Toxicological response of the green alga<Emphasis Type="Italic">Scenedesmus bijuga</Emphasis> to mercury and lead

Effect of mercury or lead on the growth, bioaccumulation and some enzyme activities of one of the most common algae in River Nile,Scenedesmus bijuga, was determined. The cell count and chlorophylla content decreased with an increase in mercury or lead concentrations in a culture medium, particularly at higher doses. Higher mercury and lead uptake was observed with increasing concentration of the elements. The alga accumulated appreciably more mercury than lead. At higher doses, the two elements strongly suppressed some enzyme activities of primaryS. bijuga metabolism.     

三江平原典型湿地植物中汞的分布与库存量

分析了三江平原典型植物中的总Hg浓度．结果表明,各种植物中总Hg浓度差别较大,苔藓>藻类>苔草>禾草>灌木;干湿环境是影响总Hg浓度的重要因素;湿地植物总Hg浓度高于水稻和玉米等农作物．较高的土壤总Hg浓度是近地面大气中Hg的重要来源,间接地影响到植物中Hg的浓度．植物各构件中总Hg浓度具有立枯>根>叶>茎的特点．在植物整个生长季总Hg浓度先增加后减少．估算了三江平原湿地植物Hg的库存量．小叶章湿地植物地上部分库存量为24．9μg·m^-2;毛果苔草湿地植物地上部分库存量为35．8μg·m^-2,高于加拿大实验湖泊湿地．     

Variability of Mercury Concentrations in Soil and Leaves of Acer plantanoides and Tilia platyphyllos in Poznań City,Poland

The paper presents the results of research on mercury in the soil and leaves of maple (Acer plantanoides) and linden (Tilia platyphyllos) collected in the four districts of the city of Poznań (Poland), which differ in terms of anthropogenic pressure. The average concentration of mercury in soil was 132 μg kg^?1. The highest concentration of mercury was determined in Tilia platyphyllos (233 μg kg^?1), whereas in Acer plantanoides it amounted to 207 μg kg^?1. Based on the study, it was found that the highest concentration of mercury in the investigated leaf species was observed in the samples collected in the districts of Grunwald, Je?yce, and Old Town. The lowest concentration was observed in the samples collected in the district of New Town. The comparison of the obtained results of mercury concentration in soil and leaf samples was made in terms of anthropogenic pressure in the investigated areas and depending on the studied leaf species. Based on the statistical analysis, it was found that there is no statistically significant relationship between mercury concentration in both studied species of trees. There was, however, a relationship between the mercury concentration in leaves and soil.     

Microplate Technique for Determining Accumulation of Metals by Algae

A microplate technique was developed to determine the conditions under which pure cultures of algae removed heavy metals from aqueous solutions. Variables investigated included algal species and strain, culture age (11 and 44 days), metal (mercury, lead, cadmium, and zinc), pH, effects of different buffer solutions, and time of exposure. Plastic, U-bottomed microtiter plates were used in conjunction with heavy metal radionuclides to determine concentration factors for metal-alga combinations. The technique developed was rapid, statistically reliable, and economical of materials and cells. Results (expressed as concentration factors) were in reasonably good agreement with literature values. All species of algae studied removed mercury from solution. Green algae proved better at accumulating cadmium than did blue-green algae. No alga studied removed zinc, perhaps because cells were maintained in the dark during the labeling period. Chlamydomonas sp. proved superior in ability to remove lead from solution.     

