نتایج جستجو برای: rivers

تعداد نتایج: 19001  

2013
Sezal Jain Stephen Nuske Andrew Chambers Luke Yoder Hugh Cover Lyle Chamberlain Sebastian Scherer Sanjiv Singh

Mapping a rivers course and width provides valuable information to help understand the ecology, topology and health of a particular environment. Such maps can also be useful to determine whether specific surface vessels can traverse the rivers. While rivers can be mapped from satellite imagery, the presence of vegetation, sometimes so thick that the canopy completely occludes the river, complic...

Journal: :Journal of fish biology 2012
W Anteneh A Getahun E Dejen F A Sibbing L A J Nagelkerke M De Graaf T Wudneh J Vijverberg A P Palstra

The reproductive biology of the only known intact species flock of large cyprinids, the 16 Labeobarbus species of Lake Tana (Ethiopia), has been extensively studied for the past two decades. Seven species of Labeobarbus are known to migrate >50 km upstream into tributary rivers for spawning during the rainy season (July to October), whereas eight other species are absent from these rivers and p...

2013
Marc Pouilly Danny Rejas Tamara Pérez Jean-Louis Duprey Carlos I. Molina Cédric Hubas Jean-Remy D. Guimarães

We examined mercury concentrations in three fish assemblages to estimate biomagnification rates in the Iténez main river, affected by anthropogenic activities, and two unperturbed rivers from the Iténez basin, Bolivian Amazon. Rivers presented low to moderate water mercury concentrations (from 1.25 ng L(-1) to 2.96 ng L(-1)) and natural differences in terms of sediment load. Mercury biomagnific...

2016
Haidong Zhou Tianqi Ying Xuelian Wang Jianbo Liu

Twelve selected pharmaceuticals including antibiotics, analgesics, antiepileptics and lipid regulators were analysed and detected in water samples collected from 18 sampling sections along the three main urban rivers in Yangpu District of Shanghai, China during four sampling campaigns. Besides, algal growth inhibition test was conducted to preliminarily assess the eco-toxicology induced by the ...

2013
Ahmed Moustafa Ashraf El-Hamalawi Andrew Wheatley

The advanced monitoring of water quality and performing a real time hazard analysis prior to entering Water Treatment Works (WTW) is very much a necessity nowadays in order to give warning of any contamination and avoid downtime of the WTW. Ultrasonic flow sensors are considered to be the most stable and reliable sensors to be used within the water and wastewater industry, as they are not easil...

2017
Chouly Ou Carmen G Montaña Kirk O Winemiller

Body size is frequently claimed to be a major determinant of animal trophic interactions, yet few studies have explored relationships between body size and trophic interactions in rivers, especially within the tropics. We examined relationships between body size and trophic position (TP) within fish assemblages in four lowland rivers of the Lower Mekong Basin in Cambodia. Stable isotope analysi...

2017
Wade L. Hadwen Christine S. Fellows Douglas P. Westhorpe Gavin Rees Simon M. Mitrovic Brett Taylor Darren Baldwin Ewen Silvester Roger Croome

Understanding longitudinal trends in the processing of carbon in rivers represents a much conceptualised, but infrequently tested, issue in aquatic ecology. In this study, we conducted concurrent longitudinal examinations of three very different rivers in eastern Australia to determine whether general principles in river functioning exist across broad geographic and hydrologic scales. Specifica...

Journal: :The Science of the total environment 2005
Steven J Balogh Yabing H Nollet Heather J Offerman

Methylmercury (MeHg) bioaccumulates in aquatic food webs and can pose health risks to animals at higher trophic levels. Characterization of MeHg production in and export from watersheds can help clarify exposure scenarios for aquatic life downstream. A number of studies have demonstrated that anoxic conditions in the saturated soils of wetlands can promote the production of MeHg, and these wetl...

2011
Init Ithoi Azman Jali J. W. Mak Wan Yusoff Wan Sulaiman Rohela Mahmud

This study reports the occurrence of Blastocystis in water from two rivers, Sungai Congkak and Sungai Batu, located in recreational areas in Malaysia. This protozoan was detected in samples from both rivers with an average of 33.3% and 22.1%, respectively. It was detected highest at the downstream (73.8% and 33.8%) followed by midstream (17.5% and 25.0%) and upstream (8.8% and 7.5%) stations, w...

2007
David B. Jepsen

We analysed stable carbon and nitrogen isotopic ratios of dissolved inorganic carbon (DIC), plants, detritus and fishes to estimate the relative importance of dominant production sources supporting food webs of four Venezuelan rivers with divergent geochemical and watershed characteristics. Based on samples taken during the dry season at each site, fishes from two nutrient-poor, blackwater rive...

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