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