Predation on tadpoles by hatchlings of the freshwater turtle

1999 ◽  
Vol 20 (2) ◽  
pp. 173-183 ◽  
Author(s):  
Mark-Oliver Rödel
Keyword(s):  
At Risk ◽  
Water Column ◽  
Body Shape ◽  
Water Levels ◽  
Freshwater Turtle ◽  
Natural Conditions ◽  
Small Prey ◽  
Regional Influence ◽  
Reduced Water

AbstractExperiments with Pelomedusa subrufa, a widespread African freshwater turtle, showed that this species consumed large quantities of tadpoles. Tadpoles preyed upon, comprised between 0.05 and 21.55% of the turtle's biomass. This demonstrated that Pelomedusa subrufa was neither gape limited nor did it ignore very small prey. Tadpoles with an ovoid body shape (Hemisus marmoratus, Hyperolius nitidulus, Ptychadena maccarthyensis), which shared, under natural conditions, the pond bottom microhabitat with the turtles, were more threatened than the robust tall-finned Kassina tadpoles that lived in the middle of the water column. The translucent, slow swimming Phrynomantis microps tadpole occurred in larger ponds and preferred the upper water column in deeper parts of the pond. This species was especially at risk in ponds with reduced water levels. Turtles, in contrast to fish or dragonfly larvae, are capable of migrating to other ponds. They therefore might have a profound regional influence on tadpole communities in ephemeral savanna ponds.

scholarly journals A Case Study of the Effects of Management Interventions on the Phosphorus Dynamics at a Coastal, Eutrophic, Caribbean lagoon (Laguna Cartagena, Puerto Rico)

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 449
Author(s):  
Yashira Marie Sánchez Colón ◽  
Fred Charles Schaffner
Keyword(s):  
Puerto Rico ◽  
Water Column ◽  
Water Levels ◽  
Wildlife Habitat ◽  
Freshwater Wetland ◽  
Water Level Fluctuations ◽  
Phosphorus Loading ◽  
Estuarine Wetlands ◽  
Management Interventions ◽  
Management Recommendations

Laguna Cartagena is a coastal, eutrophic, shallow lake and freshwater wetland in southwestern Puerto Rico, managed by the US Fish and Wildlife Service. This ecosystem has been impacted by phosphorus loading from adjacent agricultural areas since the 1950s, causing eutrophication and deteriorating wildlife habitats. Herein, we describe phosphorus input and export during September 2010–September 2011 (Phase One) and October 2013–November 2014 (Phase Two). These two phases bracket a period of intensified management interventions including excavation and removal of sediment and vegetation, draining, and burning during the summers of 2012 and 2013. Results indicate that Laguna Cartagena retains a phosphorus (sink) in its sediments, and exhibits nutrient-releasing events (source, mainly total phosphorus) to the lagoon water column, which are associated with rainfall and rising water levels. External factors including water level fluctuations and rainfall influenced phosphorus export during Phase One, but after management interventions (Phase Two), internal processes influenced sink/source dynamics, releasing elevated phosphorus concentrations to the water column. When exposed sediments were re-flooded, phosphorus concentrations to the water column increased, releasing elevated P concentrations downstream to an estuarine wetlands area and the Caribbean Sea. Herein we offer management recommendations to optimize wildlife habitat without elevating phosphorus concentrations.

scholarly journals An experimental assessment of the distribution of environmental DNA along the water column

2020 ◽  
Author(s):  
André O. Agostinis ◽  
Giorgi Dal Pont ◽  
Alexandre Borio ◽  
Aline Horodesky ◽  
Ana Paula da Silva Bertão ◽  
...  
Keyword(s):  
Water Column ◽  
Environmental Dna ◽  
Aquatic Communities ◽  
Natural Conditions ◽  
Sampling Protocol ◽  
Experimental Assessment ◽  
Qpcr Analysis ◽  
Time Period ◽  
Sampling Protocols ◽  
Different Depths

AbstractThe study of environmental DNA (eDNA) is increasingly becoming a valuable tool to survey and monitor aquatic communities. However, there are important gaps in our understanding of the dynamics governing the distribution of eDNA under natural conditions. In this report we carry out controlled experiments to assess the extent and timing of eDNA distribution along the water column. A sample of known eDNA concentration was placed at the bottom of a 5-m high tube (20 cm in diameter and total volume of 160 L), and water samples were obtained at different depths over an 8 h-period. The presence of the target eDNA was assessed by qPCR analysis. This sampling protocol allowed for assessing the timescale for the diffusion of eDNA while minimizing the influence of turbulence. We demonstrate that, after a time-period of as little as 30 min, the eDNA had spread across the entire container. The implications of these results for eDNA sampling protocols in the field are discussed.

