. Additionally, an increase in total chlorophyll and carotenoids could also indicate an unforeseen energy expense, as a response to a multi-stressor environment.

Continue reading ‘A triple threat: ocean warming, acidification and rare earth elements exposure triggers a superior antioxidant response and pigment production in the adaptable Ulva rigida’

Single and combined ecotoxicological effects of ocean warming, acidification and lanthanum exposure on the surf clam (Spisula solida)

Published 16 May 2022 Science Closed
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Highlights

  • Lanthanum was bioaccumulated after just one day of exposure.
  • Elimination did not occur during the 7-day depuration phase.
  • The biochemical response was triggered, however damage occurred.
  • The La toxic effects are more severe in a changing world.

Abstract

Lanthanum (La) is one of the most abundant emergent rare earth elements. Its release into the environment is enhanced by its use in various industrial applications. In the aquatic environment, emerging contaminants are one of the stressors with the ability to compromise the fitness of its inhabitants. Warming and acidification can also affect their resilience and are another consequence of the growing human footprint on the planet. However, from information gathered in the literature, a study on the effects of ocean warming, acidification, and their interaction with La was never carried out. To diminish this gap of knowledge, we explored the effects, combined and as single stressors, of ocean warming, acidification, and La (15 μg L−1) accumulation and elimination on the surf clam (Spisula solida). Specimens were exposed for 7 days and depurated for an additional 7-day period. Furthermore, a robust set of membrane-associated, protein, and antioxidant enzymes and non-enzymatic biomarkers (LPO, HSP, Ub, SOD, CAT, GPx, GST, TAC) were quantified. Lanthanum was bioaccumulated after just one day of exposure, in both control and climate change scenarios. A 7-day depuration phase was insufficient to achieve control values and in a warming scenario, La elimination was more efficient. Biochemical response was triggered, as highlighted by enhanced SOD, CAT, GST, and TAC levels, however as lipoperoxidation was observed it was insufficient to detoxify La and avoid damage. The HSP was largely inhibited in La treatments combined with warming and acidification. Concomitantly, lipoperoxidation was highest in clams exposed to La, warming, and acidification combined. The results highlight the toxic effects of La on this bivalve species and its enhanced potential in a changing world.

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Increasing arsenic accumulation as an implication of climate change: a case study using red algae

Published 25 April 2022 Science Closed
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Climate change due to an increasing concentration of carbon dioxide in the atmosphere is a global issue. It can impact aquatic environments by affecting water flow, pollutant transformation and migration, and other toxicant-related effects. We assessed the interactive effects of temperature warming and pH changes on variations in accumulation of total arsenic (AsT) in the red alga Sarcodia suae at different levels of arsenite (AsIII). Result showed that AsT variations in the alga were moderated by significant joint effects of warming temperature and/or increasing pH levels and their interactions with increasing AsIII concentrations. Our study suggests possible deleterious impacts on macroalgal populations due to toxicological effects associated with prevailing environmental conditions. Therefore, improved pollution management, climate change adaptation, and mitigation strategies are needed to deal with current environmental issues and As aggravation.

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The biological uptake of dissolved iron in the changing Daya Bay, South China Sea: effect of pH and DO

Published 12 April 2022 Science Closed
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Highlights

  • Fe bioavailability affected by pH and DO regulates phytoplanktonic Fe uptake.
  • Nano-phytoplankton is more sensitive to the variation of seawater pH and DO.
  • Phytoplankton community tend to be miniaturized in the changing DYB.
  • Fe requirement in DYB goes higher accompanied with the phytoplankton miniaturization.
  • DYB is not an Fe-rich environment derived from the relative low Fe:C ratio.

Abstract

The oceanic acidification and coastal hypoxia have potential to enhance biological uptake of dissolved iron (Fe) by phytoplankton. In this study, the Fe uptake rate (FeUR) in Daya Bay was significantly negatively correlated with pH and dissolved oxygen (DO) (r = −0.81 and −0.73, respectively, p < 0.001). In addition, binary regression (FeUR = −1.45 × pH − 0.10 × DO + 13.64) also indicated that both pH and DO played key roles in FeUR variations. As pH and DO decreased, Fe uptake by phytoplankton was promoted, and the contribution of nano-phytoplankton to Fe uptake increased significantly, while that of pico-FeUR decreased. These will result in the phytoplankton community to be miniaturized and Fe requirement of phytoplankton goes higher, thereby leading changes of phytoplankton composition and coastal ecosystem. This study helps to understand how Fe could affect the coastal ecosystem under the increasing anthropogenic influences.

