Joseph W. Rachlin

Uptake of heavy metals by Plectonema boryanum (cyanophyceae) into cellular components, especially polyphosphate bodies: An X-ray energy dispersive study

Abstract In situ X-ray energty dispersive analysis has been used to study heavy metal uptake in Plectonema boryanum . Air-dried cells observed in the STEM mode of the SEM show numerous polyphosphate bodies in the cells. By using this system as a probe to analyse cell sectors it was determined that the heavy metals Cd, Co, Cu, Hg, Ni, Pb and Zn are all taken up and sequestered in the cell sectors with polyphosphate bodies. Smaller amounts of the metals Cd, Cu, Hg, Pb and Zn are also concentrated in the cell sectors without polyphosphate bodies. Control polyphosphate bodies cell sectors generate high P and K signals and a low Mg signal. Sometimes a Ca peak is also generated. In Cd-exposed cells the K and Mg signal is lost from the polyphosphate body cell sectors. In Cu-treated cells the Mg and K peaks are lost from the polyphosphate body cell sectors. In Pb-treated cells the K signal is reduced from both the bodies and the cell sectors without bodies. In Hg-treated cells the K signal is lost and the Ca signal is enhanced. The other metals did not significantly affect the elemental peaks generated in the polyphosphate body cell sectors or the cell sectors without polyphosphate bodies. The sequestering of heavy metals in the polyphosphate bodies is suggested as serving a dual purpose in cells by providing a storage site for essential metals and acting as a detoxification mechanism.

Utilization of morphometric analysis in evaluating response ofPlectonema boryanum (Cyanophyceae) to exposure to eight heavy metals

The techniques of morphometric analysis were used to study the ultrastructural changes induced inPlectonema boryanum (Cyanophyceae) by heavy metal exposure. Four of the test metals (Mn, Zn, Hg, and Cd) produced no changes in overall cell dimensions. Two metals (Pb and Cu) produced significant increases in cell size and two other metals (Co and Ni) caused significant decrease in cell size. Mn, Pb, Co, Ni, and Cd caused significant increases in the surface area of the cells thylakoids and Ni, Co, Zn, and Hg caused a significant reduction in the volume of the intrathylakoidal spaces. All tested metals except Pb and Mn caused the production of extra intracellular membrane whorls. Pb, Mn, Co, Zn, Hg, Cd, and Ni caused coalescence of cellular lipid while Cu caused a reduction in cellular lipid content. Co caused a reduction in the number of polyhedral bodies and Cd caused an increase in the volume of the cells polyphosphate bodies. The physiological significance of these findings are discussed in terms of potential toxic action of cations and the cellular mechanisms for the detoxification of cations once they enter the cell. Common mechanisms of both procaryotic and eucaryotic algae are discussed and the utilization of stereological techniques for electron microscopic morphometric analysis is established in studies of metal toxicity at the cellular level.

The toxicological response of the algaAnabaena flos- aquae (cyanophyceae) to cadmium

The toxicological response of the cyanophycean algaAnabaena flos- aquae to cadmium was investigated by three integrated approaches: 1) the determination of the incipient lethal concentration of the metal, 2) study of metal incorporation and cellular compartmentalization using X-ray energy dispersive analysis, and 3) the quantification of intracellular structural changes, after metal exposure, using morphometric analysis. After 96 hr of exposure, the incipient lethal concentration was calculated to be 0.118 ± 0.04 μM cadmium. At concentrations three orders of magnitude higher than the incipient lethal concentration, cadmium was incorporated into both the cellular cytoplasm and the cells polyphosphate bodies. Cadmium also caused the polyphosphate bodies to lose Mg and Ca, resulting in ionic changes in the elemental composition of these cellular inclusions. The utilization of stereological techniques for electron microscopic morphometric analysis established that all concentrations of cadmium tested caused significant reductions in the surface area of the cells thylakoids. Cadmium induced changes in the numbers and relative volume of the cell occupied by polyhedral bodies, polyphosphate bodies, lipid inclusions, cyanophycin granules, membrane limited crystalline, inclusions, and changes in the volume of the cell wall layers were also documented. The physiological significance of these findings are discussed in terms of the toxic action of cadmium and the cellular mechanisms for detoxification of cations once they enter the cell.

An x-ray energy dispersive study of cellular compartmentalization of lead and zinc in Chlorella Saccharophila (Chlorophyta), Navicula incerta and Nitzschia closterium (bacillariophyta)

Abstract The compartmentalization of the heavy metals Pb and Zn was studied in Chlorella saccharophila, Navicula incerta and Nitzschia closterium using the STEM with dispersive X-ray spectrometer. Cells were exposed to the metals, at various concentrations, for 96 hr and then air dried on formvar coated grids. Lead was found to be concentrated in cell sectors with polyphosphate bodies in C. saccharophila at 13.3 ppm and in N. incerta and N. closterium at 10 ppm. Lead was also detected when the probe was placed on the cell margin (cell wall sector) of C. saccharophila at 25 ppm and 5.6 ppm in N. closterium . No Pb was detected in the cell margin sector (cell wall) of N. incerta at metal concentrations up to 10 ppm. In cells exposed to Zn, the metal was detected in polyphosphate body cell sectors in C. saccharophila starting at 1.0 ppm and in N. incerta starting at 2.3 ppm. Small amounts of Zn were detected in cell sectors away from polyphosphate bodies in C. saccharophila starting at 2.3 ppm. No Zn was detected in N. closterium at metal concentrations up to 2.3 ppm. It is suggested that the compartmentalization of the heavy metals Pb and Zn into polyphosphate bodies and the cell wall may be a means by which some algae reduce the toxicity of these cations. These means of sequestering heavy metals may also be a significant way in which heavy metals move, in large amounts, in the food chain.

