3.3 The Chemical Characteristics of Antarctic Lakes and Ponds, with Special Emphasis on the

Polarforschung58 (2/3):2/9-230.1988

3.3 The Chemical Characteristics of Antarctic Lakes and Ponds, with Special Emphasis on the

Distribution of Nutrients

ByTetsuya Torii'", Genki1.Matsumoto"" and ShyuNakaya" ,.,.

SUIllI1Uln: Thix rcvicws Japancsc lirnnolcgical studics muinly in rhc Mclvlurdo and wi111 spccial cmphasis011rhc nutricnt distributic"m. thc chcmical composition of thc major ionic componcnts in the coastal is similar10that in seawatcr.whilcthat in inlandDrv und ponds of thc Mcfvlurdo Onsisisabundant in culcium. ions. Thc Former can bc e.xplaincdhythc

direct influc;1CcS whilcthc lauerismainlvauributablcLOthenccumulationor;.::::;:),::(~~~C(',:C"~~~~;a'lll",,cd.

j'vlost saline lakcs arc meromictic. Dissolvcd . rc but thc houom arc anoxic

and ollen hvdrcuen sulfidc occurs. Thc 01' nutricrus but also wirb dcpth. whichis

al;und(ul{ in all frcshwater and sal iuc lukcs. mav bc duc of sei Is and rocks. conccntrutions in bcthfrcshwatcrand salinc 10\\'. Nitrate-Nconccnuutionsinthc oxiclavcrs of thc inland salinc lakcs in thc McMurdo Oasis arc oftcn high. but not high in thc coastal 01'rhcSyowaand Vestfold oascs. Thc ahu;lclancc01'phosphntc-P und ammoniurn-N in thc bottomstagnanl~-Iayers01'saline lnkcs can hc cxplaincd by thc accumulation of microbiully rclcascd nutricntsduc10thc 01'organic substanccs. Nuuicnts arc xupplicd rnainly from mchstrcams in thc catchment arcas. and arc provcd to play an important rolc in producnon.

Zusammenfassung:Eine iiberjnpanischclimnologische Studien in den eisfreien Gebieten derMcMurdoDry und derSyowa-Oasc im Hinblick auf die wird Im alleemeinen ähnelt die loncnzusanuncnsctzuua in küstennahen der des Seewassers. währendKalzium. Sulfationenin dncGewässern des Binnenlandesange~"Cicherlsind. Ersteresberuht auf dem

unmiuclbarcnEinfluß des Ozeans. aufAkkumulationvon Salz: durchVerdunstuno. ~

Die meisten Seen sind In oberflüchennahen Schichten die Suucrstolfkonzcntration im Sattiauuusbcrcich oderdarüber.während in bodennahen Schichten Sauerstoffarmut herrscht lind vorkommt. variiere;l nicht nur in den einzelnen Seen sondern auch mit der Sectiefe. Silikat-Si ist in allen Seen reichlich vorhanden und stammt von der von Gestein und Böden. Nitrat-N kommt allgemein nur in niedrigen Konzentrationen vor. Nitrat-x-Konzentrationen sind in den saucrstoffhaltigen Schichten der Seen in den McMurdo Dry Vallcys hoch. doch nicht in den Salzseen bei und in den Vestfold Hills. Die von Phosphat-P und Ammonium-N in den ruhigen

tiefen Schichten von Salzseen sind wohl Anhaufuna mikrobiell Material zunickzuführen.

Nährstoffe wcdcn vor allem von Schmelzwasserströmendes der Gewässer eingetragen eine bedeutende Rolle für die Primärproduktion.

I. INTRODUCTION

There are a large number of ice-free areas, so-called oases, in and areund the eoastal regions of Antarctica(Fig, I). Many lakes and ponds, fed by loeal snow and glacial meltwarers, are locateel in depressions in ice-free regions

01'in drainage basins encloseel by glaciers. Since thc International Geophysical Year(1957-58),many investi- gators of the SCAR nations have studicd lakes and ponels in thc oases and other ice-free regions from the li1l1nological and geoebemical points ofview. These studies have revealed interesting physicoehe1l1ieal properties of lake waters. such as unusual temperature profiles, origin and evolutional processes of lake itself, and of the major ionie components and trace metals, features of organic constituents that accOlll1t for the absence of vasenlar plants, ami unique microbial communities in harsh environments. This paper reviews mainly Japanese Iimnolo- gical stuelies on physical, chemical and some biological features in lakes and ponels of the McMurdo Oasis (McMurelo Dry Valleys01'Ross Desert) ami Syowa Oasis in Antmctica, with special emphasis on the distribution of nutrients in relation to their sources, controlling factors and photosynthetic activity (Figs. I am! 2).

