ENDANGERED ANTARCTIC ENVIRONMENTS - SOEST

49 Pages·2007·1.04 MB·English

31Aug2004 11:56 AR AR224-MI58-24.tex AR224-MI58-24.sgm LaTeX2e(2002/01/18) P1:IKH
10.1146/annurev.micro.57.030502.090811
Annu.Rev.Microbiol.2004.58:649–90
doi:10.1146/annurev.micro.57.030502.090811
Copyright(cid:1)c 2004byAnnualReviews.Allrightsreserved
FirstpublishedonlineasaReviewinAdvanceonJuly14,2004
E A E
NDANGERED NTARCTIC NVIRONMENTS
Don A. Cowan andLemese Ah Tow
DepartmentofBiotechnology,UniversityoftheWesternCape,Bellville7535,CapeTown,
SouthAfrica;email:[email protected];[email protected]
g
or
s. KeyWords Antarctica,DryValleys,microbialcommunities,microbialendemism,
w
viey. climatechange,environmentalimpact,ssurRNA
ualree onl ■ Abstract TheAntarcticcontinentharborsarangeofspecializedandsometimes
als.annonal us hmiginhelryalloscoaillisz,erdicmhoicrrnoibthiaolgbeinoitcospoeisl.s,Tghleasceiailnacnluddseebaiiocteo,piecse-acsosvoecrieadteldakweisth,tdraenssicluccaetendt
ded from arjourn9/05/07. For pers rmtAtihoosoecnkroasespu,,edpranelunivscndiiacrdgtoceieanorotsmnittoahoennenf,drtmhmainyloagpelleelxoycrtfsruhealtemalhiarneetpiestthdry(uy,isehlnooicimggllsuhei.ndcpAreienotlrigblicoiaalmdroleiwecdctirhhtvaeoaedmdrriassapci,ttetiwyeorraneiitnzuflceorutdehmx,ebeewsyse,citadlbhoneiesdoetitelmroomptwpoepostneshruieeattxitropupineoraneinontdflftssuotwacnfthrteuouesomar)e-r.
a0
nloon wecanmakeanaccurateassessmentoftheimpactsofenvironmentalchange,human
wY intervention,andothernaturalandunnaturalimpositions.Atpresent,itispossibleto
690. DoERSIT monalkyegreenaesroanlapbrleedipcrteiodnicstioonnspoabssoiubtlethcehapnhgyessicianlmefifcercotbsiaolfcloomcaml culnimityatsetrcuhcatunrgee.,Tbhuet
49-NIV consequencesofsomedirecthumanimpacts,suchasphysicaldisruptionofmicrobial
58:6S U soilcommunities,areobviousifnotyetquantitated.Others,suchasthedissemination
4.N ofnonindigenousmicroorganismsintoindigenousmicrobialcommunities,arenotyet
00KI understood.
2P
ol. HO
MicrobiOHNS CONTENTS
nu. Rev. by J ICNOTLRDODDEUSCETRIOTNMI.N.E.R..A.L..S.O.I.L.S................................................................................665501
n
A TheAntarcticDryValleys .............................................651
DryValleyMineralsSoils:ThePhysicalandChemicalEnvironment ...........652
ColdDesertMicrobialCommunities .....................................654
SensitivitytoEnvironmentalImpacts ....................................657
LITHICMICROBIALCOMMUNITIES ...................................659
Introduction ........................................................659
ThePhysicalandChemicalEnvironment .................................659
CompositionofLithicCommunities .....................................660
SensitivitytoEnvironmentalImpacts ....................................661
LAKECOMMUNITIES ................................................662
Introduction ........................................................662
ThePhysicalandChemicalEnvironment .................................662
0066-4227/04/1013-0649$14.00 649
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650 COWAN (cid:1) AHTOW
MicrobialLakeCommunities ..........................................664
WaterColumnCommunities ...........................................665
MicrobialMats ......................................................665
SensitivitytoEnvironmentalImpacts ....................................667
FLOWINGWATERSYSTEMS ..........................................668
Introduction ........................................................668
MicrobialCommunitiesinAquaticSystems ...............................668
SensitivitytoEnvironmentalImpact .....................................670
ICEMICROBIOLOGY .................................................670
Introduction ........................................................670
SeaIce ............................................................671
g
or PolarandGlacialIce .................................................671
s.
