Application of microbially induced calcite precipitation in erosion mitigation and stabilization of sandy soil foreshore slopes : a preliminary investigation

Eroding foreshores endanger the floodplains of many estuaries, as such, effective and environmentally friendly interventions are sought to stabilise slopes and mitigate erosion. As a step in forestalling these losses, we developed laboratory microcosms to simulate tidal cycles and examined the mechanisms of erosion and failure on sandy foreshore slopes. As an experimental aim, we applied microbially induced calcite precipitation (MICP) to selected slopes and compared the effectiveness of this microbial geo-technological strategy to mitigate erosion and stabilise slopes. To assess shoreline stability, thirty cycles of slowly simulated tidal currents were applied to a sandy slope. Significant sediment detachment occurred as tides moved up the slope surface. For steeper slopes, one tidal event was sufficient to cause collapse of the slopes to the soil's angle of repose (~35°). Subsequent tidal cycles gradually eroded surface sediments further reducing slope angle (on an average 0.2° per tidal event). These mechanisms were similar for all slopes irrespective of initial slope inclination. MICP was evaluated as a remedial measure by treating a steep slope of 53° and an erosion-prone slope angle of 35° with Sporosarcina pasteurii and cementation solution (0.7 M CaCl2 and urea) before tidal simulations. MICP produced 120 kg calcite per m3 of soil, filling 9.9% of pore space. Cemented sand withstood up to 470 kPa unconfined compressive stress and showed significantly improved slope stability; both slopes showed negligible sediment erosion. With efforts towards optimisation for upscaling and further environmental considerations (including effect of slope saturation on MICP treatment, saline water and estuarine/coastal ecology amongst others), the MICP process demonstrates promise to protect foreshore slope sites

Physiological effects of tourism and associated food provisioning in an endangered iguana

© The Author 2013. Deliberately feeding wildlife is an increasingly popular tourism-related activity despite a limited understanding of long-term impacts on the species being fed. As a result, tourist behaviours that may have adverse impacts on imperiled species have often been encouraged without the necessary evaluation or oversight. Here, we report the responses of Northern Bahamian Rock Iguanas (Cyclura cychlura) to human-visitation pressure and associated food provisioning. We compared a variety of blood chemistry parameters of iguanas subjected to supplemental feeding at popular tourist destinations with iguanas occurring on islands where supplemental feeding does not take place. We demonstrate that male and female iguanas inhabiting tourist-visited islands where supplemental feeding occurs do not differ in body condition or baseline stress and stress response (determined by corticosterone levels) compared with iguanas from non-visited islands. Both males and females from tourist-visited sites experienced a greater incidence of endoparasitic infection and atypical loose faeces. Indicators of dietary nutrition, including glucose, potassium, and uric acid values, also differed for both sexes from tourist-visited and unvisited islands. Male iguanas from visited islands differed significantly from those on non-visited islands in calcium, cholesterol, cobalt, copper, magnesium, packed cell volume, selenium, and triglyceride concentrations, whereas female iguanas from visited islands differed significantly in ionized calcium. Although the interpretation of these differences is challenging, chronic biochemical stressors could compromise individual health over time or decrease survivorship during periods of environmental stress. We suggest protocols that can be adopted throughout the region to ensure that supplemental feeding has fewer impacts on these long-lived iguanas

Repurposing blood glucose test strips for identification of the antimicrobial colistin

The presence and fate of antimicrobial residues in the environment is a subject of growing concern. Previous researchers have demonstrated the persistence of residues in soil and water. Additionally, antimicrobial resistance is a growing concern, particularly to public health, animal health and economic development. In this study, a low cost, commercial blood glucose meter was explored as the basis for detecting antimicrobial residues in conjunction with a microorganism sensitive to this residue. A microbial bioassay was developed based on the metabolic response of Geobacillus stearothermophilus, a sensitive bacteria used in the determination of antimicrobial residues in food products, by measuring changes in glucose as a result of metabolic activity. After optimizing experimental conditions, this sensing strategy was tested using bacterial cultures in the presence of colistin, a last-resort antibiotic used for human and animal health. Growth of G. stearothermophilus was measurable as a change in glucose concentration after 2–4 h incubation at 60 °C, when LB media was supplemented with 100 mg/dL of glucose. The lowest measured colistin concentration that resulted in inhibition of growth was 1 mg/L colistin and an increase in lag phase resulted at 100 µg/L colistin. To increase the sensitivity of the assay, we then added a sub-inhibitory concentration of chloramphenicol to the media and found that growth inhibition could be achieve at a lower colistin concentration of 8 µg /L. These results provide a promising basis for a future low-cost sensor to identify antimicrobial residues from environmental samples in the field

