Friday, November 15, 2019

Tracking Chicken Sh*$ in Chesapeake Bay

Rapid Response Chicken Sh*% team
          The Chesapeake Bay has absorbed the Eastern seaboard’s agricultural and urban runoff for centuries ever since Europeans settled there in the 1600s. The chemical wastes took their toll in the 1960s with anoxic dead zones and toxic algal blooms. Laws were passed in the states within its watershed to eliminate phosphates in detergents and to watch out for rampant pollution from under-performing sewage treatment plants. The Bay was considerably cleaned up in the decades following but not before the oyster, blue crab and sea bass fisheries were almost destroyed.
            In the summer of 1998, a bloom of the noxious alga, Pfiesteria, caused massive fish kills. Pfiesteria, first described in 1988 by JoAnn Burkholder of North Carolina State University, is a dinoflagellate, an organism with a complex life cycle part of which is a stage that produces neurotoxins thought to be responsible for fish kills. In several locations in the Bay where the fish kills occurred, it was thought that a relatively new source of pollution was potentially impacting water quality. Pollution from the more than 6,000 unregulated chicken barns, each with 25,000 chickens, was indicated as the culprit. Stimulated by slugs of nutrients from chicken barns on the Eastern Shore, Pfiesteria was also thought to cause human health issues, but at the time this finding was controversial. Environmentalists stormed the state legislatures in Maryland, Delaware, and Virginia calling for regulation of chicken wastes. 
Typical Delaware chicken barn
            Chicken producers and farmers responded with claims that they were operating within the law. They demanded proof that the nutrients in chicken farm runoff were causing the deadly algal blooms in the Bay. Who actually owned the chicken waste (75,000 tons produced per year) was another matter that complicated things. Farmers, who built low-slung barns on their property to house the chickens, don’t actually own the chickens they are raising. The producer essentially loans the chickens to them to raise from hatchlings to pullet size birds. The farmers buy (and own) the chicken feed from the producer. No one wanted to take domain over the wastes.
One the farms we monitored
            Working with Mat Wooller on the biocomplexity of mangroves project, we discussed how and if isotope tracers might help in identifying whether the source of pollution causing the Pfiesteria blooms was chicken wastes. Chickens excrete a different form of nitrogen in their wastes that is chemically distinct from the nitrogenous wastes from cows, fertilizers, and human sewage pollutants. Their waste, uric acid, is a complicated breakdown product similar in complexity to the backbone structures of DNA and RNA. Wooller and I hypothesized that if we could trace uric acid from chicken farms into the ecosystem and into Chesapeake Bay waters, we’d know whether chicken waste was responsible for the blooms. In order for this to be conclusive, the uric acid would need to have a distinctive isotope signature that could be further traced back to chicken farming. 
Mat Wooller's cartoon of the flow of nitrogen
            I wrote a small proposal to the Smithsonian’s Mellon fund and received a fellowship to carry out the study. We started by learning to assay uric acid using a chemical test kit. Then, we purchased several hundred grams of isotopically labeled uric acid and designed an experiment to follow its concentration and its incorporation into the organisms within a small watershed on Smithsonian’s Environmental Research Center. The isotopically labeled uric acid was expensive, a few thousand dollars. We mixed it into a large vat of stream water, adjusted the concentration, and had a special pump drip the solution into a 1-meter wide creek. We’d designed a week-long experiment and were monitoring it every 12 hours by collecting creek water over its 50 meter reach as the stream emptied into the Bay.
            During the second day, our uric acid tracer disappeared. We were puzzled and checked our assay method. It worked. We scratched our head. The next morning we took a sample from the vat of uric acid solution and found that all of the uric acid was gone! Native microbes had converted it quantitatively to ammonium. Our experiment was a failure or so we thought. We learned two things: uric acid, whether from a bottle or from the rump of chicken, will convert swiftly to ammonium, and elevated levels of ammonium can be detected in streams and enter the food web.
            With summer intern Quinn Roberts, we developed a field plan for taking samples at the edges of chicken farms that had large manure piles on their property. Ditches that drained the land surround most chicken farms on the Eastern Shore of Maryland. These farms also had the majority of their land under some sort of crop, typically corn or soybeans. We had no interest in investigating individual farmers, who were growing chickens and earned very little for their efforts. Ultimately the big producers like Perdue or Holly Farms were making substantial profits. We were careful to obtain our samples without being detected by the farmers though. We collected a few leaves from crops plants, a baggie full of soil they were growing in, a water sample from any standing water, and if at all possible, a handful of chicken waste. Chicken “waste” or manure is actually a combination of chicken excrement, straw from the birds’ bedding, and bits of feathers. Scooping up the chicken waste was the most daring thing we did—often casing the “job”, swinging the car around, then streaking out with gloves on, grabbing a hasty sample, before racing back to the car and pealing away. One of intern Allie Gales' favorite stories is having her run to a manure pile with gloves. When she said: "I'm nervous!" I said: "Just tell them it's for your grandma's petunias if anyone asks!"
            Occasionally locals asked us what we were doing in their neighborhood. I dressed in plaid shorts, a pink polo shirt, and looked nothing like a senior scientist. I told curious folks that we were lost and looking for the way to the beach. Mat in baggy cargo shorts used his thickest British accent and claimed he was a British Botanist touring America. Quinn Roberts wore a college T-shirt and short gym shorts. Her cover was as a student who needed to have a research project to graduate. Near the end of our study, we still had not sampled an actual chicken. Quinn bravely knocked on a farmer’s door and asked for a sample. She was taken to one of the barns and handed a scrawny nearly-dead chicken, which Quinn had to dispatch. For 6 months afterwards, she was a vegetarian.
Mat and Quinn monitoring a farm drainage ditch
            We found uric acid, the chicken’s waste compound, only once in mid-December when it was cold and microbial activity was slowed such that we could actually catch the uric acid before it was converted to ammonium. Meanwhile, we were measuring all of the nitrogen compounds (i.e., ammonium, nitrate, nitrite, and organic nitrogen) in the samples. We could tell based on the concentrations and the isotope compositions that the nitrogen had originated from chicken manure. The isotope signatures showed an enrichment of the heavy isotope of nitrogen (15N) that could be traced from the chicken waste to the soil to the crops and into streamside vegetation. As in many ecosystem studies of this type, it was a more complicated story than we had originally anticipated. I gave several presentations to interested people in the area.  A few times I had representatives from the chicken industry in the audience who challenged our data and interpretations. They had valid concerns. We had to trace the nitrogen from chicken feed to the Chesapeake Bay, which included eight different steps, all of which introduced uncertainties.
Seining for fish on the Nanticoke River
            We expanded our sampling to three major river systems on the Eastern Shore including the Nanticoke River, which contains the greatest concentration of chicken barns in its watershed. We sampled water, plankton, and small fish. The data showed—clearly to us in the know—that chicken waste nitrogen from uric acid ultimately made it into fish tissue. Whether that fact could be translated into a harmful algal bloom and fish kills was another problem. We never made that final connection because that year it rained a lot, and the concentrated chicken wastes were washed safely out to sea. We also had a problem with our sampling of leaves from shrubs and trees adjacent to the chicken farms.
Quinn and Marilyn found uric acid in the field
            The nitrogen isotope patterns in these leaves were the opposite from what we’d predicted. There was much less of the 15N isotope in the leaves within a radius about 1 kilometer around a chicken farm.  The following summer I worked with interns Allie Gale and Val Brenneis to capture ammonia, a gas that was wafting off of the piles of chicken manure. Everyone can identify with the smell of an animal feedlot. That smell is largely coming from ammonia (NH3).
Marilyn, Val Brenneis, and Allie Gale, teaching how to fish seine

