ARTICLE IN PRESS Limnologica 38 (2008) 116–125 www.elsevier.de/limno Macrozoobenthic community of Fuxian Lake, the deepest lake of southwest China Yong-De Cuia,b, Xue-Qin Liua, Hong-Zhu Wanga,Ã aState Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China bGraduate School of Chinese Academy of Sciences, Beijing 100049, China Received 14 September 2006; received in revised form 7 September 2007; accepted 26 October 2007 Abstract Located in the Yunnan–Guizhou Plateau in southwest China, Fuxian Lake covers an area of 211 km2, with maximum depth of 155 m. It is known to have a unique fauna, including 14 described endemic species. In order to describe the zoobenthic community of the lake more completely, the present study was conducted from August 2002 to August 2003. Altogether 62 benthic taxa, including 22 oligochaetes, 21 molluscs and 18 insects were identified, of which the dominant taxa belonged to Potamothrix, Procladius and Paraprososthenia. The standing stocks of benthos were much higher in the littoral (824 ind/m2 in density, 3.72 g/m2 in biomass) than in the profundal region (23 ind/m2 in density, 0.10 g/m2 in biomass). Species richness was greatest in summer and standing stocks were larger in spring and summer than in other seasons. Analyses of functional feeding groups indicated that collector-gatherers and scrapers were predominant in entire lake. Stepwise multiple regression analysis demonstrated that the water depth is the most important factor affecting the distribution of macrozoobenthos. r 2008 Elsevier GmbH. All rights reserved. Keywords: Macrozoobenthos; Taxonomic composition; Standing crop; Functional feeding group; Fuxian Lake Introduction 2006; Liang and Liu, 1995; Xu et al., 2003), but little attention has been paid to Chinese deep lakes so far. Macrozoobenthos plays an important role in linking Located in the Yunnan–Guizhou Plateau in south- detrital deposits and higher trophic levels in lake west China, Fuxian Lake (E 1021490–570,N241170–370) ecosystems (Brinkhurst, 1974; Hanson and Peters, is the deepest lake in the above area. This tectonic lake is 1984). This group has been extensively studied in known to have a unique fauna, including 14 endemic Euro-American deep lakes (Ambrosetti and Barbanti, species described to date (Cui and Wang, 2005; Sket, 2001; Barton, 2004; Dermott and Kerec, 1997; Grigor- 2000; Yang and Chen, 1995). However, previous works ovich et al., 2003; Kravtsova et al., 2004; Lozano et al., on macrozoobenthos in this lake were chiefly concen- 2001; Martin et al., 1999; Nalepa et al., 2003; Nocentini trated on these uncommon findings (Liu et al., 1980; et al., 2001; Snimschikova and Akinshina, 1994), and Sket, 2000; Wang, 1988); a study covering entire benthic Chinese shallow lakes (Chen et al., 1980; Jiang et al., community is still lacking. In 2002–2003, an investigation of macrobenthos in ÃCorresponding author. Tel./fax: +86 27 68780719. Fuxian Lake was carried out as a part of a project on the E-mail address: [email protected] (H.-Z. Wang). biological limnology of Plateau Lakes. The results, 0075-9511/$ - see front matter r 2008 Elsevier GmbH. All rights reserved. doi:10.1016/j.limno.2007.10.003 ARTICLE IN PRESS Y.-D. Cui et al. / Limnologica 38 (2008) 116–125 117 including community structure, characteristics of the 14.270.1 1C, respectively. Mean thermocline (H)islocated macrofauna, seasonal changes and environmental para- at a depth of 22.4 m. Dissolved oxygen in water above 50 m meters, are dealt with in the present paper. A new is7mgLÀ1 and gradually decreases with increasing depth endemic species found during the work was described to0.8mgLÀ1 at the bottom. The lake is oligo-mesotrophic. previously (Cui and Wang, 2005). Aquatic macrophytes cover less than 0.1% of the bottom. Lake sediments are mainly clay and sand clay (Nanjing Institute of Geography and Limnology, 1990). Study area and methods Fourteen sampling stations (ST) were set up in the lake (Fig. 1). They were grouped by depth into three Formed by faulting in the late Pliocene (3.0–4.0 Ma), zones: Zone I (depth (Z)o50 m, including ST3, 11 and Fuxian Lake is one of the characteristic tectonic lakes of 13), Zone II (Z ¼ 50–100 m, including ST1, 2, 6, 8, 9, 10, Yunnan–Guizhou Plateau. It covers an area of 211 km2 at 12 and 14); and Zone III (Z4100 m, including ST4, 5 a water level of 1721 m a.s.l., with maximum length of and 7). Physico-chemical properties of the three zones 31.5 km, and maximum width of 11.5 km. The maximum are summarized in Table 1. depth is 155 m and the average depth is 87 m. Shoreline Sampling was carried out bimonthly from August development (D )equals1.72(Fig. 1). The climate is warm 2002 to August 2003. Benthic samples were collected by L 2 and wet. Annual mean air temperature around lake area is a weighted Peterson sampler (0.08 m ), and cleaned 15.6 1C. Mean annual precipitation is 942.4 mm (84% gently with a 250 mm sieve. Animals were sorted under a occurring in May–October), and mean evaporation is dissecting microscope and preserved in 10% formalin. 