w LakeIce ...........................................................673
e
ualrevie only. CSerynosictoivniittyestoHEonlevsiro.n.m.e.n.t.a.l.Im..p.a.c.ts..........................................................................667763
als.annonal us FEILnLtrFodIEuLctDionCO.M..M..U.N..IT.I.E.S........................................................................................667777
ded from arjourn9/05/07. For pers ORITFSnNeehtlneIrlTosfiPidHethuilvOdycisttGMiiyocEnaitcoNlraoEI.nCb.ndi.vSo.iClOr.ooh.IgneL.ymm.Eei..cNn..at..Vla..lEI..RInm..vO..ipN..rao..Mcn..tms..E..eN...nT...t...S....................................................................................................................................................................666667777799997
wnloaY on 0 MSeincsriotbiviiotlyogtoyEonfvOirronnitmhoengteanlicImSpoailcsts.........................................................................668800
0. DoRSIT CONCLUSIONS ......................................................681
69E
49-NIV
58:6S U INTRODUCTION
4.N
00KI
2P
ol. HO The Antarctic continent offers a range of extreme climatic conditions that con-
MicrobiOHNS sattimtuotsepshoenreicohfuthmeidhiatrys,hleoswtelnivqiuriodnmwaetnetrsaovnaEilaarbtihli.tEy,xatrnedmheisgohfpteemriopdericatuinrcei,dleonwt
Rev. by J rcaodnitaitnieonntwreiltahtilvoenlygipnehroiosdpsitaobflecofmorptlheeteddevaerklonpemsseanltlocfobnitorilbougtiecatlocroemndmeurinnigtieths.e
u.
n We must remember that the concept of an extreme environment is, in part,
n
A
anthropogenic and therefore artificial. The discomforts and difficulties that the
mesophilic mammal Homo sapiens experience in Antarctic conditions are not a
good yardstick for assessing the success, or otherwise, of microbial existence.
Nevertheless, the Antarctic environment does impose real thermodynamic and
kineticlimitationsonmicrobialgrowth.Thisisevidentinthathighereukaryotes
are restricted to the more northern latitudes (the Antarctic peninsula) and that
bothmicrobialbiomasslevelsandspeciesdiversityaresignificantlylowerinthe
most extreme ice-free region of Antarctica, the McMurdo Dry Valleys, than in
temperateenvironments.However,wheresuitablenichesarefound,microbiallife
exists. The presence of liquid water stimulates the most productive and diverse
microbialcommunities:inshallowlakemargins,glacialandsnowfieldmeltwater
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ENDANGEREDANTARCTICENVIRONMENTS 651
TABLE1 ImpactsonAntarcticmicrobialbiotopesandcommunities
Source Nature Effect(s)
Anthropogenic Movement,transport,physical Physicaldisturbancetosoilsurfaces;
activities disseminationofnonindigenous
microorganisms
Productionofwastematerials Chemicalcontamination/eutrification
ofsoilandwatersystems
Climatic Temperaturerise Lossofice;increasedmicrobialgrowth;
increasedwateravailability
g
or Temperaturedecrease Increaseinicecover;reducedmicrobial
ws. activity;decreasedwateravailability
e
viy. ElevatedUVradiation Changesinmicrobialdistribution
ualree onl
als.annonal us streams and “flushes,” and meltwater pools in glacial ice. Elsewhere, microbial
aded from arjourn09/05/07. For pers ctsoapofkamlMicingmegahsuntsinyhaniveotcliafterieytslhrasbaeutarinAlelidltnimeyntraeoasrnrrcteoodtinccpdkehemssys,,iisihccnicracocavabrtleialioyacanlkcr.chseoisienmtvriremcodtcuekandi.sfittiEnreanestdaabo,raelaliantphndoictceeevnmbetnieiactwlwrloyiebtehsineainnltshtciheoteimvliienmmttoeiutrnaestixtitiotiteeinarss-l,
wnloY on nalimpacts(Table1).ThephysicalfragilityoftheDryValleysoilsandAntarctic
DoT peninsular fellfields makes their microbial communities susceptible to physical
690. ERSI andclimaticdeterioration.Theextenttowhichthestructuresofthesecommuni-
49-NIV tiesmightbemodifiedbytheimpactofnonindigenousmicrobialcontamination
58:6S U remains to be evaluated. Others, such as ice, lake, and flush communities, are
4.N obviouslysusceptibletoregionaltemperaturechanges.
