Research Article Dynamics of the Methanogenic Archaea in Tropical Estuarine Sediments - Hindawi

14 Pages·2015·1.68 MB·English

HindawiPublishingCorporation
Archaea
Volume2013,ArticleID582646,13pages
http://dx.doi.org/10.1155/2013/582646
Research Article
Dynamics of the Methanogenic Archaea in
Tropical Estuarine Sediments
MaríadelRocíoTorres-Alvarado,1FranciscoJoséFernández,2
FlorinaRamírezVives,2andFranciscoVarona-Cordero1
1DepartmentofHydrobiology,UniversidadAutónomaMetropolitana-Iztapalapa,AvenidaSanRafaelAtlixcoNo.86,
ColoniaVicentina,09340MexicoCity,DF,Mexico
2DepartmentofBiotechnology,UniversidadAutónomaMetropolitana-Iztapalapa,AvenidaSanRafaelAtlixcoNo.86,
ColoniaVicentina,09340MexicoCity,DF,Mexico
CorrespondenceshouldbeaddressedtoMaríadelRocíoTorres-Alvarado;[email protected]
Received27July2012;Revised30October2012;Accepted3December2012
AcademicEditor:MartinKrüger
Copyright©2013MaríadelRocíoTorres-Alvaradoetal.isisanopenaccessarticledistributedundertheCreativeCommons
AttributionLicense,whichpermitsunrestricteduse,distribution,andreproductioninanymedium,providedtheoriginalworkis
properlycited.
Methanogenesis may represent a key process in the terminal phases of anaerobic organic matter mineralization in sediments
of coastal lagoons. e aim of the present work was to study the temporal and spatial dynamics of methanogenic archaea in
sedimentsoftropicalcoastallagoonsandtheirrelationshipwithenvironmentalchangesinordertodeterminehowthesein�uence
methanogeniccommunity.Sedimentsampleswerecollectedduringthedry(February,May,andearlyJune)andrainyseasons
(July,October,and�ovember).Microbiologicalanalysisincludedthe�uanti�cationofviablemethanogenicarchaea(MA)with
three substrates and the evaluation of kinetic activity from acetate in the presence and absence of sulfate. e environmental
variablesassessedweretemperature,pH,Eh,salinity,sulfate,solidscontent,organiccarbon,andcarbohydrates.MAabundance
wassigni�cantlyhigherintherainyseason(10 –10 cells/g)comparedwiththedryseason(10 –10 cells/g),withmethanolas
animportantsubstrate.Atspatiallevel,MAwere6det7ectedinthetwolayersanalyzed,andnoimp4ortan6tvariationswereobserved
eitherinMAabundanceoractivity.Salinity,sulfate,solids,organiccarbon,andEhweretheenvironmentalvariablesrelatedto
methanogeniccommunity.AconceptualmodelisproposedtoexplainthedynamicsoftheMA.
1.Introduction methanogenesis is outcompeted by anaerobic respiration,
mainly for thermodynamic reasons [5]. MA distribution
Coastal and marine environments, including estuaries and patterns and its number, as well as physical, chemical,
coastallagoons,arecharacterizedbylargeamountsoforganic andnutritionalparameterscontrollingtheirabundanceand
matter,whichismineralizedprimarilyinsedimentsthrough distribution have been studied in lacustrine sediments [6]
anaerobic processes, sulfate reduction being the dominant andincoastalenvironments[7,8].
metabolic pathway [1, 2]. However, although these ecosys- Most of the ecological studies assessing the structure of
tems are the typical habitat of sulfate-reducing prokaryotes methanogenic communities in estuarine systems have been
(SRP),methanogenicarchaea(MA)andmethaneproduction performedintemperatelatitudeswheretemperatureisoneof
havealsobeendetected[3,4]. themajorfactorsregulatingecosystemfunction.eseinves-
MA are strict anaerobes that produce methane as end- tigationshaveincludedanevaluationoftheMAintheinter-
product of their metabolism. ese organisms are com- tidalzoneofmarsheswiththepresenceofSpartina alterni-
mon in anoxic environments in which electron acceptors �ora,whoserootsprovideorganiccarbonandcontributeto
such as nitrate and sulfate are either absents or present at createaerobicmicrohabitats[9,10].MAabundancehasbeen
low concentrations and are usually dominant in freshwater �uanti�edwithtwoorthreesubstrates,ofwhichacetateand
environments. In the presence of these electron acceptors, hydrogenhavebeenreportedasthetwomostimportantones
2 Archaea
N
15◦32
15◦32
15◦23
0 1 2 4 5 6
96◦03 0 1 2(Km4) 5 6 15◦09 92◦55 (Km)
(a) CoastallagoonsystemofCarretas-Pereyra,Chiapas (b) CoastallagoonsystemofChantuto-Panzacola,Chiapas
F1:Studyareaandsamplingsites( ).
