Testate amoebae in late quaternary sediments of the Cape Mamontov Klyk (Yakutia)

ISSN 1062-3590, Biology Bulletin, 2009, Vol. 36, No. 4, pp. 363–372. © Pleiades Publishing, Inc., 2009.Original Russian Text © A.A. Bobrov, S. Müller, N.A. Chizhikova, L. Schirrmeister, A.A. Andreev, 2009, published in Izvestiya Akademii Nauk, Seriya Biologicheskaya, 2009,No. 4, pp. 433–444.

363

Testate amoebae inhabit practically all water andland habitats, but prefer bogs and litter of coarse humussoils. Specific environmental conditions determine thedevelopment of communities specific to a given habitat.Habitat preferences of different species and fair preser-vation of their tests, which keeps especially well in oli-gotrophic conditions, both contribute to their great sig-nificance in paleoecological research (Warner, Char-man, 1994; Charman et al., 2007). The speciescomposition of a testate amoeba paleocommunity andits structure make it possible to reconstruct environ-mental conditions of the sediment deposition period.Ecological groups and indicator species of rhizopodsare particularly important. Rhisopod analysis has notbeen widely used in Russia and lingers only at the ini-tial stage of accumulation of information on testateamoeba communities of the Late Quaternary sediments(Bobrov, 2003). Despite the long history of researchinto the modern and Late Quaternary flora and fauna ofthe East Siberian Arctic, the data on the protozoan pop-ulation of this region are scarce; particular features oftheir ecology, paleoecology, and geographic distribu-tion being practically unexplored.

The traditional geochronological scheme distin-guishing within the Upper Pleistocene the warm Karginand cold Sartan periods was used for interpreting theresults of rhizopod analysis. During the last few yearsthere have been a number of publications questioningthe predominance of a warm climate in Siberia 50000–25000 years ago. The results of micropaleontologicalresearch are of great interest because they provide addi-tional information about the environmental conditionsof the sediment deposition period and thus about theclimatic peculiarities of a certain period.

The goal of the present study is analysis of the diver-sity of the testate amoebae from the Late Pleistoceneand Holocene sediments of Cape Mamontov Klyk(northeastern Yakutia) and the reconstruction of theirhabitat conditions.

MATERIAL AND METHODS

Cape Mamontov Klyk (

73°60

′

–73°63

′

north latitudeand

116°88

′

–117°18

′

east longitude) is situated on theLaptev Sea coast between Anabar and Olenek bays,approximately 30 km to the north of PronchishevRidge. The area of study belongs to the zone of subarc-tic tundra. The present-day climate is characterized bylong winters (8 months) and short and cold summers;the mean January temperature is

32–34°C

, and themean July temperature is about

9°ë

. Precipitation var-ies from 200 to 300 mm per year. Predominant soils aretundra gley soils and bog gley soils with the permafroststratum beginning at the depth of 30–40 cm (Dobrovol-skii, Urusevskaya, 2004). The predominant vegetationtype is moss-dwarf-shrub tundra with rarefied grasscover.

Samples were taken in 2003 on Cape MamontovKlyk from sediments of different geneses: fluvial, allu-vial, ice complex, alas (thermokarst depression), andalluvial–dealluvial (thermoerosive depression).

The samples in the form of water suspension werepassed through a sieve with a cell size of 0.5 mm andthen centrifuged. Preparations were examined with alight microscope under 200

×

and 400

×

magnifications.The average amount of preparations per sample was 5.The amount of identified tests was dependent on thedensity of the testate amoebae in the sample and rangedfrom 1 to 350 specimens. The ordination of samples in

Testate Amoebae in Late Quaternary Sediments of the Cape Mamontov Klyk (Yakutia)

A. A. Bobrov

a

, S. Müller

b

, N. A. Chizhikova

c

, L. Schirrmeister

b

, A. A. Andreev

b

a

Moscow State University, Soil Science Faculty, Moscow, 119992 Russia

b

Alfred Wegener Institute for Polar and Marine Research, Telegrafenberg A 43, Potsdam, 14473, Germany

c

Ulyanov–Lenin Kazan State University, Kremlevskaya ul. 17, Kazan, 420008 Russia

Received June 4, 2008

Abstract

—The results of the analysis of Rhizopoda from permafrost sediments of the cryolithozone of north-eastern Siberia are presented. Testate amoeba communities (Rhizopoda: Testaceafilosea, Testacealobosea) ofthe late Pleistocene and Holocene and modern habitats of the Cape Mamontov Klyk (the Laptev Sea coast inthe vicinity of the Lena River estuary) have been researched. The paleocommunity structure was examined;assessment of rhizopod diversity in sediments of different (fluvial, alluvial, ice complex, alas, and alluvial-deal-luvial) geneses was conducted.