2. GENERAL CHARACTERISTICS OF ANTARCTIC LAKES AND PONDS

Lakes and ponels in the oases are distributeel usually at altitudes between--60m below sea level and1450111above sea level. Saline pond at the IÜghest elevation (1450m) was found at the foot of Mount Bastian of the upper Victoria Valley in the McMurdo Oasis (MURAYAMA et al.1983).Generally, saline lakes in the coastal regions

Pror. Dr. Tetsuya Torii, Japan PoInt" Research Association, Kojimachi1-8-7.Chiyocla-Ku. 102.Japan.

Dr.Genki1.i\·Iatsumo!o. Deparlment01'Chemistry. The College01'Arts and Seiences,The of Tokyo, Komaba3-8-1 lvleguro-Ku.Tok)'o 153.Japan.

Dr. Shyu Nakaya. Department01'Earlh Sciences. Facul!y of Seience, Hirosaki Uni\'crsit)!, Bunkyo-eho 3. Hirosaki. AOl11ori Prefecture 036, Japan.

180°

MeMurdo Oasis

/

Antaret rc

/ .

Peninsula

\ ~.."

Syowa Oasis

0°

Home Lake Lake

V~LEY

50i km 162°E

Nort h Fork .. ~

-, Lake Vanda

«-,.;,.e

~-\

"'. \ Onyx ..:,.,?-vv -{ .

" WRIGrrr t>-\.-\.-~

/ Lake Canopus O'?---J~ ^. Juan Pond t>--{\.-.'r,"

Lake

Joyee~

"""'" LI k C d:

\ . ~ae ha<

Lake Bonney

o

i B-I

Don 77"00'S

Fig. I:Lakc-, und pond-,IIIthc Mcivhudo Oa"Js of sourhcrn Victoria LandIIIAntarcuca . • :O'lSCS.

are founel below sea level. while those in the inlanel Dry Valley regions ofthe MeMurelo Oasis are situated above sea leveL Lakes ancl ponels in the oases contain a large vuriety of elissolveel salts in chlorinity ranging from ne ar snow meltwater to 13 ti rnes higher than that of seawater. In gcneral, inlanel Dry Valley 1akes are covered with thiek ice throughout the year, anel thus not influeneeel with wind-induccd turbulance, although sorne coastal saline lakes anel small ponds often melt completely eluring the austral surnmer. However, hypersaline Don Juan Panel in the McMurelo Oasis and Deep Lake in the Vestfolel Oasis are often fre of ice cover throughout the year. Usually saline lakes have no outlets ancl the lake lcvels arc balanced between the supply of snow and glacial mcltwaters and the evaporation of lake waters.

The stable isotopic ratlos ofhydrogen ancl oxagen for the coastal and inland freshwater lakes anel ponds are similar to those for local snow and glacial meltwaters, anel fit with the metoric water relationship line (MATSUBAYA et al, 1979, TORII et al. 1988). They indicate that these water bodies are direetly supplieel from loeal snow anel glaeial meltwaters, However, the stable isotopie ratios for some saline lakes ancl panels arc dcviated from the meteoric water relationship line elue to the isotopie fractionation eluring the fractional freezing or evaporation of lake anel panel waters.

Most saline lakes are merornictic. Thus physical, chemical ancl biologieal properties in the warer column differ rernarkably not only among the lakes but also with elcpth. For instance, the water temperature in Lake Vanela of the McMurelo Oasis rises stepwise with inereasing depth and reaches the maximum of about 25" ein the botrom layer (Fig. 3). YUSA (1975) interpreted this unusually high water terneprature baseel on a simple ancl quasisteaely thermal model, The moelelleaels to a possible eonclusion that water tcmperatures up to 25" C ean be attributed to solar heating. Also the water temperarure in Lake Nururne of the Syowa Oasis has two max ima at elepths of 3.5 anel 12 m (SANO et al. 1977). In general, the heat source of high water temperatures in the meromictic lakes is believeel to be the penetrating solar energy. The elissolveel oxygen in the upper layers is usually saturateel01' super-saturated but the bottom layers are anox ic, anel often hyelrogen sulfide oeeurs (e. g. Fig. 3). In some cases.

elissolveel oxygen eoneentrations are extremely high, over 4 times higher than the saturation (e. g. TORII et aI.

1975, MATSUMOTO et aI. 1982, 1985, WHARTON et al, 1987). For the high elissolveel oxygen concerurarions,

10km

1

40^{0 0 0 ' E}

5

Lake Midori

o

I

. _,

I-(f)

'" ^«

r..~ ⁰

u 69° 15'8

«

>-

LÜTZOW-HOLM

BAY

¹⁰(f)

."

Lake

39°00'E 69°30'8

Lake 69°00'8

Fig. 2: Lukcs and pondsinthc SYO\,.(lO;lSIS01"Endcrby Land. Antarcuca.

WHARTON et al, (1987) suggesteel that this super-saturation resulteel from the exclusion01'oxygen e1uringthe freezing01'aeratedmeltstreamwater at the bottom01'the iee cover. pH values01'lake waters in the oxie layers showed neutral or alkaline, but those01'the anoxie layers inelieateel sometimes acielie.