scholarly journals High accuracy coastal flood mapping for Norway using LiDAR data

2019 ◽  
Author(s):  
Kristian Breili ◽  
Matthew James Ross Simpson ◽  
Erlend Klokkervold ◽  
Oda Roaldsdotter Ravndal
Keyword(s):  
At Risk ◽  
Sea Level Rise ◽  
Sea Level ◽  
Storm Surge ◽  
Coastal Flooding ◽  
High Accuracy ◽  
Mapping Method ◽  
Water Levels ◽  
Climate Services ◽  
Elevation Data

Abstract. Using new high accuracy Light Detection and Ranging elevation data we generate coastal flooding maps for Norway. Thus far, we have mapped ~ 80 % of the coast, for which we currently have data of sufficient accuracy to perform our analysis. Although Norway is generally at low risk from sea-level rise largely owing to its steep topography, the maps presented here show that on local scales, many parts of the coast are potentially vulnerable to flooding. There is a considerable amount of infrastructure at risk along the relatively long and complicated coastline. Nationwide we identify a total area of 400 km2, 105,000 buildings, and 510 km of roads that are at risk of flooding from a 200 year storm-surge event at present. These numbers will increase to 610 km2, 137,000, and 1340 km with projected sea-level rise to 2090 (95th percentile of RCP8.5 as recommended in planning). We find that some of our results are likely biased high owing to erroneous mapping (at least for lower water levels close to the tidal datum which delineates the coastline). A comparison of control points from different terrain types indicates that the elevation model has a root mean square error of 0.26 m and is the largest source of uncertainty in our mapping method. The coastal flooding maps and associated statistics are freely available, and alongside the development of coastal climate services, will help communicate the risks of sea-level rise and storm surge to stakeholders. This will in turn aid coastal management and climate adaption work in Norway.

Numerical Simulation of Mixed Emulsion Explosive Charging in Water-Filled-Hole

2013 ◽  
Vol 634-638 ◽  
pp. 3563-3566
Author(s):  
Hai Wang Ye ◽  
Dong Ling Nong ◽  
Ting Li ◽  
Jie Wang Ye
Keyword(s):  
Numerical Simulation ◽  
Water Column ◽  
Water Depth ◽  
Jet Flow ◽  
Hole Diameter ◽  
Water Levels ◽  
Effective Range ◽  
Emulsion Explosive ◽  
Hole Bottom

When charging in water-filled-hole with emulsion mixed loading truck, if the charging hose can not reach the borehole bottom, there will be a water column in the charge. Emulsion explosive charging in water-filled-hole is simulated under three conditions with different water levels, charging velocity and hole diameter when the hose of the explosive mixed loading truck does not reach the hole bottom. The results show that explosive can not reach the bottom of the blasthole if the water depth exceeds the maximum effective range of the jet flow, which is proportional to charging speed and hole diameter, and there will exist a water column at the bottom of the hole. To prevent that, the distance between the hose outlet and the hole bottom must be shorter than the effective range when charging. Besides, increasing charging velocity also works.

Growth, anatomy, and gas exchange of Cenostigma pluviosum cultivated under reduced water levels in iron mining tailings

2021 ◽  
Author(s):  
Alessander Lopes Caetano ◽  
Maxwell Pereira de Pádua ◽  
Marcelo Polo ◽  
Moacir Pasqual ◽  
Fabricio José Pereira
Keyword(s):  
Gas Exchange ◽  
Water Levels ◽  
Mining Tailings ◽  
Iron Mining ◽  
Reduced Water

A Case Study for Infrastructure Scour Management

2020 ◽  
Author(s):  
Eftychia Koursari ◽  
Stuart Wallace ◽  
Panagiotis Michalis ◽  
Yi Xu ◽  
Manousos Valyrakis
Keyword(s):  
At Risk ◽  
Water Levels ◽  
Bridge Engineering ◽  
Second Phase ◽  
Two Phase ◽  
Phase Approach ◽  
Remediation Measures ◽  
Stability Of Structures ◽  
Safety Inspections

