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NAT. CROAT. VOL. 18 No 1 49–82 ZAGREB June 30, 2009

original scientific paper / izvorni znanstveni rad

COMPOSITION AND STRUCTURE OF BENTHIC MACROINVERTEBRATE COMMUNITIES IN THE MEDITERRANEAN KARST RIVER THE AND ITS TRIBUTARY THE RUDA,

IVAN VU^KOVI]1,IVANA BO@AK2,MARIJA IVKOVI]3,MIRJANA JELEN^I]3, MLADEN KEROVEC3,ALEKSANDAR POPIJA^3,ANA PREVI[I]3, SINI[A [IRAC1,IVONA ZRINSKI4 &MLADEN KU^INI]3*

1Hrvatske vode, Central Water Management Laboratory, Ulica grada Vukovara 220, HR-10000 Zagreb, Croatia 2Vari}akova 14, HR-10000 Zagreb, Croatia 3Department of Biology, Faculty of Science, University of Zagreb, Rooseveltov trg 6, HR-10000 Zagreb, Croatia 4Croatian Environment Agency, Inland Water and Marine Unit, Ksaver 208, HR-10000 Zagreb, Croatia

Vu~kovi}, I., Bo`ak, I., Ivkovi}, M., Jelen~i}, M., Kerovec, M., Popija~, A., Previ{i}, A., [irac, S., Zrinski I., Ku~ini}, M.: Communities in the Mediterranean karst River the Cetina and its trib- utary the Ruda, Croatia. Nat. Croat., Vol. 18, No. 1., 49–82, 2009, Zagreb. Benthic invertebrate communities of the Cetina River and the upper reach of the Ruda River were sampled monthly at 11 sites from August 2004 to August 2005. The sampling sites were locat- ed along the longitudinal gradient of the Cetina and in the upper reach of the Cetina's largest trib- utary, the Ruda River. Throughout the study, a total of 310225 animals were collected in 366 sam- ples. In the upper and middle reaches the most numerous taxa were Amphipoda and Gastropoda, while the most numerous taxon in the lower reaches was Gastropoda. The highest and the lowest population density of benthic invertebrates were recorded at the sites Preo~ki Most in June 2005 (22728 individuals/m2) and Radmanove Mlinice in November 2004 (90 individuals/m2), respecti-

* Note: surname of authors in alphabetical order, except first and corresponding author

Croatian Natural History Museum, Demetrova 1, Zagreb, Croatia

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vely. At sites I and Trilj II, the most numerous taxa were Oligochaeta and Chironomidae, indi- cators of watercourses with higher organic loads. The composition of benthic invertebrate commu- nities at sites along the entire course of Cetina does not reflect the situation expected under natural conditions due to flow regulation and construction of hydroelectric power plants and reservoirs. Key words: physico-chemical parameters, macroinvertebrate community structure, Mediterra- nean karst river, regulated river

Vu~kovi}, I., Bo`ak, I., Ivkovi}, M., Jelen~i}, M., Kerovec, M., Popija~, A., Previ{i}, A., [irac, S., Zrinski I., Ku~ini}, M.: Sastav i struktura zajednica makrozoobentosa mediteranske kr{ke rijeke Cetine i njene pritoke Rude. Nat. Croat., Vol. 18, No. 1., 49–82, 2009, Zagreb. Istra`ivanje benti~kih beskralje`njaka rijeke Cetine i izvori{nog dijela toka rijeke Rude provedeno je u razdoblju od kolovoza 2004. do kolovoza 2005. godine. Cilj istra`ivanja bio je utvrditi sastav i strukturu benti~kih beskralje`njaka du` toka rijeke Cetine i izvori{nog dijela rijeke Rude. U razdoblju od 13 mjeseci u 366 uzoraka ukupno je prikupljeno 310225 jedinki benti~kih beskralje`njaka. Naj- brojnije su bile skupine Amphipoda i Gastropoda, i to u gornjem i srednjem dijelu toka, dok je u donjem dijelu toka najbrojnija skupina bila Gastropoda. Udio predstavnika ~istih voda iz skupina Plecoptera, Ephemeroptera i Trichoptera smanjivao se od izvora prema u{}u. Najve}a gusto}a ben- ti~kih beskralje`njaka bila je na gornjem dijelu toka, na postaji Preo~ki most u lipnju 2005. godine (22728 jedinki/m2), a najmanja na postaji na donjem dijelu toka, Radmanovim mlinicama, u stude- nom 2004. godine (90 jedinki/m2). Na postajama TriljIiTrilj II najzastupljenije su bile skupine Oligochaeta i Chironomidae koje su karakteristi~ne za organski optere}enije vodotoke. Uzrok tome je vjerojatno nerije{ena odvodnja otpadnih i komunalnih voda grada Trilja i okolnih podru~ja. Sastav zajednica makrozoobentosa na postajama du` cijelog toka rijeke Cetine ne `ava situaciju koju bismo o~ekivali u prirodnim uvjetima, zbog regulacije samog toka i izgradnje hidroelektrana i akumulacija. Klju~ne rije~i: fizikalno-kemijski parametri, sastav benti~kih beskralje`njaka, mediteranska kr{ka rijeka, regulirana rijeka

INTRODUCTION

Physical (e.g. structure of the substrate, temperature, light, water flow velocity, depth) and chemical properties (e.g. alkalinity, dissolved oxygen, pH value) of sur- face waters affect the composition and structure of invertebrate community inhabit- ing the riverbed, commonly known under the term macrozoobenthos. Stream and river communities also show high spatial and temporal variation in their structure and taxonomic composition over a different scale (BOYERO &BOSCH, 2002; BOYERO, 2003). The spatial density (density at particular sampling sites), spe- cies richness, taxonomic and functional composition of benthic invertebrates often show seasonal changes, reactions to torrents (MILLER &GOLLADAY, 1996) or leaf lit- ter availability (ABELHO &GRACA, 1998). Aquatic invertebrates are present in the lentic and lotic parts of the watercourse, with different adaptations to water tem- perature (@IVI] et al., 2006), pollution load (VIÐINSKIENË, 2005), water flow velocity and structure of the substrate (STATZNER et al., 1998). Since benthic organisms largely participate in the trophic relations, changes in their abundance and biomass considerably influence the quality of surface waters. Some benthic invertebrates are good indicators of organic water pollution, for in-

