10 Acta Zoologica Lituanica, 2004, Volumen 14, Numerus 3 ISSN 1392-1657 SPECIES COMPOSITION OF MACROINVERTEBRATES IN MEDIUM-SIZED LITHUANIAN RIVERS Virginija PLIÛRAITË, Vytautas KESMINAS Institute of Ecology of Vilnius University, Akademijos 2, LT-08412 Vilnius-21, Lithuania. E-mail: [email protected], [email protected] Abstract. The article is devoted to the analysis of the taxonomic composition of macroinvertebrates in 17 medium-sized Lithuanian rivers with different kinds of substrata. One hundred and sixty taxa of invertebrates were identified in the course of the study. The obtained results proved that in the same river the number of taxa and Shannon-Weavers index of diversity are substratum type dependent. The greatest number of taxa was established in the stone substratum while the smallest was recorded in the sand one. The richest biodiversity and the highest Shannon-Weavers index in the stone substratum were recorded in the Jiesia River. Rivers with increased organic contamination were dominated by Trichoptera of the genus Hydropsyche. Key words: macroinvertebrate, species richness, medium-sized rivers INTRODUCTION (1959, 1960, 1962) conducted a comprehensive study of the species composition of stoneflies, caddisflies, may- In streams, species richness of macroinvertebrates is flies in the Perðokðna and Mera Rivers and that of may- affected by a large number of biological (Feminella & flies in the Verknë, Ûla-Pelesa Rivers. There were Resh 1990) and environmental factors (Voelz & seven species of caddisflies recorded in the Perðëkë McArthur 2000), such as environmental stability (Ward River by Spuris (1969). The occurrence of stonefly, cad- & Stanford 1979). Species richness of aquatic inverte- disfly, mayfly species in the Eþerëlë, Jiesia, Lakaja, Lû- brates is also strongly influenced by natural and/or an- ðis, Siesartis (Ðeðupë), Ðerkðnë Rivers was not reported. thropogenic disturbance (Rosenberg & Resh 1993), The aim of the current study has been to establish the which may lead to spatial discontinuities in predictable species composition and diversity of macroinvertebrates gradients (Ward & Stanford 1983) and losses of taxa in medium-sized Lithuanian rivers with different kinds (Brittain & Saltveit 1989). Resh and Jackson (1993) of substrata. noted that species richness is susceptible to the impact of human activities on stream ecosystems, particularly on aquatic insects of the orders Ephemeroptera, MATERIAL AND METHODS Trichoptera or Plecoptera, which are often good indica- tors of environmental conditions in streams. The investigations were performed in summer 1998 Aquatic insects such as Ephemeroptera, Plecoptera, 2002 in 17 medium-sized rivers: the Armona, Eþerëlë, Trichoptera, Coleoptera (EPTC) are known to be pollu- Jiesia, Lakaja, Lûðis, Mera, Perðëkë, Perðokðna, Siesar- tion-sensitive (Hynes 1957). Cayrou et al. (2000) tis (Ðeðupë), Spengla, Ðerkðnë, Ðirvinta, Verseka, showed the pertinence of EPTC species associations for Verknë, Vilnia, Virinta, Ûla-Pelesa. The presence of the stream classifications. Wallace et al. (1996) noticed that stone substratum, noted for higher species richness, was species richness of Ephemeroptera, Plecoptera, taken into consideration when selecting rivers for the Trichoptera actually responds to variations in water investigation. quality. Data on species richness of macrozoobenthos in me- Description of sites dium-sized Lithuanian rivers are not abundant. Kazlaus- kas (1959, 1960, 1962) investigated stoneflies (Plecop- There are about 29.9 thousand streams (longer than tera), caddisflies (Trichoptera) and mayflies (Ephe- 0.5 km) with the total length of 63,700 km in Lithuania. meroptera) in different types of (medium-sized among Small rivers up to 10 km long make up approximately them) Lithuanian rivers. In his study he described their 97.5% of the total number of rivers or 77% of the total species, indicating their sampling locations. Kazlauskas length of riverbeds. 758 rivers and canals are longer than 11 Species composition of macroinvertebrates in medium-sized rivers 10 km, 19 of them being longer than 100 km and nine The majority of the investigated rivers were clean or longer than 200 km (Kilkus 1998). The rivers investi- cleanish (IIII class). According to the quality class of gated were classified as medium-sized in accordance with contamination the most contaminated rivers were the the EC Water Framework Directive (2000/60/EC). Jiesia, Siesartis, Perðëkë (IVV class; Table 2). In the course of sampling the water level in the investi- gated rivers with the stone substratum was 2540 cm Sampling methods and statistical analysis and 6070 cm in those with the gravel, sand-silt and sand substrata. At the moment of sampling the water in Samples of