download this poster (ppt file)
TRANSCRIPT
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:
www.SanSalMO.net
Tim SteppeHans PaerlLou Anne CheshireMelissa Leonard
Alan Decho
Jay Pinckney
Participants Collaborators
Virginia Tech
University of NC-Wilmington
University of Miami
[email protected][email protected]
UNC-CH Institute ofMarine Sciences
USC-Columbia Dept. of Environmental HealthSciencesTexas A&M Dept. of Oceanography
Anhydrophilic, Halotolerant Microbial Mats of San Salvador, Bahamas
05
101520253035
0
30
60
90
120
150
180
0
50
100
150
200
250
300
0
10
20
30
40
50
60
Salt PondSeawater
n.d.
n.d.b.d.b.d.
Tem
pera
ture
(o C)
Salin
ity
(psu
)N
H 4+
(N)
(mg
L-1 )
NO x
- (N
)(
g L-1
)
Mar.1999
Mar.2001
Mar.2000
Oct.2001
b.d.
b.d.
Mar.2002
Oct.2002
Date
Mar.2003
Salt Pond salinity exhibits both inter- and intra-annual variation. Salinity and temperature measurements contributed by Elyse Voegeli.
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 water-cover occurs most often.
L1(U)
L2(M)
L3(L)
Surface of MatX-Section of Mat X-Section of Mat
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.
Con NH4 NO3 P04 NH4/P04 NO3/P040
0.5
1
1.5
2
2.5
3 Sea WaterSalt Pond
Con NH4 NO3 P04 NH4/P04 NO3/P040123456789
Treatment
H14C
0 3- U
ptak
e (n
mol
C c
m-2
h-1 )
Nitr
ogen
ase
Act
ivity
(nm
ol C
2H4
cm-2
h-1
)
0
500
1000
1500
2000
2500
3000
3500
4000
0 200 400 600 800 1000 1200 1400
DarkLight
Dep
th in
Sed
imen
t (µm
)
O2 Concentration (µM)
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.
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.
0.1 subs/site
T10717T10011
T10012T10010
T10710T10008
T10016
T12313T12304
Desulfosarcina variablisT10017
T12319T12302
T12310T12317
T10006
T12309T10707
T12315T12316
T10715
Desulfovibrio longusDesulfovibrio africanus
T10014T10019
Desulfomonas pigraT10716T12305
T12306T10709
T10013
T12312T12303
Desulfotomaculumacetoxidans
T10713T10719
T10001T12318
Desulfoarculus baarsiiT10005
T10020T10002
T10003Desulfobulbus rhabdoformis
T10702T12314
T12301T10701
Archaeoglobus fulgidis
86100
100
94
70
67
8868
100
100
51100
59
61100
100
96100
100
73
93100
59
86
0.1 subs/site
T10717T10011
T10012T10010
T10710T10008
T10016
T12313T12304
Desulfosarcina variablisT10017
T12319T12302
T12310T12317
T10006
T12309T10707
T12315T12316
T10715
Desulfovibrio longusDesulfovibrio africanus
T10014T10019
Desulfomonas pigraT10716T12305
T12306T10709
T10013
T12312T12303
Desulfotomaculumacetoxidans
T10713T10719
T10001T12318
Desulfoarculus baarsiiT10005
T10020T10002
T10003Desulfobulbus rhabdoformis
T10702T12314
T12301T10701
Archaeoglobus fulgidis
86100
100
94
70
67
8868
100
100
51100
59
61100
100
96100
100
73
93100
59
86
T38L22T30U11
T30U10Phormidium sp.
T12307Pseudoanabaena sp.
NC mat cyanoT30U9
T30U02T323U03
T12306T38M06
Lyngbya lagerhaemiiDermocarpa sp.
Plectonema sp.T323L03T12304
Myxosarcina sp.Xenococcus sp.
Cyanothece sp.Aphanazomenon sp.
Anabaerna oscillaroidesNostoc commune
Lyngbya sp. SG1Synechococcus sp.
Synechocystis sp.Gloeothece sp.
Trichodesmium sp.Trichodemium thiebautii
T38L05T38M14
T10719T38U19
T323U09T38U23
T10711T10722
T38M12
Azotobacter chromatiumVibrio diazotrophicus
Azospirillum brasilenseRhodobacter rubrum
T10020T38M15
T10023NC Mat 0729 D10NC Mat 0729 D12
Desulfomicrobium baculatusDesulfovibrio vulgaris
Desulfovibrio salexigensT38M01
T10712
T323M18T323L05
T10002T10014
T10715T323L03
T10713Desulfovibrio gigas
T38U01NC Mat 0729 D11
T30U15T38U12
T323L12NC Mat 0909 D09
T323L07T323L21
NC Mat 0729 D09T38L08
T323L14T30L02
T323U23T323LU21T323L09
T38L18Clostridium pasteurianum
T30L13T30L06
T30M16T30L20
T10718Desulfobacter curvatus
Desulfonema limicolaDesulfosporosinus orientis
Clostridium cellobioparum Meth.voltae
0.1 subs/site
97
9964
100
90
99
52100
71
7278
64
100
86
8351
5192
60
67
89
68
10072
79
100
80
100
10062
100
10055
cyanobacteria
heterocystous
bet a/ga mm
aalpha
anaerobesdelta SR
B, gram
+s, etc
T38L22T30U11
T30U10Phormidium sp.