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Mangrove trace metal biogeochemistry response to global climate change

Published 8 April 2022 Science Closed
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This review discusses observed impacts from different climate change-driven pressures on mangrove’s role in modulating trace metal transfer at the land-ocean interface. It contributes to the literature in a global context and shows mangroves as mitigators or providing positive feedback to metal mobilization. Most chalcophile metals2+ accumulate in mangrove soils associated with sulfides while high sedimentation rates avoid their oxidation. Exudation of oxygen by roots fixates Fe, which co-precipitates metals as oxyhydroxides in the rhizosphere. These two biogeochemical processes reduce trace metal availability to plants and their mobility within estuaries. However, climate change-driven pressures alter this geochemical equilibrium. Increasing atmospheric CO2 and temperature, and the intensity and frequency of extreme climatic events, have proved to affect mangrove functioning and cover, but no direct observation on the impact on metal biogeochemistry is presently available, whereas sea level rise and saline intrusion impacts on the fate of metals have already been observed. Sea level rise increases erosion, that dissociates deposited sulfides releasing metals to the water column. Released metals adsorb onto suspended particles and can re-deposit in the estuary or are exported to continental shelf sediments. Saline intrusion may oxidize deeper sediment layers releasing metals to porewaters. Part of the mobilized metals may remain in solution complexed with DOM and have their bioavailability increased, as shown by high bioaccumulation factors and biomagnification and high metal concentrations in the estuarine biota, which results in higher human exposure through fisheries consumption. Since erosion occurs preferentially at the sea border and higher sedimentation at the higher reaches of the estuary, triggering mangroves migration landward, spatial gradients are formed, and shall be taken into consideration when planning mitigation or adaptation strategies. These observations suggest disruption of traditional humans dwelling in mangrove dominated coastlines by increasing contamination of coastal fisheries, often the principal protein source for those groups and an important source of income. Further research into the environmental and socioeconomic impacts of climate change driven alterations to metal biogeochemical processes in mangroves as contaminant levels are expected to increase.

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The combined effects of ocean acidification and copper on the physiological responses of the tropical coral Stylophora pistillata

Published 25 March 2022 Science Closed
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Highlights

  • Exposure to increased Cu concentrations suppressed coral calcification.
  • Calcification was suppressed further when exposed to Cu under high pCO2.
  • Respiration decreased after two weeks when stressors were applied in combination.

Abstract

A decrease in ocean pH of 0.3 units will likely double the proportion of dissolved copper (Cu) present as the free metal ion, Cu2+, the most bioavailable form of Cu, and one of the most common marine pollutants. We assess the impact of ocean acidification and Cu, separately and in combination, on calcification, photosynthesis and respiration of sub-colonies of a single tropical Stylophora pistillata colony. After 15 days of treatment, total calcification rates were significantly decreased in corals exposed to high seawater pCO2 (∼1000-μatm, 2100 scenario) and at both ambient (1.6–1.9 nmols) and high (2.5–3.6 nmols) dissolved Cu concentrations compared to controls. The effect was increased when both stressors were combined. Coral respiration rates were significantly reduced by the combined stressors after 2 weeks of exposure, indicating the importance of experiment duration. It is therefore likely rising atmospheric CO2 will exacerbate the negative effects of Cu pollution to S. pistillata.

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In contrast to diatoms, cryptophytes are susceptible to iron limitation, but not to ocean acidification

Published 18 March 2022 Science Closed
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Previous field studies in the Southern Ocean (SO) indicated an increased occurrence and dominance of cryptophytes over diatoms due to climate change. To gain a better mechanistic understanding of how the two ecologically important SO phytoplankton groups cope with ocean acidification (OA) and iron (Fe) availability, we chose two common representatives of Antarctic waters, the cryptophyte Geminigera cryophila and the diatom Pseudo-nitzschia subcurvata. Both species were grown at 2°C under different pCO2 (400 vs. 900 μatm) and Fe (0.6 vs. 1.2 nM) conditions. For P. subcurvata, an additional high pCO2 level was applied (1400 μatm). At ambient pCO2 under low Fe supply, growth of G. cryophila almost stopped while it remained unaffected in P. subcurvata. Under high Fe conditions, OA was not beneficial for P. subcurvata, but stimulated growth and carbon production of G. cryophila. Under low Fe supply, P. subcurvata coped much better with OA than the cryptophyte, but invested more energy into photoacclimation. Our study reveals that Fe limitation was detrimental for the growth of G. cryophila and suppressed the positive OA effect. The diatom was efficient in coping with low Fe, but was stressed by OA while both factors together strongly impacted its growth. The distinct physiological response of both species to OA and Fe limitation explains their occurrence in the field. Based on our results, Fe availability is an important modulator of OA effects on SO phytoplankton, with different implications on the occurrence of cryptophytes and diatoms in the future.

