Browsing All Posts filed under »water flow«

How rivers befriend seabirds

January 14, 2019

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Where rivers flow into the ocean, the density fronts between fresh and salt water masses help to concentrate zooplankton and larval fish, making them more available to predators.  For example, freshwater discharge from the Columbia River creates a large brackish plume that can stretch for hundreds of kilometres along the North American coast, and nutrient […]

Turbulent times for freshwater plants

January 14, 2019

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Water movement is one of the most important factors affecting the distribution of aquatic plants, and has a beneficial or detrimental impact  depending on the magnitude of flow.  Japanese researchers compared the effects of steady flow and turbulence on three plant species with different types of morphology: western waterweed (Elodea nuttallii) with whorled leaves, curly-leaved […]

What drives regional differences in streamflow?

October 8, 2018

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Typically, large-scale models of stream flow take into account the interaction between climate and vegetation (which determines evapotranspiration) and landscape features that dictate how non-evaporated water is diverted to soil, groundwater and overland flow.  However, there are often strong spatial variations in streamflow drivers, which can limit the usefulness of global models.  Researchers drew on […]

Tree cover makes for lower fish diversity

March 27, 2017

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A pervasive feature of lowland streams, especially in areas where land has been cleared for agriculture or urban development, is a decrease in forested cover from the headwaters to the mouth. The presence or absence of streamside tree cover has a profound influence on stream ecology. Streams running through undisturbed forests typically contain large woody […]

How river transport affects dissolved organic matter

December 13, 2016

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In most rivers, the downstream transport of dissolved organic matter (DOM) makes large amounts of energy available to aquatic ecosystems. The River Continuum Concept (RCC) of Vannote et al. (1980) provided a useful framework for studying the influence of organic material from headwater streams on the structure and function of downstream ecosystems. The RCC hypothesized […]

Predators concentrate on current-concentrated prey

December 13, 2016

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In marine environments, recirculating eddies, upwellings and downwellings play an important role in concentrating plankton in small areas, a process that attracts predators such as fish, mammals and birds and boosts ecological productivity significantly above background levels. However, much less is known about the ways in which physical processes may concentrate organisms and intensify food-web […]

Creating fast flow refuges in streams

October 15, 2015

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Hydroelectric power plants create frequent, intense pulses in downstream river flow (hydropeaking) that are typically accompanied by increased sediment movement, high turbidity and habitat scouring. These changes can affect several aspects of the biology of fishes, including migration, spawning, early development and growth. In Switzerland, a 60% decline in catches of brown trout since 1980 […]