Aug 30, 2006 - ABSTRACT: Chironomids collected as pupal exuviae were used in biotypological study of the river Hron, one of the biggest rivers in the West ...
1 Acta Universitatis Carolinae Biologica 50 (2006): 5-17 Editum August 30, 2006
The actual longitudinal zonation of the river Hron (Slovakia) based on chironomid assemblages (Diptera: Chironomidae) PETER BITUSfK, MAREK SVITOK and MARTINA DRAGlJ:NOVA Department of Biology and General Ecology, Faculty of Ecology and Environmental Sciences, Technical University in Zvolen, Kolpa8ska 9, SK-969 01 Banska Stiavnica, Slovakia
Received: October 11, 2005 Accepted: November 2, 2005
ABSTRACT: Chironomids collected as pupal exuviae were used in biotypological study of the river Hron, one of the biggest rivers in the West Carpathians. A total of Ill chironomid taxa were recorded at 13 sites in March, May and July 2003. 1\vo-way indicator species analysis (TWINS PAN) was used to classify sampling sites into five groups defined by cbironomid species composition. Detrended canonical correspondence analysis (DCCA) showed slope, temperature and human influence to be the variables best correlated to the cbironomid data. Even the typology of the river was made in sense of the zonation concept, actual changes in cbironomid assemblages along the longitudinal gradient were rather gradual than zonal. Compared with data from 1980s when zonation pattern was largely influenced by pollution stress, the present data provided the better interpretable longitudinal scheme of the river. KEY woRDs: Chironomids, pupal exuviae, longitudinal zonation, river
INTRODUCTION Stream classification has been a popular topic among limnologists for a relatively long time. Despite difficulties, the classification of fluvial systems remains an important basis for the development of management strategies for streams and rivers (Naiman 1998). Most of classification systems have been based on biotic communities that can be sensitive indicators of environmental vitality (Wright et al. 1984). The Hron River is one of the main rivers of the West Carpathians. Up till now, it has not been affected by the construction of dams; however, it was heavily polluted during recent decades (since the end of the Second World War) by both increases in sewage waste water and the input of toxic wastes. The most serious toxic events occurred between 1947 and 1954. Over the following 30 years, toxic events were repeated at 2-5 year intervals. The 30 km long section between the village of Dubova and city of Banska Bystrica was especially heavily polluted. Water quality improved at the end of the 1980's. Successful fishery
5
r in the previously seriously damaged parts of the river in the 1990's has been good evidence of the river's ecological recovery. The principal goals of project No. 1/0200/03 performed in 2003-2005 were 1) to obtain information on the structure of the macro invertebrate communities and to identify the most important natural and anthropogenic factors influencing the river Hron environment; 2) to find the most preserved and most valuable river sections; 3) to evaluate the stability and persistence of macrozoobenthic communities comparing the recent and historical data. Chironomids are one of the most important benthic groups of invertebrates in every type of limnic ecosystems. Many species are considered to be good indicators of environmental conditions but problems with exact identification at species level of larval stages have restricted their usage for biomonitoring purposes. Chironornid pupal exuviae technique (Wilson & Ruse, 2005) provides a method that overcomes the problems mentioned above, and makes chironomids possible to be used in various studies of stagnant and running waters. The aim of this paper is to present the actual biocenotic zonation of the river Hron based on chironornid pupal exuviae data collected in 2003. This biotypological study can be used as a reference, one for further monitoring of the river and an assessment of environmental quality of other running waters in Slovakia. STUDY AREA AND SAMPLING SITES The Hron River, a 298 km long left tributary of the Danube, arises at ca 900 m a.s.l., and empties into the recipient at 112m a.s.l. Its catchment is 5454 km2, 40% of it is covered by forests. The slope ranges from -24%o in the upper reaches to -7%o and 1.5%o in the middle and lower course, respectively. The sampling sites were chosen with respect to changing of principal river characteristics and possible effects of human impact. Some characteristics at study sites on the river are shown in Fig. 1. MATERIAL AND METHODS Chironornid pupal exuviae were collected along the shore by skimming the water surface with a 250 J.tm mesh hand net in March, May and July 2003. In total, the study material included 39 samples and 14, 894 pupal exuviae. Each flotsam collection was placed into a small polythene bottle, labelled and fixed with 4% formalin in the field. In laboratory, pupal exuviae were manually sorted at 7-40 magnifications and preserved in 80% ethanol. Later, they were mounted on slides using the Berlese fluid and identified to species-level, if possible, under high magnification (x400). Identification keys included Wiederholm (1986), Langton (1991), Langton & Visser (2002). Au!ecological characteristics of the chironornid species/ taxa were used after Sporka (2003). Sampling sites were characterized using method of the River Habitat Survey (Raven et al. 1997, Bulankova 2006). Data from each sampling date were pooled for each site. Pooled presence/absence data set with exclusion of species presented in one specimen was used for further analyses. Two-way indicator species analysis (TWINSPAN; Hi111979) was used to classify sampling sites according to discrete chironomid assemblages. Final division level was set to 3 to maximise interpretability in terms of major environmental gradient. Dominant patterus of faunistic variation in the data were identified using detrended correspondence analysis (DCA) with detrending by segments. Canonical correspondence analysis (CCA) with Monte Carlo permutation test (999 permutations; p < 0.05) was
6
[Z]
geographical watershed
~
river Hron
~
tributaries
~
-ment
10
20
N
30km
A
Fig. 1: Map of the Hron River watershed showing the sampling sites. For abbreviations of the site names see Tab. 1.
