FRINK Linked Data Fragments server

Matches in SemOpenAlex for { <https://semopenalex.org/work/W1493755659> ?p ?o ?g. }

• W1493755659 endingPage "4" @default.
• W1493755659 startingPage "1" @default.
• W1493755659 abstract "For the field of aquatic trace metal biogeochemistry, quantitatively linking the in situ chemical speciation of dissolved trace metals to the physiological responses of phytoplankton poses a grand challenge, the solution to which requires the contributions of phycologists, limnologists, oceanographers, and chemists. Using new analytical tools, chemists can measure the in situ speciation−the distribution of a metal (only cationic are considered here) among ions complexed by water (the free or aquo ion), by inorganic ligands such as OH− or Cl−, and by organic ligands such as fulvic acid−of most ecologically-relevant metals (Batley et al. 2004). Using equilibrium models to calculate concentrations of metal species in experimental media, phycologists have built an extensive body of research into the relationships between metal speciation and the biological responses of cultured phytoplankton (Twiss et al. 2001). And, using increasingly sophisticated methods of sampling and analysis, limnologists and oceanographers have observed in situ biological responses to changes in metal availability (and commensurate changes in speciation), such as in large-scale additions of iron to marine ecosystems (Rue and Bruland 1997; Timmermans et al. 1998; Maldonado et al. 2001). The premise unifying much of this work is that the dependencies of biological responses on the concentrations of different metal species measured in the laboratory can be combined with in situ speciation measurements to predict and/or explain observable in situ biological responses. The report by Vigneault and Campbell in this issue is an important milestone towards verifying this premise, particularly for freshwater ecosystems. For some metals, multiple species contribute to biological responses. For example, neutral, lipophilic metal ion complexes are taken up passively (Phinney and Bruland 1994), whereas complexes of redox-active metals are subject to cell-surface redox reactions that cause the complex to dissociate and permit the metal ion to be readily taken up by algae (Jones et al. 1987). Experimental studies of such processes typically observe correlations between the response and the concentration of the “bioavailable” species. However, for metal uptake, the concentration of free metal ions most often controls the biological response to a metal. This “free ion model”−which grew out of seminal work by Sunda and Guillard (1976) and Morel (1983) and coworkers−has arguably served as the field's organizing paradigm. The free ion model (FIM) follows from a simple premise: that equilibrium exists between the free metal ions in solution and the metal ions bound to transport enzymes (or other physiologically-active sites) on algal cell membranes. The aqueous free ion concentration then serves as a reproducible scale of metal ion reactivity, much as temperature defines the scale for thermal energy. Reflecting this thermodynamic basis, the preponderance of evidence supporting the “free ion model” (FIM) has come from studies using experimental media containing synthetic chelators, which permit experimenters to buffer free metal ion concentrations at defined values without directly measuring them. To predict in situ biological responses from such experimental work and in situ measurements (or models) of metal speciation generally requires making the assumption, which we may term the “NOM corollary” of the FIM, that the organism only responds to the free-metal ion concentration in solution, regardless of the nature of the metal complexes in solution. In other words, the sole effect of NOM is to complex the metal in solution and in doing so it behaves exactly as a synthetic ligand would behave. The high level of confidence in both the FIM and its NOM corollary is reflected in the development and widespread adoption of the Biotic Ligand Model (Di Toro et al. 2001; Gorsuch et al. 2003), which applies the FIM to predict biological responses in general in aquatic organisms on the basis of modeled metal complexation by NOM and competition among the metal ions, H+ and hardness cations for binding to the putative transporter. Although undeniable differences in composition, structure, and size between natural organic ligands and synthetic chelators exist, there