The Impact of a More Acidic Environment on Marine Microbes due to Ocean Acidification Experiment conducted by Maya Johnson
Introduction Purpose of the experiment
“ So much carbon dioxide is dissolving into the ocean so quickly that this natural buffering hasn’t been able to keep up, resulting in relatively rapidly dropping pH in surface waters. Such a relatively quick change in ocean chemistry doesn’t give marine life, which evolved over millions of years in an ocean with a generally stable pH, much time to adapt. - The Smithsonian Ocean Portal Team 3
Abstract As climate change has become an evermore prevalent issue, the consequence of ocean acidification has become increasingly alarming in terms of the potential effects on the environment, Marine ecosystems are at a great risk of decreasing significantly in biodiversity because many species are struggling and will continue to struggle adapting to the increasingly acidic environment (Bennett). Carbonate is a “building block” of the Earth’s oceans, and with the increased CO 2 levels in the ocean, the average pH is increasing as the carbonate ion levels are decreasing. The current ocean pH is 8.1, but is expected to decrease by 2100 to 7.7 - 7.8 (Bennett), which would make the ocean’s the most acidic they have ever been. However, not only can this impact the ocean’s composition, but the microbial species who inhabit the waters. Detrimental consequences for the earth may arise if marine microorganisms are not able to readily adapt to decreased pH levels resulting from ocean acidification. Marine microbes are the major primary producers in the earth’s oceans, making them also the primary, making them arguably the most crucial aspect of marine ecosystems (Hall). Therefore, this experiment delves into trying to examine the possible impact ocean acidification (and thus climate change) would have on marine microorganisms. Samples were taken from Mercer Lake. The samples were subcultured, isolated and grown on agar plates. The growth of Bacillus pseudomycoides , Bacillus paranthracis , and Bacillus tropicus was examined under varying concentrations of carbonic acid. The greatest number of colonies were observed in slightly basic environments with a decrease in microbial growth in environments with a pH less than 7. Such conclusions are significant because as CO 2 levels continue rising and the pH of the ocean decreases, it will have a negative impact on microbial populations which are beneficial to the proper balance of ecosystem functionality. 4
Hypothesis As the pH of the growth medium of the marine microbes decreases, the bacterial growth will decrease. Microbes inability to rapidly adapt to increasingly acidic environment ❏ Essential chemical reactions are sensitive to slight changes in pH ❏ Though some may be able to adapt, a majority will suffer ❏ 5
Procedure Obtain water samples from Mercer Isolate colonies through three Create carbonic acid by completing Subculture in LB and carbonic acid Lake phases of subculturing and plating the reaction between calcium mixture for 24 hours at 37 ℃ . Then, for 48 hours at 37 ℃ each time for carbonate and hydrochloric acid growth on agar plates for 24 hours purification at 37 ℃ . Plate 200 ul of water samples on Send plated isolated colonies to Using a test tube with an outlet Observe and record qualitative separate nutrient agar plates and GENEWIZ for sequencing tube, distribute the produced CO 2 results. Obtain photographs using a incubate for 48 hours at 37 ℃ into the water. Use litmus paper to light box to increase visibility of determine why pH is at 7 and 8. bacteria. 6
Materials Mercer Lake water samples Sterile dispensable Light box ❏ ❏ ❏ collected in sterile sample subculturing tubes Sharpie ❏ cups Culture spreaders Microwave ❏ ❏ Litmus paper pH test strips Nutrient agar (pH of 7.5) Laptop ❏ ❏ ❏ Thermometer Petri dishes Tape ❏ ❏ ❏ Micropipettes (20 uL, 200 Calcium carbonate Beakers (250 mL, 400 mL) ❏ ❏ ❏ uL, 1 mL) 0.1 N hydrochloric acid Trash bin ❏ ❏ Micropipette tips Safety goggles Tap water ❏ ❏ ❏ Gloves Apron ❏ ❏ Antibacterial soap Test tubes ❏ ❏ Incubator set at 37 ℃ Parafilm ❏ ❏ Test tube rack Paper straw ❏ ❏ 7
Data Qualitative data: photographs
Control Group: pH of 8 Bacillus pseudomycoides Bacillus paranthracis Bacillus tropicus 9
