Hydrobiologia (2010) 651:185–197 DOI 10.1007/s10750-010-0295-7 PRIMARY RESEARCH PAPER Similar distribution pattern of different phenotypes of Limnocythere inopinata (Baird) in a brackish-water lake in Inner Mongolia Dayou Zhai • Jule Xiao • Lang Zhou • Ruilin Wen • Zhigang Chang • Qiqing Pang Received: 11 December 2009 / Revised: 28 April 2010 / Accepted: 3 May 2010 / Published online: 20 May 2010 Ó Springer Science+Business Media B.V. 2010 Abstract It has been recognized long ago that their maximum abundances in the intermediate zone Limnocythere inopinata is a widely distributed of the lake. All the phenotypes of L. inopinata ostracod and comprises various phenotypes. The display a similar preference for water depth and taxonomy of the different phenotypes and their substrate, implying that the occurrence of different ecological differences, however, are still under phenotypes is controlled by other factors. The age debate. In this study, we investigated the relationships structure of L. inopinata is mainly related to the sand between ostracod distribution, water depth, and the content, with the percentage of adults increasing and substrate based on the analyses of species composi- that of early juveniles decreasing with increasing tion, abundance, and age structure of ostracods in 51 sand content. Our data suggest that the occurrence of surface-sediment samples from Dali Lake in Inner L. inopinata is closely related to water depth and Mongolia in order to reveal the distribution pattern substrate grain size, and different phenotypes of and habitat characteristics of the ostracods. The L. inopinata respond in a similar pattern to water identification of a total of 32,182 valves indicates that depth and substrate. the dominant ostracod in Dali Lake is L. inopinata, which includes unnoded, 1-, 2- and 3-node and Keywords Dali Lake Á Surface sediment Á 1-carina phenotypes. The distribution of L. inopinata Ostracod Á Water depth Á Substrate is affected both by the water depth and by the sand content of the substrate, and the phenotypes show Introduction Ostracods, micro-crustaceans with calcite shells, usu- Handling editor: S. A. Halse ally colonize the bottom of oceans, lakes, swamps, and D. Zhai (&) Á J. Xiao Á L. Zhou Á R. Wen Á Z. Chang ponds. They exuviate eight times during their life and Key Laboratory of Cenozoic Geology and Environment, leave their shells in the sediments (Holmes, 2001). The Institute of Geology and Geophysics, Chinese Academy occurrence of ostracods is closely related to the depth, of Sciences, 19 Beitucheng West Road, Chaoyang District, Beijing 100029, China temperature, salinity, and dissolved oxygen content of e-mail: [email protected] the water and the nature of the substrate (De Deckker, 1981;Benzie,1989;Holmes,2001), and the fossil shells Q. Pang thus provide ideal materials for studies of paleoenvi- College of Resources, Shijiazhuang University of Economics, 136 Huai’an East Road, Shijiazhuang 050031, ronmental variations (Chivas et al., 1986;DeDeckker& China Forester, 1988; Horne & Mezquita, 2008). 123 186 Hydrobiologia (2010) 651:185–197 It is essential to investigate the ecology of extant representative samples from the lake for establish- ostracods in order to reconstruct paleoenvironmental ment of the extant ostracod database of lakes in conditions based on analyses of fossil ostracods. A northern China. number of investigations have been made to docu- ment the relation between the feature of ostracods and the physical and chemical properties of the Study site ambient water (Ku¨lko¨ylu¨og˘lu, 2004; Bunbury & Gajewski, 2005; Viehberg, 2006; Mischke et al., Dali Lake (43°130–230 N, 116°290–450 E) is a closed- 2010). However, owing to the diversity of ostracods basin lake that lies 90 km west of Hexigten Banner, (Martens et al., 2008), and regional differences that Inner Mongolia (Fig. 1). It has an area of 238 km2,a may occur in the ecology of the same species across maximum water depth of 11 m, and an elevation of its range, our understanding of the response of 1226 m above sea level. The lake sits at the northern ostracods to different environmental factors can only margin of the W–E trending Hulandaga Desert Land be improved if we undertake detailed studies of the and is surrounded by hills of basaltic rocks to the morphology and age structure of single species in west, north, and east. Two permanent rivers from different lakes (Yin et al., 1999; Van Doninck et al., the northeast and two intermittent streams from the 2003). It is also important to examine concurrently southwest feed the lake. ostracod species assemblages in the same lakes Dali Lake is located at the transition from semi- (Martı´n-Rubio et al., 