used to assess relatiousbips between measured environmental variables and midge assemblages. As the distributions of altitude, slope, discharge and depth data were skewed, they were normalised by log transformation prior to analyses. Potentially important factors controlling midge assemblages were selected from each group of environmental variables by (1) sequential deleting collinear variables with high variance inflation factor (YIF) until all of the remaining variables had VIF < 10, and (2) forward selection associated with Monte Carlo permutation tests (999 permutations; p < 0.05). Probability levels in the forward selection were adjusted using sequential Bonferroni correction (Holm 1979). Intra-set correlations were examined to estimate the relative contributions of the individual environmental variables to the ordination axes (ter Braak 1995). Variation partitioning procedure (Borcard et al. 1992) was applied to distinguish independence and relative importance of selected environmental variables to chironomid assemblages. The variation partitioning was done by the means of series of partial CCAs. Analyses were performed using the programs CAP (Seaby & Henderson, 2004) and CANOCO (ter Braak & Smilauer 1998).
RESULTS AND DISCUSSION A total of Ill chironomid taxa were recorded. Six species, 0. ashei, 0. obumbratus, R. chalybeatus, 0. rubicundus, 0. weterensis, 0. rivicola were the most important making up more than 50% (8, 148) of all collected pupal exuviae. A systematic list is presented in Tab. 1. Classification based on TWINSPAN revealed five relatively distinct chironomid assemblages (Fig. 2). The initial division differentiated uppermost situated sites from the others. Absence of Cricotopus bicinctus was indicative for their assemblages. This group
7
00
Tanypodinae Procladius (Holotanypus) choreus (Meigen, 1804) Procladius (H.) sagittalis (Kieffer, 1909) Macropelopia nebulosa (Meigen, 1804) Arctopelopia barbitarsis (Zetterstedt, 1850) Conchapelopia melanops (Meigen, 1818) Conchape/opia pallidula (Meigen, 1818) Conchapelopia Pe1 Langton, 1991 Paramerina sp. Rheopelopia ornata (Meigen, 1838) Thienemanniemyia pseudocamea Murray, 1976 Buchonornyiinae Buchonomia thienemanni Fittkau, 1955 Diamesinae Diamesa cinerel/a Meigen, 1835 Diamesa hamaticomis Kieffer, 1924 Diamesa insignipes Kieffer, 1908 Diamesa starrnachi Kownacki et Kownacka, 1970 Diamesa tonsa (Walker, 1856) Potthastia Jongimana (Kieffer, 1922) Prodiarnesinae Odontomesa fulva (Kieffer, 1919) Prodiamesa olivacea (Meigen, 1818) Orthocladinae Bri/lia longifurca Kieffer, 1921 Bri/lia modesta (Meigen, 1830) Cardiocladius capucinus (Zetterstedt, 1850) Cardiocladius fuscus Kieffer, 1924
taxa
RF RB RB RB RB RB RF RF RF RF RF RB RB
Sc Sc Sc Sc Sc CoG Co Fa CoG CoG CoG p p
RF RF
?
RF RB
?
?
