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Aquatic Microbial Ecology

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AME 75:139-153 (2015)  -  DOI:

High- and low-affinity phosphate uptake and its effect on phytoplankton dominance in a phosphate-depauperate lake

Matthew J. Prentice1,*, Kate R. O’Brien2, David P. Hamilton3, Michele A. Burford1

1Australian Rivers Institute, Griffith University, Nathan, Queensland 4111, Australia
2School of Chemical Engineering, The University of Queensland, St Lucia, Queensland 4072, Australia
3Centre for Biodiversity and Ecology Research, The University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand
*Corresponding author:

ABSTRACT: Phosphorus (P) is an essential element for phytoplankton growth, and in recent years our understanding of P use based on kinetics has been overturned with new knowledge of the complexity of P utilization. However, much of this knowledge is based on culture studies with individual species. Our objective was to measure the effect of dissolved inorganic P (DIP) concentrations on DIP uptake rates by phytoplankton, in the context of seasonal phytoplankton succession in a large monomictic, DIP-depauperate lake. We demonstrated an inverse relationship between surface DIP concentration and DIP uptake rate, with substantially higher uptake rates occurring under thermally stratified, DIP-depauperate conditions. The combination of surface water DIP concentration and water temperature explained 50.3% of the variation in uptake rates. DIP concentration explained the majority of variation, with a concentration of 4.75 µg DIP l-1 appearing to be a transition between low- and high-affinity uptake. Variability below 4.75 µg DIP l-1 was further explained by water temperature. High-affinity DIP uptake was most common when Cyanobacteria dominated the phytoplankton assemblage. We validated our field results by conducting a DIP starvation study on an isolate of a dominant cyanobacterium, Cylindrospermopsis raciborskii. High-affinity uptake was demonstrated as the culture became progressively starved of P. Our findings indicate that rapid DIP scavenging via high-affinity uptake is advantageous under DIP-depauperate conditions during the summer-stratification period. It may also contribute to the switch from diatom/cryptophyte/chlorophyte dominance to cyanobacterial dominance in summer. This study also has implications for phytoplankton–nutrient models, which typically do not incorporate high-affinity P uptake.

KEY WORDS: Phosphorus limitation · Phosphorus dynamics · Phosphorus cycling · Cyanobacteria · Cylindrospermopsis raciborskii · Phytoplankton blooms · Seasonal succession

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Cite this article as: Prentice MJ, O’Brien KR, Hamilton DP, Burford MA (2015) High- and low-affinity phosphate uptake and its effect on phytoplankton dominance in a phosphate-depauperate lake. Aquat Microb Ecol 75:139-153.

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