DOI:

10.1134/S1062359009040074

ECOLOGY

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accordance with testate amoeba species compositionwas based on the method of principal coordinates (Leg-endre, P., Legendre, L., 1998).

DESCRIPTION OF EXAMINED SAMPLES

Fluvial facies

(A) is presented by the sediments oftemporary water courses, it formed 44000 years ago.This facies is distinguished by the low content of organiccarbon (0.2% on average) and the lowest C/N ratio(between 0.7 and 2.5).

Alluvial facies

(B) belongs to the floodplain stage; theage of these sediments ranges from 43620 +170/–1400to 31250 +1080/–950 years ago, thus they belongentirely to the Kargin interstadial. These samples are dis-tinguished by significant variations in the content oforganic matter (from 0.2% to 15.3%) and by high C/Nvalues (up to 24.9). The periods of soil formation charac-terized by stable surface conditions were regularly inter-rupted by short periods when sedimentation processesintensified.

Ice complex sediments

(C) embrace the end of theKargin interstadial and Sartan. The content of organiccarbon in samples ranged from 1.6% to 4.9%, and theC/N ratio varied between 7.2 and 16.1. The decrease inthe C/N ratio in comparison to the profile B (alluvialseries) points to the rise of more dry and aerobe condi-tions entailing the intensification of the processes oforganic matter mineralization.

Holocene sediments

(D

2

) formed at the surface ofthe Sartan ice complex in relatively warm and humidclimatic conditions.

Alas complex sediments

(D

3

) are situated at a dis-tance of 8 km from the main profile (the ice complex).They formed during the Late Pleistocene andHolocene. They are usually distinguished by wide dis-persion in the content of organic carbon due to thechanging of lake and bog facial conditions in the periodof their deposition (Kholodov et al., 2006).

Alluvial–dealluvial sediments

(D

1

) are thermoero-sive valley sediments of Holocene origin. The samplesare soils of various granulometric composition withinclusions of peat and sand with plant residues. Theyare characterized by a nearly neutral or alkalescentreaction of their aqueous extract and show a significantvariation in organic carbon content.

Forty of the examined samples belong to the LatePleistocene, 18 of them belong to the Kargin intersta-dial, and 22 belong to the Sartan. Holocene sedimentsinclude 12 samples, and modern surface sedimentsinclude 15.

Surface samples

were taken in the immediate prox-imity of the ice complex from a depth of 0–5 cm, withthe diversity of habitats (polygons, sand outcrops, edo-mas, oligotrophic bogs, and thermokarst depressions)taken into consideration.

RESULTS

We found testate amoebae in 39 out of 67 samplesof the Late Pleistocene and Holocene origin, whichwere carbon-dated as belonging to the period of the last44000 years. The palaeocommunities of testate amoe-bae consisted of 77 species and subspecies forms. Pro-tozoans were not found on sand outcrops. The totalamount of taxa in samples of Late Quaternary originand in modern surface samples was 95 species, variet-ies, and forms (Table 1). Protozoans were identifieddown to the level of subspecies taxa and morphologicalforms.

Species diversity in the Late Pleistocene samplesamounted to 68 taxa, that in the Holocene samples was2, and in modern samples it was 39 taxa. The number ofspecies in the samples from the Late Pleistocene periodwas almost 30% higher than that from the Holocene.The diversity of the testate amoebae in the samples ofthe Kargin period was more than 2 times higher than inthe Sartan (Table 2). For the purposes of paleoecologi-cal analysis, we divided testate amoebae into 4 maingroups in accordance with their environmental prefer-ences: hydro-hygrophilous, sphagnobiontic, soil andeurybiontic, and calciphilous. The species compositionof the sphagnobionts and hydro-hygrophils in the Kar-gin period was substantially higher than in the Sartan,and these groups were generally more common inpalaeocommunities in comparison with the modernsamples (Table 2).

The number of testate amoeba taxa in the samples ofthe Late Pleistocene and Holocene origin varied from 1to 32 species and subspecies forms. The highest speciesdiversity was recorded for the Kargin samples. Ten outof the 20 samples whose species composition included15 or more taxa belonged to the Kargin, 5 samplesbelonged to the Sartan, and 5 belonged to the Holocene.This diversity allows us to call the palaeocommunitiesof testate amoebae full-ranged ones, a fact dependanton environmental conditions favorable for the forma-tion of testate communities. The conditions for theirpreservation in sediments were also favorable; the sed-iments were not affected by secondary cycles of micro-biological and biochemical activity intensification, andthe deposition of palaeocommunities proceeded at highspeed.

Fluvial sediments.

