Streams Cleaned by Algae
One’s first thought of algae might be of green goopy stuff resembling moss that lines lake shores and river banks. However, recent research has shown algae biodiversity can remove harmful pollutants from stream water. University of Michigan researcher Brad Cardinale constructed over 100 manmade streams in a lab to study how the number of algae species in freshwater impacts the rate of nitrate removal. Cardinale found that a combination of eight algae species in freshwater resulted in the removal of nitrate 4.5 times faster than when only one algae species was present.
Mr. Cardinale said, “If we were to maintain streams in their naturally diverse state, these streams that we love for their recreation, for their beauty, for fishing, etc. … have the tangential benefit of cleaning up our water for us. One implication (of the study) is, if we let nature do its thing, we don’t have to run around creating very expensive water treatment plants all over the planet.” (Source: Reuters.com)
Nitrate is a naturally occurring form of nitrogen and is a nutrient for plants such as algae. In streams near farmland though, it is often artificially elevated by runoff from chemical fertilizers used nearby, and manure. Excessive nitrate in water supplies can lead to algal blooms where there is too much algae, and lack of oxygen in the water for aquatic species like fish. Also excessive nitrate in drinking water can harm humans.
Additionally, related research found nitrate levels in streams may be connected to their production of a greenhouse gas called nitrous oxide. This study indicated that reducing nitrate levels from agricultural runoff would likely reduce the greenhouse gas production. Biodiversity of algae in streams therefore might play a role in reducing both nitrate and nitrous oxide production, which would limit the greenhouse gas generation. Nitrous oxide has a capacity to trap heat in the atmosphere 300 times greater than that of CO2.
Dead zones in the oceans are areas with oxygen levels low enough they can’t support marine life in the normal way. These areas are in part created by the extra nitrogen introduced into river and marine systems by intensive agriculture.
Image Credit: Eugene Zelenko