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The following is an excerpt from a news
release issued by the National Science Foundation.
Small streams remove more nutrients such as nitrogen from
water than do their larger counterparts, according to researchers
who have applied sampling methods developed in a National Science
Foundation (NSF) Arctic area ecological study to waterways across
the nation. The finding could have important implications
for land-use policies in watersheds from the Chesapeake Bay
on the East Coast to Puget Sound in the West.
The findings, published in Science* magazine, are based on
data collected initially from streams in NSF’s Arctic Tundra
Long-Term Ecological Research site in Alaska. Excess nitrogen
can cause ecologically damaging effects, including algae blooms,
in large waterways because the nutrients are transported downstream
and collect there.
“There’s a very strong relationship between the size
of a stream and how rapidly that stream removes nutrients,”
said Bruce Peterson of the Ecosystems Center at the Marine Biological
Laboratory in Woods Hole, Massachusetts. “The smaller
the stream, the more quickly nitrogen can be removed and the
less distance it will be transported down the stream.”
He noted that the findings are unique because research teams
working in a coordinated and identical fashion nationwide under
the same research protocol produced them.
“In terms of ecosystems studies it’s very rare to
get people from this many sites to agree to do this kind of
controlled experiment,” Peterson said. “Many people
study nitrogen cycling, but they all tend to do their own experiments.
Collaboration is the key to developing a general understanding
of ecosystems.”
Peterson notes that, collectively, the new studies provide
a radically different picture of the role of small streams in
contributing to existing nutrient loading. “Traditionally
streams have been thought of as transport systems moving substances
from catchments to downstream points,” he said. “It’s
been difficult to understand how dynamic the stream system itself
is.”
By placing tracers in smaller streams, the researchers discovered
how quickly nutrients were assimilated and processed by organisms
that live on the stream beds.
The findings could have important implications for land use
policies. In many agricultural areas, for example, small streams
are often covered to allow ease of access for tilling and working
fields. The covering, in effect, creates a dark pipe that inhibits
the stream’s ability to scrub excess nutrients.
While excess nitrogen has many sources, including runoff from
residential lawns and byproducts of automobile combustion, taking
greater care to insure that small streams can work effectively
to clean the water will reduce the overall nitrogen load that
makes its way into larger bodies of water.
“It doesn’t mean that you can ignore your sewage
treatment plants, but if we can do better with our small streams
and do some restoration activities, it’s going to have
some benefits,” Peterson said. “What it means is
that you have to take care of the streams on the landscape.”
* Science 2001 April 6; 292: 86-90, American Association for
the Advancement of Science.
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