Quantitative Effects of Atyid Shrimp (Decapoda: Atyidae) on the Depositional Environment in a Tropical Stream: Use of Electricity for Experimental Exclusion

1994 ◽  
Vol 51 (6) ◽  
pp. 1443-1450 ◽  
Author(s):  
Catherine M. Pringle ◽  
Gail A. Blake
Keyword(s):  
Depositional Environment ◽  
Dry Mass ◽  
Base Flow ◽  
Inorganic Materials ◽  
Flow Conditions ◽  
Tropical Stream ◽  
High Discharge ◽  
Sediment Mass ◽  
Organic Particles ◽  
Total Sediment

Effects of biotic (shrimp) and abiotic (discharge) factors on the depositional environment were quantified in a montane stream in Puerto Rico. Electricity was used experimentally to exclude large (approximately >1 cm in length) biota without artificially increasing sedimentation as in cage enclosure/exdosure experiments in stream systems. Shrimp (>1 cm in length) were excluded from rock substrata by semicircular fences hooked up to battery-powered fence chargers which emitted continuous pulses of electricity. Unelectrified control substrata had natural high densities of atyid shrimp. Significantly greater masses of total sediment, fine and large organic particles, and algal biovolume occurred in shrimp exclusion treatments relative to controls. Shrimp exclusion treatments experienced slow and steady accumulation of sediments under base flow conditions and a large stepwise increase in sediment weight following a storm. No measurable sediment accrued in the presence of natural densities of shrimp under base flow conditions. Shrimp rapidly removed sediments that accrued during the storm (440–620 g∙m2 dry mass−1), decreasing sediment mass in control treatments to near prestorm levels (5–13 g∙m2 dry mass−1) within 30 h. Atyid shrimp can significantly affect the accumulation of organic and inorganic materials on rock substrata in stream pools between high-discharge events.

scholarly journals Hydrological, Environmental and Taxonomical Heterogeneity during the Transition from Drying to Flowing Conditions in a Mediterranean Intermittent River

Biology ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 316
Author(s):  
Andy Banegas-Medina ◽  
Isis-Yelena Montes ◽  
Ourania Tzoraki ◽  
Luc Brendonck ◽  
Tom Pinceel ◽  
...  
Keyword(s):  
Ecosystem Services ◽  
Base Flow ◽  
Ephemeral Streams ◽  
Biogeochemical Processes ◽  
Flow Conditions ◽  
Intermittent Rivers ◽  
Terrestrial Biodiversity ◽  
Turn Over ◽  
Zero Flow ◽  
Intermittent River

Intermittent rivers and ephemeral streams (IRES) are increasingly studied because of their often-unique aquatic and terrestrial biodiversity, biogeochemical processes and associated ecosystem services. This study is the first to examine the hydrological, physicochemical and taxonomic variability during the dry-wet transition of an intermittent river in the Chilean Mediterranean Zone. Based on 30-years of river monitoring data and the TREHS tool, the hydrology of the river was characterised. Overall, the river shows a significant reduction in streamflow (−0.031 m3/s per year) and a substantial increase of zero flow days (+3.5 days per year). During the transition of hydrological states, variations were observed in the environmental conditions and invertebrate communities. During the drying phase, abundance, richness, and diversity were highest, while species turn-over was highest during base flow conditions. The disconnected pools and the flow resumption phases were characterised by high proportions of lentic taxa and non-insects, such as the endemic species of bivalves, gastropods, and crustaceans, highlighting the relevance of disconnected pools as refuges. Future climatic change scenarios are expected to impact further the hydrology of IRES, which could result in the loss of biodiversity. Biomonitoring and conservation programmes should acknowledge these important ecosystems.

scholarly journals Post-fire consequences for leaf breakdown in a tropical stream

2019 ◽  
Vol 31 ◽  
Author(s):  
Renan de Souza Rezende ◽  
Cristiano Queiroz de Albuquerque ◽  
Andrezza Sayuri Victoriano Hirota ◽  
Paulo Fernandes Roges Souza Silva ◽  
Ricardo Keichi Umetsu ◽  
...  
Keyword(s):  
Leaf Litter ◽  
Fungal Biomass ◽  
Mesh Size ◽  
Fire Effects ◽  
Dry Mass ◽  
Tropical Stream ◽  
Fire Event ◽  
Litter Bags ◽  
Fine Mesh ◽  
Post Fire Effects

