Interactions between a planktivorous fish and planktonic microcrustaceans mediated by the biomass of aquatic macrophytes

2021 ◽  
Author(s):  
Bárbara Angélio Quirino ◽  
Franco Teixeira de Mello ◽  
Sabrina Deosti ◽  
Claudia Costa Bonecker ◽  
Ana Lúcia Paz Cardozo ◽  
...  
Keyword(s):  
Aquatic Macrophyte ◽  
Plant Biomass ◽  
Flow Speed ◽  
Trophic Niche ◽  
Planktivorous Fish ◽  
Low Flow ◽  
High Biomass ◽  
Predator Prey ◽  
Cladoceran Species ◽  
Macrophyte Biomass

Abstract Habitat complexity is recognized to mediate predator–prey relationships by offering refuge or not. We investigated the availability of planktonic microcrustaceans and the diet of a planktivorous fish (Hyphessobrycon eques) at different levels (low, intermediate and high) of aquatic macrophyte biomass. Sampling was carried out in a river with low flow speed, located in a Neotropical floodplain. We collected fish and microcrustaceans in macrophyte stands with variations in biomass. There were no differences in microcrustacean density in the water among the levels of macrophyte biomass, but microcrustacean richness and diet composition of H. eques differed. Microcrustacean richness and trophic niche breadth of the planktivorous fish were higher in high biomass stands. There was high consumption of a small cladoceran species in low macrophyte biomass, which was replaced by larger species, such as copepods, in intermediate and high biomass. Thus, the selection of some species was different among the biomass levels. These results suggest that plant biomass plays an important role in the interaction between fish and microcrustaceans, and prey characteristics such as size, escape ability and energy value make them more or less subject to predation by fish according to habitat structuring.

The recovery and dynamics of submerged aquatic macrophyte vegeta­tion in the Wilderness lakes, southern Cape

Bothalia ◽  
1992 ◽  
Vol 22 (2) ◽  
pp. 283-288 ◽  
Author(s):  
P. J. Weisser ◽  
A. K. Whitfield ◽  
C. M. Hall
Keyword(s):  
Species Composition ◽  
Seasonal Changes ◽  
Aquatic Macrophyte ◽  
Plant Biomass ◽  
Plant Populations

Between 1979 and 1981, the submerged aquatic macrophyte vegetation in the Wilderness lakes died back significantly, and in some areas disappeared altogether. This study documents the senescent phase and describes the recovery of the plant populations between May 1982 and May 1983. In two lakes, namely Langvlei and Eilandvlei, the plant biomass approximately doubled between the winters of 1982 and 1983. Seasonal changes in species composition are documented and possible factors accounting for the collapse and recovery of the plant populations are discussed.

An analysis of primary production in the Daly River, a relatively unimpacted tropical river in northern Australia

2005 ◽  
Vol 56 (3) ◽  
pp. 303 ◽  
Author(s):  
I. T. Webster ◽  
N. Rea ◽  
A. V. Padovan ◽  
P. Dostine ◽  
S. A. Townsend ◽  
...  
Keyword(s):  
Primary Production ◽  
Plant Biomass ◽  
Net Primary Production ◽  
Low Flow ◽  
Nutrient Concentrations ◽  
Tight Coupling ◽  
Tropical River ◽  
Rate Of Photosynthesis ◽  
Curve Method ◽  
Tropical Australia

In this paper, the dynamics of primary production in the Daly River in tropical Australia are investigated. We used the diurnal-curve method for both oxygen and pH to calculate photosynthesis and respiration rates as indicators of whole-river productivity. The Daly River has maximum discharges during the summer, monsoonal season. Flow during the dry season is maintained by groundwater discharge via springs. The study investigated how primary production and respiration evolve during the period of low flow in the river (April–November). The relationship between primary production and the availability of light and nutrients enabled the role of these factors to be assessed in a clear, oligotrophic tropical river. The measured rate of photosynthesis was broadly consistent with the estimated mass of chlorophyll associated with the main primary producers in the river (phytoplankton, epibenthic algae, macroalgae, macrophytes). A significant result of the analysis is that during the time that plant biomass re-established after recession of the flows, net primary production proved to be ~4% of the rate of photosynthesis. This result and the observed low-nutrient concentrations in the river suggest a tight coupling between photosynthetic fixation of carbon and the microbial degradation of photosynthetic products comprising plant material and exudates.

