Aquatic Sciences Meeting, Albuquerque 2001

CS15 Harmful Algal Blooms

Date: Tuesday, February 13, 2001, Time: 10:30:00 AM

Location: Cochiti/Taos

Mulholland, M, R, SUNY Stony Brook, Stony Brook, USA, mmulholland@notes.cc.sunysb.edu

Gobler, C, , Southampton College, Long Island University, Southampton, USA, cgobler@southampton.liu.edu

Lee, C, , SUNY Stony Brook, Stony Brook, USA, cindylee@notes.cc.sunysb.edu

AMINO ACID OXIDATION AND PEPTIDE HYDROLYSIS IN POPULATIONS SEASONALLY DOMINATED BY AUREOCOCCUS ANOPHAGEFFERENS

Both organic and inorganic nutrients influence growth of the Brown Tide chrysophyte, Aureococcus anophagefferens, and co-occurring phytoplankton. To estimate their relative importance, we measured inorganic and organic N uptake, and rates of peptide hydrolysis and amino acid oxidation (AAO) in size-fractionated samples during a seasonal study in Quantuck Bay, Long Island. Extracellular enzyme activity increased as Brown Tide populations developed and inorganic N sources were depleted, and decreased when Brown Tide populations collapsed in the summer. Much of the AAO was in the bacterial size fraction (< 1.2 um) while the bulk of the peptide hydrolysis was in the < 5.0 um size fraction when Brown Tide was present. As seasonal Brown Tide populations developed, N uptake rates increased, and the < 5.0 um size fraction accounted for most of this uptake. When dissolved inorganic N and organic compounds with different N contents were added to incubations of natural populations, rates of extracellular enzyme activity and N and C uptake were differentially affected among size-fractions, probably because of relative differences in the growth stimulation among bacteria, picoplankton, and larger phytoplankton.

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Aquatic Sciences Meeting, Albuquerque 2001

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