Interactions among epilimnetic phosphorus, phytoplankton biomass and bacterioplankton metabolism in lakes of varying submerged macrophyte cover

The effect of submerged macrophytes on interactions among epilimnetic phosphorus, phytoplankton, and heterotrophic bacterioplankton has been acknowledged, but remains poorly understood. Here, we test the hypotheses that the mean summer phytoplankton biomass (chlorophyll a): phosphorus ratios decreas...

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Bibliographic Details
Published in:Hydrobiologia 2003-07, Vol.501 (1-3), p.75-81
Main Authors: ROONEY, Neil, KALFF, Jacob
Format: Article
Language:English
Subjects:
Animal and plant ecology
Animal, plant and microbial ecology
Aquatic plants
Biological and medical sciences
Biomass
Fresh water ecosystems
Freshwater
Fundamental and applied biological sciences. Psychology
Plankton
Production increases
Synecology
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Summary:The effect of submerged macrophytes on interactions among epilimnetic phosphorus, phytoplankton, and heterotrophic bacterioplankton has been acknowledged, but remains poorly understood. Here, we test the hypotheses that the mean summer phytoplankton biomass (chlorophyll a): phosphorus ratios decrease with increased macrophyte cover in a series of nine lakes. Further, we test that both planktonic respiration and bacterioplankton production increase with respect to phytoplankton biomass along the same gradient of increasing macrophyte cover. Increased macrophyte cover was associated with a lower fraction of particulate phosphorus in epilimnia, with total particulate phosphorus declining from over 80% of total phosphorus in a macrophyte free lake to less than 50% in a macrophyte rich lake. Phytoplankton biomass (chlorophyll a) too was lower in macrophyte dominated lakes, despite relatively high levels of total dissolved phosphorus. Planktonic respiration and bacterioplankton production were higher in macrophyte rich lakes than would be expected from phytoplankton biomass alone, pointing to a subsidy of bacterioplankton metabolism by macrophyte beds at the whole lake scale. The results suggest that the classical view of pelagic interactions, which proposes phosphorus determines phytoplankton abundance, which in turn determines bacterial abundance through the production of organic carbon, becomes less relevant as macrophyte cover increases.[PUBLICATION ABSTRACT]
ISSN:0018-8158
1573-5117
DOI:10.1023/A:1026255302443