Elemental composition of <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis> under conditions of lake nutrient depletion

Electron probe X-ray microanalysis (XRMA) was used to determine the elemental composition of the blue-green alga, Microcystis aeruginosa, in a stratified freshwater lake during the late summer. Colonies of this alga were initially observed in mid-July, at a time when phosphorus concentration in the lake water had decreased to minimal levels (total P 0.04 mg l⁻¹). The P quota of these cells was high (mean concentration 132 mmol kg⁻¹ dry weight) with a cell P to lake water P concentration ratio of 10⁵. The elemental concentrations of Microcystis remained relatively stable throughout the sampling period (July–September), with mean cell concentrations of Mg, P, S and Ca showing no significant changes. Mean elemental ratios and the ratio of monovalent/divalent cations were also relatively constant (SE <10% mean). The pattern of cell elemental associations, determined by Factor and Pearson correlation analysis, was consistent throughout – with Mg, P, K and S forming a core tetrad of inter-correlated elements. The relative constancy of cell composition seen in Microcystis would be expected of an alga with a K-selection strategy. The continued high P quota over a period of nutrient depletion in lake water is consistent with the ability of this alga to sink to nutrient-rich lower regions of the water column.     

Use ofCladophora glomerata to monitor heavy metals in rivers

Methods were developed for the use ofCladophora glomerata to monitor heavy metal concentrations in flowing waters. At least under conditions without marked fluctuations in ambient metal concentration, there was no detectable difference in the metal concentrations of young plants between terminal 2-cm lengths of filament and whole plants. In order to establish the relationship between metal concentration in plant and that in water, 60 algal and water samples were analyzed from sites in northern England for Fe, Cu, Zn, Cd and Pb. Other environmental variables were measured at the time in order to assess their influence on metal accumulation. There were highly significant correlations for each of the five metals between concentrations in alga and water. The regression equations relating metal in alga to metal in water permit an unknown environmental metal concentration to be estimated from the algal concentration. Multiple stepwise regression analyses were used to indicate environmental factors which may influence metal accumulation; for instance, Fe appears to have a positive influence on Cu accumulation. In generalCladophora accumulates much less metal than bryophytes, but the slope relating metal in alga to metal in water is steeper, particularly for Pb. This means thatCladophora is especially useful where there is a need for a sensitive indicator of differences between sites or sampling occasions.     

Mechanism of aluminium tolerance in Cyanidium caldarium

Cyanidium caldarium, an acidophilic, thermophilic red alga, specifically tolerates Al. The tolerance increases at lower culture temperatures. The intracellular Al concentration is kept at low levels, especially when the cells are cultured at lower temperatures. Lower Al incorporation accounts for the Al tolerance in this alga. Fe incorporation antagonizes the Al incorporation, implying that Fe transporters incorporate Al ions. Treatment with an uncoupler, carbonylcyanide m-chlorophenylhydrazone, increases the intracellular concentration of Al. These results support the hypothesis that Al ions taken up by the algal cells are exported by an energy-dependent mechanism.     

Nitrate Uptake by Reef Corals

In specimens of the hermatypic coral species Fungia scutaria and Montipora verrucosa and in the alga Ulva lactuca, nitrate uptake was measured in light and dark with a flow-through apparatus. The nitrate uptake was measurable in high-nitrate bay water of Kaneohe Bay and also in low-nitrate open ocean water. Nitrate consumption rates by the corals and the alga did not differ from light to dark. Neither the coral nor the alga showed measurable immediate nitrate uptake in open ocean water of low nitrate concentration when they had been held previously in the high-nitrate bay water. In low-nitrate open ocean water the uptake per unit time increases when the flow of the water increases. The uptake of nitrate by reef corals even from low concentrations indicates nonspecific nutrient sources for reef corals.     

Mercury ions inhibit photosynthetic electron transport at multiple sites in the cyanobacteriumSynechococcus 6301

Inhibition of electron transport activities in the spheroplasts ofSynechococcus 6301 by HgCl² is dependent on the concentration of mercury ions. The inhibition of whole chain electron transport activity occurs at low concentration of Hg²⁺ (6 ΜM@#@). This inhibition occurs mostly due to interaction of Hg²⁺ on plastocyanin. At an elevated concentration (24 ΜM@#@), mercury induces inhibition chiefly in photosystem II catalyzed electron transport. At this concentration it also alters both the absorption and emission characteristics of the phycocyanin. The photosystem I catalyzed electron transport was inhibited by 50% only at high concentrations (36 ΜM@#@) of HgCl₂. However, electron transport catalyzed by photosystems I and II from reduced duroquinone to methylviologen which involves intersystem electron transport is extremely sensitive to mercury (low concentration 6–9 ΜM) like that of whole chain assay indicating that the observed inhibition in whole chain electron transport at low concentrations is mostly contributed by the damage involving other intersystem electron transport carrier(s) like plastocyanin. Thus mercury ions depending on the concentration affects the electron transport at multiple sites in the spheroplasts ofSynechococcus.     