has been a paucity of work testing the NOM corollary. Most reports in which metal chelation by NOM is inferred by measuring algal response to the metal do not include measurements of metal speciation and therefore can only qualitatively test the NOM corollary, as discussed in the authoritative reviews of the subject by Campbell (1995) and Campbell et al. (2002). Thus, the report in this volume by Vigneault and Campbell is a milestone because it demonstrates that the functional relationship between free Cd2+ ion concentration and metal uptake rate by two freshwater algae, Pseudokirchneriella subcapitata and Chlamydomonas reinhardtii, measured in media containing ligands from humic material and environmentally-relevant metal concentrations, is in fact unchanged from the relationship observed in media containing the synthetic chelator NTA. That close agreement is observed even without resort to logarithmically-scaled data is as much a testimony to the care taken in their work as to the correctness of the FIM and NOM corollary. Nevertheless, they do not suggest that universal application of the FIM (or the NOM corollary) is now warranted. Instead Vigneault and Campbell recommend carefully examining each combination of metal, organism, and type of NOM. Given the magnitude of this task, knowing when exceptions to the FIM and NOM corollary are most likely to occur is exceedingly important. Campbell and coworkers have led the effort to experimentally test this question and explore the limits of the FIM in general. Their work and synthesis of the literature has identified three key conditions that must be met in order for the FIM and the NOM corollary to hold: i) the NOM must exert no physiological effects on the organism of interest, ii) no metal-NOM complexes may be taken up by alternate mechanisms, and iii) non-equilibrium effects (diffusion-limitation or kinetic control) must not influence uptake rates. Note that the first condition has little to do with the FIM per se, the second concerns cases where the FIM is generally not at all appropriate to apply, and the third represents cases where dramatic departures from FIM-like behavior may be observed (see below). Effects of NOM on phytoplankton physiology are well documented, although the resulting influences on metal uptake are just beginning to be understood (Campbell et al. 1997; Slaveykova et al. 2002; Vigneault et al. 2000). NOM adsorbs on the surfaces of phytoplankton, thereby altering the surface charge, the passive permeability of cell membranes, and potentially the functioning of transporters. An indirect physiological effect of NOM has been reported by Parent et al. (1996), who found that amelioration of Al3+ toxicity in Chlorella pyrenoïdosa by soil humic acid was not in accord with the FIM, but instead resulted the humic acid enhancing the P supply and/or reducing the disruption of membranes by Al3+ through the formation of ternary phospholipid-Al-HA complexes. Similarly, Slaveykova et al. (2003) suggested that the enhancement in uptake of Pb2+ by Chlorella kesslerii in the presence of NOM relative to uptake in media with synthetically-chelated Pb2+ was due to changes in the algal surface charge. Alternate metal transport mechanisms include passive absorption of neutral, lipophilic metal-NOM complexes and algal-mediated reduction of metal-NOM complexes followed by subsequent metal ion uptake. If either of these mechanisms caused uptake at significant rates, non-FIM dependence of biological responses on metal speciation would be observed with NOM present. Metal complexes are known to adsorb to algal surfaces and affect membrane passive permeability (Campbell et al. 1997; Vigneault et al. 2000). This effect enhances uptake rates of lipophilic metal complexes−Cd(DDC)2−a low pH (Boullemant et al. 2004). The reduction of FeIII-chelates, including EDTA (Weger 1999; Herbik et al. 2002; Weger et al. 2002) and siderophore complexes (Maldonado and Price 2001), has also been shown to be a significant mechanism for enhancing metal uptake in algae. This mechanism has great ecological relevance (Hutchins et al. 1999) since a significant fraction of FeIII may chelated in aquatic systems, particularly in the ocean. Phytoplankton also reduce CuII complexes (Jones et al. 1987), a process that may enhance uptake under conditions where Cu-deficient growth conditions (Hudson 1998). A third alternate non-FIM transport mechanism is “piggy-back” uptake of metal complexes, such as acquisition