Laying the foundation for a comprehensive program of restoration for wildlife habitat in a riparian floodplain

We analyzed the past and current distribution and abundance of vegetation and wildlife to develop a wildlife habitat restoration plan for the Sweetwater Regional Park, San Diego County, California. Overall, there has been a substantial loss of native amphibians and reptiles, including four amphibians, three lizards, and 11 snake species. The small-mammal community was depauperate and dominated by the exotic house mouse (Mus musculus) and the native western harvest mouse (Reithrodontomys megalotis). It appeared that either house mice are exerting a negative influence on most native species or that they are responding positively to habitat degradation. There has apparently been a net loss of 13 mammal species, including nine insectivores and rodents, a rabbit, and three large mammals. Willow (Salix) cover and density and cottonwoods (Populus fremontii) had the highest number of positive correlations with bird abundance. There has been an overall net loss of 12 breeding bird species; this includes an absolute loss of 18 species and a gain of six species. A restoration plan is described that provides for creation and maintenance of willow riparian, riparian woodland, and coastal sage scrub vegetation types; guides for separation of human activities and wildlife habitats; and management of feral and exotic species of plants and animals.     

Understanding the Large‐Scale Influence of Levees on Floodplain Connectivity Using a Hydrogeomorphic Approach

The widespread construction of levees has reduced river–floodplain connectivity and altered associated fluvial processes in many river systems. Despite the recognition that levees can alter floodplain connectivity, few studies have examined the role of levees in reducing floodplain areas at large watershed scales. This paper explores the application of a hydrogeomorphic floodplain inundation model in the Wabash Basin, located in the Midwestern United States, to assess changes in floodplain area in levee‐protected areas. We evaluate 10‐ and 30‐m topographic resolutions and spatially examine the influence of levees on floodplain area in relation to river network attributes. Generally, floodplains in levee‐protected areas were influenced by topographic resolution, stream order, and elevation details of levees found in topography datasets. We show, when compared to Federal Emergency Management Agency maps, our approach underpredicts floodplain area when using 10‐m resolution topography data but only slightly overpredicts when using 30‐m resolution data. After removing details of levees from topography data, we found changes in floodplain area varied spatially, but basin‐aggregate results changed little compared to topography datasets that contain levees, though larger floodplain areas were produced in some regions where levees were removed. This work contributes to a growing research emphasis on using hydrogeomorphic floodplain models to understand floodplain disconnectivity.     

Use of an inert radioactive particle for measuring particle accumulation by filter-feeding bivalve molluscs

Because the rate of microbial degradation differs for the various sources contributing to the detrital pool in marine systems, their availability to detritivores might also vary. Carbon-14 tracer experiments were used to compare differences in the oxidation and net incorporation by the polychaete Capitella capitata of a nitrogenrich, easily-decomposable detritus derived from the red macrophytic algae Gracilaria sp. versus a nitrogen-poor, decay-resistant detritus derived from the eelgrass Zostera marina. The net incorporation of Gracilaria sp. detritus by C. capitata reached a maximum (91 g dry weight of detritus/mg dry weight of worm/day) after only 14 days of decomposition, whereas that of z. marina detritus equaled this level after 30 days of aging, but continued to increase to 375 g at 180 days. The oxidation rate of Gracilaria sp. detritus was consistently higher (peak of 61 mg dry weight of detritus/day at 30 day-aging) than z. marina detritus, which reached this level only after 180 days of aging. The presence or absence of C. capitata did not significantly alter the oxidation rate. The above difference might be attributed to a rapid exploitation and mineralization by bacteria of the more available Gracilaria sp. detritus, but a slow, controlled utilization by the microbes of the less available Z. marina detritus, especially during the early stage of decomposition. This would allow maximum exploitation of the substrate by macroconsumers, resulting in more of the detrital resource being tied up in detritivore biomass rather than being rapidly mineralized to CO₂. Difference in the length of aging at which various detrital sources become available to detritivores could result in a temporal partitioning of food resources and should be considered in attempting to understand the dynamics of detrital-based food chains.     

