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| Titel |
Synergistic effects of UVR and simulated stratification on commensalistic phytoplankton–bacteria relationship in two optically contrasting oligotrophic Mediterranean lakes |
| VerfasserIn |
P. Carrillo, J. M. Medina-Sánchez, C. Durán, G. Herrera, V. E. Villafañe, E. W. Helbling |
| 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. 3 ; Nr. 12, no. 3 (2015-02-04), S.697-712 |
| Datensatznummer |
250117798
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| Publikation (Nr.) |
 copernicus.org/bg-12-697-2015.pdf |
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| Zusammenfassung |
| An indirect effect of global warming is a reduction in the depth of the upper
mixed layer (UML) causing organisms to be exposed to higher levels of
ultraviolet (UVR, 280–400 nm) and photosynthetically active radiation (PAR,
400–700 nm). This can affect primary and bacterial production as well as
the commensalistic phytoplankton–bacteria relationship. The combined effects
of UVR and reduction in the depth of the UML were assessed on variables
related to the metabolism of phytoplankton and bacteria, during in situ
experiments performed with natural pico- and nanoplankton communities from
two oligotrophic lakes with contrasting UVR transparency (high-UVR versus
low-UVR waters) of southern Spain. The negative UVR effects on epilimnetic
primary production (PP) and on heterotrophic bacterial production (HBP),
intensified under increased stratification, were higher in the low-UVR than
in the high-UVR lake, and stronger on the phytoplanktonic than on the
heterotrophic bacterial communities. Under UVR and increased stratification,
the commensalistic phytoplankton–bacteria relationship was strengthened in
the high-UVR lake where excretion of organic carbon (EOC) rates exceeded the
bacterial carbon demand (BCD; i.e., BCD : EOC(%) ratio < 100). This did
not occur in the low-UVR lake (i.e., BCD : EOC(%) ratio > 100). The
greater UVR damage to phytoplankton and bacteria and the weakening of their
commensalistic interaction found in the low-UVR lake indicates that these
ecosystems would be especially vulnerable to UVR and increased
stratification as stressors related to global climate change. Thus, our
findings may have important implications for the carbon cycle in oligotrophic
lakes of the Mediterranean region. |
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