Micro-benthic crustacean communities in tundra lakes of North-East European Russia

Elena B. Fefilova • Olga A. Loskutova • Sergey V. Pes to v

Received: 22 August 2006/Accepted: 6 June 2007/Published online: 12 July 2007 © Springer Scicnce+Busincss Media B.V. 2007

Abstract We studied micro-benthic copepods and cladocerans in the bottom substrates of 12 lakes in the Bol'shezemel'skaya tundra in North-East European Russia during the summer. About 30 species of Cladocera and 28 species and subspecies of Copepoda were found. The majority of the micro-crustaceans are palaearctic or northern palaearctic. But the harpacti-coid fauna of the western pail of the studied region had specific European features, and three species of the harpacticoid fauna in the eastern part of the region were Siberian. It is therefore a boundary territory for two zoogeographical regions, the arctic and subarctic zones. Acidophilic {Arcticocamptus arcticus (Lillje-borg 1902)) and halophilic (Microsetella norvegica (Boeck 1864)) harpacticoid species were found in the lakes of the eastern part of Bol'shezemerskaya tundra. On basis of their way of locomotion we distinguished live ecological groups and on basis of their feeding habits four ecological groups of micro-crustaceans. Groups with a similar way of locomotion were likely distributed over the studied water bodies. Habitat (inshore versus offshore), substrate particle size and substrate hardness were of paramount importance for the species distribution.

E. B. Fefilova (El) • O. A. Loskutova • S. V. Pestov Ural Division of Russian Academy of Sciences, Institute of Biology of Komi Scientific Center, 28 Kommunisticheskaya St.. Syktyvkar, Komi 167982, Russia e-mail: fefilova@ib.komisc.ru

Keywords Ecological groups • Feeding Locomotion type • Meiobenthos

Introduction

The treeless part of the Pechora lowland is the Bol'shezemel'sky region of the East-European prov­ince. In the East it is restricted by the Ural Mountains, and in the West—by the Pechora river (Fig. 1). Its northern part is located in the arctic zone, while its southern part is in the temperate zone (Gorbatsky 1967). The climate of the Bol'shezemel'skaya tundra is continental, and the continentality of the climate, i.e., the temperature difference between the warmest and the coldest month of the year, increases from the West to the East. The great number of lakes is one of the main peculiarities of the Bol'shezemel'skaya tundra's landscape. The majority of them are shallow and oligotrophic. The lakes are fed by snow and snow-glacial sources which determines their low concentration of organic matter (Vlasova 1976; Khokhlova 1996).

The fauna of the water bodies in Bol'sheze­mel'skaya tundra is diverse and microcrustaceans make up an important part. The first data on the fauna of plankton and meiobenthic crustaceans of this region were obtained in the beginning of the 20th century (Rylov 1917, 1918). After a break the investigation of cladoceran and copepod fauna was continued (e.g., Borutsky 1966; Isiurova 1966;

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Fig. 1 Location of the 12 study lakes. For descriptions see Table 1

25 30 35 40 45 50 55 60 65 70 75 80

Popova 1976; Vehov 1982; Fefilova 2001). Accord­ing to the last inventory 54 species and subspecies of Cladocera and 43 species and subspecies of Cope-poda were found in the Borshezemel'skaya tundra (Fefilova 2002). Studies of zoogeographical analysis of the fauna have been made mainly on Calanoida, Cyclopoida, and Cladocera (Vehov 1982; Fefilova 2002). They illustrate the large role of widely spread European species and the less important role of arctic species in the communities of Bol'shezemel'skaya tundra.

Information on the ecology of meiobenthic crus­taceans in the lakes of the Bol'shezemel'sky region concerns their role in the quantitative development of the benthos or meiobenthos as well as their biotope distribution in the bottom communities (e.g., Loskut-ova and Fefilova 1996; Skvortsov 1997; Ponomarev and Loskutova 2006). These researchers found that microcrustaceans were abundant in the benthos, both in terms of numbers and in biomass. Furthermore, the composition of taxa can be ecologically heteroge­neous as also was observed by Sarvala (1998) for copepods in Finnish lakes.

In this study we compare for the first time the tnicro-benthic copepod and cladoceran communities

of the Bol'shezemel'skaya tundra lakes. Our goals were to determine the species composition, ecolog­ical status (i.e., feeding habits, way of locomotion), zoogeographical status, and distribution in relation to habitat characteristics.

