Simultaneous measurement of <i>δ</i>¹³C, <i>δ</i>¹⁸O and <i>δ</i>¹⁷O of atmospheric CO₂ – performance assessment of a dual-laser absorption spectrometer

Using laser absorption spectrometry for the measurement of stable isotopes of atmospheric CO2 instead of the traditional isotope ratio mass spectrometry method decreases sample preparation time significantly, and uncertainties in the measurement accuracy due to CO2 extraction and isobaric interferences are avoided. In this study we present the measurement performance of a new dual-laser instrument developed for the simultaneous measurement of the δ13C, δ18O and δ17O of atmospheric CO2 in discrete air samples, referred to as the Stable Isotopes of CO2 Absorption Spectrometer (SICAS). We compare two different calibration methods: the ratio method, based on the measured isotope ratio and a CO2 mole fraction dependency correction, and the isotopologue method, based on measured isotopologue abundances. Calibration with the ratio method and isotopologue method is based on three different assigned whole-air references calibrated on the VPDB (Vienna Pee Dee Belemnite) and the WMO 2007 (World Meteorological Organization) scale for their stable isotope compositions and their CO2 mole fractions, respectively. An additional quality control tank is included in both methods to follow long-term instrument performance. Measurements of the quality control tank show that the measurement precision and accuracy of both calibration methods is of similar quality for δ13C and δ18O measurements. During one specific measurement period the precision and accuracy of the quality control tank reach WMO compatibility requirements, being 0.01 ‰ for δ13C and 0.05 ‰ for δ18O. Uncertainty contributions of the scale uncertainties of the reference gases add another 0.03 ‰ and 0.05 ‰ to the combined uncertainty of the sample measurements. Hence, reaching WMO compatibility for sample measurements on the SICAS requires reduction of the scale uncertainty of the reference gases used for calibration. An intercomparison of flask samples over a wide range of CO2 mole fractions has been conducted with the Max Planck Institute for Biogeochemistry, resulting in a mean residual of 0.01 ‰ and −0.01 ‰ and a standard deviation of 0.05 ‰ and 0.07 ‰ for the δ13C measurements calibrated using the ratio method and the isotopologue method, respectively. The δ18O could not be compared due to depletion of the δ18O signal in our sample flasks because of storage times being too long. Finally, we evaluate the potential of our Δ17O measurements as a tracer for gross primary production by vegetation through photosynthesis. Here, a measurement precision of <0.01 ‰ would be a prerequisite for capturing seasonal variations in the Δ17O signal. Lowest standard errors for the δ17O and Δ17O of the ratio method and the isotopologue method are 0.02 ‰ and 0.02 ‰ and 0.01 ‰ and 0.02 ‰, respectively. The accuracy results show consequently results that are too enriched for both the δ17O and Δ17O measurements for both methods. This is probably due to the fact that two of our reference gases were not measured directly but were determined indirectly. The ratio method shows residuals ranging from 0.06 ‰ to 0.08 ‰ and from 0.06 ‰ to 0.1 ‰ for the δ17O and Δ17O results, respectively. The isotopologue method shows residuals ranging from 0.04 ‰ to 0.1 ‰ and from 0.05 ‰ to 0.13 ‰ for the δ17O and Δ17O results, respectively. Direct determination of the δ17O of all reference gases would improve the accuracy of the δ17O and thereby of the Δ17O measurements.