•
[4,11].Additionally,ithasbeenestablishedthatinestuaries, 2.MaterialsandMethods
where a salinity gradient exists from the marine zone to a
riverentrance,MAareprevalentupstreaminthefreshwater 2.1. Study Site. e Chantuto-Panzacola and Carretas-
regionanddecreasetowardsthebrackishandmarineends; Pereyra lagoon systems are located in the State of Chiapas,
sulfatereductionhasbeenidenti�edasthekeyfactorrelated Mexican Paci�c coast (Figure 1); they are part of the Inter-
totheMAdistribution[7,10,12,13].Depthpro�lesofMA nationalBiosphereReserve“LaEncrucijada”.eclimateof
distribution have been observed, their abundance increase theregioniswarm(28 C)andhumid(89 )withabundant
in deeper layers of the sediment column, because the MA summer rainfall; annua∘l rainfall ranges between 1,300 and
are dependent on heterotrophs and fermenters during the 3,000mm. e rainy season begins betwe%en May and June
organic matter decomposition, its decline is also related to and continues through November; the dry season occurs
adecreaseinbothsulfateconcentrationandredoxpotential fromDecembertoMay[17].Lagoonsystemsarecharacter-
[8]. izedbyhightemperaturesinthewatercolumn(29–35.5 C),
In contrast to estuaries, coastal lagoons generally have withavariablesalinityrangingfrom0to34.5‰ inChantu∘to-
restricted communication with the sea and in tropical Panzacolaandfrom0to22.7‰ inCarretas-Pereyra,depend-
lagoons,asaresultofstrongseasonalprecipitationpatterns, ing on the season. ere is a limited exchange with the sea
therearesigni�cant�uctuationsinriverdischarge,andasso- andasigni�cantphosphorussupplyfromrivers,whichfavors
ciated hydrological conditions (salinity). ese variations highchlorophyll-alevels.Systemsareborderedbymangrove
mightaffectthestructureofmicrobialcommunitiesinvolved forestsandfreshwaterwetlands.Mangrovedetritusresultsin
in the terminal phases of the anaerobic organic matter highhumicsubstancelevels( 150mg/L)intherainyseason
mineralization, as well as to the biogeochemical processes [18]alsorecordinghighammoniumconcentrationsderived
related to it. In spite of its importance, studies focused frommineralization[19]. >
on these ecosystems to assess the dynamics of anaerobic eChantuto-Panzacolalagoonhasanareaof18,000ha
microbiota, especially MA, are scarce. It has been reported and comprises �ve lagoons: Chantuto, Campón, �eculapa,
that MA using methylamines are the primary microbial Cerritos, and Panzacola. In this system, samples were col-
components in sediments of coastal lagoons associated to lected from the Cerritos and Campón lagoons (Figure 1).
mangroves, with higher densities during the summer and e Cerritos lagoon (15 0954.4 N, 92 4534.0 W) has a
premonsoon [14, 15]. In another study, a peak of methane mean depth of 1.1m in the dry season and 1.3m during
∘ ′ ′′ ∘ ′ ′′
productioninmangrovesedimentshasbeenrecordedinthe therainyseason.eCintalapaRiver�owsintothislagoon,
postmonsoonseason[16].InMexico,wherecoastallagoons
contributing a volume between 66.2m /s in October and
areabundant,investigationsonmethanogeniccommunities
0.4m /sinMay(datesproportionatedby3theNationalWater
are virtually absent; hence, the aim of the present study
was to explore the spatial and temporal dynamics of the Comm3issioninMexico).eCamponlagoon(15 1230.0 N,
methanogenic community in sediments from two tropical 92 5124.2 W) has a mean depth of 0.8m in th∘e ′dry s′′ea-
coastal systems: Chantuto-Panzacola and Carretas-Pereyra, son∘ a′nd o′f′ 0.9m in the rainy season. e Cacaluta River
located in the Mexican southern Paci�c and to propose a �ows into this lagoon, with a maximum in�ow in October
conceptual model on MA dynamics in sediments for the (144.2m /s) and a minimum in�ow in May (0.5m /s).
tropicalcoastallagoonsstudied. Sediments are a mixture of silt and sand in both lagoons.
