Sediment nitrogen transformations during an ice-free winter in a large, shallow, eutrophic lake

Objectives: 1. Characterize and quantify water column nitrogen (N) cycling rates in lakes Peipsi and Võrtsjärv (Estonia) a. Ammonium (NH4+) uptake and regeneration b. Nitrification 2. Characterize and quantify sediment–water interface N transformations and O2 demand in Lake Võrtsjärv a. Net nutrient (NOx, NH4+, urea, ortho–P), O2, and N2 fluxes b. Potential denitrification and DNRA c. Possible anammox d. N2 fixation (heterotrophic)Funding: EU, European Regional Development Fund, Estonian University of Life Sciences ASTRA project “Value-chain based bio-economy”Funding: EU, European Regional Development Fund, Estonian University of Life Sciences ASTRA project “Value-chain based bio-economy

Nitrogen cycling in Sabine Lake

As a part of continuing efforts to investigate nitrogen cycling in Texas estuaries, denitrification, nitrogen fixation, dissimilatory nitrate reduction to ammonium (DNRA), and sediment oxygen demand were measured in Sabine Lake, Texas. Estuarine phytoplankton production can be limited by N availability, and sediments often are an important source of dissolved inorganic N ... . Denitrification transforms combined N to gaseous forms ... . These end-products represent unavailable nutrient sources to most estuarine producers (e.g., phytoplankton and bacteria; Howarth et al. 1988). Thus, denitrification may drive systems toward N limitation (Seitzinger 1990). The purposes of this study were to evaluate the importance of denitrification in nitrogen cycling and examine environmental conditions influencing nitrogen cycling in Sabine Lake. A membrane inlet mass spectrometer (MIMS) for dissolved gas measurement and high performance liquid chromatography (HPLC) system for ammonium isotope measurements were used to quantify denitrification, N-fixation, DNRA, and sediment oxygen demand. Four sampling trips to Sabine Lake were made in June, September, December 2000 and March 2001. Here, we report water column measurements and incubation experiment results.Final report submitted to: The Texas Water Development Board, contract #2000-483-337July 2001Marine Scienc

Cognitive and affective components of challenge and threat states

We explored the cognitive and affective components of the Theory of Challenge and Threat States in Athletes (TCTSA) using a cross-sectional design. One hundred and seventy-seven collegiate athletes indicated how they typically approached an important competition on measures of self-efficacy, perceived control, achievement goals, emotional states and interpretation of emotional states. Participants also indicated to what extent they typically perceived the important competition as a challenge and/or a threat. The results suggest that a perception of challenge was not predicted by any of the cognitive components. A perception of threat was positively predicted by avoidance goals and negatively predicted by self-efficacy and approach goals. Both challenge and threat had a positive relationship with anxiety. Practical implications of this study are that an avoidance orientation appeared to be related to potentially negative constructs such as anxiety, threat and dejection. The findings may suggest that practitioners and researchers should focus on reducing an avoidance orientation, however the results should be treated with caution in applied settings, as this study did not examine how the combination of constructs exactly influences sport performance. The results provided partial support for the TCTSA with stronger support for proposed relationships with threat rather than challenge states

Vertical patterns in 15N natural abundance in PON from the surface waters of warm-core rings

The natural abundance of 15N in PON from the upper 200 m of 4 warm-core rings and the Sargasso Sea was measured. Minima in the δ15N of PON often occurred near the depth at which NO3− was first detectable. Frequently, maxima in PON concentration and minima in C/N ratio also co-occurred in this region. The average value for the δ15N of PON below the top of the nitracline was almost always greater than that above the top of the nitracline. The observed vertical pattern for the δ15N of PON is most likely the result of isotopic fractionation in the processes of NO3− uptake by phytoplankton at the base of the euphotic zone and the degradation of PON below the euphotic zone. Variations in the strength and coherence of this vertical pattern appear to occur in response to both rapid physical modification of the water column and the trophic status of the euphotic zone

Case report of spuriously low sodium and calcium in a 36-year-old male in primary care