200PKI Itisimportanttounderstandtheimmediacy,significance,andultimateconse-
ol. HO quence of these natural (climatic) and unnatural (anthropogenic) impacts. How-
MicrobiOHNS elovgeirc,athlicsowmiplllebxeitpyoosfsiebalcehohnalbyiwtaht,eannwdtehheawveayaidnewtahiliecdhtuhnedceorsmtamnduinnigtyosftrtuhcetubrioes-
Rev. by J andrelationshipsrespondtoenvironmentalchangesandimpositions.Wereview
u. the current state of knowledge of the microbiology of major Antarctic habitats
n
An (seeFigure1forprincipallocations),andconsiderthesemicrobialcommunities
inlightofknownandprojectedenvironmentalimpacts.
COLDDESERTMINERALSOILS
TheAntarcticDryValleys
Ice-free regions represent less than 2% of the total land area of the Antarctic
continent(35).TheMcMurdoDryValleysofEasternAntarcticacomprisemuch
ofthetotalice-freeland,althoughice-freeregionsarealsofoundintheVestfold
Hills, the Bunger Hills, and at various sites in the Transantarctic mountains and
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652 COWAN (cid:1) AHTOW
g
or
s.
w
e
viy.
ualree onl
als.annonal us
ded from arjourn9/05/07. For pers
a0
nloon
DowTY Figure 1 Continental Antarctica, showing the most important sites for terrestrial
0. RSI microbiologicalresearch.
69E
49-NIV
4.58:6NS U oEnartthheaAndnteaxrcpteicriePnecneinasuvlaar.ieTtyheoDfhryarVshalelenyvsiraornemtheentcaollcdoenstdiatniodndsr(ieTsatbdlees2e)r.tsTohne
00KI extremelylowtemperatures,lowprecipitation,lowhumidities,highsaltcontent,
2P
ol. HO katabaticwinds,steepphysicalandchemicalgradientsintheterrestrialhabitats,
MicrobiOHNS asunrdvliovwalo(7rg4a,n1i6c5m).attercontentimposemajorlimitationsonmicrobialgrowthand
Rev. by J TheMcMurdoDryValleysarenothomogeneoussystems.Theyofferarange
u. of widely differing microbial biotopes that includes lakes (both freshwater and
n
n saline), freshwater streams, and at least two types of soil, moist soils that are
A
exposedtoglacialmeltwateranddesiccatedmineralsoils(153).
DryValleyMineralSoils:ThePhysicaland
ChemicalEnvironment
DryValleymineralsoilsarethemostbarrensoilsofthesnow-freeregionsofthe
Antarctic continent (Figure 2). The upper horizon of mineral soils typically has
a low water content (0.5%–2% wt) due to the low level of precipitation and ex-
posuretothedesiccatingatmosphere.Lowhumidity(<10%RHinwinter),low
precipitationandstrongkatabaticwinds(especiallyduringwinter)resultinlong
periods of desiccation (74). The mean annual precipitation of 15 g cm−2 year−1
31Aug2004 11:56 AR AR224-MI58-24.tex AR224-MI58-24.sgm LaTeX2e(2002/01/18) P1:IKH
ENDANGEREDANTARCTICENVIRONMENTS 653
TABLE2 EcologicalfactorsinAntarcticcolddeserts(reproducedfromReference165with
permission)
Favorableconditions Unfavorableconditions
North-southorientationofvalley(across East-westorientationofvalley(along
katabaticwinddirection) katabaticwinddirection)
Northernexposure Southernexposure