3 3
Archaea 3
eCarretas-Pereyrasystemcoversanareaof3,696haand wassupplementedwithsulfate(�nalconcentration20mM).
comprises four water bodies: Pereyra, Carretas, Bobo, and Bottles were inoculated with 8mL of moist sediment and
Buenavista,samplingtookplaceinPereyraandBobo(Figure incubated at 32 C in the dark for 42 days; the incubations
1). ePereyra lagoon(15 3126.1 N, 92 5124.2 W) hasa were shaken th∘ree times per week. Each experiment was
mean depth of 0.7m in the dry season and 1.0m in the run by duplicate for each sample, including the respective
∘ ′ ′′ ∘ ′ ′′
rainy season. Sediment is silt-sand. e Margaritas River controls (without acetate), with and without sulfates in
drainsintothePereyralagoon(dischargevolumeunknown). the medium. Mineralization was evaluated by determin-
ing changes in acetate concentration and percent methane
eBobolagoon(15 2922.0 N,93 0844.6 W)hasamean
production in bottles. For acetate analysis, 1.5mL samples
depth of 0.5m and 0.7m in the dry and rainy seasons,
∘ ′ ′′ ∘ ′ ′′ were centrifuged at 1,120gf for 10min. e supernatant
respectively. It lacks freshwater inputs and sediment is silt-
was �ltered. A 950 L aliquot was acidi�ed with 50 L of
sand.
HCl (2.2M). e acetate concentration was measured by
�ame ionization gas𝜇𝜇chromatography (Agilent Series𝜇𝜇6890
2.2.SampleCollectionandPreparationProcedures. Sediment
Plus) using an Agilent crosslinked FFAP capillary column
coreswerecollectedwitha45cmlongand4.5cmwideplex-
(15m 0.530mm 1.00 m).Column,injectionport,and
iglasscoringdeviceduringthedry(February,May,andearly
FID temperatures were 120, 130, and 150 C, respectively.
June)andrainyseasons(July,October,andNovember).Tem-
e tem×perature of×the co𝜇𝜇lumn, detector, an∘d injector were
perature, Eh, and pH were simultaneously measured when
120, 150, and 130 C, respectively. e carrier gas was N
sampling the cores at two sediment depths (6 and 12cm)
(4.5mL/min).
∘
usingstandardelectrodesandanIonanalizer(Conductronic
2
pH 120). pH was measured with a glass electrode and the
2.4. Physicochemical Analyses. Sediment samples were cen-
sediment redox potential was measured using a platinum
trifuged at 1,602.76gf at low temperature (4-5 C) for 20
electrode and a saturated KCl calomel reference electrode
minutes to separate porewater from sediments [22]. Pore-
(Instrulab,Mexico).estandardpotentialofthereference ∘
water was �ltered through 0.45 m Millipore membranes
(+198)wasaddedtothemeanvaluetoobtaintheEhofthe
andthefollowingparametersweredetermined:salinity,with
sedimentmedium.Electrodeswereroutinelystandardizedin
the�eldusinga�oBellSolution[20].Subsequently,samples an optical refractometer (Ameri𝜇𝜇can Optical); sulfate [23]
and total dissolved carbohydrates, with the phenol-sulfuric
weretransportedtothelaboratory.
acid technique [24]. Total solids and volatile solids were
Coresobtainedineachsamplingstationweresegmented
quanti�edinmoistsediments[25],porositywasdeterminate
intwosections(0–6cmand6–12cm)underanitrogenatmo-
by measuring the weight loss by drying sediment samples
sphere.Aereachsectionwashomogenizedinaplasticbag
of know volumes and weights. Organic carbon content was
usingsteadyshaking,subsampleswereimmediatelytakento
measured through the method by Gaudette et al. [26] in a
quantifyMA.eremainingsedimentwasmaintainedunder
sedimentsampledriedat60 C.
lowtemperaturetoperformphysical-chemicalanalyses.
∘
2.3. Microbiological Analyses. Enumeration of viable MA 2.5.StatisticalAnalyses. edatamatrixincludedMAabun-
was performed using the Most Probable Number (MPN) dancesandphysicochemicalvariables.Tomeetthenormality
assumptions, data for variables were transformed through
methodbyaten-folddilutionseries(10 to10 )foreach
[27]. For the temporal analysis, variables were
sample using four tubes per dilution. e MPN analyses
−1 −10
grouped into two climate seasons (dry and rainy); for the
included the quanti�cation with substrates commonly used
by the different groups of MA: acetate, CO + H , and lsopgat𝑥𝑥ial𝑥an1alysis,dataweregroupedintotwodepthcategories
(0–6cm and 6–12cm). An analysis of variance (ANOVA)
methanol,withthebasicmediumbyBalchetal.[21].Salinity
in the culture medium was adjusted with a N2aCl (3320g/L) was conducted to test for signi�cant differences between
seasons in each system, on the one hand, and between
solution to obtain similar values to those measured in the
depth categories, on the other. e signi�cance of speci�c
original sediment sample; the pH was adjusted to 7.2 with
differences was assessed through the Tukey-Kramer mul-
a bicarbonate (10 ) solution. Cultures were incubated at
tiple comparison test [27]. A Canonical Correspondence
32 C for one month. Methane was detected with a GOW-
Analysis (CCA) was used to investigate the relationship
MA∘ C Series 580 G%C with a thermal conductivity detector
between microbial abundance and environmental variables
(TCD) under the following operation conditions: column,
[28]. ese analyses were conducted with the Statistica 10
detector, and injector temperatures of 140, 190, and 170 C,
(Academic)andMVSP3.12bSoware.
