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Lincoln, New Zealand

Tirsgaard B.,Copenhagen University | Moran D.,Plant and Food Research | Steffensen J.F.,Copenhagen University
Aquatic Toxicology | Year: 2015

Land-based aquaculture systems expose fish to elevated dissolved CO2 levels, a factor that is correlated with reduced growth, feed conversion efficiency and body condition index. The physiological basis underlying the pathological effects of environmental hypercapnia is poorly understood, in particular for marine fish species. We investigated whether changes in energy expenditure and the specific dynamic action (SDA) of digestion and assimilation could account for the lower growth of adult Atlantic cod (Gadus morhua) under environmental hypercapnia. Fish acclimated to a partial pressure of 800μatm CO2 (0.6mmHg, 1.5mg/L) and 9200μatm CO2 (7mmHg, 18.7mg/L) exhibited no difference in maintenance metabolic rates, which concurs with previous research for this species and other fish species. At 9200μatm CO2 Atlantic cod had a significantly diminished (14%) maximum aerobic capacity. While hypercapnia did not affect the amount of oxygen required for the SDA process, it did prolong the SDA duration by 23%. The longer SDA process time may offer an explanation for the observation of lower feed intake, growth and condition factor in long-term hypercapnia studies. Comparison of aerobic scope and cardiac performance during digestion suggested that reduced oxygen delivery capacity under hypercapnia could be one mechanism by which CO2 prolongs SDA, although our results could not definitively demonstrate this effect. © 2014 Elsevier B.V.

Nelson W.R.,Plant and Food Research | Fisher T.W.,U.S. Department of Agriculture | Munyaneza J.E.,U.S. Department of Agriculture
European Journal of Plant Pathology | Year: 2011

Three haplotypes of the recently discovered bacterium species "Candidatus Liberibacter solanacearum" are described and related to geographic ranges. The first two are associated with Zebra Chip/Psyllid Yellows of potatoes and other solanaceous plants, vectored by the tomato/potato psyllid Bactericera cockerelli in North and Central America and New Zealand. The third is associated with diseased carrots in Finland and vectored by the carrot psyllid Trioza apicalis. The haplotypes are described by SNPs on the 16s rRNA, 16s/23s ISR and 50s rplJ and rplL ribosomal protein genes. These SNPs are inherited as a package across the three genes. Haplotype "a" has been found primarily from Honduras and Guatemala through western Mexico to Arizona and California, and in New Zealand. Haplotype "b" is currently known from eastern Mexico and northwards through Texas to south central Washington. These haplotypes show some range overlap in Texas, Kansas and Nebraska. The haplotypes are not yet known to elicit biological differences in the plant or insect hosts. These apparently stable haplotypes suggest separate bacterial populations of long standing. © 2011 KNPV.

Raynes J.K.,University of Canterbury | Pearce F.G.,University of Canterbury | Meade S.J.,Plant and Food Research | Gerrard J.A.,University of Canterbury
Biotechnology Progress | Year: 2011

Organophosphate hydrolase has potential as a bioremediation and chemical detoxification enzyme, but the problems of reusability and stability need to be addressed to use this enzyme on an industrial scale. Immobilizing the enzyme to a nanoscaffold may help to solve these problems. Amyloid fibrils generated from insulin and crystallin provided a novel nanoscaffold for the immobilization of organophosphate hydrolase, using glutaraldehyde as the crosslinking reagent. Electrophoretic, centrifugation, and temperature stability experiments, together with transmission electron microscopy were undertaken to verify that crosslinking had successfully occurred. The resulting fibrils remained active towards the substrate paraoxon and when immobilized to the insulin amyloid fibrils, the enzyme exhibited a significant (∼300%) increase in the relative temperature stability at 40, 45, and 50°C (as measured by comparing the initial enzyme activity to the activity remaining after heating), compared to free enzyme. This confirms that amyloid fibrils could provide a new type of nanoscaffold for enzyme immobilization. © 2010 American Institute of Chemical Engineers.

Gadd J.B.,University of Canterbury | Tremblay L.A.,Landcare Research | Northcott G.L.,Plant and Food Research
Environmental Pollution | Year: 2010

Agricultural wastes are a source of steroid estrogens and, if present, conjugated estrogens may add to the estrogen load released to soil and aquatic environments. Dairy shed effluent samples were collected from 18 farms for analysis of steroid estrogens by GC-MS, conjugated estrogens by LC-MS-MS, and estrogenic activity by E-screen in vitro bioassay. 17α-estradiol was found at highest concentrations (median 730 ng l-1), followed by estrone (100 ng l-1) and 17β-estradiol (24 ng l-1). Conjugated estrogens (estrone-3-sulfate, 17α-estradiol-3-sulfate and 17β-estradiol-3,17-disulfate) were measured in most samples (12-320 ng l-1). Median estrogenic activity was 46 ng l-1 17β-estradiol equivalents. Conjugated estrogens contributed up to 22% of the total estrogen load from dairy farming, demonstrating their significance. Steroid estrogens dominated overall estrogenic activity measured in the samples. Significantly, 17α-estradiol contributed 25% of overall activity, despite potency 2% that of 17β-estradiol, highlighting the importance in environmental risk assessments of this previously neglected compound. © 2009 Elsevier Ltd. All rights reserved.

Kim D.-G.,Landcare Research | Hernandez-Ramirez G.,Plant and Food Research | Giltrap D.,Landcare Research
Agriculture, Ecosystems and Environment | Year: 2013

Rising atmospheric concentrations of nitrous oxide (N2O) contribute to global warming and associated climate change. It is often assumed that there is a linear relationship between nitrogen (N) input and direct N2O emission in managed ecosystems and, therefore, direct N2O emission for national greenhouse gas inventories use constant emission factors (EF). However, a growing body of studies shows that increases in direct N2O emission are related by a nonlinear relationship to increasing N input. We examined the dependency of direct N2O emission on N input using 26 published datasets where at least four different levels of N input had been applied. In 18 of these datasets the relationship of direct N2O emission to N input was nonlinear (exponential or hyperbolic) while the relationship was linear in four datasets. We also found that direct N2O EF remains constant or increases or decreases nonlinearly with changing N input. Studies show that direct N2O emissions increase abruptly at N input rates above plant uptake capacity. The remaining surplus N could serve as source of additional N2O production, and also indirectly promote N2O production by inhibiting biochemical N2O reduction. Accordingly, we propose a hypothetical relationship to conceptually describe in three steps the response of direct N2O emissions to increasing N input rates: (1) linear (N limited soil condition), (2) exponential, and (3) steady-state (carbon (C) limited soil condition). In this study, due to the limited availability of data, it was not possible to assess these hypothetical explanations fully. We recommend further comprehensive experimental examination and simulation using process-based models be conducted to address the issues reported in this review. © 2012 Elsevier B.V..

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