Effects of salinity on growth and content of intracellular solutes in Heterococcus sp. (Tribonennatales, Xanthophyceae) from Antarctica

The growth and osmoregulation of Heterococcus sp. isolated from dry soil collected in Antarctica were investigated in relation to salinity. This alga was able to grow over a wide range of saline conditions from 0 to 0.8 mol L^-1 NaCI, although growth was suppressed in proportion to the increase in extracellular concentration of NaCI. This indicates that the alga is halotolerant. Using gas-liquid chromatography-mass spectroscopy, it was found to contain mannitol as an osmoticum. The intracellular content of mannitol increased with increase in concentration of extracellular NaCI, suggesting that mannitol acts as an osmoregulatory substance.     

Volatilization of Mercury by Algae

The presence of Chlorella cells in a medium containing HgCl₂ causes a rapid decrease of the mercury content in the algal suspension. The rate of decrease depends on the inoculum concentration. The presence of Hg in the medium induces a lag in the growth, whose length depends on the initial concentration of Hg and of the inoculum. Binding and/or uptake of mercury by the cells is not dependent on temperature. The mercury content per cell declines somewhat at the time at which the culture resumes growth at a rate similar to that of the controls without mercury.     

Seasonal accumulation of metals by red alga Gracilaria verrucosa (Huds.) Papens. from Thermaikos Gulf, Greece

Concentrations of Fe, Pb, Cu, Zn and Cd were determined during one season in the red alga Gracilaria verrucosa, sediment and seawater from the Thermaikos Gulf, Greece. This region has been subject to change due to increases in industrial and domestic activities. The relative abundance of metals in G. verrucosa and seawater decreased in the order: Fe>Zn>Pb>Cu>Cd and in the sediment: Pb>Fe>Zn>Cu>Cd. Cadmium concentration in the alga correlated positively with that in seawater. There was positive correlation between Fe concentrations in the alga and those of the Zn and Cu. The concentrations of metals in the alga showed no significant differences between the stations. Lead, Zn and Cu concentrations in the alga were slightly higher at Biamyl, whereas Cd was higher at Perea and Fe at Nea Krini. Seasonal variation of metal concentrations in the alga was significant for Cd and Fe. Copper and Fe increased from winter to summer, whereas Cd was the opposite. Zinc concentrations were minimum and Pb concentrations were maximum during spring. These variations are discussed in relation to tissue age, life cycle, ambient concentrations of metals and other environmental conditions. Cd and Pb concentrations inG. verrucosa in the Thermaikos Gulf were higher and those of Cu and Zn were lower than in other species of the genus. This revised version was published online in August 2006 with corrections to the Cover Date.     

Identification of Calmodulin in the Red Alga Susabi Laver (Porphyra yezoensis)

To test whether calmodulin is present in the red alga Susabi laver (Porphyra yezoensis), materials was concentrated from this alga, using hydrophobic chromatography. In this case, 0.25 m (NH₄)₂SO₄ should be added to bind the protein to the column in the presence of 5 mm CaCl₂. Calmodulin is present in the marine red alga, although at a very low concentration.     

