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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. Outline. Importance Hypothesis Methods Instruments Results & Discussion.
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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
Outline • Importance • Hypothesis • Methods • Instruments • Results & Discussion
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
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
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
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
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
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).
Phytoplankton Abundance and Health • Photosynthetic efficiency remained relatively constant • Distinct trends seen in phytoplankton abundance
Nutrients • Total dissolved phosphorus remains constant • Dissolved silicate exhibits an interesting trend
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
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
Acknowledgements • Advisor Dr. Michael Twiss • Tiffany Basara and Dave Page • Co-worker Kyleigh Gloska • Cristina Gauthier and all the REUs!
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.
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