Aquatic Sciences Meeting, Albuquerque 2001

CS41 Phytoplankton: Nutrient Dynamics and Physiology

Date: Friday, February 16, 2001, Time: 12:00:00 PM

Location: Galisteo

Hutchins, D, A, University of Delaware, College of Marine Studies, Lewes, DE, USA, dahutch@udel.edu

Pustizzi, F, , University of Delaware, College of Marine Studies, Lewes, DE, USA, franp@udel.edu

Hare, C, , University of Delaware, College of Marine Studies, Lewes, DE, USA, schroff@udel.edu

Trick, C, G, University of Western Ontario, London, ON, Canada, cyano@julian.uwo.ca

DiTullio, G, R, University of Charleston, Charleston, SC, USA, ditullioj@cofc.edu

UPWELLED NUTRIENT AND IRON EFFECTS ON PHYTOPLANKTON COMMUNITY STRUCTURE INVESTIGATED USING SHIPBOARD NATURAL COMMUNITY CHEMOSTAT SYSTEMS

Shipboard 'growout' experiments where nutrients are added in a single large pulse are analogous to laboratory 'batch' cultures, producing nutrient perturbation effects and non steady-state conditions. In many marine ecosystems, however, nutrient supplies often don't arrive in discrete large pulses, but rather as continuous low-level inputs from upwelling or eddy diffusion. We developed a natural community continuous culture (chemostat) shipboard incubation system that delivers nutrients at realistic continuous input rates and concentrations to simulate real-world vertical advection processes. Flow cytometry, pigment HPLC and epifluorescence microscopy were used to understand how natural ranges in nutrient input rates control phytoplankton community structure. Low-level continuous major nutrient additions in the oligotrophic Atlantic suggest that cyclonic eddy events will shift community composition towards dominance by diatoms and particular prokaryotic taxa. Realistic simulations of variable upwelled iron inputs in the Equatorial Pacific also demonstrate dramatic changes in community structure. Natural community chemostat systems offer unique insights into the effects of sustained, low-level nutrient fluxes on phytoplankton community composition in regimes dominated by these types of inputs, including the HNLC areas and the oligotrophic central gyres.

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Aquatic Sciences Meeting, Albuquerque 2001

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