Linking stream and landscape trajectories in the southern Appalachians

A proactive sampling strategy was designed and implemented in 2000 to document changes in streams whose catchment land uses were predicted to change over the next two decades due to increased building density. Diatoms, macroinvertebrates, fishes, suspended sediment, dissolved solids, and bed composition were measured at two reference sites and six sites where a socioeconomic model suggested new building construction would influence stream ecosystems in the future; we label these "hazard sites." The six hazard sites were located in catchments with forested and agricultural land use histories. Diatoms were species-poor at reference sites, where riparian forest cover was significantly higher than all other sites. Cluster analysis, Wishart's distance function, non-metric multidimensional scaling, indicator species analysis, and t-tests show that macroinvertebrate assemblages, fish assemblages, in situ physical measures, and catchment land use and land cover were different between streams whose catchments were mostly forested, relative to those with agricultural land use histories and varying levels of current and predicted development. Comparing initial results with other regional studies, we predict homogenization of fauna with increased nutrient inputs and sediment associated with agricultural sites where more intense building activities are occurring. Based on statistical separability of sampled sites, catchment classes were identified and mapped throughout an 8,600 km(2) region in western North Carolina's Blue Ridge physiographic province. The classification is a generalized representation of two ongoing trajectories of land use change that we suggest will support streams with diverging biota and physical conditions over the next two decades.     

Application of a Three-Dimensional Water Quality Model as a Decision Support Tool for the Management of Land-Use Changes in the Catchment of an Oligotrophic Lake

While expansion of agricultural land area and intensification of agricultural practices through irrigation and fertilizer use can bring many benefits to communities, intensifying land use also causes more contaminants, such as nutrients and pesticides, to enter rivers, lakes, and groundwater. For lakes such as Benmore in the Waitaki catchment, South Island, New Zealand, an area which is currently undergoing agricultural intensification, this could potentially lead to marked degradation of water clarity as well as effects on ecological, recreational, commercial, and tourism values. We undertook a modeling study to demonstrate science-based options for consideration of agricultural intensification in the catchment of Lake Benmore. Based on model simulations of a range of potential future nutrient loadings, it is clear that different areas within Lake Benmore may respond differently to increased nutrient loadings. A western arm (Ahuriri) could be most severely affected by land-use changes and associated increases in nutrient loadings. Lake-wide annual averages of an eutrophication indicator, the trophic level index (TLI) were derived from simulated chlorophyll a, total nitrogen, and total phosphorus concentrations. Results suggest that the lake will shift from oligotrophic (TLI = 2–3) to eutrophic (TLI = 4–5) as external loadings are increased eightfold over current baseline loads, corresponding to the potential land-use intensification in the catchment. This study provides a basis for use of model results in a decision-making process by outlining the environmental consequences of a series of land-use management options, and quantifying nutrient load limits needed to achieve defined trophic state objectives.     

SIMULATION OF URBAN NON-POINT SOURCE POLLUTION1

ABSTRACT: Public Law 92–00 has mandated the need for evaluating the impact of nonpoint source pollution on receiving water quality, primarily through Section 208 Areawide Planning. The Management of Urban Non-Point Pollution (MUNP) model was developed to estimate the accumulation of eight non-point pollutants on urban streets, their removal by both rainfall and street sweeping operations. The model can simulate the following pollutants: total solids or sediment-like material, volatile solids, five-day biochemical oxygen demand, chemical oxygen demand, Kjeldahl nitrogen, nitrates, phosphates, and total heavy metals. The simulated results can be used for investigation of non-point pollution management alternatives. The model is capable of reflecting variation in such diverse factors as physical and chemical characteristics of accumulated pollutants, land use characteristics, rainfall characteristics, street sweeper characteristics, roadway characteristics, and traffic conditions. By using mean estimates of many input variables for large segments of a city, the MUNP model could be used to quickly assess the magnitude of pollutants annually entering receiving waterways due to nonpoint source pollution alone. If the results indicate that non-point pollution loadings are sizeable and require futher analysis, the MUNP model could be used to define the specific nonpoint source pollution areas within a city. Hypothetical locations and actual rainfall data for Washigton D.C. were used to demonstrate some capabilities of the MUNP model.     

