A study of the effect of ocean pH on the degree of bioluminescence in the dinoflagellate species Pyrocystis lunula
Charlotte Clegg
Stratford Hall
Floor Location : S 199 V

AbstractrnrnThis extended essay seeks to investigate the extent to which ocean pH affects the intensity of bioluminescence in dinoflagellates, specifically the species Pyrocystis lunula.rnThe investigation was performed by obtaining a culture of Pyrocystis lunula and culturing it to yield a suitable test population. The population was then divided into eleven population samples each containing 25mL, which yielded two population samples for each predetermined pH value (7.972, 8.054, 8.136, 8.218, 8.300 and 8.382) except the original pH 8.218 as there was insufficient volume. Using calculated volumes of 1.0x10-8mol/dm3 HCl and 1.0x10-6mol/dm3 Na2CO3 solutions, the pH of each sample was altered as specified. During scotophase, each sample was individually placed into a dark test cell and was mechanically stimulated to bioluminesce for 9 seconds during which the illumination levels inside the test cell were measured by a light sensor. Immediately after, a second trial was performed. The process was repeated a week later with slight variation, which is outlined further in the paper.rnIt was initially expected that altering the pH of each sample would show a clear and immediate detrimental effect on the intensity of bioluminescence due to the fact that the bioluminescent reaction is based on the enzyme luciferase, which would denature. However, due to the limited sample and trial numbers, results show weak relationships between pH and intensity of bioluminescence in dinoflagellates. Data analysis yields no significant trends; however, qualitative data indicates that population samples that experienced higher pH changes displayed lower percentage abundances remaining. Additionally, more basic conditions generally displayed a greater negative effect on cell growth than more acidic conditions. While significant trends with regard to the intensity of the bioluminescence were not apparent, qualitative data indicates a negative effect on dinoflagellate population growth when ocean pH is altered.rnrnWord Count: 293rn