The Effects of Beaver Dams on Stream Chemistry

Methods• We sampled upstream and downstream of two dams

located on the Cache River (Figure 2). Site 2 was sampled three times (3-1-14, 3-20-14, 3-22-14), while site 1 was sampled only once (3-1-14) due to high water submerging the dam on other sample dates.

• Nutrient levels (phosphate, nitrate, nitrite & ammonia) were measured with HACH® Aquacheck Water Quality Test strips.

• Turbidity was measured by collecting water samples and analyzing them in the lab using 2020 LaMotte Turbidimeter.

• Chlorophyll-a was measured by collecting water samples, filtering 100 mL of them through a glass fiber filter, extracting filters in 90% buffered acetone, and performing fluorometric analysis with a Turner Aquaflor fluorometer at a 430 nm wavelength.

• Dissolved oxygen was measured with a YSI-PRO probe.• pH was measured using LaMotte pH Test Strips.• Data were analyzed using a paired-sample t-test,

comparing upstream to downstream.

Introduction & Objectives

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Acknowledgements

Discussion

Results

We found no significant differences in any of the water chemistry variables upstream and downstream of the beaver dams. Previous studies have found that beavers reduce turbidity downstream, which in turn can decrease temperature because solids in the water absorb more heat (USEPA 2012). This temperature decrease can increase dissolved oxygen levels because colder water holds more oxygen.Turbidity, a measure of total suspended solids, can have negative impacts on plants and animals by inhibiting growth and feeding. We expected turbidity to be higher upstream than downstream because dams can filter sediment and other substances out of the water, and materials can accumulate in the beaver pond as stream water backs up against a dam. Bioturbation by the beavers can also lead to high turbidity (Bird et. al 2011).Beavers can also affect nutrient cycling through excretion as well as alteration of macroinvertebrate and plant community structure (McDowell & Naiman 1986, Huntly 1995). Carpenter et al. (1993) found higher nutrient levels at active beaver sites compared to abandoned sites. This relates to our research by outlining possible variables that could have affected our data when measuring nutrient levels. It’s likely that we did not see significant differences due to small sample sizes related to time restrictions, high water levels, and high variability of some parameters. With additional sampling at different times of year as well and more sites, our study could be more conclusive.

The North American beaver (Castor canadensis) is considered an ecosystem engineer due to its ability to alter channel geomorphology and hydrology, increase retention of sediment and organic matter, and modify structures in its habitat (Naiman 1986). Prior to the early 20th century, Castor canadensis was nearly hunted to extinction (Hill 1982), but conservation efforts have since aided in their recovery. The current U.S. population is around 6-12 million (Naiman et al., 1986). While beavers are important to many ecological processes, overabundance of dams can be problematic for humans, causing flooding in residential areas and agricultural fields. Beaver ponds can be most effectively managed through water level control using different materials as drains (N.C. Wildlife Resource Commission 2014). Recent research on the ecological impacts of beaver activity is sparse, but understanding the impacts of beavers on ecosystem structure and function is crucial to management efforts for both beaver populations and stream and wetland habitats.

B.C. Corbett, K.A. Baumann1, H.M. Rantala1, and M. R. Whiles1

1Department of Zoology and Center for Ecology, Southern Illinois University Carbondale

Carpenter, K., Dawson, K., Reyes, B., Thompson, L. (1993). Water chemistry responses to vacant and active beaver dams [Abstract]. Biological State, University of Michigan (UMBS).

Dewey, T.. Photograph of Castor canadensis. Retrieved March 30, 2014, from: http://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=1090

Naiman, R. J. (1986). Ecosystem Alteration of Boreal Forest Streams By Beaver (Castor Canadensis). Ecology, 67(5), 1254-1269

Rosell, F., Orsolya, B., Collen, P., Parker, H. (2005). Ecological impact of beavers Castor fibre & Castor canadensis and their ability to modify ecosystems. Mammal Review, 35.

USEPA (2012) Turbidity. Water Monitoring & Assessment.

Bird, B., O’Brien, M., Petersen, M. (2011) Beaver and Climate Change Adaptation in North America. WildEarth Guardians.

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Upstream

Literature Cited

Funding was provided by the SIU Research Rookie program. D. McClain and M. Oliver assisted in locating beaver dams.

Figure 2. Location of study sites on the Cache River. Modified from Little River Research & Design, http://www.emriver.com/ Accessed 31 March 2014.

Figure 3. Turbidity (NTU) upstream and downstream of each dam (p<0.05). Site 2 was sampled on three dates (March 1, March 30, and March 22), displayed chronologically left to right.

Figure 1. Current distribution of the North American beaver. From Canadian Geographic, http://www.canadiangeographic.ca/ Accessed 31 March 2014.

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Figure 4. Chlorophyll-a (µg/L) upstream and downstream of each dam (p<.05). Site 2 was sampled on three dates,(March 1, March 30, and March 22), displayed chronologically left to right.

Figure 5. Sampling at site 2, 3/22/14.