Cadmium and manganese flux in eelgrass Zostera marina II. Metal uptake by leaf and root-rhizome tissues

Cadmium and manganese radionuclide uptake by Zostera marina L. tissues and translocation between rootrhizomes and leaves was examined. Cadmium concentrations in root-rhizomes increased with incubation time but appeared to reach saturation levels at 24 h of exposure. Translocation of cadmium between root-rhizomes and leaves occurred in both directions. A greater flux of cadmium downward suggested that root-rhizomes were a cadmium sink. Cadmium flux in either direction could be enhanced by a salt gradient. Cadmium appears to move through eelgrass by diffusion or mass flow through vascular tissues and apparent free spaces. Manganese is less mobile but is more readily fixed by leaves. Manganese mobility is not enhanced by salt gradients. Incorporation of cadmium and manganese into root-rhizomes from labelled anoxic sediments was several orders of magnitude less than that from labelled anoxic seawater media.This research was supported by grants to B. H. Brinkhuis from the New York Sea Grant Institute and the Nassau-Suffolk Regional Planning Board, and by a Jessie Smith-Noyes Fellowship and Sigma Xi grant to W. F. PenelloMarine Research Center Contribution No. 248     

The nitrogen supply to intertidal eelgrass (Zostera marina)

The uptake of ammonium and nitrate by eelgrass (Zostera marina L.) was studied in two-compartment chambers. The plants were collected in 1992 from a population growing on a tidal flat in the S.W. Netherlands. They were incubated under conditions which reflected field conditions; this implied the use of natural seawater and sediment porewater as incubation media. In all six experiments, carried out over the course of a major part of the growing period (from July to the end of September), ammonium appeared to be much more important as a source of nitrogen than nitrate. The largest part was taken up by the leaves: uptake of ammonium by the leaves accounted for 68 to 92% of total plant nitrogen uptake. The uptake of nitrogen compounds by the root-rhizome system represented only 4 to 30% of total plant uptake. Thus, at least during flood tide, the leaves play the major role in nitrogen uptake in this intertidal population. During ebb tide, most of the plants are submerged in very shallow tidepools. It is suggested that during this phase of the tidal cycle, influx of porewater ammonium into the tide-pool water may enable the leaves to exploit local sediment resources.     

Uptake of cadmium by the eelgrassZostera marina

The uptake of cadmium by the shoots ofZostera marina L. (eelgrass) was examined in the laboratory. Experiments were carried out in experimental chambers which allowed the separation of the leaves from the root-rhizome portions of intact shoots. Cadmium uptake by the root-rhizome portions over 24 h was directly related to substrate cadmium concentration (1.0, 5.0 and 10.0 g Cd ml^-1) and varied from 6.5 to 30.0 g Cd g^-1. Cadmium uptake by the root-rhizomes and the leaves in a substrate concentration of 1 g Cd ml^-1 was also related to exposure times (24, 48 and 72 h). Maximum uptake by the root-rhizomes and the leaves was observed after 72 h at a substrate concentration of 1 g Cd ml^-1 and was equivalent to 48 and 94 g Cd g^-1, respectively. Translocation of cadmium from the leaves to the root-rhizomes was observed after 24 h, and at the end of 72 h was equivalent to 27% of the total leaf uptake. No cadmium movement from the root-rhizomes to the leaves was detected.     

Interaction of leaves and roots of Ruppia maritima in the uptake of phosphate,ammonia and nitrate

