13 1 Institute of Zoology, Bulgarian Academy of Sciences, 1 Tsar Osvoboditel Blvd., 1000 Sofia, Bulgaria; Fax: (3592) 9888-28-97; e-mail: mtodorov@zoology.bas.bg ACTA ZOOLOGICA BULGARICA Acta zool. bulg., 57 (1), 2005: 13-23 Testate Amoebae (Protozoa, Rhizopoda) of the Smradlivo Ezero Glacial Lake in the Rila National Park (Southwestern Bulgaria) Milcho Todorov 1 Abstract: The species diversity and the distribution of testate amoebae in different biotopes were investigated. A total of 86 taxa testaceans, belonging to 25 genera were recorded in 22 samples, collected from the benthos, the littoral zone and the wet coastal mosses of the Smradlivo Ezero - the biggest glacial lake in Bulgaria. The testacean taxocenoses in the lake studied are mainly composed of typical aquatic or sphagnophilous species of the genera Difflugia (21 taxa), Euglypha (10), Centropyxis (9) and Nebela (9), and the representatives of the genus Difflugia have a manifested predominance. The complexes of dominant species in the studied biotopes are rather different and include: T. lineare, C. aerophila, C. sylvatica, E. acanthophora (in littoral), D. viscidula, C. ecornis, D. oblonga, Z. compressa (in benthos), and E. ciliata, Q. symmetrica, Sph. fissirostris, T. lineare, D. elegans, M. patella, C. aerophila, C. ampulla, D. pulex (in coastal mosses). Furthermore, it was found out that the species diversity of the testacean fauna in the coastal mosses is two times bigger than that in the benthos, and three times greater than that in the littoral (74, 37 and 24 taxa, respectively). The comparison between the testacean fauna of the Smradlivo Ezero Lake and that of some well-studied glacial lakes in the Rila National Park, like the Ribni Ezera Lakes and the Sedemte Ezera Lakes, shows that there is not a big similarity between them (coefficients of faunal similarity of Jaccard are 48% and 57%, respectively). Key words: Rhizopodà, testate amoebae, ecology, glacial lakes, Rila National Park. Introduction The data about the testacean fauna of the glacial lakes in the Rila National Park are still very incomplete. The first studies on the testaceans of the glacial lakes in the Rila and Pirin Mountains were published by VALKANOV (1932, 1934 and 1938). These first investigations are not of ecological value, because the author has reported about the finding of many testaceans, without species identification or without the exact localities of the found species. Later, GOLEMANSKY, TODOROV (1993) investigated the testacean fauna of the littoral and watercatchment area of the Beli Iskar Dam and along with the testaceans of the dam they reported 7 testate amoebae from the hygropsammon of the Kanarsko Ezero Glacial Lake. More detailed investigations on the testaceans of the glacial lakes in the Rila National Park started by TODOROV, GOLEMANSKY 2000, TODOROV 2004. The authors studied the species diversity, distribution and dominant structure of testate amoebae in 14 different biotopes of 14 high-mountain glacial lakes in the Rila National Park, and recorded a total of 130 taxa of testaceans. These new data can be used in the future for the biomonitoring of the Rila National Park, still more in view of the increasing urban- ization of these until recently virgin regions, which with the building of the new ski-lifts are becoming much more accessible for the tourists. The present paper is part of a series dealing with testaceans of the glacial lakes in the Rila National Park, and concerns the species diversity, biotopic distribution and dominant structure of testacean communities in the Smradlivo Ezero Lake. Material and Methods The studied Smradlivo Ezero Lake is the biggest of the glacial lakes in Bulgaria. It is situated at 2294 m a.s.l. in a glacial circus in the Middle Rila. Its top area is 212 dca and volume is 1720 x 10 3 m 3 . The maximum length is 800 m, maximum width - 375 m, maximum depth - 24 m and average depth - 8.1 m. The main water supply comes from the small stream on the southern side of the lake, and at a lower degree from the Sphagnum bogs near the lake. The chemical analyses of water show a very low level of total mineralization, which ranges from 35.0 mg/l on the surface to 50.0 mg/l at a depth of 10 m. Among the ion ingredients hydrocarbonate ions (from 15.2 mg/l to 21.3 mg/l) prevail, compared with natrium, sulphate, chlorine and magnesium ions, the amount of which is lower. The permanganate oxidability is not more than 2.1 mg O/l and the total iron content is low and does not exceed 0.73 mg/l. The water reaction is neutral and the total hardness of water ranges from 0.59 to 1.51 dH 0 , i.e. it is very soft (IVANOV et al. 1964). The materials for the present investigation were collected in September 2002. A total of 22 samples from three different biotopes of the studied lake were treated. All samples were fixed in situ with 4% formol. The locations of the sampling sites are given in Fig. 1. The materials were collected from the following 3 biotopes: (1) Littoral zone of the lake - washed emersed and submerged vegetation (Ranun- culus aquatilis var. riloense, Sparganium affine, Graminea sp.) and benthic samples at a depth up to 1.5 m (6 samples, 1-6); (2) Benthic samples at a depth from 5 to 18 m (8 samples, 7-14); (3) Wet mosses (mainly Sphagnum sp.) from the coastal zone of the lakes (8 samples, 15-22). Eckmanns grab was used for the collection of the benthic samples. The relative abundance of each species was used to determine the dominant structure of testacean communities. The abundance was registered by a five-level scale with conventional signs: cc  abundant, c  often, + - average, r  rare, rr  very rare. The dominance frequency (DF) was calculated by the formula: DF = (md/n) . 100, where md is the number of samples in which a given species dominates (the dominants are the species which take the first two places as regards their abundance - cc and c) and n is the total number of samples. The frequency of occurrence (pF) of the particular species was calculated by the formula: pF = (m/n). 100 ,