A 21-year record of vertically migrating subepilimnetic populations of Cryptomonas spp.

The vertical distribution and diel migration of Cryptomonas spp. were monitored continuously for 21 years in mesotrophic Cross Reservoir, northeast Kansas, USA. The movements of these motile algae were tracked on multiple dates during July–October of each year using in situ fluorometry and optical microscopy of Lugol’s iodine-preserved samples. Episodes of subepilimnetic diel vertical migration by Cryptomonas were detected and recorded on 221 different days between 1994 and 2014, with just 2 of these years (1998 and 2013) lacking any sampling events with deep peaks sufficiently large enough to track. Whenever a subepilimnetic layer of Cryptomonas was detectable, it was generally observed to ascend toward the bottom of the epilimnion beginning approximately at sunrise; to descend toward the lake bottom during the late afternoon and evening; and to remain as a deep-dwelling population until dawn of the following day. Moreover, there was high day-to-day consistency in the absolute water column depths at which the migrating algal cells would cease their ascending or descending movement. We believe this unique and remarkable dataset comprises the most detailed record of diel migratory behavior for any planktonic freshwater alga reported for a single freshwater lake

Effect of Exercise Training and +Gz Acceleration Training on Men

Countermeasures for reduction in work capacity (maximal oxygen uptake and strength) during spaceflight and enhanced orthostatic intolerance during re-entry, landing and egress from the return vehicle are continuing problems. The purpose for this study was to test the hypothesis that passive-acceleration training; supine, interval, exercise plus acceleration training and exercise combined with acceleration training would improve orthostatic tolerance in ambulatory men; and that addition of the aerobic exercise conditioning would not alter this improved tolerance from that of passive-acceleration training. Seven men (24-38 yr) underwent "Passive" training on the Ames human-powered centrifuge (HPC) for 30 min, "Exercise" training on the cycle ergometer with constant +Gz acceleration; and "Combined" exercise training at 40% to 90% of the HPC +Gz(max) exercise level. Maximal supine exercise loads increased significant (P<0.05) by 8.3% (Passive), 12.6% (Exercise), and by 15.4% (Combined) after training, but their post-training maximal oxygen uptakes and maximal heart rates were unchanged. Maximal time to fatigue (endurance) was unchanged with Passive was increased (P<0.05) with Exercise and Combined training. Thus, the exercise in the Exercise and Combined training Phases resulted in greater maximal loads and endurance without effect on maximal oxygen uptake or heart rate. There was a 4% to 6% increase (P<0.05) in all four quadriceps muscle volumes (right and left) after post-Combined training. Resting pre-tilt heart rate was elevated by 12.9% (P<0.05) only after Passive training suggesting that the exercise training attenuated the HR response. Plasma volume (% Delta) was uniformly decreased by 8% to 14% (P<0.05) at tilt-tolerance pre- vs. post-training indicating essentially no effect of training on the level of hypovolemia. Post-training tilt-tolerance time and heart rate were increased (P<0.05) only with Passive training by 37.8% and by 29.1%, respectively. Thus, addition of exercise training appeared to attenuate the increased Passive tilt-tolerance

Weak Lensing with SDSS Commissioning Data: The Galaxy-Mass Correlation Function To 1/h Mpc