Leafy shoots of Ruppia maritima were incubated in two-compartment chambers, with the roots in one compartment and the leaves in the other. Rates of phosphate and ammonia uptake were compared when roots and leaves were supplied with these nutrients separately and simultaneously. Uptake of phosphate and ammonia by leaves was reduced when these nutrients were supplied to the roots, but uptake by roots was not affected by the availability of these nutrients to leaves. This response suggested root-to-shoot translocation predominated. V_max for leaf uptake of phosphate was decreased by 31% when roots were supplied with phosphate simultaneously. Leaf uptake of ammonia was not affected by the availability of ammonia to roots unless the plants were starved for nitrogen. V_max for plants starved for nitrogen was two times greater than for unstarved plants. When roots and leaves of starved plants were exposed simultaneously to ammonia, V_max for ammonia uptake by leaves did not change but K_s increased by 97% to a value similar to that for unstarved plants. Ammonia supplied to leaves or roots inhibited nitrate uptake by leaves by an average of 52%. Ammonia supplied to leaves, however, had no influence on the rate of nitrate uptake by roots.Contribution No. 579 of the Environmental Research Laboratory, US Environmental Protection Agency. Use of product names does not imply endorsement by USEPA     

Cadmium and manganese flux in eelgrass Zostera marina I. Modelling dynamics of metal release from labelled tissues

Release of cadmium and manganese radionuclides from eelgrass leaves and root-rhizomes into seawater and seawater plus 1×10^-4 disodium ethylenediaminetetraacetate (EDTA) was monitored over periods of 6 h following incubations of 1 to 98 h. Flux of both isotopes from tissues is initially rapid and enhanced by the addition of EDTA. The initial release rate is independent of incubation time, indicating desorption of metals from exterior tissue surfaces. High initial release rates become rapidly attenuated. Fitting a power curve to the data proved valuable in inferring uptake capacity of tissues from observed metal release characteristics. In addition to desorption, and diffusion from intercellular spaces, diffusion from cells and biologically controlled release could be described with the aid of curve fits. Manganese apparently is released more slowly during later phases of release than is cadmium, pointing to greater biological accumulation potential.This research was supported by grants to B. H. Brinkhuis from the New York Sea Grand Institute and the Nassau-Suffolk Regional Planning Board, and by a Jessie Smith-Noyes Fellowship and Sigma Xi grant to W. F. PenelloMarine Sciences Research Center Contribution No. 247     

Short-term influence of nutrient availability on the uptake and translocation of phenanthrene in mangrove seedlings

Abstract

The uptake and distribution of phenanthrene, a typical polycyclic aromatic hydrocarbon, in plant tissues of Aegiceras corniculatum and Avicennia marina and the relationship with nutrient (nitrate, ammonium, and soluble reactive phosphorus) availability were investigated. After 12?h of exposure, enhancements in the concentration of nitrate and soluble reactive phosphorus markedly decreased the residual level of phenanthrene in roots, while the addition of ammonium significantly increased the residual concentration. Due to the similar enzymatic degradation potential between treatment groups, the variation of phenanthrene concentration in mangrove roots may result from the H⁺/phenanthrene cotransport at the root surface that was influenced by nutrient uptake. Moreover, both nitrate and soluble reactive phosphorus amendments significantly increased translocation of phenanthrene from roots to leaves, which likely resulted from the change of hydraulic conductivity in mangrove plants triggered by different nutrient availability.     

接种Glomus versiforme对红三叶草利用有机磷的影响

以红三叶草为材料,利用三室隔网培养方法,研究接种菌根真菌Glmous versiforme对土壤有机磷及外加有机磷化合物植酸钠（Na-Phytate)、核糖核酸（RNA）和卵磷脂（Lecithin)的利用效率,植株生长7wk后收获测定植标干物重、含磷量和根系菌根侵染率,结果表明：接种菌根真菌能明显增加植株干物重、含磷量和吸磷总量,与各有机磷处理相比,无机磷（KH2PO4）处理生长效应最好,施用有机磷化合物各处理与CK相比均明显促进了植株生长,但不同有机磷处理之间没有显著差异,在植株吸磷量上,各接种处理均为相应CK处理的2倍以上,其中磷酸二氢钾处理吸磷量最高,菌根对照植物的根外菌丝虽然被限制在有限的空间内,但其吸磷量也达到不施磷的CK－M处理的2倍多,这说明由于菌根的形成植物能利用土壤因有的有机磷来满足自身生长的需要,表3参10     

