Quantification of seasonal sediment and phosphorus transport dynamics in an agricultural watershed using radiometric fingerprinting techniques

Purpose

Phosphorus (P) is a limiting nutrient for most US Midwestern aquatic systems and, therefore, increases of P, through point or non-point sources (NPS) of pollution such as agriculture, causes eutrophication. Identifying specific NPS contributions (e.g., upland vs. stream channels) for sediments and P is difficult due to the distributed nature of the pollution. Therefore, studies which link the spatial and temporal aspects of sediment and P transport in these systems can help better characterize the extent of NPS pollution.

Materials and methods

Our study used fingerprinting techniques to determine sources of sediments in an agricultural watershed (the North Fork of the Pheasant Branch watershed; 12.4 km² area) in Wisconsin, USA, during the spring, summer, and fall seasons of 2009. The primary sources considered were uplands (cultivated fields), stream bank, and streambed. The model used fallout radionuclides, ¹³⁷Cs, and ²¹⁰Pb_xs, along with total P to determine primary sediment sources. A shorter-lived fallout radioisotope, ⁷Be, was used to determine the sediment age and percent new sediments in streambed and suspended sediment samples (via the ⁷Be/²¹⁰Pb_xs ratio).

Results and discussion

Upland areas were the primary source of suspended sediments in the stream channels followed by stream banks. The sediment age and percent new sediment for the streambed and suspended sediments showed that the channel contained and transported newer (or more recently tagged with ⁷Be) sediments in the spring season (9–131 days sediment age), while relatively old sediments (165–318 days) were moving through the channel system during the fall season.

Conclusions

Upland areas are the major contributors to in-stream suspended sediments in this watershed. Sediment resuspension in stream channels could play an important role during the later part of the year. Best management practices should be targeted in the upland areas to reduce the export of sediments and sediment-bound P from agricultural watersheds.     

Microbial dynamics after adding bovine manure effluent together with a nitrification inhibitor (3,4 DMPP) in a microcosm experiment

The application of animal manure effluents in agriculture in combination with nitrification inhibitors should be beneficial for nutrient recycling, soil quality, plant productivity, and greenhouse gas emission and offer economic advantages to make them an alternative to conventional fertilizers. The present study aims to estimate the effects of the addition of bovine manure effluent alone or together with a nitrification inhibitor (3,4-dymethylpyrazol-phosphate (3,4 DMPP)) on the microbial community dynamics in a Mediterranean soil in an incubation experiment over 28 days. The application of the bovine manure effluent increased respiration, microbial biomass carbon, fungal and bacterial growth, and enzyme activities and changed the microbial community structure evaluated by the phospholipid fatty acid pattern. Adding the bovine manure effluent together with the nitrification inhibitor, although partly negating the positive effect of the effluent on soil microbial activity, still resulted in higher or similar growth and activity as in the control. Our results indicate that the addition of the nitrification inhibitor 3,4 DMPP together with a bovine manure effluent could be a promising solution to control the animal manure effluent application effects on soil microbiological properties and microbial dynamics, as well as counteracting direct inhibiting effects of 3,4 DMPP on the soil heterotrophic community.     

Echinacea alkylamides modulate induced immune responses in T-cells

The effects of Echinacea and several of its phytochemical components on NFkappaB expression by Jurkat cells (a human T-cell line) were investigated in vitro. In the absence of stimulation, Echinacea and its components exerted no significant effect on basal NFkappaB expression levels. In the presence of endotoxin (LPS), NFkappaB expression was decreased. However, this decrease was significantly reversed by treatment with cichoric acid, an Echinacea root extract (prepared from both Echinacea angustifolia and Echinacea purpurea) and the alkylamide fraction derived from this combination. For the phorbol myristate acetate stimulation of Jurkat cells, effects on NFkappaB expression were mixed. Depending on the concentration, cichoric acid and a 2,4-diene alkylamide significantly induced NFkappaB levels, whereas a 2-ene alkylamide caused a significant inhibition. In contrast, both the Echinacea and the mixed alkylamide fraction exerted no effect. The alkylamide results indicate that the two basic forms of these compounds present in Echinacea may have opposing effects. These opposing effects demonstrate the importance of a knowledge, not only of the phytochemical make-up of a herbal preparation, but also of the actions of each component and the consequences of differing relative amounts in the preparation being investigated.     

A comparison of aggressiveness and deoxynivalenol production between Canadian <Emphasis Type="Italic">Fusarium graminearum</Emphasis> isolates with 3-acetyl and 15-acetyldeoxynivalenol chemotypes in field-grown spring wheat

Twenty four isolates of Fusarium graminearum, half of which were 3-acetyldeoxynivalenol (3-ADON) and half 15-acetyldeoxynivalenol (15-ADON) chemotypes, were tested for their ability to produce deoxynivalenol and to cause Fusarium head blight (FHB) in spring wheat cultivars. The objectives of this study were to determine (1) whether 3-ADON isolates differ in aggressiveness, as measured by the FHB index, and DON production from 15-ADON isolates under field conditions, and (2) whether the performance of resistant host cultivars was stable across isolates. Field tests of all isolates were conducted with three replicates at each of two locations in Canada and Germany in 2008 with three host genotypes differing in FHB resistance level. The resistant host genotype showed resistance regardless of the chemotype or location. The differences between mean FHB indices of 3-ADON and 15-ADON isolates were not significant for any wheat genotype. In contrast, average DON production by the 3-ADON isolates (10.44 mg kg⁻¹) was significantly (P < 0.05) higher than for the 15-ADON isolates (6.95 mg kg⁻¹) at three of the four locations where moderately resistant lines were tested, and at both locations where susceptible lines were evaluated. These results indicate that 3-ADON isolates could pose a greater risk to food safety. However, as the mean aggressiveness and DON production of 3-ADON and 15-ADON chemotypes was similar on highly resistant lines, breeding and use of highly resistant lines is still the most effective measure of reducing the risks associated with DON in wheat.     

