Ecology and Conservation of the Endangered American Burying Beetle (Nicrophorus americanus)

Field studies were conducted on the western population of the endangered American burying beetle (Nicrophorus americanus) in Oklahoma and Arkansas to determine its habitat affinities. A common cause of declining populations is some specialized adaptation that makes it difficult to respond to a rapidly changing habitat. We evaluated the hypothesis that N. americanus is a habitat specialist in its search for food, preferring mature forests with deep, humic soils. This hypothesis was rejected. Based on comparisons of niche breadth among syntopic congeners and niche overlap, N. americanus is relatively generalized in its use of a range of habitats when searching for food. It is likely that the generalist nature and the endangered status of N. americanus both derive from the fact that it is the largest member of its guild. In comparison to smaller species, N. americanus breeds on larger carcasses, which are more unpredictable in space and time. It is likely, therefore, that N. americanus must search over a larger area and greater diversity of habitats than its smaller congeners.     

Prenatal diagnosis of a homologous Robertsonian translocation involving chromosome 15

We report the prenatal diagnosis of a fetus with a de novo Robertsonian translocation: 45,XY,der(15;15)(q10;q10). Although Robertsonian translocations are common chromosomal rearrangements, those involving homologous chromosomes are infrequent. Since chromosome 15 is imprinted, uniparental disomy (UPD) is a concern when chromosomal rearrangements involving chromosome 15 are identified. In the present case, UPD studies showed normal biparental inheritance. In contrast to the fact that most homologous acrocentric rearrangements are isochromosomes, these results indicate postzygotic formation of a Robertsonian translocation between biparentally inherited chromosomes 15. Copyright © 2001 John Wiley & Sons, Ltd.     

Introduction History and Invasion Patterns of Ammophila arenaria on the North Coast of California

European beachgrass ( Ammophila arenaria [L] Link), introduced to stabilize sand, is fully naturalized in central and northern California and has supplanted populations of native dune plants in many areas, including the North Spit of Humboldt Bay. We interpreted air photos of the North Spit for the presence of Ammophila arenaria at three points in time: 1939/1942, 1962, and 1989. To quantify the spread and to detect invasion patterns of Ammophila , we then compiled maps using a geographic information system. We documented introduction dates and locations to improve the accuracy of our photo interpretation. Interpretation of the three photo series revealed invasion and expansion of Ammophila in both foredunes and inland dunes. The most dramatic increase in cover was found in the foredunes, whereas documented and presumed plantings were found mostly on inland dunes. Adjusting for intentional eradication, Ammophila cover on the North Spit was found to have increased between 1939 and 1989 by 574%. The square root of the area occupied by Ammophila on the North Spit increased linearly with time, conforming to biological invasion theory.     

Variations in Densities of Invertebrate Benthos of the Clyde Estuary Tidal Flats

The Clyde Estuary is recognised as an important area for overwintering flocks of ducks and waders (Smyth et al., 1974. Here we draw attention to some of the spatial and temporal variations in the invertebrate populations on which these birds feed. Smyth et al. (1977) discuss possible relationships between the bird populations and their invertebrate prey. A 12-month survey, 1976-77, provides the main information on numbers of feeding birds (Halliday, 1978), complemented by sampling over the estuarine flats for invertebrate prey species and for chemical environmental factors: salinity, organic carbon, organic nitrogen, dissolved oxygen, as well as sediment grades. Although there is no constant monitoring shceme for the estuarine flats, a series of surveys provide data over the period 1973-1981.     

Barnacle larvae actively select flow environments supporting post-settlement growth and survival

Many marine dispersive propagules select specific settlement sites based on a range of environmental cues. However, the link between larval choice and post-settlement growth and survival is still poorly understood. Here we show that cypris larvae of the barnacle Balanus improvisus actively reject surfaces exposed to local flow speeds exceeding 5-10 cm/s. Field experiments show that post-settlement growth and survival decline in freestream flows above 15 cm/s. Moreover, studies in flume flow at local speeds exceeding 10 cm/s reveal that early juveniles show reduced feeding rates caused by deformation of the cirral fan, reduced retention efficiency, and a decrease in time spent feeding. We conclude that cypris larvae actively reject flow environments that will be suboptimal for suspension feeding in the early post-settlement phase. Our study suggests that larval choice can be adaptively connected to a specific part of the life cycle, in this case the very sensitive time after metamorphosis.     

