Transcript this Poster (ppt file)

Anhydrophilic, Halotolerant Microbial Mats of
San Salvador, Bahamas
500
[email protected] Texas A&M Dept.
of Oceanography
1000
Abstract
Objectives
The overall research objective of this study is to assess the influence water availability has on
structural diversification, community composition, production, and carbon sequestration in
microbial mats. The specific goals for this observatory are to:
1
NH4
P04
120
90
8
60
7
30
6
0
5
300
4
250
2
1
NH4
4000
NO3
P04
NH4/P04 NO3/P04
EPS Characterization
3-D Reconstruction of Tower
L1(U)
0.5
50
40
30
20
b.d.
n.d.
b.d.
b.d.
10
0
Mar.
1999
Mar.
2000
Mar.
2001
Oct.
2001
Mar.
2002
Oct.
2002
S4
3m
S5
0m
Date
350
45
40
35
30
25
20
15
10
5
0
300
250
200
150
100
50
0
19-Apr-03 29-May-03
4
Oct. 2002
Mar. 2002
Mar. 2003
9
14
19
8-Jul-03
24
Salt Pond salinity exhibits both inter- and
intra-annual variation. Salinity and
temperature measurements contributed by
Elyse Voegeli.
X-Section of Mat
S3
7m
SITE
Site
Mar.
2003
Date
L3(L)
S2
11m
Abundances of Extracellular Polymeric
Secretions (EPS) in three different layers of
the Salt Pond Microbial Mat: (1) An
“orange” surface “ layer (L1); a “green”
cyanobacterial layer (L2); and a “purple”
Chromatium sp. Layer (L3). Significantly
higher abundances of EPS occur in the
surface L1 layer, and at sites where watercover occurs most often.
n.d.
L2(M)
Surface of Mat
1.0
b.d.
10-Mar-03
X-Section of Mat
1.5
S1
23m
0
60
Combined results of short-term nutrient bioassays
from March 2002 and 2003. Mat pieces were
collected and incubted in Salt Pond water or
seawater ammended with nutrients (NH4+ 20 μM;
NO3- 20 μM; and/or PO42- 5 μM). We observed no
significant stimulation of photosynthesis or
nitrogenase activity (N2 Fixation) due to nutrient
additions. Both forms of nitrogen repressed
nitrogenase activity, while phosphorus appeared to
ameliorate any N repression. Salinity appeared to
affect 14CO2 upatke more than it did NA. These
observations suggest water availability and
salinity, in particular, have the largest impact on
production and cycling in the mats.
2.0
Salt Pond
Seawater
100
Treatment
Light and dark profiles of dissolved oxygen concentration
in hypersaline microbial mats. Oxygen gradients change
from anoxic under dark conditions to ca. 10 times O2
saturation under sunlight. EPS may provide a buffering
mechanism to prevent oxidative damage to photosynthetic
enzymes.
2.5
0.0
150
50
Con
Surface Layer (L1)
Layer 2 (L2)
Layer 3 (L3)
200
0
0
10
20
30
10
20
30
10
20
30
Carbon:Nitrogen Ratio
Diversity of Key Biogeochemical Functional Groups
The surface layer microbial communities of Salt Pond mats form crenulated “polymer towers” that extend
upward during water cover (see X-section). When examined using confocal scanning laser microscopy
(CSLM), these polymer towers contain dense arrays of cyanobacteria and heterotrophic bacteria enveloped
in a dense gel matrix of extracellular polymers (EPS). Dense colonies of cells suggest chemical signaling
may occur in these towers. Also, clusters of cells contained within amphiphilic (hydrophobic/hydrophilic)
EPS.
