INTERNATIONAL MANAGEMENT OF THE GREAT LAKES-ST. LAWRENCE BASIN1

Neither Canada nor the United States attach much importance to the International Joint Commission (IJC) judging by the size of staffs and annual budgets. The Commission has been restricted to a relatively minor number of functions in the Great Lakes-St. Lawrence. It has investigated: the degree and causes of water and air quality deterioration; the effects of hydroelectric and navigation projects on water levels; the impacts of water-level fluctuations; and the feasibility of a deep waterway from the St. Lawrence to the Hudson River. Projects approved by the Commission have produced less than might be expected through no fault of the Commission. The Great Lakes Fishery Commission has promoted little international management. Budgetary limitations restrict its lamprey control program; institutional limitations restrict its ability to deal effectively with fishery problems. Commission responsibilities are limited to coordination and advisory functions. Since Canada and the United States have not chosen to refer most aspects of river basin management to international bodies, an institutional void exists in the Great Lakes Basin to consider these questions on a continuous basis. There is a need for expanded international cooperation.     

An advantage to mate choice in the seaweed fly,Coelopa frigida

Summary All natural populations studied of the seaweed fly, Coelopa frigida, are polymorphic for the inversion system on chromosome I. It has previously been shown that heterokaryotypes have superior egg-to-adult survival than either homokaryotype, and that there is non-random mating with respect to inversion genotypes. We have inquired whether the production of fitter progeny in larger numbers is the possible reason for the existence of non-random mating behaviour. We measured the fertility, fecundity and progeny survival of adults that have either been allowed to exercise mate preference, or been given a single, randomly chosen, mate. The fertility (% of females producing progeny) and progeny survival (% of larvae surviving to the late 3rd instar stage) are both significantly greater in choice than nochoice females. There are also significant differences in fertility and progeny survival depending on whether the parents were of similar or dissimilar inversion genotypes. An effect of relative adult size on fertility was also observed. There appear to be no effects of mate choice on fecundity. Indirect evidence is presented that adults are choosing their mates not only on the basis of genotypes but on other criteria as well. It is suggested that the superior reproductive performance of animals allowed a choice of mates may account for the evolutionary origin and continued existence of mate discrimination. Furthermore, since over 25% of the genome of Coelopa is located within inversions, the observed pattern of negative assortative mating may maintain a substantial fraction of the genes in a polymorphic state.     

Morphologic development, relative sea level rise and sustainable management of water and sediment in the Ebre Delta, Spain

The Ebre (Ebro) Delta is one of the most important wetland areas in the western Mediterranean. Ca. 40 % of the delta plain is less than 0.5 m above mean sea level and part of the southern margin of the delta is at mean sea level in an area protected by dikes. Both mean rates of secular subsidence in the Ebre Delta and eustatic sea level rise are ca. 1 – 2 mm/yr. Thus, the present annual relative sea level rise (RSLR) rate in the Ebre Delta may be at least 3 mm/yr. Measured accretion rates in the delta range from 4 mm/yr in the wetlands surrounding the river mouth to <0.1 mm/yr in impounded salt marshes and rice fields. The annual sediment deficit in the delta plain to offset RSLR is close to 1 million m³/yr. Accretion rates in the rice fields prior to the construction of large dams in the Ebre watershed were higher than RSLR rates, from 3 – 15 mm/yr. At present, >99 % of the riverine sediments are retained in the reservoirs and rice fields are losing ca. 0.2 mm/yr. Future management plans should take RSLR into account and include control of freshwater and sediment flows from the river in order to offset negative effects from waterlogging and salt intrusion, and maintain land elevation. This will include the partial removal of sediments trapped behind the Ribarroja and Mequinença dams. Stocks and inputs of sediments in the corresponding reservoirs are large enough for land elevation of ca. 50 cm in the whole delta plain. Advantages of this solution include (1) new sediments to the delta to offset subsidence (via rice fields) and coastal retreat, (2) enhanced functioning of the delta (productivity and nutrient processing), (3) avoidance of accumulation of sediments in the reservoirs. Hence, it is important to manage river discharges at the dams from an integrated viewpoint, whereas currently only hydropower and agricultural requirements are considered. It is also crucial to maintain periods of high discharge, to have enough river energy to transport as much sediments as possible.     

The use of legumes for reclaiming copper mine wastes in the Southwestern USA

Seeds of three legumes, blue lupine (Lupinus hirsutus L.), sesbania (Sesbania macrocarpa Muhl.), and alfalfa (Medicago sativa L.) were broadcast planted on four soil materials (desert soil, overburden, overburden plus tailings, and tailings) associated with copper mines near Tucson, Arizona. Experiments were conducted to study the effects of the four soil materials on germination (emergence), seedling establishment, and growth over a two-year period (1974 and 1975). All species grew best on desert soil, followed by overburden, overburden plus tailings, and tailings, in decreasing order. The presence of copper in overburden plus tailings and in tailings may have created a toxicity effect that limited the growth of plants in these two soil materials. Alfalfa was superior on all soil materials. Sesbania and blue lupine grew equally well. All three species were able to adapt to the different soil materials. For revegetation on copper mine wastes, it is desirable to plant a variety of plant species rather than a single species, to help blend the disturbed areas into the surrounding environmentApproved for publication as Arizona Agricultural Experiment Station Research Contribution No. 3100.     