Abstract Aim Wildfire is a natural pulsed disturbance in landscapes of the Savannah Biome. This study evaluates short-term post-fire effects on leaf litter breakdown, the invertebrate community and fungal biomass of litter from three different vegetal species in a tropical stream. Methods Senescent leaves of Inga laurina, Protium spruceanum and Rircheria grandis (2 ± 0.1 g dry mass) were individually placed in litter bags (30 × 30 cm: 10 mm coarse mesh and 0.5 mm fine mesh) and submerged in the study stream before and after fire. Replicate bags (n = 4; individually for each species, sampling time, fire event and mesh size) were then retrieved after 20 and 40 days and washed to separate the invertebrates before fire event and again immediately after fire. Disks were cut from leaves to determine ash-free dry mass, while the remaining material was oven-dried to determine dry mass. Results The pre-fire mean decomposition coefficient (k = -0.012 day-1) was intermediate compared to that reported for other savannah streams, but post-fire it was lower (k = -0.007 day-1), due to decreased allochthonous litter input and increased autochthones production. Intermediate k values for all qualities of litter post-fire may indicate that fire is equalizing litter quality in the stream ecosystem. The abundance of scrapers was found to be more important than fungal biomass or shredder abundance, probably due to their functioning in leaf fragmentation while consuming periphyton growing on leaf litter. Conclusions Theses results indicate that fire can modify the relationships within decomposer communities in tropical stream ecosystems.

scholarly journals A multi-functional and multi-compartment constructed wetland to support urban waterway restoration

2018 ◽  
Vol 13 (4) ◽  
pp. 764-770 ◽  
Author(s):  
T. M. Adyel ◽  
M. R. Hipsey ◽  
C. Oldham
Keyword(s):  
Constructed Wetland ◽  
Flow System ◽  
Surface Flow ◽  
Base Flow ◽  
Low Flow ◽  
Nutrient Loads ◽  
Storm Events ◽  
Flow Conditions ◽  
Storm Flow ◽  
Diverse Area

Abstract This study assessed the significance of a multi-functional and multi-compartment constructed wetland (CW) implemented to restore a degraded urban waterway in Western Australia. The wetland was initially constructed as a surface flow system, then modified through the incorporation of the additional laterite-based subsurface flow system, with the potential for operation of a recirculation scheme and groundwater top-up during low water flows in summer. The CW performance was assessed by comparing nitrogen (N) and phosphorus (P) attenuation during base flow, high flow and episodic storm flow conditions. The performance varied from approximately 41% total nitrogen (TN) and 66% total phosphorus (TP) loads reduction during storm events, increasing up to 62% TN and 99% TP during low flow and summer recirculation periods. In overall, the CW attenuated about 45% TN and 65% TP loads from being delivered to the downstream sensitive river between 2009 and 2015. The CW design proved to be not only highly effective at reducing nutrient loads, but also improved the ecological services of the urban waterway by providing a diverse area for habitat and recreational activities.

Modeling the Onset of Gas Entrainment in a Single Downward Discharge From a Stratified Gas-Liquid Region With Liquid Crossflow

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
R. C. Bowden ◽  
I. G. Hassan
Keyword(s):  
Experimental Data ◽  
Froude Number ◽  
Liquid Region ◽  
Flow Conditions ◽  
Critical Height ◽  
High Discharge ◽  
Gas Entrainment ◽  
Model Predictions ◽  
Pipe Inlet ◽  
Made In

The critical height at the onset of gas entrainment, in a single downward oriented discharge from a stratified gas-liquid region with liquid crossflow, was modeled. The assumptions made in the development of the model reduced the problem to that of a potential flow. The discharge was modeled as a point-sink while the crossflow was said to be uniform at the main pipe inlet. The potential function was determined from a superposition of known solutions for a point-sink and uniform flow. The resulting system of three equations demonstrated that the flow field was dominated by the discharge and crossflow Froude numbers. The system was solved numerically and provided a relationship between the geometry, flow conditions, dip location, and critical height. The model predicted that the critical height increased with the discharge Froude number and decreased with the crossflow Froude number. With no imposed crossflow, the model prediction demonstrated agreement with transient and quasisteady experimental data to within ±30%. Existing experimental correlations showed inconsistent crossflow effects on the critical height and disagreed with the model predictions at high discharge Froude numbers.

scholarly journals Analysis of the impacts of major anion variations on surface water acidity particularly with regard to conifer harvesting: case studies from Wales and Northern England

1998 ◽  
Vol 2 (2/3) ◽  
pp. 303-322 ◽  
Author(s):  
C. Neal ◽  
B. Reynolds ◽  
J. K. Adamson ◽  
P. A. Stevens ◽  
M. Neal ◽  
...  
Keyword(s):  
Large Range ◽  
Base Flow ◽  
Flow Conditions ◽  
Stream Acidification ◽  
Major Cation ◽  
North Wales ◽  
Acidic Component ◽  
Abstract Data ◽  
Water Acidity

