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| Titel |
Effects of varied nitrate and phosphate supply on polysaccharidic and proteinaceous gel particle production during tropical phytoplankton bloom experiments |
| VerfasserIn |
A. Engel, C. Borchard, A. Loginova, J. Meyer, H. Hauss, R. Kiko |
| 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 ; 12, no. 19 ; Nr. 12, no. 19 (2015-10-07), S.5647-5665 |
| Datensatznummer |
250118112
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| Publikation (Nr.) |
 copernicus.org/bg-12-5647-2015.pdf |
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| Zusammenfassung |
| Gel particles such as the polysaccharidic transparent exopolymer particles
(TEP) and the proteinaceous Coomassie stainable particles (CSP) play an
important role in marine biogeochemical and ecological processes like
particle aggregation and export, or microbial nutrition and growth. So far,
effects of nutrient availability or of changes in nutrient ratios on gel
particle production and fate are not well understood. The tropical ocean
includes large oxygen minimum zones, where nitrogen losses due to anaerobic
microbial activity result in a lower supply of nitrate relative to phosphate
to the euphotic zone. Here, we report of two series of mesocosm experiments
that were conducted with natural plankton communities collected from the
eastern tropical North Atlantic (ETNA) close to Cape Verde in October 2012.
The experiments were performed to investigate how different phosphate
(experiment 1, Varied P: 0.15–1.58 μmol L−1) or nitrate (experiment 2,
Varied N: 1.9–21.9 μmol L−1) concentrations affect the abundance and
size distribution of TEP and CSP. In the days until the bloom peak was
reached, a positive correlation between gel particle abundance and Chl a
concentration was determined, linking the release of dissolved gel
precursors and the subsequent formation of gel particles to autotrophic
production. After the bloom peak, gel particle abundance remained stable or
even increased, implying a continued partitioning of dissolved into
particulate organic matter after biomass production itself ceased. During
both experiments, differences between TEP and CSP dynamics were observed;
TEP were generally more abundant than CSP. Changes in size distribution
indicated aggregation of TEP after the bloom, while newly formed CSP
decomposed. Abundance of gel particles clearly increased with nitrate
concentration during the second experiment, suggesting that changes in
[DIN] : [DIP] ratios can affect gel particle formation with potential
consequences for carbon and nitrogen cycling as well as food web dynamics in
tropical ecosystems. |
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