title: Time-courses of size-fractionated phosphate uptake: are larger cells better competitors for pulses of phosphate than smaller cells?
abstract: Time-course experiments of phosphate uptake by size-fractionated phytoplankton were conducted in oligotrophic Kennedy and Sproat Lakes. The objective was to determine if large phytoplankton obtained more phosphate than smaller cells, when the nutrient was present at higher concentrations. Studies at Kennedy Lake revealed that uptake rates in the 0.2-3.0 μm fraction were very sensitive to the time they were exposed to elevated concentrations; rates determined over the 60-120 min interval were less than 30% of those recorded over the 0-60 min interval. In contrast, there was little difference in uptake rates over these intervals for cells>3.0 μm. At Sproat Lake phosphate incorporation into the two size fractions was followed after the aerial fertilization of the lake with inorganic nutrients. Following nutrient addition the proportion of phosphate entering the>3.0 μm size fraction increased from ca. 35% to ca. 85%. Despite these observations, it is doubtful that larger cells are able to sequester enough phosphate from pulses to realize the same specific growth rates as their smaller counterparts.
authors.affiliation: Department of Botany and Oceanography, University of British Columbia, 6270 University Boulevard, V6T 1W5, Vancouver, British Columbia, Canada.
authors.forename: C A
authors.initials: CA
authors.lastname: Suttle
authors.affiliation: Department of Fisheries and Oceans, West Vancouver Laboratory, 4160 Marine Drive, V7V 1N6, West Vancouver, British Columbia, Canada.
authors.forename: J G
authors.initials: JG
authors.lastname: Stockner
authors.affiliation: Department of Fisheries and Oceans, West Vancouver Laboratory, 4160 Marine Drive, V7V 1N6, West Vancouver, British Columbia, Canada.
authors.forename: K S
authors.initials: KS
authors.lastname: Shortreed
authors.affiliation: Department of Botany and Oceanography, University of British Columbia, 6270 University Boulevard, V6T 1W5, Vancouver, British Columbia, Canada.
authors.forename: P J
authors.initials: PJ
authors.lastname: Harrison
keywords: Lake fertilization; Nutrient patches; Nutrient pulses; Phosphate uptake; Size-fractionated phosphate uptake