Microbial biogeochemistry of B oiling S prings L ake: a physically dynamic, oligotrophic, low‐p H geothermal ecosystem

• Published in: Geobiology Vol. 11; no. 4; pp. 356 - 376
• Main Authors: Siering, P. L., Wolfe, G. V., Wilson, M. S., Yip, A. N., Carey, C. M., Wardman, C. D., Shapiro, R. S., Stedman, K. M., Kyle, J., Yuan, T., Van Nostrand, J. D., He, Z., Zhou, J.
• Format: Journal Article
• Language: English
• Published: 01-07-2013
• ISSN: 1472-4677; 1472-4669
• DOI: 10.1111/gbi.12041

B
oiling
S
prings
L
ake (
BSL
) in
L
assen
V
olcanic
N
ational
P
ark,
C
alifornia, is
N
orth
A
merica's largest hot spring, but little is known about the physical, chemical, and biological features of the system. Using a remotely operated vessel, we characterized the bathymetry and near‐surface temperatures at sub‐meter resolution. The majority of the 1.2 ha, p
H
2.2 lake is 10 m deep and 50–52 °C, but temperatures reach 93 °C locally. We extracted
DNA
from water and sediments collected from warm (52 °C) and hot (73–83 °C) sites separated by 180 m. Gene clone libraries and functional gene microarray (
G
eo
C
hip 3.0) were used to investigate the
BSL
community, and uptake of radiolabeled carbon sources was used to assess the relative importance of heterotrophic vs. autotrophic production. Microbial assemblages are similar in both sites despite the strong temperature differential, supporting observations of a dynamic, convectively mixed system.
B
acteria
in the
A
ctinobacteria
and
A
quificales
phyla are abundant in the water column, and
A
rchaea
distantly related to known taxa are abundant in sediments. The functional potential appears similar across a 5‐year time span, indicating a stable community with little inter‐annual variation, despite the documented seasonal temperature cycle.
BSL
water‐derived
DNA
contains genes for complete
C
,
N
, and
S
cycles, and low hybridization to probes for
N
and S oxidation suggests that reductive processes dominate. Many of the detected genes for these processes were from uncultivated bacteria, suggesting novel organisms are responsible for key ecosystem services. Selection imposed by low nutrients, low p
H
, and high temperature appear to result in low diversity and evenness of genes for key functions involved in
C
,
N
, and
S
cycling. Conversely, organic degradation genes appear to be functionally redundant, and the rapid assimilation of radiolabeled organic carbon into
BSL
cells suggests the importance of allochthonous
C
fueling heterotrophic production in the
BSL C
cycle.