dsrA
sulfate-reducers
NifH
diazotrophs
NifH
86
59
T10717
T10011
T10012
T10010
T10710
T10008
T10016
T10006
T12313
Virginia Tech
100
100
86
T10702
T12314
T12301
T10701
Archaeoglobus fulgidis
0.1 subs/site
89
NC Mat 0729 D10
NC Mat 0729 D12
Desulfomicrobium baculatus
67
Desulfovibrio vulgaris
Desulfovibrio salexigens
68
T38M01
T10712
T323L05
100
T323M18
72
T10002
79
T10014
T10715
100
T323L03
T10713
Desulfovibrio gigas
80
T38U01
NC Mat 0729 D11
T30U15
T38U12
T323L12
NC Mat 0909 D09
T323L07
T323L21
NC Mat 0729 D09
55
100 T38L08
T323L14
T30L02
100 T323U23
T323LU21
T323L09
T38L18
Clostridium pasteurianum
100
T30L06
62
T30L13
T30M16
100 T30L20
T10718
60
Desulfobacter curvatus
Desulfonema limicola
Desulfosporosinus orientis
Clostridium cellobioparum
anaerobes
University of NCWilmington
86
meter mark
upper, middle, or
lower portion of mat
clone number
heterocystous
delta SRB, gram +s, etc
acetoxidans
Desulfoarculus baarsii
T10005
T10020
T10002
T10003
Desulfobulbus rhabdoformis
94
0.1 subs/site
transect
alpha
70
T12304
Desulfosarcina variablis
T10017
100 T12319
93
T12302
T12317
T12310
T12309
100
96
T10707
T12315
T12316
73
100 T10715
100
T12306
61
T10709
T10013
Desulfovibrio longus
100
59
Desulfovibrio africanus
T10014
T10019
Desulfomonas pigra
100 T10716
68
T12305
88
T12312
100 T12303
67
T10713
T10719
T10001
100
51
T12318
Desulfotomaculum
T38L22
T30U11
83
T30U10
51
Phormidium sp.
T12307
Pseudoanabaena sp.
NC mat cyano
T30U9
T30U02
T323U03
T12306
T38M06
Lyngbya lagerhaemii
Dermocarpa sp.
Plectonema sp.
T323L03
T12304
Myxosarcina sp.
64
Xenococcus sp.
Cyanothece sp.
Aphanazomenon sp.
78
Anabaerna oscillaroides
72
Nostoc commune
Lyngbya sp. SG1
51
Synechococcus sp.
92
Synechocystis sp.
Gloeothece sp.
100 Trichodesmium sp.
Trichodemium thiebautii
T38L05
T38M14
99
T10719
100
T38U19
T323U09
T38U23
90
T10711
99
64
T10722
Azotobacter chromatium
97
Vibrio diazotrophicus
T38M12
52
Rhodobacter rubrum
100
Azospirillum brasilense
71
T10020
T38M15
T10023
T323U08 Cyanobacterial 16S
primary producers
beta/gamma
EPS
Collaborators
University of
Miami
NH4/P04 NO3/P04
3
3500
Polymer Towers
NO3
150
NH4 + (N)
(mg L-1)
Depth in Sediment (µm)
3000
5
180
9
2500
10
0.5
Con
2000
3.0
15
0
1500
Dark
Light
20
cyanobacteria
Participants
1.5
0
1) Describe the structural and microbial diversity of the mat communities in relation to water
availability.
2) Assess the influence water availability has on primary production extracellular polymeric
substances (EPS) production, and EPS degradation.
3) Isolate and characterize desiccation tolerant organisms
4) Develop a conceptual model linking climate and water budget data, water availability, and
primary production.
