Although the toxic effects of cyanotoxins on animals have been examined extensively, little research has focused on their effects on higher plants and macroalgae, and the potential for ...bioaccumulation in the food web through plants. Two aquatic plants,
Lemna minor and
Wolffia arrhiza, and one filamentous alga,
Chladophora fracta, were exposed to the cyanotoxin microcystin-LR. Growth of
L. minor (as weight and frond number) and root length were significantly reduced and peroxidase activity was significantly increased after 5 days of exposure to concentrations of 10 and 20
μg
mL
−1 microcystin-LR. Growth of
W. arrhiza (as frond number) was significantly reduced after 5 days of exposure to 15
μg
mL
−1 microcystin-LR. Growth and peroxidase activity of
C. fracta were not affected by microcystin-LR at concentrations up to 10
μg
mL
−1.
L. minor also accumulated microcystin-LR up to a concentration of 0.288±0.009
ng
mg
−1 wet wt. plant material over the 5 days of the experiment, equivalent to an accumulation rate of 0.058
ng
mg
−1
day
−1.
C. fracta accumulated a microcystin-LR concentration of 0.042±0.015
ng
mg
−1 wet wt. plant material over the 5 days of the experiment, equivalent to an accumulation rate of 0.008
ng
mg
−1
day
−1.
Although the toxic effects of cyanotoxins on animals have been examined extensively, little research has focused on their effects on macrophytes and macroalgae. To date only microcystins have been ...found to be detrimental to aquatic plants. Peroxidase activity of the free floating aquatic plant
Lemna minor and the filamentous macroalga
Chladophora fracta was measured after exposure to several concentrations of the cyanotoxin, anatoxin-a. Peroxidase activity (POD) was significantly (
P<0.05) increased after 4 days of exposure to an anatoxin-a concentration of 25
μg
mL
−1 for both
L. minor and
C. fracta. Peroxidase activity was not significantly increased at test concentrations of 15
μg
mL
−1 or lower. In another experiment, the effects of various concentrations of anatoxin-a on the detoxication enzyme, glutathione S-transferase (GST) in
L. minor were investigated. GST activity was significantly elevated at anatoxin-a concentrations of 5 and 20
μg
mL
−1. Photosynthetic oxygen production by
L. minor was also found to be reduced at these concentrations. This is the first report to our knowledge of the cyanotoxin anatoxin-a being harmful to aquatic plants.
OBJECTIVES
We sought to define the therapeutic dose range of levosimendan in patients with New York Heart Association class II-IV heart failure of ischemic origin.
BACKGROUND
Levosimendan is a ...calcium sensitizer for treatment of acute decompensated heart failure.
METHODS
A double-blind, placebo-controlled, randomized, multicenter, parallel-group study included 151 adult patients. Levosimendan was given as a 10-min intravenous bolus of 3, 6, 12, 24 or 36 μg/kg, followed by a 24-h infusion of 0.05, 0.1, 0.2, 0.4 or 0.6 μg/kg/min, respectively. Dobutamine, for comparative purposes, was given as an open-label infusion (6 μg/kg/min). The primary efficacy variable was the proportion of patients achieving in each treatment group at least one of the following: 1) a ≥15% increase in stroke volume (SV) at 23 h to 24 h; 2) a ≥25% decrease in pulmonary capillary wedge pressure (PCWP) (and ≥4 mm Hg) at 23 h to 24 h; 3) a ≥40% increase in cardiac output (CO) (with change in heart rate HR <20%); 4) a ≥50% decrease in PCWP during two consecutive measurements.
RESULTS
The response rate to levosimendan ranged from 50% at the lowest dose to 88% at the highest dose (compared with placebo 14%, dobutamine 70%). A dose-response relationship was demonstrated for levosimendan on increases in CO and SV, and reductions in PCWP during the infusion (for all, p ≤ 0.001). Headache (9%), nausea (5%) and hypotension (5%) were the most frequently reported adverse events at higher dosages.
CONCLUSIONS
Dosing of levosimendan with a 10-min bolus of 6 to 24 μg/kg followed by an infusion of 0.05 to 0.2 μg/kg/min is well tolerated and leads to favorable hemodynamic effects.