respectively;25 C/minrate;columnpackedwithcarbosphere
∘
80/100, helium as carrier gas at 25mL/min; polarity of
∘
120mA. 3.ResultsandDiscussion
In order to determine the effect of sulfate on MA for a
competitivesubstrate,methanogenicactivitywasdetermined e aim of this study was to analyze the changes in the
in a medium without sulfates (sulfate-free), using 125-mL abundance and activity of MA and relate these commu-
serumbottles,with42mLoftheBalchetal.[21]andacetate nity characteristics with some physicochemical variables to
assubstratetoa�nalconcentrationof20mM.Experiments propose a conceptual model of methanogenic community
were conducted in parallel in which the culture medium dynamicsincoastallagoonsediments.
4 Archaea
T1:EnvironmentalvariablesinthecoastallagoonsedimentsofChantuto-PanzacolaandCarretas-Pereyra,Chiapas.Mean Standard
deviation.
±
Dryseason Rainyseason
Depth 6 12 6 12
Chantuto-Panzacola
Temperature(C)
Salinity(‰) ∘
Sulphate(mM) 29.2±1.1 28.3±1.3 28.1±1.5 26.7±1.5
pH 21.3±6.1 18.6±5.1 2.5±2.5 2.8±3.1
Eh(mV) 112.006±17.86 93.856±1.324 3.180±41.44 22.986±0.593
TotalSolids(TS,g/L) 7.1±0.1 7.0±0.1 6.7±0.2 6.8±0.1
VolatileSolids(VS,g/L) − ± − ± − ± − ±
Porosity(g/cm3) 445.50±120.65 338.12±79.11 320.79±153.2 303.50±151.07
Organicmatter( ) 42.61±20.19 47.40±34.86 75.82±41.0 68.76±51.98
Organiccarbon( ) 0.3±0.1 0.4±0.08 0.4±0.1 0.4±0.1
Carbohydrates(m%g/L) 7.2±3.4 5.9±3.8 9.8±5.5 5.8±3.2
% 4.1±2.0 Carretas3-.P4e±re2y.r2a 5.7±3.1 3.3±1.8
5.6±4.0 6.5±4.0 5.0±1.0 5.9±4.1
Temperature(C)
Salinity(‰) ∘
Sulphate(mM) 29.4±0.8 28.5±0.7 28.5±1.9 28.3±0.9
pH 27.3±5.3 23.5±3.3 4.3±4.08 3.2±3.8
Eh(mV) 132.906±18.43 114.171±16.36 3.155±21.9486 13.969±1.949
TotalSolids(TS,g/L) 6.9±0.1 6.8±0.1 6.8±0.1 6.7±0.1
VolatileSolids(VS,g/L) − ± − ± − ± − ±
Porosity(g/cm3) 261.70±135.49 229.49±134.29 211.56±123.36 188.41±97.24
Organicmatter( ) 75.22±35.27 85.05±71.58 28.40±12.90 40.39±22.98
Organiccarbon( ) 0.2±0.07 0.2±0.1 0.4±0.1 0.5±0.1
Carbohydrates(m%g/L) 12.5±4.5 25.4±19.2 10.0±4.5 15.7±8.8
% 7.2±4.5 14.5±11.02 6.1±2.6 9.03±5.04
6.8±3.6 6.0±3.5 3.8±1.2 5.3±3.5
3.1.EnvironmentalVariables. Conditionsinthesedimentary the local climate, continental freshwater runoff, connection
habitat in the Chantuto-Panzacola and Carretas-Pereyra with the sea, and in�uence of tides. �noppers and �jerfve
lagoon systems resulted from seasonal variations between [30]pointoutthatseasonalpulsesinfreshwaterin�owexert
the dry and rainy seasons. Temperature in the sediment amarked impact ontheecology ofcoastal lagoons,besides
was higher in the dry season in comparison with rainy controlling salinity, increasing the water level, and holding
season (Table 1); the temporal variations were signi�cant opencommunicationtothesea.