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stance, Oligochaeta and Syphiidae (Diptera) larvae. In general, high population density of above mentioned groups indicates high organic pollution (VIÐINSKIENË, 2005). However, the density and diversity of benthic organisms are influenced not only by organic pollution; there are other pressures, such as regulation of running water, habitat alteration etc. The Cetina River is regulated; there are five hydroelectric power plants in the river basin (HPP Peru~a, HPP \ale, HPP Kraljevac, HPP Zaku- ~ac and HPP Orlovac) and three reservoirs (Peru~a, \ale and Pran~evi}i). Overall, there are few studies dealing with the dynamics of benthic invertebrates in regulat- ed rivers; for instance WARD &STANFORD (1979) and later CRAIG &KEMPER (1987) studied the ecology of regulated streams and rivers. Croatia has a large number of regulated rivers, but there are few studies that ad- dress the issue. In the last few years a new approach to the study of different aspects of aquatic organisms has been applied in Croatia, mainly focusing on faunistics, ecology, tax- onomy and distribution of freshwater taxa (Boca et al., 2006; BUJ et al., 2008a; 2008b, DELI] et al., 2003, HABDIJA et al., 2002, 2004; IVKOVI] et al., 2007; IVKOVI] &HORVAT, 2007a, 2007b; KLOBU^AR et al., 2006 a, 2006 b, KU^INI] et al., 2008; LAJTNER et al., 2004; MAGUIRE et al., 2002, 2003, 2004; MALICKY et al., 2007; MATONI^KIN et al., 2001; MERDI] et al., 2005; MI^ETI] et al., 2008; MIHALJEVI] et al., 2004; MILI[A et al., 2006; MRAKOV^I] et al., 2000; MUSTAFI] et al., 2003, 2008; PEROVI] et al., 2006; PREVI[I] et al. 2007a; 2007b; SCHNEIDER et al., 2000; SKET et al., 2001; STANKOVI] &TERNJEJ, 2007; [POLJAR et al., 2005; TEMUNOVI] et al., 2007; TERNJEJ &STANKOVI], 2007). Studies focusing on the faunistics of invertebrates of the Cetina and Ruda rivers began during 2004 and have resulted in some important new data regarding the di- versity and distribution of Empididae (Diptera) (IVKOVI] &HORVAT, 2007; IVKOVI] et al. 2007), Neuroptera (RAUSCH &WEIßMAIR 2007) and taxonomy of caddisflies (Trichoptera) (GRAF et al. 2008; WARINGER et al. in press). However, the majority of animal taxa are still understudied. The aim of this study was to investigate the composition and structure of macro- invertebrate communities along the Cetina River and its tributary the Ruda. Since macroinvertebrate communities in permanent Mediterranean rivers are generally poorly investigated, our study represents an important contribution to the knowl- edge of their composition and structure.

RESEARCH AREA

The Mediterranean part of Croatia is characterized by numerous water flows, of which, in terms of fauna and ecology, the most significant are the , and Cetina rivers, with their smaller tributaries. This study was conducted in the area of the Cetina River, the longest Mediterranean river in Croatia, and its largest tributary the Ruda (Fig. 1). The length of the Cetina River is 106 km; its spring is located 50 km from the coast, and its mouth into the is located in the town of Omi{.

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Fig. 1. Map of research area showing location of sampling sites on the Cetina and Ruda rivers. Names and corresponding numerals of the sites are listed in Tab. 1.

MATERIAL AND METHODS

Physico-chemical parameters were measured and macrozoobenthos was sam- pled monthly, from 25 August 2004, to 27 August 2005, at 9 sites along the Cetina River and two additional sites at its tributary the Ruda River (Tab. 1, Fig. 1). The study encompassed a sampling site at one of the springs of the Cetina River (No. 1), two sites in the upper reach (Nos. 2 and 3), a site in the reservoir (No. 4), three sites in the middle reach (Nos. 5, 6 and 7) and two sites in the lower reach of the Cetina (Nos. 8 and 9). Additionally, the spring and upper reach of the Ruda River were sampled (Nos. 10 and 11).

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Tab. 1. List of sampling sites at the Cetina and Ruda rivers, showing geographic posi- tion and dominant substrate type for each site.

Sampling site GPS position Elevation Dominant substrate 1. Cetina Spring (Glavaš) N 43° 58' 36.1'' E 16° 25' 48.6'' 386 m gravel and sand, submersed vegetation 2. Preo~ki most N 43° 57' 59'' E 16° 25' 53'' 371 m sand 3. Crveni most N 43° 57' 35.7'' E 16° 25' 46.6'' 367 m gravel, sand 4. Peru~a reservior N 43° 51' 02.7'' E 16° 37' 24.3'' 350 m sand 5. Obrovac Sinjski N 43° 40' 01.4'' E 16° 41' 04.7'' 301 m cobbles of 5–10 cm, boulders covered in green algae 6. Trilj I N 43° 36' 49.8'' E 16° 43' 49.2'' 297 m sand, silt 7. Trilj II N 43° 36' 21.1'' E 16° 43' 46.2'' 296 m sand, silt 8. ^ikotina La|a N 43° 31' 58.4'' E 16° 44' 42.3'' 236 m pebbles, pebbles covered in moss 9. Radmanove Mlinice N 43° 26' 16.2'' E 16° 45' 11.3'' 15 m pebbles , moss 10. Ruda Spring N 43° 40' 07.1'' E 16° 47' 56'' 320 m boulders, pebbles , moss 11. Ruda II N 43° 40' 07.5'' E 16° 47' 49.2'' 308 m pebbles , boulders

The following physico-chemical parameters of water were measured in the field: pH value (with the WTW ph 330 pH-meter); concentration of dissolved oxygen and water temperature (with the WTW Oxi 330/SET oximeter); electrical conductiv- ity (with the WTW LF 330 conductivity meter) and alkalinity (by titration with 0.1 M HCl). Macrozoobenthos samples were collected using a Surber sampler of an area of 0.1 m2, mesh size 500 mm. Only at the sites Trilj I and Trilj II and at the Peru~a Reservoir wasa a drag sample of 0.5 m taken using a 20 cm wide triangular dredge (»kratzer net«, also of an area of 0.1 m2, mesh size 500 mm). Macroinvertebrate samples cov- ered all habitat types, e.g. springs, upper, middle and lower reaches and HPP reser- voirs. At each site three or four different microhabitats were sampled (such as cobbles, fine sand, fine pebbles, algae covering the cobbles, moss or submersed vegetation), with the exception of sites at the Peru~a reservoir, Trilj I and Trilj II, where samples were taken from one habitat due to the homogeneity of the substrate. Altogether 366 macroinvertebrate samples were collected. Collected material was conserved in 80% ethanol and sorting and identification of the fauna were carried out in the laboratory. Macroinvertebrates were identified to the level of class or order, with the exception of Diptera and Arachnida, where identification was performed to the level of the family for the larval Chironomidae and Hydrachnidae (NILSSON, 1996; GHETTI, 1992; SCHMEDTJE &KOCHMAN, 1992), re- spectively. The number of individuals (population density) was calculated on a surface of 1m2, and all data were entered into the tables using Microsoft Excel 2003. Physico-chemical parameters were analysed using StatSoft Statistica 7.

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Fig. 2. Water temperature (C°) recorded monthly from August 2004 to August 2005 at 11 sampling sites at Cetina and Ruda rivers.

