Publication Date:
2018-10-29
Description:
Eastern boundary upwelling systems (EBUSs) are among the most productive marine
environments in the world. The Canary Current upwelling system off the coast of
Mauritania and Morocco is the second most productive of the four EBUS, where
nutrient-rich
waters fuel perennial phytoplankton blooms, evident by high chlorophyll
a concentrations off Cape Blanc, Mauritania. High primary production leads to
eutrophic waters in the surface layers, whereas sinking phytoplankton debris and
horizontally dispersed particles form nepheloid layers (NLs) and hypoxic waters at
depth. We used Catalyzed Reporter Deposition Fluorescence In Situ Hybridization
(CARD-FISH)
in combination with fatty acid (measured as methyl ester; FAME) profiles
to investigate the bacterial and archaeal community composition along transects
from neritic to pelagic waters within the “giant Cape Blanc filament” in two
consecutive years (2010 and 2011), and to evaluate the usage of FAME data for microbial
community studies. We also report the first fatty acid profile of Pelagibacterales
strain HTCC7211 which was used as a reference profile for the SAR11 clade.
Unexpectedly, the reference profile contained low concentrations of long chain fatty
acids 18:1 cis11, 18:1 cis11 11methyl, and 19:0 cyclo11–12 fatty acids, the main compounds
in other Alphaproteobacteria. Members of the free-living
SAR11 clade were
found at increased relative abundance in the hypoxic waters in both years. In contrast,
the depth profiles of Gammaproteobacteria (including Alteromonas and
Pseudoalteromonas), Bacteroidetes, Roseobacter, and Synechococcus showed high
abundances of these groups in layers where particle abundance was high, suggesting
that particle attachment or association is an important mechanisms of dispersal for
these groups. Collectively, our results highlight the influence of NLs, horizontal particle
transport, and low oxygen on the structure and dispersal of microbial communities
in upwelling systems.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
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isiRev