Effect of Cell-to-matrix Ratio in Polyvinyl Alcohol Immobilized Pure and Mixed Cultures on Atrazine Degradation

Atrazine biodegradation by immobilized pure and mixed cultures was examined. A pure atrazine-degrading culture, Agrobacterium radiobacter J14a (J14a), and a mixed culture (MC), isolated from an atrazine-contaminated crop field, were immobilized using phosphorylated-polyvinyl alcohol (PPVA). An existing cell immobilization procedure was modified to enhance PPVA matrix stability. The results showed that the matrices remained mechanically and chemically stable after shaking with glass beads over 15 days under various salt solutions and pH values. The immobilization process had a slight effect on cell viability. With the aid of scanning electron microscopy, a suitable microstructure of PPVA matrices for cell entrapment was observed. There were two porous layers of spherical gel matrices, the outside having an encapsulation property and the inside containing numerous pores for bacteria to occupy. J14a and MC were immobilized at three cell-to-matrix ratios of 3.5, 6.7, and 20 mg dry cells/mL matrix. The atrazine biodegradation tests were conducted in an aerobic batch system, which was inoculated with cells at 2,000 mg/L. The tests were also conducted using free (non-immobilized) J14a and MC for comparative purpose. The cell-to-matrix ratio of 3.5 mg/mL provided the highest atrazine removal efficiency of 40–50% in 120 h for both J14a and MC. The free cell systems, for both cultures, presented much lower atrazine removal efficiencies compared to the immobilized cell systems at the same level of inoculation.     

Biodegradability of Poly (lactic acid), Preparation and Characterization of PLA/Gum Arabic Blends

In this study, the biodegradation of PLA films using microorganisms from Lake Bogoria (Kenya) were investigated. The biodegradation tests done using certain strains of thermophilic bacteria showed faster biodegradation rates and demonstrated temperature dependency. The biodegradation of the PLA films was studied using Gel Permeation Chromatography (GPC) and light microscopy. The biodegradation of PLA was demonstrated by decrease in molecular weight. The preparation and characterization of PLA/Gum Arabic blends were also investigated using DSC, TGA, TMA and NMR. In summary, the results obtained in this research show that PLA films undergo fast biodegradation using thermophiles isolated from Lake Bogoria. The PLA/GA blends studies show it is possible to prepare films of varying hydrophobic–hydrophilic properties for various applications.     

Avian Conservation under the Endangered Species Act: Expenditures versus Recovery Priorities

Abstract: Budget constraints require the U.S. Fish and Wildlife Service to prioritize species for recovery spending. Each listed species is ranked according to the degree of threat it faces, its recovery potential, and its taxonomic distinctness. We analyzed state and federal government expenditures for recovery of threatened and endangered birds ( n = 85 species) from 1992 to 1995 to determine if the priority system was being followed. Although recovery spending correlated with priority rank, priority rank explained <5% of the variation in spending. A small number of the same moderately ranked species dominated expenditures each year (41–79% of total annual budgets). Species with wide distributions, high recovery potential, and captive breeding programs received the most funding, and more funding than their priority ranks dictated. Island species received significantly less funding than expected based on priority rank. Twelve species, 10 of which resided on islands, received <$5000 at least once from 1992 to 1995. Recovery spending was unrelated to degree of threat, taxonomic distinctness, and migratory status. There also was no relationship between land-purchase expenditures and priority ranks. To improve the relationship between recovery spending on threatened and endangered birds and their priority rank, significant changes need to be made within the private sector ( less litigation and special-interest lobbying  ), U.S. Congress (increased budget and reduced earmarking  ), and the U.S. Fish and Wildlife Service (restructuring of regional offices and increased accountability).     

Ecology of subtropical hermit crabs in S.W. Madagascar: cluster structure and function

The Madagascar coast (both) has a higher density and diversity of hermit crabs than is known from any other locality in the western Indian Ocean. Of the 20 species occurring at Anakao (S.W. Madagascar), 11 aggregated into clusters, including all but one of the species above the subtidal zone. The mean number of hermit crabs and species in clusters varied with several spatial parameters and time. Over 80% of the community clustered in certain habitats in particular tidal zones, whilst as low as 3% clustered in others. The highest intensity of clustering with shore zone was coincident with peak numbers of hermit crabs. The initiation and duration of clusters of hermit crabs above the eulittoral was driven by circadian rhythms, whilst those in the eulittoral were governed by tidal state. Clusters above and below the eulittoral were longer in duration, and those in the subtidal were more temporally variable than those above it. Certain pairs of species showed positive correlations of occurrence and (more rarely) of abundance, and all the correlations (of occurrence) of one, Clibanarius eurysternus, were negative. Positive correlations of occurrence were related to the degree of shell-use commonality between species pairs. Eulittoral species clustered with other individuals of approximately similar size and exchanged shells upon cluster disintegration. There was evidence of a dehydration-reduction function to shell clustering in addition to shell-exchange facilitation. The highly variable species-specific strategies of clustering may be important in alleviating both intra- and interspecific competition in assemblages of similar and highly abundant species.     

