Aquatic Ecology: Cycle I Activities (1991 - 2001)

Aquatic Ecology: Study Design

Ecological Studies are an integral part of the approach used by NAWQA to assess water quality. Information on biological communities and habitat characteristics contributes to the conceptual model of factors that affect water quality and to improved understanding of the relation among physical, chemical, and biological characteristics of streams. Fixed-Reach Assessments and Intensive Ecological Assessments provide an initial evaluation of the linkages among physical, chemical, and biological conditions within the Study Unit. Ecological Synoptic Studies provide a much more complete geographic representation within the Study Unit, but for a more limited set of physical, chemical, and biological characteristics.

Ecological Studies: Fixed Reach Assessment

• The richest targeted habitat samples were collected from the habitat expected to yield the greatest diversity of organisms and therefore expected to be the most sensitive to change because potential changes are the largest. Relative abundance data were obtained. 
• The depositional targeted habitat samples were collected where fine grained sediments are most abundant. These samples were expected to be sensitive to contaminants adsorbed to sediment particles because it samples organisms most closely associated with that habitat. Relative abundance data were obtained.
• The qualitative multi-habitat samples were collected from all habitat types present to establish species richness. These samples were expected to be sensitive to loss of sensitive species that might be missed by the more specific samples. Only presence/absence data were obtained. A single fish sample was taken, providing data on relative abundance of species at the site.

Ecological Studies: Intensive Ecological Assessment

The Intensive Ecological Assessment was done to provide information on spatial and temporal variability of biological communities and habitat characteristics. Spatial variability was addressed by sampling three similar reaches at three stream sites (Multi-Reach Assessment). Temporal variability was addressed by sampling one reach at each site annually during the three-year intensive data collection period (1993, 1994, 1995) (Single-Reach, Multi-Year Assessment).

• Multi-Reach Assessment: fish, invertebrates, and algae were collected and identified, and habitat characteristics were described for three reaches at each of three sites (Tuolumne River at Modesto, Stanislaus River near Ripon, and Merced River at River Road sites) in 1995.
• Single-Reach, Multi-Year Assessment: One reach on the three aforementioned sites and on the Merced River at Happy Isles Bridge site were sampled in 1993, 1994, and 1995.

Ecological Studies: Community Assessment Synoptic

The Ecological Synoptic Study completed in 1994 had two primary purposes. First, additional sites were sampled on the lower mainstem San Joaquin River and the Stanislaus, Tuolumne, and Merced Rivers, below the reservoirs to improve spatial coverage of the Fixed-Reach Assessment on each river and to facilitate comparison of ecological communities among rivers. Second, a number of locations upstream of Lake McClure on the Merced River were sampled, including several sites in Yosemite National Park. Data from these samples were used to analyze the ecological communities of the least-altered Sierra Nevada river in the study unit and to establish a database of background information for future studies.

Aquatic Ecology Data

Aquatic Ecology Data include descriptions of fish, benthic invertebrate and algal communities, and habitat. At this time only the fish data is available.

Low-Intensity Phase Sampling

Biological data collection include annual single-reach assessments of fish, invertebrate, and algal communities, and Level I habitat characterization.