An unseparated serum specimen for a 36-year-old male was received from primary care. The specimen arrived in the laboratory at Cork University Hospital one day after collection, as documented on the paper request card, and was promptly centrifuged. Analysis was delayed for three days due to operational constraints and serum indices were run at the same time as the biochemical analyses. Results showed a moderately haemolysed specimen with remarkably low concentrations of both sodium (119 mmol/L) and total calcium (1.15 mmol/L), with all other parameters within their appropriate reference intervals (RIs). The complete report was released electronically and both sodium and calcium results were phoned to, and acknowledged by, the requesting general practitioner (GP). Discussion between the medical scientists and clinical biochemist on duty raised the possibility that the specimen was significantly older than initially thought. Further discussion of results with the GP clarified that the documented time of collection corresponded with specimen receipt by the courier, rather than the time of phlebotomy. Thus, the specimen was 7 days old when received in the laboratory and 10 days old when analysed. This case illustrates the dangers of multiple convergent preanalytical errors. Laboratories should be mindful of the stability of analytes in unseparated blood and unusual patterns of results which might suggest a specimen is “old”, and that this may coexist with erroneous request information. Any potential adverse effects on patient care were prevented in this case by laboratory vigilance

Hurricane Disturbance Stimulated Nitrification and Altered Ammonia Oxidizer Community Structure in Lake Okeechobee and St. Lucie Estuary (Florida)

© Copyright © 2020 Hampel, McCarthy, Aalto and Newell. Nitrification is an important biological link between oxidized and reduced forms of nitrogen (N). The efficiency of nitrification plays a key role in mitigating excess N in eutrophic systems, including those with cyanobacterial harmful algal blooms (cyanoHABs), since it can be closely coupled with denitrification and removal of excess N. Recent work suggests that competition for ammonium (NH4+) between ammonia oxidizers and cyanoHABs can help determine microbial community structure. Nitrification rates and ammonia-oxidizing archaeal (AOA) and bacterial (AOB) community composition and gene abundances were quantified in Lake Okeechobee and St. Lucie Estuary in southern Florida (United States). We sampled during cyanobacterial (Microcystis) blooms in July 2016 and August 2017 (2 weeks before Hurricane Irma) and 10 days after Hurricane Irma made landfall. Nitrification rates were low during cyanobacterial blooms in Lake Okeechobee and St. Lucie Estuary, while low bloom conditions in St. Lucie Estuary coincided with greater nitrification rates. Nitrification rates in the lake were correlated (R2 = 0.94; p = 0.006) with AOA amoA abundance. Following the hurricane, nitrification rates increased by an order of magnitude, suggesting that nitrifiers outcompeted cyanobacteria for NH4+ under turbid, poor light conditions. After Irma, AOA and AOB abundances increased in St. Lucie Estuary, while only AOB increased in Lake Okeechobee. AOA sequences clustered into three major lineages: Nitrosopumilales (NP), Nitrososphaerales (NS), and Nitrosotaleales (NT). Many of the lake OTUs placed within the uncultured and uncharacterized NS δ and NT β clades, suggesting that these taxa are ecologically important along this eutrophic, lacustrine to estuarine continuum. After the hurricane, the AOA community shifted toward dominance by freshwater clades in St. Lucie Estuary and terrestrial genera in Lake Okeechobee, likely due to high rainfall and subsequent increased turbidity and freshwater loading from the lake into the estuary. AOB community structure was not affected by the disturbance. AOA communities were consistently more diverse than AOB, despite fewer sequences recovered, including new, unclassified, eutrophic ecotypes, suggesting a wider ecological biogeography than the oligotrophic niche originally posited. These results and other recent reports contradict the early hypothesis that AOB dominate ammonia oxidation in high-nutrient or terrestrial-influenced systems

Short Term Effects of Hurricane Irma and Cyanobacterial Blooms On Ammonium Cycling Along a Freshwater-Estuarine Continuum In South Florida

