The effect of Manganese on the native algal
species Pseudokirchneriella subcapitata
Emily Christine Siders
Marietta College
Introduction
Methods
Results
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.
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 MnCl2.4H20 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:
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.
Control
227,000
A total of three replications were conducted and
the data were analyzed using SPSS.
1400000
Average Cell Count (cells/ml)
1200000
y = 226944x - 95278
800000
600000
y = 81667x + 48333
400000
200000
y = -7777.8x + 121667
y = 1018.5x + 25093
0
0
1
2
3
4
Day
Control
5 ppm
50 ppm
500 ppm
5
50 ppm
7,800
500 ppm
1,000
Discussion
Figure I: Cumulative average cell counts for trials I, II, and III
1000000
5 ppm
81,700
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).
cells per milliliter = n/10 x 250,000
where n = total number of counted cells
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.
Table I: Overall growth rates (cells/ml/day)
6
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.