Aquatic Sciences Meeting, Albuquerque 2001

SS10 Human Activities and Their Effects on Aquatic Ecosystems (Environmental Connections; Science and Society Connections)

Date: Monday, February 12, 2001, Time: 4:00:00 PM

Location: La Cienega

Valdes, L, M, University of Delaware, Lewes, USA, lexia@udel.edu

Hutchins, D, A, University of Delaware, Lewes, USA, dahutch@udel.edu

THE EFFECT OF MANIPULATING NITROGEN TO PHOSPHORUS RATIOS (N:P) ON ESTUARINE PHYTOPLANKTON COMMUNITY STRUCTURE

Traditionally, increases in the occurrence, distribution, and abundance of phytoplankton blooms have been attributed to increases in the absolute concentrations of nitrogen and phosphorus. However, eutrophication induced changes in the ratio of these nutrients are hypothesized to have caused a shift in phytoplankton community structure towards bloom-forming phytoplankton species through succession and competition for nutrients. In order to determine whether there is a shift in phytoplankton community structure under varying N:P ratios, this study manipulated inorganic N:P ratios in waters of the Delaware Inland Bays in controlled laboratory experiments. Nutrients were manipulated during the summers of 1999 and 2000 to yield the final N:P ratios of 1:1, 5:1, 16:1, 25:1, and ambient. Throughout the length of the experiment, daily size-fractionated Chlorophyll a, primary productivity, nutrient (inorganic and organic), cell enumeration and identification, CHN, and pigment analyses samples were taken. Preliminary data analysis and interpretation suggest that changes in the N:P ratio that result from nutrient loading could play a major role in determining phytoplankton species composition in estuarine systems.

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Aquatic Sciences Meeting, Albuquerque 2001

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