In the only sample from fluvialsediments, we found 17 testate species and varieties,among which hygrophilous species

Difflugia

, sphagno-biontic

Heleopera

and

Argynnia

, and 2 specimens ofaquatic

Arcella

discoides

v

.

scutelliformis

were regis-tered. We also recorded the first occurrences for theLate Pleistocene of the sphagnum-moss species

Paraquadrulla

irregularis

and soil-moss

Bullinulariagracilis

.

Alluvial sediments.

The samples mainly representwaterlogged soils and soils with peat inclusions whoseage is between 44000–40000 years. Forty-five testatetaxa were found in the 11 samples. These sediments are

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TESTATE AMOEBAE IN LATE QUATERNARY SEDIMENTS 365

Table 1.

List of testate species from the Late Pleistocene and Holocene sediments of Cape Mamontov Klyk

SpeciesOccurrence, %

EcologyLate Pleistocene Holocene Surface samples

Arcella arenaria

v.

compressa

Chardez 10.3 18.2 0.97 M

A. artocrea

Leidy 9.1 0.19 Sh

A

. c. f.

crenulata

Deflandre 3.4 ShM

A. discoides

v.

scutelliformis

Playfair 6.9 W

A. rotunda

v.

aplanata

Deflandre 0.39 ShM

A

. sp. 3.4

Bullinularia gracilis

Thomas 3.4 MS

B. indica

Penard 0.6 MS

Trigonopyxis arcula

(Leidy) Penard 10.3 MS

T. minuta

Schönborn, Peschke 3.4 S

Centropyxis aculeata

(Ehrenberg) Stein 3.4 W

C. aculeata

f. A 3.4 W

C. aerophila

Deflandre 86.2 63.6 5.41 M

C. aerophila

v.

minuta

Chardez 86.2 72.7 0.58 WMS

C. aerophila

v.

sphagnicola

Deflandre 41.4 45.5 ShM

C. cassis

(Wallich) Deflandre 3.4 27.3 0.19 ShMS

C. constricta

(Ehrenberg) Penard 51.7 18.2 6.76 WS

C. constricta

v.

minima

Decloitre 79.3 63.6 12.16 W

C. discoides

(Penard) Deflandre 3.4 W

C. gibba

Deflandre 3.4 ShM

C. orbicularis

Deflandre 20.7 18.2 0.19 WShM

C. plagiostoma

Bonnet, Thomas 86.2 45.5 0.39 S

C. plagiostoma

f. A (major) 37.9 0.58 S

C. plagiostoma

f. B (minor) 48.3 54.5 3.86 S

C. plagiostoma

Bonnet-Thomas v.

oblonga

Chardez 9.1 S

C. plagiostoma

v.

terricola

Bonnet, Thomas 3.4 54.5 S

C. platystoma

(Penard) Deflandre 6.9 27.3 0.19 WMS

C. sylvatica

(Deflandre) Thomas 86.2 72.7 4.05 WShM

C. sylvatica

v.

globulosa

Bonnet 3.4 SC. sylvatica v.

microstoma

Bonnet 37.9 9.1 S

C. sylvatica

v.

minor

Bonnet, Thomas 86.2 63.6 0.39 ShS

C

. sp. 1 3.4

C

. sp. 2 9.1

Cyclopyxis arcelloides

Penard 3.4 WShM

C. eurystoma

Deflandre 44.8 36.4 1.16 WSh

C. eurystoma

v.

parvula

Bonnet, Thomas 72.4 81.8 11.39 S

C. kahli

Deflandre 67.2 18.2 WShS

C. kahli

Deflandre f. A (minor) 6.9 WShS

C

. sp. 6.9

Plagiopyxis bathystoma

Bonnet 10.3 S

P. callida

Penard 20.7 9.1 WShMS

P. declivis

Thomas 3.4 ShS

P. minuta

Bonnet 3.4 0.39 MS

P. penardi

Thomas 31 36.4 WS

Heleopera petricola

Leidy 20.7 WSh

H. petricola

v.

amethystea

Penard 6.9 WSh

H. petricola

v.

humicola

Bonnet et Thomas 3.4 S

H. sphagni Leidy 3.4 WMNebela bigibbosa Penard 0.19 WShMN. collaris (Ehrenberg) Leidy 3.4 18.2 ShM

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Table 1. (Contd.)

