•Growth potential of Australasian snapper, an important New Zealand fishery, is still not fully understood.•Yellow-eyed mullet is a different ecotype, with a low economical profile but with a unique ...growth strategy.•Fish were fed ad libitum for a year to determine maximum potential growth rates (GR) and seasonality in growth dynamics.•Snapper grew strictly seasonal while mullet, due to unlimited food grew linearly undermining seasonal effects.•Snapper maximum GR may increase with further temperature rise, while mullet best grew at 17/18 °C.
Seasonality can have a major influence on growth dynamics of temperate teleosts that alternates between sustaining the maximum growth performance and confining it to its minimum. Yet the effects may not always be easily discernible, and species use different strategies to deal with annual oscillation in environmental variables. In this comparative study carried out in New Zealand snapper (Chrysophrys auratus) and yellow-eyed mullet (Aldrichetta forsteri) were exposed to seasonal conditions for 12 months under an ad libitum feeding regime to investigate whether an unrestricted diet can produce a clear seasonal response in their growth profile and, assuming that food is limiting in the wild, what would be their maximum potential growth rates. Data showed a strong seasonal effect on growth parameters and energy partitioning in snapper, whereas there were no seasonal dependent responses in mullet. Snapper showed exponential growth during the warm period and the opposite was evident in winter when growth ceased and become even negative. Mullet grew steadily all year around with only a slight deflection from the linear growth trajectory in winter. Snapper’s maximum growth rates corresponded with the highest ambient temperature in the peak of summer. Therefore, this study was not able to determine the maximum potential growth rates for snapper as it would possibly increase with further temperature rise. In contrast, mullet appeared to grow fastest at ∼17/18 °C. In terms of fish condition – snapper partitioned resources to maximise winter survival by switching from investment into growth to energy stores on transition between autumn and winter, whereas yellow-eyed mullet focused on maximising accumulation of visceral fat to reach optimal levels of ∼15 % body mass, which was independent of environmental temperature. Results from this study suggest that wild length-based growth rates in mullet may indeed be feed limited, whereas this cannot be suggested for wild snapper.
The ability of WHAM VII and NICA-Donnan models to predict free-ion activities of Cu in natural waters was examined from two perspectives, (i) the presence of EDTA and NTA contaminants, (ii) the need ...to improve estimates of HA and FA concentrations. Potentiometric responses of a Cu(II) ion-selective electrode were investigated in five assays containing dissolved organic matter (DOM) isolated from a series of polluted (urban) and relatively unpolluted (upland) streams in northern England. The Cu/DOC ratio in these assays spanned an environmentally realistic range of ∼1–500 μmol/g. Reasonably good agreement between measured and predicted Cu2+ activities was obtained with both WHAM VII and NICA-Donnan models, assuming 65% of DOM as fulvic acid and including the measured EDTA and NTA concentrations, but generally the models overestimated the activities by a factor of ∼2. In contrast, the models over-predicted the Cu2+ activities by up to 2 orders of magnitude at low Cu/DOC ratios in urban waters if anthropogenic ligands were not included in the model simulations. Three-dimensional fluorescence excitation–emission matrix (EEM) spectroscopy was used to measure the functional properties of the isolated DOM and to estimate the fractions of FA and HA present. Using these fractions in the models gave improvements in predictions compared to the 65% FA assumption, as shown by higher correlations, reduced error and reduced bias. These results highlight various issues with the use of the available speciation models for predicting free ion concentrations in natural waters, such as the use of the Biotic Ligand Model (BLM) for the derivation of environmental standards. It is clearly necessary to measure EDTA and NTA in waters with urban influences, while fluorescence measurements offer the possibility of appreciably improving the accuracy of predictions.
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•We report a new approach for representing reactive DOM in speciation calculations.•Fluorescence EEM provides a proxy for DOM components in different aqueous conditions.•Fluorescence-derived DOM as model input enabled Cu-speciation with improved accuracy.•Our new approach represents a way to overcome the problem of DOM natural variability.•Anthropogenic ligands coexisting with DOM are sources of errors in chemical speciation.
