The unnecessary amounts of phosphorus carried by rainwater from farms to lakes can now be significantly reduced, a new study has revealed.
In a U.S. Department of Agriculture (USDA)-funded study, researchers from Pennsylvania State University (PSU) collaborated with Central Michigan University and Cornell to study the movement of phosphorus from agricultural lands to streams. The results of the study would help the researchers to come up with ways of controlling the runoff of phosphorus.
Phosphorus In Lakes
Crops like soybean and corn benefit from the nutrition provided by phosphorus but excess of it are oftentimes carried by rainwater toward streams and lakes, which can cause water pollution and ecosystem disruption.
Presence of the nutrient is not entirely bad for the aquatic environment. Amounts less than 0.02 parts per million, phosphorus can encourage algal activity. But more than the said amount can force the algae to grow too much. When this happens, the oxygen in the aquatic environment gets depleted rapidly, thus harming the fishes and other flora. Along with the overgrowth is the existence of cyanobacteria that releases toxins and hurt the water supply.
Phosphorus Mobility
USDA research hydrologist Anthony Buda said that phosphorus from fertilizers and manure often builds up in many agricultural soils. The excess are then lost through microbial activity and other biogeochemical and hydrological influences.
PSU Environmental Engineering professor and lead project director John Regan said their research involves the study of two bacterial groups, the dissimilatory iron-reducing bacteria (DIRB) and polyphosphate accumulating organisms (PAOs), both of which play a huge role in phosphorus retention and movement from the soil to the water.
"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 Miranda Stockton, a graduate student of environmental engineering.
The researchers are studying the said microbes in the field at the watershed site in Mahantango Creek operated by the USDA and in the laboratory via soil column testing.
The field monitoring group is observing the effect of microbes on phosphorus movement while in their natural setting, while the laboratory group is conducting experiments by injecting soil columns with a DIRB microbe, Shewanella oneidensis and a PAO microbe.
Postdoctoral researcher Claudia Rojas said the separate laboratory monitoring is necessary to help them understand the behavior of the microbes in relation to phosphorus cycling while in a controlled setting.
DIRBs And PAOs
DIRBs releases phosphorus by breathing through iron. Regan explained that as the soil gets abundant amounts of water, the level of oxygen is reduced. Through the iron in the soil, these bacteria encourage mobility of phosphorus by releasing it.
PAOs, on the other hand, stores high amount of the phosphorus in their cells, break it up and release phosphate. When the water in the soil has enough water and oxygen, PAOs store the phosphorus — only releasing it when there is oxygen reduction.
Lakes with high levels of phosphorus, a biofilm forms on the stream floor and in that film are many bacteria that undergo daily gain and loss of oxygen.
"We are looking to see if there are microbes in the biofilm that can take up and release phosphorus under these cyclic conditions," said Regan. "So far, we've found that there are lots of PAOs there."
The researchers are now working on expounding the roles of these microbes, the process they undergo to assists phosphorus cycling and how much of the phosphorus is altered along with bacterial growth.
As soon as the research concludes, the scientists would be able to efficiently map out the watersheds and control excessive amounts of phosphorus in lakes.
