Browsing All Posts filed under »plants«

Riparian roots help streams breathe

December 21, 2017

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In aquatic systems, especially those with abundant plants, dissolved oxygen concentrations often show strong daily fluctuations because there’s a net input of oxygen from photosynthesis during the day but a net loss of oxygen due to   respiration at night.  When researchers working on a small tropical stream in São Paulo State, Brazil recorded this pattern […]

Collapsing waterweeds:  shading and herbivory work together

December 21, 2017

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In lakes and ponds, aquatic plants help to maintain clear-water conditions and their decline can cause a shift to a turbid state with lower biodiversity.  But what triggers the collapse of waterweed populations?  Grazing by aquatic herbivores would seem to be an obvious cause, but supporting evidence for this idea has proved surprisingly elusive, leading […]

Once more from the top

December 21, 2017

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Top-down trophic cascades are population-level effects transmitted along food chains, from consumers down to primary producers.  In a typical three-level food chain the loss of top predators (for example, as a result of human exploitation) allows herbivore populations to increase, which in turn reduces populations of algae or higher plants.   However, few studies have considered […]

Invasive waterplants: be prepared

December 21, 2017

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Investigators from Europe, the USA and New Zealand recently authored a comprehensive review of methods for the management of invasive freshwater plants.   As well as describing options for mechanical, biological and chemical control, the review includes information on relevant biology, management costs, the effects of management on freshwater ecosystems, and the post-management restoration of native […]

Restoration and invertebrates: Reappraising stream condition indicators

September 25, 2017

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In degraded rivers and stream systems, the replanting of riparian vegetation is a common restoration activity, partly because increases in shading, nutrient interception and litter fall are expected to provide food and habitat benefits for aquatic communities. Changed habitat conditions should be reflected in indices of stream condition, such as those based on macroinvertebrate richness. […]

Ironing out harmful algal blooms

September 25, 2017

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An understanding of how iron affects the supply of nutrients in aquatic systems may open the door to better success in managing harmful algal blooms. In highly productive lakes, the release of phosphorus stored in the bottom sediment can encourage bloom development, but nutrient release is retarded in the presence of iron, which precipitates phosphorus […]

Urban trees protect local water bodies

September 25, 2017

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As a result of nutrient transfer from the land, urban waterways often have high concentrations of nitrogen and phosphorus, which can lead to algal blooms, low water clarity, oxygen depletion and species loss. Nutrient enrichment problems also extend to urban groundwater, where water quality can be compromised.  Although nutrients moving from land to groundwater water […]