Abstract. Data on the water quality of streams draining a range of acidic and acid sensitive, mainly afforested, upland catchments in mid- and north-Wales and northern-England are described to investigate the acidification effects of conifer harvesting in relation to natural variability. Most sites show a large range in pH and major cation and major anion concentrations. The waters draining from the smaller catchments are more acidic and aluminium bearing reflecting a higher proportion of runoff from the acidic soils in each area. However, there is often a less acidic component of runoff under base-flow conditions due to ground-water contributions particularly within the larger streams. Higher concentrations of nitrate occur for sites which have been felled although declines in concentration occur several years after felling. Multiple regression analysis reveals the importance of cation exchange and within catchment acidification associated with sulphate and nitrate generation. Sulphate also has a component associated with weathering but the patterns vary from catchment to catchment. Analysis of the influence of changing anion concentrations associated with tree harvesting reveals that the acidification induced by increases in nitrate can be offset or reversed by the lowering of chloride and sulphate concentrations due to decreased atmospheric scavenging by the vegetation, reduced evapotranspiration and increased surface runoff diluting the acidity generated. It is concluded that contemporary UK forestry guidelines with an emphasis on phased harvesting of catchments over several years and careful harvesting methodologies can alleviate most problems of stream acidification associated with felling activities and in some cases can reverse the acidification pattern.

Spatial changes in instream DOM quality under base flow conditions linked with different DOM sources in small forested catchments

2021 ◽  
Author(s):  
Maria Paula da Silva ◽  
Katharina Blaurock ◽  
Burkhard Beudert ◽  
Jan H. Fleckenstein ◽  
Luisa Hopp ◽  
...  
Keyword(s):  
Ground Water ◽  
Base Flow ◽  
Aquatic Systems ◽  
Flow Conditions ◽  
Forested Catchments ◽  
Spatial Changes ◽  
Doc Concentration ◽  
End Members ◽  
Ft Icr Ms ◽  
Ft Icr

<p>Dissolved organic matter (DOM) plays an important role in aquatic systems controlling metal bioavailability and mobility, and nutrient cycling. The quantity and quality of instream DOM determine its role and behavior in aquatic systems. Headwater streams are particularly sensitive systems to study the changes in DOM dynamics due to their immediate interface with adjoining hillslopes and the high soil-to- water-area ratio. However, the controls, sources and mobilization processes of DOM export in natural forested catchments are still poorly understood. The objective of this study is to combine high temporal resolution spectroscopic DOM analysis with high-resolution mass spectrometry data to characterize the spatial changes in DOM composition along a low-order stream in a forested catchment (Bavarian Forest National Park - Germany) during base flow conditions. Furthermore, the study aims to link the patterns found instream with fingerprints of DOM end member sources. DOM quality was monitored over 1.5 year in three sites along the stream using absorption indices indicators of aromaticity (SUVA<sub>254</sub>) and molecular weight (E<sub>2</sub>:E<sub>3</sub>) and data aggregating quality parameters and intensity based on formulas derived from discrete samples analyzed by FT-ICR-MS. Additionally, three end members corresponding to DOM in deep ground water, shallow ground water and water in the top layer of the soil were sampled in the catchment.</p><p>At base flow conditions, no significant changes in DOC concentration were observed spatially. Yet, absorption indices from DOM exhibited clear spatial patterns, with higher aromatic and lower molecular weight DOM at the lower floodplain compared to upstream. From the FT-ICR-MS data, however, high aggregate quality data showed a small gradient in DOM quality between the upper and lower parts of the catchment, with the relationship between DOC concentration and the relative intensity (RI) of molecular formulas being a better descriptor of the spatial changes. The patterns observed in formulas with an increase or decrease in RI at higher DOC concentrations is indicative of changes in DOM sources between upper and lower parts of the catchment. The characterization of end members could further elucidate the observed changes in RI of formulas. In the studied catchment, formulas with a decrease in RI at higher DOC concentration agree with the formulas most commonly found for DOM from the deep ground water, whereas the formulas being enriched at higher DOC concentration changed along the stream. At the upper part of the catchment, these formulas are the ones most abundantly present at the shallow ground water, whereas at the lower part these formulas are also representative of formulas found in the sample collected at the superficial layer of the soil. The monitoring of DOM amount and quality in the small forested catchments showed that DOM spatial variability is connected with the availability and mobilization of different sources, even during base flow conditions. The use of spectrophotometers allowed us to identify general trends in DOM quality and concentration, while FT-ICR-MS data was crucial to characterize DOM quality and link the findings instream with DOM sources.</p>

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