Materials and methods

Study area

Eight of the study lakes (Lakes 1-8) in the Bol'sheze­mel'skaya tundra are located in the Western part of the studied region and belong to the Ortina River basin (Fig. 1). The Ortina River discharges into the Barents Sea. These small lakes, slightly different in origin, were inspected during the beginning of July 2000 (Table 1). The lake waters were slightly acid or neutral, with a dominance of silty or sandy substrate on the lake bottoms. Lakes 2 and 3 are interconnected by a channel. Four of the study lakes (Lakes 9-12) are located in the Eastern part of the Bol'shezemel'skaya tundra. These lakes are larger than the studied water bodies in the western pail of the region and the Eastern water bodies are located at a higher altitude

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than the Western lakes (Table 1). Lakes Bol'shoy Kharbey and Golovka are interconnected making a single system (Kharbey lakes), they belong to Pechora river basin (Fig. 1). Lakes Komaty and Bol'shoy Ngosavey are connected with the Kara river on the Eastern border of the Bol'shezemel'skaya tundra. All Eastern lakes are of glacial origin. Their bottoms are covered by different substrates and waters show a wide range of pH values varying from neutral to low alkaline types (Table 1). Bol'shoy Ngosavey Lake (Lake no. 9) is the only lake which is directly connected with the sea by a system of canals.

Sampling

Quantitative samples were collected with a Petersen dredge (two replicates from each point, sampling area 0.040 m2) and hydrobiological scraper with the blades' length 0.3 m. The Petersen dredge was used for the collection of material on soft substrates, a hydrobiological scraper was used for samples from hard substrates following the procedure of Shubina (1986). The scraper grasped the substrate 0.3 m down the bottom. The boulders in the shallow area of lakes were lifted manually and a 230 urn mesh size net was placed underneath them to prevent loss of organisms (Shubina 1986). For concentration of samples a kapron net with a mesh-size of 230 urn was used. Samples were preserved in ca. 4% formaline. The biomass of animals was estimated by applying length-weight relationships given by Balushkina and Winberg (1979), Naberezhny and Irmasheva (1980). The types of fine fractional substrate were determined roughly, without measuring the size of composing fractions. In order to determine the number of organisms per m2, the sampled area was estimated by measuring the area of projection per bottom of large stony elements. On average it was 176.3 ± 10.4 sm2 and 56.4 ± 5.6 sm2. According to linear dimensions of the measured elements these substrates belong to the small boulders and large pebble (Ruhin 1953).

For the analysis of fauna distribution the data concerning species distributions were gathered from literature (Borutsky 1952; Baranovskaya 1978; Run-die et al. 2000). The data on ways of locomotion and feeding of crustaceans from literature (Rylov 1948; Smirnov 1976; Monakov 1976, 1998; Chuykov 1981; Sarvala 1998) were used.

Data analyses

Differences in biomass of microcrustacean groups among different biotopes were tested using the Kolmogorov-Smirnov nonparametric test (Statistica 6.0 2001). The significance level was set at P < 0.05. The association between micro-benlhic crustacean biomass and environmental parameters was investigated with canonical correspondence analysis followed by Monte Carlo tests and cluster analysis with Euclidean distance measure and Ward's group linkage method using PC-ORD for Windows (McCune and Mefford 1999). In the statistical analysis the sizes of elements of the substrates in arbitrary units were used. Among the qualitative characteristics its hardness and the pres­ence or absence of visually distinguishable plants was taken into account. All mineral substrates except soft sands and clay were considered to be hard substrates; silts, clays, and soft sands were considered to be soft substrates (Konstantinov 1979).

Results

Zoogeographical characteristics of crustacean fauna

In the studied lakes of the Bol'shezemel'skaya tundra 58 crustacean species were found: 30 species of Cladocera and 28 species and subspecies of Cope-poda. The biomasses of Ostracoda were low and were not classified onto the species level. About 30 crustacean species were recorded in the Western part of the region while 47 species were recorded in the Eastern part. For the first time Microsetella norvegica (Boeck 1864) was found in Bol'shezemel'skaya tundra (Lake Bol'shoy Ngosavey). Nine species of Cladocera and nine species of Copepoda were recorded in both regions. The majority of the species which we encountered are only present in specific types of lakes (Table 2). They appear to be the most common representatives of the limnofauna and cover very vast areas: cosmopolitan (five species), in almost all climatic zones of the Holarctic (six species) or the Palearctic (two species) and in the tundra and taiga zones of the Palaearctic (four species).

