Browsing All Posts filed under »food webs«

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 […]

Top-down control varies within a species

January 14, 2019

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  Because consumer species can impose strong top-down effects on the structure and functioning of aquatic ecosystems, the loss or replacement of apex species may lead to dramatic alterations to the food web.  But can different forms of the same consumer species be sufficiently distinct that the replacement of one form by another triggers a […]

How the food web affects river restoration

October 8, 2018

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River restoration commonly  concentrates on improving habitat quality for threatened fish populations.  However, because stream fish are strongly influenced by food availability, competition and predation, a case can be made for also incorporating food web modelling into the restoration process.  A group of environmental scientists developed an ecosystem model and applied it to a river-floodplain […]

The magical diatom diet

July 5, 2018

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In forested headwater streams, detritus derived from decaying plant material is the primary source of energy driving the aquatic ecosystem, and most studies of such systems have focussed on the fate of leaf litter, the main resource.   However, because the food quality of detritus is extremely low it’s unclear how headwater streams support their  biological […]

Surveying river birds

July 5, 2018

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River birds are effective ecological indicators because they’re linked to river and riparian food webs in many  ways and are easily observed.  Boat-based surveys of river birds pose disturbance issues and can be difficult during periods of high or low flow, while transect-based surveys can be compromised by lack of access to private land.  Researchers […]

Why are there so many crocodiles in tropical waterholes?

March 26, 2018

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Transfers of organic material from one aquatic environment to another (for example, through flood pulses or animal migrations) allow productive donor ecosystems to subsidise less productive habitats. However, there are big variations in the extent to which different animal species depend on production subsidies.  To explore such differences, Australian researchers collected a wide array of […]

How sedimentation affects the food web

March 25, 2018

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In rivers and streams, high predator densities are predicted to boost algal biomass by reducing the number of grazing animals. However, in disturbed systems the smothering of stream bed surfaces by sediment is expected to have an opposite, negative effect on algal biomass.  Studies that investigate interactions between sedimentation (an abiotic stress factor) and predation […]