A moving target—incorporating knowledge of the spatial ecology of fish into the assessment and management of freshwater fish populations

Freshwater fish move vertically and horizontally through the aquatic landscape for a variety of reasons, such as to find and exploit patchy resources or to locate essential habitats (e.g., for spawning). Inherent challenges exist with the assessment of fish populations because they are moving targets. We submit that quantifying and describing the spatial ecology of fish and their habitat is an important component of freshwater fishery assessment and management. With a growing number of tools available for studying the spatial ecology of fishes (e.g., telemetry, population genetics, hydroacoustics, otolith microchemistry, stable isotope analysis), new knowledge can now be generated and incorporated into biological assessment and fishery management. For example, knowing when, where, and how to deploy assessment gears is essential to inform, refine, or calibrate assessment protocols. Such information is also useful for quantifying or avoiding bycatch of imperiled species. Knowledge of habitat connectivity and usage can identify critically important migration corridors and habitats and can be used to improve our understanding of variables that influence spatial structuring of fish populations. Similarly, demographic processes are partly driven by the behavior of fish and mediated by environmental drivers. Information on these processes is critical to the development and application of realistic population dynamics models. Collectively, biological assessment, when informed by knowledge of spatial ecology, can provide managers with the ability to understand how and when fish and their habitats may be exposed to different threats. Naturally, this knowledge helps to better evaluate or develop strategies to protect the long-term viability of fishery production. Failure to understand the spatial ecology of fishes and to incorporate spatiotemporal data can bias population assessments and forecasts and potentially lead to ineffective or counterproductive management actions.     

Effects of pig manure containing copper and zinc on microbial community assessed via phospholipids in soils

Pig manure (PM) is widely used as an organic fertilizer to increase yields of crops. Excessive application of compost containing relatively great concentrations of copper (Cu) and zinc (Zn) can change soil quality. To clarify the effects of different rates of application and to determine the optimal rate of fertilization, PM containing 1,115 mg Cu kg^?1, dry mass (dm) and 1,497 mg Zn kg^?1, dm was applied to alkaline soil at rates of 0, 11, 22, 44, 88, and 222 g PM kg^?1, dm. Phospholipid fatty acids (PLFAs) were used to assess soil microbial community composition. Application of PM resulted in greater concentrations of total nitrogen (TN), NH₄ ⁺-N, NO₃ ^?-N, total carbon (TC), soil organic matter (SOM) but lesser pH values. Soils with application rates of 88–222 g PM kg^?1, dm had concentrations of total and EDTA-extractable Cu and Zn significantly greater than those in soil without PM, and concentrations of T-Cu and T-Zn in these amended soils exceeded maximum limits set by standards in china. Except in the soil with a rate of 11 g PM kg^?1, dm, total bacterial and fungal PLFAs were directly proportional to rate of application of PM. Biomasses of bacteria and fungi were significantly greater in soils with application rates of 44–222 g PM kg^?1, dm than in the soil without PM. SOM, TC and EDTA-Zn had the most direct influence on soil microbial communities. To improve fertility of soils and maintain quality of soil, rate of application should be 22–44 g PM kg^?1 dm, soil containing Cu and Zn.     

A landscape-based reconnaissance survey of estrogenic activity in streams of the upper Potomac,upper James,and Shenandoah Rivers,USA

Endocrine-disrupting compounds (EDCs) are becoming of increasing concern in waterways of the USA and worldwide. What remains poorly understood, however, is how prevalent these emerging contaminants are in the environment and what methods are best able to determine landscape sources of EDCs. We describe the development of a spatially structured sampling design and a reconnaissance survey of estrogenic activity along gradients of land use within sub-watersheds. We present this example as a useful approach for state and federal agencies with an interest in identifying locations potentially impacted by EDCs that warrant more intensive, focused research. Our study confirms the importance of agricultural activities on levels of a measured estrogenic equivalent (E2Eq) and also highlights the importance of other potential sources of E2Eq in areas where intensive agriculture is not the dominant land use. Through application of readily available geographic information system (GIS) data, coupled with spatial statistical analysis, we demonstrate the correlation of specific land use types to levels of estrogenic activity across a large area in a consistent and unbiased manner.     

Reproductive endocrine disruption in smallmouth bass (Micropterus dolomieu) in the Potomac River basin: spatial and temporal comparisons of biological effects

A high prevalence of intersex or testicular oocytes (TO) in male smallmouth bass within the Potomac River drainage has raised concerns as to the health of the river. Studies were conducted to document biomarker responses both temporally and spatially to better understand the influence of normal physiological cycles, as well as water quality and land-use influences. Smallmouth bass were collected over a 2-year period from three tributaries of the Potomac River: the Shenandoah River, the South Branch Potomac and Conococheague Creek, and an out-of-basin reference site on the Gauley River. The prevalence of TO varied seasonally with the lowest prevalence observed in July, post-spawn. Reproductive maturity and/or lack of spawning the previous spring, as well as land-use practices such as application of manure and pesticides, may influence the seasonal observations. Annual, seasonal, and site differences were also observed in the percentage of males with measurable concentrations of plasma vitellogenin, mean concentration of plasma vitellogenin in females, and plasma concentrations of 17β-estradiol and testosterone in both sexes. Bass collected in the South Branch Potomac (moderate to high prevalence of TO) had less sperm per testes mass with a lower percentage of those sperm being motile when compared to those from the Gauley River (low prevalence of TO). An inverse relationship was noted between TO severity and sperm motility. An association between TO severity and wastewater treatment plant flow, percent of agriculture, total number of animal feeding operations, the number of poultry houses, and animal density within the catchment was observed.