The effect of Manganese on the native algal species Pseudokirchneriella subcapitata Emily Christine Siders Marietta College Introduction Manganese is one of the main pollutants in the Marietta, Ohio area due to Eramet. Eramet is the leading producer of ferromanganese alloys in the world as well as producing manganese based products for the chemical industry. According to a 2005 investigation by the US Department of Health and Human Services, the Ohio River in Washington County, Ohio has a manganese concentration of approximately 5 parts per million. The elevated concentrations released into the environment may have an effect on organisms that inhabit the area. Pseudokirchneriella subcapitata is a distinct crescent shaped green micro alga that is found in many freshwater aquatic ecosystems, including the Ohio River. Its short life cycle as well as the little space and care that is required for it to flourish makes Pseudokirchneriella subcapitata an ideal organism for laboratory use in toxicology studies as a bioindicator. Bioindicators are used to monitor the health of an environment or ecosystem. The purpose of this experiment was to look at the effect of manganese on the growth of an algal species native to the Ohio River in Washington County, Ohio. Further, to develop an understanding of toxicology as well as build on basic lab techniques. It was hypothesized that the lowest concentration of manganese (5 parts per million) will not have a significant effect on the population growth of Pseudokirchneriella subcapitata, while the higher concentrations of 50 and 500 parts per million will have a detrimental effect on the population growth. Methods Three 50 ml flasks were used for each of the four concentrations. Each flask contained: 9 ml of ultra pure water 2 ml of Pseudokirchneriella subcapitata 9 ml of Alga-grow Medium For the control condition, no MnCl 2.4H 2 0 was present in the Alga-grow Medium, while 5, 50, or 500 ppm was present in each experimental condition. The Twelve flasks were stirred continuously on a shaker under a 12 hour light/dark cycle. Each concentration of the Pseudokirchneriella subcapitata cells were counted daily for five days with a hemocytometer then calculated for total number of cells in each flask. The formula is as follows: cells per milliliter = n/10 x 250,000 where n = total number of counted cells A total of three replications were conducted and the data were analyzed using SPSS. Results The overall growth rates (in cells/ml/day) for each condition are shown in Table I. Figure I illustrates the cumulative daily averages for each condition throughout the trials. A 4 (conditions) x 5 (day) Mixed Factor ANOVA was used to analyze the data. There was a significant main effect of condition F (3,32) = 26.71, p <.001 as well as a significant interaction of condition and day, F (12,128) 16.77, p <.001. All conditions were significantly different except for the 50 ppm and 500 ppm ( p =.312). Discussion The lowest concentration of manganese (5 ppm) did not have a significant effect on the population growth of Pseudokirchneriella subcapitata, while the higher concentrations of 50 and 500 ppm did have a detrimental effect on the population growth. This research suggests that increasing levels of manganese may cause a decline in native alga species, which has significant implications for the Washington County, Ohio area. In future research, more replications as well as concentrations under 50 ppm should be used due to the significant decline of growth seen at the 50 ppm condition. References available upon request. Control5 ppm50 ppm500 ppm 227,00081,7007,8001,000 Table I: Overall growth rates (cells/ml/day) Acknowledgements Dr. Brown, Dr. Hogan, Mrs. Jarrell, Biology senior capstone class, Dr. McCabe, Dr. Pate, Dr. McKay, Dr. Tschunko, Marietta College Biology Department, Andrea Marion, Allison Rhea, Christiana Hilditch, and David Borrelli. Figure I: Cumulative average cell counts for trials I, II, and III