Water securityBacteria may help keep water cleaner

Phosphorus is a crucial nutrient regularly applied to crops such as corn and soybeans to help them grow efficiently. However, excess phosphorus can be carried by rainwater runoff into lakes and streams, creating potential problems for aquatic environments and the ecosystem services they provide to humans.

In trace amounts (less than 0.02 parts per million), phosphorus is actually good for water systems. It encourages the growth of algae and other florae, providing a healthy habitat for fish and other aquatic organisms. However, when too much phosphorus bleeds into waterways, an overgrowth of algae can occur, leading to depletions in dissolved oxygen that can kill aquatic life. Also, blooms of cyanobacteria can produce toxins that threaten public water supplies. 

“Historical applications of manure and fertilizer have built up phosphorus levels in many of our agricultural soils – often times above and beyond what’s needed by crops – which then renders the excess phosphorus susceptible to loss when microbial processes and other hydrological and biogeochemical factors come into play,” said Anthony Buda, a research hydrologist at the U.S. Department of Agriculture (USDA) Agricultural Research Service.

PSU reports that to combat this problem, researchers at Penn State, in collaboration with Cornell, Central Michigan University, and the USDA, are trying to better understand how several kinds of interactions affect phosphorus mobility in agricultural soils and streams. These findings can then be used to develop methods to better control phosphorus losses in agricultural environments.

“We are trying to understand two groups of bacteria that could affect whether phosphate is retained in the soil or becomes mobile and gets into the water,” said John Regan, professor of environmental engineering at Penn State and lead project director.

To better comprehend how microbes affect phosphorus migration into our waterways, the researchers have combined field monitoring in Mahantango Creek, a small upland agricultural watershed operated by the USDA, with laboratory testing involving soil column experiments conducted at Penn State. The experiments seek to evaluate the roles of two particular kinds of bacteria – dissimilatory iron-reducing bacteria (DIRB) and polyphosphate accumulating organisms (PAOs) – on phosphorus cycling in soils.

At the USDA watershed test site, the researchers are looking at the role microbes have on phosphorus mobility in natural environments.

“Microbes that affect phosphorus mobility are known to exist and are being used in some wastewater treatment plants to reduce the amount of phosphorus in water leaving the plant,” said environmental engineering graduate student Miranda Stockton.