Metal diffusion properties of a Nafion-coated porous membrane in an aquatic passive sampler system

A cellulose acetate membrane, positioned in a passive sampler system, was coated with the perfluorinated polymer Nafion. Aqueous metal transport through the membrane and the Nafion film was investigated. The Nafion-coated membrane prevents the transport of metals bound to natural organic material to the receiving phase in the passive sampler, while copper associated with small synthetic ligands pass through the Nafion film. Increasing thickness of the Nafion film decreases the metal uptake rate to the receiving phase in the passive sampler and increases the response time. A decreased response time for the passive sampler would provide a better estimation of rapid changes in concentration, particularly for dynamic aquatic systems such as urban runoff. Limited biofouling protection with the Nafion coating was demonstrated by growth inhibition of natural periphyton communities on glass surfaces.     

Rapid measurement of indoor mass-transfer coefficients

Indoor air pollutant concentrations can be influenced by how rapidly species are transported to and from surfaces. Consequently, a greater understanding of indoor transport phenomena to surfaces improves estimates of human exposure to indoor air pollutants. Here, we introduce two methods of rapidly and directly measuring species fluxes at indoor surfaces, allowing us to evaluate the transport-limited deposition velocity, v_t (a mass-transfer coefficient). The deposition velocity sensor (DeVS) method employs a small microbalance coated with a pure hydrocarbon, preferably octadecane. We quantify flux (or evaporation rate) of the hydrocarbon into a room by observing the rate of mass loss on the microbalance. The transport-limited deposition velocity, v_t,octadecane, is then obtained by combining the flux with the vapor pressure of the hydrocarbon. Simultaneously, v_t,ozone is quantified using the deposition velocity of ozone (DeVO) method, which acts as a standard to calibrate and evaluate DeVS. Specifically, DeVO evaluates ozone transport to surfaces by quantifying the conversion by ozone of nitrite to nitrate on a glass fiber filter. Simultaneous laboratory chamber experiments demonstrates that v_t for octadecane and ozone are strongly correlated, with the values for ozone 1.5 times greater than that for octadecane. In an office experiments, the DeVS method responds within minutes to step changes in conditions such as occupancy, activities and ventilation. At present, the results are in order-of-magnitude agreement with predicted indoor mass-transfer coefficients.     

Animal Burrowing Attributes Affecting Hazardous Waste Management

/ Animal burrowing is critical to the formation of soils and contributes to the interface between geological materials and organic life. It also influences the management of hazardous materials at nuclear waste facilities and elsewhere. For example, residues and waste products from the production of nuclear weapons are released onto the ground surface and within engineered burial structures. Soil bioturbation has exposed radionuclides and other hazardous materials to wind and rain, thereby risking inhalation and injury to humans and wildlife on and off site. Soil bioturbation can expand soil depths and spatial distributions of the source term of hazardous waste, potentially increasing chronic exposures to wildlife and humans over the long term. Ample evidence indicates that some of the large quantities of hazardous materials around the world have been released from soil repositories, where they have also contaminated and harmed biota. Key burrowing parameters influencing these outcomes include the catalog of resident species, and their abundance, typical burrow volumes (void space created by soil displacement), burrow depth profiles, maximum depth of excavation, constituents and structural qualities of excavated soil mounds, and proportion of the ground covered by excavated soil. Other important parameters include rate of mound construction, depth of den chambers, and volume of burrow backfill. Soil bioturbation compromised the integrity of some hazardous waste management systems using soil, but the environmental impact remains largely unknown. Designers and operators of waste management facilities, as well as risk assessors, need to understand how burrowing animals influence hazardous waste storage.KEY WORDS: Burrowing; Environmental impact; Radioactivity; Risk; Soil bioturbation; Hazardous waste     

Organochlorine contaminants in the estuarine and coastal marine environments of the Fiji Islands

No information has been published on the presence of organochlorine pesticides and polychlorinated biphenyls in the Fiji Islands. This paper reports the first data on the concentration of a range of organochlorine compounds in sediments and shellfish in the estuarine and coastal marine environment around Fiji. Twenty-three sediment and two shellfish samples were analysed for 22 pesticides and related residues, and PCBs. While a significant number of organochlorines (20 pesticide related species and PCBs) was detected, the concentrations were generally very low (< 10 ng g), indicative of a relatively 'less contaminated' marine environment. Relatively high concentrations were observed only near the two major ports (Suva and Lautoka), with Suva harbour samples having the largest number of detectable species and the largest total concentrations of organochlorines (up to 91 ng g). No PCBs were detected in areas away from major industrial centres. The variations in the concentrations found, and the possible sources and movement of the organochlorine contaminants are discussed.     