Three haipacticoid forms: Canthocamptus glacial-is Lilljeborg, 1902 from the lake Bol'shoy Ngosovey,

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Arcticocamptus krochini Borutsky, 1951 from the lakes Komaty and Bol'shoy Ngosovey, and Bryo-camptus zschokkei komi Borutsky, 1962 from the lake Bol'shoy Kharbey were specific for the fauna of the Eastern group of lakes.

A low number of Arcticocamptus cuspidatus (Schmeil 1893) were found only in the Western part of the Bol'sliezemel'skaya tundra in a small creek feeding into lake. The basin of the Ortina River appeared to be the extreme eastern location for this European Palaearctic harpacticoid species.

Ecological characteristics of crustacean fauna

About 14 species of Cladocera and nine species of Copepoda from the benthos samples belonged to the euplanktonic group. Six species are defined by the characteristics of different habitat conditions. Can-thocamptus staphylinus (Jurine 1820), C. glacialis, Br. z. komi, A. krochini are limnophilic. The rest of the species with an exception of Arcticocamptus arcticus (Lilljeborg 1902) are eurytopic. Microsetella norvegica is halophilic and the rest of species are freshwater. A. arcticus is acidophilic. Halophilic and acidophilic species were rare in the investigated water bodies. Halophilic M. norvegica occurred together with freshwater species in Lake 12 (Table 2). Acidophilic species were found in the littoral zone of Lake 9.

On basis of their way of locomotion the micro-crustaceans can be grouped into five categories: (1) crawlers and burrowers, (2) crawlers and swimmers, (3) crawlers, swimmers, and burrowers, (4) burrow­ers, and (5) swimmers attached to substrate (Table 2). Swimming and attaching to substrate (Sida and Simocephalus) were found only in the eastern studied lakes. The other categories were found in both region. Cladocerans of different ecological types occurred on different depths and substrates in the undergrowths of macrophytes or without macrophytes (Table 2). Large species of Cyclopoida are capable to swim and creep well; small ones can swim, creep, and bury themselves in substrate. In the comparatively large glacial lakes 9 and 11 all ecological types of crustaceans were found (Table 2). On basis of their feeding mode we could distinguish four ecological groups: (1) primary filter feeders, (2) secondary filter feeders and gatherers, (3) raptorial feeders, and (4) gatherers.

Biomass distribution of benthic crustaceans in lakes

Biomass values of bottom crustaceans in the researched lakes varied from 29 ± 11 mg wet wt m~2 in Lake 3 up to 500 ± 360 mg m2 in Lake 11 (Komaty). In the lakes of the western part of Bol'shezemerskaya tundra biomass appeared to be the biggest in the Lake 8: 210 ± 9 mg nT2 (Fig. 2A).

The total abundance of crustaceans varied from lake to lake similar to the variation of their biomass: the highest densities were registered in the Lake 11 (Komaty): 12,700 ± 7,600 ind. m^2, the smallest—for the lake 5: 1,400 ± 467 ind. m~2. In terms of numbers Cladocera or Cyclopoida were generally most numer­ous, but in Lakes 11 and 12 Harpacticoida were the most abundant microcrustaceans. However, by bio­mass the last group didn't prevail in any lakes because of small sizes of individuals (Fig. 2B).

The Kholmogorov-Smirnov test did not show significant differences in taxonomic composition (biomass) and in majority of cases in ecological composition among lakes (P < 0.05). The significant differences were between biomass of crawlers and burrowers in B. Kharbey and Lake 8, of raptorial feeders in B. Kharbey too and B. Ngosavey and of secondary filter feeders and gatherers in B. Ngosavey and Lake 4 (P < 0.05).