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Interactive effects of acidification and copper exposure on the reproduction and metabolism of coral endosymbiont Cladocopium goreaui

Published 16 March 2022 Science Closed
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Highlights

  • Acidification raised growth by Fv/Fm, nutrient uptake and biomolecular biosynthesis.
  • Copper pollution alone decreased algal reproduction through toxic effects.
  • Combined stressor repressed reproduction through downregulated aromatic amino acid.
  • Abstract

Ocean acidification resulting from increased CO2 and pollution from land-sourced toxicants such as copper have been linked to coral cover declines in coastal reef ecosystems. The impacts of ocean acidification and copper pollution on corals have been intensively investigated, whereas research on their effects on coral endosymbiont Symbiodiniaceae is limited. In this study, reproduction, photosynthetic parameters, nutrient accumulation and metabolome of Symbiodiniaceae Cladocopium goreaui were investigated after a weeklong treatment with acute CO2-induced acidification and copper ion. Acidification promoted algal reproduction through increased nutrients assimilation, upregulated citrate cycle and biomolecular biosynthesis pathway, while copper exposure repressed algal reproduction through toxic effects. The combined acidification and copper exposure caused the same decline in algal reproduction as copper exposure alone, but the upregulation of pentose phosphate pathway and the downregulation of aromatic amino acid biosynthesis. These results suggest that copper pollution could override the positive effects of acidification on the symbiodiniacean reproduction.

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Particulate iron bioavailability to phytoplankton in Antarctic and Arctic waters: effects of ocean acidification and the organic ligand EDTA

Published 1 March 2022 Science Closed
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Particulate iron (PFe) usually is not considered as a bioavailable iron fraction to phytoplankton. In this study we tested the bioavailability of one PFe species, goethite (α-FeO(OH)), to phytoplankton community in Southern Ocean under the effect of ocean acidification (OA) (pHT ca. 7.5) and representative concentration pathways (RCP) 8.5 condition (pCO2 ca. 1300 µatm), and to an Arctic diatom species, Nitzschia frigida, under the effect of the organic ligand, EDTA (using the commercially available salt disodium ethylenediaminetetraacetate dihydrate), as a chelator, respectively.

In March 2019, a natural phytoplankton community was sampled and used for the deck incubation experiment in the Southern Ocean. The sampling site was 68.10°S, 6.00° W, which was in the region of Queen Maud Land (Norwegian: Dronning Maud Land, DML). We observed marine biogeochemical performance of the phytoplankton community under OA. Different chemical and biological parameters during the incubation were determined, including dissolved iron (DFe), total acid leachable iron (TaLFe), macronutrients including nitrate (NO3-), phosphate (PO43-) and silicate, total pH (pHT), dissolved inorganic carbon (DIC), the concentration & fugacity of carbon dioxide (fCO2), chlorophyll a (Chla) concentration & in vivo fluorescence. The results show that the tested phytoplankton assemblage was more severely influenced by OA than iron bioavailability, especially under severe OA. Goethite, as one type of PFe, is insoluble under the tested OA scenarios. There could be PO43- remineralization in all treatments but species shift to diatoms only in ambient pH treatments (mild OA), which coincides with the judgement that OA impact is predominant in comparison to iron enrichment in this experiment. We should analyze phytoplankton species to test this hypothesis. OA can result in that phytoplankton launches Hv channel-mediated H+ efflux mechanism, carbon concentration mechanism (CCM) down-regulation of phytoplankton and the thriving of more tolerant species with more efficient CCM.

In April 2021, using an Arctic diatom species, Nitzschia frigida, we investigated the possibility of EDTA increasing goethite bioavailability to phytoplankton and photosynthetic performance by measuring relative electron transport rate (rETR) in the experiment performed at Trondheim Biological Station (Norwegian: Trondheim Biologiske Stasjon, TBS). The results show that elevating EDTA concentration can increase the bioavailability of goethite while decrease that of ferric chloride (FeCl3). This is inconclusive according to possibly negatively biased α (the slope of a typical P/E (photosynthesis/irradiance) curve), because it results in underestimation of goethite bioavailability under the influence of EDTA.

Further research regarding the combined effect of OA and EDTA on PFe bioavailability to phytoplankton is recommended.

Continue reading ‘Particulate iron bioavailability to phytoplankton in Antarctic and Arctic waters: effects of ocean acidification and the organic ligand EDTA’

Aluminium in aquatic environments: abundance and ecotoxicological impacts

Published 28 February 2022 Science Closed
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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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