More than 60 small freshwater and saline ponels are distributcd in high elevteel areas01'600-1000 m above sea level, viz., in the Labyrinth01'the uppcr Wright Valley01'the MeMurelo Oasis. High eoneenrrations01'e1issolvecl oxygen, logether with high pH values(>10) were observeel in certain ponels in the Labyrinth (MATSUMOTO et al. 1985, TORII et al. 1988). This can be explainecl by the intensive photosynthesis since extensive cyanobacterial mats were observed at the ponel eclges.

Fig.J:Vcrtical distrilnuion ofin Lake Vanda of thc~,P'i~~;~~'~~~:,',~~

fromNAKAIctal.(1975).

°

. : oxyqen

Bottom

j y

, j \

pH

I

I

^I

• : i i \ \

I \ _~

I 1..,\ \

I I \

I

^I

I I \

• \ j\ i

Tempereture

:

\ . I

\ I .

\ \ !

0/

\\Chl_{\ or lm ty}. . \.

_\! !

I ~

0,

.--... ^/

^'--.

^--"--. -,

--... Y ..., 0

< ,. •, . .

0'>-<::::'"

~...,...

cf

I

'--.,

...

__---=-,,0%-"--.:::.,0

^<,

° ' 0 . . . . "

I- r

^S2.::-·

^Ö

<, --... \\

t ^Y

Temperature/OC

0 5 10 15 20 25

I I I I I I

pH, Dissolved oxygen/ml-I-^I

0 5 10 15 20

I ^{I I} I I

Chlori nity

Ig-

kg-I ,S2-/mg-I-^I

*

0 20 40 60 80 100

I I I I I I

0

10

3

5 20

60

<,

E

s:

-

^Co

~

40

3. MAJOR IONIC COMPONENTS AND TRACE METALS

The composition of the major ionic components in freshwater lakes and ponds in both the coastal and inland Dry Valley regions is generallysirnilarto that of loeal snow and glacial meltwaters in the catchment areas (Tab. I, Fig. 4). Most saline lakes and ponds are of chloride-type, meromictie und are chemically stratified, having a layer of freshwater underneath an ice cover and the deeper water increasing in salinity with depth (e. g. Fig. 3). The composition of the major ionic components of the saline lakes and ponds in the coastal regions is similar to that of seawater, while that of the inland Dry Valley saline lakes and ponds is markedly different among the lakes and ponds, although these lakes are gene rally abundant in calcium, magnesium and sulfate ions (Tab. 2 and 3. Fig.

4). Equivalent percentages of calcium ions in total cations (sodium, potassium, calcium and magnesium ions) for DonJuan Pond ancl Lake Vanda are 97 and 58%,respectively. Those of magnesium ions for the east lobe of Lake Bonney ancl L-I Pond (unnamed pond in the Labyrinth) are approximately 40% (TORI!&YAMAGATA 1981).

Torii and his coworkers (TORI!&YAMAGATA 1981, TORI! et al. 1981, 1988) explained the fonnation of these unusual dissolved salts as follows: Freshwaters originated from local snow and glacial meltwatcrs are concentra- ted in lakes and ponds by freezing ancl evaporation of watcrs, accompaniedbythe fractionation of dissolved salts

Sampie Na K Ca Mg CI SO, Rcfcrcnccs McMurdo Oasis

Lake Brownworth 3.85 0.47 1.90 0.6 4.9 6.2 TORlictal.( 1975)

Lake Canopus 35.9 2.01 4.10 5.8 44.0 38.0 ibid.

L-12 Pond" 60.3 1.3 25.8 17.5 78.3 99.6 TOR!!ctal. (1987)

L-20 Pond" 42.5 1.3 4.5 10.0 93.6 15.0 ihid.

NF-IPond"" 17.0 0.6.') 4.4 6.4 16.1 13.8 TORIlet al. ( 1975)

NF-2 PomV* 20.0 0.66 5.7 7.2 18.5 15.2 ibid.

Syowa Oasis

LakeMidori 8.5 0.2 3.2 1.7 17.3 6.8 MUR;\YA:-'lA(1977)

Lake O-ike 60 3.0 5.9 9.6 120 12 ibid.

Lake Skallcn Oike 48 3.4 9.4 9.5 85 10 ibiel.

Tab. 1: Chcmical composition of Frcshwatcr lakcs and ponds (mgkg""). "" Unnamcd ponds in the Labyrinth. Unnamcd ponds in thc North Fork.

Ca

Na+K (in equlvclent •

%)

Mg

Fig. 4: Triangular diagram showiug major cation composition of the bouom watcrx of lakcs and ponds in the McMurdo. Syowa and Vestfold oases.

G: Glacial mcltwater. S:Snow.A: Seawater; 0 and .: Coastal frcshwater nnd saline lakes and ponds, rcspcctively, 0 ande:Inland freshwatcr and saline lakes and ponds. respectively.

under frigid conditions, as delineated by THOMPSON&NELSON (1956).