Among all the lakes of the eastern part of Bol'shezemerskaya tundra canonical correspondence analysis was applied to the data. Classification of the environmental conditions in the Kharbey lakes had shown that the axis 1 is the one that very closely connected with all viewed factors: substrate particle size, its hardness, depth, and station, presence of biofilm on the substrate, and the temperature of water (Figs. 3A, 4A-C). All this conditions correlated with each other and significant correlated with axis 1 according to Monte Carlo test (P = 0.02). The interdependence between the changes of the environ­mental factors and species' biomass had been also stated (Table 3). Even though the distinctive value and the size of gradients are higher for axis 1, axis 3 also shows considerable and important gradients of the data difference (P = 0.01). This indicates the existence of additional not uncovered factors of impact on the distribution of species' biomass. Cluster analysis revealed two major groups and a number of smaller groups of species with the similar

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Fif>. 2 Absolute biomass (mg wet wt m ") and biomass composition (%) of micro-benthic invertebrates in the 12 study lakes: A = absolute biomass of four main taxa. B = biomass composition of the main four taxa, C = biomass composition of the five type of locomotion behavior groups, D = biomass composition of the five feeding groups. Numbers refer to Lake numbers (see Table 1)

distribution of biomass in the bottom substrates of the Kharbey Lakes (Fig. 5A). The composition of groups appeared to be taxonomically and ecologically the most diverse. One of these groups is comprised of the species (S. crystalline, M. duthiei, Br. z. komi, Ch. sphaericus, M. viridis), whose biomass correlated with the axis 1 in canonical correspondence analysis and their scores had the similar direction with the vectors, describing the substrate quality (Table 3). Biomass of A. elongatus, Eucyclops sp., M. schmeili, and Cyclopoida juv. also similarly distributed along the axis 1 (Table 3). Species from group 3 (Fig. 5A) didn't show similar dependence on the factors, used in the canonical correspondence analysis.

In the lakes 1-8 the majority of the studied factors of the environment had correlated with the axis 2 as well as between each other (Figs. 3B, 4D-F) except

for the size of substratum elements, which was more closely connected with the axis 3 (Table 4). Test Monte Carlo for canonical correspondence analysis showed the reliability of dependence of species' biomass with the variables along the axis 3. Cluster analysis disclosed three groups of microcrustaceans in the small lakes of the western part of Bol'sheze-mel'skaya tundra (Fig. 5B). Taxonomic and ecolog­ical composition of the clusters' groups and sub­groups is heterogeneous even in the groups and sub­groups comprised of two or three species. Species' biomass in one of the clusters (P. schmeili, ... Cyclopoida juveniles) correlated with the axis in the canonical correspondence analysis (Table 4).

Multiple analysis of relationship of the environ­mental factors (station and substrate particle size) and total ecological groups' biomass have shown not

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Conclusions

Microcrustaceans in the benthos of studied lakes of Bol'shezemel'skaya tundra are represented by Clado-cera, Copepoda, and Ostacoda. Cladocera and Cope-poda prevail numerically and in biomass. Zoogeographical analysis of data on these taxa did not change the existent opinion on the fauna of the majority of crustacean groups (Cladocera, Cyclopo-ida, Calanoida) of Bol'shezemel'skaya tundra as of palaearctic with the elements of arctic. Along with circumpolar and palaearctic species European and Siberian species were revealed in the fauna of Harpaclicoida.

Biomass of microcrustaceans was distributed in the bottom communities due to the quality of substratum (size of its elements, hardness), depth, and habitat (inshores vs. offshore). In the deep-water lakes dependences in distribution of biomass was more evident. In the shallow tundra lakes the structure of the bottom crustacean communities was regulated by other environmental factors. In the deeper water bodies the quality of substratum had an influence on the biomass of burrowers and on species of other ecological groups. Clusters had very diverse ecological and systematic composition. Similar dis­tribution of biomasses of species from these clusters in some cases can be a result of food interrelations between predator and its prey.

Acknowledgments This research was supported by grant from the Russian Foundation for Basic Research (RFBR) No. 98-04-50007-a, the international projects "Sustainable development of the Pechora region in a changing Society and Environment"—SPICE (contract EC No. ICA2-CT-2000-10018) and "Pechora River Basin Integrated System Management" (PRISM) 2003-2005. We thank our colleague Vasily I. Ponomarev for samples and data about lakes 1-8 kindly given. We wish to thank also Anna Loskutova for help in translation and Vivienne Jones for kindly checking the English of the manuscript. We are grateful to three anonymous reviewers for their valuable comments and suggestions on an earlier draft of this article.

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