Measurement of the Instantaneous Velocity Gradients in Plane and Axisymmetric Turbulent Wake Flows

2001 ◽  
Vol 124 (1) ◽  
pp. 143-153 ◽  
Author(s):  
T. Schenck ◽  
J. Jovanovic´
Keyword(s):  
Correction Method ◽  
Flow Speed ◽  
Low Flow ◽  
Sphere Diameter ◽  
Hot Wire ◽  
Local Isotropy ◽  
Plane Wake ◽  
Good Spatial Resolution ◽  
Pressure Transport ◽  
Derivatives Of

All first-order spatial derivatives of the turbulent velocity fluctuations were measured using a pair of X hot-wire probes. Measurements were performed in the self-preserving region of a turbulent plane wake downstream of a cylinder and in an axisymmetric wake behind the sphere. Good spatial resolution of the measurements was ensured by choosing small values for the cylinder/sphere diameter and a low flow speed. Errors due to the finite hot-wire length and the wire and probe separation were analyzed using Wyngaard’s correction method. The derived corrections were verified experimentally. The measuring technique and the experimental results were systematically checked and compared with the results available in the literature. The assumptions of local isotropy and local axisymmetry were examined. Both investigated flows deviate only moderately from local isotropy and local axisymmetry. Support for the measured results is provided by plotting the data on an anisotropy invariant map. The budgets of the turbulent kinetic energy were computed from the measured data. In contrast to the results obtained in the plane wake, where the pressure transport is nearly negligible, in the axisymmetric wake it was found to play an important role and closely follows the estimate made by Lumley, uip¯/ρ≈−0.2q2ui¯.

scholarly journals Determination of best groyne combination for mitigating bank erosion

2019 ◽  
Vol 21 (5) ◽  
pp. 875-892
Author(s):  
Kaushik Bora ◽  
Hriday Mani Kalita
Keyword(s):  
Optimization Model ◽  
Optimization Problem ◽  
Bank Erosion ◽  
Flow Speed ◽  
Low Flow ◽  
Test Cases ◽  
Meandering Channel ◽  
Novel Approach

Abstract This paper presents a novel approach for determining the best combination of groynes in terms of their number, lengths and positions for controlling bank erosion. The vulnerable bank is considered to be protected if a very small value of water flow speed is achieved on the near bank area. A linked simulation–optimization model is developed in this regard which minimizes the total construction cost of the groyne project. At the same time, a constraint in terms of low flow speed in a predefined zone is incorporated, which helps in bank erosion prevention. In the simulation model, the depth-averaged shallow water equations are solved using a finite difference scheme. The optimization problem is formulated in three different approaches to tackle different types of in situ field problems. Genetic algorithm (GA) is used to solve the optimization problem. The proposed optimization model is used in two hypothetical test cases including one straight channel and one meandering channel. The results obtained with all the three formulations are found to be logical and establish the potential of the present model for application in real cases.

Fluoride removal from aqueous solution by Ca-pretreated macrophyte biomass

2008 ◽  
Vol 5 (1) ◽  
pp. 68 ◽  
Author(s):  
Patricia Miretzky ◽  
Carolina Muñoz ◽  
Alejandro Carrillo-Chávez
Keyword(s):  
Aqueous Solution ◽  
Developing Countries ◽  
Drinking Water ◽  
Sorption Capacity ◽  
Aquatic Macrophyte ◽  
Low Cost ◽  
Isotherm Models ◽  
Fluoride Removal ◽  
Natural Material ◽  
Macrophyte Biomass

Environmental context. Fluoride concentrations in drinking water above 1.5 mg L–1 may be detrimental to human health. Many methods have been developed for removing excessive fluoride from drinking water. The use of an aquatic macrophyte biomass (Eleocharis acicularis) pretreated with Ca2+, a low-cost natural material, could be a technique for rural populations in developing countries that cannot afford treated or bottled water for daily consumption. Abstract. The use of an aquatic macrophyte biomass (Eleocharis acicularis) pretreated with Ca2+ as a low-cost natural material for the removal of fluoride from aqueous solution was studied. Batch experiments were carried out to determine fluoride sorption capacity and the efficiency of the sorption process under different pH, initial F– and macrophyte biomass doses. The experimental data showed good fitting to Langmuir and Freundlich isotherm models. The maximum F adsorption capacity was 0.110 mmol g–1 with an efficiency of 64.5% (pH 6.0; 5.0 g L–1 Ca-pretreated biomass). The binding of Ca2+ to the biomass increased the removal efficiency over 100%. The F– removal kinetics were rapid, less than 30 min, and best described by the pseudo-second order rate model. The rate constant, the initial sorption rate and the equilibrium sorption capacity were determined. These results may be useful for deprived rural population water supply schemes in Mexico and in other developing countries.

scholarly journals Nature Conservation Against All? Aquatic Macrophyte De-Weeding – Cut or Conserve? A Stakeholder Analysis