Previous studies on metabolic responses to feeding (i.e. the specific dynamic action, SDA) in Antarctic fishes living at temperatures below zero have reported long-lasting increases and small peak ...responses. We therefore hypothesized that the postprandial hyperemia also would be limited in the Antarctic fish Pagothenia borchgrevinki. The proportion of cardiac output directed to the splanchnic circulation in unfed fish was 18%, which is similar to temperate fish species. Contrary to our prediction, however, gastrointestinal blood flow had increased by 88% at twenty four hours after feeding due to a significant increase in cardiac output and a significant decrease in gastrointestinal vascular resistance. While gastric evacuation time appeared to be longer than in comparable temperate species, digestion had clearly commenced twenty four hours after feeding as judged by a reduction in mass of the administered feed. Even so, oxygen consumption did not increase suggesting an unusually slowly developing SDA. Adrenaline and angiotensin II was injected into unfed fish to investigate neuro-humoral control mechanisms of gastrointestinal blood flow. Both agonists increased gastrointestinal vascular resistance and arterial blood pressure, while systemic vascular resistance was largely unaffected. The hypertension was mainly due to increased cardiac output revealing that the heart and the gastrointestinal vasculature, but not the somatic vasculature, are important targets for these agonists. It is suggested that the apparently reduced SDA in P. borchgrevinki is due to a depressant effect of the low temperature on protein assimilation processes occurring outside of the gastrointestinal tract, while the gastrointestinal blood flow responses to feeding and vasoactive substances resemble those previously observed in temperate species.
Analysis of the dynamic features of diffusion gradients in thin film devices (DGT) indicates that the penetration of complexes into the resin layer dramatically increases their lability. This should ...be taken into account when interpreting DGT measurements in terms of the dynamics of solution speciation. The experimental accumulation of Cd by DGT sensors in Cd-NTA systems confirmed these theoretical analyses. A computational code, which allows a rigorous digital simulation of the diffusion-reaction processes in the gel and resin layers, was used to model the results and to demonstrate the effect of the complex penetration into the resin layer on the lability degree. These findings suggest that DGT renders all complexes much more labile than if the resin-diffusive gel interface was considered as a perfect planar sink, explaining why DGT often measures a high proportion of the metal in a natural water. This information is relevant since some studies have stressed the importance of labile complexes as a source of bioaccumulated metal.
Increasing blood pressure variability has been reported following acute stroke, but there is uncertainty about how best to measure it and about the impact on prognosis following acute ischaemic ...stroke and transient ischaemic attack.
Enhanced casual blood pressure and ambulatory blood pressure monitoring were completed at baseline (≤48 h post symptom onset). Blood pressure variability was defined by standard deviation and coefficient of variation of systolic, diastolic, mean arterial pressure, and pulse pressure. Modified Rankin scale score ≥3 described poor functional outcome assessed at 1- and 12-months post-stroke. Multivariable logistic regression models incorporating blood pressure variability measurement and other factors were performed, and odds ratio and 95% confidence intervals reported.
232 patients were recruited; 45 were dependent at 1-month, and 37 at 12-months. Dependent patients were more likely to be older, with a higher burden of pre-morbid conditions, and with increased blood pressure variability. Enhanced casual standard deviations of diastolic blood pressure 1.19 (1.02 to 1.39) and mean arterial pressure 1.20 (1.00 to 1.43) predicted dependency at 1-month. Predictors of 12-month dependency included: enhanced casual standard deviation of mean arterial pressure 1.21 (1.0-1.46); 24 h ambulatory monitor standard deviations of diastolic blood pressure 2.30 (1.08-4.90) and mean arterial pressure 1.72 (1.09-2.72), and the coefficient of variation of mean arterial pressure 1.76 (1.05-2.94); day-time ambulatory monitor coefficient of variation of systolic blood pressure 1.44 (1.02-2.03) and mean arterial pressure 1.46 (1.02-2.08); and night-time ambulatory standard deviation of diastolic blood pressure 1.65 (1.03 -2.63), and the coefficient of variation of mean arterial pressure and 1.38 (1.00- 1.90) and pulse pressure 1.29 (1.00–1.65).
Increasing blood pressure variability is independently and modestly associated with poor functional outcome at 1- and 12-months following acute stroke.
Antarctic marine organisms are considered to have extremely limited ability to respond to environmental temperature change. However, here we show that the Antarctic notothenioid fish
Pagothenia ...borchgrevinki
is an exception to this theory.
P. borchgrevinki
was able to acclimate its resting metabolic rate and resting ventilation frequency after a 5°C rise in temperature. Acute exposure to 4°C resulted in an elevation in metabolic rate (57.8 ± 4.79 mg O
2
kg
−1
h
−1
) and resting ventilation rate (40.38 ± 1.61 breaths min
−1
) compared with fish at −1°C (metabolic rate 34.45 ± 3.12 mg O
2
kg
−1
h
−1
; ventilation rate 29.88 ± 3.72 breaths min
−1
). However, after a 1-month acclimation period, there was no significant difference in the metabolic rate (cold fish 29.52 ± 3.01; warm fish 31.13 ± 2.30 mg O
2
kg
−1
h
−1
), or the resting ventilation rate (cold fish 28.75 ± 0.98; warm fish 34.25 ± 2.28 breaths min
−1
) of cold and warm acclimated fish. Acclimation changes to the rate of oxygen consumption following exhaustive exercise were complex. The pattern of oxygen consumption during recovery from exhaustive exercise was not significantly different in either cold or warm acclimated fish.