2005). humid to semi-arid areas in the middle temperate zone Several datasets of extant ostracods record the of China (Chinese Academy of Sciences, 1984). In the ostracod assemblage of different lakes (e.g., Mezq- lake region, mean annual temperature is 1–2°C with a uita et al., 2005; Bunbury & Gajewski, 2005; Forester July average of 16–18°C and a January average of et al., 2005; Viehberg, 2006; Mischke et al., 2007), -17 to -24°C. Mean annual precipitation is 350– and from some of the databases, transfer functions of 400 mm with 70% of the annual precipitation falling ostracod assemblages and environmental parameters in June–August. Mean annual evaporation reaches (mainly water salinity and temperature) were estab- 1287 mm (Li, 1993). The lake is covered with ca. 1 m lished for quantitative paleoenvironmental recon- of ice from November to April (Li, 1993). structions. It should be noted, however, that some The modern natural vegetation of the Dali Lake datasets contain the ostracod assemblage recorded in region is categorized as temperate steppe and domi- a single sample from one lake. In reality the nated by grasses (Li, 1993). Herbs of Stipa grandis, assemblages may be significantly different in differ- Leymus chinensis, and Cleistogenes squarrosa are ent positions of a lake (Benzie, 1989; Martı´n-Rubio distributed in the grasslands on the hills. Xeric plants of et al., 2005), implying that not any sample could be Artemisia desterorum, Polygonum divaricatum, and used to represent the ostracod assemblage of indi- Agriophyllum squarrosum grow in the Hulandaga vidual lakes. Therefore, the establishment of a high- Desert Land, accompanied by small patches of shrubs quality database of extant ostracods needs a proper of Salix gordeivii, Ulmus pumila, and Caragana sinica. selection of the representative samples based on The water of Dali Lake has a pH of 9.5 and a investigations of the within-lake distribution of salinity of 5.6 g l-1 with major cations of Na? ? K? ostracods in individual lakes. (97.4%), Mg2? (2.3%), and Ca2? (0.3%) and major - - 2- In this study, 51 samples of the surface sediments anions of Cl (40.1%), HCO3 (31.7%), CO3 2- of Dali Lake in central eastern Inner Mongolia were (21.8%), and SO4 (6.4%) (Li, 1993). Aquatic plants analyzed for ostracod assemblage, age structure of are scarce in the lake and confined to the areas of the the dominant ostracod, and grain size. We attempt to river mouth. The benthic fauna of the lake consists investigate the spatial distribution of ostracods in the mainly of Gastropoda, Oligochaeta, Crustacea, and lake and then examine the relation between the Insecta, and most of these animals inhabit the near- ostracod assemblage and environmental factors. This shore zone (Li, 1993). study provides basic data both for understanding The lake region is sparsely populated. Local paleoenvironmental processes through the sedimen- people are engaged in animal husbandry and do not tary sequence of Dali Lake and for selecting undertake any agricultural activity. A fishery unit was 123 Hydrobiologia (2010) 651:185–197 187 Fig. 1 Map of Dali Lake 116 30 116 45 showing sites of 51 samples Fishery Headquarters from the surface sediments. Capital letters with numerals mark the sample + Dali Gongger River numbers. Solid, half-solid, A9 and hollow circles indicate A6 A7 A8 China the total abundance of ostracods in the samples. B6 B7 B8 Dashed lines with numerals 43 20 C5 C6 C7 C8 represent the bathymetry of –1 Sa the lake (contour in meters) <1000 v g D5 D6 D7 D8 D9 lin River 1000–10,000 v g–1 E4 E5 E6 E7 E8 E9 >10,000 v g–1 F4 F5 F6 F7 F8 F9 3 1 7 5 11 9 G2 G3 G4 G5 G6 G7 G8 G9 Hola i Ri 43 15 ver H2 H3 H4 H5 H6 H7 H8 H9 K1 K2 K3 K4 K5 K6 K7 BORHAN HILL er Riv 0 5 km gzi Lian set up on the lakeshore (Fig. 1) in 1956 to organize Ostracod analysis fishery production. Fishery management activities have been carried out in winter since the 1970s to For each sample of ca. 100 mg of air-dried sediment, protect fish resources (Li, 1993). 60 ml of 10% H2O2–0.1% Na2CO3 solution (pH 9–10) was added to disaggregate the sediment for 24 h. The resulting residue was sieved in water through a Materials and methods 250-mesh sieve with a pore size of 63 lm. The remains of the sample were rinsed repeatedly and Surface-sediment sampling spread onto a glass plate (9 cm 9 12 cm) as thin stripes with a buret (4-mm inner-caliber) and then The surface sediments of Dali Lake were sampled at dried in an oven at 40°C. All the ostracod shells intervals of 1 min of latitude (equivalent to 1.9 km) including both living and dead individuals in the and 1.5 min of longitude (equivalent to 2 km) sample were identified and counted with an Olympus (Fig.