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AME 34:79-92 (2004)
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Abstract
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Role of nutrient supply and loss in controlling protist species dominance and microbial food-webs during spring blooms
C. Lovejoy1,3,*, N. M. Price2, L. Legendre1,4
1GIROQ, Département de Biologie, Université Laval, Sainte-Foy, Québec G1K 7P4, Canada
2Biology Department, McGill University, 1205 Avenue Docteur Penfield, Montreal, Québec H3A 1B1, Canada
3Present address: Institut de Ciències del Mar, CMIMA, CSIC, Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain
4Present address: Laboratoire d'Océanographie de Villefranche, BP 28, 06234 Villefranche-sur-Mer, Cedex, France
*Email: clovejoy@icm.csic.es
ABSTRACT: The species composition of spring blooms varies over open marine regions, displaying both spatial and inter-annual differences. We used semi-continuous cultures to promote species-specific blooms and investigate associated microbial food-web
dynamics and inorganic nutrient utilization. Beginning with high nutrient, low biomass water from 13 m depth, we compared the changes that took place over 9 d in 2 treatments: (1) NEW, a 'new-nutrient' treatment that simulated horizontal or vertical
advection; every 2 d, both particles and dissolved organic matter were removed and ca. 25% of the volume of the container was replaced with nutrient-rich seawater from 200 m depth. (2) REC, a recycling treatment simulating grazing and sinking losses
without nutrient replacement, i.e. conditions mimicking sharply stratified water columns; in this treatment the same volume of water was removed, but was then returned to the container following filtration through a 2.0 µm filter. In the NEW treatment,
diatoms consumed the added nutrients and dominated the production and biomass of the protist community. Total protist community production in the REC treatment was significantly lower than in the NEW treatment, with either a late or no diatom bloom and
prymnesiophytes such as Phaeocystis spp. attaining higher proportional biomass. Total production rates for heterotrophic protists, bacteria and viruses did not differ significantly between treatments. Nutrient consumption by the ensuing communities
differed between the 2 treatments, with a significantly greater proportion of total inorganic nutrients consumed in the NEW than in the REC treatment. The results demonstrate that the character of nutrient supply and loss influences protist community
structure and subsequent bulk nutrient utilization.
KEY WORDS: Nutrient supply · Protist species · Spring-bloom initiation · Succession · Phytoplankton · Marine · Arctic
Full text in pdf format
Published in AME Vol.
34, No. 1
(2004) on January 16
Print ISSN: 0948-3055; Online ISSN: 1616-1564.
Copyright © Inter-Research, Oldendorf/Luhe, 2004
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