Nutrient subsidies to belowground microbes impact aboveground food web interactions

Historically, terrestrial food web theory has been compartmentalized into interactions among aboveground or belowground communities. In this study we took a more synthetic approach to understanding food web interactions by simultaneously examining four trophic levels and investigating how nutrient (nitrogen and carbon) and detrital subsidies impact the ability of the belowground microbial community to alter the abundance of aboveground arthropods (herbivores and predators) associated with the intertidal cord grass Spartina alterniflora. We manipulated carbon, nitrogen, and detrital resources in a field experiment and measured decomposition rate, soil nitrogen pools, plant biomass and quality, herbivore density, and arthropod predator abundance. Because carbon subsidies impact plant growth only indirectly (microbial pathways), whereas nitrogen additions both directly (plant uptake) and indirectly (microbial pathways) impact plant primary productivity, we were able to assess the effect of both belowground soil microbes and nutrient availability on aboveground herbivores and their predators. Herbivore density in the field was suppressed by carbon supplements. Carbon addition altered soil microbial dynamics (net potential ammonification, litter decomposition rate, DON [dissolved organic N] concentration), which limited inorganic soil nitrogen availability and reduced plant size as well as predator abundance. Nitrogen addition enhanced herbivore density by increasing plant size and quality directly by increasing inorganic soil nitrogen pools, and indirectly by enhancing microbial nitrification. Detritus adversely affected aboveground herbivores mainly by promoting predator aggregation. To date, the effects of carbon and nitrogen subsidies on salt marshes have been examined as isolated effects on either the aboveground or the belowground community. Our results emphasize the importance of directly addressing the soil microbial community as a factor that influences aboveground food web structure by affecting plant size and aboveground plant nitrogen.     

Interaction effects of metals and salinity on biodegradation of a complex hydrocarbon waste

The presence of high levels of salts because of produced brine water disposal at flare pits and the presence of metals at sufficient concentrations to impact microbial activity are of concern to bioremediation of flare pit waste in the upstream oil and gas industry. Two slurry-phase biotreatment experiments based on three-level factorial statistical experimental design were conducted with a flare pit waste. The experiments separately studied the primary effect of cadmium [Cd(II)] and interaction effect between Cd(II) and salinity and the primary effect of zinc [Zn(II)] and interaction effect between Zn(II) and salinity on hydrocarbon biodegradation. The results showed 42-52.5% hydrocarbon removal in slurries spiked with Cd and 47-62.5% in the slurries spiked with Zn. The analysis of variance showed that the primary effects of Cd and Cd-salinity interaction were statistically significant on hydrocarbon degradation. The primary effects of Zn and the Zn-salinity interaction were statistically insignificant, whereas the quadratic effect of Zn was highly significant on hydrocarbon degradation. The study on effects of metallic chloro-complexes showed that the total aqueous concentration of Cd or Zn does not give a reliable indication of overall toxicity to the microbial activity in the presence of high salinity levels.     

Demography and disappearing merchandise: How older workforces influence retail shrinkage

Prior research on retail shrinkage has taken a largely individual‐level approach to theorizing about why it occurs, showing that older employees are less prone to theft and more vigilant in preventing customer shoplifting than younger personnel. However, given the influence of organizational contexts on organizational behavior, theorizing about shrinkage may be enhanced by the consideration of business‐unit level contextual variables. The present study addressed this concern by examining the relationship between store‐level age composition, whistle‐blowing (WB) climate, and shrinkage in 726 retail stores. Results indicated that the negative mean age–shrinkage relationship was stronger when there was less age diversity or a climate more supportive of WB. Moreover, the negative WB climate–shrinkage linkage was stronger when the mean age was higher. Copyright © 2011 John Wiley & Sons, Ltd.     

Microwave-assisted synthesis of biodegradable and antibacterial thiophene,furan and thiazole derivatives

Environmental Chemistry Letters - The rise of bacterial resistance to common clinical antibiotics is calling for alternative techniques to synthesize antibacterial drugs with high biodegradability....     

