Arsenic cycling in marine systems: degradation of arsenosugars to arsenate in decomposing algae, and preliminary evidence for the formation of recalcitrant arsenic

2011 ◽  
Vol 8 (1) ◽  
pp. 44 ◽  
Author(s):  
Jana Navratilova ◽  
Georg Raber ◽  
Steven J. Fisher ◽  
Kevin A. Francesconi
Keyword(s):  
Direct Contact ◽  
Marine Algae ◽  
Marine Alga ◽  
Inorganic Arsenic ◽  
Arsenic Species ◽  
Preliminary Evidence ◽  
Arsenic Compounds ◽  
Marine Systems ◽  
Inorganic Species ◽  
Unknown Structure

Environmental context Despite high levels of complex organoarsenic compounds in marine organisms, arsenic in seawater is present almost entirely as inorganic species. We examine the arsenic products from a marine alga allowed to decompose under simulated natural coastal conditions, and demonstrate a multi-step conversion of organic arsenicals to inorganic arsenic. The results support the hypothesis that the arsenic marine cycle begins and ends with inorganic arsenic. Abstract Time series laboratory experiments were performed to follow the degradation of arsenic compounds naturally present in marine algae. Samples of the brown alga Ecklonia radiata, which contains three major arsenosugars, were packed into 12 tubes open to air at one end only, and allowed to naturally decompose under moist conditions. During the subsequent 25 days, single tubes were removed at intervals of 1–4 days; their contents were cut into four sections (from open to closed end) and analysed for arsenic species by HPLC/ICPMS following an aqueous methanol extraction. In the sections without direct contact with air, the original arsenosugars were degraded primarily to arsenate via two major intermediates, dimethylarsinoylethanol (DMAE) and dimethylarsinate (DMA). The section with direct contact with air degraded more slowly and significant amounts of arsenosugars remained after 25 days. We also report preliminary data suggesting that the amount of non-extractable or recalcitrant arsenic (i.e. insoluble after sequential extractions with water/methanol, acetone, and hexane) increased with time. Furthermore, we show that treatment of the pellet with 0.1-M trifluoroacetic acid at 95°C solubilises a significant amount of this recalcitrant arsenic, and that the arsenic is present mainly as a cationic species of currently unknown structure.

Arsenic species in seafood: Origin and human health implications

2010 ◽  
Vol 82 (2) ◽  
pp. 373-381 ◽  
Author(s):  
Kevin A. Francesconi
Keyword(s):  
Human Health ◽  
Arsenic Species ◽  
Marine Organisms ◽  
Current Status ◽  
Human Toxicology ◽  
Important Food ◽  
Arsenic Compounds ◽  
Inorganic Species ◽  
Organoarsenic Compound ◽  
High Concentrations

The presence of arsenic in marine samples was first reported over 100 years ago, and shortly thereafter it was shown that common seafood such as fish, crustaceans, and molluscs contained arsenic at exceedingly high concentrations. It was noted at the time that this seafood arsenic was probably present as an organically bound species because the concentrations were so high that if the arsenic had been present as an inorganic species it would certainly have been toxic to the humans consuming seafood. Investigations in the late 1970s identified the major form of seafood arsenic as arsenobetaine [(CH3)3As+CH2COO–], a harmless organoarsenic compound which, following ingestion by humans, is rapidly excreted in the urine. Since that work, however, over 50 additional arsenic species have been identified in marine organisms, including many important food products. For most of these arsenic compounds, the human toxicology remains unknown. The current status of arsenic in seafood will be discussed in terms of the possible origin of these compounds and the implications of their presence in our foods.

Arsenic compounds in tropical marine ecosystems: similarities between mangrove forest and coral reef

2009 ◽  
Vol 6 (3) ◽  
pp. 226 ◽  
Author(s):  
Somkiat Khokiattiwong ◽  
Narumol Kornkanitnan ◽  
Walter Goessler ◽  
Sabine Kokarnig ◽  
Kevin A. Francesconi
Keyword(s):  
Marine Algae ◽  
Arsenic Species ◽  
Mangrove Ecosystem ◽  
Marine Ecosystems ◽  
Dry Mass ◽  
Aqueous Extracts ◽  
Mangrove Forests ◽  
Arsenic Compound ◽  
Arsenic Compounds ◽  
Marine Animals