Phytotoxicity and uptake of chlorpyrifos in cabbage

Chinese cabbage, Brassica chinensis L., and cabbage, Brassica oleracea L. var. capitata, are the main daily foliar vegetables of the vast majority of the population of eastern and southern China. Cabbages are also planted and consumed widely in other countries. The insecticide and acaricide chlorpyrifos is registered in many countries. Chlorpyrifos controls a variety of insects in plants and soils, and chlorpyrifos is extensively used in the Chinese market. Food poisoning due to the presence of organophosphorus pesticide residues in vegetables has been reported in China provinces. Plant uptake of pesticide residues in air, water, and soil is a source of pesticide residues in vegetables. Here, phytotoxicity and uptake of chlorpyrifos by Chinese cabbage and cabbage were studied in the laboratory using the batch technique. From 0 to 16 days after chlorpyrifos treatment, vegetables roots, stems, leaves, and culture water samples were collected, and the residues of chlorpyrifos in culture water, plant tissues were analyzed using GC-FPD. The results demonstrate that culture solutions with chlorpyrifos had no significant inhibitory effects on vegetable plant height. However, at 1.0 mg/l, it had significant inhibitory effects on the root length and fresh weight of Chinese cabbage. Then, at 10.0 mg/l, it had only significant inhibitory effects on the root length and fresh weight of cabbage compared to the control treatment. The disappearance rates of chlorpyrifos in solutions were in sequence as: nutrition solution with Chinese cabbage, nutrition solution with cabbage, pond water, nutrition solution. The results showed also that chlorpyrifos can be taken up by roots of Chinese cabbage and cabbage from water and subsequently translocated as a function of time. Uptake dynamics of chlorpyrifos from culture solutions by the two cabbage plants were similar.     

小麦根系菲与磷吸收及转运的相互作用

作物根系对多环芳烃(PAHs)与磷吸收及转运之间的相互作用研究对农产品的安全生产和PAHs污染环境植物修复的强化具有重要意义。为此,本文以菲为PAHs的代表,采用水培试验研究了不同磷、菲水平下小麦根系菲、磷吸收及其转运的效果,旨在揭示植物根系吸收PAHs与磷素的相互作用。结果表明,在0~1 200μmol·L~(-1)磷浓度范围内,小麦根系、茎叶菲含量在低磷浓度(10μmol·L~(-1))时最高,分别为36.87 mg·kg~(-1)和2.07 mg·kg~(-1);磷含量总体呈现随磷处理浓度的升高而增大的趋势;成对数据t-检验显示无论加菲与否,根系、茎叶磷含量无显著性差异(P0.05)。磷可促进菲从根部向地上部转运,而菲对磷转运没有显著性影响。在低磷浓度下(10μmol·L~(-1)),随着菲浓度的升高,小麦根系、茎叶菲含量呈现显著升高趋势(P0.05)。磷、菲共存处理介质pH升高幅度大于单一处理。     

根表铁膜对水稻吸收转运稀土元素Ce的影响

采用溶液培养的方法探讨根表铁膜形成对水稻吸收积累和转运稀土元素Ce的影响。结果表明,Ce污染胁迫可抑制水稻根表铁膜的形成,根表铁膜吸附的Ce量随着溶液中Ce浓度的提高而增加。根表铁膜形成可降低水稻根系但提高水稻茎叶对Ce的吸收积累。当溶液中Ce浓度为0.1、0.5和1.0 mmol·L~(-1)时,铁膜诱导组水稻根系Ce含量分别比非诱导组水稻根系Ce含量降低38.60%、45.94%和32.75%,诱导组水稻茎叶Ce含量分别比非诱导组水稻茎叶Ce含量提高42.37%、28.87%和22.62%。根表铁膜形成可影响Ce在水稻植株中的富集和转运能力。非诱导组水稻根系富集Ce的能力远大于茎叶。诱导组水稻根系对Ce的富集能力最强,其次是根表铁膜,最后是水稻茎叶。诱导组水稻根系Ce转运系数显著大于非诱导组的根系,说明根表铁膜形成可促进水稻根部Ce向茎叶中转运。可见,根表铁膜对水稻吸收转运稀土元素的影响机理比较复杂。     

