112.3112.3Jessica L. Feeser, M. Elise Lauterbur & Jennifer L. Soong

Research Project for Systems Ecology (ENVS 316), Fall ’06Oberlin College, Oberlin OH

Background Findings Cont’d.

References

Goals & Hypotheses

Methods

• The 19 sampling locations were selected to provide a comprehensive spatial resolutionthroughout the 5 mile section of the stream. Theaccessibility of the points was also taken into consideration. See fig. 1, below, for sampling locations.

• We collected water samples from the stream on two days during the fall, once 48 hours after a storm event, and once during a low flow period. We expected nutrient concentrations to be near their highest at 48 hours after the storm, as suggested by Cummings et al. (2004).

• BOD, pH, Turbidity, and [NH4+] of the water

samples were analyzed in the lab according to the protocols in Methods for Analyzing Aquatic Ecosystems (Petersen 2006).

• NO32-, NO2

-, PO43-, and Cl- concentrations

were measured using ion chromatography according to Methods for Analyzing Aquatic Ecosystems (Petersen 2006).

• Because Cl- is not a nutrient, and is therefore not affected by biological processes, we were able to use it as a passive tracer.

Findings

• The regression of NOx against Cl- concentrations reveals that NOx concentrations arebeing affected by biological processing during low flow, but not during the post-storm period.

• A similar regression of PO43- against Cl-

indicated that in-stream processes were not having much of an affect on PO4

3- concentrations.

• Because in stream processing influences NOx concentrations during low flow, we used the post-storm data to examine nutrient inputs and dilutions through the varying landscape.

Plum Creek is classified as a grade-1 tributary of the Black River, which is located in North East Ohio and drains into Lake Erie. Plum Creek’s headwaters are located in agricultural land east of the City of Oberlin, and the creek runs through a golf course, a small forested area (arboretum), and the City of Oberlin, before receiving the effluent of the Oberlin’s waste water treatment plant (WWTP) to the west of the city.

Eutrophication caused by high levels of PO4

3- is a major problem in Lake Erie. In order to understand how Plum Creek’s nutrient contributions to Lake Erie can be reduced, it is necessary to determine how different types of land use affect the input of nutrients into Plum Creek, and how these nutrients are processed within the stream.

There is little knowledge about how varying land use within Plum Creek’s watershed affects the nutrient dynamics of the creek. While there have been previous studies addressing this issue, we feel that none have examined an adequate number of sample locations to obtain a comprehensive understanding of the creek’s dynamics.

Cummings, J., T. Reed, K. Weinberger. 2004. “The city of Oberlin’s effect on the Plum Creek watershed during a storm event: variation in upstream and downstream water quality during and after storm water run-off as a function of urban land cover” Report for Oberlin College ENVS 316.

Petersen, J. 2006. “Methods for Analyzing Aquatic Ecosystems”

Goals

• To quantify water quality at multiple points along Plum Creek during typical autumn conditions

• To identify point and non-point sources of pollution within Plum Creek’s watershed

• To determine how biological processing within the stream affects nutrient concentrations during low flow and post-storm periods

Hypotheses

• We hypothesized that concentrations of nutrients would increase in the agricultural and golf course regions, and decrease throughout the arboretum and the city.

• We expected that, due to the constant flow of water, biological activity would have little effect on nutrient concentrations within the studied portion of the stream.

Nutrient concentrations along an agricultural/urban stream during low flow and post-storm periods as a

function of varying land use and biological processing

• Because fertilizers are generally applied in the spring, it will be necessary to do a full-year study in order to fully understand the effects of land use on the stream’s water quality.

• Studying the stream’s flow rate at the time of sampling will allow quantification of the net change in nutrient levels between two points.

• Future studies must identify major polluters of PO4

3- within Plum Creek’s watershed before steps can be taken to minimize Oberlin’s contributions to eutrophication in Lake Erie.

Future Studies

Figure 1. Map of Plum Creek

Locations are labeled by their distance from the first sample point, located in the creek’s headwaters to the west of Oberlin.

Standardized nutrient concentrations (post-storm)

• NOx concentrations increase throughout the agricultural and golf course portions of the stream. This indicates that these areas are non-point sources of nitrogen. The peak in nitrogen concentration at the boundary between the golf course and the arboretum indicates a drastic difference in the effects of these two forms of land use on the creek’s water quality.

• The nutrient concentrations in the arboretum are inconclusive. This could be a result of its small size or of the city’s storm-drainage system draining into the stream as it flows through the arboretum.

• The highest fluctuation in nutrient concentrations occur as the stream flows through the city, though nutrient concentrations decrease overall.

• The peaks in the city are likely due to inputs from Oberlin’s storm-drainage system. The overall decrease in concentration suggests that urban runoff dilutes the nutrients.

• All ions reach their maximum concentrations at the sampling point immediately past the WWTP. The WWTP is a point-source of pollutants.