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| Titel |
Examination of the role of the microbial loop in regulating lake nutrient stoichiometry and phytoplankton dynamics |
| VerfasserIn |
Y. Li, G. Gal, V. Makler-Pick, A. M. Waite, L. C. Bruce, M. R. Hipsey |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 11 ; Nr. 11, no. 11 (2014-06-05), S.2939-2960 |
| Datensatznummer |
250117446
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| Publikation (Nr.) |
 copernicus.org/bg-11-2939-2014.pdf |
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| Zusammenfassung |
| The recycling of organic material through bacteria and microzooplankton to
higher trophic levels, known as the "microbial loop", is an important
process in aquatic ecosystems. Here the significance of the microbial loop in
influencing nutrient supply to phytoplankton has been investigated in Lake Kinneret
(Israel) using a coupled hydrodynamic–ecosystem model. The model was designed
to simulate the dynamic cycling of carbon, nitrogen and phosphorus through
bacteria, phytoplankton and zooplankton functional groups, with each pool
having unique C : N : P dynamics. Three microbial loop sub-model
configurations were used to isolate mechanisms by which the microbial loop
could influence phytoplankton biomass, considering (i) the role of bacterial
mineralisation, (ii) the effect of micrograzer excretion, and (iii) bacterial
ability to compete for dissolved inorganic nutrients. The nutrient flux
pathways between the abiotic pools and biotic groups and the patterns of
biomass and nutrient limitation of the different phytoplankton groups were
quantified for the different model configurations. Considerable variation in
phytoplankton biomass and dissolved organic matter demonstrated the
sensitivity of predictions to assumptions about microbial loop operation and
the specific mechanisms by which phytoplankton growth was affected.
Comparison of the simulations identified that the microbial loop most
significantly altered phytoplankton growth by periodically amplifying
internal phosphorus limitation due to bacterial competition for phosphate to
satisfy their own stoichiometric requirements. Importantly, each
configuration led to a unique prediction of the overall community
composition, and we conclude that the microbial loop plays an important role
in nutrient recycling by regulating not only the quantity, but also the
stoichiometry of available N and P that is available to primary producers.
The results demonstrate how commonly employed simplifying assumptions about
model structure can lead to large uncertainty in phytoplankton community
predictions and highlight the need for aquatic ecosystem models to carefully
resolve the variable stoichiometry dynamics of microbial interactions. |
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