Examination of Lake Life
Bio 181 Section 001k
The goal of the lab was to determine the health of the aquatic community of Lake Wheeler. Different sediment samples were taken to be tested and observed in many ways. The water temperature, dissolved oxygen, and water clarity were also tested with different tools. The health of Lake Wheeler was tested through coliform samples that were taken to see if it is safe for humans. The whole experiment was a unique and enjoyable experiment. Introduction
The aquatic communities lab goal was to evaluate the overall healthiness of Lake Wheeler. The evaluation is performed by testing several aspects of the lake water. Some of the tests were measuring the pH, Secchi depth, compensation depth, dissolved oxygen, and temperature at different depths, sediment samples from different zones, eco plates, and coliform tests. The pH test calculates the acidity of the lake water, which should be close to neutral. Secchi depth testing is to find the average water clarity and light penetration. The compensation depth is the depth at which only 1% of surface light penetrates the water column (NC State Department of Bio 2013, p39). Sediment samples taken from various zones show what is living in the sediment. Coliform testing is to check for the presence of coliform bacteria. Methods
This lab contained many different tests to determine the quality of the aquatic community at Lake Wheeler. The first test was to find dissolved oxygen and the temperature at different depths of the lake. To do this test, a submersible probe was lowered by a cable at 50 cm increments into the lake water and at every increment; the dissolved oxygen was measured along with the water temperature. The measurements were then recorded, averaged, and then reported to the class. Test Two was collecting samples of plankton in the lake. The procedure for this involved using a “Schindler-Patalas trap” that was lowered into the water to collect water at different depths (NC State Department of Bio 2013, p38). The trap is made of a Plexiglas sample box supported by a metal frame with hinged doors on top and bottom. The doors allowed water to flow through the box so the box could sink faster and then take a 12- liter sample once the doors are closed. Once the box is brought back up from its different sample depths in 50 cm increments, the sample was then filtered through a sample tube with a plankton filter. The sample left in the tube is placed in a labeled container for that depth and saved for testing. Once back in the lab, all of the samples were put into fish bowls containing only samples from that depth. A pipette is used to take a sample from the fishbowl. The sample is used to prepare slides using one-to- two drops per slide and placing a cover slip over it to observe under a microscope. Using books and keys all organisms observed were identified and deemed autotroph or heterotroph. All of the data was recorded in a table containing the organisms found at each depth. The third test was to determine the presence of “coliform bacteria” in the lake water (NC State Department of Bio 2013, p38). This was done by taking samples in tubes that were filled to 2/3 with the surface water from two different locations. One of the samples was taken from an area that we thought to be the cleanest area while the other was taken from an area we thought to be the dirtiest. The sample tubes labeled were with “clean” and “dirty.” Once back in the lab, we acquired two tubes of “lauryl tryptose nutrient broth” and labeled each tube with clean or dirty (NC State Department of Bio 2013, p45). Then, use an alcohol flame and flame the mouth of the nutrient broth tube for 3 seconds. After that, add one mL of lake water using a sterile pipette into each tube of nutrient broth. The cap is then replaced back on the tubes and the tubes are inverted once to make sure the sample is mixed and makes it into the small internal vial....
References: Lenntech B.V. Why Dissolved Oxygen is important. 2013 Oct 24.
North Carolina State University Department of Biology. 2013. Aquatic Communities: Field Sampling Techniques, Species Identification, and Community Assessment. Bio 181 General Biology I Laboratory Manual. Plymouth:Hayden-Mcneil Publishing. p33-52
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