Aquatic Sciences Meeting, Albuquerque 2001

CS41 Phytoplankton: Nutrient Dynamics and Physiology

Date: Friday, February 16, 2001, Time: 10:45:00 AM

Location: Galisteo

Kemper, K, , University of Maine, Orono, USA, kkemper@lumcon.edu

Townsend, D, W, University of Maine, Orono, USA, davidt@maine.maine.edu

DYNAMICS OF SILICATE, NITRATE+NITRITE, AND THE LATE SPRING PHYTOPLANKTON COMMUNITY ON GEORGES BANK, MAY AND JUNE 1998

It has previously been assumed that Georges Bank, a highly productive region, would be a diatom dominated phytoplankton community throughout the summer. We collected phytoplankton, nutrient and chlorophyll a samples in May and June 1998. The distribution of phytoplankton taxa was compared to hydrography and nutrient concentrations. In May 1998, Georges Bank was dominated by monads, had low chlorophyll a concentrations (<1.5 micrograms l-1), and vertical stratification was found only off the bank. Nitrate+nitrite concentrations were low, while silicate concentrations were highly variable, reaching 15 micromolar, indicating silicate regeneration with seasonal warming. The front system in May was weakly developed. By June, the front had intensified, and the phytoplankton population had shifted to a diatom dominated system. Diatoms were most abundant on the Northern flank and Northeast Peak. Silicate and nitrate+nitrite concentrations remained low in June, but were elevated at the Northeast Peak. It is evident that Georges Bank is not always a diatom dominated system. Variability in the timing in the summer front system development after the spring bloom may cause large differences in the taxonomic composition of the phytoplankton community between years.

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Aquatic Sciences Meeting, Albuquerque 2001

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