Flocculation of algae using chitosan

Flocculation of three freshwater algae, Spirulina,Oscillatoria and Chlorella, and onebrackish alga, Synechocystis, using chitosan was studiedinthe pH range 4 to 9, and chlorophyll-a concentrations inthe range 80 to 800 mg m^–3, which produces aturbidity of 10 to 100 nephelometric turbidity units (NTU) in water. Chitosanreduced the algal content effectively by flocculation and settling. Theflocculation efficiency is very sensitive to pH, and reached a maximum at pH7.0for the freshwater species, but lower for the marine species. The optimalchitosan concentration that is required to effect maximum flocculation dependedon the concentration of alga. Flocculation and settling were faster whenconcentrations of chitosan higher than optimal are used. The settled algalcellsare intact and live, but will not be redispersed by mechanical agitation. Thede-algated water may be reused to produce fresh cultures of algae.     

Mercury in the marine food chain in the Southern Ocean at Macquarie Island: an analysis of a top predator,Patagonian toothfish (<Emphasis Type="Italic">Dissostichus eleginoides</Emphasis>) and a mid-trophic species,the warty squid (<Emphasis Type="Italic">Moroteuthis ingens</Emphasis>)

The characteristics and habitat of the Patagonian toothfish (Dissostichus eleginoides) are typical of fish that accumulate high concentrations of mercury. In this study, mercury determinations were made on samples of muscle tissue from Macquarie Island toothfish and the Southern Ocean deepwater warty squid (Moroteuthis ingens). The analysis of mercury in the biological tissues was made by cold vapour-atomic absorption spectrometry following acid digestion. Performance of the analytical procedure was assessed by analysis of certified reference material (DORM-2, dogfish muscle). Mercury concentrations of 16 Macquarie Island toothfish ranged from 0.12 mg kg^–1 (550 g, 381 mm TL) to 0.59 mg kg^–1 (6,100 g, 823 mm TL), with a mean concentration of 0.33±0.12 mg kg^–1. A significant correlation was found between mercury and either toothfish weight or total length. The fish analysed were juveniles, which suggests that larger individuals would have higher mercury concentrations well exceeding food standard code limits for mercury in fish (typically 0.5 mg kg^–1). Warty squid, also from around Macquarie Island, had a low mean mercury concentration of 0.086 mg kg^–1 in mantle tissue; no significant correlation existed between mercury concentration and either squid mantle length or total weight. It is postulated that the squid have a mechanism, possibly involving the digestive gland, that prevents bioaccumulation of mercury in the mantle, and presumably other body tissues.     

EFFECTS OF HYDROXAMATE SIDEROPHORES (STRONG Fe (III) CHELATORS) ON THE GROWTH OF ALGAE1

Varying concentrations of Fe were tested with three hydroxamate siderophores to demonstrate the interactions affecting growth of Chlamydomonas reinhardtii and Chlorella vulgaris. Schizokinen was purified from the excretions of the blue-green alga Anabaena sp. grown in low-Fe medium. Chlamydomonas reinhardtii was inhibited by schizokinen when in molar excess of the Fe concentration; the inhibition was overcome with excess Fe. The growth of C. vulgaris was not affected by this chelator. Results with desferrioxamine were similar. A weaker chelator, rhodorulic acid, did not inhibit the growth of either alga. Low concentrations of the chelators may stimulate algal growth when Fe precipitates are hydrolyzed. Since different algae respond differently to the presence of the chelators, the observed interactions could be important in determining competitive relationships when Fe is limiting. If an alga can excrete a strong chelating agent, as does Anabaena, algae lacking the ability to compete with the chelator may not grow.     

Mercury removal by immobilized algae in batch culture systems

The accumulation and volatilization of mercury by non-immobilized and immobilizedChlorella emersonii have been studied in batch culture systems. Reduction in the mercury concentration in the growth medium by non-immobilized cells was highly dependent on inoculum density, whilst reduction in mercury concentration by immobilized cells was rapid at all inoculum densities. Mercury accumulation by immobilized cell biomass was significantly greater than by non-immobilized cells with 10⁶ and 10⁵ cells bead^–1 or ml^–1. Volatilization of mercury by non-immobilized cell systems was greatest at higher inoculum densities, whereas more mercury was volatilized from immobilized cell systems at lower inoculum densities, and was greatest with unstocked alginate beads. Thus, in immobilized systems, mercury removal from solution is complex and involves mercury accumulation by the cells and volatilization by the matrix and cells. Further studies of mercury accumulation and volatilization by unstocked immobilization matrices revealed that agarose volatilized much less mercury than alginate or agar. The precise mechanism of mercury volatilization by alginate remains unclear, though it is thought to be a chemical effect.     