Minimizing opportunity costs to aquatic connectivity restoration while controlling an invasive species

Controlling invasive species is critical for conservation but can have unintended consequences for native species and divert resources away from other efforts. This dilemma occurs on a grand scale in the North American Great Lakes, where dams and culverts block tributary access to habitat of desirable fish species and are a lynchpin of long‐standing efforts to limit ecological damage inflicted by the invasive, parasitic sea lamprey (Petromyzon marinus). Habitat restoration and sea‐lamprey control create conflicting goals for managing aging infrastructure. We used optimization to minimize opportunity costs of habitat gains for 37 desirable migratory fishes that arose from restricting sea lamprey access (0–25% increase) when selecting barriers for removal under a limited budget (US$1–105 million). Imposing limits on sea lamprey habitat reduced gains in tributary access for desirable species by 15–50% relative to an unconstrained scenario. Additional investment to offset the effect of limiting sea‐lamprey access resulted in high opportunity costs for 30 of 37 species (e.g., an additional US$20–80 million for lake sturgeon [Acipenser fulvescens]) and often required ≥5% increase in sea‐lamprey access to identify barrier‐removal solutions adhering to the budget and limiting access. Narrowly distributed species exhibited the highest opportunity costs but benefited more at less cost when small increases in sea‐lamprey access were allowed. Our results illustrate the value of optimization in limiting opportunity costs when balancing invasion control against restoration benefits for diverse desirable species. Such trade‐off analyses are essential to the restoration of connectivity within fragmented rivers without unleashing invaders.     

Effectiveness of Panama as an intercontinental land bridge for large mammals

Habitat fragmentation is a primary driver of wildlife loss, and establishment of biological corridors is a common strategy to mitigate this problem. A flagship example is the Mesoamerican Biological Corridor (MBC), which aims to connect protected forest areas between Mexico and Panama to allow dispersal and gene flow of forest organisms. Because forests across Central America have continued to degrade, the functioning of the MBC has been questioned, but reliable estimates of species occurrence were unavailable. Large mammals are suitable indicators of forest functioning, so we assessed their conservation status across the Isthmus of Panama, the narrowest section of the MBC. We used large-scale camera-trap surveys and hierarchical multispecies occupancy models in a Bayesian framework to estimate the occupancy of 9 medium to large mammals and developed an occupancy-weighted connectivity metric to evaluate species-specific functional connectivity. White-lipped peccary (Tayassu pecari), jaguar (Panthera onca), giant anteater (Myrmecophaga tridactyla), white-tailed deer (Odocoileus virginianus), and tapir (Tapirus bairdii) had low expected occupancy along the MBC in Panama. Puma (Puma concolor), red brocket deer (Mazama temama), ocelot (Leopardus pardalis), and collared peccary (Pecari tajacu), which are more adaptable, had higher occupancy, even in areas with low forest cover near infrastructure. However, the majority of species were subject to ≥1 gap that was larger than their known dispersal distances, suggesting poor connectivity along the MBC in Panama. Based on our results, forests in Darien, Donoso–Santa Fe, and La Amistad International Park are critical for survival of large terrestrial mammals in Panama and 2 areas need restoration.     

Estimating the normal background rate of species extinction

A key measure of humanity's global impact is by how much it has increased species extinction rates. Familiar statements are that these are 100–1000 times pre‐human or background extinction levels. Estimating recent rates is straightforward, but establishing a background rate for comparison is not. Previous researchers chose an approximate benchmark of 1 extinction per million species per year (E/MSY). We explored disparate lines of evidence that suggest a substantially lower estimate. Fossil data yield direct estimates of extinction rates, but they are temporally coarse, mostly limited to marine hard‐bodied taxa, and generally involve genera not species. Based on these data, typical background loss is 0.01 genera per million genera per year. Molecular phylogenies are available for more taxa and ecosystems, but it is debated whether they can be used to estimate separately speciation and extinction rates. We selected data to address known concerns and used them to determine median extinction estimates from statistical distributions of probable values for terrestrial plants and animals. We then created simulations to explore effects of violating model assumptions. Finally, we compiled estimates of diversification—the difference between speciation and extinction rates for different taxa. Median estimates of extinction rates ranged from 0.023 to 0.135 E/MSY. Simulation results suggested over‐ and under‐estimation of extinction from individual phylogenies partially canceled each other out when large sets of phylogenies were analyzed. There was no evidence for recent and widespread pre‐human overall declines in diversity. This implies that average extinction rates are less than average diversification rates. Median diversification rates were 0.05–0.2 new species per million species per year. On the basis of these results, we concluded that typical rates of background extinction may be closer to 0.1 E/MSY. Thus, current extinction rates are 1,000 times higher than natural background rates of extinction and future rates are likely to be 10,000 times higher. Estimación de la Tasa Normal de Extinción de Especies     