Real-world observational datasets that record and quantify pressure-stressor-response linkages between effluent discharges and natural aquatic systems are rare. With global wastewater volumes ...increasing at unprecedented rates, it is urgent that the present dataset is available to provide the necessary information about microbial community structure and functioning. Field studies were performed at two time-points in the Austral summer. Single-species and microbial community whole effluent toxicity (WET) testing was performed at a complete range of effluent concentrations and two salinities, with accompanying environmental data to provide new insights into nutrient and organic matter cycling, and to identify ecotoxicological tipping points. The two salinity regimes were chosen to investigate future scenarios based on a predicted salinity increase at the study site, typical of coastal regions with rising sea levels globally. Flow cytometry, amplicon sequencing of 16S and 18S rRNA genes and micro-fluidic quantitative polymerase-chain reactions (MFQPCR) were used to determine chlorophyll-a and total bacterial cell numbers and size, as well as taxonomic and functional diversity of pelagic microbial communities. This strong pilot dataset could be replicated in other regions globally and would be of high value to scientists and engineers to support the next advances in microbial ecotoxicology, environmental biomonitoring and estuarine water quality modelling.
Understanding longitudinal variation in water quality along rivers and how they are influenced by large dams is important for both ecological theory and river management. This study examines ...longitudinal changes in water quality downstream of a large bottom release dam (Lake Copeton) on the Gwydir River, Australia. We compared longitudinal changes in water quality variables from sites upstream and downstream of Lake Copeton over a two-year period and a total river distance of approximately 200 km. Lake Copeton acted as a source of nitrogen as nitrogen oxides (NO
x
) and phosphorus as filterable reactive phosphorus (FRP). A significant increase in the concentration of NO
x
and FRP was evident downstream of the dam, particularly in summer with elevated concentrations detected up to 60 km downstream. Significantly lower chlorophyll a (Chl-a) concentrations and electrical conductivity (EC) were evident below the dam. Mean nutrient concentrations declined with increased distance downstream of Lake Copeton while Chl-a concentrations increased, suggesting uptake by autotrophs. This study suggests that Copeton Dam disrupts the river continuum for nutrients, Chl-a and EC as predicted by the serial discontinuity concept, with recovery occurring approximately 60 km downstream.
•We present a new method for water quality management with remotely sensed water temperature.•Testing of the method in both Chinese and Australian rivers suggested a well-performed method.•Comparison ...with previous models revealed its practicability and effectiveness.•It can be easily applied to rivers with insufficient ground observations worldwide.
Globally, water quality degradation severely threatens the security of water resources. Understanding a river’s capacity to accommodate pollutants (or water environmental capacity: WEC) can help efficiently protect rivers. However, the requirement for comprehensive ground-observed hydrological and water quality data in previous methods makes it difficult to estimate WEC in areas with limited ground observations. This paper proposes a new framework for WEC estimation in data-scarce areas based on remotely sensed skin water temperature and limited ground observations. Two new models were developed to calculate the two critical parameters for WEC estimation: water temperature, and integrated pollutant degradation coefficients (k). Images of ASTER Surface Kinetic Temperature (AST_08) 90 m grid product were used to retrieve water temperatures. The above results were subsequently used to calculate a river’s capacity to accommodate pollutants, or WEC, in agriculturally dominated areas. The use of remote sensing techniques enables the methods to be applied over large spatial scales and to areas with limited ground observations. The application and testing of the framework in four rivers, including two Chinese rivers (the Huai and the Wei Rivers) and two Australian rivers (the Ovens and the Gwydir Rivers), suggest that the models performed well to calculate the real-time water temperature and the coefficient k based on limited ground-observations. Uncertainty analysis on water temperature calculated from remotely sensed land surface temperature and ground-observed meteorological air temperature suggests that remotely sensed water temperature had high concurrence with ground observations (RMSE = 3.08 °C with R2 = 0.88), while the sparse-spatially distributed meteorological stations reduced the accuracy in estimating water temperature (RMSE = 4.39 °C with R2 = 0.91). We found that the coefficient (k) increased with water temperature over different seasons in an exponential form but in a logarithmical form with streamflow velocity. Comparison with previous research and other models with abundant data revealed the practicability and effectiveness of our models, which can be easily applied to rivers with insufficient ground observations across the globe.
Water cycles are changing because of human population growth and climate change. Such changes will affect fundamental system-level characteristics that in turn will greatly influence ecosystem form ...and functioning. Here, a collection of papers is offered that furthers our understanding of cause and effect relationships between altered hydrology and various ecosystem properties. Combined, these papers address issues related to inflows, connectivity, and circulation and vertical mixing. In regards to altered inflows, this collection of papers addresses how seagrass bed communities, incidence of some haptophyte harmful algal blooms, and biodiversity of intermittently flowing streams might respond. These papers also address factors that influence connectivity in wetlands, and in the case of a lake and its neighboring wetland, how connectivity between systems can profoundly affect ecosystem form and functioning. Finally, the effects of altered circulation and vertical mixing are addressed as they relate to the spread of some cyanobacteria blooms to higher latitudes. The reader of this collection of papers gains a better appreciation of how ecosystem form and functioning is influenced by hydrologic processes and can conclude that there is a need for continued research in this area to better understand the impacts of human population growth and climate change.
PDF