in Chantuto-Panzacola (Table 2). Signi�cant differences in Nosigni�canttemporalvariationswereobservedinthe
pH were observed (Table 2). In the dry season, a greater concentration of total solids and organic fractions (volatile
marine in�uence favors neutral conditions; by contrast, in solids, organic matter, organic carbon, and carbohydrates)
the rainy season the higher �uvial in�ow decreased marine ( ); and their supply was constant through rivers
in�uence, and acid conditions were registered (Table 1). andwetlands.ehighrateoffreshwaterin�owwithorganic
e redox conditions were similar to those reported for d𝑃𝑃ebr𝑃is 0fr.0o5m land and run-off as well as from adjacent
sediments from mangroves [29] and were signi�cantly less mangroves is a key factor related to the contribution of
reductiveintherainyseason(Table1)whenthefreshwater organicmatterincoastalzones[31].
in�ow favored sediment suspension in the water column Spatially there was no pattern of physicochemical con-
(turbidity=126–224NTU),withanincreaseinporosityand ditions in the sedimentary habitat as evidenced by the null
less reduced conditions at the sediments. In the dry season signi�cance observed for the temperature, pH, salinity and
redoxpotentialdecreasedasaresultofsedimentdeposition sulfates ( ). An exception was the Eh, which
(turbidity=31–107NTU). decreased signi�cantly with depth (Tables 1 and 2). e
emajorchangesweredeterminedinsalinityandsulfate vertical �u𝑃𝑃ctu𝑃atio0n.s05in Eh may be attributed to a reduction
content(Tables1and2).Maximumvalueswererecordedin intheoxygendiffusionrateinporewaterasthedepthofthe
thedryseasonandminimumintherainyseason;eventotally sediment column increases [32]. ere were no signi�cant
freshwater conditions existed in both systems in October variationsinsolidscontentandorganicfractions( )
(0‰). e decrease in salinity and sulfates was due to an (Table1).Howevertheorganiccarboncontentwashigherin
increasein�uvialin�owandprecipitation.Salinityincoastal the sediment layer of 12cm, dos Santos Fonseca e𝑃𝑃t𝑃al.0[.0353]
lagoonsvariesaccordingtoannualcycles,whichdependon point out that this behavior seems to result from the fact
Archaea 5
T2:ResultsoftheANOVA(F)andmultiplecomparisonsanalysis(MCA)(Tukeytest)ofenvironmentalandmicrobiologicalvariables
betweenseasonsandsedimentdepthinChantuto-PanzacolaandCarretas-Pereyra.P:signi�cance.Seasons:D:dryandR:rainy.Depth:6cm
and12cm.
Season Depth
Variables
F P MCA F P MCA
Chantuto-Panzacola
Temperature(C) 4.66 0.0421 D R 3.75 0.0684 —
Salinity(‰) ∘ 62.03 0.0000 D R 0.08 0.9311 —
>
Sulphate(mM) 109.00 0.0000 D R 0.45 0.5349 —
>
pH 28.81 0.0000 D R 0.01 0.9427 —
>
Eh(mV) 4.54 0.0446 D R 38.04 0.0000 6 12
>
MA-Acetate(cells/g) 112.38 0.0000 D R 0.01 0.7842 —
< <
MA-Hydrogen(cells/g) 15.10 0.0008 D R 0.05 0.8195 —
<
MA-Methanol(cells/g) 5.92 0.0236 D R 3.36 0.0528 —
<
Activity+SO (mMacetate/gVS/day) 14.71 0.0009 D R 1.50 0.2321 —
4
<
CH +SO 66.12 0.0000 D R 0.85 0.3085 —
4 4
>
CH SO 4.96 0.0364 D R 2.17 0.0831 —
4 4
<
Carretas-Pereyra
− <
Temperature(C) 0.97 0.3344 1.28 0.2705 —
Salinity(‰) ∘ 154.47 0.0000 D R 0.26 0.6156 —
Sulphate(mM) 210.03 0.0000 D R 0.45 0.5101 —
>
pH 10.47 0.0038 D R 1.09 0.3088 —
>
Eh(mV) 3.80 0.0641 — 19.80 0.0002 6 12
>
MA-Acetate(cells/g) 4.82 0.0390 D R 0.13 0.7193 —
<
MA-Hydrogen(cells/g) 9.39 0.0057 D R 0.48 0.4952 —
<
MA-Methanol(cells/g) 2.71 0.1142 — 1.06 0.3142 —
<
Activity+SO (mMacetate/gVS/day) 12.62 0.0018 D R 0.46 0.5042 —
4
CH +SO 15.39 0.0007 D R 6.24 0.0204 6 12
4 4
>
CH SO 7.21 0.0135 D R 7.88 0.0103 6 12
4 4
< <
− < <
thatthemostlabilesubstrateisreadilyusedbythemicrobial was H -CO and the lowest levels correspond to acetate
community in the top centimeters of sediment, and the (Table3).
