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| Titel |
Bottom up effects on bacterioplankton growth and composition during summer-autumn transition in the open NW Mediterranean Sea |
| VerfasserIn |
F. Wambeke, J.-F. Ghiglione, J. Nedoma, G. Mével, P. Raimbault |
| 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 ; 6, no. 4 ; Nr. 6, no. 4 (2009-04-28), S.705-720 |
| Datensatznummer |
250003648
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| Publikation (Nr.) |
 copernicus.org/bg-6-705-2009.pdf |
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| Zusammenfassung |
| We examined the vertical and temporal dynamics of nutrients, ectoenzymatic
activities under late summer-fall transition period (September–October 2004) in NW
Mediterranean Sea in relation to temporal change in factors limiting
bacterial production. The depth of the mixed layer (12.8±5.3 m) was
extremely stable until the onset of the destratification period after
11 October, creating a zone where diffusion of nutrient from the much deeper
phosphacline (69±12 m) and nitracline (50±8 m) was probably
strongly limited. However after 1st October, a shallowing of nutriclines
occured, particularly marked for nitracline. Hence, the nitrate to phosphate
ratio within the mixed layer, although submitted to a high short term
variability, shifted the last week of the cruise from 1.1±1.2 to 4.6±3.8,
and nitrate increased by a factor 2 (0.092±0.049 μM). A corresponding switch from more than one limitation (PN) to P-only
limitation of bacterial production was observed during the month as detected
by enrichment bioassays. Differences in the identity of the limiting
nutrient in surface (5 m: N and P at the beginning, strictly P at the end of
the study) versus 80 m (labile carbon) influence greatly bacterial community
structure shift between these two layers. The two communities (5 and 80 m)
reacted rapidly (24 h) to changes in nutrient concentrations by drastic
modification of total and active population assemblages resulting in changes
in activity. For bacterial production values less than 10 ng C l−1 h−1
(associated to deeper layers), aminopeptidase and lipase
exhibited higher activity relative to production whereas phosphatase varied
in the same proportions than BP on the range of activities tested. Our
results illustrate the effect of bottom-up control on bacterial community
structure and activities in the epipelagic NW Mediterranean Sea. |
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