Gentlenorth-facingslope Flatorsouth-facingslope
Highsolarradiation Low,sporadicsolarradiation
g Microclimateabovefreezing Microclimatebelowfreezing
or
ws. Absenceofwind Highwinds
e
ualrevie only. NHoigrhthheurlmyiwdiitnidess LSoouwthheurmlyidwiitniedss
als.annonal us Sloworimpededdrainage Rapiddrainage
ded from arjourn9/05/07. For pers LTNAreopannpngsrstoalhulxytciymedsnuaottrieapllsteyi,bobnbnaelleouasftnraacvleadpiHliaobnliecwcoamterposition SSHOahiplgoathyrqtu(sdoeouriprllaseo,tbwiuobn)nlebposaHflaanvcaeidlabioleniwcactoemrposition
nloaon 0 Organiccontamination(e.g.,skuas,seals) Noorganiccontamination
wY
DoT
0. RSI
58:649-69S UNIVE imhsoiredinizttoyir,ne.mlyucinhothfethfeorsmnowofssunbolwim.eHsowwitehvelirt,tlbeemcaouisseturoefptheneeltorawtinagtmthoespuhpepreicrshoui-l
4.N
00KI Acementedpermafrostlayerispresentatthebaseofthemineralsoilprofile(as
2P
ol. HO littleasafewcentimetersbelowthesoilsurface)(Figure3).Despitethepresence
MicrobiOHNS omfatfhreospteirnmtearffraocset(laoyweirn,gintsouftfihecisetnetelpiqdueisdicwcaatteiornisgorabdtaieinnet)dtforosmuptphoertmceoltnesdispteenr-t
Rev. by J micTrhoebiDalrygrVoawlltehyisnotfhAenstuarrfcatciceaseoxilpse(r1ie6n4c)e.extremelylowtemperatures,themean
nu. annualairtemperaturerangingfrom–20to–25◦C(164).Insummer,themeanair
n
A temperatureis∼0◦C,whilesurfacegroundtemperaturesaveragearound+15◦C
duringperiodsofdirectsunlight.Prolongedperiodsofextremelylowtemperatures
(−55◦C) prevail during winter (159). Cameron (27) reported that a Ross Desert
soil experienced a temperature change from –15 to +27.5◦C within 3 h. Such
temperaturefluctuationsleadtofreeze-thawcyclesthatarepotentiallylethaltosoil
microbiota.ThesurvivalofmicroorganismsinDryValleymineralsoilsdepends
ontheirhydrationstate,theircompatiblesolutecontent,andtheirabilitytoswitch
metabolismtosynthesizecryoprotectants(24).
Besides tolerating the desiccating conditions and extreme temperatures, mi-
croorganisms inhabiting the mineral soils are subjected to osmotic stress due to
highsaltconcentrationsfromaccumulatedsodium,calcium,magnesium,chloride,
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654 COWAN (cid:1) AHTOW
sulphate, and nitrate (74). The high salt concentrations within the mineral soils
resultfromupwardtransportfromthesubstratumaswellassurfacesupplementa-
tion resulting from sea spray blown inland by onshore winds (153, 165). The
soluble nitrogen (N) concentrations measured in desert soils range from 0 to
1250 µg g−1 soil in the form of NO−-N and from 0.3 to 40 µg g−1 soil in the
3
form of NH +-N (153). Nitrate concentrations in Antarctic mineral soils are the
4
lowest reported for terrestrial soils (such as forest and cultivated soils) and are
derived primarily from atmospheric precipitation (154). Soluble phosphorus (P)
concentrations in Antarctic desert soils are between <0.01 and 120 µg g−1 soil
(153).
