Jessica Harold Advisor: Dr. Michael Twiss Clarkson REU Program August 2, 2007

1. Phytoplankton Community Composition, Abundance, and Health on the International Section of the St. Lawrence River Jessica Harold Advisor: Dr. Michael Twiss Clarkson REU Program August 2, 2007

2. Outline • Importance • Hypothesis • Methods • Instruments • Results & Discussion

3. Why Study Phytoplankton of the St. Lawrence River? • The Great Lakes-St. Lawrence River System holds 18% of the world’s freshwater (Thorp et al. 2005) • Phytoplankton form the basis of aquatic food chains

4. Hypothesis • Phytoplankton biomass will decrease upon entry into the St. Lawrence River from Lake Ontario • Disruption of phytoplankton physiology (Lewis et al. 1984) • Increased predation by zooplankton and benthic grazers • Decreased nutrient availability • Cell loss from the water column due to increased flocculation (Ruiz et al. 2004) • Phytoplankton community composition will change due to changing environmental factors

5. Materials and Methods • 19 stations were sampled over a two day period • Phytoplankton • Health and composition determined by a FRRF and a FluoroProbe, respectively • Abundance determined using chlorophyll-a abundance

7. FluoroProbe • Measures phytoplankton biomass in each of four divisions Fast Repitition Rate Fluorometer (FRRF) • Determines photosynthetic efficiency of whole phytoplankton samples (Fv/Fm) • Photosynthetic efficiency is a measure of phytoplankton health

8. Nutrients • Water collected from a depth of 6 m using a 2 L Niskin bottle • Analyzed water to determine total phosphorus and dissolved silicate • Chlorophyll-a • Water is filtered and then chlorophyll-a is extracted from the filter paper using acetone • Fluorometer is used to determine abundance

9. Results • No significant changes in phytoplankton community composition were found along the transect • Dominated by Chlorophyta (green algae) and Euglenophyta • Both groups are typically abundant under eutrophic conditions (Kalff 2002).

10. Phytoplankton Abundance and Health • Photosynthetic efficiency remained relatively constant • Distinct trends seen in phytoplankton abundance

11. Nutrients • Total dissolved phosphorus remains constant • Dissolved silicate exhibits an interesting trend

12. Discussion • Total dissolved phosphorus and chlorophyll-a are not correlated • Phosphorus is not limiting • Silicate concentrations • Increase due to elevated turbulence as the river becomes isothermal

13. Phytoplankton abundance initially decreases, but then recovers • The decrease is not due to poor health • Hypothesis: decrease is due to increased predation or disrupted physiology • Increase in abundance • Hypothesis: phytoplankton have adapted to new environment, or predation has decreased

14. Acknowledgements • Advisor Dr. Michael Twiss • Tiffany Basara and Dave Page • Co-worker Kyleigh Gloska • Cristina Gauthier and all the REUs!

15. Questions?

17. Literature Ruiz, J., Macias, D, Peters, F. 2004. Turbulence increases the average settling velocity of phytoplankton cells. Proc. Nat. Acad. Sci. 101:17720-17724. Lewis, M. R., E. P. W. Horne, J. J. Cullen, N.S. Oakley & T. Platt. 1984. Turbulent motions may control phytoplankton photosynthesis in the upper ocean. Nature 311: 49-50; doi 10.1038/311049a0. Thorp, J.H., Lamberti, G.A., and Casper, A.F. 2005. St. Lawrence River Basin. In Rivers of North America, eds. A.C. Benke and C.E. Cushing, pp. 983-1018. Boston: Elsevier Academic Press. Kalff, Jacob. 2002. The Phytoplankton.In Limnology, p. 316. Upper Saddle River, New Jersey: Prentice Hall. Basu, B.K., Klaff, J., Pinel-Alloul, B. 2000. Midsummer plankton development along a temperate river: the St. Lawrence River. Can. J. Fish. Aquat. Sci. 57 (Suppl.1): 7-15.

18. FRRF details • The FRRF was programmed to measure the ratio of variable chlorophyll-a fluorescence (Fv) to maximal chlorophyll-a fluorescence (Fm) • Fo=basal chlorophyll-a fluorescence