LF LF RF
flow
p p p p p p p p p p
FFG
-
-
-
-
+
-
-
-
-
-
-
-
-
-
-
-
-
-
+
+
+
-
+
+
+
-
-
-
-
-
+ +
+ +
+
-
-
-
-
-
+ +
+
-
-
-
-
+
-
+ +
-
-
-
-
-
+
-
+ -
-
-
-
-
Vas
-
-
-
Ben
-
-
-
-
Val
-
-
-
-
-
-
-
Mea
-
-
Tel
-
+
+
+ +
-
+
+
-
+ +
+
+
+ +
+
+
+
-
+
-
-
-
+
-
-
Rev
+
+
+
-
-
-
-
-
-
-
-
Bud
-
-
-
+
-
-
Sal
sampling sites
+
+
-
+
-
-
-
-
-
-
-
-
Rud
+
+
+
-
-
-
+
+ +
+
+ +
Kal
+
-
+
+ +
-
Jur
+
+
-
+
Bin
+
+
Kam
Tab. 1: Chironomid taxa at 13 sampling sites of the river Hron (abbreviations: FFG - functional feeding group, Sh - shredders, P - predators, Sc - scrapers, CoG - gathering collectors, CoFa - active filter feeders, CoFp - passive filter feeders; flow - tolerance to flow, RB - rheobiont, RF- rheophil, R·L- rheo·limnophil, LB -limnobiont, LF -limnophil, L-R- limno-rheophil).
10
Chaetocfadius Pe 2a Langton, 1991 Cricotopus (C.) bicinctus ( Meigen, 1818) Cricotopus (C.) curtus Hirvenoja, 1973 Cricotopus (C.) fuscus (Kieffer, 1909) Cricotopus (C.) simi/is Goetghebuer, 1921 Cricotopus (C.) tremufus ( Unnaeus, 1758) Cricotopus (C.) triannulatus Macquart, 1826 Cricotopus (C.) trifascia Edwards, 1929 Cricotopus (C.) vierriensis Goetghebuer, 1935 Cricotopus (C.) sp.A Cricotopus (lsocladius) intersectus (Staeger, 1839) Cricotopus U.) sylvestris (Fabricius, 1794) Diplocladius cu/triger Kieffer, 1908 Eukiefferiefla brevicalcar (Kieffer, 1911 ) Eukiefferiefla c/aripennis (Lundbeck, 1898) Eukiefferief/a clypeata (Kieffer, 1923) Eukiefferiefla devonica (Edwards, 1929) Eukiefferie/Ja fuldensis Lehmann, 1972 Eukiefferief/a gracei (Edwards, 1929) Eukiefferief/a ilkleyensis (Edwards, 1929) Eukiefferiella lobifera Goetghebuer, 1934 Eukiefferiella minor (Edwards, 1929} Eukiefferiefla simi/is Goetghebuer, 1939 Eukiefferiella tirolensis Goetghebuer, 1938 Heleniella senatosioi Ringe, 1976 Nanocladius bicolor (Zetterstedt, 1838) Nanocladius parvulus (Kieffer, 1909) Nanoc/adius rectinervis (Kieffer, 1911) Orthocladius (Euorthoc/adius) ashei Soponis 1991 Orthocladius (E.) rivicola Kieffer, 1924 Orthocladius (E.) rivulorum Kieffer, 1909 Orthocladius (E.} thienemanii Kieffer, 1906
taxa
CoG CoG CoG CoG Sc Sc Sc Sc
Sc
Sc Sc Sc Sc Sc Sc Sc
Sc
Sc CoG Sc Sc
Sc
? L-R L-R RF RF RF RF RB RB RB RF RF RF RB RB RB R-L RB RF RB RB RB RB
?