Influence of Environmental Stressors on the Microbiota of Zebra Mussels (Dreissena polymorpha)

Host-associated microbiota play a critical role in host fitness by providing nutrition, enhancing digestion capabilities, and by providing protection from pathogens. Here, we investigated the effects of two environmental stressors, temperature, and salinity, on the microbiota associated with zebra mussels (ZMs), a highly invasive bivalve in North America. To examine this in detail, lake-collected ZMs were acclimated to laboratory conditions, and subjected to temperature and salinity stress conditions. The impact of these stressors on the diversity, composition, and dynamics of ZM-associated microbiota were assessed by using amplicon- and shotgun-based sequencing, and qPCR-based approaches. Elevated temperature was found to be the primary driver of ZM mortality, although salinity alone also increased its likelihood. Stressor-induced ZM mortality, which ranged between 53 and 100%, was concomitant with significant increases in the relative abundance of several genera of putative opportunistic pathogens including Aeromonas. These genera were only present in low relative abundance in ZMs obtained from the control tank with 0% mortality. Shotgun sequencing and qPCR analyses indicated that the relative and absolute abundances of pathogenic Aeromonas species (particularly A. veronii) were significantly greater in temperature-induced dead ZMs. Taken together, our results show that environmental stress, especially elevated temperature (> 25 °C), is associated with the rapid mortality of ZMs as well as the proliferation of putative opportunistic bacterial pathogens.

Heavy Metal Uptake and Bioaccumulation by Mangrove Grab (Goniopsis pelli) from used Drilling Mud, Niger Delta, Nigeria

This study was carried out to evaluate some heavy metal uptake and bioaccumulation in the meat, egg and shell of G. pelli from used drilling mud. The experimental approach involved the exposure of ten of the test organism G. pelli to six acute concentrations of drilling mud representing 0% (control), 10%, 20%, 30%, 40% and 50% for 96 hours in three replicates after the range finding test was conducted to determine the LC50. From the LC50, the test organism was further exposed to four sub-lethal concentrations of drilling mud (0%, 5%, 10% and 15%) for 21 days to evaluate the heavy metal uptake by the test organism. the result showed that heavy metal uptake increased in the order of meat (<0.001-2.36±0.12), shell (<0.001-3.31±0.19) and egg (<0.001-0.54±0.05) when compared with those in control tank. Copper was highest (3.31μg/g) in the shell and lowest (0.26μg/g) in the egg; zinc was highest (2.36μg/g) in the meat and lowest (0.22μg/g) in the shell; chromium was highest (0.12μg/g) in the meat and lowest (0.06μg/g) in the egg; cadmium was highest (0.2μg/g) in the shell and lowest (0.001μg/g) in the egg while lead had equal value (<0.001) in the meat, shell and egg of the test organism. This could pose a very serious health challenge to the consumers of G. pelli and other aquatic fishery resources if nothing is done to ensure the best practice in drilling activities in other to avoid pollution of the water bodies through drilling. Keywords: Heavy metals, bioaccumulation, drilling mud, Goniopsis pelli

Tank-Mixing Pesticides without Disasters

Tank-mixing several pesticides is a common practice in conducting pest control. Tank mixes can consist of much more than just pesticides, such as fertilizers, micronutrients, and adjuvants. However, applicators must be aware of potential problems given that there are so many potential combinations when combining these products. Manufacturers cannot possibly test for all of these combinations, so both chemical and physical incompatibility are a concern with the practice. This new 4-page document, written by Frederick M. Fishel and published by the UF/IFAS Pesticide Information Office, describes some common-sense practices to help overcome costly tank-mixing errors.https://edis.ifas.ufl.edu/pi285

Effect of Temperature on Nutrient Removal Efficiency of Water Hyacinth for Phytoremediation Treatment

Wetlands have been introduced as natural based devices for treating the stormwater runoff. Temperature plays an important role in the nutrient removal process of wetland plants. Thus, the effect of temperature on nutrient removal efficiency of the water hyacinth plant was evaluated in this study. Water quality of both tanks that containing water hyacinth plants and control tank were monitored continuously for 2 weeks. The collected water samples were examined for total phosphorous (TP), turbidity, dissolved oxygen (DO), pH, conductivity (Cond.), total dissolve solid (TDS) and water temperature. The results showed that there are changes in the water quality concentration although there is no water hyacinth in the control tank. The release of phosphorus from the organic matter and particle in the control tank is suggested that occurred during the high temperature period. The optimum removal of nutrient occurred during the water temperature at 30℃. This clearly showed the effect of temperature on the flux of phosphorus in the water tank.

