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.     

A longitudinal study of the risks for introduction of severe footrot into sheep flocks in the south west of Norway

In 2008, ovine footrot was detected in Norway for the first time since 1948. By December 2012 it had spread to 99 flocks, all in the county of Rogaland in the south west of Norway, and 42% of which were located in the municipality of Rennesøy in Rogaland. The aim of this study was to investigate risk factors for contracting severe footrot in flocks of sheep. A flock was considered positive for severe footrot based on positive virulence test or by clinical signs in addition to a positive PCR test.     

Antimicrobial ability and growth promoting effects of feed supplemented with probiotic bacterium isolated from gut microlfora of Cirrhinus mrigala

The present studies were conducted to isolate, select, identify and characterize gut bacteria as antimicrobial and growth promoting agent for the feed of economical y important ifsh Cirrhinus mrigala. ...     

Biochemical changes in sunflower plants due to seed treatment/spray application with biocontrol agents

The application ofTrichoderma harzianum andPseudomonas fluorescens led to increases in dry matter content, starch, total soluble sugars (TSS) and reducing sugar contents in leaves of sunflower (Helianthus annuus) when done as seed treatment or coupled with spray. There was a significant increase in TSS and reducing sugars in stem tissue after treatment with biocontrol agents. The content of total phenols in leaves increased after treatment at 30 and 60 days after sowing (DAS) and at 30 DAS in stem tissues. Biocontrol agents increased the activities of phenylalanine ammonia lyase (PAL) in leaves and stem tissue after 30 DAS and significantly reduced total phenolic content and PAL activity in the stem at 60 DAS. Following treatment with biocontrol agents, seed lipid content increased, the proportion of linoleic acid increased and that of oleic acid decreased. Application of biocontrol agents to sunflower plants initiated certain biochemical changes, which can be considered to be part of the plant’s defense response. http://www.phytoparasitica.org posting August 6, 2008.     

Antimicrobial ability and growth promoting effects of feed supplemented with probiotic bacterium isolated from gut microflora of Cirrhinus mrigala

The present studies were conducted to isolate, select, identify and characterize gut bacteria as antimicrobial and growth promoting agent for the feed of economically important fish Cirrhinus mrigala. Intestinal microflora were isolated, counted, and identified, and their in vitro antibacterial properties were determined. The results have revealed that occurrence of Gram-negative rods was around 75% and of Gram-positive rods was 25%. Among the isolates Gram-positive were maintained in nutrient agar slants at 4°C. Of these, eight strains were replica-plated on agar seeded with Aeromonas hydrophila and only one strain CM2(C. mrigala 2) exhibited antibacterial properties in vitro showing inhibition against fish pathogen by well diffusion assay. This isolated strain was identified as Bacillus cereus. This bacterium was mass cultured and incorporated in the pelleted diet(40% protein and 18 k J g–1 gross energy) of C. mrigala to investigate its effect on growth performance, digestibility, nutrient retention and activities of digestive enzymes. The results of feeding trial revealed significantly(P<0.05) high growth performance in terms of specific growth rate, growth percent gain in body weight(BD)(272.4±1.5)%, high apparent protein digestibility((79.9±0.30)%) and low food conversion ratio in the group of fishes fed on diet containing B. cereus in comparison to the fishes fed on diet without probiotics. The carcass composition also revealed high accumulation of proteins((15.28±0.15) g 100 g–1) in fishes fed on diet containing probiotics. Intestinal enzyme activities of protease, amylase and cellulase were also significantly(P<0.05) high in the group of fishes fed on diet supplemented with probiotics indicating the extracellular enzyme production by B. cereus. These results indicate that probiotics stimulate the digestion through the supply of digestive enzyme and certain essential nutrients to animals. Also significantly(P<0.05) low excretion of metabolites, i.e., ammonia excretion and phosphate production(mg kg–1 BW d–1) was observed in the fishes fed with probiotic based diets. Thus, B. cereus appears to be a promising candidate for ptobiotic applications which can enhance growth performance and nutrient retention in C. mrigala.