T12307Pseudoanabaena sp.
NC mat cyanoT30U9
T30U02T323U03
T12306T38M06
Lyngbya lagerhaemiiDermocarpa sp.
Plectonema sp.T323L03T12304
Myxosarcina sp.Xenococcus sp.
Cyanothece sp.Aphanazomenon sp.
Anabaerna oscillaroidesNostoc commune
Lyngbya sp. SG1Synechococcus sp.
Synechocystis sp.Gloeothece sp.
Trichodesmium sp.Trichodemium thiebautii
T38L05T38M14
T10719T38U19
T323U09T38U23
T10711T10722
T38M12
Azotobacter chromatiumVibrio diazotrophicus
Azospirillum brasilenseRhodobacter rubrum
T10020T38M15
T10023NC Mat 0729 D10NC Mat 0729 D12
Desulfomicrobium baculatusDesulfovibrio vulgaris
Desulfovibrio salexigensT38M01
T10712
T323M18T323L05
T10002T10014
T10715T323L03
T10713Desulfovibrio gigas
T38U01NC Mat 0729 D11
T30U15T38U12
T323L12NC Mat 0909 D09
T323L07T323L21
NC Mat 0729 D09T38L08
T323L14T30L02
T323U23T323LU21T323L09
T38L18Clostridium pasteurianum
T30L13T30L06
T30M16T30L20
T10718Desulfobacter curvatus
Desulfonema limicolaDesulfosporosinus orientis
Clostridium cellobioparum Meth.voltae
0.1 subs/site
97
9964
100
90
99
52100
71
7278
64
100
86
8351
5192
60
67
89
68
10072
79
100
80
100
10062
100
10055
cyanobacteria
heterocystous
bet a/ga mm
aalpha
anaerobesdelta SR
B, gram
+s, etc
T38M14T30L16
T30U10T30L23T30U04
T323U09T38M21
T38M13T38U23T38U08
T38M10T323M16T30M14T38M17
T38M07T38L07
T30M12T30U18
T323U01T38U13
T30M18T30U15T38L09
T30L13T30L06
Oscillatoria sp. OH25T30M24
T323M01T30M06
T323U21T30M11
T30M07T38M15
T38U18T30M19
Nodularia sp. PCC9350Anabaena flos-aquae
Anabaenopsis sp. PCC9215Symploca semiplena
Trichdesmium thiebautiiLyngbya aestuarii
Halospirulina sp. BAJA95T30U16
Halothece sp.
Halomicronema sp. TFEP2
Leptolyngbya sp. PCC9221T38L14
T38U21Cyanothece sp. PCC7418
Aphanothece sp. ATCC43922T38L03
T38U01T323U22
Lyngbya sp. PCC7419T323L01
T30M05T38U12
T38L01T323U19
T30L03
T323U15T38UL11
T38U22T323L04
T323L02T38L04
Leptolyngbya sp. PCC7104CY38L08
Escherichia coli0.1 subs/site
100
100
88
62
86
85
5370
52
9683
6077
T38M14T30L16
T30U10T30L23T30U04
T323U09T38M21
T38M13T38U23T38U08
T38M10T323M16T30M14T38M17
T38M07T38L07
T30M12T30U18
T323U01T38U13
T30M18T30U15T38L09
T30L13T30L06
Oscillatoria sp. OH25T30M24
T323M01T30M06
T323U21T30M11
T30M07T38M15
T38U18T30M19
Nodularia sp. PCC9350Anabaena flos-aquae
Anabaenopsis sp. PCC9215Symploca semiplena
Trichdesmium thiebautiiLyngbya aestuarii
Halospirulina sp. BAJA95T30U16
Halothece sp.
Halomicronema sp. TFEP2
Leptolyngbya sp. PCC9221T38L14
T38U21Cyanothece sp. PCC7418
Aphanothece sp. ATCC43922T38L03
T38U01T323U22
Lyngbya sp. PCC7419T323L01
T30M05T38U12
T38L01T323U19
T30L03
T323U15T38UL11
T38U22T323L04
T323L02T38L04
Leptolyngbya sp. PCC7104CY38L08
Escherichia coli0.1 subs/site
100
100
88
62
86
85
5370
52
9683
6077
Sites and Design Photosynthesis and Nitrogenase Activity Mat & Water Chemistry (Salt Pond)
EPS Characterization
Diversity of Key Biogeochemical Functional Groups
23m 11m 7m 3m 0m
Site
dsrAsulfate-reducers
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.
NifH
3-D Reconstruction of TowerPolymer Towers
EPS
NifHdiazotrophs
Cyanobacterial 16Sprimary producers
T323U08
transect
meter markupper, middle, or lower portion of mat
clone number
10-Mar-03 19-Apr-03 29-May-03 8-Jul-030
50100150200250300350
051015202530354045
Date
Temperature
Salin
ity (P
SU)
10 20 300 10 20 30
4
9
14
19
24
10 20 30
Carbon:Nitrogen Ratio
Tran
sect
Pos
ition
Mar. 2002 Mar. 2003Oct. 2002
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 organisms4) Develop a conceptual model linking climate and water budget data, water availability, and
primary production.