(abridged) We present measurements of galaxy-galaxy lensing from early commissioning imaging data from the Sloan Digital Sky Survey (SDSS). We measure a mean tangential shear around a stacked sample of foreground galaxies in three bandpasses out to angular radii of 600'', detecting the shear signal at very high statistical significance. The shear profile is well described by a power-law. A variety of rigorous tests demonstrate the reality of the gravitational lensing signal and confirm the uncertainty estimates. We interpret our results by modeling the mass distributions of the foreground galaxies as approximately isothermal spheres characterized by a velocity dispersion and a truncation radius. The velocity dispersion is constrained to be 150-190 km/s at 95% confidence (145-195 km/s including systematic uncertainties), consistent with previous determinations but with smaller error bars. Our detection of shear at large angular radii sets a 95% confidence lower limit $s>140^{\prime\prime}$, corresponding to a physical radius of $260h^{-1}$ kpc, implying that galaxy halos extend to very large radii. However, it is likely that this is being biased high by diffuse matter in the halos of groups and clusters. We also present a preliminary determination of the galaxy-mass correlation function finding a correlation length similar to the galaxy autocorrelation function and consistency with a low matter density universe with modest bias. The full SDSS will cover an area 44 times larger and provide spectroscopic redshifts for the foreground galaxies, making it possible to greatly improve the precision of these constraints, measure additional parameters such as halo shape, and measure the properties of dark matter halos separately for many different classes of galaxies.Comment: 28 pages, 11 figures, submitted to A

Investigation of the correlation between odd oxygen and secondary organic aerosol in Mexico City and Houston

Many recent models underpredict secondary organic aerosol (SOA) particulate matter (PM) concentrations in polluted regions, indicating serious deficiencies in the models' chemical mechanisms and/or missing SOA precursors. Since tropospheric photochemical ozone production is much better understood, we investigate the correlation of odd-oxygen ([Ox]≡[O3]+[NO2]) [([O subscript x] ≡ [O subscript 3] + [NO subscript 2])] and the oxygenated component of organic aerosol (OOA), which is interpreted as a surrogate for SOA. OOA and Ox [O subscript x] measured in Mexico City in 2006 and Houston in 2000 were well correlated in air masses where both species were formed on similar timescales (less than 8 h) and not well correlated when their formation timescales or location differed greatly. When correlated, the ratio of these two species ranged from 30 μg [mu g] m−3/ppm [m superscript -3 / ppm] (STP) in Houston during time periods affected by large petrochemical plant emissions to as high as 160 μg [mu g] m−3/ppm [m superscript -3 / ppm] in Mexico City, where typical values were near 120 μg [mu g] m−3/ppm [m superscript -3 / ppm]. On several days in Mexico City, the [OOA]/[Ox] [[OOA] / O subscript x]] ratio decreased by a factor of ~2 between 08:00 and 13:00 local time. This decrease is only partially attributable to evaporation of the least oxidized and most volatile components of OOA; differences in the diurnal emission trends and timescales for photochemical processing of SOA precursors compared to ozone precursors also likely contribute to the observed decrease. The extent of OOA oxidation increased with photochemical aging. Calculations of the ratio of the SOA formation rate to the Ox [O subscript x] production rate using ambient VOC measurements and traditional laboratory SOA yields are lower than the observed [OOA]/[Ox] [[OOA] / O subscript x]] ratios by factors of 5 to 15, consistent with several other models' underestimates of SOA. Calculations of this ratio using emission factors for organic compounds from gasoline and diesel exhaust do not reproduce the observed ratio. Although not successful in reproducing the atmospheric observations presented, modeling P(SOA)/P(Ox) [P (SOA) / P (O subscript x)] can serve as a useful test of photochemical models using improved formulation mechanisms for SOA.National Science Foundation (U.S.) (Grant ATM-528227)National Science Foundation (U.S.) (Grant ATM-0528170)National Science Foundation (U.S.) (Grant ATM-0513116)National Science Foundation (U.S.) (Grant ATM-0449815)United States. Dept. of Energy. Office of Biological and Environmental Research. Atmospheric Science Program (Grant DE-FGO2-05ER63982)United States. Dept. of Energy. Office of Biological and Environmental Research. Atmospheric Science Program (Grant DEFGO2- 05ER63980)United States. Dept. of Energy. Office of Biological and Environmental Research. Atmospheric Science Program (Grant DE-FG02-08ER64627)United States. National Oceanic and Atmospheric Administration (Grant NA08OAR4310656