A regional approach to estimating recreation benefits of improved water quality

Recreation demand and value are estimated with the travel-cost method for fishing, camping, boating, and swimming on a site-specific regional basis. The model regional in that 179 sites are defined for the Pacific Northwest. A gravity model is employed to estimate the number of trips from each origin to its destination in the region, and these data are the basic input in the travel-cost demand curves. The model is illustrated by estimating the recreation benefits that would result from meeting the national environmental goal of “fishable and swimmable” rivers. The main finding is that potential recreation benefits are concentrated in a few select areas, which are accessible to large population centers.     

Reduction of stream sediment concentration by a riparian buffer: filtering of road runoff in disturbed headwater basins of montane mainland southeast Asia

We determined the extent that a riparian buffer reduces stream suspended sediment concentrations by filtering road runoff during 18 rain events in a 2.5-ha, multi-use watershed in northern Thailand. The dominant buffer species was the perennial sedge Fimbristylis aphylla Zoll. ex Steud. (Cyperaceae). We monitored stream sediment concentration for situations where road runoff either flowed into the riparian buffer or was diverted directly into the stream (buffer and no buffer scenarios). These data were used to develop the following relationships between instantaneous stream sediment concentration (Ci) and discharge (Qi): Ci= 28.329Qi(0.851) (buffer scenario) and Ci= 22.265Qi(1.579) (no buffer scenario). Using these functions to calculate total event suspended concentrations, we determined that the buffer reduced suspended sediment concentration by 34 to 87%, for the range of events monitored. Removal of sediment from runoff generated on a 2.4-m-wide, 165-m-long unpaved road section was achieved principally via ponding, which reduced the transport capacity as flow entered the relatively flat, saturated buffer. Sediment deposition occurred primarily within the first 10 m of the buffer. Some sediment was also deposited on the fillslope leading to the buffer. Maximum road sediment concentration during the largest buffer event approached 100,000 mg L(-1). Meanwhile, the corresponding maximum stream suspended sediment concentration was <4000 mg L(-1). In contrast, maximum stream concentrations when flow bypassed the buffer during smaller events were commonly 4000 to 7000 mg L(-1). Naturally occurring buffers represent an economical means of mitigating road-related impacts in upland basins in Southeast Asia, particularly if combined with measures limiting sediment and runoff production on contributing road sections.     

Metal Extraction from Road Sediment using Different Strength Reagents: Impact on Anthropogenic Contaminant Signals

Washoff of road deposited sediment into storm drainsystems is one of the major contributors to nonpoint sourcepollution in urban fluvial networks. These sediments contain avariety of potentially toxic organic and inorganic contaminants.Road sediment from 13 locations in an urban (non-industrialized)drainage basin, and soil from 10 background (control) locationswere collected to assess total and labile fractions of Al, Co,Cu, Fe, Mn, Ni, Pb and Zn. Four digestions, of varying strength,were used to assess contaminant levels, these included: a totalfour-acid digestion, a microwave-assisted digestion withconcentrated nitric acid (USEPA Method 3051), a 0.5 M `cold' HCl,and a 0.05 M EDTA (pH 7). Road sediment data indicate that Al,Co, Fe, Mn and Ni were primarily lithogenic in origin, while Cu,Pb and Zn showed very significant anthropogenic signals, mostprobably from vehicle-related sources. Median Pb concentrationenrichment ratios for the EDTA extraction were about 42,indicating an extreme anthropogenic signal. The weak extractants(HCl and EDTA) are considered in this study to be superior intheir ability to characterize the degree of anthropogeniccontamination and should be utilized more widely in environmentalcontaminant studies.     

Reserve design to optimize functional connectivity and animal density

Ecological distance-based spatial capture–recapture models (SCR) are a promising approach for simultaneously estimating animal density and connectivity, both of which affect spatial population processes and ultimately species persistence. We explored how SCR models can be integrated into reserve-design frameworks that explicitly acknowledge both the spatial distribution of individuals and their space use resulting from landscape structure. We formulated the design of wildlife reserves as a budget-constrained optimization problem and conducted a simulation to explore 3 different SCR-informed optimization objectives that prioritized different conservation goals by maximizing the number of protected individuals, reserve connectivity, and density-weighted connectivity. We also studied the effect on our 3 objectives of enforcing that the space-use requirements of individuals be met by the reserve for individuals to be considered conserved (referred to as home-range constraints). Maximizing local population density resulted in fragmented reserves that would likely not aid long-term population persistence, and maximizing the connectivity objective yielded reserves that protected the fewest individuals. However, maximizing density-weighted connectivity or preemptively imposing home-range constraints on reserve design yielded reserves of largely spatially compact sets of parcels covering high-density areas in the landscape with high functional connectivity between them. Our results quantify the extent to which reserve design is constrained by individual home-range requirements and highlight that accounting for individual space use in the objective and constraints can help in the design of reserves that balance abundance and connectivity in a biologically relevant manner.     