RESULTS

Physico-chemical parameters During the study, water temperature ranged from 4.6 °C to 26.3 °C (Fig. 2). The lowest mean value of 9.2 °C was measured at the highest site, the Cetina Spring in the upper reach, and the highest mean value of 14 °C was measured at the lowest site, Radmanove Mlinice, in the lower reach of the Cetina River. The concentration of dissolved oxygen was used to measure the level of organic production. At all sampling sites, concentration of dissolved oxygen did not vary significantly, thus there is no significant difference in oxygen concentration between the spring and the estuary (Fig. 3). Oxygen concentration ranged from 10.40 to 15.52 mg/l at sites in the upper reach. In no month did oxygen saturation fall be- low 90% (Fig. 4). Sites in the middle reach of the Cetina River did not show a signi- ficantly lower oxygen concentration than the sites in the upper reach. At sites in the middle reach, values ranged from 8.5 to 14.74 mg/l. The highest value, of 14.74 mg/l, was recorded at the site Obrovac Sinjski in April. Similarly, sites in the lower reach of the Cetina River did not show a significant difference of oxygen concentration compared to the middle reach, except for one month (August), when the oxygen concentration was 8.80 mg/l at ^ikotina La|a, while the mean values for ^ikotina La|a and Radmanove Mlinice were 11.39 mg/l and 11.27 mg/l, respectively.

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Fig. 3. Dissolved oxygen (mg/l) recorded monthly from August 2004 to August 2005 at 11 sampling sites in the Cetina and Ruda rivers.

Fig. 4. Percent of oxygen saturation (%) recorded monthly from August 2004 to August 2005 at 11 sampling sites in the Cetina and Ruda rivers.

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Fig. 5. pH value recorded monthly from August 2004 to August 2005 at 11 sampling sites in the Cetina and Ruda rivers.

Fig. 6. Electroconductivity (mS/cm) recorded monthly from August 2004 to August 2005 at 11 sampling sites in the Cetina and Ruda rivers.

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The pH value ranged from 7.45 to 8.55, which means that the waters of the Cetina River are mildly alkaline (Fig. 5). Electrical conductivity was used to measure the concentration of ionized sub- stances in the water. The values of electrical conductivity ranged from 282 to 588 mS/cm (Fig. 6). At sites located in the middle and the lower reach of the Cetina River (Obrovac Sinjski, Trilj I, Trilj II, ^ikotina La|a and Radmanove Mlinice), higher values of electrical conductivity were recorded, with significantly higher an- nual oscillations. The values of alkalinity (140 to 215 mg/l CaCO3) showed that the rivers Cetina and Ruda have moderately hard water (Fig. 7).

Fig. 7. Alkalinity (mg CaCO3/l) recorded monthly from August 2004 to August 2005 at 11 sampling sites in the Ruda and Cetina Rivers.

Macroinvertebrate community structure The Cetina River is characterized by a relatively high diversity of macrozoo- benthos. During 13 month surveys, in 366 samples a total of 310225 animals were collected and all values were calculated per square meter (m2). A total of 24 differ- ent macroinvertebrate taxa were recorded. Macroinvertebrate samples were col- lected from various microhabitats (cobbles, fine sand, fine pebbles, algae covering the cobbles, moss and submersed vegetation). At sampling sites in the spring and upper reach of the Cetina River 20–23 macro- invertebrate taxa were recorded (Tabs. 2–4, Figs. 8–10). The average density of

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58 Vu~kovi}, I. et al.: Benthic macroinvertebrate communities in the Mediterranean karst river the Cetina... 0.00 0.08 0.02 0.07 0.01 0.00 0.00 0.05 0.21 tion at sampling site Cetina Spring (Glava{) during 2004/2005 (Ad – adults, Lv – larvae). 2 030005000 018 03000000030 0 9 30000053053 062 000007505050388 03000005000 0 8 00000050000 0 5 00000000300 0 3 000738185000041 00070255030000268 Density of macroinvertebrates per m MonthAmphipoda 2004/08Araneae 3899 09 5831 10 41623 3 3613 11 533 12 2820 9628 01 6398 02 3298 2308 03 9400 7668 04 7828 05 104847 83.83 06 07 2005/08 Total Propor- BivalviaChironomidaeColeoptera Ad 566 27 43 17 7 583 197 0 0 7 0 0 3 158 263 0 0 43 23 3 103 200 328 0 110 108 335 1685 1396 1.35 1.11 Coleoptera LvCollembola 20 0 0 0 7 10 20 0 0 5 508 25 0 10 8 5 608 0.49 CopepodaDipteraEphemeroptera 0 0 7 37 137 43 17 0 43 33 10 8 8 223 10 23 33 63 3 8 95 125 60 8 90 230 801 0 0.64 513 0.41 GastropodaHeteroptera 1022 255 0 316 70 3 535 1203 193 208 18 1228 933 985 6969 5.57 Hirudinea 0 Isopoda 0 Megaloptera 0 NematodaOligochaetaOstracoda 0Plecoptera 0 10 0 43 3 33 0 243 147 0 30 53 3 0 45 3 0 1163 93 15 0 1063 433 0 103 0 93 1488 518 68 0 525 0 58 5484 118 4.37 0 3 3 103 202 771 0.16 0.61 TrichopteraTurbellariaTotal 20 0 53 67 30 5620 6450 37 17 43175 110 4023 3 662 0 85 3530 13672 23 115 7374 118 73 4959 2769 25 13 13069 33 9407 75 10356 53 125066 18 100.00 23 58 8 116 676 115 0.54 612 0.48 Tab. 2.

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Nat. Croat. Vol. 18(1), 2009 59 0.01 0.33 0.01 0.20 0.08 tion 0000000 0223 0000000 3 3 730301007137 33070001756 0303000 0 6 at sampling site Preo~ki Most during 2004/2005 (Ad – adults, Lv – larvae). 2 Density of macroinvertebrates per m CopepodaDipteraEphemeroptera 3Gastropoda 629Heteroptera 47 10 0Hirudinea 5561Hydrachnidia 200 0 246 210 0Isopoda 313 1941 0 17 50 0Megaloptera 1981 0 999Nematoda 13 3170 0 180 0Oligochaeta 0 3 0 306Ostracoda 549 186 10 3 0 676 0 0Plecoptera 2037 0 0 0 3Trichoptera 3 40 0 120 0 0 223 3 0Turbellaria 0 4492 0 746 30 13 77Total 30 370 50 0 3 153 0 0 127 0 3 7 0 4662 0 30 939 0 60 0 2121 0 113 107 7 293 3 37 40 14156 0 4039 7 233 4053 50 20 0 1475 6160 0 63 7 7 47 1011 5801 13 0 20 9.11 0 27 23 3472 2817 13 1.49 0 0 30 27 0 13182 30 10 20 60 8234 30 0 43 0 10 273 16058 57 0 545 53 4788 90 27 20 0 3 0.81 460 14683 3 67 2854 0 160 0 0.68 10 22728 3 196 0 8814 17 90 0 67 20395 33 3 10 35 67681 0 178 57 114 100.00 60 0 63 0.26 616 60 233 0 230 7017 7 0.34 130 3749 10.36 73 1186 83 5.54 0 1.75 0.12 100 332 0.49 MonthAmphipodaBivalvia 2004/08 3673Chironomidae 09Coleoptera 1046 Ad 3183 10 1911Coleoptera 147 Lv 17 0Collembola 859 11 426 0 909 3330 3 12 176 0 0 7060 0 57 230 12141 01 0 4336 0 176 926 7 7859 02 536 2468 216 0 0 03 14663 0 193 5891 0 0 107 04 9347 639 17 0 15238 0 05 186 0 20 22.52 293 703 06 0 0 113 0 7 10 1002 7 976 2005/08 310 Total 0 Propor- 10 0 713 70 13 23151 816 34.22 0 7210 33 10.65 33 43 476 227 0.70 0.33 Tab. 3.