g
or The Dry Valley mineral soils contain low levels of organic matter (an av-
ws. erage of 0.064 ± 0.035% total organic carbon) (93). Soil organic matter in
e
ualrevie only. tohregaTnaicylmoratVtearl,lelyacuresgtriionne-adreirsievsedfroormgasneicvepraalrtiscouulracteess,, csruycphtoaesndmoalirtihniec-adlelyrivdeed-
als.annonal us roifveodrgoarngiacnmicamttearttferro,manidnlaainrsdpolarkae(s2(2l)a.cSutsrtorinnge-kdaetraibvaetdicpwaritnicduslaatieds)thaenddimspaerrisnael
ded from arjourn9/05/07. For pers ebcnolovmwirmnounsnmainteidnetssa.lloonwtos tmheinderisatlrisbouitliosnurofafcoersg.aPnhicysmicaatltearbfrraosmionenodforloitchkics mbyicwroibnida-l
a0
nloon ColdDesertMicrobialCommunities
wY
DoT
0. RSI MicrobialabundanceanddiversityinAntarcticdesertsoilsdependonanumber
58:649-69S UNIVE ohcofablslipetceatcteicdfiocfmreopcmoosloiftogiouicnradlaifnfadfcetraoesrnssto(cl2oi9act)aet(diToamnbsilce(rao1lb)l.ieaTxlhpciesormiiespneocvisinidtgieondntiffifrneormRenoctsosemdDappeashreiiscrotcnshsoaiolrs-f
4.N
00KI acteristics) (Table 3) (24, 25, 28, 165). For example, soil water content and cell
2P
ol. HO numbersarepositivelycorrelated;low-organic-contentsalinesoilscontainlower
MicrobiOHNS ntiuomnmbeursstobfeceuxleturcriasbeldewmhiecnroionrtgearpnriesmtinsgthqaunanntiotnatsiavleindeatsaofilrsom(29cu).ltHuroew-deevpeer,ndcaeun-t
Rev. by J econnutmaienralotiwonlesvtueldsieosf,mwihcircohorhgaavneisrmepse[aet.egd.,ly10s2h–o1w0n4gth−a1;t(D2r4y,2V5a,l2le8y)]m.Hinoewraelvseoriilns
u.
n situATPanalysisdatahaveindicatedthatDryValleymineralsoilscontainthree
n
A
to four orders of magnitude higher levels of microbial biomass than previously
reported(41).
Mostmicroorganismsisolatedfrommineralsoilsarepsychrotrophs,perhapsnot
surprisinglybecausetheseorganismsarebetteradaptedtosurvivethetemperature
cyclingofsurfacesoilsthantruepsychrophiles.Psychrophilesaremoreabundant
inthepermafrostlayer,wheretemperaturefluctuationsarelow.Mostoftheviable
(i.e., culturable) bacteria in Ross Desert soils are found in the permafrost layer
andtowardthesurface(30).Chromogenicbacteriacolonizesoilsurfaces,whereas
nonpigmentedbacteriaweremainlyfoundbelowthesoilsurfaces(30).Antarctic
soils are largely aerobic and most microorganisms isolated from this habitat are
aerobicheterotrophs.Althoughafewanaerobicbacteriahavebeenisolatedfrom
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ENDANGEREDANTARCTICENVIRONMENTS 655
TABLE3 SoiledaphicandmicrobialcharacteristicsatfourDryValleysites(reproducedfrom
References24,25,and28withpermission)
Properties VictoriaValley CoalsackBluff BarwickValley WheelerValley
Position 77◦20(cid:3)S 84◦14(cid:3)S 77◦20(cid:3)S 77◦12(cid:3)S
Substratum Dunesand Sandon Patternground Gray-brown
BergMoraine sand sand
Moisture(%drywt) 0.14 1.58 1.74 4.30
pH 8.0 6.5 8.3 8.1
org OrganicC(%wt) 0.02 0.38 0.02 0.17
s.
w OrganicN(%wt) 0.003 0.024 0.004 0.024
e
ualrevie only. In(oprpgmandircyiownts)
ded from arjournals.ann9/05/07. For personal us CFCNNSCPUOOalHO(4443G.D.W.)−1 1128064.3.00055 51007101..42010200 501130..185 042N71.105D20
a0
wnloY on Bacteria
DoT 2–5◦C 50 29,000 52,000 120,000
0. RSI 10–22◦C 12,000 400 85,000 1.3×106
58:649-69S UNIVE YMAeligacasrteosfungi 000 050100 3—001000 2260.40×106
4.N
00KI
2P ND,notdetermined
ol. HO
MicrobiOHNS
Rev. by J ADnestaerrcttsiocimlsihnaevraelbseoeilns,uantsteumccpetssstfoulis(o2l5a)t.eNanoaaenroabericobsiuclpbhaactteerrieadluocrearsrcfhroaemalR1o6sSs
u.
n rRNAgenesignalshavebeenobservedinextensivephylogeneticstudiesofDry
n
A
Valleymineralsoils(J.J.Smith,L.AhTow&D.A.Cowan,unpublishedresults).
