Accumulation of aluminium by the freshwater crustacean Asellus aquaticus in neutral water

This study examined the accumulation of aluminium (Al), mostly as the insoluble (Al(OH)(3)) species, by the freshwater crustacean Asellus aquaticus at neutral pH. Animals were exposed to a range of Al concentrations (5-356 microg l(-1)) in three experiments. The first two were of 30 and 50 days duration, respectively, followed by transfer of the A. aquaticus to water containing no Al for 20 days. The third used live and dead animals in order to investigate the contribution made by surface adsorption of Al to the total accumulated. Significant accumulation of Al in the whole tissues occurred by day 10 in all animals in the 30- and 50- day experiment. Peak concentrations of Al were measured in animals between days 10 and 20 with high concentration factors ranging from 1.4 x 10(4) to 5.5 x 10(3). By day 30, accumulated Al had fallen but was still significantly greater than the control in the 50- day exposure experiment. This 30- day increase followed by decreased accumulation of Al was repeated over the remaining exposure period (i.e. 30-50 days) although rates of uptake and loss and peak tissue levels of Al were higher. Proportionality between environmental (water) and tissue concentrations of Al occurred at day 20 but not at day 45. Significantly more Al was accumulated by dead animals than live animals at all Al exposure concentrations. These results suggest that Al is available to the crustacean at neutral pH and that the cuticle may provide an important site of uptake.     

ROLE OF CARBONATE ROCKS IN MODIFYING FLOOD FLOW BEHAVIOR1

ABSTRACT. The interrelationships between the runoff characteristics of watersheds (expressed as the mean annual flood), standard basin parameters (area, drainage properties, and relief), and the parameters which describe the solutional modification of the basins (carbonate rock fractions, sinkhole development, and measures of internal drainage) were used to group 62 carbonate watersheds. Simple binary correlations were obtained by direct plotting of the data. This was followed by multivariate analyses: factor and cluster analyses. Following the cluster analysis, which separated the basins into three groups, the variance within each group was examined again by binary correlations and by factor analysis. Prediction equations for those basins underlain by dolomite rock [QBAR = 12.4 TOT^1.01] and for those basins underlain by carbonate rock with very little surface expression [QBAR = 43.5 TOT^0.87] were proposed. Basins underlain by karstic limestone had a large amount of variance within the data set; therefore no prediction equation could be obtained. (QBAR = mean annual flood, cfs; TOT = total length of all blue lines shown on topographic maps, miles.)     

Agricultural area impacts within a natural area: Cades cove,a case history

Agricultural management in Cades Cove, an historic district in Great Smoky Mountains National Park, has affected natural resources both within the district and in the adjoining natural areas. Aquatic impacts of haying and cattle grazing included increases in water temperatures, turbidity, nutrient loading, and bacterial counts and decreases in benthic macroinvertebrate density and fish biomass. Wildlife populations, including groundhogs, wild turkeys, and white-tailed deer, have increased in the open fields and around the periphery of the historic district. Intensive deer foraging has removed deciduous seedlings and saplings from woodlots, lowering species diversity and favoring coniferous reproduction. Cades Cove has limestone habitats unique in the park, and both deer browse and cattle grazing may have disturbed populations of rare plant species. Effects on water quality are detectable at a campground 15 stream km from the agricultural area, and the effects of deer foraging extend about 1 km beyond the open fields.Since historic landscape preservation is presently a goal of the park, managing for open vistas in Cades Cove will require some sort of continuing disturbance. Conversion of cattle pastures to hayfields would reduce aquatic impacts but the deer herd might increase as a result of reduced competition for forage. Retarding old field succession would increase populations of native plant species dependent on sunlight, but would require government-funded mowing. Other options are discussed. Completely eliminating the effects of the historic district on adjoining areas may be impossible, at least under present economic constraints.     

Modelling the costs of fox predation and preventive measures on sheep farms in Britain

Economic analysis is a useful tool to aid decisions on what to do about wildlife impacts, such as those of vertebrate predators on livestock farmers. The case-study of lamb predation by foxes in Britain is used to develop a theoretical economic model, with the aim of determining a financially optimal solution to minimise the total costs of livestock predation at the farm-level. Total costs include output losses and expenditure on preventive and control measures, in this case indoor housing and lethal fox control. The model is tested empirically with data from a questionnaire survey of sheep farmers and field data on fox population densities in Britain. Regression analyses are used to determine the relationships between lamb losses and expenditure on indoor housing, fox population density and other non-management characteristics. The effect of fox abundance on the cost of fox control is also assessed. Marginal analysis is used to determine the total cost-minimising solution from the farmer's point-of-view, in terms of how many ewes should be housed indoors and for how long, as well as how many foxes should be killed in addition to any lethal control already carried out. Optimal solutions vary according to farm characteristics, including flock size and the regional location of farms. In all cases, to minimise the costs of predation, as many ewes as possible should be housed. However, it is not worthwhile housing them for more than a day after lambing. Efficient fox predation management does not necessarily mean that lamb losses should be reduced to zero, and additional fox control is not worthwhile on the majority of farms. The analysis provides a framework for future evaluations of wildlife impacts and cost-effective management of these problems.     