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60 Vu~kovi}, I. et al.: Benthic macroinvertebrate communities in the Mediterranean karst river the Cetina... 0.01 0.02 0.00 0.00 0.14 0.00 0.00 0.02 0.02 0.05 tion 03000 082 at sampling site Crveni most during 2004/2005 (Ad – adults, Lv – larvae). 2 300000000 016 30300303000 025 000300023030042 0000180000000018 000000000030 0 3 003000000000 0 3 000023131323476071717220 000000003000 0 3 000030000000 0 3 Density of macroinvertebrates per m Month:AmphipodaAraneae 2004/8Bivalvia 5182 9Chironomidae 4662Coleoptera Ad 6284 7076 3 10Coleoptera Lv 3047 7 10Collembola 0 11 390 1988 0Copepoda 1708 3 0 2890Diptera 77 12 10 Ephemeroptera 11389 0 656 10 27Gastropoda 5228 107 73 01Heteroptera 4496 110 0 73 3 13 0Hirudinea 290 4965 02 2774 10Hydrachnidia 3243 2434 550 170 9464 872Hydrozoa 03 8 0 3889 11166 443 403 13 0Isopoda 147 13 946 3956 04 743Lepidoptera 10 50 1225 0 0 216 107 73318 10Megaloptera 3170 1072 05 123 45.68 Nematoda 7 53 516 25 53 776 1469 13Odonata 50 06 0 240 6856Oligochaeta 110 0 3 87 0 87 13 Ostracoda 2324 0 07 173 27 1046 7Plecoptera 839 177 3503 7 13 2005/08 3 193Trichoptera 7 Total 2171 599 0 203 3 36Turbellaria 0 Propor- 10 117 0 3523 2571 0Total 0 256 177 20 939 0 220 440 7 160 170 13 13 0 110 11056 27 0 0 3 1648 2299 1975 0 110 17 6.88 0 147 13 36442 11945 18546 0 0 1.44 270 30 320 3 22.70 13 230 7852 0 7.44 0 3 10 433 10 17651 13 703 13 23 5 5422 0 266 20 0.46 57 87 20 0 7103 173 13 280 23 4068 3 5426 1835 0.06 60 37 0 20 21103 0 2.53 147 1.14 23 7840 3 0 186 73 10332 0 0 6649 20 67 96 80 30352 316 20 12634 50 20 503 613 13 9605 37 147 63 160515 30 12763 0.39 100.00 47 37 296 67 0 213 1305 137 200 7 0.81 0.14 13982 1971 8.71 3 1.20 40 263 0.16 Tab. 4.

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Fig. 8. Proportion of macroinvertebrate taxa per m2 at the sampling site Cetina Spring (Glavaš) collected with a Surber net monthly from August 2004 to August 2005 (Ad – adults, Lv – larvae).

Fig. 9. Proportion of macroinvertebrate taxa per m2 at sampling site Preo~ki Most collected with a Surber net monthly from August 2004 to August 2005 (Ad – adults, Lv – larvae).

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Fig. 10. Proportion of macroinvertebrate taxa per m2 at the sampling site Crveni Most collected with a Surber net monthly from August 2004 to August 2005 (Ad – adults, Lv – larvae).

Fig. 11. Proportion of macroinvertebrate taxa per dm2 at the sampling site Peru~a Reservior collected with a triangular dredge monthly from August 2004 to August 2005 (Ad – adults, Lv – larvae).

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Fig. 12. Proportion of macroinvertebrate taxa per m2 at the sampling site Obrovac Sinj- ski collected with a Surber net monthly from August 2004 to August 2005 (Ad – adults, Lv – larvae).

macroinvertebrates during 13 months was 9620 individuals/m2 at Cetina Spring- Glava{, 15741 individuals/m2 at the Preo~ki most and 12347 individuals/m2 at the Crveni Most. Amphipoda and Gastropoda were dominant groups in samples from all sites in the upper reach (Cetina Spring-Glava{; 83.83% and 5.57%, Preo~ki Most; 22.52% and 9.11%, Crveni Most; 45.68% and 22.70%, respectively). In addition to the contribution of Coleoptera larvae (34.22%), a considerable por- tion of the catch at the site Preo~ki Most consisted of Chironomidae (10.65%), Oli- gichaeta (10.36%) and Plecoptera (5.54%). Moreover, Plecoptera (8.71%), Ephemerop- tera (7.44%) and Chironomidae (6.88%) also accounted for a considerable portion of the catch at the site Crveni Most. At the Peru~a Reservoir 13 macroinvertebrate taxa were recorded (Tab. 5, Fig. 11). More than 66.00% of individuals collected during the entire research period belonged to Chironomidae. A considerable portion of the catch consisted of the crustaceans Ostracoda (17.65%) and Copepoda (5.88%) as well as Oligochaeta (4.04%). The aver- age density of macroinvertebrates during 13 months was 565 individuals/m2. A total of 21 macroinvertebrate taxa were recorded at the site in the middle reach of the Cetina River, Obrovac Sinjski (Tab. 6, Fig. 12). As in the upper reach, the dominant group was Amphipoda (27.01%) but Chironomidae (16.71%), Oligochaeta (12.90%), Gastropoda (8.27%) and Ephemeroptera (7.45%) also accounted for a con- siderable portion of the catch. The average density of macroinvertebrates through- out the 13 months was 5128 individuals/m2.

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64 Vu~kovi}, I. et al.: Benthic macroinvertebrate communities in the Mediterranean karst river the Cetina... tion 0.12% 0.12% 0.98% 0.37% 0.12% 0000030 0000010 at sampling site Peru~a Reservoir during 2004/2005 (Ad – adults, Lv – larvae). 2 000001000010 000010000010 0000700001080 Density of macroinvertebrates per m MonthChironomidaeCladoceraColeoptera Ad 50 10 0 11 0 01 0 0 02 3260 0 03 0 20 04 10 0 06 900 0 07 0 10 1200 08 0 5420 Total 66.42% Propor- 0 30 0.37% Coleoptera Lv CopepodaDipteraEphemeropteraGastropoda 0 0 0 0 0 10 0 0 10 310 100 0 0 0 40 0 0 0 170 20 0 0 100 200 0 0 0 480 220 260 5.88% 0.49% 0.98% HydrachnidiaNematodaOligochaeta 0OstracodaTrichoptera 0 0 0Total 0 0 0 0 30 0 0 160 0 0 50 0 30 0 260 40 0 140 0 10 0 10 0 4290 30 30 120 10 0 0 60 20 10 0 1150 0 200 10 300 2.45% 10 1240 330 180 7250 4.04% 100.00% 17.65% Tab. 5.

