A team of University of Texas at Arlington
biologists working with the U.S. Geological Survey has found that watershed
wetlands can serve as a natural source for the improvement of streams polluted
by acid rain.
A team of UTA biologists analyzed water samples in the Adirondack Forest Preserve.
The group, led by associate professor
of biology Sophia Passy, also contends that recent increases in the level of
organic matter in surface waters in regions of North America and Europe – also
known as “brownification” – holds benefits for aquatic ecosystems.
The research team’s work appeared in
the September issue of the journal Global Change Biology.
The team analyzed water samples
collected in the Adirondack Forest Preserve, a six million acre region in
northeastern New York. The Adirondacks have been adversely affected by
atmospheric acid deposition with subsequent acidification of streams, lakes and
soils. Acidification occurs when environments become contaminated with
inorganic acids, such as sulfuric and nitric acid, from industrial pollution of
Inorganic acids from the rain filter
through poorly buffered watersheds, releasing toxic aluminum from the soil into
the waterways. The overall result is loss of biological diversity, including algae,
invertebrates, fish, and amphibians.
“Ecologists and government officials
have been looking for ways to reduce acidification and aluminum contamination
of surface waters for 40 years. While Clean Air Act regulations have fueled
progress, the problem is still not solved,” Passy said. “We hope that future restoration efforts in acid streams will consider
the use of wetlands as a natural source of stream health improvement.”
Working during key times of the year
for acid deposition, the team collected 637 samples from 192 streams from the
Black and Oswegatchie River basins in the Adirondacks. Their results compared
biodiversity of diatoms, or algae, with levels of organic and inorganic acids.
They found that streams connected to wetlands had higher organic content, which
led to lower levels of toxic inorganic aluminum and decreased presence of
harmful inorganic acids.
Passy joined the UT Arlington College of Science
in 2001. Katrina L. Pound, a doctoral student working in the Passy lab, is the
lead author on the study. The other co-author is Gregory B. Lawrence, of the USGS’s New York Water Science Center.
The study authors believe that as
streams acidified by acidic deposition pass through wetlands, they become
enriched with organic matter, which binds harmful aluminum and limits its
negative effects on stream producers. Organic matter also stimulates microbes
that process sulfate and nitrate and thus decreases the inorganic acid content.
These helpful organic materials are
also present in brownification – a process that some believe is tied to climate
change. The newly published paper said that this process might help the
recovery of biological communities from industrial acidification.
Many have viewed brownification as a
negative environmental development because it is perceived as decreasing water
quality for human consumption.
“What we’re saying is that it’s not
entirely a bad thing from the perspective of ecosystem health,” Pound said.
The UTA team behind the paper hopes
that watershed development, including wetland construction or stream
re-channeling to existing wetlands, may become a viable alternative to liming.
Liming is now widely used to reduce acidity in streams affected by acid rain
but many scientists question its long-term effectiveness.
The new paper is available online at
Funding for Passy’s work was provided
in part by the New York State Energy Research and Development Authority. The
Norman Hackerman Advanced Research Program, a project of the Texas Higher
Education Coordinating Board, as well as the US Geological Survey, the
Adirondack Lakes Survey Corporation and the New York State Department of
Environmental Conservation also provided support.
The University of Texas at Arlington is a
comprehensive research institution of more than 33,000 students and more than
2,200 faculty members in the heart of North Texas. Visit www.uta.edu to learn more.