Growth responses of the newly-discovered Cd-hyperaccumulator Rorippa globosa and its accumulation characteristics of Cd and As under joint stress of Cd and As

Rorippa globosa has been identified as a newly-found Cd-hyperaccumulating species. In the present study, growth responses of Rorippa globosa and its accumulation characteristics of Cd and As were examined under joint stress of Cd and As. The results showed that Cd and As had an antagonistic effect on enhancing the growth of Rorippa globosa plants and Cd uptake and accumulation under the low concentration Cd and As treatments. When the concentration of Cd in the soil was 10 mg/kg and the concentration of As was 50 mg/kg, the highest growing height of the plant was up to 35.9 cm and the dry weight of the shoots was up to 2.2 g/pot, respectively. Meanwhile, the accumulation of Cd in the leaves under the joint stress was higher than that at the same level under single Cd pollution. However, there were synergic adverse effects on plant growth and Cd uptake under the combined pollution from a high concentration of Cd and As. Meanwhile, the accumulation of As in the roots was greater than that in the shoots, the translocation factor (TF) was ?0.3 and the bioaccumulation factor (BF) was ?0.6, thus showing that Rorippa globosa had an excluding effect on As uptake. These results confirmed that Rorippa globosa had a strong tolerant ability to the joint stress of Cd and As, and the potential for phytoremediation of soils contaminated by Cd and As.     

不同磷浓度下水稻短根突变体与野生型对五价砷吸收和转运的差异

为研究水稻根形态及磷营养状况对水稻吸收和转运五价砷的调控作用,采用水培的方法,研究了在不同外部磷浓度(0、10、50、150、300μM KH2PO4)下水稻(Oryza sativa L.)短根突变体与野生型短期内对五价砷(10μM Na3AsO4)吸收和转运的差异.结果表明,水稻根形态(短根突变体与野生型)和磷营养状况均能对水稻吸收和转运五价砷产生显著影响:1)磷能竞争性抑制水稻对五价砷的吸收,随营养液中磷浓度的增加,水稻地上部和地下部五价砷含量、单位根干重砷吸收量(根系砷吸收能力)均显著降低;2)水稻短根突变体对五价砷的吸收能力低于野生型,但转运能力高于野生型.     

几种改性磷肥肥效研究初报

在与过磷酸钙生产类似的亚艺条件下,在磷矿粉中加入一定比例的添加剂,研制出3种改性磷肥。化学分析结果表明,在改性磷肥有效磷中,水溶性磷比例下降。盆栽试验结果显示,在等质量施肥条件下,3种改性磷肥均有较大幅度的增产,且植株吸磷量和磷含量有显著的增加。     

Control of microbial growth and of amphipod grazing by water-soluble compounds from leaves of Zostera marina

The role of minor components of the leaves of Zostera marina L. in altering the activity of micro-organisms directly (and indirectly by affecting amphipod grazers) was investigated in laboratory experiments, using plants collected at Roberts Bank (49°2N; 123°8W) on the west coast of Canada. Water-soluble extracts of eelgrass leaves inhibited the growth of a micro-alga (Platymonas sp.) and many marine bacteria at concentrations equivalent to as little as 10 mg dry leaf l^-1. The potency of leaf extracts was higher (1) in young, actively metabolizing tissue than in older leaves, and (2) in leaves collected during rapid growth in summer 1980 than during the following winter. Water-soluble inhibitors (especially phenolic acids) may explain the low biomass of epiphytes on actively growing leaves. Three phenolic acids inhibited the test micro-organisms at concentrations as low as 0.3 mg l^-1; caffeic acid was more potent than either protocatechuic or gentisic acid. Extracts of young leaves also inhibited grazing by amphipods [Eogammarus confervicolus (Stimpson)] on dead leaves. The time required for leaching of soluble inhibitors may account for the delay between the loss of leaves from the plants and the onset of grazing. Thus, interactions among the biotic components of the detritus ecosystem may be significantly modified by minor compounds in the leaves of Z. marina     