refractoryfractionbuildsupindeeperlayers,whereitwillbe e2cons2tantoccurrenceofMAwasprobablytheresultof
degradedslowly.epresenceofrefractorymaterial(wood theirabilitytousedifferentelectrondonorsinanecosystem
andphytoplanktondebrisidenti�edwithalightmicroscope with a constant supply of organic matter provided by the
Zeiss Axioscop) concentrated largely in the 6–12cm-deep rivers and run-off from adjacent mangroves. Verma et al.
layer in Pereyra and Campón lagoons seem to support this [34]mentionedthatthecontinuedpresenceofMAincoastal
hypothesis. lagoons is possible by the presence of “noncompetitive”
substrates, (methanol and methylamines), that are used
exclusively by the MA, as well as the constant availability
3.2. Abundance and Distribution of MA. Viable MA in
of “competitive” substrates (acetate and hydrogen), used by
the sediments of Chantuto-Panzacola and Carretas-Pereyra
methanogenandotheranaerobicmicroorganisms.
systems were evaluated with MPN, obtaining a range of
Methanol was an important substrate in both seasons,
abundancebetween10 and10 cells/g.MAdensityreached may be released from methoxy groups during degradation
peak levels in the rain4y season7, with a signi�cant decrease of lignin. Methanol-utilizing MA have a broad substrate
of as much as two orders of magnitude during the dry spectrum, can also grow on acetate, growth on H -CO
season ( ) (Figures 2(a)–2(c)). In the rainy season, is restricted to some Methanosarcina species [5]. ere is
increased freshwater input created favorable conditions for evidence supporting the hypothesis that cometabolism2 of a2
MA prol𝑃𝑃ife<rat𝑃io𝑃𝑃n𝑃. In this season highest levels of MA were broadrangeofsubstratesbygeneralistmicroorganismsmay
recordedwithacetateandmethanolinChantuto-Panzacola confercompetitiveadvantages[35].Purdyetal.[13]mention
andwithmethanolandH -CO inCarretas-Pereyra.During that, within the methanogenic community, the presence of
thedryseason,highMAlevelswereobtainedwithmethanol generalistgroupsimpliesthatthesearebetteradaptedtothe
inbothlagoonsystems;th2esec2ondsubstrateinimportance variationsintheestuarineconditions.Additionallymethanol
6 Archaea
Chantuto-Panzacola Carretas-Pereyra
8 8
S) 7 7
T
g
cells/6 6 6
ogh:
e (lept
atD 5 5
et
c
a
M-
A 4 4
3 3
8 8
S) 7 7
T
g
ogcells/h: 12 6 6
ate (lDept 5 5
et
c
a
M-
A 4 4
3 3
Dry Rainy Dry Rainy
(a)
Chantuto-Panzacola Carretas-Pereyra
7.5 7.5
7 7
S)
T
g 6.5 6.5
cells/ 6 6
n (logpth: 65.5 5.5
drogeDe 5 5
y
h
M- 4.5 4.5
A
4 4
3.5 3.5
7.5 7.5
7 7
S)
T
g 6.5 6.5
cells/2 6 6
g1
n (lopth: 5.5 5.5
ee
gD
dro 5 5
y
M-h 4.5 4.5
A
4 4
3.5 3.5
Dry Rainy Dry Rainy
(b)
F2:Continued.
Archaea 7
Chantuto-Panzacola Carretas-Pereyra
8 8
7.5 7.5
S)
T
ells/g 7 7
c
g6 6.5 6.5
nol (loDepth: 6 6
a
h
met 5.5 5.5
M-
A 5 5
4.5 4.5
8 8
7.5 7.5
S)
T
ells/g 7 7
c2
nol (logDepth: 1 6.65 6.65
a
h
met 5.5 5.5
M-
A 5 5
4.5 4.5
Dry Rainy Dry Rainy
(c)
F2:TemporalandspatialvariationintheabundanceofMA(logcells/gTS).
T 3: Abundance of MA, acetoclastic activity, and methane production in sediments of Chantuto-Panzacola and Carretas-Pereyra,
Chiapas.Meanvalues.