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Nat. Croat. Vol. 18(1), 2009 65 0.02 0.00 0.01 0.16 tion at sampling site Obrovac Sinjski during 2004/2005 (Ad – adults, Lv – larvae). 2 7003017320017110 03030000000 3 9 00000000030 0 3 00300300000 0 6 Density of macroinvertebrates per m MonthAmphipodaBivalvia 2004/08Chironomidae 90 09Cladocera 3 693 10Coleoptera Ad 0Coleoptera Lv 376 11 0 0 0Collembola 3 110 559Copepoda 12 759 33Diptera 0 113 107 20 0 Ephemeroptera 01 0 353 10 120 167 0Gastropoda 13 0 02 649 137Heteroptera 6 0 3 293 0Hirudinea 763 366 0 16 03Hydrachnidia 0 0 233 236 0 1026 293 666Hydrozoa 60 04 0 20 709 3 63 53Isopoda 566 193 0 7 153 05Megaloptera 4701 13 2125 88 0 0 7 0 0Nematoda 1695 147 87 9 06 96Oligochaeta 0 236 363 0 9038 6676 466 10 37 1 233Ostracoda 0 18006 07 40 0 606 0 27 0 40 27Plecoptera 20 27.01 13 2005/08 0 0 0 27 483 363Trichoptera Total 23 280 536 1 0 Propor- 0 107 0Turbellaria 137 1465 147 306 0 5 0 0 350Total 0 0 436 190 0 546 70 33 659 3 0 67 213 6 0 11 0 57 473 0 340 236 7 113 10 0 0 23 103 186 0 1703 163 11144 37 127 0 25 0 1264 10 87 236 13 80 16.71 110 24 0 2.55 0 183 666 1905 93 0 606 10 127 579 806 0 3 243 93 4658 40 4972 303 4 0 4346 637 0 24 13 30 10 3491 0.36 589 7.45 3 70 40 12 226 0.96 393 451 0 97 40 5514 80 266 0 919 127 33 3 3 973 8.27 0 1800 223 353 0 0 37 473 80 11031 20 1105 2.70 60 296 153 2033 0 1402 47 783 1.65 0 3 14758 386 23 17 0 250 7 1691 776 493 107 63 0 733 9667 50 0 809 37 3057 180 346 3041 1.09 77 8594 4.59 0 7 11704 360 0 0 0.52 12.90 6665 70 727 20 0 556 100.00 110 456 1.11 350 726 0 0 2149 1290 1.08 3.23 823 17 1.94 3600 190 5.40 0.29 Tab. 6.

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66 Vu~kovi}, I. et al.: Benthic macroinvertebrate communities in the Mediterranean karst river the Cetina... 0.07% 0.15% 0.01% 0.01% 0.01% 1520 2022 3.29% at sampling site Trilj I during 2004/2005 (Ad – adults, Lv – larvae). 0000000010 2 000010000040 0000120033020 000060000300090 00001000000010 00000000001010 Density of macroinvertebrates per m MonthAmphipodaAraneae 0 09 0 10 20 12 60 30 01 0 02 60 03 0 04 90 05 10 06 150 07 1700 2005/08 0 Total Percente 2090 3.00% Bivalvia 0 32 ChironomidaeCladocera 0 1470 890 0 17040 0 5690 0 1460 0 4500 31050 44.41% Coleoptera LvCollembola Copepoda 0DipteraEphemeroptera 20 0Gastropoda 0 130Heteroptera 30 0Hirudinea 50 0 0Hydrachnidia 0 10Isopoda 60 300 20 30 0Nematoda 10 0Odonata 30 0 100 0Oligochaeta 0 80 0 0 10 10Ostracoda 20 90 10Trichoptera 50 30 0 0 0 190 70 0Turbellaria 0 10 0 0 30Total 0 2390 0 0 0 90 10 90 30 0 180 0 20 130 430 0 3100 10 10 0 0 150 0 1480 10 20 100 0 0 360 0 50 50 0 80 10 430 0 1100 460 70 4462 230 0 2110 0 10 540 30 0 0 0 60 410 3000 50 760 0 130 200 0.77% 20 2320 290 170 160 0 20 0 90 0 50 80 40 19570 30 0 0 0 560 6590 360 280 0 170 720 2370 60 0 9.42% 0.79% 0 190 120 13060 0.40% 0 1.03% 20 0 0 10 520 1030 120 0 300 9020 1.47% 0 7900 800 0 0 17460 910 0 3200 1.13% 170 25.37% 1350 460 16600 20 280 390 68822 1.93% 1.43% 2960 100.00% 0 0 4.24% 0 590 0.84% 160 0.23% Tab. 7.

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Nat. Croat. Vol. 18(1), 2009 67 tion 0.35% 0.02% 0.02% 0.67% 0.04% 0.02% at sampling site Trilj II during 2004/2005 (Ad – adults, Lv – larvae). 0000000010 0000000010 0000000010 2 0000100300130010180 00001010100600230320 000000001001020 Density of macroinvertebrates per m MonthAmphipodaBivalvia 2004/09Chironomidae 90 10Cladocera 0Coleoptera Ad 0 0 12Coleoptera Lv 800 0Collembola 110 300 01Copepoda 0 380Diptera 0 80 0 0 02Ephemeroptera 60 0 0Gastropoda 380 10 0 03 0Heteroptera 0 20 1440 0Hirudinea 100 20 0 10 04 310Hydrachnidia 10 10 0 0 200 260Hydrozoa 10 20 30 05 30Isopoda 0 2290 30 210 270 20Nematoda 0 190 40 10 06Oligochaeta 270 0 770 0 0 70Ostracoda 140 0 0 160 80 07 0 0Plecoptera 3190 0 3210 380 0 0Trichoptera 2005/08 0 0 0 60 60 0Turbellaria 0 170 80 Total 150 0 280 110 0 120Total Propor- 160 0 100 220 240 1050 2280 100 390 40 0 0 200 220 0 0 4.42% 0 9150 0 450 30 220 0 80 0 100 10 160 10 17.72% 0 30 400 90 1060 10 570 0 2020 1050 0 110 0 480 10 0 20 2560 2.01% 0 0 190 0 0 130 4040 0 1 140 0 1120 70 17060 0 2.01% 10 10 40 20 0 1910 360 110 0 10 150 80 1290 1520 400 10 1300 0 5590 900 0 1151 620 40 2.95% 30 0 1350 670 2.25% 0 1.74% 0 10 1760 160 2.97% 0 20 26670 20 330 810 100 1050 2430 0 450 20 23220 1.55% 2.03% 0 10200 0 44.97% 180 0 10 51 20 2190 340 870 4680 4.25% 0 1430 0 54421 2550 2.78% 100.00% 190 4.94% 270 420 760 0.82% 1.48% Tab. 8.

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68 Vu~kovi}, I. et al.: Benthic macroinvertebrate communities in the Mediterranean karst river the Cetina...