1400 mm. The lake receives surface runoff from the All specimens were identified to species or genus level catchment (1044.6 km2) through many streamlets. It also whenever possible, based on the keys in Brinkhurst and receives water from a eutrophic lake in the south and Jamieson (1971), Epler (2001), Liu et al., (1979), Morse discharges into Nanpanjiang River through Haikou River et al., (1994), Sperber (1948) and Wang (2002). in the east. Annual mean temperatures of lake water in Animals were mainly identified to species or genus. upper and bottom layers are 19.171.2 1C (SE) and All taxa were assigned to functional feeding groups (shredders, collector-gatherers, collector-filterers, scra- pers and predators) according to Morse et al., (1994) and Liang and Wang (1999), or by direct examination of their gut contents. When a taxon has several possible feeding activities, its functional designations were equally proportioned. Wet biomass of larger animals was determined with an electronic weigher after being blotted (molluscan shells retained), while that of smaller worms was calculated from length (L)–weight (W) relationship formula (W ¼ aLb; see Yan, 1998). Statistic 6.0 was used for one-way ANOVA analyses. Standing stocks were compared among zones using Unequal N HSD Test after one-way ANOVA. Jaccard coefficient (Sj) was applied to compare the compositions of benthic communities between Fuxian Lake and other lakes (Wu and Liang, 1999): c S ¼ , j ða þ b À cÞ where a is the number of species in community A, b is the number of species in community B, and c is the number of species common to both communities. Results Community structure Species composition Fig. 1. Sampling stations in Fuxian Lake (B) and its location Altogether 62 taxa belonging to 13 families and in China (A). Dashed lines show isobaths. 46 genera were identified from quantitative samples. ARTICLE IN PRESS 118 Y.-D. Cui et al. / Limnologica 38 (2008) 116–125 Table 1. Physico-chemical parameters of sampling zones in Fuxian Lake (mean7SE) Parameters Zone I Zone II Zone III Entire lake Water depth (m) 37.174.3 83.074.1 122.8712.7 81.878.5 Secchi depth (m) 6.770.2 7.170.2 7.470.1 7.170.1 Temperature (1C) Upper 19.672.0 19.471.8 18.970.8 19.171.2 Bottom 17.270.7 14.670.2 14.470.1 14.270.1 pH 8.970.05 8.870.03 8.770.20 8.870.04 Conductivity (mS/cm) 29.870.20 30.070.28 29.170.50 29.270.21 Chlorophyll a (mg/L) 2.470.24 2.170.05 2.070.11 2.270.06 Total nitrogen (mg/L) 0.20470.003 0.19970.005 0.18870.001 0.19870.003 Total phosphorus (mg/L) 0.02270.000 0.02170.000 0.02270.001 0.02170.000 Among them were 22 species of oligochaetes, 21 species and Procladius, comprising 49.6% and 29.8% in density, of molluscs and 18 species of aquatic insects (Table 2). and 49.4% and 13.3% in biomass, respectively. Although the numbers of species were the same in Zone I and Zone II (47), the species composition was Functional structure different, i.e. more molluscan species occurred in the former region. Only nine species were found in Zone III. The relative abundances of five functional feeding Among oligochaete species, Potamothrix scleropenis is groups are shown in Fig. 3. Collector-gatherers and endemic (Cui and Wang, 2005), and the specific scrapers were predominant in entire lake, respectively identities of another six, Potamothrix sp.1, Potamothrix comprising 48.7% and 30.6% in number of species, sp.2, Potamothrix sp.3, Tubificinae gen. sp.1, Tubifici- 44.8% and 32.1% in density, and 12.2% and 52.9% in nae gen. sp.2, and Tubificinae (?) gen. sp., are still in biomass. Zone I had more scrapers than collector- doubt. Their taxonomic position and geographic dis- filterers or predators as compared with that in Zone II, tribution need further study. although the total species numbers in both zones were equal. The relative abundance of collector-gatherers in Body size Zone III was higher than that in other zones, but the 7 Mean body length of oligochaetes was 10.2 0.85 mm absolute values of all groups in this zone were very low. (SE), mean shell height of gastropods was 5.270.22 mm, mean shell length of bivalve was 3.671.05 mm, and Seasonal dynamics mean body length of insect larvae was 5.370.26 mm.