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

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

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!

Questions?

Literature Ruiz, J., Macias, D, Peters, F Turbulence increases the average settling velocity of phytoplankton cells. Proc. Nat. Acad. Sci. 101: Lewis, M. R., E. P. W. Horne, J. J. Cullen, N.S. Oakley & T. Platt Turbulent motions may control phytoplankton photosynthesis in the upper ocean. Nature 311: 49-50; doi /311049a0. Thorp, J.H., Lamberti, G.A., and Casper, A.F St. Lawrence River Basin. In Rivers of North America, eds. A.C. Benke and C.E. Cushing, pp Boston: Elsevier Academic Press. Kalff, Jacob The Phytoplankton. In Limnology, p Upper Saddle River, New Jersey: Prentice Hall. Basu, B.K., Klaff, J., Pinel-Alloul, B 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