Environmental context. Despite the widespread occurrence of arsenobetaine in marine animals the origin of this arsenic compound remains unknown. A current hypothesis is that arsenobetaine is formed from more complex arsenic compounds found in marine algae. To test this hypothesis, we examined the arsenic compounds in a mangrove ecosystem where algae play a limited role in primary productivity. Abstract. Marine algae are known to bioaccumulate arsenic and transform it into arsenosugars, which are thought to be precursors of the major arsenic compound, arsenobetaine, found in marine animals. Marine ecosystems based on mangrove forests have high nutrient input from mangrove leaves, and thus provide a unique opportunity to study the cycling of arsenic in a marine system where algae are not the dominant food source. Two mangrove forests in Phuket, Thailand were selected as sampling sites for this study. For comparison, samples were also collected from two coral reef sites at and near Phuket. The samples collected included mangrove leaves, corals, algae, molluscs, fish and crustaceans. Arsenic contents in the samples and in aqueous extracts of the samples were determined by hydride generation atomic absorption spectrometry following a dry-ashing mineralisation procedure, and arsenic species were determined in the aqueous extracts by HPLC-MS (mainly ICPMS). Mangrove leaves contained only low concentrations of total arsenic (0.10–0.73 mg kg–1 dry mass) and the aqueous extracts thereof contained inorganic arsenic species, methylarsonate and dimethylarsinate, but arsenosugars were not detected. The total mean arsenic contents (3.2–86 mg kg–1 dry mass) of the animals from the mangrove ecosystem, however, were typical of those found in animal samples from other marine ecosystems. Similarly the arsenic compounds present were typical of those in animals from other marine ecosystems comprising mainly arsenobetaine with smaller quantities of other common arsenicals including arsenosugars, arsenocholine, tetramethylarsonium ion, trimethylarsine oxide and dimethylarsinate. A trimethylated arsenosugar, which is not commonly reported in marine organisms, was a significant arsenical (6–8% of total As) in some gastropod species from the mangrove ecosystem. The coral samples contained mainly arsenosugars and arsenobetaine, and the other animals collected from the coral ecosystem contained essentially the same pattern of arsenicals found for the mangrove animals. The data suggest that food chains based on algae are not necessary for animals to accumulate large concentrations of arsenobetaine.

Distribution of arsenic species in an open seagrass ecosystem: relationship to trophic groups, habitats and feeding zones

2012 ◽  
Vol 9 (1) ◽  
pp. 77 ◽  
Author(s):  
A. Price ◽  
W. Maher ◽  
J. Kirby ◽  
F. Krikowa ◽  
E. Duncan ◽  
...  
Keyword(s):  
Inorganic Arsenic ◽  
Arsenic Species ◽  
Trophic Levels ◽  
Arsenic Content ◽  
Trophic Groups ◽  
Marine Systems ◽  
Seagrass Ecosystem ◽  
High Concentrations ◽  
Species Specific ◽  
Arsenic Source

Environmental contextAlthough arsenic occurs at high concentrations in many marine systems, the influencing factors are poorly understood. The arsenic content of sediments, detritus, suspended particles and organisms have been investigated from different trophic levels in an open seagrass ecosystem. Total arsenic concentrations and arsenic species were organism-specific and determined by a variety of factors including exposure, diet and the organism physiology. AbstractThe distribution and speciation of arsenic within an open marine seagrass ecosystem in Lake Macquarie, NSW, Australia is described. Twenty-six estuarine species were collected from five trophic groups (autotrophs, suspension-feeders, herbivores, detritivores and omnivores, and carnivores). Sediment, detritus, epibiota and micro-invertebrates were also collected and were classified as arsenic source samples. There were no significant differences in arsenic concentrations between trophic groups and between pelagic and benthic feeders. Benthic-dwelling species generally contained higher arsenic concentrations than pelagic-dwelling species. Sediments, seagrass blades and detritus contained mostly inorganic arsenic (50–90 %) and arsenoribosides (10–26 %), with some methylarsonate (9.4–14.6 %) and dimethyarsinate (7.9–9.7 %) in seagrass blades and detritus. Macroalgae contained mostly arsenoribosides (40–100 %). Epibiota and other animals contained predominately arsenobetaine (63–100 %) and varying amounts of dimethyarsinate (0–26 %), monomethyarsonate (0–14.6 %), inorganic arsenic (0–2 %), trimethylarsenic oxide (0–6.6 %), arsenocholine (0–12 %) and tetramethylarsonium ion (0–4.5 %). It was concluded that arsenic concentrations and species within the organisms of the Lake Macquarie ecosystem are species-specific and determined by a variety of factors including exposure, diet and the physiology of the organisms.

