Nitrogen is a nutrient found in all living organisms. But excess nitrogen is a pollutant that is usually carried to water bodies in runoff containing nitrogen-based fertilizers and nitrogen-bearing sewage.
Various species of algae were chosen to represent biodiversity in the study because algae are the primary organisms that take up excess nutrients, such as nitrogen, from streams, lakes and oceans.
The power of niche partitioning
Cardinale's results showed that nitrate uptake in the model streams increased linearly with species diversity. On average, the eight-species mix removed nitrate 4.5 times faster than did a single species grown alone.
Evidence that these results were produced by niche partitioning includes the domination of differently shaped forms of algae in different types of stream habitats, as predicted by ecological theory. For example, high velocity habitats were dominated by small, single-celled species of algae that grew in ways that were resistant to displacement by the force of fast-moving water. By contrast, low velocity habitats were dominated by large, filamentous algae that were vulnerable to such forces.
In addition, as part of the research, streams were experimentally simplified until they contained just one type of a habitat, and no opportunity for species to express their niches. Results showed that each of these simplified water bodies then collapsed to one dominant species that singularly drove all nitrate uptake, without species diversity influencing such uptake. These result confirmed that niche differences among species
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National Science Foundation