INTEGRATED ECHO SOUNDER,GPS, AND GIS FOR RESERVOIR SEDIMENTATION STUDIES: EXAMPLES FROM TWO ARKANSAS LAKES1

ABSTRACT: Bathymetric and sedimentation surveys were conducted using a dual frequency (28/200 kHz) echo sounder system in two reservoirs (Lee Creek Reservoir and Lake Shepherd Springs) in the Ozark Plateau of northwestern Arkansas. Echo sounder survey data were merged within geographic information system (GIS) software to provide detailed visualization and analyses of current depths, pre‐impoundment topography, distribution, thickness, and volume estimates of lacustrine sediment, time averaged sediment accumulation rates, long term average annual sediment flux, and water storage capacity. Calculated long term average sediment accumulation rates were used to model sediment infilling and projected lifetimes of each reservoir. Results from echo sounder surveys and GIS analyses suggest that the Lee Creek Reservoir has a projected lifetime of approximately 500 years compared to a projected lifetime for Lake Shepherd Springs of approximately 3,000 years. Estimated differences in projected lifetimes of these reservoirs reflected differences in initial reservoir volume and long term average annual sediment flux from the respective watersheds related to watershed area, physiography, land cover, and land use. The universal soil loss equation (USLE) model generated sediment fluxes an order of magnitude larger from the watersheds of both reservoirs compared to the geophysical data estimates. This study demonstrated the utility of merging geophysical survey (echo sounder) data within a GIS as an aid to understanding patterns of reservoir sedimentation. These data and analyses also provide a baseline relevant to understanding sedimentation processes and are necessary for development of long term management plans for these reservoirs and their watersheds.     

Nitrification and denitrification rates of Everglades wetland soils along a phosphorus-impacted gradient

Little information is available on the effect of phosphorus (P) enrichment on nitrogen (N) biogeochemical cycling in wetland soil. Of particular importance are the coupled nitrification-denitrification reactions that regulate the microbially mediated loss of N from wetland systems. Soils from the northern Florida Everglades have been affected by P loading from surface waters over the past 40 years. Elevated P levels have been show to have an effect on the size and activity of the microbial pool and a decrease in the N to P ratio of the microbial biomass. The objective of the study was to determine if P enrichment in soils affected microbial activities related to nitrification and denitrification in these flooded, peat soils. Potential nitrification rates of soil and detritus were determined using constantly stirred reactors under aerobic conditions while denitrification rates were determined from anaerobic incubations of slurry. Nitrification rates showed two distinct linear phases, a slower initial rate, signifying activity of nitrifiers present, followed by a sharp increase in the NH4+ conversion rate indicative of maximum potential rates. Initial rates of nitrification were highest in the surficial detrital layer decreasing with soil depth and did not correlate to soil total P. The potential rates of nitrification were 13 times greater than the initial rates. Potential denitrification rates were highest in the detritus and 0- to 10-cm soil interval with significantly lower values in the 10- to 30-cm soil interval, significantly correlated to total P of the soil. A significant (P < 0.01) relationship was seen between potential denitrification rates and soil total P suggesting an increased rate of N removal from P-enriched regions of the northern Everglades.     

Influence of form and quantity of selenium on the development and survival of an insect herbivore

Even plants classified as 'nonaccumulators' can sequester concentrations of sodium selenate, sodium selenite, selenocystine and selenomethionine that can strongly influence insect development and survival. These forms of selenium (Se), tested in diet-incorporation bioassays, proved toxic to larvae of a generalist insect herbivore at relatively low levels. Sodium selenite was the most toxic form tested against Spodoptera exigua (Hübner), with an LC(50) of 9.14 microg g(-1) wet wt (21.11 microg g(-1) dry wt). Selenocystine was intermediate with an LC(50) of 15.2 microg g(-1) wet wt. The least toxic forms, sodium selenate and selenomethionine, had LC(50)s below 50 microg g(-1) dry wt, the upper level for tissues of plants classified as nonaccumulators. Ingestion of some forms of Se also affected growth and development. Increasing concentrations of sodium selenate and sodium selenite decreased pupal weight and added significantly to the time needed for development to the pupal and adult stages. The time required to complete the larval stage increased by over 25% and the time from egg to adult emergence was extended by 22% to nearly 30%. Selenocystine and selenomethionine did not significantly increase developmental times, even at concentrations that killed 90% or more of the test populations. Analyses of relative growth rate, relative growth index, and an analysis of covariance technique for measuring growth indicated that the form of Se affected growth rates, growth inhibition responses of the larvae, and toxicological effects. Thus, quantity and the form of Se accumulating in plants grown on Se-contaminated sites are likely to influence the population dynamics of insect herbivores. The implications of these results for the ecology of contaminated sites are discussed.     

Environmental management in an international consumer goods company

Many management processes and tools can provide companies with information to support their environmental decision making. Risk assessment, environmental auditing, life cycle assessment and environmental reporting are but a few examples. Each of these has typically evolved independently as the need for it has arisen. Today, however, this abundance of tools can lead to confusion: What is the exact objective of each tool? How do they differ? Are some ‘better’ than others? Should they be used in parallel, sequentially or in place of each other? More importantly, how do they fit together into a coherent environmental management framework that will ensure sound environmental and economic decision making in a company? This paper seeks to answer these questions. It describes the overall environmental framework that has been developed internally within Procter & Gamble and which allows the company to make coherent economically and environmentally sound decisions, in both the short- and long-term.