Penetration of complexes into the resin layer can dramatically increase the contribution of complexes to the metal flux measured with a DGT (diffusive gradients in thin films) sensor, but equations ...to describe this phenomenon were not available. Here, simple approximate analytical expressions for the metal flux, the lability degree and the concentration profiles in a DGT experiment are reported. Together with the thickness of the reaction layer in the gel domain, the effective penetration distance into the resin layer that would be necessary for full dissociation of the complex (λ(ML)) plays a key role in determining the metal flux. An increase in the resin-layer thickness (r) effectively increases the metal flux and the lability degree until r ≈ 3λ(ML). For the usual DGT configuration, where the thickness of the gel layer exceeds that of the resin layer, the complex is labile if r > (D(ML)/k(d))½, where D(ML) is the diffusion coefficient of the metal complex and k(d) its dissociation rate constant. A general procedure for estimating the lability of any complex in a standard DGT configuration is provided.
Measurements of trace metal species in situ in a softwater river, a hardwater lake, and a hardwater stream were compared to the equilibrium distribution of species calculated using two models, WHAM ...6, incorporating humic ion binding model VI and visual MINTEQ incorporating NICA-Donnan. Diffusive gradients in thin films (DGT) and voltammetry at a gel integrated microelectrode (GIME) were used to estimate dynamic species that are both labile and mobile. The Donnan membrane technique (DMT) and hollow fiber permeation liquid membrane (HFPLM) were used to measure free ion activities. Predictions of dominant metal species using the two models agreed reasonably well, even when colloidal oxide components were considered. Concentrations derived using GIME were generally lower than those from DGT, consistent with calculations of the lability criteria that take into account the smaller time window available forthe fluxto GIME. Model predictions of free ion activities generally did not agree with measurements, highlighting the need for further work and difficulties in obtaining appropriate input data.
Concentrations of Al, Fe, Mn, Ni, Cu, Cd, Pb, and Zn were measured using DGT (diffusive gradients in thin-films) devices deployed in situ in 34 headwater streams in Northern England. Mean values of ...filtered samples analyzed by ICP-MS (inductively coupled plasma mass spectrometry) were used, along with DOC (dissolved organic carbon), pH and major ions, to calculate the distribution of metal species using the speciation code WHAM. DGT-measured concentrations, MeDGT, of Zn and Cd were generally similar to concentrations in filtered samples, Mefilt. For the other metals, MeDGT was similar to or lower than Mefilt. Calculation of the maximum dynamic metal from the speciation predicted using WHAM showed that most of the lower values of CuDGT could be attributed to the dominance of Cu-fulvic acid complexes, which diffuse more slowly than simple inorganic species. Similar calculations for Al, Pb, and Mn were consistent with appreciable proportions of these metals being present as colloids that are not simple complexes with humic substances. Differences between WHAM predictions and the measured NiDGT indicated that WHAM used with the default binding parameters underestimates Ni binding to natural organic matter. Plots of MeDGT versus the ratio of bound metal to DOC provided slight evidence of heterogeneous binding of Pb and Cu, while results for Mn, Cd, and Zn were consistent with weak binding and complete lability.
Several techniques for speciation analysis of Cu, Zn, Cd, Pb, and Ni are used in freshwater systems and compared with respect to their performance and to the metal species detected. The analytical ...techniques comprise the following: (i) diffusion gradients in thin-film gels (DGT); (ii) gel integrated microelectrodes combined to voltammetric in situ profiling system (GIME-VIP); (iii) stripping chronopotentiometry (SCP); (iv) flow-through and hollow fiber permeation liquid membranes (FTPLM and HFPLM); (v) Donnan membrane technique (DMT); (vi) competitive ligand-exchange/stripping voltammetry (CLE-SV). All methods could be used both under hardwater and under softwater conditions, although in some cases problems with detection limits were encountered at the low total concentrations. The detected Cu, Cd, and Pb concentrations decreased in the order DGT > or = GIME-VIP > or = FTPLM > or = HFPLM approximately = DMT (>CLE-SV for Cd), detected Zn decreased as DGT > or = GIME-VIP and Ni as DGT > DMT, in agreement with the known dynamic features of these techniques. Techniques involving in situ measurements (GIME-VIP) or in situ exposure (DGT, DMT, and HFPLM) appear to be appropriate in avoiding artifacts which may occur during sampling and sample handling.
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