Aquatic Sciences Meeting, Albuquerque 2001

CS41 Phytoplankton: Nutrient Dynamics and Physiology

Date: Friday, February 16, 2001, Time: 8:30:00 AM

Location: Galisteo

Murrell, M, C, US EPA, Gulf Breeze, FL, USA, murrell.michael@epa.gov

Lores, E, M, US EPA, Gulf Breeze, FL, USA, lores.emile@epa.gov

PLANKTON DYNAMICS IN PENSACOLA BAY, FL, USA: A WARM TEMPERATE ESTUARY OF THE NORTHERN GULF OF MEXICO

A seasonal study was conducted in Pensacola Bay, Florida, USA to characterize the seasonal dynamics of nutrients, phytoplankton and bacterioplankton. Monthly samples were collected from 5 sites spanning the salinity gradient. Bulk parameters included chlorophyll, nutrients, PC/PN, and DOC. Phytoplankton community composition was determined by size-fractionated chlorophyll analysis and cyanobacterial direct counts. Bacterioplankton parameters included biomass via direct counts, production via L-leucine incorporation, and ectoenzyme activities via methylumbelliferyl substrate analogs. The results show apparent temperature-driven seasonality in chlorophyll, cyanobacteria, and bacterioplankton parameters. Cyanobacteria became very abundant during summer months, peaking at 3 million cells per milliliter, and often dominated the chlorophyll signal. Spatially, biomass and activity measures usually peaked in the upper estuary near the mouth of the Escambia River. The uppermost site, located in the Escambia River, usually had the highest DOC concentrations, but the lowest chlorophyll and bacterioplankton parameters. Therefore bacterioplankton appeared limited by phytoplankton carbon rather than by detrital/riverine carbon. The may be explained by the drought-induced low flows that prevailed in the Escambia River during this study.

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Aquatic Sciences Meeting, Albuquerque 2001

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