www.SanSalMO.net
2
EPS Abundance Across Hydration Gradient
25
Temperature
Like many Bahamian Islands, San Salvador Island (24o05' N, 74o30' W) contains numerous
shallow, hypersaline (45 to 322 ‰) lakes. The lakes are subjected to intense irradiance (> 2100
μE m-2 s-1), high temperatures (> 35o C) and chronic nutrient depletion. Highly productive
microbial mats blanket the shallow sediments in many of the lakes. The overall research
objective of this study is to assess the influence water availability has on structural
diversification, community composition, production, and carbon sequestration in microbial
mats. Three transects, 26 meters in length, have been established along a natural desiccation
gradient in one of the hypersaline lakes, Salt Pond. Samples for community composition,
extracellular polymeric substances (EPS) content, C & N content, and microscopic
documentation are collected during each site visit (two to three times a year). Rates of key C, O,
and N cycling processes (photosynthesis and N2 fixation) are obtained. In cooperation with the
staff from the Gerace Research Center, Salt Pond’s salinity and temperature are being
measured every 10-21 days. From March to July, Salt Pond’s salinity increased from ~ 110‰ to
over 320‰. Light and dark vertical O2 distribution profiles of the mat’s upper 5 mm indicate
that, under dark conditions, anoxia reaches the mat surface. When exposed to light (1,500 µmol
m-2 s-1, 10 min), O2 was detected as deep as 5 mm with concentrations (ca. 800% O2 saturation)
peaking at 1 mm depth. Light and dark cycles create a dynamic chemical environment that
changes from anoxic to hyperoxic conditions within minutes. How EPS may buffer against
drastic changes in redox conditions is being examined. Nutrient addition bioassays (e.g., NH4+,
NO3-, and PO42-) indicate salinity levels and not nutrient availability has the greatest impact on
these crucial biogeochemical processes. Sequencing surveys of cyanobacterial 16S (primary
producers), dsr (sulfate reducers/carbon mineralizers), and nifH (diazotrophs) genes show that
diverse assemblages comprise the key functional groups of microorganisms. We are currently
analyzing the sequence distributions to determine if there are any differences along the
gradient. Carbohydrate analyses have led to the discovery of “amadori products" (APs) in the
Salt Pond mats. APs are unique protein-carbohydrate linkages that form when basic amino
acids cross-link with carbohydrate carboxyl groups. This is the first report of APs being found
in natural systems. The potential for amadori products to act as a further defense (e.g.,
scytonemins, mycosporine amino acids, etc) against UV is being investigated.
30
ug EPS per mg Cell Biomass
0
2.5
Temperature
(oC)
200 400 600 800 1000 1200 1400
Salinity
(psu)
0
35
NOx- (N)
(g L-1)
USC-Columbia Dept. of
Environmental Health
Sciences
Sea Water
Salt Pond
3
Transect Position
O2 Concentration (µM)
Salinity (PSU)
Jay Pinckney
[email protected]
Photosynthesis and Nitrogenase Activity Mat & Water Chemistry (Salt Pond)
Sites and Design
Nitrogenase Activity
(nmol C2H4 cm-2 h-1)
Alan Decho
UNC-CH Institute of
Marine Sciences
H14 C03- Uptake
(nmol C cm-2 h-1)
Tim Steppe
[email protected]
Hans Paerl
[email protected]
Lou Anne Cheshire
Melissa Leonard
70
100
83
52
Meth.
voltae
0.1 subs/site
96
T38M14
T30L16
T30U10
T30L23
T30U04
T323U09
T38M21
T38M13
T38U23
T38U08
T38M10
T323M16
T30M14
T38M17
T38M07
T38L07
T30M12
60 T30U18
77
T323U01
T38U13
T30M18
T30U15
T38L09
T30L13
T30L06
Oscillatoria sp. OH25
T30M24
T323M01
T30M06
T323U21
T30M11
T30M07
T38M15
T38U18
T30M19
Nodularia sp. PCC9350
100
Anabaena flos-aquae
Anabaenopsis sp. PCC9215
Symploca semiplena
Trichdesmium thiebautii
Lyngbya aestuarii
Halospirulina sp. BAJA95
T30U16
Halothece sp.
Leptolyngbya sp. PCC9221
T38L14
88 T38U21
Cyanothece sp. PCC7418
Aphanothece sp. ATCC43922
62
T38L03
T323U22
86
T38U01
Lyngbya
sp. PCC7419
85
T323L01
T30M05
53
T38U12
T38L01
T323U19
T30L03
Halomicronema sp. TFEP2
T323U15
T38UL11
T38U22
T323L04
T323L02
T38L04
Leptolyngbya sp. PCC7104
CY38L08
Escherichia coli