SpeciesOccurrence, %

EcologyLate Pleistocene Holocene Surface samples

N. lageniformis Penard 3.4 0.39 ShMN. parvula Cash 6.9 ShMN. penardiana Deflandre 9.1 WN. tincta (Leidy) Awerintzew 3.4 9.1 9.85 ShMN. tincta f. stenostoma Jung 0.58 ShMSN. sp. 6.9Argynnia c.f. teres Jung 31 18.2 WShArgynnia sp. f. A (minor) 3.4 WShSchoenbornia humicola (Schönborn) Decloitre 5.02 SSch. viscicula Schönborn 0.39 SDifflugia bryophila (Penard) Jung 3.4 ShMD. cratera Leidy 3.4 18.2 WD. difficilis Thomas 18.2 WD. globulus Walich 37.9 36.4 1.93 WShD. lucida Penard 20.7 9.1 WShD. mammilaris Penard 6.9 WD. microstoma (Thomas) 3.4 WD. minuta Rampi 10.3 9.1 ShD. oblonga Ehrenberg 9.1 WD. oblonga v. longicollis Gassowsky 9.1 WD. penardi Hopkinson 6.9 9.1 WD. pristis Penard 6.9 WD. c.f. pyriformis Perty 3.4 WD. sp. 1 3.4 WD. sp. 2 3.4 WPhryganella acropodia (Hert. et Less.) Hopkinson 55.2 27.3 0.97 WMSPh. acropodia c.f. v. australica Playfair 13.8 45.5 WPh. hemisphaerica Penard 9.1 WShMParaquadrulla irregularis Archer 3.4 ShMAssulina muscorum Greef 2.9 MValkanovia delicatula (Valkanov) 0.39 ShMEuglypha ciliata (Ehrenberg) Wailes 0.19 WShME. ciliata f. glabra Wailes 9.46 WShMSE. cuspidata Bonnet 0.39 SE. dolioliformis Bonnet 0.19 MSE. laevis (Ehrenberg) Perty 5.41 WShMSE. strigosa f. glabra Wailes 2.32 ShMSCorythion dubium Taranek 0.77 WShMTrinema enchelys (Ehrenberg) Leidy 0.58 WShMT. lineare (Ehrenberg) Leidy 6.56 WShMST. penardi Thomas, Chardez 1.93 MSPseudodifflugia c.f. gracilis Schlumberger 3.4 27.3 WP. gracilis v. terricola Bonnet et Thomas 6.9 9.1 STestacea sp. 1 10.3 9.1Testacea sp. 2 0.19Number species 68 42 39

Note: The ecological characteristic is based on Chardez classification (Chardez, 1965): aquatic (W), sphagnobiontic (Sh), moss (M), andsoil and eurybiontic species (S).



the richest in the testate amoeba species composition(the genera Arcella, Centropyxis, Cyclopyxis, Heleopera,Nebela, Argynnia, Difflugia, Phryganella, and Pseudodif-flugia). Paludification periodically interchanged withmore automorphic stages, which led to the formation oforganic-mineral soils. We found 12 species and subspe-cies taxa belonging to the group of soil and eurybionts(Centropyxis, Cyclopyxis, Plagiopyxis, Phryganella) insoil samples. Some species represent minor sizegroups: minor, minuta, minima. It is not uncommon forthe species composition to be several times lower in thesamples where such groups prevail. Hydrophilous spe-cies are absent, and eurybiontic and soil species domi-nate. The representatives of the soil group of the testateamoebae from the genus Plagiopyxis begin to occur.Neutral and alkalescent soil reaction determines theoccurrence of calciphilous species Centropyxis plagios-toma and Cyclopyxis kahli. Alluvial sediments are dis-tinguished by both significant species richness oftestates and fair preservation of their tests. In the upperstrata of the sediments in the sample with peat inclu-sions, 32 testate species and varieties was found. Themaximal species diversity of testate amoebae was notedthere in comparison with the samples from other sedi-ment types of Cape Mamontov Klyk and Late Pleis-tocene, Holocene, and surface samples from the Byk-ovskii Peninsula, which had been studied earlier(Bobrov et al., 2003). The species composition in thissample was greater mainly due to the significantamount of hydrobionts of the genus Difflugia and sphag-nobionts of the genera Heleopera, Nebela, and Argyn-nia. The climatic conditions can be characterized aswarm and humid.

Ice complex sediments. These sediments embracetwo periods of the Upper Pleistocene: Kargin and Sartan.The lower Kargin part of the ice complex, which is43000 years old, can be classed as a soil stage of sedi-ment deposition judging by the domination of the soiland eurybiontic testate group. The testate amoebae popu-lation consists of species belonging to the genera Centro-

pyxis, Cyclopyxis, and Phryganella, most of which arerepresented by minor size groups: minor, minuta, minima.But by the end of the Kargin, the soil stage gave place tobog. In the sample of 27220 +310/–300 years of age,19 rhizopod species and varieties were found. In additionto soil and eurybiontic species, hygrophilous speciessuch as D. globulus and D. cf. prisits begin to occur. Asingle finding of a sphagnobiontic Argynnia cf. teres canalso be mentioned. The hydromorphism degree was ris-ing against the background of meso- or oligotrophic con-ditions, judging by the rise in numbers of calcifilousC. plagiosoma represented by almost every morphologi-cal form.