Both cosmopolitan and indigenous fungal, yeast, and protozoan species have
been isolated from McMurdo Dry Valley mineral soils (Table 4). Filamentous
fungalcellcountsoflessthan200cfupergramofsoilwereobtainedfromRoss
Desert samples, the lowest reported counts for the various Antarctic soil envi-
ronments (25). Yeasts are relatively abundant in the surface horizons of certain
moistAntarcticsoils(4,26).ThepredominantalgaeisolatedfromAntarcticsoil
were the oscillatorioids, Microcoleus sp., Schizothrix spp., Anacystis spp., and
Coccochloris spp. Flagellated and amoeboid protozoa have also been isolated
from moist Antarctic soils (29). Thus while a few endemic microbial species
have been isolated (78, 102, 128), most bacteria isolated from Antarctic soil
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656 COWAN (cid:1) AHTOW
TABLE4 MicrobialspeciesisolatedfromAntarcticDryValleysoils(summarizedwith
permissionfromReference153)
Microorganism IndigenoustoAntarctica Cosmopolitangenera
Fungi Monodictysaustrina, Acremonium,Alternaria,
Chrysosporiumverrucosum, Aspergillus,Aureobasidium,
Acrodontiumantarcticum, Beauveria,Botrytis,Camposporium,
Chalaraantarctica,Phialophora Chrysosporium,Cladosporium,
dancoii,Thelebolusmicrosporus Epicoccum,Exophiala,Fusarium,
Geotrichum,Gymnascella,
org Helminthosporium,Hormoconis,
s. Myceliophthora,Nectria,Paecilomyces,
w
viey. Penicillium,Phialophora,Phoma,
ded from arjournals.annualre9/05/07. For personal use onl Yeasts CCCr..ylvupisptohi,cnoCiac.ccsiuio,scLicaeolunicss,oosrptioorniidsi,um TMRSTprraoiioctcrirohtroidoaetidcrruiheecmlirhlum,aumS,am,eM,,pVTuSeerctdriecotoiphrcnh,oiilauRplnimhhuoyi,mzstSoop,pnpoWo,urairsuormdtho,rmixy,ces,
a0
nloon
wY
DoT
0. RSI have been found to be cosmopolitan in distribution (Table 4). Bacteria isolated
58:649-69S UNIVE feMrroaicm:rAoMccohccrMocmuusor,dbPoalcaDtnerory,coAVcractluhlesryo,bPsasoceitulesdrom,mBooastnciaclsolu,msS,mtrCeopontrloyymnbeyebclaeocsn,tgearnituodmNth,oeFcalfaorvdlloioabwa(i2cnt3ge)r.giCuemno--,
4.N
00KI ryneformsarethemostabundantbacteriaisolatedfromDryValleysoils(85%of
2P
ol. HO whichwererepresentedbyCorynebacteriumsepedonicum)(23).
MicrobiOHNS thaIttthisew1%idetloy1a0c%cepotfemditchraotocruglatnuirsem-dsetpheantdceanntbmeedtheotedcsteadrebystrcounltgulrye-bdieapseedndaenndt
Rev. by J tiencdhenpieqnudeesnt(7te0c)hnairqeunesotsurcehpraessesnmtaatlilvseuboufnitth(essnua)turRraNlApogpeunleatsieoqnue(3n)c.eCanualtluyrseis-
u.
n andinsituhybridization(2,3)haveprovedtobeinvaluableinphylogeneticstudies
n
A
ofsoilmicrobiota(includingviable,nonviable,anddormantmicroorganisms).It
ishighlyrevealingthatsequencesretrievedfromenvironmentalclonelibrariesare
mostoftennotrepresentedbyanycultivatedorganisms(156).
Althoughtherehavebeennumerousphylogeneticsurveysofmicrobialspecies
presentinvarioustemperateandtropicalsoils(86,92,109),fewpublisheddata
yetexistfromphylogeneticstudiesofAntarcticDryValleymineralsoilcommu-
nities. Phylogenetic analysis of DNA extracts from mineral soils collected from
theslopesoftheMiersValley(RossDesert)indicatedthatasmanyas50%ofthe
retrievedsequencesarefromunculturedbacteria(J.J.Smith,L.AhTow&D.A.