不同磷初始浓度对紫萍生长及磷吸收效率的影响

采用室内模拟培养试验方法,研究不同磷初始浓度对紫萍生长及磷吸收效率的影响。结果表明,水体初始ρ（磷）为3.0 mg.L-1时,紫萍相对生长率最高,生长繁殖速度最快。当初始ρ（磷）为0.3～3.0 mg.L-1时,紫萍对水体中磷的去除率在70%以上。紫萍累积吸磷量和磷吸收能力均随磷初始浓度的升高而增加,但当初始ρ（磷）为45.0 mg.L-1时,紫萍累积吸磷量和单位鲜质量紫萍吸磷量均明显下降。当初始ρ（磷）≤1.5 mg.L-1时,紫萍体内酸性磷酸酶活性升高,但随着低磷胁迫时间的延长,低磷条件和高磷条件间酸性磷酸酶活性差异减小。     

Increased macrophyte nitrate reductase activity as a consequence of groundwater input of nitrate through sandy beaches

While most marine macrophytes preferentially assimilate ammonium to meet growth demand for nitrogen, some also utilize nitrate and exhibit high nitrate reductase activity (NRA). Although nitrate concentrations are often low in coastal waters during the summer and sandy beaches are generally considered to be low nutrient-input habitats, we have observed elevated NRA in leaves of some eelgrass (Zostera marina L.) plants growing immediately adjacent to the shoreline. We postulated that nitrate may become available to eelgrass and macroalgae via groundwater inputs that enter the nearshore water column. To address this possibility, we investigated the availability of groundwater nitrate for the induction of NRA in the leaves of eelgrass and in the macroalgaeSargassum filipendula C. Agardh (Phaeophyceae) andEnteromorpha intestinalis L. Link (Chlorophyceae) collected adjacent to two sandy beaches in the vicinity of Woods Hole, Massachusetts, USA. Induction of NRA was determined in the laboratory for eelgrass collected from one of the beach sites and from an offshore site, Lackey's Bay, which is isolated from groundwater input. At the two beach locations, pore water nitrate concentrations were 100 to 400µM within a few meters inland from the waterline. Nitrate efflux into the nearshore water column was quite high and variable (2160±660µmol m^–2 h^–1) when associated with rapid percolation (37±11 1 m^–2 h^–1) of nitrate-enriched pore water. Turbulent wave mixing rapidly diluted the nitrate. Macroalgae and eelgrass growing adjacent to a beach with high nitrate efflux had NR activities three- to sevenfold higher than those of algae and eelgrass growing along a beach section with low nitrate efflux. NRA of eelgrass plants from Lackey's Bay and Great Harbor increased in response to low daily nitrate additions (10 to 25µM) in the laboratory, with higher nitrate additions (50 to 200µM) yielding less dramatic responses. The increase in NRA was roughly three times higher for Great Harbor than for Lackey's Bay eelgrass. It appears that groundwater input of nitrate is sufficient to induce NRA in marine macrophytes growing near some beaches, including those with turbulent wave mixing.     

