Biological phosphate uptake and release: effect of pH and magnesium ions.

Enhanced biological phosphorus removal (EBPR) is based on poly-phosphate accumulating organisms' (PAOs) unique features of "luxury" phosphate uptake during aerobic conditions and phosphate release in anaerobic conditions. It is believed that poly-phosphate accumulation is accompanied by the uptake and accumulation of potassium ions (K+) and magnesium ions (Mg2+). The release of phosphate under anaerobic conditions is also accompanied by the release of both cations. The objective of this research was to evaluate the effect of pH and Mg2+ on the biological phosphate uptake and release behavior of activated sludge mixed liquor during aeration and sedimentation. Research results indicate that Mg2+, supplied either by magnesium chloride (MgCl2) or magnesium hydroxide [Mg(OH)2], stimulated phosphate uptake during the aeration period, while pH increase, caused by the application of Mg(OH)2, enhanced phosphate release during the sedimentation period. It is also noted in our experiments with MgCl2 that Mg2+ slightly inhibited anaerobic phosphate release.     

Veterinary antimicrobials in feedlot manure: dissipation during composting and effects on composting processes

Composting of manure may lead to the degradation of veterinary antimicrobials, but it is largely unknown if the presence of antimicrobials affects the composting process. Open-air windrow composting of manure from beef cattle (Bos taurus) administered chlortetracycline, sulfamethazine, and tylosin was investigated in a 2-yr study. At windrow construction, chlortetracycline had extensively isomerized to iso-chlortetracycline. Sulfamethazine, tylosin, and iso-chlortetracycline dissipated by first-order kinetics, whereas the dissipation of enol/keto-chlortetracycline was better described by exponential equations. At the end of the composting period, proportions of antimicrobials remaining were as follows: iso-chlortetracycline (< 1%), chlortetracycline (1 to 4.5%), tylosin (6.3%), and sulfamethazine (6.8% [2005], 41% [2006]). Times for 50% dissipation (DT50) decreased in the order: tylosin (20.3 to 43.5 d) > iso-chlortetracycline (13.5 to 26.5 d) > enol/keto-chlortetracycline (5.5 to 9.8 d). The DT50 values for sulfamethazine varied from 26.8 d in 2005 to 237 d in 2006. Treatments with chlortetracycline showed significantly reduced temperature rises (10.1 to 11.0 degrees C) between Days 21 to 28 in 2006 compared with rises of 26.6 to 31.0 degrees C for control and tylosin treatments, suggesting an inhibition of microbial activity. During composting in 2005, manure from cattle administered chlortetracycline at 44 mg kg(-1) of feed lost significantly less dry matter, carbon, and nitrogen than manure from cattle fed 11 mg chlortetracycline kg(-1) of feed, implying that the higher level of chlortetracycline inhibited microbial decomposition of organic matter. The study shows that while composting leads to dissipation of antimicrobials, the microbially driven composting process may be inhibited by their presence.     

Population regulation by enemies of the grass Brachypodium sylvaticum: demography in native and invaded ranges

The enemy-release hypothesis (ERH) states that species become more successful in their introduced range than in their native range because they leave behind natural enemies in their native range and are thus "released" from enemy pressures in their introduced range. The ERH is popularly cited to explain the invasive properties of many species and is the underpinning of biological control. We tested the prediction that plant populations are more strongly regulated by natural enemies (herbivores and pathogens) in their native range than in their introduced range with enemy-removal experiments using pesticides. These experiments were replicated at multiple sites in both the native and invaded ranges of the grass Brachypodium sylvaticum. In support of the ERH, enemies consistently regulated populations in the native range. There were more tillers and more seeds produced in treated vs. untreated plots in the native range, and few seedlings survived in the native range. Contrary to the ERH, total measured leaf damage was similar in both ranges, though the enemies that caused it differed. There was more damage by generalist mollusks and pathogens in the native range, and more damage by generalist insect herbivores in the invaded range. Demographic analysis showed that population growth rates were lower in the native range than in the invaded range, and that sexually produced seedlings constituted a smaller fraction of the total in the native range. Our removal experiment showed that enemies regulate plant populations in their native range and suggest that generalist enemies, not just specialists, are important for population regulation.     

Monitoring microbes in the Great Lakes

The concentrations of Cu, Pb, Zn, Cd, and Ni were measured in surface and core sediments to determine their distribution characteristics and toxicity in the sediments of Lake Chaohu. The results revealed that metal concentrations in the surface sediments had a tendency to increase from the estuarine mouth to the lake center. The distribution characteristics of the five target metals were similar along the sediment profiles at each site. Principal component analysis revealed that all of the measured variables were loaded in the same component, indicating that there was a strong relationship among these measured variables, which was confirmed by the correlation analysis. Two sets of sediment quality guidelines (SQGs): simultaneously extracted metal (SEM) and acid volatile sulfides (AVS) models (including ∑SEM/AVS, ∑SEM-AVS, and ∑SEM-AVS/ f (oc)) and threshold effect level and probable effect level values were used to predict the sediment toxicity. Comparison of the results obtained using these two sets of SQGs revealed that only a small portion of the entire set was identical, while the majority of the results were different and sometimes completely contradictory. These contradictory results would cause a great deal of trouble for environment managers. More accurate and universal SQGs must be developed for environmental researchers and local environmental managers and regulators.     

Formerly utilized sites remedial action program “completed” sites: Lessons for long‐term stewardship

The Formerly Utilized Sites Remedial Action Program (FUSRAP) covers inactive commercial, federal, and university facilities that once supported activities of the Manhattan Project or Atomic Energy Commission. Current responsibilities, established by a Memorandum of Understanding (MOU), are split between the U.S. Department of Energy (US DOE) and the U.S. Army Corps of Engineers. The MOU distinguishes between facilities remediated before 1997 (“completed” sites) and those where remediation remained to be completed at that time. This article evaluates activities conducted at completed sites with regard to considerations for long‐term stewardship, which is defined by the US DOE as all activities necessary to protect human health and the environment after remediation is considered complete. Experience with these FUSRAP sites provides “lessons learned” for the requirements of satisfactory long‐term stewardship. © 2007 Wiley Periodicals, Inc.     

Effects of Long-Term Ungulate Exclusion and Recent Alien Species Control on the Preservation and Restoration of a Hawaiian Tropical Dry Forest

Abstract: Although the destruction of tropical rain forests receives much attention, tropical dry forests are in general far more threatened and endangered. Eliminating grazing ungulates is often considered a key first step toward protecting these ecosystems, but few studies have investigated the long-term effects of this technique. We examined the effects of ungulate exclusion from a 2.3-ha native dry-forest preserve on the island of Hawaii by comparing its present flora to the flora of an adjacent area subjected to continuous grazing since the preserve was fenced over 40 years ago. Relative to this adjacent area, the fenced preserve contained a more diverse flora with substantially greater coverage of native overstory and understory species. Until recently, however, regeneration of native canopy trees within the preserve appears to have been thwarted by a dominant herbaceous cover of alien fountain grass (   Pennisetum setaceum ) and predation by alien rodent species. Our results indicate that although ungulate exclusion may be a necessary and critical first step, it is not sufficient to adequately preserve and maintain Hawaii's remaining tropical dry forest remnants. Our recent efforts to control the dominant alien species within the fenced preserve suggest that this practice may facilitate both the regeneration of native species and the colonization and potential invasion of new alien plants. Comparisons of seedlings of the dominant native canopy tree Diospyros sandwicensis growing in sites both dominated by and free of fountain grass suggested that fountain grass inhibits Diospyros seedling growth and photosynthesis but may increase survival if seedlings are protected from ungulates.