The population of most samples of the ice complexof the Sartan period consists of soil and eurybionticspecies. The beginning of the Sartan (the sample dated24600 +170/–160 years old) is denoted by a commu-nity consisting of 19 rhizopod species and subspeciesforms. The peculiarity of its species composition con-sists in the presence of sphagnobiontic Trigonopyxisarcula and T minuta, which usually inhabit coarsehumus litter of forest soils, as well as three soil speciesof the genus Plagiopyxis—P. callida, P. minuta, andP. penardi.

At the minimum of the Sartan, cooling conditionsworsened. For example, only 9 species and varieties(represented mainly by minor, minuta, minima, andmicrostoma forms) of the genera Centropyxis andCyclopyxis were found in a sample of 18920 ± 70 yearsof age. This presumably points to unfavorable climaticconditions leading to a decrease in the test size such astemperature fall (Smith, 1988) or the coming of a drierperiod (Bobrov, 2005). The presence of the varietyCyclopyxis eurystoma v. parvula, which is smaller thantypica, among the dominant species corroborates this.The increase in hydromorphism was recorded in the onlysample where the dominant group included hydro-hygrophilous species of the genus Difflugia D. globulus,D. lucida, and aquatic and sphagnobiontic A. cf. teres

Table 2. The numbers of testate amoeba taxa in the Late Pleistocene and Holocene sediments of different geneses

Ecological group of testate amoebae

Sediment type Period of sediment deposition

fluv

ial

allu

vial

ice

com

plex

alas

allu

vial

–dea

lluvi

al

Kar

gin

Sart

an

Lat

e Pl

eist

ocen

e(K

argi

n, S

arta

n)

Hol

ocen

e

mod

ern

Hydro-hygrophilous 4 12 3 7 6 12 9 15 7 2

Sphagnobiontic 6 16 14 5 9 25 9 25 12 15

Soil and eurybiontic 5 17 23 13 14 15 17 27 18 20

Calciphilous 2 4 4 2 4 6 4 6 5 3

Total number of taxa 17 49 41 27 26 58 26 68 42 39

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BOBROV et al.

along with soil and eurybiontic representatives of thegenera Centropyxis, Cyclopyxis, and Phryganella.

The beginning of the Holocene is denoted by humidand warm conditions. Seventeen testate amoeba speciesand varieties were found in the sample of 9480 ± 40 yearsof age. The population of testates is typical for meso- andoligotrophic bogs; species indicating an intense paludifi-cation process are present: Arcella arenaria v. compressa,Argynnia sp., and Phryganella hemisphaerica. Accordingto the data of spore-pollen analysis, the formation of for-est-tundra ecosystems began about 9300 years ago andwas concurrent with climate warming, and the Palaearcticclimate of that period was warmer than the modern cli-mate (Andreev et al., 2002, 2004; Neronov, 2006).

Soil and eurybiontic species from the samplesbelonging to the Middle Holocene are characteristic ofautomorphic soil conditions. The occurrence of hygro-philous Centropyxis cassis and sphagnobiontic Heleoperasphagni in the sample from the end of the Holocene(2785 ± 30 years ago) indicates the increase in hydro-morphism of the environment.

Thermokarst lake sediments (alas sediments). Thepopulation of alas sediments consists mainly of aquaticspecies and sphagnobionts. Judging by the dominationof D. globulus (25%), these sediments formed in moistbog conditions. The similar composition of ecologicalgroups was also noted for other alas samples. For exam-ple, 20 species and varieties of rhizopods characteristicof overwetted meso- and oligotrophic bogs were foundin one of the samples. The presence of the soil speciesP. penardi and xerophilous moss and soil species Bull-inularia indica in this sample can apparently beexplained by the “pulsatory” seasonal water regime, theinterchanging of water influx and droughty stages.

Sediments of thermoerosive depression. As in thecase with alas sediments, aquatic and sphagnobionticspecies (Centropyxis platystoma, Cyclopyxis arcel-loides, and Pseudodifflugia gracilis) dominate here.The intense processes of paludufication of theHolocene alluvial–dealluvial sediments contributed tothe high density and significant species diversity oftestate amoebae. Twenty-two species and subspeciestaxa including the group of aquatic species of the genusDifflugia (D. globules, D. minuta, D. oblonga, andD. sp.) were found in one of the samples; this points to alengthy paludification stage. The latest occurrence of asphagnobiontic Argynnia sp. in the Late Quaternary sed-iments was registered in the sample of 1500–2000 yearsof age.

