Consumer-resource body-size relationships in natural food webs

It has been suggested that differences in body size between consumer and resource species may have important implications for interaction strengths, population dynamics, and eventually food web structure, function, and evolution. Still, the general distribution of consumer-'resource body-size ratios in real ecosystems, and whether they vary systematically among habitats or broad taxonomic groups, is poorly understood. Using a unique global database on consumer and resource body sizes, we show that the mean body-size ratios of aquatic herbivorous and detritivorous consumers are several orders of magnitude larger than those of carnivorous predators. Carnivorous predator-prey body-size ratios vary across different habitats and predator and prey types (invertebrates, ectotherm, and endotherm vertebrates). Predator-prey body-size ratios are on average significantly higher (1) in freshwater habitats than in marine or terrestrial habitats, (2) for vertebrate than for invertebrate predators, and (3) for invertebrate than for ectotherm vertebrate prey. If recent studies that relate body-size ratios to interaction strengths are general, our results suggest that mean consumer-resource interaction strengths may vary systematically across different habitat categories and consumer types.     

An overview of President Carter's Water Policy (1978)

On June 6, 1978, President Carter presented his Federal Water Policy Initiatives to the Congress. These were based on a year-long and sometimes controversial study by the Water Resources Council, the Office of Management and Budget, and the Council on Environmental Quality. Reforms were proposed relative to cost sharing, planning procedures, project evaluation, and environmental protection. Omitted from the policy were recommendations on water pollution control, planning coordination, and water resources research.The views expressed are the author's, and not necessarily those of the Library of Congress.     

Day-of-Week behavior of atmospheric ozone in three U.S. cities

The weekly cycles of atmospheric ozone (O3) are of interest because they provide information about the response of O3 to changes in anthropogenic emissions from weekdays to weekends. The weekly behavior of O3 in Chicago, IL; Philadelphia, PA; and Atlanta, GA, is contrasted. In Chicago and Philadelphia, maximum 1-hr average O3 increases on weekends. In Atlanta, O3 builds up from Mondays to Fridays and declines during weekends. In all three areas, volatile organic compound (VOC)/nitrogen oxides (NOx) ratios are higher during weekends, resulting from greater than proportionate decreases in NOx relative to VOC emissions. The VOC/NOx ratios correlate with maximum 1-hr O3 concentrations in Chicago, a response consistent with a VOC-sensitive airshed. A weak correlation between O3 concentrations and VOC/NOx ratios in Philadelphia suggests the impact of transported O3, which is formed in upwind VOC-sensitive locations that may be hundreds of kilometers away. Ozone concentrations in Atlanta do not correlate with VOC/NOx ratios but with concentrations of NOx and total reactive nitrogen (NOy) carried over from the previous day. When data from 1986-1990 and 1995-1999 are compared, only small differences in the weekly behavior of O3 are observed in Chicago and Philadelphia. The day-of-week differences in O3 are amplified in the more recent period in Atlanta, a possible result of urban growth.     

Polycyclic aromatic hydrocarbons in sediments and associated benthos in Lake Erie

Polycyclic aromatic hydrocarbons (PAH) were analyzed in surficial sediments and benthic organisms in southwestern Lake Erie near a large coal fired power plant. Sediment concentrations (530–770 ppb PAH) were relatively homogenous throughout most of the 150 km² area, although river and nearshore concentrations reached nearly 4 ppm. Oligochaete worms and chironomid midges were near equilibrium with local sediments except for enhanced concentrations in nearshore midges.     

Numerical methods for describing chemical transport in the unsaturated zone of the subsurface

Finite-difference and finite-element methods of approximation have been extended to solve the one-dimensional nonlinear partial differential equations that describe the simultaneous transport of heat, moisture and chemical in the unsaturated zone. Especially for chemical transport, nodal spacing criteria are required to minimize numerical dispersion and oscillatory behavior in the solution vector for chemical concentration. Conservative criteria for nodal spacing for saturated flow can be used to set nodal spacing for unsaturated zone transport. When nodal spacing criteria are satisfied, for the same set of transport and boundary conditions, chemical concentration profiles calculated by the two numerical methods will be almost the same. A situation that is simulated very well with one-dimensional models, is the application of chemicals to land surfaces. To compare and contrast the characteristics of solutions given by the two numerical methods, moisture content, temperature and chemical concentration profiles for a 75-day period after application in the unsaturated zone are calculated for two representative types of organic chemicals. In the first, the chemical is very slowly degraded in the subsurface environment but strongly sorbed to soil surfaces. In the second, the chemical is rapidly degraded but weakly sorbed to soil surfaces. Because of differences in sorption coefficients and mechanisms of degradation, for the same set of hydrodynamic properties of the subsurface, the weakly sorbed chemical is more widely distributed throughout the unsaturated zone, whereas the strongly sorbed chemical stays very close to where it is put initially with little penetration into the subsurface. Satisfying nodal spacing criteria minimizes the impact of the method of approximation on the calculated solutions of the transport equations. For better model predictive performance, however, there are needs for more fundamental information on processes governing transport in the subsurface.     

Ecological Monitoring for Assessing the State of the Nearshore and Open Waters of the Great Lakes

The Great Lakes Water Quality Agreement stipulates that the Governments of Canada and the United States are responsible for restoring and maintaining the chemical, physical and biological integrity of the waters of the Great Lakes Basin Ecosystem. Due to varying mandates and areas of expertise, monitoring to assess progress towards this objective is conducted by a multitude of Canadian and U.S. federal and provincial/state agencies, in cooperation with academia and regional authorities. This paper highlights selected long-term monitoring programs and discusses a number of documented ecological changes that indicate the present state of the open and nearshore waters of the Great Lakes.