Growth and development of cellular slime mould Dictyostelium discoideum treated with DDT

The effects of dichlorodiphenyl trichloroethane (DDT) on the growth, phagocytic activity, ultrastructure and developmental stages of a well known species of the cellular slime mould, Dictyostelium discoideum were studied. DDT, at doses of 60 ppm and above, inhibited growth of the vegetative cells and this was also evident from the colony blots which were smaller in size. A dose-dependent inhibition occurred in the phagocytic activity and macromolecular syntheses of DDT-treated cells. The cytomorphology of growing Dictyostelium cells, as revealed under light and electron microscopes, was profoundly affected by DDT treatment. Further, a considerable delay occurred in the various morphogenetic events in the slime mould cells exposed to DDT.     

Induction of metamorphosis in larvae of the oyster Crassostrea gigas using neuroactive compounds

Chemical (neuroactive compounds at different concentrations and exposure times) and physical (water agitation, light) factors with potential effects on the metamorphosis of larvae of the oyster Crassostrea gigas (Thunberg) larvae have been studied. The neurotransmitters l-dihydroxyphenylalanine (DO), epinephrine (EP), norepinephrine (NE), and acetylcholine (AC) have been identified as very active inducers of metamorphosis, whilst serotonin (SE), dopamine (DA) and potassium (K) were less effective inducers. The -aminobutyric acid (GA) and ammonium (AM) were found ineffective at the concentrations tested. Exposure to 10^-4 M EP for 15 min was sufficient to promote >80% metamorphosis within 48 h, whereas NE required 2 h to exert comparable induction. Maximum induction by DO (>50%) was achieved after 2 h exposure to 10^-4 M. However, unlike EP and NE, DO was lethal at that concentration in the long term. Maximum induction by AC (30% metamorphosis) was achieved at a concentration of 10^-4 M. In contrast to other neurotransmitters, AC induced settlement behaviour, cementation and eventual metamorphosis, yielding postlarvae which were all attached to the substratum. EP and NE triggered the morphogenetic changes, by-passing settlement and leading to postlarvae not cemented to the substratum. DO induced mostly attached spat at low concentrations (10^-5 M) and unattached spat at high concentrations (10^-4 M), and a similar pattern was apparent for the weaker inducers SE and DA. Regarding physical factors, a highly reflectant surface significantly increased the percentage of attached spat obtained, compared to a dark bottom. No consistent effect of water current or light was detected on the production of unattached spat. The three different forms of induction are discussed in relation to different regulatory pathways of settlement and metamorphosis.     

Phytomonitoring and management of tar piles on the Qatari coastal marshes, Arabian Gulf

Most of the shores in Qatar and other oil producing countries have had a long history of crude oil pollution from different sources. This pilot study was to assess the problem and suggest a management programme for disposing of the collected tar or lessening the impact of tar accumulation. The vegetation on the sites used for dumping tar was used in a field survey to identify bioindicators of tar pollution and of the natural recovery of polluted sites. The phytomonitoring results indicate that recovery of polluted sites can be quite rapid after clean-up and restoration. To facilitate natural plant invasion and colonization, and the restoration of tar piles, the dumping sites must have plant communities with high species diversity and a high percentage of annual plants. Depending on the sand-tar ratio in the piles, artificial seeding of selected plant species (listed) can be applied by using species mixes or single species seeding. Management techniques are suggested to optimize the natural recovery and revegetation of tar-affected coastal marshes.     

Interactions between copper and cadmium modify metal organ distribution in mature tilapia, Oreochromis mossambicus

Sexually mature female tilapia were exposed to sublethal concentrations of waterborne Cu and/or Cd over 6 days, and subsequent body concentrations of these metals were determined in several organs. The results show that the distribution of Cu and Cd was metal and organ specific. This is demonstrated, for example, by the observation that in tilapia, Cu exposure did not result in Cu accumulation in the liver, whereas in the intestinal wall, notably high concentrations of Cu and Cd were measured in metal exposed fish. In addition to single metal exposed fish, we also determined Cu and Cd body distribution in Cu?Cd co-exposed fish. The observed interactions in metal accumulation were most pronounced in the organs of fish exposed to low, environmentally realistic, metal concentrations.     