of Ag-thiosulfate complexes by an algal sulfate transporter (Fortin and Campbell 2000). In accordance with the NOM corollary, “piggy-back” uptake should be inhibited by the fulvic and humic components of NOM, which competitively inhibit formation of the transported complex and are themselves unlikely form transportable complexes. “Piggy-back” uptake may cause the non-FIM response of P. subcapitata to Cd2+ in the presence of citrate, a low molecular weight, assimilable organic ligand (Errécalde and Campbell 2002). Non-equilibrium effects, although detectable even with synthetic chelators, are metal-and organism-specific (Hudson 1998; Campbell et al. 2002). Apparent uptake of labile metal complexes can occur if they dissociate in the boundary layer of an aquatic organism under conditions where uptake of the free ion is rapid relative to its diffusion to the cell. Metal complexes with weak inorganic and metal-organic ligand complexes are likely to be bioavailable in such cases. If the rate constants for the relevant complexation reactions and cellular transport parameters are known (often they are not), diffusion-reaction models may be used to model metal uptake (Pinheiro and van Leeuwen 2001). Nevertheless, conditions under which enhanced diffusion is likely to affect uptake may be predictable to some degree (Sunda and Huntsman 1998; Hudson 1998). One final class of non-equilibrium effects, kinetically-controlled facilitated transport, has been confirmed for Fe (Hudson and Morel 1990) and suggested as an explanation for the anomalous speciation dependence of Hg2+ uptake by bacteria (Golding et al. 2002), and has the potential to cause significant deviations from FIM behavior for metals that are complexed by weak ligands to a significant extent. To summarize, we may inquire whether Vigneault and Campbell's finding that algal Cd2+ uptake fits with both the FIM and the NOM corollary could be predicted using the lines of reasoning presented above. If so, the number of individual organism/metal/NOM combinations that must be investigated experimentally in the future may be reduced. At present the empirical understanding of direct NOM effects (condition 1) is insufficient to predict direct NOM influences on the uptake of Cd2+ and most other metals. Nevertheless, since Cd-NOM complexes are not known to be particularly hydrophobic and Cd exists only in a single oxidation state in aquatic systems there is no reason to expect alternate uptake mechanisms to be important (condition 2). Furthermore, as Vigneault and Campbell (2005) suggest, the finding that Cd2+ uptake rates are significantly below the diffusion limit (condition 3) is consistent with Cd being a non-essential element that is inadvertently taken up by a divalent metal ion transporter, such as one whose normal function is to acquire Mn2+. Finally, it may be noted that purely chemical reasoning about the kinetics of Mn2+, Zn2+, Cd2+, and Cu2+ uptake by such a divalent metal ion transporter led to the conclusion that of these metals, Cd2+ was most likely to exhibit true FIM-type equilibrium between the solution and transporter (Hudson 1998). Careful work such as that reported by Vigneault and Campbell (2005) is essential for resolving developing a basis for anticipating which combinations of alga, NOM, and metal will behave according to the FIM and which will not." @default.
• W1493755659 created "2016-06-24" @default.
• W1493755659 date "2005-02-01" @default.
• W1493755659 modified "2023-09-28" @default.
• W1493755659 title "TRACE METAL UPTAKE, NATURAL ORGANIC MATTER, AND THE FREE-ION MODEL" @default.
• W1493755659 cites W1491340377 @default.
• W1493755659 cites W1633519431 @default.
• W1493755659 cites W2002173519 @default.
• W1493755659 cites W2006101651 @default.
• W1493755659 cites W2014423490 @default.
• W1493755659 cites W2017341031 @default.
• W1493755659 cites W2021221294 @default.
• W1493755659 cites W2026648591 @default.
• W1493755659 cites W2028236026 @default.
• W1493755659 cites W2040573857 @default.
• W1493755659 cites W2042926961 @default.
• W1493755659 cites W2063114761 @default.
• W1493755659 cites W2065146436 @default.
• W1493755659 cites W2065368978 @default.
• W1493755659 cites W2065683387 @default.
• W1493755659 cites W2076100780 @default.
• W1493755659 cites W2085955757 @default.
• W1493755659 cites W2105234635 @default.
• W1493755659 cites W2106488183 @default.
• W1493755659 cites W2112246761 @default.
• W1493755659 cites W2116097006 @default.