macrozoobenthos were taken with a stove- the rivers was unturbid. The character of anthropogenic pipe sampler (cylindrical tube) from the gravel, sand- pollution was not studied in the course of sampling. silt and sand substrata (Gasiûnas 1956). On study sites According to the classification of water contamination with the substrata of sand and stones 210 cm in diam- used in Lithuania the rivers were divided into six classes eter samples were dredged up from three 0.1 m2 areas in accordance with Water quality monitoring progra- (stone substratum) by the method of kick-sampling mme; Table 1. (NBWE 1993). Samples were also collected from plants: Table 1. Classification of river contamination used in Lithuania. Low Medium Highly Very Very Clean contami- contami- contami- highly con- clean nated nated nated taminated Quality class I II III IV V VI BDS5, mgO2/l <2.0 2.03.5 3.65.0 5.18.0 8.118.0 >18 Inorganic nitrogen, mg N/1 <0.3 0.30.75 0.82.5 2.67.5 7.615.0 >15 Phosphates, mg P/1 <0.025 0.0250.050 0.0550.125 0.1300.250 0.3000.500 >0.500 Table 2. Parameters of the investigated rivers. Area of the Average Water tem- Current River Name of river basin long-term perature in Sampling Quality velocity basin the affluent in Lithuania annual the course of dates class m/s km² yield m³/s sampling °C Spengla 148.3 1.00 0.28 17.2 July 1999 I Merkys Verseka 384.4 2.70 0.55 19.4 June 1998 I Ûla-Pelesa 752.9 5.50 0.35 17.0 July 1999 I Armona 218.9 1.40 0.30 21.0 July 1999 II Ðventoji Ðirvinta 918.1 6.50 0.40 21.0 July 1999 III Virinta 566.3 4.40 0.45 14.0 June 1998 II Lakaja 432.1 2.51 0.31 20.1 July 1999 I Þeimena Mera 204.4 1.90 0.40 16.5 July 1999 II Perðokðna 105.3 0.70 0.30 18.9 July 1999 I Lûðis 113.6 1.03 0.50 12.5 August 2001 II Venta Ðerkðnë 285.2 1.90 0.30 15.8 August 2001 III Jiesia 473.7 3.00 0.30 17.0 July 2002 IV Nemunas Perðëkë 561.8 2.50 0.50 20.0 August 2001 V Verknë 727.5 5.70 0.50 16.8 June 1998 III Neris Vilnia 623.5 5.50 0.50 20.5 July 2002 II Ðeðupë Siesartis 197.6 1.00 0.40 19.0 August 2001 IVV Mûða Eþerëlë 156.2 0.74 0.30 16.0 August 1998 II In Table 2 the river basin area is presented in accordance with Gailiuðis et al. (2001) 12 Pliûraitë V., Kesminas V. benthic fauna having been collected, plants were is recommended by Bloom (1981), Faith et al. (1987) weighed (phytophilic species), the abundance of and Jackson (1993). When applied to binary data the zoobenthos being calculated ind/1 kg of plants and the Bray-Curtis index is exactly equivalent to Sørensens biomass g/1 kg of plants. The more common plant index (Sørensen 1948). These similarities were calcu- species from which samples of macroinvertebrate were lated using the Cluster Program of the Primer package. collected in the investigated rivers included Elodea canadensis, Ceratophyllum demersum, Potamogeton spp. In total there were 117 samples gathered and RESULTS analysed in the laboratory by conventional methods employed in hydrobiology. Species composition of macroinvertebrates in inves- The following indices were calculated: Shannon- tigated medium-sized rivers Weavers diversity index (Shannon & Weaver 1949) and Sørensens similarity index (Sørensen 1948). In the course of the investigation performed in 17 me- Oligochaeta and Simuliidae were identified only to the dium-sized rivers in different districts of Lithuania family level and therefore were excluded from statisti- 160 taxa of macrozoobenthic organisms were identi- cal analyses when calculating indices. Mean ±SE and fied: Hirudinea 4 (2.5% of the total number of taxa), Students t-test was used for estimates of macroin- Isopoda 1 (0.6%), Amphipoda 1 (0.6%), Epheme- vertebrate abundance in the stone substratum of rivers. roptera 20 (12.5%), Plecoptera 6 (3.7%), Odonata Correlations were calculated according Pearson 2 (1.2%), Heteroptera 4 (2.5%), Coleoptera larvae (StatSoft 2001). Similarities in the abundance of taxa 4 (2.5%), Coleoptera imago 6 (3.7%), Megaloptera between invertebrate samples collected from the stone 1 (0.6%), Trichoptera 31 (19.4%), Lepidoptera substratum and plants were calculated using the Bray- 1 (0.6%), other Diptera 10 (6.2%), Chironomidae Curtis similarity measure (Bray & Curtis 1957), which 44 (27.5%), Mollusca 25 (15.6%; Table 3). Table 3. List of taxa of benthic macroinvertebrates in rivers. Family/ Group Taxon Subfamily Mera Lûðis Jiesia Vilnia Lakaja Virinta Verknë Eþerëlë Perðëkë Ðerkðnë Verseka Spengla Ðirvinta Armona Siesartis Perðokðna Ûla-Pelesa 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Oligochaeta + + + + + + + + + + + + + + + + + Hirudinea Glossiphonidae Glossiphonia ++ ++++ complanata (Linnaeus) Helobdella stagnalis ++++ ++ (Linnaeus) Erpobdellidae Erpobdella octoculata +++ + + ++++++ (Linnaeus) Pisciolidae Piscicola geometra ++ (Linnaeus)