Predictive value of amniotic acetylcholinesterase analysis in the diagnosis of fetal abnormality in 3700 pregnancies

The value of acetylcholinesterase (AChE) analysis as an adjunctive test to amniotic alpha fetoprotein (amAFP) for the diagnosis of fetal abnormality has been investigated in a series of 3785 amniotic fluid samples. Quantitative analysis of AChE performed retrospectively on a selected group of 541 amniotic fluid samples failed to discriminate between normal and open neural tube defect pregnancies. Qualitative analysis of AChE by polyacrylamide gel (PAG) electrophoresis in the same series of 541 fluids correctly identified 251 of the 255 pregnancies with open neural tube defect and 29 of the 31 pregnancies with false positive amAFP results. The failure of the test to diagnose 4 cases of open neural tube defect was probably attributable to the age and condition of the stored AF samples. Routine diagnostic testing of AChE isoenzymes in a further 3244 AF samples successfully identified all 170 cases of open neural tube defect and 20 cases with other fetal defects. Thirteen fluids gave false positive AChE results (0.4 per cent) compared to 59 of the series in which there were false positive amAFP results (1.8 per cent). Six of the 13 false positive AChE cases had AChE bands of low intensity which would not be regarded as diagnostic of fetal abnormality, and in five the AChE band may have been the result of significant blood contamination. False positive AChE results contributed to the decision to abort three apparently normal fetuses, but a normal AChE result undoubtedly helped to save a number of pregnancies with false positive amAFP results. Our experience suggests that repeating the amniocentesis may help in resolving the rare diagnostic difficulty of a positive AChE result with or without an elevated amAFP in the absence of ultrasound evidence of fetal abnormality, particularly where there is blood contamination of the amniotic fluid sample.     

Towards a model of acidification effects on waterfowl in Eastern Canada

Data from 212 lakes in central Ontario were used to examine the relationship between presence of breeding waterfowl and loons and the following lake characteristics: pH, presence of fish, lake area, dissolved organic carbon (DOC) and total phosphorus (TP) concentration. In univariate analyses, the two fish-eating species preferred large, high pH lakes with fish, while insectivorous species showed little consistent pattern of lake association. Logistic regression analyses confirmed that large lake size and presence of fish were important determinants of presence of piscivores, though the residual effect of pH differed between the two species. Broods of three of the four insectivorous species avoided lakes with fish, and independently showed a positive response to pH. By calculating the probability that fish will be present on a lake of given area and pH, it is possible to estimate the net effect of pH change on these waterfowl. Relationships such as those presented here can, with some assumptions, be linked to models of lake acidification to estimate response of waterfowl to predicted changes in acidic deposition.     

Are lower-latitude plants better defended? Palatability of freshwater macrophytes

Increased herbivory at lower latitudes is hypothesized to select for more effective plant defenses. Feeding assays with seaweeds and salt marsh plants support this hypothesis, with low-latitude plants experiencing greater damage in the field and being less palatable than higher-latitude plants. We tested this hypothesis for freshwater macrophytes because they offered an independent plant lineage and habitat type for testing this general hypothesis and because the patchiness of consumer occupancy across isolated water bodies might produce local variance in herbivory that would override geographic variance and produce different results for this habitat type. When we fed eight congeneric pairs of live plants from four sites in Indiana vs. four sites in South Florida (-215 and 0 frost days/yr respectively) to three species of crayfishes and one species of snail, three of the four herbivores significantly preferred high-latitude to low-latitude plants. For two crayfishes that differed in feeding on live plants (one favoring high-latitude plants and one not), we retested feeding using foods composed of freeze-dried and finely ground plants, thus removing structural characteristics while retaining most chemical/nutritional traits. In this assay, both herbivores strongly preferred high-latitude plants, suggesting that lower-latitude plants had been selected for more deterrent chemical traits. When we collected 22 pairs of congeneric plants from 9 sites throughout Indiana vs. 13 sites in Central Florida (-215 and -95 frost days/yr respectively) and tested these in feeding assays with three crayfishes using dried, ground, and reconstituted plant material, we found a significant effect of latitude for only one of three species of herbivore. Overall, our results suggest a preference for high-latitude plants, but the strength of this relationship varied considerably across small scales of latitude that differed considerably in numbers of frost-free days. The difference in results suggests that large changes in frost frequency over small spatial scales may affect selection for plant defenses, that local variance in herbivory overrode differential selection at geographic scales, or that these possibilities interact when durations of cold weather periodically exclude herbivores from shallower habitats, producing heterogeneous selection for defenses at small spatial scales.