• W1493755659 cites W2132770035 @default.
• W1493755659 cites W2132918635 @default.
• W1493755659 cites W2144179667 @default.
• W1493755659 cites W2156473134 @default.
• W1493755659 cites W2171193723 @default.
• W1493755659 cites W4235045259 @default.
• W1493755659 cites W4253225062 @default.
• W1493755659 cites W4378759224 @default.
• W1493755659 doi "https://doi.org/10.1111/j.1529-8817.2005.41101.x" @default.
• W1493755659 hasPublicationYear "2005" @default.
• W1493755659 type Work @default.
• W1493755659 sameAs 1493755659 @default.
• W1493755659 citedByCount "18" @default.
• W1493755659 countsByYear W14937556592012 @default.
• W1493755659 countsByYear W14937556592013 @default.
• W1493755659 countsByYear W14937556592014 @default.
• W1493755659 countsByYear W14937556592015 @default.
• W1493755659 countsByYear W14937556592017 @default.
• W1493755659 countsByYear W14937556592018 @default.
• W1493755659 countsByYear W14937556592022 @default.
• W1493755659 crossrefType "journal-article" @default.
• W1493755659 hasConcept C107872376 @default.
• W1493755659 hasConcept C138885662 @default.
• W1493755659 hasConcept C151730666 @default.
• W1493755659 hasConcept C185592680 @default.
• W1493755659 hasConcept C18903297 @default.
• W1493755659 hasConcept C191897082 @default.
• W1493755659 hasConcept C192562407 @default.
• W1493755659 hasConcept C2776608160 @default.
• W1493755659 hasConcept C2778566039 @default.
• W1493755659 hasConcept C41895202 @default.
• W1493755659 hasConcept C48743137 @default.
• W1493755659 hasConcept C544153396 @default.
• W1493755659 hasConcept C75291252 @default.
• W1493755659 hasConcept C86803240 @default.
• W1493755659 hasConceptScore W1493755659C107872376 @default.
• W1493755659 hasConceptScore W1493755659C138885662 @default.
• W1493755659 hasConceptScore W1493755659C151730666 @default.
• W1493755659 hasConceptScore W1493755659C185592680 @default.
• W1493755659 hasConceptScore W1493755659C18903297 @default.
• W1493755659 hasConceptScore W1493755659C191897082 @default.
• W1493755659 hasConceptScore W1493755659C192562407 @default.
• W1493755659 hasConceptScore W1493755659C2776608160 @default.
• W1493755659 hasConceptScore W1493755659C2778566039 @default.
• W1493755659 hasConceptScore W1493755659C41895202 @default.
• W1493755659 hasConceptScore W1493755659C48743137 @default.
• W1493755659 hasConceptScore W1493755659C544153396 @default.
• W1493755659 hasConceptScore W1493755659C75291252 @default.
• W1493755659 hasConceptScore W1493755659C86803240 @default.
• W1493755659 hasIssue "1" @default.
• W1493755659 hasLocation W14937556591 @default.
• W1493755659 hasOpenAccess W1493755659 @default.
• W1493755659 hasPrimaryLocation W14937556591 @default.
• W1493755659 hasRelatedWork W1484855306 @default.
• W1493755659 hasRelatedWork W1996950723 @default.
• W1493755659 hasRelatedWork W2001629084 @default.
• W1493755659 hasRelatedWork W2038710408 @default.
• W1493755659 hasRelatedWork W2052570512 @default.
• W1493755659 hasRelatedWork W2075362594 @default.
• W1493755659 hasRelatedWork W2116877927 @default.
• W1493755659 hasRelatedWork W2201283928 @default.
• W1493755659 hasRelatedWork W2271359201 @default.
• W1493755659 hasRelatedWork W2953261018 @default.
• W1493755659 hasVolume "41" @default.
• W1493755659 isParatext "false" @default.
• W1493755659 isRetracted "false" @default.
• W1493755659 magId "1493755659" @default.
• W1493755659 workType "article" @default.