At sampling sites Trilj I and Trilj II 20 macroinvertebrate taxa were recorded (Tabs. 7–8, Figs. 13–14). The benthic community of these sites was dominated by Chironomidae and Oligochaeta, which accounted for more than 40% of the total catch. The average macroinvertebrate density was similar at these two sites throug- hout the whole period of the study (5294 individuals/m2 and 4186 individuals/m2 at sites Trilj I and Trilj II, respectively). A total of 22 and 24 macroinvertebrate taxa were recorded at sites in the lower reach of the Cetina River, ^ikotina La|a (Tab. 9, Fig. 15) and Radmanove Mlinice (Tab.10, Fig. 16), respectively. At the site ^ikotina La|a, the average density of macroinvertebrates collected was 6875 individuals/m2, whereas at the site Radma- nove Mlinice the average density was 4064 individuals/m2. At the former site, 21.58% of the catch consisted of Chironomidae, but Epheme- roptera (18.95%), Amphipoda (13.30%), Oligochaeta (11.17%), coleopteran larvae (7.15%), Gastropoda (6.78%) and Trichoptera (4.25%) also accounted for a consider- able portion of the catch. At the site Radmanove Mlinice 40.95% of the catch con- sisted of Gastropoda, followed by coleopteran larvae (17.84%), Ephemeroptera (7.49%), Amphipoda (7.42%) and Trichoptera (5.93%). At Ruda Spring, a total of 20 macroinvertebrate taxa were collected (Tab. 11, Fig. 17). The dominant taxa were Amphipoda (25.60%), Chironomidae (20.44%), Gastro- poda (17.53%), coleopteran larvae (15.16%), Ephemeroptera (11.03%) and Plecoptera (5.48%). Downstream, at the site Ruda II, in total, 23 macroinvertebrate taxa were recorded (Tab. 12, Fig. 18). As with the spring site, the community was dominated

Fig. 13. Proportion of macroinvertebrate taxa per dm2 at the sampling site Trilj I collected with a triangular dredge monthly from August 2004 to August 2005.

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Nat. Croat. Vol. 18(1), 2009 69

Fig. 14. Proportion of macroinvertebrate taxa per dm2 at the sampling site Trilj II col- lected with a triangular dredge monthly from August 2004 to August 2005 (Ad – adults, Lv – larvae).

Fig. 15. Proportion of macroinvertebrate taxa per m2 at the sampling site ^ikotina La|a collected with a Surber net monthly from August 2004 to August 2005 (Ad – adults, Lv – larvae).

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70 Vu~kovi}, I. et al.: Benthic macroinvertebrate communities in the Mediterranean karst river the Cetina... tion 0.00% 1.18% 0.29% 0.00% 0.74% 0.08% 0.12% 0.13% 7700263 0000100015115 at sampling site ^ikotina La|a during 2004/2005 (Ad – adults, Lv – larvae). 2 0000000002105 03730131004313665 030004701000110 30003030000012 0300000000003 000030000637578 Density of macroinvertebrates per m MonthAmphipodaAraneae 2004/08 1535Bivalvia 09Chironomidae 569Cladocera 10 4918 3 1472Coleoptera Ad 173 11 110Coleoptera 0 Lv 43 90Collembola 1359 0 12 4662 846Copepoda 533 0 140 0Diptera 0 01 10 0 809Ephemeroptera 0 649 10 13 147 02Gastropoda 2987 450 476Hirudinea 1452 376 50 0 599 0 0 03 0Hydrachnidia 1152 986 3826Isopoda 390 4229 0 719 04 123 3 713 27 67 450Megaloptera 140 686 0 270 0 05Nematoda 97 1725 160 1528 410 7 23 10Odonata 3124 200 0 50 437 260 06 13 20 3 70Oligochaeta 353 27 566 11913 1961 3 17Ostracoda 87 7 1146 13.30% 07 0 47 103 749 0 0Plecoptera 43 30 1768 0 2005/08 490 286 0 TotalTrichoptera 67 2361 20 862 7 43 Propor- 243 20 420 27 3Turbellaria 7 7 340 33 70 27 1702Total 382 133 193 73 10 1422 0 0 93 756 67 43 19276 120 756 90 10 147 659 180 21.58% 0 236 370 20 73 4282 10 693 0 610 749 14455 23 100 3 7 589 107 0 53 15 16930 203 10 2397 130 10 6395 18.95% 832 0 466 470 10 605 140 14700 17 0 107 7.15% 0 430 42 23 0.60% 392 0 10 3 2441 326 0 5266 7224 30 5982 40 107 10 40 2258 83 0 8.04% 6.78% 60 40 11192 6950 1635 3 3 3220 117 0 0 166 1.83% 7 16479 166 37 78 3395 140 0 30 15 573 5109 1911 3 0 8069 37 2.15% 0 303 50 2407 110 58 0.34% 0 683 89377 37 0 10037 100.00% 120 11.17% 30 0 3873 57 147 4.25% 0 0 33 623 393 50 0.69% 0.44% 926 1.04% Tab. 9.

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Nat. Croat. Vol. 18(1), 2009 71 0.37 0.23 0.31 0.03 0.16 0.22 0.01 0.19 0.06 0.01 0.01 0.06 tion 030003 029 03000130117197 0000000 016 03000303086 0000000 026 at sampling site Radmanove Mlinice during 2004/2005 (Ad – adults, Lv – larvae). 2 73100097 0703010000 0377170110 707317073137 700800 0117 3700000830107 03000001002317103156 00070000000 0 7 00033000000 0 6 00070000000 0 7 Density of macroinvertebrates per m PlecopteraTrichopteraTurbellaria 7 Total 120 0 430 353 6454 10 4189 3019 303 90 30 3184 193 5431 13 7788 2625 7 5921 2492 27 3684 413 2838 176 5126 52841 1006 100.00 3081 5.94 OligochaetaOstracoda 27 0 20 173 0 15 7 213 0 27 107 57 37 286 3 53 20 37 1018 1.20 Odonata 3 0 0 0 13 LepidopteraNematoda 0 0 0 27 0 23 HirudineaHydrachnidiaIsopoda 799 7 0 13 13 63 7 33 0 0 57 0 0 27 23 0 0 7 70 30 0 50 73 40 0 17 283 3 1368 201 2.70 0.40 DipteraEphemeropteraGastropoda 303Heteroptera 669 410 969 743 486 47 909 176 5 10 759 5 253 30 20 163 163 1452 4492 13 673 2717 147 20 1618 523 3120 260 370 789 130 1625 47 157 886 253 73 2158 326 616 21524 3959 40.95 137 7.49 3162 5.98 MonthAmphipodaAraneae 2004/08Bivalvia 483 09Chironomidae 400Coleoptera Ad 10 729 0 Coleoptera Lv 246 30 576Collembola 11 0 1672Copepoda 5 416 0 12Decapoda 789 120 0 123 43 01 13 509 0 0 186 0 0 20 02 0 586 183 0 17 190 03 107 13 80 0 470 0 579 0 04 0 133 7 3157 543 0 23 05 350 0 130 0 519 563 83 06 13 323 0 20 13 87 93 07 10 0 87 73 2005/08 256 463 Total 363 3870 0 803 Propor- 30 7.42 0 130 513 13 9379 130 0 17.84 7 1981 203 3.75 1764 680 3.36 1.31 Tab.10.