Mammalian Growth Hormone-Releasing Hormone Indirectly Stimulates Sex Steroid Production in Tilapia

Abstract.— Fish possess a growth hormone similar to mammalian growth hormone, and the presence of a growth hormone-releasing hormone-like material in the brain has been demonstrated in several teleost species. We investigated the effect of a mammalian growth hormone-releasing hormone on serum estradiol-17β and testosterone concentrations in tilapia Oreochromis mossambicus and a hybrid O. niloticus × O aureus because growth hormone has been implicated in the regulation of gonadal functions in teleosts. Three hours after injecting the releasing hormone, male and female serum testosterone concentrations significantly increased compared to controls, while serum estradiol-17β concentrations increased significantly only in females. These increases were commensurate with respective serum steroid concentrations in fish injected with gonadotropin releasing-hormone. Studies utilizing hypophysectomized fish resulted in non-detectable levels of serum sex steroids in fish treated with the growth hormone-releasing hormone; however, significant increases occurred in fish treated with human chorionic gonadotropin. Similarly, gonadal tissue incubated with growth hormone releasing hormone had non-detectable levels of sex steroids in the media, whereas gonads incubated with human chorionic gonadotropin had significant increases in sex steroid concentrations. These studies suggest that growth hormone-releasing hormone acts at the level of the pituitary. Although mammalian growth hormones have been shown to increase serum gonadotropic hormone concentrations, this study provides evidence that a mammalian growth hormone-releasing hormone has the ability to indirectly increase sex steroid levels in fish.     

Mycobacterium fortuitum infection interference with Mycobacterium bovis diagnostics: natural infection cases and a pilot experimental infection

Mycobacterium fortuitum and at least 1 unidentified species of soil mycobacteria were isolated from lymph nodes from 4 of 5 African buffalo (Syncerus caffer) that had been culled because of positive test results using the Bovigam assay. The buffalo were part of a group of 16 free-ranging buffalo captured in the far north of the Kruger National Park (South Africa) assumed to be free of bovine tuberculosis. No Mycobacterium bovis was isolated. To investigate the possible cause of the apparent false-positive diagnosis, the Mycobacterium isolates were inoculated into 4 experimental cattle and their immune responses monitored over a 13-week period, using the gamma interferon assay. The immune reactivity was predominantly directed toward avian tuberculin purified protein derivative (PPD) and lasted for approximately 8 weeks. During that period 3 of 4 cattle yielded positive test results on 1 or 2 occasions. The immune responsiveness was boosted when the inoculations were repeated after 15 weeks, which led to 2 subsequent positive reactions in the experimental animal that did not react previously. Including an additional stimulatory antigen, sensitin prepared from M. fortuitum in the gamma interferon assay, showed that it was able to elicit a detectable gamma interferon response in all 4 experimentally inoculated cattle when applied in parallel with bovine and avian tuberculin PPD for the stimulation of blood samples. The implications of occasional cross-reactive responses in natural cases of infection with environmental mycobacteria in the diagnosis of bovine tuberculosis in African buffalo and cattle in South Africa are discussed.     

Candida rugosa lipase LIP1-catalyzed transesterification to produce human milk fat substitute

Structured lipids (SLs) containing palmitic and oleic acids were synthesized by transesterification of tripalmitin with either oleic acid or methyl oleate as acyl donor. This SL with palmitic acid at the sn-2 position and oleic acid at sn-1,3 positions is similar in structure to human milk fat triacylglycerol. LIP1, an isoform of Candida rugosa lipase (CRL), was used as biocatalyst. The effects of reaction temperature, substrate molar ratio, and time on incorporation of oleic acid were investigated. Reaction time and temperature were set at 6, 12, and 24 h, and 35, 45, and 55 degrees C, respectively. Substrate molar ratio was varied from 1:1 to 1:4. The highest incorporation of oleic acid (37.7%) was at 45 degrees C with methyl oleate as acyl donor. Oleic acid resulted in slightly lesser (26.3%) incorporation. Generally, higher percentage incorporation of oleic acid was observed with methyl oleate (transesterification) than with oleic acid (acidolysis). In both cases percentage incorporation increased with reaction time. Incorporation decreased with increase in temperature above 45 degrees C. Initially, oleic acid incorporation increased with increase in substrate molar ratio up to 1:3. LIP1 was also compared with Lipozyme RM IM as biocatalysts. The tested reaction parameters were selected on the basis of maximum incorporation of C18:1 obtained during optimization of LIP1 reaction conditions. Reaction temperature was maintained at 45, 55, and 65 degrees C. Lipozyme RM IM gave highest oleic acid incorporation (49.4%) at 65 degrees C with methyl oleate as acyl donor. Statistically significant (P < 0.05) differences were observed for both enzymes. SL prepared using Lipozyme RM IM may be more suitable for possible use in human milk fat substitutes.