<p>Scour is the leading cause of bridge collapse worldwide, being responsible for compromising the stability of structures’ foundations. Scour and erosion can take place without prior warning and cause sudden failure. This study describes engineering measures and complications encountered during construction for a case study in the Scottish Borders (A68 Galadean Bridge). The bridge studied carries the A68 road across the Leader Water.</p><p>Transport Scotland’s structures crossing or near a watercourse are subject to a two-stage scour assessment following the Design Manual for Roads and Bridges (DMRB) BD97/12 Standard, ‘The Assessment of Scour and Other Hydraulic Actions at Highway Structures’. Structures identified at risk are monitored through Reactive Structures Safety Inspections following events likely to increase water levels. The most common form of monitoring includes visual inspections, however, monitoring sensors are being currently implemented and trialled at locations at high risk of scour.</p><p>Scour in the area was identified during a Reactive Structures Safety Inspection, following which a weekly scour monitoring regime was established, alongside further Reactive Structures Safety Inspections, until remediation measures were put in place.</p><p>Despite the bridge being constructed perpendicular to the Leader Water, meandering of the watercourse was detected upstream. Sediment transport was the cause of an island formation immediately upstream of the structure. Non-uniform flow and secondary, spiral currents, resulting from the formation of the bend were exacerbating scour and erosion in the area. The design of the remediation measures included the implementation of rock rolls alongside the affected riverbank. However, during construction, increased water levels resulting from thawing snow resulted in the collapse of a significant portion of the embankment supporting the structure’s abutment and the A68 road, prior to the realisation of the remediation measures. An emergency design revision was required and emergency measures had to be enforced.</p><p>The urgency of the works led to a two-phase approach being followed for the design and construction of the scour measures in the affected area. The first phase included the construction of a platform in front of the affected road embankment and the implementation of rock rolls to provide scour protection. The two-phase approach ensured the infrastructure at risk was protected from further deterioration while the reconstruction of the embankment was being designed.</p><p>The second phase of works included the reconstruction of the affected road embankment, for which the anticipated total scour depth was taken into account.</p><p> </p><p>References:</p><p>Koursari E and Wallace S. 2019. Infrastructure scour management: a case study for A68 Galadean Bridge, UK. Proceedings of the Institution of Civil Engineers – Bridge Engineering, https://doi.org/10.1680/jbren.18.00062</p><p> </p><p>Acknowledgements:</p><p>The authors would like to acknowledge Transport Scotland for funding this project.</p>

Limnological succession in reservoirs: a paleolimnological comparison of two methods of reservoir formation

1999 ◽  
Vol 56 (6) ◽  
pp. 1109-1121 ◽  
Author(s):  
Roland I Hall ◽  
Peter R Leavitt ◽  
Aruna S Dixit ◽  
Roberto Quinlan ◽  
John P Smol
Keyword(s):  
Water Level ◽  
Sediment Cores ◽  
Hydrological Regime ◽  
Community Change ◽  
Water Levels ◽  
Water Level Fluctuations ◽  
Lake Diefenbaker ◽  
Fossil Records ◽  
Variable Versus ◽  
Reduced Water

Analysis of diatoms, algal pigments, and chironomids in sediment cores from two otherwise similar prairie reservoirs demonstrated that differences in reservoir formation (river valley impoundment versus lake inundation) and hydrological regime (variable versus stable water level) resulted in distinct patterns of aquatic community change. Lake Diefenbaker, a 500-km2 reservoir created by damming the South Saskatchewan River in 1968, experiences water level fluctuations of 6 m·year-1. In contrast, impoundment of Buffalo Pound Lake in 1952 flooded a natural lake, raised mean water levels ~2.0 m, and reduced water level fluctuations from ~3 to <1 m·year-1. Comparison of fossil records showed that reservoir formation did not inevitably lead to eutrophication. Lake Diefenbaker exhibited typical reservoir ontogeny with three trophic periods, including an initial ~4-year period of eutrophy, a decade of mesotrophy, and a gradual shift to modern productive conditions. Planktonic taxa dominated diatom communities at all times, whereas benthic chironomid and algal remains were rare. In contrast, pigment analyses suggested that phytoplankton standing crops declined after impoundment in Buffalo Pound Lake but that chironomid and macrophyte populations expanded. Such site specificity in trophic development appears to result from differences in the extent of inundation (500 versus ~5 km2) and the magnitude of subsequent water level fluctuations (6.3 versus <1 m).