Accumulation of Ag, Cd, Co, Cu, Hg, Ni and Pb in Pavlova viridis Tseng (Haptophyceae)

The flagellate alga Pavlova viridis Tseng was investigated in the laboratory for accumulation of the heavy metals, silver, cadmium, cobalt, copper, mercury, nickel and lead. The cultures were grown in an artificial seawater medium mixed with the individual metals at different concentrations. Based on data from the controls, the baseline metal concentrations in P. viridis were shown to be in an order of Cu > Pb > Co > Cd > Ni > Ag > Hg. In the experimental groups, the seven metals displayed different isotherm equilibrium patterns and the metal uptake capacity of the alga was Ni > Pb > Co > Hg > Cu > Cd > Ag at equilibrium. When assessed using the bioconcentration factors, metal accumulation by P. viridis was demonstrated to be the most efficient at a concentration of 0.001 mg L-1 for Ag, Cd and Co, and at 0.01 mg L-1 for Cu, Hg, Ni and Pb. This study suggests that P. viridis can be a source of mineral supplements in mariculture. The alga is not, however, recognized as an effective agent for removing heavy metals from wastewater. This revised version was published online in June 2006 with corrections to the Cover Date.     

The hydrochemical regime of the habitat of the red algaAhnfeltia tobuchiensis population in the Bay of Izmena (Kunashir Island)

In 1989–1990 and 1997, in the Bay of Izmena (Kunashir Island), the spatial distribution ofAhnfeltia tobuchiensis (Kanno et Matsubara) Mak, an unattached agar-containing red alga, was studied, and the availability of biogenic elements for the process ofA. tobuchiensis primary production was assessed. The concentrations of dissolved O₂, ammonium [NH ₄ ⁺ ], and orthophosphate [PO ₄ ³⁻ ], were highest in the central and northeastern areas of the bay, where the bulk of the population is situated. During the day, the mean oxygen concentration above the alga bed increased from 8.2±0.09 to 8.7±0.08 mg/l, showing a high rate of photosynthesis in the population. As a result of diurnal ammonium and orthophosphate assimilation by the alga, their concentration in bottom waters dropped from 5.1 to 3.5 and from 0.45 to 0.35 μM/l, respectively. Proceeding from the mean values of the nitrogen to phosphorus atomic ratio in the bay waters (11.5±3.3 in the morning and 10.6±3.3 in the evening) and in algal thalluses (33 in the case ofA. tobuchiensis), we conclude that the concentration of major biogenic elements is sufficient for the processes of primary production in the Bay of Izmena.     

Alteration in growth and peroxidase activity by heavy metals in Phaseolus seedlings

The aim of the present work was to see the effect of mercury and chromium on elongation growth of phaseolus seedlings and changes in chlorophyll content. Phaseolus seedlings were treated with two different concentrations of two heavy metals viz. mercury (0.05 mM and 0.4 mM HgCl₂, and chromium (0.5 mM and 1.0 mM K₂Cr₂O₇). Both mercury and chromium inhibited root and hypocotyl elongation growth. Changes in cytoplasmic and wall bound peroxidase activities were studied using guaiacol as a hydrogen donor. Peroxidase activity was higher in both mercury and chromium treated seedlings as compared to distilled water control; they showed a clear concentration effect. Peroxidase activity showed inverse relation with growth i.e. distilled water treated seedlings had maximum growth and minimum activity while higher concentration of heavy metal treated seedlings had minimum growth and maximum activity. Chlorophyll content was also decreased by mercury. The role of peroxidase activity in defense mechanism in response to heavy metal toxicity is discussed.