Dryseason Rainyseason
Depth 6 12 6 12
Chantuto-Panzacola
MA-acetate(cells/g) 1.30 105 2.99 104 2.20 107 2.09 107
MA-Hydrogen(cells/g) 1.63 106 9.55 104 9.37 106 8.63 106
MA-methanol(cells/g) 1.79×106 1.97×107 1.17×107 2.06×107
AcetateactivitywithoutSO (mMacetate/gVS/day) 0.×03 0.×03 0.×02 0.×01
AcetateactivitywithSO (−m2Macetate/gVS/day) 0.×05 0.×03 0.×01 0.×01
4
CH withoutSO −2 4.81 7.91 23.50 29.73
4 4
CH withSO −2 2.78 4.63 5.64 8.77
4 4
% −2 Carretas-Pereyra
4
%MA-acetate(cells/g) 4.52 104 6.17 104 1.90 106 1.32 106
MA-Hydrogen(cells/g) 1.34 105 1.51 105 4.49 106 2.64 106
MA-methanol(cells/g) 1.34×106 8.24×106 1.27×107 2.21×107
AcetateactivitywithoutSO (mMacetate/gVS/day) 0.×03 0.×02 0.×01 0.×01
AcetateactivitywithSO (−m2Macetate/gVS/day) 0.×04 0.×03 0.×01 0.×01
4
CH withoutSO −2 7.83 13.01 15.42 23.47
4 4
CH withSO −2 4.02 6.55 6.41 13.02
4 4
% −2
4
%
8 Archaea
allowsMAtomaintaintheirpopulationsinthepresenceof (Table3;Figures3(a)–3(c)).Verticalvariationsdidnotreach
sulfate,whichactfavoringsulfatereduction.ekeyroleof statisticalsigni�cance( ).
othermethylatedcompoundswasdemonstratedinmangrove Methaneformationwasobservedinallexperiments,with
areasinIndia,whereMAwerequanti�edfrommethylamines differences depending𝑃𝑃on𝑃𝑃th𝑃𝑃e𝑃speci�c conditions of each
[14,15]. medium. e addition of acetate results in an increase in
In the rainy season, methanol remained important, but methane production in relation to the amount observed in
theabundanceofMAfromhydrogenandacetateincreased controls(nocarbonsupplementation).
under low sulfate concentrations, hydrogen theoretically Methane production was higher in sulfate-free media
contributes33 tototalmethanogenesiswhencarbohydrates compared with sulfate-enriched media (Table 3; Figures
or similar organic matter are degraded, being important in 3(b)–3(d)). Temporal differences ( ) in methane
environments%with high sedimentation rates ( 10cm/year) production from acetate were observed in both systems.
and organic carbon supplementation [36]. In the coastal Methane levels were higher in the r𝑃𝑃ain𝑃y se𝑃a𝑃𝑃s𝑃on than in the
lagoons studied, a high concentration of org≈anic carbon dryseason(Table3).Signi�cantverticalchanges( )
(3.4–14.5 ) was quanti�ed, and a sedimentation rate of wereobservedonlyinCarretas-Pereyra:alowerproduction
6cm/yearwasobservedinCarretas-Pereyra.Acetatecanpro- in the upper 6cm and a higher methane producti𝑃𝑃on𝑃in𝑃𝑃𝑃th𝑃e
duceappr%oximatelytwothirdsoftotalmethaneinfreshwater 6–12cmlayer(Table3,Figures3(b)–3(d)).
sediments; however, its contribution to methane formation e presence of sulfate in the culture media in�uenced
decreaseswhenisconsumedinotheranaerobicprocessesas methanogenicactivity.Inthesulfate-freeexperimentsapeak
the sulfate reduction [4]. e effect of sulfate on methano- of acetoclastic activity was observed coupled with a rise in
genesiswasdemonstratedintemperateestuaries,wherethe methane production in sediments during the rainy season
contribution of acetate for this process has been found to and in the deep layer, suggesting that methanogenesis was
increasewhensulfateconcentrationislowinfreshwaterzone, favored.Studiesdemonstratedthatpotentialmethanogenesis
andthesulfatereductiondecreased[7,13].eacetateand from acetate was higher in the absence of sulfates [37]. By
hydrogen are also important substrates for methanogenesis contrast, the addition of sulfate resulted in an increase of
insaltmarshesareas[10]. acetoclastic activity in the dry months and in the upper
is study has revealed that acetate-utilizing and sediment layer, and methane production declined. In sedi-
hydrogen-utilizing MA does not have a distinct vertical ments of coastal lagoons and mangrove areas in India, an
distribution pattern in Chantuto-Panzacola and Carretas- increase in the production and emission of methane was
Pereyra sediments, whereas the methanol-based group determinedinfreshwaterareascomparedtobrackishregions.
apparently being more abundant in the 6–12cm layer Also, methane emissions were higher in the postmonsoon
( ). e presence of MA along 12cm of sediment season, when salinity and sulfate concentration were lower
column seems to be a result of the availability of substrates [16,34].
fo𝑃𝑃r t𝑃he𝑃se𝑃𝑃𝑃microorganisms; the constant supply of different
substrates favors the presence of MA at different sediment 3.4.EnvironmentalVariablesandMA. ecorrelationcoef-
layers as also has been demonstrated in sediments of tidal �cients between environmental variables and ordination
�ats,coastalmarshes,andmangroves[8,10,14]. axes (interset correlation) obtained by CCA denote the
relative importance of each environmental variable in the
3.3. Acetoclastic Metabolic Activity. In all kinetic experi- distributionofthemethanogeniccommunity.ForChantuto-
ments,therewasanincreaseintheconcentrationofacetate Panzacola, the MA-environment correlation was 0.92 cor-
in the �rst days, along with other volatile fatty acids (pro- responded to a salinity-sulfate gradient and 0.60 for pH.
