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| Titel |
Biogeochemical controls on the bacterial populations in the eastern Atlantic Ocean |
| VerfasserIn |
S. B. Neogi, B. P. Koch, P. Schmitt-Kopplin, C. Pohl, G. Kattner, S. Yamasaki, R. J. Lara |
| 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 ; 8, no. 12 ; Nr. 8, no. 12 (2011-12-20), S.3747-3759 |
| Datensatznummer |
250006254
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| Publikation (Nr.) |
 copernicus.org/bg-8-3747-2011.pdf |
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| Zusammenfassung |
| Little is known about bacterial dynamics in the oligotrophic ocean,
particularly about cultivable bacteria. We examined the abundance of total
and cultivable bacteria in relation to changes in biogeochemical conditions
in the eastern Atlantic Ocean with special regard to Vibrio spp., a group of
bacteria that can cause diseases in human and aquatic organisms. Surface,
deep water and plankton (<20 μm, 20–55 μm and >55 μm)
samples were collected between 50° N and 24° S. Chlorophyll-a was very
low (<0.3 μg l−1) in most areas of the nutrient-poor Atlantic,
except at a few locations near upwelling regions. In surface water,
dissolved organic carbon (DOC) and nitrogen (DON) concentrations were 64–95 μM C and 2–10 μM N
accounting for ≥90 % and ≥76 % of total organic C and N, respectively. DOC and DON gradually decreased to
~45 μM C and <5 μM N in the bottom water. In the surface
layer, culture independent total bacteria and other prokaryotes represented
by 4´-6-diamidino-2-phenylindole (DAPI) counts, ranged mostly between 107 and 108 cells l−1, while cultivable bacterial counts (CBC) and
Vibrio spp. were found at concentrations of 104–107 and
102–105 colony forming units (CFU) l−1, respectively. Most
bacteria (>99 %) were found in the nanoplankton fraction (<20 μm), however, bacterial abundance did not correlate with suspended
particulates (chlorophyll-a, particulate organic C [POC] and N [PON]).
Instead, we found a highly significant correlation between bacterial
abundance and temperature (p < 0.001) and a significant correlation with
DOC and DON (p < 0.005 and <0.01, respectively). In comparison to CBC
and DAPI-stained prokaryotes, cultivable Vibrio showed a stronger and highly
significant correlation with DOC and DON (p < 0.0005 and p < 0.005,
respectively). In cold waters of the mesopelagic and abyssal zones, CBC was
50 to 100-times lower than in the surface layer; however, cultivable
Vibrio spp. could be isolated from the bathypelagic zone and even near the
seafloor (average ~10 CFU l−1). The depth-wise decrease in CBC
and Vibrio coincided with the decrease in both DOC and POC. Our study indicates
that Vibrio and other bacteria may largely depend on dissolved organic matter to
survive in nutrient-poor oceanic habitats. |
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