Lacustrine and coastal systems are vulnerable to the increasing number and intensity of tropical storms driven by climate change. Strong winds associated with tropical storms can mobilize nutrients in sediments and alter nitrogen and phosphorus cycling, leading to amplification of preexisting conditions, such as eutrophication and cyanobacterial blooms (cyanoHABs). In 2016, Florida declared a State of Emergency within and downstream of Lake Okeechobee (LO) due to toxic cyanobacterial blooms (primarily Microcystis). The blooms originated in LO, but flood control measures released water from LO to the brackish St. Lucie Estuary (SLE). In September 2017, Hurricane Irma traversed the Florida peninsula with sustained winds exceeding 160 km h–1, generating torrential rains over the watershed. We quantified ammonium (NH4+) regeneration and potential uptake rates, and Microcystis toxin gene (mcyD) abundance in LO and SLE during the massive bloom in July 2016, the bloom in August 2017 (2 weeks before Irma), and 10 days after Hurricane Irma landfall. In 2016, cyanoHABs were present in both LO and SLE, and potential NH4+ uptake rates were high in both systems. In 2017, the bloom was constrained to LO, potential NH4+ uptake rates in LO exceeded those in SLE, and mcyD gene abundance was greater in LO than SLE. Post Hurricane Irma, potential NH4+ uptake rates decreased significantly in LO and SLE, while mcyD gene abundance decreased in LO and increased slightly in SLE. Average NH4+ regeneration rates could support 25–40% of water column potential NH4+ demand in the lake and, when extrapolated to the entire LO water column, exceeded external nitrogen loading. These results emphasize the importance of internal NH4+ recycling for bloom expansion and toxicity in the lake and downstream estuaries. In 2018, the cyanobacterial bloom in the Okeechobee region was one of the largest recorded and is presumed to be driven by the aftermath of Hurricane Irma. Large-scale blooms have also been observed in SLE, likely due to LO flushing and decreased salinity post-hurricane. Thus, results from this study support predictions that increased frequency and strength of tropical storms will lead to more intense blooms in aquatic systems

Stabilising effect of α-lactalbumin on concentrated infant milk formula emulsions heat treated pre- or post-homogenisation

peer-reviewedProtein type and/or heat treatment pre- or post-homogenisation can affect the physical stability of infant formulations during manufacture. Previous research has described the use of α-lactalbumin addition in infant formulae, but has not demonstrated the effect of heating pre- or post-emulsion formulation during processing. The objective of this study was to evaluate the effect of both of these parameters. Three batches of model 1st-stage infant formula containing differing whey protein ratios (60:40 whey: casein with α-lactalbumin content 12, 30 or 48% of total protein) were prepared. Each batch was split; one half receiving heat treatment pre-homogenisation and the second half homogenised and then heat treated. Emulsion stability was determined by size exclusion chromatography, SDS-PAGE, particle size and viscosity measurements. There was a significant (P < 0.05) reduction in the formation of large soluble aggregates upon increasing α-lac concentration in emulsions heat treated either before or after homogenisation. Heat treatment of formulations post-homogenisation resulted in a higher (P < 0.05) D.v09 within the particle size distribution; increasing α-lactalbumin concentration to 30 or 48% significantly (P < 0.05) reduced the D.v09 within the particle size distribution in these emulsions. The viscosity of concentrates (55 % total solids) containing the 12% α-lactalbumin, heat treated post-homogenisation, was significantly greater (P < 0.05) than the equivalent emulsion heat treated pre-homogenisation; increasing the α-lactalbumin concentration to 30 or 48% significantly (P < 0.05) reduced viscosity. When the α-lactalbumin content was increased to 48% as a percentage of the total protein, heating before or after emulsion formation had no effect on concentrate viscosity. The findings demonstrate the importance of thermal denaturation/aggregation of whey proteins (and in particular, the ratio of α-lactalbumin to β-lactoglobulin) prior to homogenisation of infant formula emulsions

Catchment land cover and soil as predictors of organic carbon, nitrogen, and phosphorus levels in temperate lakes : [presentation]

The presentation took place at the 10th International Conference on Shallow Lakes in 2021.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 951963. This study was funded by the Estonian Research Council grants PUTJD954, PRG705, and PRG709, and by the European Regional Development Fund through Estonian University of Life Sciences ASTRA project “Value-chain based bio-economy”. The Estonian Ministry of Environment and the Estonian Environment Agency supported data collection in the national monitoring program.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 951963. This study was funded by the Estonian Research Council grants PUTJD954, PRG705, and PRG709, and by the European Regional Development Fund through Estonian University of Life Sciences ASTRA project “Value-chain based bio-economy”. The Estonian Ministry of Environment and the Estonian Environment Agency supported data collection in the national monitoring program