Experimental Group: pH of 7 Bacillus pseudomycoides Bacillus paranthracis Bacillus tropicus 10
Experimental Group: pH of 7.5 Bacillus pseudomycoides Bacillus paranthracis Bacillus tropicus 11
Tabular Comparison (relative) pH 8 (control) pH 7 pH 7.5 Bacillus pseudomycoides colony growth least colony growth most colony growth Bacillus paranthracis colony growth least colony growth most colony growth Bacillus tropicus colony growth least colony growth most colony growth 12
Analysis The results observed partially support the hypothesis stated that a decrease in environmental pH would result in a decrease of marine microbial growth. As was observed with all three analyzed bacterial species, the control environment (pH 8) had a relative amount of colony growth, the experimental group in an environment with a 7.5 pH environment exhibited the most colony growth, and the experimental group in an environment with a pH of 7 exhibited the least amount of colony growth. A conclusion that can be drawn from these results is that the three species of marine microbes are adaptable to pH changes that result in a overall slightly basic environment, however once the environment becomes neutral and closer to becoming acidic, many of the microbes’ chemical reactions cannot performed, resulting in decreased growth. A 0.5 pH change is significant in terms of marine ecosystems, therefore a drastic change was expected to occur. There was evidence of error in this experiment that could lead to it being considered inconclusive. The current pH of the ocean is 8.1, therefore since the control environment had a pH of 8, this plate was expected to exhibit the most growth; however, it was the 7.5 pH environment that did so. While the bacterial growth observed in the pH of 7 environment performed as expected, the results observed in the control and other experimental group were not as expected. Based off of the collected evidence, this experiment proved inconclusive on the impact ocean acidification would have on marine microbes. Further, despite knowing the negative impacts on marine multicellular organisms, this cannot be applied similarly to bacteria because of microbes’ ability to adapt more easily to an ever-changing environment. 13
Future Plans Continue research throughout the remained of the school year ❏ Examine other variables such as temperature and competition ❏ Establish and research a more specific methodology for measure ❏ pH once having created carbonic acid ***These were established prior to the current state of world affairs 14
Credits Special thank you to the instructors and advisors who assisted me throughout my research: ❏ Mrs. Sbarro ❏ Mrs. Benegal 15
Works Cited (APA Format) Abatenh, E., Gizaw, B., Tsegaye, Z., Tefera, G. (2018, January 18). Microbial Function on Climate Change - A Review . Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3686211/. Bennett, J. (Ed.). (2018, April). Ocean Acidification. Retrieved February 20, 2020, from https://www.google.com/amp/ocean.si.edu/ocean-life/invertebrates/ocean-acidification?amp. Coelho, F.J.R.C., Santos, A.L., Coimbra, J., Almeida, A., Cunha, A., Cleary, D.F.R., Calado, R., Gomes, N.C.M. (2013, April 23). Interactive effects of global climate change and pollution on marine microbes: the way ahead . Retrieved https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3686211/. 16
Works Cited (APA Format) Currie, A.R., Tait, K., Parry, H., Francisco-Mora, B., Hicks, N., Osborn, A.M., Widdicombe, S., Stahl, H. (2017, August 22). Marine Microbial Gene Abundance and Community Composition in Response to Ocean Acidification and Elevated Temperature in Two Contrasting Coastal Marine Sediments . Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5572232/. Hall, D., Santoro, A., & Laperriere, S. (2019, July 24). Marine Microbes. Retrieved March 4, 2020, from https://ocean.si.edu/ocean-life/microbes/marine-microbes. Rui, J., Li, J., Wang, S., An, J., Liu, W., Lin, Q., Yang, Y., He, Z., Li, X. (n.d.) Responses of Bacterial Communities to Simulated Climate Changes in Alpine Meadow Soil of the Qinghai-Tibet Plateau . Retrieved from https://aem.asm.org/content/81/17/6070. Shomu’s Biology. (2012, October 31). 16s rRNA and its use . Retrieved from https://youtu.be/wFMcTIEMVJk. 17
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