Infrastructure and Conservation Policy in Brazil

Abstract:  The development of transportation and energy infrastructure has been a major driver in the conversion of natural ecosystems in Brazil since the nineteenth century. Although this pattern is present in most countries, Brazil differs in the scale of opportunities that are still available to build its physical infrastructure while pursuing an ambitious conservation agenda. This advantage stems from the magnitude of intact ecosystems, a dynamic policy environment, and the increasing availability of biological and economic data needed to harmonize conservation with public works. Success depends on integrating conservation and infrastructure planning, rather than relying on the project based, largely ineffective environmental assessment process. Front-loading environmental mitigation and compensation will also help, as will improving public access to, and understanding of, information on the environmental and economic values at stake in major infrastructure decisions.     

Hygroscopic organic aerosols during BRAVO?

The hygroscopic properties of the organic fraction of aerosols are poorly understood. The ability of organic aerosols to absorb water as a function of relative humidity (RH) was examined using data collected during the 1999 Big Bend Regional Aerosol and Visibility Observational Study (BRAVO). (On average, organics accounted for 22% of fine particulate matter with an aerodynamic diameter less than 2.5 microm (PM2.5) mass). Hourly RH exceeded 80% only 3.5% of the time and averaged 44%. BRAVO aerosol chemical composition and dry particle size distributions were used to estimate PM2.5 light scattering (Bsp) at low and high ambient RH. Liquid water growth associated with inorganic species was sufficient to account for measured Bsp for RH between 70 and 95%.     

Optical measurements of aerosol size distributions in Great Smoky Mountains National Park: dry aerosol characterization

Aerosol size distributions were measured during the summertime 1995 Southeastern Aerosol and Visibility Study (SEAVS) in Great Smoky Mountains National Park using an Active Scattering Aerosol Spectrometer (ASASP-X) optical particle counter. We present an overview of the experimental method, our data inversion technique, timelines of the size distribution parameters, and calculations of dry accumulation mode aerosol density and refractive index. Aerosol size distributions were recorded during daylight hours for aerosol in the size range 0.1 < Dp < 2.5 microns. The particle refractive index used for the data inversion was calculated with the partial molar refractive index approach using 12-hr measured aerosol chemical composition. Aerosol accumulation mode volume concentrations ranging from 1 to 26 micron 3 cm-3 were observed, with an average of 7 +/- 5 micron 3 cm-3. The study average dry accumulation mode geometric volume median diameter was 0.27 +/- 0.03 micron, and the mean geometric standard deviation was 1.45 +/- 0.06. Using an internally mixed aerosol model, and assuming chemical homogeneity across the measured particle distribution, an average accumulation mode dry sulfate ion mass scattering efficiency of 3.8 +/- 0.6 m2 g-1 was calculated.     

Role of manganese oxides in the exposure of mute swans (Cygnus olor) to Pb and other elements in the Chesapeake Bay, USA

The aims of this study are to estimate exposure of waterfowl to elements in contaminated sediments in the Chesapeake Bay and to consider the potential role of Mn in influencing bioavailability and exposure. Metal concentrations were measured in livers and digesta taken from mute swans living on the Aberdeen Proving Ground, whose sediment had elevated concentrations of Cu, S, Se, Zn, As, Co, Cr, Hg and Pb. Concentrations of only the first four of these elements were elevated in swan digesta. None of the concentrations detected in the digesta or livers of the swans was considered toxic, although the concentrations of Cu and Se were high compared to concentrations of these elements reported in other waterfowl. Lead was found to be scavenged by Mn and Fe oxides from the water and deposited on the surface of vegetation at a reference site. Under some environmental chemical conditions, this is an important route of exposure to Pb in waterfowl, not previously recognized.     

An assessment of the chronic toxicity of the synthetic pyrethroid, fenvalerate, to Daphnia galeata mendotae, using life tables

The effects of chronic exposure to fenvalerate, a synthetic pyrethroid insecticide, on the cladoceran Daphnia galeata mendotae were evaluated under laboratory conditions. The daphnids were exposed for their entire life cycle to concentrations ranging from 0.005 to 0.1 microg fenvalerate litre(-1). The parameters used to determined toxicity were survival, time to first reproduction, reproductive frequency, number of young per brood, cumulative brood size, intrinsic rate of natural increase (r(m)), generation time (T) and net reproductive rate (R(0)). A concentration of 0.005 microg fenvalerate litre(-1) resulted in an increase in longevity but a decrease in production of young. Higher concentrations caused a decrease in survival. Studies of shorter duration than the complete life cycle of the organisms would not have detected toxicity at such low levels. The intrinsic rate of natural increase, r(m), was not affected by fenvalerate until concentration reached 0.05 microg litre(-1) and r(m) decreased to 0.113 from 0.238. A concentration of 0.01 microg litre(-1) caused the net reproductive rate, R(0), and the generation time, T, to decrease to 73.2 offspring per female and 17.3 days from 125.9 offspring per female and 20.3 days, respectively.     

Utility analysis for the probationary selection decision to obtain a fixed quota of successful selectees

This article presents the extension of the one-cohort probationary selection (OCPS) framework (De Corte, 1994) to a multiple cohort model and shows how the extension can be applied to estimate the utility of probationary selection with replacement (PSWR) when a fixed quota of successfully performing selectees is required. Next, formulas to compute the net present value of the OCPS and the PSWR approach to the selection of a fixed quota of successful employees are derived. The equations indicate that the latter approach will usually lead to a higher utility, but not necessarily to a higher net present value of the predictor selected workforce. This finding, which is corroborated by the results of an example application, is of immediate practical relevance because it justifies the probationary selection with replacement practice that is adopted in many West European countries. Finally, the example results suggest also that the traditional Brogden–Cronbach–Gleser framework generally overestimates the incremental utility of using a predictor when the objective is to select a fixed quota of successful selectees. © 1997 John Wiley & Sons, Ltd.