Marginal bleaching of thalli of Rhizocarpon as evidence for acid rain in the Norra Storfjället, Sweden

Recent lichen surveys in the foreland of The Syterb?cken glacier reveal that the crustose lichens, principally species of Rhizocarpon section Rhizocarpon, exhibit marginal bleaching, readily distinguishable from normal pigmented forms. The largest elliptical thallus of Rhizocarpon measured 290 mm maximum diameter on a bedrock outcrop beyond the margin of Little Ice Age moraines in the upper Syterb?cken Valley. Many small and large thalli of Rhizocarpon suffered damage to the periphery of individual thalli. We examine here some of the possible hypotheses explaining these occurrences. Among others, these are bedrock lithology, ice crystal blasting, long-term snowbank cover, ultraviolet exposure and acid rain. While at this time none of the possibilities can be ruled out entirely, acid rain would appear to be at least one of the factors involved. Acid rain, which is known to produce a soil pH as low as 3.3 in the field area, appears to provide a high input of H(+) ions that the lichen algal component cannot withstand. However, the lack of similar effects on associated foliose or fruticose forms raises the possibility that perhaps two or more factors specific to the environment of Rhizocarpon are operating.     

The effect of catch crops on sulphate leaching and availability of S in the succeeding crop on sandy loam soil in Denmark

Sulphate leaching losses may reduce the long-term possibility of maintaining the S supply of crops in low input farming systems. The ability of catch crops (Italian ryegrass (Lolium multiflorum Lam), winter rape (Brassica napus L.) and fodder radish (Raphanus sativus L.)) to reduce soil sulphate concentrations in autumn and make it available to a succeeding crop was investigated in 1996–1998 on sandy loam soil in Denmark. All catch crops reduced soil sulphate concentrations in the autumn compared to bare soil. Especially, the cruciferous catch crops had the ability to deplete efficiently soil sulphate levels and thus, reduce the sulphate leaching potential. The S uptake in aboveground catch crop was 8, 22 and 36 kg S per ha for ryegrass, winter rape and fodder radish, respectively. In the following spring, sulphate levels of the autumn bare soil were low in the top 0.5 m and a peak of sulphate was found at 0.75–1 m depth. In contrast, where a fodder radish catch crop had been grown, high sulphate levels were present in the top 0.5 m, but only small amounts of sulphate were found at 0.5–1.5 m depth. In spring barley (Hordeum vulgare L.), that followed catch crops, S concentrations at heading and maturity revealed that the availability of soil S increased following winter rape and fodder radish, whereas there were indications that following ryegrass, the S availability was reduced compared to bare soil. This initial study showed that catch crops have a high potential for reducing sulphate leaching and may be used to synchronise S availability with plant demand in a crop rotation.     

Uranium enrichment by the separation-nozzle process

The Science of Nature - The development of reliable manufacturing methods for commercial separation elements, the successful operation of separative stages, and extensive tests performed on plant...     

Ecoprofit-Styria-prepare Thirteen pollution prevention case studies in the Styrian industry

The paper focuses upon the organization of a federal state-funded pollution prevention project in the Styrian industry. The project includes 13 companies from the textile, pulp and paper, machine building, wood working and printed circuit board manufacturing industries, covering most of the sectors and sizes in the Styrian industry. It started in January 1994 and will last for one year. It will demonstrate the possibilities of pollution prevention and the need for further research work. This project will make use of the methods and tools that were refined in the Austrian Prepare project. As a first step, a systematic balance of all the inputs and outputs of a company is made, after which the weak points and inefficiencies of material and energy use are identified and the options for improvements, both economical and ecological, are defined. Consequently, modifications in products and production lead to a situation with less waste and emissions. The preliminary lessons from these projects are presented: as a rule, the utilities (consumption of process materials and water, cleaning, energy, preparatory and finishing steps) are treated as black boxes and usually represent a considerable optimization potential. In these areas especially there is usually a lack of information and coordination as well as a need for a systematic and comprehensive approach. Leadership in the company and creative consultants are needed for starting lasting successful pollution prevention projects.