Der Einfluß physikalischer und chemischer Faktoren auf die Aufnahme in Meerwasser gelöster Aminosäuren durch Aktinien

Changes in abiotic environmental factors do not adversely influence the capacity of Anemonia sulcata (Coelenterata, Anthozoa) to take up dissolved amino acids from sea water; e. g., A. sulcata resorbs also under anaerobic conditions. The influence of temperature on amino acid uptake (Q₁₀=2) indicates that the translocation of the organic molecules through membranes of the ectoderm depends on energy. Uptake of amino acids is possible against a gradient of up to 9×10⁶:1. It can be postulated that L-amino acids (also D-isomers) and glucose are resorbed by different “carrier systems”, since glucose does not influence the uptake of amino acids; however, amino acids can interfere with each other, e. g. phenylalanine/glycine. Blocking of anaerobic glycolysis results in uptake reduction; at the same concentrations “oxidative” blockers have a much smaller effect on amino acid uptake. The possibility of exploiting the surrounding water as an energy source by taking up dissolved organic material is discussed with reference to ecological and evolutionary aspects.     

Interactions between two introduced species: Zostera japonica (dwarf eelgrass) facilitates itself and reduces condition of Ruditapes philippinarum (Manila clam) on intertidal flats

Dwarf eelgrass (duckgrass; Zostera japonica) and Manila clams (Ruditapes philippinarum) are two introduced species that co-occur on intertidal flats of the northeast Pacific. Through factorial manipulation of clam (0, 62.5, 125 clams m⁻²) and eelgrass density (present, removed by hand, harrowed), we examined intra- and interspecific effects on performance, as well as modification of the physical environment. The presence of eelgrass reduced water flow by up to 40% and was also observed to retain water at low tide, which may ameliorate desiccation and explain why eelgrass grew faster in the presence of conspecifics (positive feedback). Although shell growth of small (20–50 mm) clams was not consistently affected by either treatment in this 2-month experiment, clam condition improved when eelgrass was removed. Reciprocally, clams at aquaculture densities had no effect on eelgrass growth, clam growth and condition, or porewater nutrients. Overall, only Z. japonica demonstrated strong population-level interactions. Interspecific results support an emerging paradigm that invasive marine ecosystem engineers often negatively affect infauna. Positive feedbacks for Z. japonica may characterize its intraspecific effects particularly at the stressful intertidal elevation of this study (+1 m above mean lower low water).     

Simulation of long-term nutrient removal in a full-scale closed-loop bioreactor for sewage treatment: an example of Bayesian inference

In this study, the performance of nitrogen and phosphorus removal in a full-scale closed-loop bioreactor (oxidation ditch) system was simulated using the ASM2d model. Routine data describing the process for two years were compiled for calibration and validation. To overcome the identifiability problem, the classic Bayesian inference approach was utilized for parameter estimation. The calibrated model could describe the long-term trend of nutrient removal and short-term variations of the process performance, showing that the Bayesian method was a reliable and useful tool for the parameter estimation of the activated sludge models. The anoxic phosphate uptake by polyphosphate accumulating organisms (PAO) contributed 71.2% of the total Poly-P storage, which reveals the dominance of denitrifying phosphorus removal process under the oxygen limiting conditions. It was found that 58.7% of the anoxic Poly-P storage and denitrification by PAO in the reactor was achieved in the aerated compartment, implying that the PAO’s anoxic activity was significantly stimulated by the low dissolved oxygen (DO) level in this compartment due to the oxygen gradient caused by brush aerator.     

Population structure of the Spanish sardine Sardinella aurita: natural morphological variation in a genetically homogeneous population

The importance of larval dispersal in determining the distribution and abundance of benthic marine organisms is well recognized; however, the contribution of post-larval dispersal has not been measured. I compared the dispersal of swimming larvae with that of rafting colonies in a population of compound ascidians, Botrylloides sp., living attached to leaves of the eelgrass Zostera marina in Tomales Bay, California, USA in 1990–1992. Colonies rafting on broken eelgrass traveled over 200 times farther and had comparable recruitment success relative to swimming larvae. The recruitment of rafting colonies into new habitats was facilitated by the ability of thesecolonial animals to grow asexually onto surrounding substrata. Rafting colonies brooded larvae that were subsequently relased after the colony settled into a new habitat. These results suggest that colonization of new habitats can occur by post-larvae as well as larvae, and that long-range dispersal by species with short-lived larvae may occur by post-larval rafting.