Application of various mathematical models to data from the uptake of methyl mercury in bluegill sunfish (Lepomis macrochirus)

Evaluated and compared are the results of various mathematical models to data from the uptake of methyl mercury in bluegill sunfish (Lepomis macrochirus). Data were obtained from the direct uptake of methyl mercury from water in bluegill at 9°C and at a CH₃HgCl concentration of 0.2 ppb. The models considered are: (1) linear uptake relationship; (2) first-order kinetics, one-compartment or single-exponential model; (3) combination of first-order kinetics and the linear uptake relationship, designated as slope-exponential model; (4) two-compartment or double-exponential model; (5) three-compartment model, including a storage compartment for the build up of contaminant, designated as storage model; (6) three-compartment model, allowing two routes of elimination, designated the “Y” model; (7) an empirical uptake relationship having the form of a rectangular hyperbola.A comparison of the nonlinear models showed that the empirical model had fewer convergence problems in obtaining parameter estimates and its parameter values had less variation. The best fit was made by the “Y” model, the empirical model gave one of the smaller values of the residual mean squares, and other nonlinear models had computational convergence difficulties. The lack of computational problems and the comparitively small residual mean squares resulted in the selection of and the preference for the empirical model for use in describing the individual and interactive effects of temperature and methyl mercury concentration on the direct uptake of methyl mercury from water by bluegill.     

A new satellite-based methodology for continental-scale disturbance detection.

The timing, location, and magnitude of major disturbance events are currently major uncertainties in the global carbon cycle. Accurate information on the location, spatial extent, and duration of disturbance at the continental scale is needed to evaluate the ecosystem impacts of land cover changes due to wildfire, insect epidemics, flooding, climate change, and human-triggered land use. This paper describes an algorithm developed to serve as an automated, economical, systematic disturbance detection index for global application using Moderate Resolution Imaging Spectroradiometer (MODIS)/Aqua Land Surface Temperature (LST) and Terra/MODIS Enhanced Vegetation Index (EVI) data from 2003 to 2004. The algorithm is based on the consistent radiometric relationship between LST and EVI computed on a pixel-by-pixel basis. We used annual maximum composite LST data to detect fundamental changes in land-surface energy partitioning, while avoiding the high natural variability associated with tracking LST at daily, weekly, or seasonal time frames. Verification of potential disturbance events from our algorithm was carried out by demonstration of close association with independently confirmed, well-documented historical wildfire events throughout the study domain. We also examined the response of the disturbance index to irrigation by comparing a heavily irrigated poplar tree farm to the adjacent semiarid vegetation. Anomalous disturbance results were further examined by association with precipitation variability across areas of the study domain known for large interannual vegetation variability. The results illustrate that our algorithm is capable of detecting the location and spatial extent of wildfire with precision, is sensitive to the incremental process of recovery of disturbed landscapes, and shows strong sensitivity to irrigation. Disturbance detection in areas with high interannual variability of precipitation will benefit from a multiyear data set to better separate natural variability from true disturbance.     

Biological solids reduction using the Cannibal process.

A laboratory study of the Cannibal process was undertaken to determine if the Cannibal system would generate less sludge compared with a conventional activated sludge system. Side-by-side sequencing batch reactors were operated--one using the Cannibal configuration and the other as conventional activated sludge. It was found that the Cannibal process generated 60% less solids than the conventional activated sludge system, without any negative effect on the effluent quality or the settling characteristics of the activated sludge. The oxygen uptake rate for the centrate from the Cannibal bioreactor showed that readily biodegradable organic matter was released from the recycled biomass in the Cannibal bioreactor. It is proposed that the mechanism for reduced solids from the Cannibal system is that, in the Cannibal bioreactor, iron is reduced, releasing iron-bound organic material into solution. When the Cannibal biomass is recirculated back to the aeration basin, the released organic material is rapidly degraded.     

Trends and sources of particulate matter in the Superstition Wilderness using air trajectory and aerosol cluster analysis

Ambient aerosols adversely affect human health and visibility and impact climate. Identification of sources of particulate matter and its precursors is necessary for developing control strategies. The goal of this research is to utilize long-term speciated particulate matter data and back-trajectory cluster analyses to determine trends and sources of particulate matter in the Superstition Wilderness, a rural area east of Phoenix, Arizona. Twenty-four hour back-trajectories were calculated for every hour of every 24-h particulate matter sample obtained by IMPROVE from 1991 to 2004. Days that included back-trajectories with considerable spatial variance were excluded from further analyses. To minimize uncertainties inherent in single trajectories, all calculated trajectories for each sampling day were averaged to represent the air mass sampled during that day. Cluster analysis of trajectories identified four unique regions, including a region with Phoenix, a region with copper smelters, and one with coal-fired power plants. Yearly averages of sulfate, nitrate, soil, and carbon concentrations were calculated for each region. Statistically significant trends in species concentrations by region and independent of region and differences in concentrations between regions were examined.Sulfate concentrations from the region with smelters were higher than other regions but decreased during the study period. Emissions data from the smelters indicate that much of the sulfate from the region was due to the smelters. The overall 2.2% year⁻¹ decrease in sulfate concentrations at TNM is likely due to decreased emissions from the copper smelters. A 3.6% year⁻¹ increase in nitrate concentrations was driven largely by increasing NO_x concentrations from Phoenix and to a lesser extent the region southwest of the site which includes Tucson and suburban/urban areas between Phoenix and Tucson. Soil concentrations were higher from regions with deserts than the region without desert. This method could not identify trends or source regions of carbonaceous aerosols at this site.