Modern surface samples. Eurybiontic and soil spe-cies predominated in the sample taken from the edomasurface horizon. Single occurrences of hydro- and hygro-philous species (Arcella artocrea, Arcella arenaria v.compressa, and C. cassis) can be explained by temporaryseasonal excessive humidification of the habitat. As wenoted before (Bobrov et al., 2003), the cooccurrence ofsoil eurybiontic and hygrophilous species in samples ischaracteristic of tundra habitats. Apparently, this phe-

nomenon is determined by peculiarities of seasonalchange in the hydrological regime as well as the confin-ing layer of permafrost. The population of the centralpart of the polygon consists of hydro- and hygrophilousspecies of the genera Difflugia and Arcella. The litter oftundra gley soil can be characterized as a humid habitatjudging by the presence of hydrophilous and sphagno-biontic species (D. difficilis, Nebela biggibosa,N. lageniformis, and N. tincta). The surface samplestaken from a thermokarst hollow and an alas are poor intestates (single occurrences of eurybiontic species of thegenera Centropyxis and Cyclopyxis). The population ofan oligotrophic bog is distinguished by occurrences ofhydrophilous D. globulus and hygrophilous C. platys-toma.

On the whole the species diversity in alluvial andfluvial samples belonging to the Kargin period is signif-icantly higher than in modern samples, and especiallyin comparison to the Sartan sediments.

The mathematical treatment of the data of protozo-ological research of the Late Quaternary and surfacesamples from Cape Mamontov Klyk consisted in theanalysis of significance of differences between distin-guished ecological groups of testate amoebae in orderto evaluate the correctness of distinguishing these spe-cies into the above-mentioned groups, and the ordina-tion of the examined samples within ecological space inorder to analyze their differences in composition of thetestate population. In the latter case, a preliminaryexpert judgment of the ecological group compositionswas conducted, and different weights were assigned tothe indicator species according to the breadth of theirecological niche. The narrower the species ecologicalniche, the greater the weight assigned to the species.Singularly occurring species were excluded from theanalysis. The ANOSIM test was conducted in order toestimate the division of the groups in the ecologicalspace of the original dimension and in the ordinationplane. The Bray-Curtis metric was used for analyzingthe principal coordinates and nonmetric scaling (Leg-endre, P., Legendre, L., 1998).

According to the results of statistical treatment, allthe species in the ordination plane were divided into3 main groups (Fig. 1): hydro-hygrophilous, soil, andsphagnobiontic. The widest dispersion can be seenamong sphagnobiontic species. This fact reflects thecontinuity of habitat environments and the breadth ofthe ecological niche with respect to the hydrologicalregime. The compactness of the soil species groupresults from the narrow range in which the habitat pHchanged; it was nearly neutral. In the habitats populatedby aquatic and bog species, the reaction ranged in awider diapason, especially in bogs, where it variedfrom acid pH in oligotrophic bogs to slightly acid andnearly neutral pH in mesotrophic bogs. We divided thespecies on the basis of two criteria: the presence of thespecies in a sample and its abundance. The presence ofthe species proved to be a more sensitive and informa-



tive method of data treatment (Table 3). The values inthe first column characterize the division of species inthe space of the original dimension. The results of thestatistical treatment lie within the range from –1 to +1.The closeness of the coefficient value to +1 points atcomplete division of the groups; 0 means that thegroups are mixed (nondivided); –1 means that one ofthe groups is highly disperse and the species from thisgroup occur in many samples in various conditions. Ascan be seen from the Table 3, testate ecological groupsdiffer significantly when the “presence of the species”parameter is used. Sphagnobiontic soil species and soilhydrophilous species differ with a high (99.9%) confi-dence level. One of the main factors determining pecu-liar features of the testate amoeba species compositionis the habitat humidity.

The analysis of the ecology of indicator speciesrevealed that the sample distribution along axis 1 isexplained by the habitat humidity gradient (Fig. 2). Thesample distribution along axis 2 complies with thetestate species diversity. The higher the amount of indi-cator species in samples, the more conspicuous theirdiversion by ecological preferences. For this reason wecan see two distinct groups in the upper part of axis 2:groups of humid (A) and dry (B) habitats with an inter-mediate (C) group along the humidity gradient, as areflection of environment continuity. Group A is repre-sented by humid habitats, which belong generally to theKargin time, partially by the Holocene samples (alasand alluvial–dealluvial sediments) and one modernsample from the central damped part of the polygon.The indicator species from the group A samples belonggenerally to the genus Difflugia. Group B (dry habitats)embraces the samples that belong mainly to the Sartanand partially to the Holocene. The indicator speciesfrom these samples belong to the genera Centropyxisand Trigonopyxis. Group C includes the samples inter-mediate with respect to the humidity gradient. Group Dconsists of habitats with low testate species diversityand includes samples with rare occurrences of testateamoebae from all three periods: the Late Pleistocene(mainly the Sartan time), Holocene, and modern habitats.