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72 Vu~kovi}, I. et al.: Benthic macroinvertebrate communities in the Mediterranean karst river the Cetina... tion 0.05% 0.00% 0.01% 0.05% 0.00% 0.06% 0.01% 2005/8 Total Propor- 000000093 1234567 03030300022 at sampling site Ruda Spring during 2004/2005 (Ad – adults, Lv – larvae). 2 003703237130002076 00300000000003 0300013003000322 7337203703770370 00007000000007 Density of macroinvertebrates per m Total 17363 2740 20996 2541 9875 6276 15384 4529 5680 2315 21698 7495 34657 151549 100.00% PlecopteraTrichopteraTurbellaria 743 23 0 290 766 90 0 27 67 30 420 50 2228 107 1132 170 73 27 120 97 67 989 17 1655 603 8294 480 5.48% 1977 1.30% NematodaOligochaetaOstracoda 220 353 0 3 13 17 0 3 0 27 0 0 83 40 0 3 7 10 0 7 17 97 0 0 47 33 387 593 0.26% 0.39% HydrachnidiaIsopoda 100 0 37 0 13 0 63 0 17 0 143 0 133 506 0.33% CopepodaDipteraEphemeroptera 10Gastropoda 1412Hirudinea 0 23 0 373 33 390 0 83 63 3 4266 0 2081 376 20 10 5361 649 47 1092 10 1079 2721 1059 10 17 1169 150 1062 77 10 80 719 10 0 3050 2085 40 1515 1498 10 6896 4056 20 16719 26566 0 17.53% 11.03% 353 17 43 1022 3 1701 87 1.12% 0.06% ChironomidaeColeoptera Ad 1652Coleoptera Lv 456 0Collembola 7609 57 4429 0 140 0 4759 13 300 50 27 0 1888 60 210 693 3447 490 0 27 40 1955 236 63 0 110 10270 3 2155 0 176 210 11675 2304 70 30974 22971 20.44% 15.16% 60 1689 1.11% MonthAmphipodaAraneae 2004/8 4336Bivalvia 9 2248 6074 10 3 260 43 11 0 1702 20 3726 12 0 4309 3 996 10 0 1831 1262 0 3197 2584 27 6267 38792 25.60% Tab. 11.

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Nat. Croat. Vol. 18(1), 2009 73

Fig. 16. Proportion of macroinvertebrate taxa per m2 at the sampling site Radmanove Mlinice collected with a Surber net monthly from August 2004 to August 2005 (Ad – adults, Lv – larvae).

Fig. 17. Proportion of macroinvertebrate taxa per m2 at the sampling site Ruda Spring collected with a Surber net monthly from August 2004 to August 2005 (Ad – adults, Lv – larvae).

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74 Vu~kovi}, I. et al.: Benthic macroinvertebrate communities in the Mediterranean karst river the Cetina...

Fig. 18. Proportion of macroinvertebrate taxa per m2 at the sampling site Ruda II collected with a Surber net monthly from August 2004 to August 2005 (Ad – adults, Lv – larvae).

by the following taxa groups; Amphipoda (43.78%), Ephemeroptera (18.62%), Chi- ronomidae (18.24%), coleopteran larvae (4.97%) and Plecoptera (4.16%). The aver- age macroinvertebrate density throughout the period of the study was 12629 indi- viduals/m2 at the site Ruda Spring and 9264 individuals/m2 at Ruda II. Macroinvertebrate density at all sampling sites during 2004/2005 is given in the appendix (Tab. 2–12).

DISCUSSION

Values of water temperature of the Cetina River recorded in the current study were in accordance with prior surveys of this river ([TAMBUK-GILJANOVI], 2005). Water temperature is directly dependent on the temperature of the air (GILLER & MALMQUIST, 1998). In Mediterranean karst running waters, for instance in the Krka, Zrmanja, and Cetina, water temperature decreases with depth, and increases downstream ([TAMBUK-GILJANOVI], 2002, 2005). Values of dissolved oxygen ranged from 8.50 to 15.52 mg/l along sites at the Cetina River, which is in accordance with the mean values recorded from the other Mediterranean karst rivers, e.g. Zrmanja, Krka, etc. (about 10-12 mg/l; [TAMBUK- GILJANOVI], 2002, 2005). The concentration of dissolved oxygen as a physico-chemi- cal parameter is used to measure the level of organic production in a watercourse (GILLER &MALMQUIST, 1998). Generally, the concentration of oxygen decreases from

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Nat. Croat. Vol. 18(1), 2009 75 tion 0.01% 0.04% 0.00% 0.02% 0.00% 0.02% 0.05% 0.01% 0.02% 2005/8 Total Propor- 1234567 30000070109 at sampling site Ruda II during 2004/2005 (Ad – adults, Lv – larvae). 2 00000000000010 00000000000010 33033000103133041 00000100100307030 00000000300003 00000000001713030 00003000130370356 3003000001000016 Density of macroinvertebrates per m PlecopteraTrichopteraTurbellaria 706Total 360 0 776 95 55 19255 196 9738 0 3890 173 110 2368 240 173 2875 203 3240 193 5184 160 286 4776 123 150 10134 2327 63 23 24272 1755 7971 40 486 24402 120432 120 100.00% 393 153 4983 2049 4.16% 1.68% Copepoda DipteraEphemeropteraGastropoda 2870Heteroptera 103 210Hirudinea 599 2680 0Hydrachnidia 203 7Isopoda 445 496 1165 3Nematoda 160 536 3Oligochaeta 0 0 3Ostracoda 569 10 0 10 816 196 0 3 446 10 150 20 7 889 180 390 30 13 7 10 4206 110 37 0 1329 3 0 513 7972 67 83 123 23182 33 13 137 18.62% 902 0 10 7 576 90 107 120 7 7 303 10 0 3546 77 20 569 2.95% 1495 7 7 0 1.33% 27 7 60 67 33 1358 1050 1.13% 7 0.87% 100 344 0.28% MonthAmphipodaAraneae 2004/8 7166Bivalvia 9 8608 340 10 1002 83 11 992 0 12 1845 2554 0 2954 2497 3 1558 13 4362 5435 12910 52223 43.78% ChironomidaeColeoptera Ad 4469Coleoptera Lv 293 0Collembola 2071 70 35 57 10 0 0 70 20 17 20 40 100 0 17 256 130 779 120 0 370 23 4922 666 603 0 97 93 10892 490 373 0 90 350 1272 892 200 21737 18.24% 5958 2202 4.97% 1.80% Tab. 12.