MASUDA et al. (1982, 1984) analyzed trace metals, Al, Co, Cl', Cs, Cu, Fe, Mn, Ni, Rb, Sb, Sr, Th and Zn, in the water samples from Lakes Canopus, Fryxell ancl Vanda, Don Juan Pond, L-4 Pond (unnamed pond in the Labyrinth), Onyx River and glacier ice. Three possible origins of these metals. i.e. connate seawater, rock weathering and tropospheric aerosol particles, were investigated. The correlations of trace metals between tropospheric aerosol particles and lake and pond waters indicate that the trace metals in the Dry Valley lakes ancl ponds may have been derived from tropospheric aerosol particles. For Lake Vanda they concluded the pathway

Syowa Oasis Vestfold Oasis

Lake Lake Lake Lake Lake Ace Decp Oval

Hunazokc Nururne Oyayubi Suribali Zakuro Lake Lake Lake

Sampling datc 10/06/67 10/12/69 10/05/72 11/11/72 10/06/72 11/29/74 12/02/74 04/30/74

Lakelevel (m) -25 -0.5 0 -33 -6 7.6 -56 -27

Maximumdepth(m) 9.3 16.6 5.2 31.2 4.6 21 36

Sampling depth (m) 2.5 15 5.0 30.0 4.1 15 30 0

Tcmpcraturc ( C) -15.7 9.4 -6.0 -5.5 -15.0 13.0 -9.0

pl-l 7.26 6.80 7.2 7.1 7.1 7.44 7.63

Spccific grnvity 1.146 1.040 1.070 1.141 1.142 1.022 1.175 1.105

(1Y C) (2YCI (2WC) (20· C) (20' C) (2WC) (20' Cl (20' C)

Na 58.2 IS.l 34.0 69.0 60.0 10.2 59.1 44.9

K 2.4 0.66 1.2 2.5 2.5 0.36 3.95 0.79

Ca 2.22 0.77 1.1 1.2 2.5 0.24 2.19 1.91

Mg 7.87 2.00 3.5 8.5 8.4 1..11 12.2 5.52

CI 116.6 29.90 53.0 130 130 18.04 137.4 80.43

SO, 2.47 3.81 83 8.1 4.0 0.85 2.50 2.36

0"0 (~h:) -9.9 -29 -4.2 -10.9 -11.0 -173 -12.7 -14.2

(7 m) (16 m) (17 m I (34m)

oD

^{(~{o) -137 -83 -74 -146 -137 ·-145 -141 -141}

(7 m) (16m) (17m) (34m)

Rcfcrnccs" b

Tab. 2: Chemical composition of salinc lnkes in the coastal region. "a:TORli(19B6). b:ivkRAY.,\~IA(1977).

ß~IPond Lake Bonny Don Junn Lake Lake Labyrimth Lake

(unnamcd) cast lobe west lobe Pond Fryxell JoyeeL-1 pond Vanda

(unnnmcd)

Sampling datc 12/21/82 01/04/72 01/09/72 01/06/65 12/20/72 12/18/76 01/03/77 12/09/72

Lake levcl (m) 1450 56 56 122 12 330 930 93.6

Maximum depth (m) 33.4 .10.2 0.1 18 34.8 4 68.5

Sampling dcpth (m} 0.5 32.5 29.5 surfacc 16 30.4 0.15 64.6

Tcmpcrature ("C) -0.2 ~2.4 -4.6 10.4 1.6 -0.1 4.0 24.3

pl-l 8.32 6.51 5.73 4.6 7.(J7 6.59 7.54 5.45

Spcc. grafity (25' C) 1.034 1.203 1.102 1.386 1.00 1.00 J.(J17 1.092

Na 9.96 56.9 32.1 1.63 2.98 1.06 4.13 6.11

K OllS2 2.30 1.47 0.26 0.203 0.07 0.025 0.59

Ca 1.07 1.22 1.48 137 0.027 0.25 0.531 24.4

rvlg 5.86 21.7 8.34 1.80 0.331 0.14 1.92 7.40

CI 17.1 162 78.1 251 3.71 1.45 7..\8 74.3

SO, 1.90 2.94 4.45 0.00 0.253 1.08 2.13 0.615

0"0 (Sfd --25.3 -25.2 ·-40.5 -\3.9 .. 31.8 -12.7 -29.7

(64 m)

so

^{«(;(-e-) -225 -252 -318 -186 -254 -174}

m)

Rcfcrenccs'" b

Tab. 3: Chcmical composiuon01'saline lakes in thc Dry Vallcy region. "a:TORliel al. (1987). b:TORI!et al. (1975). c:TORJIet al. (1977). d:TOR!I

(1986).

of these trace metals as follows: Tropospheric aerosol particles - precipitation - glacier - glacial meltwater - Lake Vanda. This result supports a view that the dissolvcd salts in the Dry Valley lakes were derived from atmospheric salts.

