Research suggests Bay creates its own phosphorous

By BRUCE HOTCHKISS
Senior Editor

A researcher and scientist at the University of Delaware is suggesting the Chesapeake Bay ’s principal problem with phosphorous is not what is coming off the land around it but what it is creating within its own waters.

Dr. Deb Jaisi, an assistant professor in the University of Delaware ’s Department of Plant and Soil Science, is in the second year of a soybean checkoff-funded study that shows that phosphorous build-up in the Bay is the result of a process called “remineralization” as opposed to what might be called “remobilization.”

In that event, Dr. Jaisi said, it’s “an efficient system for microorganisms but a real pain for nutrient management.” 

Questioned as to whether his findings might impact the current and on-going debate in Maryland on the use of the so-called Phosphorous Management Tool to measure the phosphorous runoff from watershed cropland, Dr.Jaisi paused, then replied, “I can’t answer that.”

Another pause. “I don’t know that yet.”

He did say, however, in an interview with The Delmarva Farmer, that “more P is coming from mineralization than flowing from the earth.”

What precisely is remineralization?

Adam Thomas, a member of the staff of the UDaily, the campus paper at the University of Delaware , explained it this way:
Remineralization is a cycling process that starts with the breaking down of organic matter, in this case phytoplankton (algae) blooms that take up phosphorous and live in top level waters that have undergone eutrophication. 

When those phytoplankton die, they settle to the bottom of the body of water, break down and release phosphorous, causing hypoxia.

While some believe the dead zone in the center of the Chesapeake during the midsummer months can be attributed to nutrient remobilization — phosphorous entering from terrestrial or atmospheric sources, settling to the sediment and then again mobilizing to bottom water — this research suggests that the problem lies in organic matter remineralization, as it forms the predominant pathway for phosphorous cycling in this section of the Bay.

“This remineralization process is more of a natural process of cycling and leans more toward a self-sustaining process than having direct phosphorous coming into the bay from the land,” said Dr. Jaisi. 

Dr. Jaisi continued: “That [remobilization] pathway is almost not there. It is very insignificant because the bulk of land-driven phosphorus is buried in the sediment and is inactive. People used to think that that pathway is a significant pathway compared to remineralization, which is not the case. 

“It’s the other way around, and that has a direct impact on how to control the nutrient issue in the Bay.”

Dr. Jaisi heads the Environmental Biogeochemistry Laboratory at the University of Delaware. 

A major focus of his research involves the “biogeochemical processes that regulate the source, sink, transformation and internal cycling of phosphorus in terrestrial and coastal environments.” and
Obviously, then, the phosphorous issues drawing the attention of the environmental community and state government officials in Maryland captured his attention. 

He argued that that an efficient nutrient management plan for the Chesapeake Bay cannot be crafted until the origins of the invading nutrients, particularly phosphorous, are known. 

Did it come from runoff of manure or fertilizers? Or did it originate in wastewater, or geological processes such as soil or rock dissolution? Or how about driven into the Bay from the ocean?

Dr. Jaisi, who is an environmental biogeoscientist, noted that the EPA established stringent rules on total maximum daily load in the Chesapeake Bay with rigorous accountability measures requiring 24 percent phosphorus cutoff by 2025, with at least 60 percent action completed by 2017. 

“Under this plan, EPA estimates that 20 percent or about 600,000 acres of cropped land in the watershed, will have to be removed from production and be converted to grassland or forest,” Dr. Jaisi said. 

He added that, needless to say, “this will adversely affect the farmers’ quality of life.” 

With soybean checkoff contributions from Maryland , Delaware and Pennsylvania , Dr Jaisi determined to pinpoint the source of the Bay’s phosphorous.

His research earned him a recent peer-reviewed report in the Journal of Environmental Science and Technology under a headline: “Organic Matter Remineralization Predominates Phosphoroous Recycling in the Mid-Bay Sediments in the Chesapeake Bay .”

The introduction to the report states that “This is the first research that identifies the predominance of the remineralization pathway and recycling of P within the Chesapeake Bay .”

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