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76 Vu~kovi}, I. et al.: Benthic macroinvertebrate communities in the Mediterranean karst river the Cetina...

the surface towards the bottom and downstream (GILLER &MALMQUIST, 1998). In the surveyed area, there are no considerable differences in the concentration of dis- solved oxygen at sites in the upper, middle and lower reaches; hence there is no large decrease of oxygen concentration from the spring to the estuary. The latter may be the consequence of the morphology of the lower reaches, since this section contains numerous cascades and large boulders that enable additional aeration of water, thus increasing the quantity of dissolved oxygen (MAYER, 1993). The range of pH value recorded in this study is in accordance with the values typical of karst running waters in Central ; from 6.5 to 8.5 ([TAMBUK-GILJA- NOVI], 2005). These values are result of the limestone geological substrate of the karst running waters in the region. Waters on such substrates have a high buffering capacity (GILLER &MALMQUIST, 1998). When leaving the underground, the water, along with carbonates, also contains carbonic acid and free carbon (IV) oxide that lowers the pH value. The highest values are measured in the summer, when the water level is lower and river flow slower. In the middle and lower reaches, the anthropogenic influ- ence is increased (most households do not have wastewater sewerage) ([TAMBUK- GILJANOVI], 2005). The values of alkalinity measured in Cetina and Ruda are also within the range listed according to prior research ([TAMBUK-GILJANOVI], 2002, 2005). Water in the Mediterranean karst rivers in the wider area of Dalmatia (the Jadro, @rnovnica, Ce- tina, Ruda and Kosinac) is moderately hard, with 140 to 215 mg/l CaCO3 ([TAMBUK- GILJANOVI], 2002, 2005). Overall, the alkalinity of karst running waters in the upper reaches is directly influenced by the rainfall and groundwater levels (BONACCI, 1987; [TAMBUK-GILJANOVI], 2002, 2005). At sampling sites at the Cetina Spring and the Ruda Spring, the community is not dominated by insect taxa, which is in accordance with previous studies on sim- ilar rivers (DOLÉDEC, 1989; CIANFICCONI et al., 1991). In hard waters, where pH is higher than 7.0 and alkalinity is higher than 25 mg/l CaCO3, benthic communities are not dominated by insect taxa (WEBB et al., 1998). The density and diversity of macroinvertebrates is generally higher in permanent springs, such as the springs of the Cetina and Ruda. However in some springs that occasionally run dry, the den- sity of some taxa (Diptera and Ephemeroptera) may be higher, due to their capacity for fast colonization (GLAZIER &GOOCH, 1987). At the Peru~a reservoir, the dominant substrate is mud, and the sampling loca- tion was near the dam. Insect larvae that could be present in the substrate are lack- ing, and even if they were present (having drifted there), they are probably located in the substrate at the beginning of the reservoir. Drift densities are usually higher in the summer and spring (SCHREIBER, 1995) and lower in the winter (SHEARER et al., 2002). High oscillation in water flow and physico-chemical parameters in Peru~a Reservoir may have a negative impact on the macroinvertebrate community (CA- ZAUBON &GIUDICELLI, 1999). In the middle reach, at sites Trilj I and Trilj II, the dominant taxa were Oligochae- ta and Chironomidae. In general, the high population density of the above men-

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Nat. Croat. Vol. 18(1), 2009 77

tioned groups indicates high organic pollution (VIÐINSKIENË, 2005). Even though these two localities are similar to Peru~a Reservoir in terms of substrate type, diver- sity was higher than in Peru~a Reservoir, possibly due to the high oscillations in water level and physico-chemical parameters in the latter (CAZAUBON &GIUDICELLI, 1999). The previous study showed a similar macroinvertebrate community struc- ture in the middle reach of the Cetina River. The anthropogenic influence in the form of abiotic factors such as the untreated reception of wastewater and flow reg- ulation, have a negative impact on the ecosystem in this part of the Cetina River (CORTES et al., 2002). At Radmanove Mlinice, the sampling site in the lower reach, the benthic commu- nity was dominated by Gastropoda, coleopteran larvae and Ephemeroptera. Prior studies of the gastropods have shown that their population density is related to the biomass of macrophytes (CALOW, 1973; VINCENT et al., 1991; COSTIL &CLEMENT, 1996). Accordingly, in the present study the highest gastropod population density was observed at the site with the largest biomass of macrophytes and mosses. Benthic community structure at some of the investigated sites in Cetina River was noticeably influenced by the flow regulation. Changes in taxonomic and func- tional composition of benthic assemblages are expected (BOYERO, 2003). Different taxa usually respond in a particular way to flow regulation (WARD &STANFORD, 1979). According to the observed community structure the sites in the middle reach appear to be mostly influenced by flow regulation measures (CORTES et al., 2002; WARD &STANFORD, 1979). RADER &BELISH (1999) found that most mayflies, simu- liids, and some stoneflies and caddisflies were the least tolerant of low flow condi- tions, while chironomids and ostracods were the most tolerant. During the entire study, throughout the 13 months, variations in the density of macroinvertebrates were recorded. Overall, the density of macroinvertebrates de- pends on the life cycle, specific behaviour, and may also be reduced by the alter- ation of biological conditions in the habitat (BÊCHE et al., 2006). In order to obtain a detailed insight into the composition and structure of macroinvertebrate communi- ties and their differences in various reaches of the river, a comprehensive study of macroinvertebrate community needs to be conducted.

ACKNOWLEDGEMENT

We are very grateful to our colleagues from Department of Zoology, University of Zagreb for their assistance in the field. We also highly appreciated the support and help from the Majstrovi} family (Biteli}) and Dr Ignac Sivec and Dr Bogdan Horvat (Slovenian Museum of Natural History in Ljubljana, Slovenia). This paper is part of the outcome of the project »Biological indicators and ecology, distribution and den- sity of caddisflies (Trichoptera, Insecta) along the Cetina River«, supported by Hrvat- ske vode and projects (Nos. 119-1193080-1206, PL: M. Ku~ini} and 119-1193080-3076, PL: M. Kerovec) supported by the Croatian Ministry of Science, Education and Sports. Received October 24, 2008

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SA@ETAK

Sastav i struktura zajednica makrozoobentosa mediteranske kr{ke rijeke Cetine i njene pritoke Rude I. Vu~kovi}, I. Bo`ak, M. Ivkovi}, M. Jelen~i}, M. Kerovec, A. Popija~, A. Previ{i}, S. [irac, I. Zrinski & M. Ku~ini}

Istra`ivanje benti~kih beskralje`njaka rijeke Cetine i izvori{nog dijela rijeke Rude provedeno je u razdoblju od kolovoza 2004. do kolovoza 2005. godine na 11 postaja. Mjerne postaje nalazile su se du` cijelog toka rijeke Cetine i na izvori{nom dijelu njezine najve}e pritoke, rijeke Rude. Uzorci su prikupljani s triju razli~itih podloga

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82 Vu~kovi}, I. et al.: Benthic macroinvertebrate communities in the Mediterranean karst river the Cetina...

Surberovom mre`om te na postajama akumulacija Peru~a, TriljIiTrilj II kracer mre`om. U istra`ivanom razdoblju, u 366 uzoraka ukupno je prikupljeno 310225 je- dinki. Najbrojnije su bile skupine Amphipoda i Gastropoda, i to u gornjem i sred- njem dijelu toka, dok je u donjem dijelu toka najbrojnija skupina bila Gastropoda. Najve}a gusto}a makrozoobentosa bila je na gornjem dijelu toka, na postaji Preo~ki most u lipnju 2005. godine (22728 jedinki/m2), a najmanja na postaji na donjem dije- lu toka, Radmanove mlinice (90 jedinki/m2), u studenom 2004. godine. Na posta- jama Trilj I i Trilj II najzastupljenije su skupine Oligochaeta i Chironomidae koje su karakteristi~ne za organski optere}enije vodotoke. Sastav zajednica makrozoobentosa na postajama du` toka rijeke Cetine ne odra`ava situaciju kakvu bismo o~ekivali u prirodnim uvjetima, zbog regulacije samog toka i izgradnje hidroelektrana i aku- mulacija.

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