4. NUTRIENTS 4.1 Distribution

Many investigators have studied nutrients, i. e. silicate-Si, phosphate-P, nitrate-N, nitrite-N and ammoniurn-N, in lake and pond waters in the three geographie al regions, McMurdo, Syowa and Vestfold oases. Nutrient concentrations vary largely among the lakes and ponds, although they also differ considerably by investigators (e. g. FORTNER et at. 1976). Especially, earlier researches for hypersaline water samples are generally underestimated. Table 4 surnmarizes some selected nutrient concentrations for freshwater and saline lakes and ponds in the three regions. Also examples of vertical nutrient distributions in an inland meromictic Lake Vanda and a coasral meromictic Lake Suribati are shown in Figures 5 and 6, respectively.

S i 1i c a t e - The silicate-Si concentrations in Lakes Fryxell, Joyce and Vanda in the McMurdo Oasis rise with

Lake or pond

Dcpth (m)

SiO,~Si (~lg~,tt'll)

PO,~P

(llg-al·l·^l)

NO,-N (,Ug-at.l·i)

NO,-N (,Ug-,tt'I-^I)

NH.-N

(.ug-~t.l·l) Lake'>" Referenccs type

---~.._ - - _.._-~...._ _..

1.60-430 HS FORTMoRetal,(1976) O~I170 HS WE,\;-';D et a1.(1977)

2-58 HS MxrSU~!()TüETnl. (1982)

O~190 HS ibid.

1.32 F '1'ORII et al . (1975) OA90 F PAJ~KER&SI~!~!O?\S(1985) ND-293 S TORI! clal.(1975) 0.10~·>7 S PARf.:ER&SI~l~lO?\S<.1985) OJ)~800 S TORliet al.(unpubl.)

0~>7 F PARf.:ER&Sl~lO\S(1985)

36 S MATSU,\IOTO etal.(1982)

O~OO S ibid.

ND F TORIleral.(1975)

NR F ibid.

NR F ibid.

0.81 S ibid.

ND F ibid.

O.I~1747 HS VI\TE?\Tctal.(19R I) 0~2200 HS M.·\TSL\IOTO etal.(1985) O~1700 HS TC)Rl1ctal (unpubl.)

1.7~6.0 HS Fuxur ctal./1985)

0~2420 S ibid.

O~O.I F ibid.

0~0.3 F ibid.

0-575 IIS ibid.

ND S lh?\D&HURTe)\; (19R1) 49.3 S BARf.:ER&BCRTO?\ (unpubl.)

NR HS KERRY Clal.(!977'1

O.OI~1.3 OAI-42.4 0-44.6 0.25--40 (J.OI~0.37

0.60

(J.2.~0.5 (J.0~0.3

0.0

0.0~O.2 O.O~O.I

3.1

O.O~0.55 2.68 2.70 4.33 20.0 15.0

<O.I~1.90 O.04~O.70

0.l1-0.78

ND ND

0.093~0.36

0.35#

0~0.32#

0.0~0.60 0···3.53#

<I ND

1.0~1.9

<0.1~1.8

dU

<0.1

o

4.5-156

6.4~246

16-210

0.0~24A

51

ND ND

3.8~6.2

5.6 0.8-570

107 129 455 24800

535

<1.0~233

2.80--153

<1-270

0.25-0.45 0.04~150

0.01~0.11

0.04

0.05~68.1

3.2 326.0

<0.03·IA8 O.0761~6.61

<0.003-3.29 0.0

0.0~0.7

0.17 NR 0.02~50.2

O.042-1.281?

0.24-77

0.0250~0.126

190

0.0~3.2

0.17 NR NR ND NR

<0.01--B.15 0.0--10.2

O.O~II NR

NR 6.5-220

47~250

18.7 NR 14-175

NR 64~650

NR 240

39~500

73.5 65.0 73.5 458 25.2 NR

176~714 180~1200 5A~30A

surfacc surfacc surfacc surfacc surfucc

3.25~67.5

).1-68.6 5.0-69.5

4~26 4~25 5.4-33.4 5.4-30.2 NR Various dcptbs

4·~16 Various dcpths

5.0~18.5

Various depths surfacc I\1CMlII"doOusis

Lake Bonne)' cnst lobe ibid.

ibid.

LakeBonncywcstlobe LakeConopus Lake Chnd LakeFryxell

ibid.

ibid.

Lake Hoarc HorneLake Lake Joyce NF-l Pond"

NF-2 Pond"

NF-3 Pond'<

NF-4Pond~

NF-5 Pond"

Lake Vanda ibid.

ibid.

1.15 12.4 0.19 NR EL-SAYED(1970)

BURTO\(19RI)

Tab. 4: Ranges of nutricnr concentrations in Antarctic lakes and ponds. Unnamed ponds inthe NorthFcrkofWrightVallcy.8'''F:Frcshwatcr.S: Saline. HS:

Hypersaline. # Nitrate+nilrite.NR: Not rcportccl. ND:Not dctcctcd.