pionate and butyrate); this pattern reveals the presence of CCAresultsforCarretas-Pereyrashowedacorrelationof0.74
fermentationprocessesinsediments.econtinuedpresence for pH and volatile solids, and 0.43 for volatile solids. e
of acetate along with other intermediaries (butyrate and ordination diagram obtained by CCA showed a change in
propionate) is similar to that reported in other studies the structure of the methanogenic community with regard
where methanogenesis has been assessed [37]. Acetate is to certain environmental variables (Figure 4). e �rst
an important intermediate produced during the anaerobic axis accounted for 65.62 of total variance in Chantuto-
mineralization of organic matter, followed by propionate Panzacola,correspondingtoasalinity-sulfategradient(Fig-
andothervolatilefattyacids[38].efermentationactivity ure 4(a)). In the right sid%e of the diagram, those sites with
is important because it releases organic substrates, such as thehighestsulfateconcentration,temperature,andpH(dry
acetate,thatcanbeusedbytheMA,whichcannotdirectlyuse season)weregrouped,intheseconditionsmethanol-utilizing
complexorganiccompounds.Subsequenttotheproduction MA were abundant. e le side of the plot-grouped sites
ofvolatilefattyacids,acetateconsumptionstartedonday7 with highest total solids content where hydrogen-utilizing
in sulfate-enriched media and between days 14 and 21 in MA prospered, whereas acetate-utilizing MA abound in
sulfate-freemedia.Methaneproductionwasrecordedonday sites with a higher porosity and less reduced conditions
21. (Figure 4(a)). In Carretas-Pereyra, to the plot’s upper le
Acetoclastic activity in sulfate-free experiments had no side, the �rst axis accounted for 29.08 of variance and
signi�cant temporary differences ( ) (Figures salinity-sulfate, Eh and organic carbon concentration were
3(a)–3(c)). e experiments with sulfate showed signi�cant allcorrelatedwithhydrogen-utilizingMA%abundance,mainly
temporal �uctuations, with high val𝑃𝑃ues𝑃in t𝑃h𝑃e𝑃𝑃dry season during the rainy season. Abundance of methanol-utilizing
Archaea 9
Chantuto-Panzacola Chantuto-Panzacola
y) 0.09
a
d
S/ 0.08
V
g
e/ 0.07
at
et 0.06
c
y (mM aDepth: 6 00..0045
vit
cti 0.03
a
astic 0.02
cl 0.01
o
Aut 0
0.09
y)
a
d 0.08
S/
V
g 0.07
e/
at 0.06
et
M ach: 12 0.05
mpt 0.04
y (De
vit 0.03
acti 0.02
c
asti 0.01
cl
uto 0
A +SO4 −SO4 +SO4 −SO4
Dry season Rainy season
(a)
Chantuto-Panzacola Chantuto-Panzacola
45
40
%) 35
n ( 30
o
oducti pth: 6 25
pr De 20
e
n
a 15
h
et
M 10
5
0
45
40
%) 35
n ( 30
o
ducti h: 12 25
e pro Dept 20
n
a 15
h
et
M 10
5
0
+SO4 −SO4 +SO4 −SO4
Dry season Rainy season
(b)
F3:Continued.
10 Archaea
y) 0.09 Carretas-Pereyra Carretas-Pereyra
a
d
S/ 0.08
V
e/g 0.07
at
et 0.06
c
y (mM aDepth: 6 00..0045
ctivit 0.03
c a 0.02
asti 0.01
cl
o
ut 0
A
y) 0.09
a
S/d 0.08
V
g 0.07
e/
etat 0.06
y (mM acDepth: 12 00..0045
vit 0.03
cti
a 0.02
c
asti 0.01
cl
uto 0
A +SO4 −SO4 +SO4 −SO4
Dry season Rainy season
(c)
Carretas-Pereya Carretas-Pereyra
45
40
35
%)
n ( 30
o
ucti h: 6 25
prod Dept 20
e 15
n
a
h
et 10
M
5
0
45
40
35
%) 30
n ( 25
o
ducti h: 12 20
e pro Dept 15
n
a 10
h
et
M 5
0
+SO4 −SO4 +SO4 −SO4
Dry season Rainy season
(d)
F3:TemporalandspatialvariationsofacetoclasticactivityandmethaneproductioninChantuto-Panzacola(a,b)andCarretas-Pereyra
(c,d).