Cowan, unpublished data). Most of the remaining sequences are from bacteria
31Aug2004 11:56 AR AR224-MI58-24.tex AR224-MI58-24.sgm LaTeX2e(2002/01/18) P1:IKH
ENDANGEREDANTARCTICENVIRONMENTS 657
belongingtotheActinobacteria(27%),Bacteroidetes(11%),Acidobacteria(6%),
and Verrucomicrobia (6%). In a separate phylogenetic study performed on min-
eralsoilcollectedfromheavilyimpactedgravelsfromMcMurdostation,bacteria
wereidentifiedasbelongingtothefollowingphylogeneticgroups:Actinobacte-
ria(12.5%),Bacteroidetes(25%),Firmicutes(12.5%),Planctomycetes(12.5%),
andProteobacteria(37.5%)(E.M.Kuhn&D.A.Cowan,unpublisheddata).The
observation that a high percentage of bacteria inhabiting Antarctic mineral soils
has not been assigned to a phylogenetic group, let alone identified at the genus
level, is entirely consistent with phylogenetic data from many other microbial
biotopes.
g
or
s.
w
e
viy. SensitivitytoEnvironmentalImpacts
als.annualreonal use onl TofhheuDmryanVianllteeyrvseanntdioonthoefraicleit-tflreeoevreergiaocnesnotfutrhye.TAhnetacrocmticbcinoanttiionnenotfhgaevoegarahpishtiocrayl
ded from arjourn9/05/07. For pers imfotshufoaerptlnshaeateirimfrtoainccpcoutaaonlcnarttdsrrslo,ymelblneesuveadtinnrlbossiytintttlihmtvehaeeetangametraaxeuilinacsessthxetatnogrscfeleomSthboieetafeslisipcnoeortroe-ffrrvreSniegdapeiteeoislconainsnaaoaldlmlcSatlercriemeipeaarantoiotteitifcsefitccachtnhieIodanAnntbegnayretgea.tashrTtice.nthsiTdcetehdcfseoiiorgrsnemnuctaimtenthrieouonins-ft
a0
nloon canstillberegardedaspristine.
DowTY However, our fascination with this continent results in a continued increase
0. RSI inhumanactivities(research,exploration,tourism)onthecontinent.Theimpact
58:649-69S UNIVE os(sifzuetchahebsaleesttahocwetiTvnaist,yiefiloserlidsVarbelylseenya,ortchmheecWaonnrsicgehhnottmrVaoategllseenoye,noaaunsdr:eMlRataeirsvseeaOlyrcalhsiimsb)ia,tseaednsdnnucoumwrbreecnrotnotsfotisutirutietsest
4.N
00KI activityislocalizedtositesofinterestsuchaspenguincoloniesandhistorichut
2P
ol. HO sites.Alltheseactivitiesimposephysical,chemical,andbiologicalburdensonthe
MicrobiOHNS locPaloesnsivbilryonthmeenmto(ssteedaTmabalgein1g).effects resulting from increases in human activ-
Rev. by J iatbyrainsiothne,cicoem-fpreaectiaornea,stroamf Aplnintagr,catincdadarisetufrrobmancpehyosficsoalils(i)natnhdecfhoermmicoaflp(hfoyrsiecxa-l
u.
n ample, eutrification, fuels spills, chemical debris) impacts. Physical disturbance
n
A
ofthemineralsoilsleadtosomedisruptionofstratifiedmicrobialcommunities.
Inaddition,themovementofindividualsfromoneareatoanotherresultsincross-
contamination of microorganisms between niches. Such impacts tend to invali-
datephylogeneticstudiesperformedonso-calledpristineenvironments.Thereis
alsoanincreasedriskofcontaminationatthemacroscopiclevel,forexample,by
fuel-spill contamination (48). Although typically localized, such gross contami-
nationisexpectedtohaveadramaticanddisruptiveeffectontheextantmicrobial
community.
Colddesertsoils,oncethoughttobesterile,arenowknowntobeinhabitedby
a wide variety of microorganisms (55). Many of these microbial species appear
31Aug2004 11:56 AR AR224-MI58-24.tex AR224-MI58-24.sgm LaTeX2e(2002/01/18) P1:IKH
658 COWAN (cid:1) AHTOW
to belong to cosmopolitan taxa (153), although some are apparently endemic.
