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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 […]

Low biodiversity in productive lakes

December 13, 2016

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The over-supply of nutrients to lakes (through pollution, for example) stimulates the growth of plant plankton, which blocks light from reaching bottom-dwelling algae and higher plants. Therefore, nutrient excess has the potential to reduce habitat diversity and the associated biodiversity of animal plankton, macroinvertebrates and fish. An international team of biologists looked at the relationship […]

Top predator boosts species richness – but not in alien ecosystems

December 13, 2016

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The spiny water flea Bythotrephes longimanus is a large cladoceran, a specialised carnivore and a top predator. Invasions of North American lakes by Bythotrephes have been linked to dramatic changes in food web structure and reductions in species diversity, which seems to contradict the expectation that top predators increase the evenness and diversity of aquatic […]

Surrogates for species

March 23, 2016

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Ecological communities are commonly defined and compared by reference to their species composition. However, in the case of many types of organisms, such as freshwater plankton, species-level identification is a slow, error-prone process, and for this reason there’s growing interest in characterising communities by carrying out identification at a higher taxonomic level (genus or family). […]

Hotspots for riparian plants

October 15, 2015

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Streamside plants buffer the damaging effects of floodwaters and filter material and nutrients washed down from higher points in the catchment. While these processes are well understood, the effects of seepage and overland flows on riparian plants have been largely overlooked. To explore how streamside plant diversity is affected by groundwater discharge from upland areas, […]

Rivers of plastic are hazardous to fish

October 15, 2015

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The annual global production of plastics is close to 30 million tonnes and plastic items are one of the most ubiquitous types of pollutant. Although much plastic debris is transported to the oceans by way of freshwater streams, there are very few estimates of plastic loads in rivers. A recent study carried out on the […]

Do stable habitats support longer food chains?

December 16, 2014

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Food chain length (the height of the food web, or the number of trophic transfers from basal food resources to top predators) affects ecosystem productivity, trophic cascades and the bioaccumulation of toxins. Food chain length varies widely across aquatic systems, but the reasons for these differences, and how they are affected by environmental conditions, are […]