Can You C Yano Bacteria? (Can you see any bacteria?)

This summer, I researched how various sediments within the Red Cedar watershed effect the growth of cyanobacteria. Lake sediment was compared with bedrock sediment, meaning crushed rocks were used as sediment for treatment groups. The motive behind this was that if (climate change induced) storm events were to increase the weathering, or erosion of bedrocks, would this continue to increase cyanobacterial growth. The hope was to understand if all agricultural phosphorous runoff and urban runoff were to be completely stopped, would bedrock nutrients continue the growth of cyanobacteria in eutrophic lakes. This cyanobacteria I am referring to is also known as blue-green algae; however this name is misleading for they are bacteria a type of photosythetic bacteria. Not all species of cyanobacteria are indicators of poor water quality, but the ones that are can sometimes produce toxins hazardous to people and animals when they are in a high enough density and in the process of eutrophication they have the ability to unstabilize the balance of the once healthy aquatic ecosystem.


To test the effect of sediments on cyanobacterial growth, lake water from Lake Tainter was collected and filtered to remove organic debris and grazers, or zooplankton. Rock samples of the Lone Rock, Eau Claire, Wonewoc, and Oneota rock formations were collected from roadside outcrops and crushed into a fine sediment with a mortar and pestle. A few pounds of lake muck at the mouth of Wilson Creek flowing into Lake Menomin was collected. Some of the collected lake sediment was put in small handheld microbial fuel cells (MFC) for a month and a half. (Note: The microbial fuel cells used are basically systems that take the electrons through carbon fiber pads that microbes naturally emit and then those electrons are converted to voltage, or energy). The rock and lake sediment was dried at 105 °C so it could be accurately weighed of 0.5 grams and put in each test tube. The test tubes used were 50 mL centrifuge tubes. Three replicas were set-up for each treatment type. Added to each of these tubes were 40 mL of filtered lake water and 0.25 grams of cyanobacteria (which also contained algae naturally growing in the lake). The five treatments groups were of each of the sediment types: Lone Rock formation, Eau Claire formation, Wonewoc formation, Oneota rock group, lake mud, and mud of MFC's. For the three control groups, the first contained filtered lake water and cyanobacteria with nothing additional added, the second had a combination of dissolved synthetic potassium nitrate and potassium phosphate, and the third had synthetic dissolved nutrients of potassium nitrate, potassium phosphate, and ferrous sulfate. The synthetic nutrient solutions were added at a known concentration unlike the other treatments. Once set-up, the centrifuge tubes were put in an incubator lit with UV light and set at a temperature of 30 °C for 48 hours. Next, the tubes were taken out poured into a filtering system where the cyanobacteria were caught onto filter paper and a vaccuum sucked out the water from below it. Care was given not to pour sediment from the treatment groups onto the filters. The filters were dried in a standard convection oven and weighed. Then the sediment in the centrifuge tubes were dried, weighed, and calculated of their biomass within the sediment. Analysis was also done to measure the soluble phosphorous of the various sediments.

The result of this experiment was that the lake sediment produced the most cyanobacterial population growth. Legacy and background phosphorous runoff have gathered in the sediment over a long stretch of time beginning from before it was known that agricultural runoff, septic tank leakage, and urban runoff were so problematic for our water bodies. Legacy runoff refers to human produced runoff, whereas background runoff refers to natural bedrock sediment runoff.
The most soluble phosphorous was found in the lake sediment and MFC sediment. The anode (lower part of the microbial fuel cell) contained less soluble phosphorous than the cathode. An explanation for this could be that phosphorous was made soluble in the lower anode section of the mud by microbes and moved into the watery upper section of the mud within the MFC. Phosphorous tends to bind with nutrients such as aluminum, iron, and calcium in the sediment and does not stay in the water column for long. Of my research findings, more research would need to be done on this project to test the accuracy of the results with repetition of this experiment.

Recommendations from this experiment would be to make sure buffer zones, or vegetation, were planted surrounding the entirety of lakes and river bodies to mitigate further runoff from running into the water of either bedrock or agricultural and urban runoff. Although the bedrock did not increase cyanobacterial growth as much as the lake sediment had, there still was an increase so measures can be taken to prevent further runoff from effecting the surface waters. This is considering exposed rock formations and not the ones that are buried by vegetation or exposed to groundwater. As for the nutrients that are within the lake and are a combination of legacy and background runoff, efforts could be made to unbind phosphorous from the sediment and move it into the water column for aquatic plants to utilize, such as duckweed. When phosphorous is bound to other nutrients, it is unavailable to plants. Then, the aquatic plants can be removed from the lake as used as phosphorous containing compost for farms and/or garden before the plants decay and release the phosphorous back into the water again. To do this, one possibility would be to put a microbial fuel cell in the lake sediment on a larger scale. Tests would need to be done to see if this could work.

From this summer research experience, I have changed in the sense that I know the importance of patience and flexibility when running lab experiments, for there will be obstacles to work with and the need to fix what isn't working. Changed in the way that I feel more comfortable in talking to people with opposing views to my own and attempting to understand their differing views. Environmental and social issues can be overwhelming and daunting to try to solve, but I know we can do this and I want you to believe that too.