SYO\1'OOasis

LakeHunuzoko 0~7 155-227

LakeNururne 0-15 4-426

Lake O-ike O~7.5 23

Lake Skal1cnOikc O~8 88~93

Lake Suribati 0-29 105~244

Vestfold Oosis

Ace Lake 5.0 95

ibid. 22.0 NR

Decp Lake 0~34 99.9-163

S'('{[\l'OfCrFOIll

Antarctic OC('{l/I NR 21.3

increasing depth anel attain themaxiraumvalues of 650,500 anel 1200 !lg-at/l, respectively in the bottom layers (TORI! et al. 1975, NAKAYA et al. 1977, MATSUMOTO et al. 1982, 1985, TORII et al. unpubl. results). These profiles are also founel in Lakes Nurume, Hunazoko anel Suribati in the Syowa Oasis (TOMINAGA & FUKUI 1981, FUKUI et al. 1985). However, those in the east anel west lobes of Lake Bonney have the maximum values of 220 anel 250 ug-at/! in the mielelle layers, 15.4 anel 13.4 m, respectively (MATSUMOTO et al. 1982). Further.

high silicate-Si concentrations were found in waters from a meromictic Ace Lake (HAND & BURTON 1981) anel a hypersaline Deep Lake (KERRY et al. 1977) of the Vestfolel Oasis, Generally. silicate-Si coneentrations in freshwater lakes and ponels are similar to those in seawater from the Antarctic Ocean, but those in saline lakes are much higher. Extremely high silicate-Si values were founel in the bottom waters of Lakes Vanelaanel Fryxell.

P h0s p h0r0u s - Phophate-P concentrations in freshwater lakes are generally consielerably low anel similar to those in the oxic layers of merornictic Lakes Bonney, Fryxell. Joyce and Vanda in the McMurelo Oasis (TORI!

et al. 1975, FORTNER et al. 1976, HOEHN et al. 1977, NAKAYA et al, 1977, WEAND et al. 1977, VINCENT et al. 1981, MATSUMOTO et al. 1982, 1985), anelLakes Nurume anelSuribati in the Syowa Oasis(MURAYAMA et al 1981, 1984, TOMINAGA & FUKUI 1981, FUKUI et al. 1985, Tab. 4). In these meromictic lakes, phosphate-P concentrations increaseel with elepth anel reacheel the max imum values in the bottom layers. The extremely high phosphate-P concentrations were founel in the bottom waters of Ace Lake (326 ug-at/l , BURTON 1981), Lake Nururne (156 ug-at/], TOMINAGA& FUKUI 1981, FUKUI et al. 1985) and Home Lake (190 g-at/l, MATSUMOTO et al. 1982). Phosphate-P concentrations in the water column of the east lobe of Lake Bonney showeel seasonal variation in the 1973-75 austral sumrners (HOEHN et al. 1977, WEAND et al. 1977). They suggested that these variations are attributable to the supply of subsurface water.

WEAND et al. (1977) reporteel consielerable amounts of conelenseel (acid hyelrolyzable) phosphate in the mixolimnion of Lake Bonney. The concentrations are ab out 3 times higher than those of phosphate-P, This may be interesting in relation to primary proeluctivity limitation.

300

I

250

I

50

o

I

P04-P/~g-at·I-I. N02-N/~g-at·I-I (X 10- 1 )

o

^{2 4 6 8 10 12}

I I I I I I

NO~-N/~g-at'I-1

100 150 200

I ! !

o o

NH4-N/~g-at'I-1 •Si02-Si/~g-at'I-1

300 600 900 1200 1500

I !

lee

1800

I

10

20

30

<,E s:

g.

⁴⁰

o

50

60

70 Fig. 5: Vcrtical distribution of nutrientsin Lake

Vanda of the McMurdo Oasis.

I no r g a ni c n i t r 0 g e11 C0 m p 0LIneIs - Nitrate-N. nitrite-N anel ammonium-N concentrations in freshwater lakes anel ponels are generally considerably lower than those in saline lakes. Nitrite-N coneentrations in both freshwater and saline lakes from the three oases were generally low, bnt relatively higher nitrite-N coneentrations (31-40Ilg-at/l)^werefound between depths of 25.4 and 33.4 m in the east lobe of Lake Bonney (MATSUMOTO et al. 1982).

In the oxic layers ofLakes Bonney, Joyce and Vanda, considerably high concentrations ofnitrate-N were detected, but those in Lake Fryxell were near zero (TORII et al, 1975, unpubl,results,NAKAYA et al. 1977, MATSUMO- TO et al. 1982, 1985). The 10w nitrate-N and nitrite-N concentrations were also found in freshwater lakes, Öike and Skallen Öike as weil as saline lakes, Lakes Hunazoko, Nururne and Suribati in the Syowa Oasis (MURAYA- MAetal. 1981, 1984, TOMINAGA&FUKUI, 1981, FUKUIetal,1985), and Aee and Deep Lakes in the Vestfold Oasis (KERRY et al. 1977, HAND& BURTON 1981). These lakes are all located near the coast and consielered to have the character of coastallakes.