scholarly journals Seed Hydration Using the Drum Priming System

HortScience ◽  
1997 ◽  
Vol 32 (7) ◽  
pp. 1220-1221 ◽  
Author(s):  
Jabe E. Warren ◽  
Mark A. Bennett
Keyword(s):  
Zea Mays ◽  
Moisture Content ◽  
Sweet Corn ◽  
Water Levels ◽  
Distilled Water ◽  
Time Required ◽  
Conventional Systems ◽  
Reduced Water

Drum priming enhances seed performance without the waste and additional materials associated with conventional osmotic or matric priming techniques. Sweet corn (Zea mays L.) se (`White D' Lite') and sh2 (`WSS-4948') endosperm seeds were hydrated using drum priming at 25 °C for 6 hours. During each cycle, 125-g seed samples were exposed to 1.6, 3.2, 4.8, or 6.0 mL of distilled water and then rotated in a drum for 1 hour to ensure uniform uptake. At the end of this period, samples of 100 seeds (each) were removed and moisture content was determined. Drum priming hydrated all seedlots gradually, with increasing time required at reduced water levels for individual seedlots to achieve the desired moisture content (25% to 30%). Drum priming may provide a better alternative to conventional systems of priming.

scholarly journals Algal Boom Characteristics of Yeongsan River Based on Weir and Estuary Dam Operating Conditions Using EFDC-NIER Model

Water ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2295
Author(s):  
Darae Kim ◽  
Changmin Shin
Keyword(s):  
Water Level ◽  
Algal Blooms ◽  
Water Security ◽  
Water Levels ◽  
Operating Conditions ◽  
The Yellow Sea ◽  
Management Level ◽  
Average Water ◽  
Reduced Water ◽  
Regional Water

A number of hydraulic structures have been installed along the Yeongsan River, including an estuary dam and two weirs (Seungchon and Juksan). While these structures aid in regional water security and use and reduce flooding, they reduce water flow in the summer, thereby frequently causing algal blooms. This study simulated algal bloom and water quality characteristics of sections of the Yeongsan River in South Korea under different weir and estuary dam operating conditions using the Environmental Fluid Dynamics Code—National Institute of Environment Research (EFDC-NIER) model. Results showed that when the management levels of the Juksan Weir and estuary dam were maintained, simulated water levels were EL. 3.7 m in the weir section and EL. −1.2 m (below average water level of the Yellow Sea) in the dam section. When both the weir and dam were open, the water levels varied with the tide; in contrast, when the Juksan Weir alone was open, the water level was between EL. −1.2 and −0.9 m, in line with the management level of the estuary dam. Opening the weir alone reduced algal blooms by 72–84% in the weir region, and opening the estuary dam alone reduced the algal blooms by 83% in the dam region. This improvement was attributed to the reduced water retention time and dilution due to seawater inflows.

scholarly journals The risk of slope processes on the territory of Ub municipality

2009 ◽  
Vol 89 (3) ◽  
pp. 147-164 ◽  
Author(s):  
Slavoljub Dragicevic ◽  
Ivan Novkovic ◽  
Marko Prica
Keyword(s):  
At Risk ◽  
Land Use ◽  
Spatial Development ◽  
Physical Structure ◽  
Development Strategies ◽  
General Analysis ◽  
Natural Conditions ◽  
Strategy Of Development ◽  
Limited Application

Stereotype researches of natural conditions on the territory of Serbia have caused limited application value of the large number of recent development strategies and planning documents of different purpose. The best indicator of this is the Strategy of development of planning area of the municipality Ub where, apart from general analysis of natural potential, determining the areas endangered by different intensity of geomorphologic processes was neglected in many ways. At what extent the territory is at risk of slope processes represents an important factor in choosing the location and planning the purpose of the land use, and in defining the degree of concentration of physical structure and objects of infrastructure. This kind of analysis is unavoidable segment of strategy for spatial development of some territory. Therefore, apart from the analysis of natural conditions as the potential of development of some territory, the same attention should be paid to rightful assessment of degree of impairment of the territory, i.e. limitations for its development and growth. .

Sign in / Sign up

Export Citation Format

Share Document