River Experiment - Lab Instructor: Emily Pavia; Lab Write Up PDF

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Lab Instructor: Emily Pavia; Lab Write Up...

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Jade Tamondong Observing the effects of fertilizer on macroinvertebrates found in the American River Introduction The American River is an ecosystem that runs through the city of Sacramento. It is home to many different species, both in and around the river. Since the American River runs through an urban area where a lot of human activity occurs, it is important that we understand what factors can potentially harm the species, specifically macroinvertebrates, that live in the river. Other studies have been done on rivers that have undergone certain changes that ultimately changed the composition of the river which had an effect on the macroinvertebrates in the water. For example, streams going through conventional farming sites have fertilizer and pesticides exposed to it and resulted in a macroinvertebrate decline (Magbanua et al. 2010). Another study was done on the streams in the alpine ecosystem which showed that the macroinvertebrates were strongly affected by meltwater contribution (Brown et al. 2007). In this lab, we are observing the effects of fertilizer in the American River and how it affects the species abundance of this ecosystem. I hypothesize that the species abundance will decrease when the fertilizer is added to the ecosystem. I believe this will happen because I think that the fertilizer will cause a process called eutrophication, which is the excessive amount of nutrients in a body of water. I think that eutrophication will create an increase of algae, which will cause there to be limited sunlight passing through the river. This will ultimately change the composition of the river and effect the macroinvertebrates. Methods We collected sediment from the American River and kept it in two separate aquariums. One aquarium had fertilizer added to it, while the other one was left unchanged (control). We then took small samples from each aquarium and sifted through them using nylon in order to obtain the sediment. Once the sediment was obtained, we placed a small sample of it onto a microscope depression slide and a bigger sample on a dish that will be used for the dissecting microscope. With both microscopes, we were able to count and identify the different macroinvertebrates living in the sediment. We also tested the absorbance of the water from both tanks using the spectrometer. We then waited 3 weeks and repeated this step over again. This period of time allowed the species living in the aquariums to adjust to the changed environment, also known as the acclimation period. Once all of the data was collected, we found the mean and standard deviations of the species abundance for the control and fertilized tank before and after the acclimation period. After that we conducted multiple t-tests in order to get p-values which gave us evidence that either supported or rejected our hypothesis. Results The average and standard deviation of species abundance in the control tank before the acclimation period is 1.25±1.28 (±SD); the absorbance reading had an average of 0.03. The average and standard deviation of species abundance in the fertilized tank before acclimation period is 1±1.41 (±SD); the absorbance reading had an average of 0.04. The average and

standard deviation of species abundance in the control tank after the 2 acclimation period is 2.25±1.75 (±SD); the 1.5 absorbance reading had an average of 0.13. The 1 average and standard deviation of the species 0.5 abundance in the fertilized tank after the acclimation 0 Control Before Treatment Before Control After Treatment After period is 1.63±1.69 Figure 1: The averages of species richness in control and treatment tanks before and after acclimation period. (Error bars represents standard deviation) (±SD); the absorbance reading had an average of 0.23. The t-test we conducted on the control tank before acclimation period and fertilized tank before acclimation period resulted in a p-value of 0.72. The t-test we conducted on the control tank after acclimation period and fertilized tank after acclimation period resulted in a p-value of 0.48. The t-test we conducted on the control tank before acclimation period and control tank after acclimation period resulted in a p-value of 0.21. The t-test we conducted on the fertilized tank before acclimation period and fertilized tank after acclimation period resulted in a p-value of 0.44. Ave rage sofSpe cie sAbundanc e

2.5

Discussion The results in Figure 1 show the averages and standard deviations of the species richness in the control and treated tanks before and after the acclimation period....