Historical processes constrain patterns in global diatom diversity

There is a long-standing belief that microbial organisms have unlimited dispersal capabilities, are therefore ubiquitous, and show weak or absent latitudinal diversity gradients. In contrast, using a global freshwater diatom data set, we show that latitudinal gradients in local and regional genus richness are present and highly asymmetric between both hemispheres. Patterns in regional richness are explained by the degree of isolation of lake districts, while the number of locally coexisting diatom genera is highly constrained by the size of the regional diatom pool, habitat availability, and the connectivity between habitats within lake districts. At regional to global scales, historical factors explain significantly more of the observed geographic patterns in genus richness than do contemporary environmental conditions. Together, these results stress the importance of dispersal and migration in structuring diatom communities at regional to global scales. Our results are consistent with predictions from the theory of island biogeography and metacommunity concepts and likely underlie the strong provinciality and endemism observed in the relatively isolated diatom floras in the Southern Hemisphere.     

Lack of population genetic structuring in the marine planktonic diatom Pseudo-nitzschia pungens (Bacillariophyceae) in a heterogeneous area in the Southern Bight of the North Sea

Several marine holoplanktonic organisms show a high degree of geographically structured diversity for which it often remains unclear to what extent this differentiation is due to the presence of cryptic taxa. For the genetically distinct diatom Pseudo-nitzschia pungens var. pungens, we used six microsatellite markers to investigate the spatial and temporal genetic composition in the heterogeneous Southern Bight of the North Sea. Although our sampling area (ca. 100 km) comprised water bodies with different environmental conditions (marine, estuary, saline lake) and different degrees of connectivity (from complete isolation to supposedly free exchange between environments), no evidence of genetic differentiation was found. Expanding our sampling area (ca. 650 km), suggested a homogenous population structure over even larger areas in the North Sea. Our results suggest that the population structure of this diatom is mainly shaped by strong homogenizing effects of gene flow preventing genetic drift, even in water bodies with limited connectivity. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Phytotreatment of propellant contamination

Nitroglycerine (NG) and 2,4-dinitrotoluene (2,4-DNT) are propellants often found in soil and groundwater at military firing ranges. Because of the need for training with live ammunition, control or cleanup of these contaminants may be necessary for the continued use of these firing ranges. One inexpensive approach for managing sites exposed to these contaminants is the use phytoremedation, particularly using common or native grasses. In this study, the uptake of NG and 2,4-DNT from water by three common grasses, yellow nutsedge (Cyperus escalantus), yellow foxtail (Setaria glauca), and common rush (Juncus effusus), was investigated using hydroponic reactors. Rapid removal from solution by all grasses was observed, with yellow nutsedge removal rates being the highest. NG or 2,4-DNT accumulated in the tissues in all of the plants, except yellow foxtail did not accumulate NG. Higher concentrations were observed in killed roots, demonstrating the presence of plant-based enzymes actively transforming the contaminants. Yellow nutsedge was also grown in 2,4-DNT spiked soil. Significant uptake into the plants roots and leaves was observed and concentrations in the soil decreased rapidly, although 2,4-DNT concentration also decreased in the unplanted controls. In summary, the three grasses tested appear to be good candidates for phytoremediation of propellant contamination.     

Toward an inherently safer design and operation of batch and semi-batch processes: The N-oxidation of alkylpyridines

This work shows an application of inherent safety principles to a reaction widely used in the pharmaceutical industry. More specifically, it incorporates the teachings of Trevor Kletz into the design of an inherently safer process for the N-oxidation of alkylpyridines. This reaction is of interest because of the hazards resulting from the undesired, gas-generating decomposition of hydrogen peroxide, the oxidizing agent. The generation of oxygen, combined with the flammability of the alkylpyridines, represents a serious fire and explosion hazard for this process. The purpose of this paper is to demonstrate how an inherently safer process can be potentially achieved by designing improved reactors and by assessing conditions that reduce or eliminate the hazards. Furthermore, it is shown that such improvement in safety increases the efficiency of the process and results in a cost reduction.     

Tolerance and metabolism of phenol and chloroderivatives by hairy root cultures of Daucus carota L

Hairy root cultures are shown to be suitable experimental systems to screen higher plants for tolerance to various inorganic and organic pollutants, and for determining the role of the root matrix in the uptake and further metabolism of contaminants. A number of clones were obtained by infection of carrot tissues with Agrobacterium rhizogenes and two (the fastest and the slowest growing root clones) were chosen for further experimentation. Both clones showed a similar degree of tolerance towards phenol and its chlorinated derivatives, i.e. the growth of root biomass was maintained in concentrations of phenol equivalent to 1000 micromol/l, whilst the chlorophenols were tolerated only at concentrations 20 times lower (50 micromol/l). Transformed carrot roots were able to remove more than 90% of the exogenous phenolic compounds from the culture medium within 120 h after treatment. Metabolism of these compounds occurred in the root tissue and was accompanied by an increase in peroxidase activity.     

A comparison of swine wastewater treatment using real-time and fixed-time two-stage sequencing batch reactors

This study compared the swine wastewater treatment of two identical lab-scale two-stage sequencing batch reactors (TSSBR) under similar conditions except that one was operated on a fixed-time mode and the other on a real-time mode. While both TSSBR systems performed very well, the real-time TSSBR performed far better then the fixed-time TSSBR, in every aspect of carbon, nitrogen, and phosphorous removal. The removals of COD, TOC, were at 97% and for BOD5 even at 99.7%. In terms of NH4-N and TKN removals, the real-time TSSBR achieved removal of over 98%. For phosphorus removals (Ortho-P and total P) the results from the real-time TSSBR was quite remarkable at 97.7%.     

Benefits of sustainable waste management in the vegetable greenhouse industry

This study investigated the benefits of an on-site sustainable solid waste treatment and utilization system for the greenhouse industry. The composts made from greenhouse wastes were tested and found to contain high nutrient values and good physical properties, and could be used as high quality growing media. The finished composts were tested in a greenhouse against the conventional growth media (sawdust) and resulted in a 10% yield increase by using the compost. An economic analysis was conducted to show the economic benefits of on-site composting for a greenhouse operation. Based on a four-hectare tomato or pepper greenhouse, and amortizing the capital equipment over five years, the net annual cost of composting represents a savings of dollars 8,000 annually.