Selenium metabolism in the Marine phytoplankters Tetraselmis tetrathele and Dunaliella minuta

Wrench, J. J.

doi:10.1007/bf00391135

Cited by 114 publications

(35 citation statements)

References 9 publications

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“…A possible explanation for the low cytoplasmic Se concentration is the shorter labeling period (36 h , under dark conditions), which may limit Se penetration into the algal cytoplasm. This element is mainly associated with soluble amino acids and small polypeptides (Wrench 1978, Fisher & Reinfelder 1991 in algal cytoplasm. The greatest deviation from the 1 :l relationship of AE and cytoplasmic distribution was found for Ag, Cd, and Zn, consistent with Wang & Fisher's (1996a) findings for these metals.…”

Section: Discussion Trace Element Assimilation From Foodmentioning

confidence: 99%

Kinetic determinations of trace element bioaccumulation in the mussel Mytilus edulis

Wang¹,

Fisher²,

Luoma³

1996

Mar. Ecol. Prog. Ser.

404

402

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ABSTRACT. Laboratory experiments employing radiotracer methodology were conducted to determine the assimilation efficiencies from ingested natural seston, the influx rates from the dissolved phase and the efflux rates of 6 trace elements (Ag, Am, Cd, Co. Se and Zn) in the mussel Mytilus edulis. A kinetic model was then employed to predict trace element concentration in mussel tissues in 2 locations for which mussel and environmental data are well described: South San Francisco Bay (California, USA) and Long Island Sound [New York, USA). Assimilation efficiencies from natural seston ranged from 5 to 18": for Ag, 0.6 to 1% for Am, 8 to 20% for Cd, 12 to 16% for CO, 28 to 34% for Se, and 32 to 41 ' :, for Zn. Differences in chlorophyll a concentration in ingested natural seston did not have significant impact on the assimilation of Am, CO, Se and Zn. The influx rate of elements from the dissolved phase increased with the dissolved concentration, conforming to Freundlich adsorption isotherms. The calculated dissolved uptake rate constant was greatest for Ag, followed by Zn > Am -; Cd > CO > Se. The estimated absorption efficiency from the d~ssolved phase was 1.53 % for Ag, 0.34 % for Am, 0.31 X for Cd, 0.11 % for CO, 0.03"' for Se and 0.89% for Zn. Salinity had an inverse effect on the influx rate from the dissolved phase and dissolved organic carbon concentration had no significant effect on trace element uptake. The calculated efflux rate constants for all elements ranged from 1.0 to 3.0% d-' The route of trace element uptake (food vs dissolved) and the duration of exposure to dissolved trace elements (12 h vs 6 d) did not significantly influence trace element efflux rates. A model which used the experimentally determined influx and efflux rates for each of the trace elements, following exposure from ingested food and from water, predicted concentrations of Ag. Cd, Se and Zn in mussels that were directly comparable to actual tissue concentrations independently measured in the 2 reference sites in national monitoring programs. Sensitivity analysis indicated that the total suspended solids load, which can affect mussel feeding activity, assimilation, and trace element concentration in the dissolved and particulate phases, can significantly influence metal bioaccumulation for particlereactive elements such as Ag and Am. For all metals, concentrations in mussels are proportionately related to total metal load in the water column and their assimilation efficiency from ingested particles. Further, the model predicted that over 96% of Se in mussels is obtained from ingested food, under conditions typical of coastal waters. For Ag, Am, Cd, CO and Zn, the relative contribution from the dissolved phase decreases significantly with increasing trace element parhtion coefficients for suspended particles and the assimilation efficiency in mussels of ingested trace elements, values range between 33 and 67% for Ag, 5 and 1 7 % for Am, 47 and 82% for Cd, 4 and 30% for CO, and 17 and 51 ?h for Zn.

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Section: Discussion Trace Element Assimilation From Foodmentioning

confidence: 99%

Kinetic determinations of trace element bioaccumulation in the mussel Mytilus edulis

Wang¹,

Fisher²,

Luoma³

1996

Mar. Ecol. Prog. Ser.