Natural vectors aid the dissemination of microbes into and within the Antarctic
continent (151). These include atmospheric circulation, oceanic circulation, and
migratorymammals,birds,andfish,allofwhichcontributedirectlyorindirectlyto
theintroductionofnonindigenousmicroorganisms.Giventhatnaturalprocesses
continuously seed nonindigenous microorganisms into the Antarctic continent,
researchers might argue that additional dissemination of bacteria from human
activitiesisoflittlesignificance.
Thathumanactivitiesdocontributenonindigenousmicroorganismstothelocal
environmenthasbeenclearlyestablishedbyanumberofrecentstudiesthatshow
g
or contaminationbyhumancommensalandfecalmicroorganismsofmineralsoilsand
s.
w aquaticsystemsinthevicinityofpermanentbasesandtemporarycamps(5,19,20,
e
ualrevie only. 4h9ar,s9h7e,n1v3ir2o,n1m43e)n.taRlecgoanrddilteisosnsifinthAenhtuamrcatinc-ad,ethrievseedrecsounlttasmshinoaunldtsbceacnosnusrivdievreedthine
als.annonal us tohregacnoinstmexs.tNofalkaetdermalicgreonbeiatrlaDnsNfAers(uLrGviTv)esbefotwrleoenngnpoenriinoddisgiennDoursyaVnadllienydsiogielnso(uLs.
ded from arjourn9/05/07. For pers AecTnaohnvdiToraooctenwc,umtr&heoenvrDteei.rsiAslaa.nrrCogeeoldawgitrieaevonceg,tlyreuavncpiophdmuiecbnmldcieiosshnfteaoednrvcLereenGsstuoT(lw5tis0ni)n,.tg7hL1etGo,A8Tpn4atb)ra.teirEtccwuvtiliecadeteenenndvbciieasrcopsthneeromrsiwaaelsni(ntt7,h1ntah,ote1rL5siGs1oT)iilt.
wnloaY on 0 ctoleAarnwtahrcettihcemrsiuccrohbaiaplrococemsmswunoiutiledsb.erelevant,advantageous,ordisadvantageous
690. DoERSIT AnRtaercgtiiocneanlvoirrognlmobenaltsc.lIinmtearteestcihnagnlyg,ethheahsotlheeinpothteenStioaulthtoPdorlaarmoaztoicnaelllyayiemrpaancdt
49-NIV itsassociatedincreaseinincidentUVradiationmaynothaveadirectimpacton
58:6S U DryValleymineralsoilcommunities,whicharethoughttoavoidtheexposedupper
4.N surfacesofmineralparticles.However,thedependenceofmineralsoilcommuni-
00KI
2P tiesonlacustrine-derivedorganicmaterialasakeysourceofCorNsuggeststhat
Microbiol. OHNS HO sareerggcuioomnndeaanlrtytsememfpfaeeycrtaastlusfroreobmreegcaihmpapenlsige.edAstionnealtarkcaoenogpliernogodfuocofttihEveiatrsytcemlrinmigAahttnictbaecrchitamincpagoedrstu,arininntc.glTusdhuiemnsge-
Rev. by J merandautumnperiodsbetween1966and2000(47)appearstocoincidewitha
u. warmingofthewesternsideoftheAntarcticPeninsula,especiallyinwinter(1951
n
An to2000)(141),withanincreaseof1.09◦Cperdecadeduringwinterand0.56◦C
per decade annually. Such regional differences suggest that it may be impossi-
ble (and unwise) to assume any continent-wide climate changes. Nevertheless,
temperatureincreasesinice-freeareasareexpectedtoincreasetheavailabilityof
liquid water (from glacial and permafrost melting, and possibly from precipita-
tion),withpossiblydramaticchangesinmicrobialbiomass,microbialproductiv-
ity,andcommunitystructure.RossDesertsoilssubjectedtotemperaturesabove
0◦Cshowlargeincreasesinculturablebacteria(11),whiletheenclosureofDry
Valley desiccated mineral soils under transparent plastic cloches resulted in the
rapidgrowthofmossandcyanobacterialconsortia(D.D.Wynn-Williams,personal
communication).