Overview:
Despite
commemoration of the 30th anniversary of the Clean Water Act of
1972, significant scientific and resource management challenges
remain in reaching the goal of protecting the biological integrity
of our Nations' water resources. Ecological studies conducted by
scientists of the NAWQA Program provide data, information and scientific
insights into the status, trends, and understanding of factors that
influence the biological integrity of streams and rivers. These
studies are conducted by investigative teams distributed throughout
the Nation, and are synthesized at regional and national scales
to understand how stream ecosystems may respond in differing ways
to the diverse natural and human factors present in the Nation.
During the Program's first decade of operation (1991 - 2001), ecological
studies were conducted to assess the occurrence and distribution
of algal, invertebrate, and fish communities in 59 study units.
These study units represented the dominant hydrologic systems nationwide
and are staggered in time with respect to implementation, high-intensity,
and low-intensity sampling periods. In the second decade of the
Program (2001 - 2011), ecological studies are being conducted in
42 study units as part of a long-term, trends monitoring network
or nationally guided topical studies designed to increase our understanding
of the factors that affect water quality. Biological sampling of
algal, invertebrate, and fish communities, and habitat assessments
are being conducted at 129 sites of the 146 sites making up the
surface water trends network. Three topical studies presently underway
in the Program involving large-scale ecological studies include:
(1) the effects of urbanization on stream ecosystems, (2) the effects
of nutrient enrichment on stream ecosystems, and (3) the accumulation
of mercury in aquatic organisms.
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