The degradation of arsenoribosides from Ecklonia radiata tissues decomposed in natural and microbially manipulated microcosms

2014 ◽  
Vol 11 (3) ◽  
pp. 289 ◽  
Author(s):  
Elliott G. Duncan ◽  
William A. Maher ◽  
Simon D. Foster ◽  
Frank Krikowa ◽  
Katarina M. Mikac
Keyword(s):  
Species Diversity ◽  
Degradation Products ◽  
Inorganic Arsenic ◽  
Arsenic Species ◽  
Microbial Composition ◽  
Ecklonia Radiata ◽  
Marine Systems ◽  
Degradation Step ◽  
Sand Sediments ◽  
Macro Algae

Environmental context Arsenoribosides are the major arsenic species in marine macro-algae, yet inorganic arsenic is the major arsenic species found in seawater. We investigated the degradation of arsenoribosides associated with Ecklonia radiata by the use of microcosms containing both natural and autoclaved seawater and sand. The decomposition and persistence of arsenic species was linked to the use of autoclaved seawater and sand, which suggests that arsenoriboside degradation is governed by the microbial composition of microenvironments within marine systems. Abstract We investigated the influence of microbial communities on the degradation of arsenoribosides from E. radiata tissues decomposing in sand and seawater-based microcosms. During the first 30 days, arsenic was released from decomposing E. radiata tissues into seawater and sand porewaters in all microcosms. In microcosms containing autoclaved seawater and autoclaved sand, arsenic was shown to persist in soluble forms at concentrations (9–18µg per microcosm) far higher than those present initially (~3µg per microcosm). Arsenoribosides were lost from decomposing E. radiata tissues in all microcosms with previously established arsenoriboside degradation products, such as thio-arsenic species, dimethylarsinoylethanol (DMAE), dimethylarsenate (DMA) and arsenate (AsV) observed in all microcosms. DMAE and DMA persisted in the seawater and sand porewaters of microcosms containing autoclaved seawater and autoclaved sand. This suggests that the degradation step from arsenoribosides → DMAE occurs on algal surfaces, whereas the step from DMAE → AsV occurs predominantly in the water-column or sand–sediments. This study also demonstrates that disruptions to microbial connectivity (defined as the ability of microbes to recolonise vacant habitats) result in alterations to arsenic cycling. Thus, the re-cycling of arsenoribosides released from marine macro-algae is driven by microbial complexity plus microbial connectivity rather than species diversity as such, as previously assumed.

Speciation of Six Arsenic Compounds in Korean Seafood Samples by HPLC-ICP-MS

2005 ◽  
Vol 277-279 ◽  
pp. 431-437 ◽  
Author(s):  
Kyung Su Park ◽  
Jeong Sook Kim ◽  
Hyo Min Lee ◽  
Hee Soo Pyo ◽  
Soon Tae Kim ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
High Performance ◽  
Certified Reference Materials ◽  
Arsenic Speciation ◽  
Inorganic Arsenic ◽  
Arsenic Species ◽  
Arsenic Compounds ◽  
Inductively Coupled ◽  
Plasma Mass Spectrometry ◽  
Fish And Shellfish

Extracts of 33 samples of seaweed, shrimp, fish and shellfish, including two certified reference materials, were investigated for their contents of arsenic compounds (arsenic speciation).An anion exchange high performance liquid chromatography procedure was optimized to separate six arsenic compounds present in the seafood samples with dynamic reaction gas cell by inductively coupled plasma mass spectrometry. The concentration of each species in the sample were: arsenobetaines - 0.019-1.04 mg/kg, arsenocholine - 0.033-69.0 mg/kg, arseniousacid - ND-1.25 mg/kg, dimethylarsinate - ND-3.75 mg/kg, monomethylarsonate - ND-8.33 mg/kg, arsenic acid - ND-0.55 mg/kg. Additionally, unknown arsenic species were present in most of samples. The intake of inorganic arsenic via ingestion of the seafood samples that were analyzed did not represent a toxicological problem to humans. The limits of detection (LOD) were in the range of 0.5-2.5 µg/kg .