2017 ◽  
Vol 54 ◽  
pp. 1-14 ◽  
Author(s):  
Vasco Brummer ◽  
Sandra Roth ◽  
Markus Röhl ◽  
Carsten Herbes
Keyword(s):  
Nature Conservation ◽  
Aquatic Macrophyte ◽  
Plant Biomass ◽  
Biogas Production ◽  
Stakeholder Analysis ◽  
Flood Protection ◽  
Water Runoff ◽  
Water Plant

De-weeding of streams and lakes occurs in Germany on a widespread level, mostly to ensure water runoff and to provide flood protection. But de-weeding also affects a range of stakeholders, who have their own reasons to support or oppose it. For the list of stakeholders identified, see chapter 4. As part of a project analysing the feasibility of using water plant biomass as a substrate for biogas production, we conducted a multi-method stakeholder analysis to evaluate stakeholders’ opinions about de-weeding. The results show a preference of all stakeholders, except those identifying with nature conservation, for aquatic de-weeding. Our findings also point to a lack of communication between stakeholders, resulting in biased opinions of the stakeholders against other stakeholders and starting points for conflict.

Combined effects of flow speed and sub-lethal insecticide exposure on predator–prey interactions between the California killifish and an infaunal polychaete

Ecotoxicology ◽  
2018 ◽  
Vol 28 (1) ◽  
pp. 117-131 ◽  
Author(s):  
Nicholas T. Hayman ◽  
Brian T. Hentschel ◽  
Violet C. Renick ◽  
Todd W. Anderson
Keyword(s):  
Flow Speed ◽  
Combined Effects ◽  
Predator Prey ◽  
Insecticide Exposure

Hydrokinetic Vortex Induced Vibration (VIV) Energy Harvester

2020 ◽  
Author(s):  
Xiaoyu Zhou ◽  
Vesselina Roussinova ◽  
Vesselin Stoilov
Keyword(s):  
Bluff Body ◽  
Energy Harvester ◽  
Electrical Energy ◽  
Average Frequency ◽  
Flow Speed ◽  
Peak Amplitude ◽  
Low Flow ◽  
Bluff Bodies ◽  
Vortex Induced Vibration ◽  
Low Speed

Abstract This paper investigates the performance of vortex-induced vibration (VIV) energy harvester in low-speed water flow. The proposed VIV harvester is extracting hydrokinetic energy from the flowing current and transferring it into mechanical vibrations. The vibrations are further converted into electrical energy using the piezoelectric transducer to supply the modern demand for energy-consumption. To meet the demand, the single harvester is analyzed to determine the suitable geometry for the bluff body that is sensitive to the low-speed flow. Furthermore, the converter must be able to harvest vibrations of varying amplitudes and frequencies. To maximize the power output, different array configurations of multiple bluff bodies are examined. A single positively buoyant elastically mounted cylinder is tested experimentally and at a low flow speed of 0.3 m/s, it can harvest vibrations with an average frequency of 1.8 Hz and peak to peak amplitude of 1.5d, where d is the diameter of the bluff body. It was found that for an array consisting of ten bluff bodies, the average frequency and peak to peak amplitude increases to 2.09Hz and 1.54d, respectively.

Stability and Dynamic Evolution of Sliding Fluid-Transporting Pipes in Three-Dimensional Sense

2020 ◽  
Vol 20 (03) ◽  
pp. 2050036
Author(s):  
Xiping Sun ◽  
Hao Yan ◽  
Huliang Dai
Keyword(s):  
Flow Velocity ◽  
Three Dimensional ◽  
Flow Speed ◽  
Low Flow ◽  
Single Type ◽  
Dynamic Evolution ◽  
Transient Vibration ◽  
Aerial Refueling ◽  
Dynamic Behaviors ◽  
Conveying Fluid

This paper deals with the stability and dynamic evolution of a sliding pipe conveying fluid in the three-dimensional sense. The pipe is assumed to slide out from a fixed channel so that its free end is moving at the same time, a problem often associated with instabilities in applications of aerial refueling operation. To tackle this problem, the nonlinear governing equations of motion are derived by using the Hamilton’s principle and then reduced to a set of ordinary differential equations by the Galerkin’s method. A parametric study is performed to explore the transient vibration responses of the pipe for different values of flow velocity and sliding rate. Various dynamic behaviors are detected for the pipe in sliding and conveying fluid. The results show that 3-D oscillations of the pipe occur when the flow velocity exceeds a certain value, which can be affected by the sliding rate. For various flow velocities, the evolution of the dynamic characteristics of the sliding pipe can be classified into three typical types of motion. When at low flow velocity, the pipe is mainly subjected to a single type of 3-D motion. When the flow speed increases to high values, multi-type of 3-D motion consisting of three typical types occurs on the pipe. In addition, the pipe can display planar motions, transferring from one plane to the other. The result presented herein is helpful to understand the stabilities and dynamic behaviors of sliding-pipe systems used in aerial refueling applications.

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