There was a large isotope effect from the emanation of the ammonia from the solid chicken manure. We used the same techniques Wooller and I had perfected in our mangrove studies to collect ammonia in rainwater, storm drains, and the air. Contrary to what we’d originally hypothesized, the nitrogen from the chicken wastes had an additional pathway for spreading the pollution. The air surrounding the farms was laden with ammonia polluting a far larger region than direct application of chicken wastes to soil or into ground water.
Nutrients from chicken sh($ diagram
            The work’s not been published. Yet again, another story of biogeochemical complexity that we eventually figured out but have not formally put into the permanent record. I need to pull together the thousands of data points taken lovingly by my young colleagues and write a full on scientific report. Fortunately for the Chesapeake Bay, the Delaware and Maryland legislatures passed laws that helped the farmers deal with the wastes of the chickens they were growing to support the Big Ag chicken producers. Manure piles are now required to be covered and allowed to “ferment” on site. Farmers on the Eastern Shore never polluted the air and water intentionally, but had nowhere to dispose of the chicken wastes naturally generated. Near the end of our study, Perdue started a processing plant to receive the manure and convert it into a clean source of fertilizer that they shipped out to the Midwest where it was needed. Mat, Quinn, and I were given a special tour of the plant because we were recognized as scientists who were intent on understanding the problem, not necessarily out to “get them”. We laughed when we decided what to wear to tour a chicken shit processing plant: me, a nice blouse and slacks; Mat, a button downed shirt and tie; Quinn, a skirt and blouse.
Dressed to tour a chicken sh$# processing factory
            Pfiesteria blooms are, fortunately, no longer a major problem for the Bay.


  1. I noticed the 1999 mobile lab, I must say that the Mercedes-Benz Sprinter Van was a bit of an upgrade

  2. Such a great story! Im interested in tracing seabird, and other marine consumer, guano-derived nutrients so this information was so helpful! Very interesting that uric acid is converted so quickly to ammonium (under the right conditions)!


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