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Effects of Varying Levels of Nitrogen on Spirogyra sp. Growth Lauren Brubaker, Cassandra Maier, Kaitlin Skelly. Baylor University, Waco TX 76798 Materials and Methods Abstract
Introduc?on Effects of nutrients, including the toll of nitrogen levels, on algae cultures’ growth has increased greatly since Allen’s comment (1955). More recent studies show the photosynthesis rate is higher in algae cultures than in land plants since they are suspended in water. This allows for a higher absorpGon of nutrients and light wavelengths (James and Boriah, 2010). This leads to opGmal growth because algae has a higher efficiency when it is suspended in water. The study will examine effects of varying nitrogen concentraGons on Spirogyra sp. growth. It is hypothesized that there will be opGmal growth in the lower concentraGon of nitrogen. Figure 1: Cactus Miracle-­‐Gro and African Violet Miracle-­‐
Gro A Spirogyra sp. sample was taken from the Lake Waco Wetlands. 1200 mLs of disGlled water was added to twelve 1.6 L containers along with 0.3 g of Spirogyra sp. (Figure 3). This experiment used two liquid ferGlizers with N-­‐P-­‐K raGos of 2-­‐7-­‐7 and 7-­‐7-­‐7 (Figure 1). In four containers 5 mL of 2% liquid nitrogen ferGlizer was added. In four other containers, 5 mL of 7% liquid nitrogen ferGlizer was added. Four containers were kept at a control. Each week, filter paper was used to collect Spirogyra sp. from each container. The filter paper and Spirogyra sp. were weighed on a digital scale. Later the weight of the filter paper was subtracted. The growth was determined by comparing the change in mass per week. The 2% liquid nitrogen ferGlizer showed considerably more growth than the 7% liquid nitrogen ferGlizer and control (Figure 2). Discussion There was a relaGonship between the nitrogen concentraGon and Spirogyra sp. growth. This can be observed by the change in mass from week to week. The masses may not account for total Spirogyra sp. presence due to loss of parGcles during filtraGon. As Gme progressed, the algae began to wither away, without regard to the nitrogen concentraGon present. However, it is determined that the opGmal nitrogen level tested is 2%.
Average Spirogyra sp. growth over a three week span 0.7 Conclusion Literature Cited 0.6 0.575 0.5 0.45 0.4 0.3 Figure 3: The formaGon of the 12 containers under the growing light. The opGmal nitrogen level for Spirogyra sp. growth tested is 2%. The 7% liquid nitrogen ferGlizer was too high and resulted in algae cell apoptosis. Figure 2: Mass of Spirogyra sp. (grams) The purpose of this project was to detect the opGmal level of nitrogen suitable for algae growth. The method of measuring growth was calculaGng the mass of the collected Spirogyra sp. culture once a week. There were twelve containers: four of which were controls (no added nitrogen), four were filled with 2% nitrogen, and four were filled with 7% nitrogen. Five mL of the two ferGlizers were added to each of the four designated containers. 0.3 g of algae was added to each container as a beginning mass. AUer seven days, the Spirogyra sp. growth was measured by filtering the water from the containers and catching the algae in filter paper. The filter paper and Spirogyra sp. were weighed on a digital scale. Later the weight of the filter paper was subtracted. It was expected that the 2% nitrogen ferGlizer would produce opGmal algae growth. The results confirmed that 2% nitrogen produced the opGmal growth for the Spirogyra sp. culture. Results Control 2% N N2 0.3 N7 7% N 0.242 0.225 0.2 0.225 0.175 0.1 0 Week 1 Week 2 Time (weeks) Week 3 -­‐Boriah, Varun and Scoh C. James. (2010) “Modeling Algae Growth in an Open-­‐Channel Raceway.” Journal of Computa4onal Biology. Vol. 17, Issue 7. 895-­‐906. -­‐Allen, M. B. and Daniel I. Arnon. (1955) “Studies on Nitrogen-­‐Fixing Blue-­‐Green Algae.” American Society of Plant Biologists. Vol. 30, Issue 4. 366-­‐372. Acknowledgements A Special Thanks to: Marty L. Harvill, Ph.D., Baylor University Senior Biology Lecturer; Ms. Nora Schell, Lake Waco Wetlands Coordinator; Baylor University Dean of Arts and Science; Baylor University Biology Department; Mr. Dan Daugherty; Ms. Alex James