Tank Mixing Fungicides for Effectiveness Against Eastern Filbert Blight of Hazelnut

Hazelnut (Corylus avellana) production in Oregon primarily occurs on cultivars susceptible to Anisogramma anomala, the causal agent of eastern filbert blight (EFB). Management of EFB involves planting resistant cultivars, removal of cankered limbs, and the application of fungicides. Tank mixes of demethylation-inhibiting (DMI; Fungicide Resistance Action Committee [FRAC] group 3) or quinone outside inhibitor (QoI; FRAC group 11) fungicides with chlorothalonil (FRAC group M5) at full or reduced rates were evaluated for effectiveness against A. anomala. The use of chlorothalonil in a mix with a DMI or QoI fungicide was an effective treatment for EFB even if each component of the mix was at half the labeled rate. Different liquid or dry formulations of chlorothalonil were equally effective in a tank mix for EFB control. The combination of propiconazole (FRAC group 3) tank mixed with trifloxystrobin (FRAC group 11) was not effective, whereas trees treated with propiconazole tank mixed with pyraclostrobin (FRAC group 11) resulted in significantly fewer EFB cankers compared with nontreated trees. When using tank mixes for EFB management, DMI fungicides should remain at full rates while mixing with a half-rate of chlorothalonil. In contrast, QoI fungicides and chlorothalonil could both be used at half-rates and still maintain acceptable EFB control. Tank mixing chlorothalonil with fungicides at risk of resistance development can help maintain consistent EFB control and should help prevent or delay the emergence of fungicide-resistant A. anomala isolates.

Willows and Reeds for Biomediation of Landfill Leachate: Redox Potential in the Root Zone

Constructed wetlands can be used for bioremediation of landfill leachate (LL) making it safe to discharge into the environment. Wetland plants (reed and willow), contribute to pollutant removal, particularly of organic and nitrogen loads. Root exudates stimulate microbial activity and elevate oxygen levels in the rhizosphere which promotes nitrification. This study investigated the effects of reed and willow on bioremediation of LL in comparison with an unplanted control by measuring redox potential levels in the rhizosphere of microcosm systems in a greenhouse. Redox potential in the reed rhizosphere was consistently the highest, with the willow rhizosphere consistently the lowest. Redox potential fluctuated in the willow rhizosphere during daylight hours, with large decreases in the morning. Levels of NH4 + decreased dramatically in the first day of the experiment and remained at similar low levels in all tanks. Removal of ammonia took place in the control tank with peaks in NO2 - and NO3 -, but levels of NO3 - remained high. Removal of ammonia was also observed in the reed tank with a peak in NO2 -, but there was no peak in NO3 -, as well as in the willow tank, but there were no peaks in NO2 - or NO3 -. Final levels of totalnitrogen, nitrate and chemical oxygen demand where considerably lower in the reed and willow tank than the unplanted control.

THE EFFECT OF FEEDING Lactobacillus ON GROWTH, SURVIVAL RATE AND PROTEASE ACTIVITY OF Litopenaeus vannamei

This study examined the effect of two Lactobacillus bacteria on protease activity and growth rate of Litopenaeus vannamei. An experiment was conducted to examine protease activity and growth rate. The experiment consisted of two treatment tanks, the first tank was provided with artemia immersed in 2.6 x 1016 cfu/mL of bacteria solution, the second tank served as the control tank. After 20 days, the L. vannamei in the tank that received Lactobacillus have significantly different in growth, survival rate and protease activity (P<0.05) compared to the control, but no significant difference between Lactobacillus casei and Lactobacillus plantarum treatments. Within the digestive organ, protease activity of hepatopancreas and stomach demonstrated significant higher activity (P<0.05) compared to the intestine.