Macroinvertebrate biomonitoring in intermittent coastal plain streams impacted by animal agriculture

Little attention has been given to the ecology of intermittent coastal plain streams in the southeastern United States, and it is not known whether available macroinvertebrate biomonitoring methods reliably detect degradation in these streams. This study compared differences in biomonitoring metrics between reference and agricultural streams, and between the flow period (January-April) and the intermittent flow period (May-December). Percentages of crustaceans, isopods, and Ephemeroptera-Plecoptera-Trichoptera (EPT) were significantly higher at the reference site than the two most impacted sites during the flow period, probably resulting from the abundance of leaf litter and lower temperatures. During this same period, the agriculturally impacted sites had a significantly higher percentage of dipterans--a group that thrives in the silty, nutrient-rich waters. Four metrics (percent Crustacea, Isopoda, Diptera, and EPT) had no overlap between values for the most impacted and the least impacted sites during the flow period, but no metrics were able to detect more discrete differences among sites. Sites were physically and biologically similar during the intermittent period when natural stresses (i.e., stagnant water, high temperatures, low dissolved oxygen) were high, with many metrics, such as percentages of dominant family, burrowers, chironomids, and dipterans becoming similar at all sites. Our findings indicate that development of a better understanding of invertebrate fauna in reference conditions and of the natural variation in intermittent streams is necessary to develop effective biomonitoring programs for these systems.     

The spider and fly revisited: ploy–counterploy behavior in a unique predator–prey system

Earlier studies have shown that the sarcophagid fly Arachnidomyia lindae is the principal egg-sac predator of the colonial orb-weaving spider Metepeira incrassata, and that risk of egg-sac loss increases with group size. Observations of specialized behaviors for attack (flies) and defense (spiders) suggest that this predator-prey relationship may incorporate elements of ploy and counterploy behavior. Here we explore this relationship in detail and test hypotheses regarding efficacy of attack and defense behaviors. Egg-sac guarding by the spider includes defensive behaviors specific to this fly predator, which were observed during experimental "attacks" with tethered A. lindae, but not with similar presentations of non-predatory Musca domestica. Experimental studies also show that Metepeira incrassata recognizes this predatory fly by airborne cues (i.e., the signature frequency of wing-beats), and can distinguish between this predator and other flies (potential prey) on the basis of wing-beat frequency differences. Removal of female spiders results in a significantly higher probability of unguarded egg-sacs being parasitized, demonstrating the adaptive value of spider defensive behaviors. We also present evidence that A. lindae utilizes a behavioral ploy for circumventing spider guarding behavior (aggressive mimicry - producing vibrations of captured prey in the web), and that Metepeira incrassata, in turn, exhibits a counter-ploy behavior (signal thread cutting) to eliminate this potentially distracting vibratory information. While previous studies have shown that this colonial web-building spider uses a number of general attack-abatement mechanisms against a diversity of predators and parasitoids, results of this study suggest that selection pressures from a highly specialized predator may also result in evolution of predator-specific prey responses.     

Food,feed, and fuelwood resources of Nepal: A GIS evaluation

A GIS-based land evaluation model was developed to determine the food, feed, and fuelwood sufficiency of all districts in Nepal. Resource surpluses or deficits were calculated for each district for 1981, the year for which the national land resource data were available. Of the three resources, feed supplies were found to be the most critical. Feed deficits occurred in 57% of all districts in 1981, while food and fuelwood deficits occurred in less than 10% of all districts. Different scenarios were carried out for the year 2000 to estimate the magnitude of future resource deficits, assuming resource use and yields in Nepal remain constant in the face of growing population and livestock numbers. Linking resource data with spreadsheet and GIS systems provides a new way to understand and evaluate resources at the district and national levels. To more fully capture the usefulness of this approach, information on rates of change in productivity and land use is needed.     

Estimating maquiladora hazardous waste generation on the U.S./Mexico border

Maquiladoras, manufacturing plants that primarily assemble foreign components for reexport, are located in concentrations along the northern frontier of the US/Mexico border. These plants process a wide variety of materials using modern industrial technologies within the context of developing world institutions and infrastructure. Hazardous waste generation by maquiladoras represents a critical environmental management issue because of the spatial concentration of these plants in border municipalities where the infrastructure for waste management is nonexistent or poor. These border municipalities contain rapidly increasing populations, which further stress their waste handling infrastructure capacities while exposing their populations to greater contaminant risks. Limited empirical knowledge exists concerning hazardous waste types and generation rates from maquiladorsas. There is no standard reporting method for waste generation or methodology for estimating generation rates at this time. This paper presents a method that can be used for the rapid assessment of hazardous waste generation. A first approximation of hazardous waste generation is produced for maquiladoras in the three municipalities of Nogales, Sonora, Mexicali, Baja California, and Cd. Juarez, Chihuahua, using the INVENT model developed by the World Bank. In addition, our intent is to evaluate the potential of the INVENT model for adaptation to the US/Mexico border industrial situation. The press of border industrial development, especially with the recent adoption of the NAFTA, make such assessments necessary as a basis for the environmental policy formulation and management needed in the immediate future.     

MANAGEMENT MODEL FOR CONTROLLING NITRATE CONTAMINATION IN THE NEW JERSEY PINE BARRENS AQUIFER1

ABSTRACT: Land use planning in rapidly developing areas can serve as an effective tool for minimizing water quality impacts on ground water supplies. A land use management model applied to Jackson Township of the New Jersey Pine Barrens was developed. The management model consisted of a simulation model for the transport of nitrates from septic tank systems through the aquifer and a multiobjective, goal programming optimization model to determine population density restrictions using 208 areawide planning population projections. Results showed that growth may have to be curtailed in several areas of Jackson Township and that current population projections over the next 30 years may result in unacceptably high nitrate concentrations downgradient of Jackson Township. The management framework provides a flexible approach to land use planning.     

Thermally induced formation of PCDD and PCDF from tri- and tetrachlorobenzene in dielectric fluids

The thermal behavior of dilute (5000-50 ppm) solutions of tri- and tetrachlorobenzene in mineral oil, silicone oil, and tetrachloroethylene (TCE) has been investigated. Although pyrolyses or combustion of neat chlorobenzenes readily forms significant yields of PCDDs/PCDFs, corresponding treatment of dilute solutions was generally non-productive. This result is consistent with the proposition that, under the conditions studied, the rate-limiting step for PCDD/PCDF formation is bimolecular in chlorobenzene. In contrast, earlier studies of PCBs implied a rate-limiting step that was unimolecular in chloroaromatics. Combustion of dilute solutions of chlorobenzenes in tetrachloroethylene did produce detectable concentrations of PCDF; this result reflects combination of chlorobenzene and TCE- or TCE-derived species.     

Temporal - and dose-related characteristics of biochemical and morphological alterations in the hamster induced by 2,3,7,8-tetrachlorodibenzo- -dioxin

The temporal - and dose-related characteristics of hepatic enzymes induced and toxic responses elicited in the hamster by 2,3,7,8-tetrachlorodibenzo- -dioxin were examined. The results demonstrate a dissociation of the induction of these hepatic enzymes from TCDD-elicited lethality, but not necessarily hepatic damage, in this species. Furthermore, the hyperthyroidism observed is suggestive of a role of these hormones in the relatively insensitive nature of this species to TCDD treatment.