Amrnonium-Nwas largely concentrated in the anoxie layers of the meromictic lakes. Ammonium-N concentra- tions in the bot tom waters of Lakes Fryxell and Vanda of the McMurelo Oasis (TORII et al. 1975, NAKAYA et al. 1977, WEAND et al, 1977, VINCENTet aL 1981, MATSUMOTO et aL 1982, 1985) and Lakes Hunazoko, Nururne and Suribati (TOMINAGA&FUKUI, 1981, FUKUI et al, 1985) exceed 200Ilg-at/1.The extremely high arnmoniurn-Neoncentrationsweredetected in the bottom waters of LakesNururne(2420ug-at/l)and Vanda (2200 ug-at/l). HOEHN et a1. (1977) and WEAND et al. (1977) observed that nitrate-N, nitrite-N and arnmoni- um-N concentrations in the water eolumn ofthe east lobe ofLake Bonney varied significantly with sampling date

N02-N/~g-ot'I-1 , N0₃ -N/~g-ot'I-1

0 1 2

I

o

10

I

P04-P/~g-ot'I-1

20 30 40 50 60

I

70

I

80

NH4-N/~g-ot'I-1 , Si02-Si/~g-ot'I-1

o

100 200 300 400 500 600

I I I

0:

_{N0 2-N}

0: NH4 - N

\7: p0_{4 -} P . : Si0 2 -Si -,~

-, _....

• I

• I

: I

r

~

r ~r' ⁱ

^,

^x-.

^\

0-':iZ...-__

^{-, ''.6,}

...

i --~~

1 : ---.--=::."

: i ~V--O

. \ I

. I

\ I

\70

I -.

1 "

\7 '0

\ 1 \ I

\7"

.

0

\

-, ^\

\7 0

I /

i /

'Y

0

\7 '0

5

o

10

25 20

~

E

15

...

_a.

Cll Cl

30

Sottom ^{Fig. 6:}Vcnical disu-ibuticn01'nutricnts in Lake Suribati01'thc Syowa Oasis.

as in the results on phosphatc-P

4.2 Sources and Controlling Factcrs ofNutrient Distribution

Saline lakes and ponds have no outflows. Thus non-volatile substances, such as elissolveel salts, including nutrients supplicd from loeal snow anel glaeial meltwaters accumulate in the water bodies over a long period of time.

Therefore, local snow and glacial meltwaters through surface meltstream and subsurface flow can be considered tobeimportant nutrientsourees.

TORI! er al. (1975) reported nutrients in meltstrearns in the Wright Valley of the McMurdo Oasis, and found appreciable amounts of silicate-Si. phosphate-P, nitrate-N anel ammonium-N (Tab. 5). Measurements of the Sollas-Lacroix Glacier and Taylor Glacier meltstreams flowing into Lake Bonney indicated that phosphate-P and nitrate-N were relatively abundant (TORII et al. 1975, WEAND et al. 1977). Silicate-Si and phosphate-P can be supplied mainlybyerosion of soils and rocks in the catchment areas, although atmospheric salts are also possible sourees. For example, WEAND et al. (1977) founel that the bulk of phosphate-P from Sollas-Lacroix meltstreams contributeel to Lake Bonney was deliveredeluring the first two wecksofflow, andsuggesteel that weathering processesin the streambedeluring the long winterproduced phosphate-Pthat was easilyleachedeluringtheearly stages of meltflow,

Mcltstrcam

.""""-L"U

^{mx Glncicr}

Lowcr Glncicr Soilas-Lncroix Glncicr

SiO,-Si PO:-N NO,-N NO,-N NH,--N

fpg-,ll.j'I (llg-ill·1 (pg-aL·I' j (pg·--,lt·l 'I (pg-at·1 ) Rcfercnccs

12.0 (Im 0.36 O,l)O O,lIO Toxn ctnl.(1975)

54,0 LOO NR 0.36 11,72 ihid.

97.0 0.25 4.50 lUX (WO ibicl.

GO (U 8.9 OAI 0 \1.-\SL\iOTOClal.(l932)

95.5 0.58 21.8 0.33 ND TORIIctal.(1975)

91.0 O,SI 15.5 11,74 ND ibid.

3,lI 0.43 1.79 ND 4,88 ibid.