The main conclusion that appears from the statisti-cal treatment of the results of rhisopod analysis is thatwith respect to humidity conditions there were all hab-

itat types in the Late Pleistocene and Holocene but theirratio was different. For example, the group of dry LatePleistocene habitats consists mainly of the Sartan sam-ples (Fig. 2), while the Late Pleistocene samples fromthe Kargin interstadial are widely represented in thegroup of humid habitats. Most of the Holocene samplesbelong to the group of humid habitats. The modernsamples turned out to be poorer than the Late Quater-nary ones in species composition. This fact may reflectthe low diversity of modern habitats in comparison tothe Holocene and especially to the Late Pleistocene.

DISCUSSION

The populations of the testate amoebae of the LateQuaternary sediments demonstrate a number of similarfeatures. This applies in the first place to the dominantspecies compositions, which are very similar in the sam-ples from the Late Pleistocene and Holocene (Table 1,

Table 3. Estimate of the division of ecological groups of species on the basis of the ANOSIM test results

Ecological groupsunder comparison

Original dimension plane Plane of two first ordination axes

species abundance species presence species abundance species presence

Sphagnobiontic and soil species 0.112** 0.118** 0.233** 0.261***

Sphagnobiontic and hydrophilous species 0.051 0.043 –0.005 0.148*

Soil and hydrophilous species 0.382** 0.503*** 0.226** 0.517***

Notes: * The coefficient is significant at the 95% confidence level. ** The coefficient is significant at the 99% confidence level. *** The coefficient is significant at the 99.9% confidence level.

123

Axis 1

Axis 2

Fig. 1. The ordination of testate amoebae from the samplesof Cape Mamontov Klyk with the method of principal coor-dinates.

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BOBROV et al.

Fig. 3). The most common species (Centropyxis aero-phila and C. sylvatica) belong to the group of cosmopol-itan soil and eurybiontic species. Calciphilous C. pla-giostoma and C. kahli also belong to this group. Thechanging of hydrological regime from automorphic condi-tions to hydromorphic, interchanging of sedimentogenesisprocesses, and formation stages of organogenic andorganic-mineral soils are denoted by the entrance of hydro-and hygrophilous species D. globulus, Argynnia sp., andPhryganella acropodia v. australis into the group ofdominant species. Extremely cold and dry environmen-tal conditions are reflected in the development of minorforms by a number of species: C. aerophila v. minuta,C. sylvatica v. minor, C. constricta v. minima, andC. plagiostoma f. B (minor).

The species of the genus Centropyxis predominatein all sedimentation types. The hydrophilous represen-tatives of the genus Difflugia codominate in alluvial,alas, and alluvial–dealluvial sediments, while in thesurface samples the species of the genera Euglypha andNebela hold the second place after the genus Centropy-xis. The representatives of the genera Assulina, Val-kanovia, Euglypha, Corythion, and Trinema, which arecommon in surface samples, were not found in paleo-communities. Their fragile tests are destroyed easily,

and therefore, they are seldom used in paleoecologicalanalysis.

All four main ecological groups (soil and eurybion-tic, sphagnobiontic, hydrophilous, and calciphilous)were widely represented in all sedimentation types.They allow diagnosis of the environmental conditionsof sedimentation genesis, in the first place the hydro-logical regime and sedimentation type (bogs or soils),with a fair degree of certainty. The indicator speciesbelonging to these ecological groups, such as calciphil-ous C. plagiostoma, hydrophilous Difflugia cratera andPh. Hemisphaerica, sphagnobiontic and hygrophilousHeleopera humicola v. amethystea, H. sphagni, andA. c. f. teres, and soil Trigoniopyxis minuta, have a nar-rower tolerance range and ecological optimum than thegroup as a whole. Using such species in paleoecologi-cal analysis helps determine the characteristics of theenvironmental condition of sedimentation genesis moreaccurately.

The population of the testate amoebae of modernhabitats also includes the representatives of all ecolog-ical groups. The main characteristics that distinguishthe modern testate population from that of the LatePleistocene and Holocene are (1) a significantly smallernumber of hydro-hygrophilous and sphagnobiontic

G-5AA-3

19-411-6 AA-2.2

13-7

14-8

G-2

AA2-63-14

10-11

AA-4

11-7

14-6

14-5AA-2.1

4-11

11-14

11-92-3

2-914-4

9-42-8

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3-7

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93 10-7

2-5

-3

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9-35-3

9-5

3-16

58-3

Ä

D

B

C

Axis 1

Axis 2

d = 0.2

Fig. 2. The analysis of the principal coordinates for Late Quaternary samples. Habitat classification by humidity: A, humid; B, dry;C, intermediate; D, samples with low species diversity.



species of the genera Arcella, Bullinularia, Trigonopy-xis, Heleopera, Nebela, Argynnia, and Difflugia;(2) singular cases of the occurrence of soil speciesbelonging to the genus Plagiopyxis; (3) moss andsphagnobiontic species of the genera Assulina, Val-kanovia, Euglypha, and Trinema inhabiting generallyorganogenic horizons of automorphic soils and surfacelayers of peat soils are widely represented in moderncommunities.