Arsenic metabolism in cyanobacteria

2016 ◽  
Vol 13 (4) ◽  
pp. 577 ◽  
Author(s):  
Shin-ichi Miyashita ◽  
Chisato Murota ◽  
Keisuke Kondo ◽  
Shoko Fujiwara ◽  
Mikio Tsuzuki
Keyword(s):  
Inorganic Arsenic ◽  
Arsenic Species ◽  
Dimethylarsinic Acid ◽  
Arsenic Compound ◽  
Arsenic Compounds ◽  
Arsenic Metabolism ◽  
Methylarsonic Acid ◽  
Membrane Bound ◽  
Arsenic Transport ◽  
High Concentrations

Environmental context Cyanobacteria are ecologically important, photosynthetic organisms that are widely distributed throughout the environment. They play a central role in arsenic transformations in terms of both mineralisation and formation of organoarsenic species as the primary producers in aquatic ecosystems. In this review, arsenic resistance, transport and biotransformation in cyanobacteria are reviewed and compared with those in other organisms. Abstract Arsenic is a toxic element that is widely distributed in the lithosphere, hydrosphere and biosphere. Some species of cyanobacteria can grow in high concentrations of arsenate (pentavalent inorganic arsenic compound) (100mM) and in low-millimolar concentrations of arsenite (trivalent inorganic arsenic compound). Arsenate, which is a molecular analogue of phosphate, is taken up by cells through phosphate transporters, and inhibits oxidative phosphorylation and photophosphorylation. Arsenite, which enters the cell through a concentration gradient, shows higher toxicity than arsenate by binding to sulfhydryl groups and impairing the functions of many proteins. Detoxification mechanisms for arsenic in cyanobacterial cells include efflux of intracellular inorganic arsenic compounds, and biosynthesis of methylarsonic acid and dimethylarsinic acid through methylation of intracellular inorganic arsenic compounds. In some cyanobacteria, ars genes coding for an arsenate reductase (arsC), a membrane-bound protein involved in arsenic efflux (arsB) and an arsenite S-adenosylmethionine methyltransferase (arsM) have been found. Furthermore, cyanobacteria can produce more complex arsenic species such as arsenosugars. In this review, arsenic metabolism in cyanobacteria is reviewed, compared with that in other organisms. Knowledge gaps remain regarding both arsenic transport (e.g. uptake of methylated arsenicals and excretion of arsenate) and biotransformation (especially production of lipid-soluble arsenicals). Further studies in these areas are required, not only for a better understanding of the role of cyanobacteria in the circulation of arsenic in aquatic environments, but also for their application to arsenic bioremediation.

scholarly journals The sorption of inorganic arsenic on modified sepiolite: Effect of hydrated iron(III)-oxide

2014 ◽  
Vol 79 (7) ◽  
pp. 815-828 ◽  
Author(s):  
Nikola Ilic ◽  
Slavica Lazarevic ◽  
Vladana Rajakovic-Ognjanovic ◽  
Ljubinka Rajakovic ◽  
Djordje Janackovic ◽  
...  
Keyword(s):  
Sorption Capacity ◽  
Arsenic Removal ◽  
Ph Value ◽  
Inorganic Arsenic ◽  
Arsenic Species ◽  
Deionized Water ◽  
Order Kinetic ◽  
Initial Ph ◽  
Order Kinetic Model ◽  
Pseudo Second Order

The sorption of inorganic arsenic species, As(III) and As(V), from water by sepiolite modified with hydrated iron(III) oxide was investigated at 25 ?C through batch studies. The influence of the initial pH value, the initial As concentrations, the contact time and types of water on the sorption capacity was investigated. Two types of water were used, deionized and groundwater. The maximal sorption capacity for As(III) from deionized water was observed at initial and final pH value 7.0, while the bonding of As(V) was observed to be almost pH independent for pH value in the range from 2.0 to 7.0, and the significant decrease in the sorption capacity was observed at pH values above 7.0. The sorption capacity at initial pH 7.0 was about 10 mg g?1 for As(III) and 4.2 mg g?1 for As(V) in deionized water. The capacity in groundwater was decreased by 40 % for As(III) and by 20 % for As(V). The Langmuir model and pseudo-second order kinetic model revealed good agreement with the experimental results. The results show that Fe(III)-modified sepiolite exhibits significant affinity for arsenic removal and it has a potential for the application in water purification processes.

