Effects of veterinary fences on Wildlife conservation in Zimbabwe

In Zimbabwe, veterinary fences are used to control trypanosomiasis and foot- and-mouth disease, two important diseases that threaten cattle production and beef exports. Wildlife is implicated in both instances and the effects of fences on wildlife conservation and land use are discussed in relation to these two diseases. Advantages and disadvantages related to direct and indirect fence effects are outlined. Although the maintenance of fences for trypanosomiasis control is likely to become obsolete, control of foot- and-mouth disease will rely on fences for the foreseeable future. Most of Zimbabwe's protected wildlife areas are located in marginal agricultural land around the periphery of the country where cattle productivity is low. This land should be excluded from any involvement in the beef export industry rather than attempting its inclusion through cordoning and isolating individual protected areas. Within such land, the need for rigid veterinary restrictions should then disappear and allow more flexible strategies for disease control, including adaptive and imaginative approaches to land-use planning.     

Phylogenetic relationships of the intercellular fish pathogenIchthyophonus hoferi and fungi,choanoflagellates and the rosette agent

Ichthyophonus hoferi Plehn and Mulsow, 1911 is thought to be one of the few pathogenic fungal infections of marine fish. The result of an attack is severe epizootics in herring stocks with drastic reduction in the population as a consequence. The exact phylogenetic position of the genusIchthyophonus is not known. In the present study, a combination of molecular data, ultrastructure and biochemical characters were utilized to investigate the phylogeny ofI.hoferi. The genomic DNA encoding the small subunit ribosomal RNA (18S rRNA) was amplified and sequenced. Comparisons with other eukaryotic 18S rRNA sequences indicate thatI. hoferi is not a member of the Fungi. In both the parsimony and the neighborjoining trees,I. hoferi is the sister taxon to the rosette agent. The clade encompassingI.hoferi and the rosette organism is the sister group to the chanoflagellate clade in the neighbor-joining tree, while in the parsimony tree theI. hoferi/rosette clade is equally distant to both the choanoflagellate and animal clades. Transmission electron microscopy showed thatI. hoferi has a defined cell wall, an endoplasm that consists of a fine granulated matrix with numerous ribosomes, several nuclei, vacuoles of varying density distributed throughout the cell, and mitochondria with tubular cristae. The cell wall ofI. hoferi contains chitin.     

Macroalgal growth in nutrient-enriched estuaries: A biogeochemical and evolutionary perspective

Increased nutrient loading of a body of water leads to an increase in macroalgal growth. It is generally observed, however, that certain species thrive more than others, capitalising on the increased nutrient availability. These are usually small, fast-growing, ephemeral algae that often appear as nuisance blooms. This article discusses the correlation between nutrient increase and macroalgal bloom formation. From a historical perspective, the evolutionary history of nuisance macroalgae, and the habits available to them prior to anthropogenic influences on estuarine geochemistry are considered. The occurrence of macroalgal genera whose distribution is commonly related to estuaries with high nutrient loading is discussed, along with evidence suggesting that the ecophysiological traits of r-selected, ephemeral algae largely contribute to their ecological success and bloom-formation at nutrient-enriched sites.     

Seasonality of cooling tower drift in vegetation at ORGDP

Cooling tower operation at the Oak Ridge Gaseous Diffusion Plant (ORGDP) requires the addition of a chromated corrosion inhibitor to the recirculating cooling water (RCW) system. Fluctuations in the RCW flow rates of the ORGDP cooling towers correlates with operational levels of the enrichment plant. Drift fraction is a function of the RCW flow rate, with variations in chromium deposition reflected in vegetation contamination. Fescue grass and litter were collected in the plant environs along a distance gradient, during different seasons, and analyzed for chromium. Foliar chromium concentrations were maximum (1390 μg/g) during the winter months, decreasing in spring and summer months (190 and 173 μg/g, respectively) at 13 m as the demand for cooling decreased with lower plant operations. In contrast, concentrations in litter increased with time, ranging from 894 μg/g at 13 m during the winter to 1890 and 2140 μg/g during the summer and fall months. The accumulation of chromium in the litter component was likely related to more exchange sites associated with increased litter biomass due to the seasonal senescence of foliage, whereas decreased accumulations on foliage reflected high mobility of the drift residue due to leaching and a short lifespan of individual leaves. In addition to operational considerations, the data illustrate the importance of seasonal considerations in the use of biological materials in a monitoring program.     

Precipitation-driven decrease in wildfires in British Columbia

Trends of summer precipitation and summer temperature and their influence on trends in summer drought and area burned in British Columbia (BC) were investigated for the period 1920–2000. The complexity imposed by topography was taken into account by incorporating high spatial resolution climate and fire data. Considerable regional variation in trends and in climate–fire relationships was observed. A weak but significant increase in summer temperature was detected in northeastern and coastal BC, whereas summer precipitation increased significantly in all regions—by up to 45.9 %. A significant decrease in province-wide area burned and at the level of sub-units was strongly related to increasing precipitation, more so than to changing temperature or drought severity. A stronger dependence of area burned on precipitation, a variable difficult to predict, implies that projected changes in future area burned in this region may yield higher uncertainties than in regions where temperature is predominantly the limiting factor for fire activity. We argue that analyses of fire–climate relationships must be undertaken at a sufficiently high resolution such that spatial variability in limiting factors on area burned like precipitation, temperature, and drought is captured within units.