The findings of rare species, in the first place A. c. f.teres and Argynnia sp., allow us to suggest greaterdiversity of habitat conditions in the Late Pleistocene incomparison to the present time. The finding of Nebelabigibbosa in a surface sample represents the northern-most registered occurrence of this species on the terri-tory of Eurasia to this day. This species was also foundin the Pleistocene sediments from the Bykovskii Penin-sula (Bobrov et al., 2003). In the early 20th century, itwas found in Spitsbergen (Penard, 1903). According toTodorov’s data (Todorov, 2001), this species is fre-quently found in the litter of Bulgarian beech forests.Another rare species P. irregularis, which is character-istic of mesotrophic bogs (Opravilova, Hajek, 2006),was found in a sample from the Kargin period flu-vioglacial sediments. Hitherto this was the only findingof Paraquadrulla irregularis in the sediments of theLate Quaternary sediments. A rare form Centropyxisplagiostoma f. oblonga is common in the Late Quater-nary sediments from Cape Mamontov Klyk. D. cratera,a species characteristic of bottom sediments, was foundin the alas samples. The obligatory hydrophily of this

species underlines the aquatic genesis of alas sediments.The results of this part of the present publication may beof interest for the paleogeography of free-living protozo-ans, a research direction which at present is completelyundeveloped in the general course of paleogeography.

CONCLUSIONS

The Late Quaternary sediments of Cape MamontovKlyk, in the first place those of the Kargin interstadial,are comparable to the habitats of the forest-tundra andtaiga zone. Almost all testates are represented here,with the exception of the genera inhabiting forest litterand eutrophic bogs: Quadrulella, Sphenoderia, Placo-cista, Euglypha, Assulina, Trinema, Corythion, Cypho-deria, Pontigulasia, and Lesquereusia. In the Karginsediments (fluvial and alluvial facies and the lower partof the ice complex) changing of the testate ecologicalgroups and indicator species reflects the interchanging oflake, bog, and soil stages against the background of pre-vailing paludification processes. In the Sartan the degreeof xeromorphy in sediment deposition grows. Obligatehydrobionts are absent from samples of this period, thehydrological regime is characterized by droughty condi-tions. The Sartan is characterized by the interchanging ofmesotrophic soil conditions and bog stages like the Kar-gin but to a lesser extent. The difference between therhizopod populations of the Kargin and Sartan liesmainly in the numbers of hydrophilous species. Thus theresults of the rhizopod analysis once again confirm theexistence of the Late Pleistocene (Kargin) interstadial. In

Freq

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80

60

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12

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C. a

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inut

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osto

ma

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ylva

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ylva

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Fig. 3. Testate amoeba dominant and codominant species of the Late (Quaternary) (1) Pleistocene; (2) Holocen) sediments fromCape Mamontov Klyk.

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the samples taken from the ice complex of the BykovskiiPeninsula (Bobrov et al., 2003), the maximal testate spe-cies diversity was also registered in the Kargin intersta-dial (54000–30000 years ago). The results of the rhizo-pod analysis generally confirm the assumption that theSartan was a colder and drier period. Apparently, habi-tat diversity over the course of the Kargin and Sartanwas similar; it was the ratio between different habitattypes that changed. During the Sartan the amount ofhabitats with conditions favorable with respect tohumidity and trophic regime was decreasing, and thearea of water-logged grounds decreased especiallysharply.

Entomological analysis (Kuz’mina, 2001) confirmsthe idea of the Kargin time being a “thermochron” char-acterized by wide distribution of tundra-steppe land-scapes. The results of the palynological analysis and thecomposition of plant macroresidues and bones of mam-moth fauna also contribute to the image of the Sartan asa mammoth steppe with a cold and dry climate(Andreev et al., 2002, 2004).

ACKNOWLEDGMENTS

This study was supported by the German ResearchFoundation (DFG, grants RI 809/17-1 and SCHI 975/1,project “Late Quaternary Environmental History ofInterstadial and Interglacial Periods in the ArcticReconstructed from Bioindicators in PermafrostSequences in NE Siberia”), Alfred Wegener Institutefor Polar and Marine Research (AWI, Potsdam, Ger-many), and the German Academic Exchange Service(DAAD). The authors are grateful to the researchersfrom Moscow State University for their support and toGuido Grosse (Germany) for providing data on surfacesamples.

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Testate amoebae in late quaternary sediments of the Cape Mamontov Klyk (Yakutia)