Effects of the polychlorinated biphenyl Aroclor® 1254 on the American oyster Crassostrea virginica

Young oysters (Crassostrea virginica) were continuously exposed to Aroclor^® 1254, a polychlorinated biphenyl (PCB), in flowing, unfiltered seawater. Growth rate (height and in-water weight) was significantly reduced (=0.05) in oysters exposed to 5 g/l (ppb) for 24 weeks. Growth rate was not affected in oysters exposed to 1 ppb for 30 weeks. Mortality was not significant in exposed and control groups. In oysters exposed to 5 ppb, greatest PCB residue (whole body) was 425 mg/kg (ppm), 85,000x the concentration in the water, and less than 0.3 ppm was retained after 28 weeks depuration in PCB-free water. In oysters exposed to 1 ppb, greatest residue was 101 ppm, 101,000x the concentration in the water, and less than 0.2 ppm was retained after 12 weeks depuration. Examination of oysters exposed to 5 ppb of this PCB for pathogenesis revealed atrophy of digestive diverticular epithelium and degeneration of vesicular connective tissues concomitant with leukocytic infiltration, but tissue recovery seemed excellent after 12 weeks depuration.Registered trademark, Monsanto Company, St. Louis, Missouri, USA. Mention of commercial products or trade names does not constitute endorsement by the Environmental Protection Agency.Contribution No. 146, Gulf Breeze Laboratory.     

Rearing Pandalus borealis larvae in the laboratory

Larvae of the northern shrimp Pandalus borealis (Krøyer) are pelagic. In the Estuary and Gulf of St. Lawrence, Canada, the early stages are found in the upper 25-m of the water column in spring and early summer and are expected to experience a range of water temperatures from as low as 0°C to as high at 6°C. Little is known of the impact of water temperature on metabolic requirements of northern shrimp larvae. In this study, routine respiration (VO₂), maximum respiration (electron transport system activity, ETSA) and metabolic scope for growth (MS, ETSA–VO₂) of northern shrimp larvae were measured as a function of temperature (3, 5 and 8°C), developmental stage (I–V at 3°C, I–VII at 5°C and 8°C) and growth rate in dry mass. After logarithmic transformation, all three metabolic variables were linearly related to dry mass. The increase in VO₂ with body mass was faster at 5°C than at 3 or 8°C, whereas with ETSA this increase was slower. As a result, MS increased more slowly with dry mass at 5°C than at 3 and 8°C. However, MS did not limit growth in this study, since it explained only 39% of the variability in growth. All three metabolic variables as well as growth varied together as a function of temperature and ontogeny. Q₁₀ of all three metabolic variables ranged from 1.6 and 2.2 for stages I–V larvae, except for VO₂ at stage I (3.9) and stage III (2.9).     

Nest defence by song sparrows: methodological and life history considerations

Summary Several aspects of nest defence behavior were investigated in song sparrows (Melospiza melodia) in eastern Ontario. Two independent tests were made of the hypothesis that the increase in nest defence observed through a nesting attempt is due to the birds becoming familiar with the nest threat, rather than because the nest contents increase in value to the parents. Neither test supported the hypothesis. As predicted by life history theory for species with age-independent mortality, males did not defend their nest more vigorously as they become older. Parents defended their nests less vigorously through the breeding season, contrary to the expected pattern of increased nest defence in response to declining renesting potential. This result may be attributable to a decline in offspring value through the breeding season. Nest defence behavior of mated individuals was positively correlated, independent of factors such as offspring age, renesting potential and brood size. From this result it is proposed that a source of variation in nest defence behavior may be individuals basing their own response on their mate's response in a positive feedback fashion. Males defended nests less vigorously than females, consistent with the expectation that males have lower certainty of parentage in the offspring. It is proposed that variation in paternal uncertainty could contribute to the unexplained variation reported in nest defence studies.