Kurt D. Carpenter

Associations among fish assemblage structure and environmental variables in Willamette Basin streams, Oregon

Abstract As part of the U.S. Geological Surveys National Water-Quality Assessment Program, fish were collected from 24 selected stream sites in the Willamette Basin during 1993–1995 to determine the composition of the fish assemblages and their relation to the chemical and physical environment. Variance in fish relative abundance was greater among all sites than among spatially distinct reaches within a site (spatial variation) or among multiple sampled years at a site (temporal variation). Therefore, data from a single reach in an individual year was considered to be a reliable estimator of the fish assemblage structure at a site when the data were normalized by percent relative abundance. Multivariate classification and ordination were used to examine patterns in environmental variables and fish relative abundance over differing spatial scales (among versus within ecoregions). Across all ecoregions (all sites), fish assemblages were primarily structured along environmental gradients of water temperatur...

Relations of Habitat-Specific Algal Assemblages to Land Use and Water Chemistry in the Willamette Basin, Oregon

Benthic algal assemblages, water chemistry, and habitat were characterized at 25 stream sites in the Willamette Basin, Oregon, during low flow in 1994. Seventy-three algal samples yielded 420 taxa — mostly diatoms, blue-green algae, and green algae. Algal assemblages from depositional samples were strongly dominated by diatoms (76% mean relative abundance), whereas erosional samples were dominated by blue-green algae (68% mean relative abundance).Canonical correspondence analysis (CCA) of semiquantitative and qualitative (presence/absence) data sets identified four environmental variables (maximum specific conductance, % open canopy, pH, and drainage area) that were significant in describing patterns of algal taxa among sites. Based on CCA, four groups of sites were identified: streams in forested basins that supported oligotrophic taxa, such as Diatoma mesodon;small streams in agricultural and urban basins that contained a variety of eutrophic and nitrogen-heterotrophic algal taxa; larger rivers draining areas of mixed land use that supported planktonic, eutrophic, and nitrogen-heterotrophic algal taxa; and streams with severely degraded or absent riparian vegetation (> 75% open canopy) that were dominated by other planktonic, eutrophic, and nitrogen-heterotrophic algal taxa. Patterns in water chemistry were consistent with the algal autecological interpretations and clearly demonstrated relationships between land use, water quality, and algal distribution patterns.

Phosphorus and Nitrogen Legacy in a Restoration Wetland, Upper Klamath Lake, Oregon

The effects of sediment, ground-water, and surface-water processes on the timing, quantity, and mechanisms of N and P fluxes were investigated in the Wood River Wetland 5–7 years after agricultural practices ceased and seasonal and permanent wetland hydrologies were restored. Nutrient concentrations in standing water largely reflected ground water in winter, the largest annual water source in the closedbasin wetland. High concentrations of total P (22 mg L−1) and total N (30 mg L−1) accumulated in summer when water temperature, air temperature, and evapotranspiration were highest. High positive benthic fluxes of soluble reactive P and ammonium (NH4+-N) were measured in two sections of the study area in June and August, averaging 46 and 24 mg m−2 d−1, respectively. Nonetheless, a wetland mass balance simultaneously indicated a net loss of P and N by assimilation, denitrification (1.1–10.1 mg N m−2 h−1), or solute repartitioning. High nutrient concentrations pose a risk for water quality management. Shifts in the timing and magnitude of water inflows and outflows may improve biogeochemical function and water quality by optimizing seed germination and aquatic plant distribution, which would be especially important if the Wood River Wetland was reconnected with hyper-eutrophic Agency Lake.

Plankton communities and summertime declines in algal abundance associated with low dissolved oxygen in the Tualatin River, Oregon

2. Reduced algal “seed source” to inoculate the river. Small reductions in chlorophyll-a concentrations in the upper river have led to downstream declines (FIG. 2). Although such inoculation is important for maintaining DO, inputs of nuisance algae can be problematic. The inoculation of blue-green algae in June 2008 translated into a large bloom of toxin-producing blue-green algae (Anabaena) in the lower river -the largest in decades (below right).

Seasonal phosphorus and nitrogen dynamics of open water during restoration of the Wood River Wetland, Klamath Falls, Oregon, USA

Draining wetlands for agricultural production is a global phenomenon that has often led to impaired ecosystem function, loss of connectivity with adjacent waters, and water quality impacts from agricultural runoff. Loss of wetlands shortens the time it takes rainfall to move through the catchment, contributes to soi! erosion, and hastens nutrient and pollutant release into water bodies. In the United States, 22 states have lost 50% or more of their original wetlands in the last 2 centuries (DAHL 1990). Though efforts to conserve wetlands have increased, restoration fali s short of loss rates. Over the past 50 years, approximately 30 000 ac o f wetland adjacent to Upper Klamath Lake and connected Agency Lake (Fig. l) have been diked and drained for livestock grazing and crop cultivation. Water quality in Upper Klamath Lake has simultaneously declined, and phosphorus (P) inputs from rivers that once flowed through wetland have resulted in large-scale algae blooms (predominantly Aphanizomenon flos-aquae), periodically depleting Üz levels below those required by fish, including the endangered short-nosed ( Chasmistes brevirostris) and Lost River suckers (Deltistes luxatus; SNYDER & MoRACE 1997). Wetland draining has also lowered the water table, which has increased air and oxygenated-water movement through subsurface soils facilitating aerobic peat decomposition and release of carbon (C), nitrogen (N), and P (SNYDER & MoRACE 1997). Land surrounding the north end of the lakes has subsided 4-5 feet, requiring 1evees to prevent flooding of drained wetlands. A resource management p1an to restore the Wood River Wetland was initiated in 1996 to provide long-term improvement in water quality and quantity entering Agency Lake and restore and enhance wetland habitat (U.S. BuREAU oF LAND MANAGEMENT 2005). In 2003 to 2005, we investigated the spatial and temporal variations in water chemistry during the initia! phase of wetland recovery to assess its ro1e as a nutrient source or sink. During the study, water flow through the wet1and was nominal, and surface-water nutrients accumu1ated from sediment release and evapoconcentration. The results suggest ecosystem function had not fully recovered to process the large quantities of standing nutrients in the wetland.