The toxic action and interactions of copper and cadmium to the marine AlgaDunaliella minuta, in both acute and chronic exposure

The effective concentrations of copper and cadmium which reduced the population growth ofDunaliella minuta by 50% after 96 h of static exposure, were determined to be 7.57 μM Cu and 0.34 μM Cd. Short-term static exposure to both metals indicated that their combined action is antagonistic with respect to growth of this chlorophyte. Additionally, long-term exposure to low levels of Cu or Cd led to the acquisition of tolerance towards Cu and Cd, respectively, and co-tolerance towards Cu.

The growth response of the green alga Chlorella vulgaris to combined divalent cation exposure

Using the growth response of the green algaChlorella vulgaris as a model system, the effects of combinations of the environmentally active cations Cd, Co, and Cu were evaluated. The 96-h static EC50 for these cations toC. vulgaris were, respectively, 0.89 μM, 9.0 μM, and 2.8 μM, yielding a toxicity series such that Cd>Cu>Co. The cation combinations of Cd+Cu, and Cu+Co acted synergistically, while Cd + Co, and the tri-metallic combination Cd + Cu + Co resulted in antagonistic interactions. Examination of these toxic combinations at 24, 48, 72, and 96 h indicate that the cellular response is not a uniform one. Failure of energy dispersive X-ray spectrophotometric analysis to demonstrate any intracellular incorporation of these cations (except for a weak cytoplasmic Cu peak at the 8.0 KEV position) suggests that the toxic actions of these cations at EC50 concentrations are exerted at the level of the plasma membrane.

Food Habits of Atlantic Sturgeon off the Central New Jersey Coast

Abstract Limited information exists on the marine diet of the Atlantic sturgeon Acipenser oxyrinchus oxyrinchus. We examined the food habits of 275 Atlantic sturgeon (total length, 106–203 cm) caught in the commercial fishery off the coast of New Jersey. Stomachs were provided by fishermen. Significantly more stomachs were empty in the spring than in the fall. Sand and organic debris were a major component in the stomachs (26.3–75.4% by weight). Polycheates were the primary prey group consumed, although the isopod Politolana concharum was the most important individual prey eaten. Mollusks and fish contributed little to the diet. Some prey taxa (i.e., polychaetes, isopods, amphipods) exhibited seasonal variation in importance in the diet of Atlantic sturgeon. Identification of the offshore diet of Atlantic sturgeon is an important step in developing a better understanding of the life history requirements and marine ecology of this species.

Ultrastructural changes in Dunaliella minuta following acute and chronic exposure to copper and cadmium

The ultrastructural changes taking place after shortterm acute exposure to copper, cadmium and a combination of the two metals were examined. Additionally, the effects of long-term (8 months) exposure to ambient concentrations of these metals were investigated. Exposure to 0.34 μM cadmium affected the photosynthetic potential of this alga, by reducing the relative volume of the chloroplast by 23.27%. It also led to 74.6% increase in the relative volume of starch granules. Cells challenged with 0.34 μM cadmium and 7.57 μM copper had 33.49% larger volumes than controls, and their relative lipid volumes increased by 170%. In contrast, the relative volume of their pyrenoids decreased by 41.46%. Similar results were obtained after chronic exposure to 4.9×10−4 μM copper with the relative volume of the pyrenoid being 28% smaller than the controls.

The effects of pH on the growth ofChlorella vulgaris and its interactions with cadmium toxicity

The effects of pH alone, and in combination with exposure to 0.89 μM cadmium, on the growth response of the green algaChlorella vulgaris were evaluated. Acidic (3.0–6.2) and alkaline (8.3–9.0) pH values retarded the growth of this alga. Optimal growth occurred when the pH of the medium was adjusted to values of 7.5 and 8.0. When the cells were exposed to pH adjusted medium plus the presence of 0.89 μM Cd, a value known to reduce population growth by 50% at the control pH of 6.9, the affects were additive at the acidic (3.0–5.0) pH ranges. At alkaline pH values of 8.3–9.0 all toxicity responses could be explained by pH adjustment alone, indicating that additional cadmium toxicity was absent. At pH values of 7.5 and 8.0, cadmium toxicity was mitigated against, and resultant growth at pH 8.0 was at the same enhanced rate as this pH without cadmium.

A morphometric and x-ray energy dispersive approach to monitoring pH-altered cadmium toxicity inAnabaena flos-aquae

Cadmium toxicity and uptake as influenced by different pH values have been studied in the freshwater cyanobacteriumAnabaena flos-aquae, using the techniques of morphometric analysis, x-ray energy dispersive analysis and atomic absorption spectrophotometry. A general reduction in cell dimension, thylakoid surface area, number and volume of polyhedral bodies, polyphosphate bodies, cyanophycin granules, lipid bodies, membrane limited crystalline inclusions, volume and number of wall layers and mesosomes was observed. These reductions were more pronounced in both acidic and alkaline medium than at pH 7.2. At 0.12 μM Cd, the uptake increased with alkaline pH values, and uptake was greater at pH 7.2 than at either acid or alkaline pHs. Lysis of cell wall at 1.18 μM Cd showed the following decreasing trend: pH 4.0 > pH 5.5 > pH 10.0 > pH 9.0 > pH 7.2. There was a total loss of lipid bodies at 1.18 μM Cd at all pH values listed.It is suggested that these techniques can be successfully employed for bioassay studies of metal toxicity to algae. In particular, cell wall lysis and loss of lipids by algae are good indicators of pH effects and metal toxicity in the aquatic ecosystem.