SURFACE WATER-ESKER RECHARGE STUDY EAST LANSING-MERIDIAN TOWNSHIP,MICHIGAN1

ABSTRACT: The East Lansing-Meridian Water and Sewer Authority studied a sand-gravel esker near the existing water treatment plant to determine its potential as an independent surface water supply. The nearby Red Cedar River was also investigated as a possible source of water for immediate treatment or for recharge of the esker. Although the bedrock aquifer (Grand River and Saginaw Formations) yields water adequate for the next 20 years, potential savings in treatment (hardness, iron) and pumping costs, estimated at $30,000 per year for present demand of 5 MGD, are attractive incentives for a surface water-esker recharge program. Operation savings would also be realized by constructing additional bedrock wells in new areas. The river-esker-recharge and new wellfield alternatives are compared for cost-effectiveness. Land costs make the recharge alternative more expensive. The land is undeveloped suburban property with potential for recreational use in conjunction with water supply. More places of outdoor retreat and aesthetics are needed in the Lansig Metropolitan area. A portion of the land costs would have to be borne by these or other interests for the river recharge scheme to be economically feasible.     

Adaptive host choice and avoidance of superparasitism in the spawning decisions of bitterling (Rhodeus sericeus)

Choice of a site for oviposition can have fitness consequences. We investigated the consequences of female oviposition decisions for offspring survival using the bitterling, Rhodeus sericeus, a freshwater fish that spawns inside living unionid mussels. A field survey of nine bitterling populations in the Czech Republic revealed a significantly lower rate of release of juvenile bitterling from Anodonta cygnea compared to three other mussel species. A field experiment demonstrated that female bitterling show highly significant preferences for spawning in A. anatina, Unio pictorum, and U. tumidus. Within a species, female bitterling avoided mussels containing high numbers of bitterling embryos. Mortality rates of bitterling embryos in mussels were strongly density dependent and the strength of density dependence varied significantly among mussel species. Female preferences for mussels matched survival rates of embryos within mussels and females distributed their eggs among mussels such that embryo mortalities conformed to the predictions of an ideal free distribution model. Thus, female oviposition choice is adaptive and minimizes individual embryo mortality. Received: 6 October 1999 / Received in revised form: 7 January 2000 / Accepted: 13 March 2000     

Racial mixing in South African honeybees: the effects of genotype mixing on reproductive traits of workers

To test the hypothesis that the honeybee hybrid zone in South Africa is a tension zone due to increased reproductive conflict in colonies that contain both Apis mellifera capensis and Apis mellifera scutellata worker genotypes, we constructed mixed subspecies and hybrid colonies via a combination of artificial and natural matings. We measured emergence weight, ovary activation, and the presence/absence of a spermatheca on workers of different genotypes. We show that the measured characteristics were all affected by genotype with some traits also affected by the social environment in which the worker was reared. Workers with both an A. m. capensis mother and father had the highest emergence weight. When workers had an A. m. capensis mother, paternity affected emergence weight with A. m. capensis fathers producing heavier workers. When the queen was A. m. scutellata, paternity had less effect on weight. Presence of spermatheca was highest in mixed colonies irrespective of maternity and colonies containing pure A. m. capensis workers only. Paternity had a significant effect on the presence of a spermatheca within mixed colonies, with workers that had an A. m. capensis father being more likely to possess a spermatheca. Rates of ovary activation were highest in colonies with an A. m. scutellata queen mated to drones of both genotypes, suggesting that mixed subspecies colonies likely suffer increased reproductive strife among workers. Our results provide support for the hypothesis that the South African honeybee hybrid zone is a tension zone arising from reduced fitness of genetically mixed colonies.