404

402

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“…2) indicates that these elements Mlow the same digestive pathway as organic C. These elements generally penetrate to a greater extent into the cytoplasm of algal cells than do the nonessential elemerts, which adsorb mostly onto cell surfaces (Reinfelder and Fisher 199 1). For example, Se may covalently bind to protein or nonprotein seleno-amino acids and exists in soluble forms in the cytoplasm (Wrench 1978;Fisher and Reinfelder 199 1). Zn is an essential enzyme cofactor in organisms.…”

Section: Discussionmentioning

confidence: 99%

Assimilation of trace elements and carbon by the mussel Mytilus edulis: Effects of food composition

Wang¹,

Fisher²

1996

Limnology & Oceanography

234

190

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Assimilation efficiency (AE) is an important physiological parameter in determining trace element influx from food sources into aquatic animals. We used radiotracer techniques to examine the influence of diet [seven species of algae (two diatoms, two chlorophytes, a prasinophyte, and two dinoflagellates) and glass beads] on the assimilation of seven trace elements (Ag, Am, Cd, Co, Cr, Se, Zn) and C in the mussel Mytilus edulis. Trace element assimilation was related to C assimilation and cytoplasmic distribution in the algae and to gut passage time in the mussels. Mussels displayed different C AEs for the different algal diets; the chlorophytes, which had highly refractory cell walls, were the least digestible food. Assimilation of Cd, Se, and Zn was directly correlated with C assimilation; for Am, Ag, and Cr, no relationship with C assimilation was apparent. For each species except the chlorophytes, AEs of all elements significantly correlated with their cytoplasmic distribution within each algal cell. Among all species, AEs of Am, Co, and Se also increased with elemental penetration into the cytoplasm; however, this relationship was not statistically significant for Ag, Cd, or Zn. With the exception of Cr, AEs of elements increased with gut passage time, implying more efficient digestion-absorption when the element was retained longer in the digestive tract. In waters containing large mussel populations, unassimilated particle-reactive elements should be removed from suspension and enriched in biodeposits in sediments, whereas assimilated metals should be enriched in mussel tissues.For bivalve molluscs, both dissolved and particulate sources can contribute to metal accumulation in tissues. Uptake of metals from the dissolved phase occurs primarily across the gills, after which metals are transported into various organs. Accumulation of metals from particulate sources occurs by ingesting and assimilating metals from particulate sources. Metal influx from particles is a direct function of the assimilation efficiency (AE) of metals, the metal concentration in the ingested particles, and the ingestion activity of the animal (Thomann 198 1;Luoma et al. 1992). Assimilation represents a first-order physiological process that can be compared among different metals, food types, and environmental conditions, and AE can be used to measure metal bioavailability from specific foods.l Corresponding author.

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“…However, Se(O) has only been found associated with microorganisms in the presence of high selenium concentrations (Doran and Alexander 1977). In marine phyto-and zooplankton, selenium is predominantly found in proteins and amino acids; selenium in lipid components is nondetectable (Wrench 1978;Wrench and Campbell 198 1;Foda et al 1983). This particulate selenium is not merely associated with the proteins, but appears to be actually covalently attached to carbon as selenoamino acids and their derivatives (organic selenide forms).…”

Section: Sampling and Methodologymentioning

confidence: 99%

The marine biogeochemistry of selenium: A re‐evaluation1

Cutter

Bruland

1984

Limnology & Oceanography

304

206

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Vertical and horizontal profiles from the North and South Pacific Oceans demonstrate the existence of three species of dissolved selenium: selenite, selenate, and organic selenide (operationally defined). In surface waters, organic selenide makes up about 80% of the total dissolved selenium, selenite concentrations are uniformly low, and selenate concentrations rise with increased vertical mixing. The organic selenide maximum (thought to consist of seleno-amino acids in peptides) coincides with the maxima of primary productivity, pigments, bioluminescence, and dissolved free amino acids. Deep ocean waters are enriched in selenite and selenate, while organic selenide is nondetectable. In suboxic waters of the tropical northeastern Pacific, organic selenide concentrations rise, while selenite values decrease. The downward flux of particulate selenium generally decreases with depth, and fluxing particulate selenium is found to be primarily in the (-2) oxidation state. These data allow a re-evaluation of the internal biogeochemical cycle of selenium. This cycle includes selective uptake, reductive incorporation, particulate transport, a multistep regeneration, and kinetic stabilization of thermodynamically unstable species.

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Selenium metabolism in the Marine phytoplankters Tetraselmis tetrathele and Dunaliella minuta

Cited by 114 publications

References 9 publications

Kinetic determinations of trace element bioaccumulation in the mussel Mytilus edulis

Kinetic determinations of trace element bioaccumulation in the mussel Mytilus edulis

Assimilation of trace elements and carbon by the mussel Mytilus edulis: Effects of food composition

The marine biogeochemistry of selenium: A re‐evaluation1

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