NR 0-23 0.71-22. ! O-L1 O",IG \VL'\"Deral.(1977)

Tab. 5: Nurricntconccntrationsin mcltstrearnsIromthc McMurdo Oasis.ND: NOI dClCC1C<!. NR: Not rcportcd

Distribution ofdissolvcd nitrogcn gas in thc anoxic layers ofthc west lobe 01'Lake Bonney cxhibited the highest d 15N values (1.5-2.5%e-) among those observed in the anoxic Iayers 01' various aquaric environments (WADA er al. 1984).Itrevcaled that denirrification 01' nitrate took place at tempcratures Iower than

er

C. This process may be importnur for rhe losses 01'inorganie nitrogen cornpounds. Nutricnts losses are also due to the deposition into the lake bottom as weil as the fixanon by benthic organisms (PARKER&SIMMONS 1985).

PARKER et al, (1978) reported that iee core ancl frcsh snow samples from the South Pole contained considerable amounts 01' nitratc-N and amrnonium-N, and cxplaincd that these inorganic nitrogen compounds were due to auroral activity. These inorganic nitrogen compounds should be largely responsible for the disrribution ofnutrients in lakes and ponds in Antaretic oascs.Ü^{l 5}N values 01'nitrate in soilsfromthe Dry Valleys region showed ex trcmely low values (-23.4 to -11.5%0) as eompared with other arcas 01'rhe world (WADA et al. 1981, 1984). This result supports the hypothcsis proposed by PARKER ct al. (1978).

For the eoneentration 01' silicateSi, phosphatc-P ancl ammonium-N in the anoxic bouom Iayers 01' most mcromictic lakes diseussed above can be explaincd as follows: Nutrients derived from meltstrcams are first used by primary producers, ineluding diaroms, followcd by precipitation 01' some dead plankton towards the lake botrom, and then undergo microbial dcgradnrion. Bacterial numbers determined by the acridine orange epifluo- rescence dirocr count method showed a marked incrcase in rhe anoxic bottom layers 01'Lakes Vancla and Fryxell (TAKII er al, 1986. KONDA et al. 1987, unpubl. rcsults). Thus. the nutrients releasecl by microbial degradation 01' organic substances are accurnulated in thc stagnanl lake bot 10m layers over a long periocl of time. High abundance 01'refractory organic substances in the bottom anox ic layers 01'Lakes Fryxcll ancl Vanda supports this contention (MATSUMOTO et al. 1984, 1987, 1988). However, the abundance ofphosphate-P in Home Lake can be explainecl by the influences of penguins and skuas nesting around the lake (MATSUMOTO et al. 1982).

4.3 [n!lncnccs011Primary Producli\'itr

These unique nu trient clistributions may reflect the distribution ofphotosynthetic plankton ami decomposers, such aS bacteria in the lakes ancl ponds. ANGINO& ARMITAGE (1963) suggest that inorganie nitrogen may limit primary procluction in Lake Bonney. Later detailecl studies 01' nulrients in the lake have shown that inorganic nitrogen is abundant and not growth-limiting (HOEHN et al. 1977, WEAND et al. 1977). Phosphate-P is present in much lower concentrations lhan inorganic nitrogen, ami may be growth-Iimiting to phyloplankton in the mixolimnion in the early austral summer 01' the year (HOEHN et al. 1977), whilst WEAND et al. (1977) determined condensed-P concentration in the mixolimnion wh ich is three times that in the concentration 01' phosphate-P ancl conc1uded that phosphrous does not limit productivily in the lake. GOLDMAN et aL (1967) reported that the addition 01'nitrate stimulaled carbon fixation in Lake Vanda littoral ancl pelagic waters, but the addition 01'phosphate for the littoral waters did not. Further study on phosphale-P concenlration levels and33p uptake experiments have demonstratecl that phosphorous is a major limiti ng nutrient to the primary producers in the lakes 01'the McMurdo Oasis (SIMMONS et al. 1979), This degree 01'limitation appears to follow the order:

Lake Vanda=Lake Joyce>Lake Hoare>Lake Bonney (west lobe)>Lake Fryxell>Lake Miers. VINCENT (1981) studied production strategies in Lake Fryxell ancl suggests that nutrient supply, rather than in silu light 01' temperature, determines lhe large lake-to-Iake and depth varialion in primat')' productivity, viz, nutrient availabi- lity appears to control algal biomass. For Lake Skallen Oike in the Syowa Oasis, TOMINAGA (1977) reported thai the addition ofnitrate-N stimulated primary production, but that 01'phosphorous did not. HAND&BURTON (1981) suggest that inorganic nitrogen inputs may limit primary production in Ace Lake, but phosphate may be

Jimiting it in Clear Lake ofthe Vestfold Oasis. These results reveal that phosphorous^01'nitrogen nu trient is limiring primary productiviry in most Antarctic lakes and ponds. Virtually the absence of nutrient cycling leads to oligotrophie status of Antarctic meromictic lakes and ponds (AKIYAMA 1985. PARKER&SIMMONS 1985).

5. ACKNOWLEDGEMENTS

The authors are greatly indebted to the Antarctic Division. DSIR. Ncw Zealand, US National Science Foundation and Navy, National Institnte of Polar Research (Japan). and Japan Polar Research Association for their kind support in Antarctic researchcs.

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