Methylation of Arsenic by Freshwater Green Algae

1983 ◽  
Vol 40 (8) ◽  
pp. 1254-1257 ◽  
Author(s):  
M. D. Baker ◽  
P. T. S. Wong ◽  
Y. K. Chau ◽  
C. I. Mayfield ◽  
W. E. Inniss
Keyword(s):  
Green Algae ◽  
Lake Water ◽  
Sodium Arsenite ◽  
Basal Medium ◽  
Arsenic Species ◽  
Freshwater Ecosystems ◽  
Dimethylarsinic Acid ◽  
Additional Source ◽  
Arsenic Compounds ◽  
Methylarsonic Acid

Isolates from four genera of freshwater green algae were capable of methylating sodium arsenite in lake water and Bold's basal medium. Analysis of the liquid phase of the methylation flasks revealed the presence of methylarsonic acid, dimethylarsinic acid, and trimethylarsine oxide. Volatile arsine and methylarsines were not detected in the headspace gases presumably because of the inability of the algae to reduce completely the methylated–arsenic species. Although the algae varied with respect to their methylating abilities, the levels of methylated–arsenic compounds were always significantly higher when the algae were grown in lake water. This may have been due to the lower phosphate concentration in the lake water. We suggest that arsenic methylation by green algae constitutes an additional source for the formation and cycling of organo-arsenic compounds in freshwater ecosystems.

scholarly journals Arsenic speciation in food chains from mid-Atlantic hydrothermal vents

2012 ◽  
Vol 9 (2) ◽  
pp. 130 ◽  
Author(s):  
Vivien F. Taylor ◽  
Brian P. Jackson ◽  
Matthew R. Siegfried ◽  
Jana Navratilova ◽  
Kevin A. Francesconi ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Deep Sea ◽  
Hydrothermal Vents ◽  
Arsenic Speciation ◽  
Inorganic Arsenic ◽  
Food Sources ◽  
Arsenic Compounds ◽  
Marine Animals ◽  
Δ13c And Δ15n ◽  
Organic Arsenic

Environmental contextArsenic occurs in marine organisms at high levels and in many chemical forms. A common explanation of this phenomenon is that algae play the central role in accumulating arsenic by producing arsenic-containing sugars that are then converted into simpler organic arsenic compounds found in fish and other marine animals. We show that animals in deep-sea vent ecosystems, which are uninhabited by algae, contain the same organic arsenic compounds as do pelagic animals, indicating that algae are not the only source of these compounds. AbstractArsenic concentration and speciation were determined in benthic fauna collected from the Mid-Atlantic Ridge hydrothermal vents. The shrimp species, Rimicaris exoculata, the vent chimney-dwelling mussel, Bathymodiolus azoricus, Branchipolynoe seepensis, a commensal worm of B. azoricus and the gastropod Peltospira smaragdina showed variations in As concentration and in stable isotope (δ13C and δ15N) signature between species, suggesting different sources of As uptake. Arsenic speciation showed arsenobetaine to be the dominant species in R. exoculata, whereas in B. azoricus and B. seepensis arsenosugars were most abundant, although arsenobetaine, dimethylarsinate and inorganic arsenic were also observed, along with several unidentified species. Scrape samples from outside the vent chimneys covered with microbial mat, which is a presumed food source for many vent organisms, contained high levels of total As, but organic species were not detectable. The formation of arsenosugars in pelagic environments is typically attributed to marine algae, and the pathway to arsenobetaine is still unknown. The occurrence of arsenosugars and arsenobetaine in these deep sea organisms, where primary production is chemolithoautotrophic and stable isotope analyses indicate food sources are of vent origin, suggests that organic arsenicals can occur in a foodweb without algae or other photosynthetic life.

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