Sc Sc
Sc
? RF RB RF RF RF RF RF
flow
CoG Sc Sc Sc Sc Sc Sc
FFG
-
-
-
-
-
+
-
-
-
-
-
-
+
-
-
-
-
-
-
+ +
-
-
-
-
-
-
+
-
+
+
-
-
-
-
+ + +
-
+ + + +
-
-
+ + + +
-
-
-
+ + + + + +
-
+ + + +
-
+ +
+
+ + +
-
+
+ + +
-
-
+
+
+
-
+ +
+
-
-
+
-
+ + + +
+ + + + +
Rev
+ + +
+ +
+
-
-
+
-
-
+ + + + + + +
-
+ + +
+
-
Bud
+
Sal
+ +
-
+ + + + + + +
Vas
-
-
+ +
-
+
-
+
+ +
-
-
+ + + +
-
-
-
-
-
-
-
+
-
-
-
+ +
-
+
-
Ben
-
-
-
+
-
+ +
-
-
-
-
-
-
-
-
-
+
-
-
-
-
-
-
-
-
-
-
-
-
-
-
Val
Mea
Tel
sampling sites
+
+ + + +
-
+ + + +
+
-
-
+
-
+ + + + +
Rud
+
+ + +
+
-
-
+
+
-
-
+
+
-
+ + + + +
Kal
-
+ + +
+
+
-
+
-
+
+
-
-
+ +
+
Jur
+
+
+
+
+
+
+
-
-
+
+
-
+ +
-
+
Bin
+
+ + +
+
+
+
+ +
+ +
+ +
+
Kam
-
0
Orthocladius (0.) frigidus (Zetterstedt, 1838) Orthocladius (0.) g/abripennis (Goetghebuer, 1924) Orthocladius (0.) sp. nee marchettii Rossaro et Prato, 1991 Orthocladius (0.) oblidens (Walker, 1856) Orthocladius (0.) obumbratus Johannsen, 1905 Orthocladius (0.) rubicundus (Meigen, 1818) Orthoc/adius (0.) ruffoi Rossaro et Prato, 1991 Orthocladius (0.) wetterensis Brundin, 1956 Paracricotopus niger (Kieffer, 1913) Parametriocnemus stylatus (Kieffer, 1924) Parametriocnemus Pe1 Langton, 1991 Paratrichoc/adius rufiventris (Meigen, 1830) Paratrichocladius skirwithensis (Edwards, 1929) Paratrissoc/adius excerptus (Walker, 1856) Parorthoc/adius nudipenis (Kieffer, 1908) Rheocricotopus effusus (Walker, 1856) Rheocricotopus cha/ybeatus (Edwards, 1929) Rheocricotopus fuscipes (Kieffer, 1909) Synorthocladius semivirens (Kieffer, 1909) Tvetenia bavarica (Goetghebuer, 1934) Tvetenia ca/vescens (Edwards, 1929) Tvetenia veralli (Edwards, 1929) Chironomlnae- Chlronomlnl Cryptochironomus a/bofasciatus (Staeger, 1839) Cryptochironomus obreptans (Walker, 1856) Cryptochironomus rostratus Kieffer, 1921 Dicrotendipes nervosus (Staeger, 1839) Glyptotendipes pal/ens (Meigen, 1804) G/yptotendipes paripes (Edwards, 1929) Harnischia fuscimana Kieffer, 1921 Microtendipes ch/oris (Meigen, 1818) Paratendipes Pe1 Langton, 1991
taxa
LB LB RF L·R LF LF LF L·R L·R
? p p CoG Co Fa CoG CoG CoG CoG
? Sc CoG CoG Sc Sc CoG Sc CoG CoG CoG CoG Sc Sc Sc
CoG
-
-
-
-
-
-
-
+ + +
-
-
-
+
-
-
-
+
-
+
-
-
Mea
-
-
-
+
-
-
+ +
-
+
-
-
-
RB RB RB RB RB RB RF RF RF RF RB RB RB RB RB RF RB RB RB
+
? ?
-
Tel
RB
flow
CoG Sc CoG
?
Sc CoG
FFG
-
-
-
-
+ + +
-
-
-
+
-
-
+
-
-
+ +
-
+
-
Val
-
-
-
-
-
-
-
+ + + + + + +
-
+ +
+ + + + + +
-
-
+ +
Ben
-
-
-
-
-
-
+ +
-
+
-
+
-
-
-
-
-
-
+
-
+ + + + + + +
+
-
+
+ + +
-
+ + +
-
+
Sal
+
-
+ +
-
+
-
+
+
-
Vas
-
-
-
-
-
-
+ +
-
+ + +
-
+
+ + +
-
+ +
+ +
Bud
+
+ +
+
-
+ + + + + + +
+
+ + +
-
+ +
-
Rev
sampling sites
-
+
+
-
-
-
-
+
+ +
+
-
+
+ +
+ +
+
+ + +
+
+
+ +
-
Kal
+
+ + +
+
+ + + + + +
+
-
Rud
+ + + +
+ +
+
+
+ + +
+
+
+ +
+
Jur
+
+
-
+ +
+
-
+
+
+
+ +
Bin
+
+ +
+ + +
+
+
+ +
Kam
...... ......
Paratendipes Pe2 Langton, 1991 Phaenopsectra Pe1 Langton, 1991 Polypedilum (Polypedi/um) albicorne Goetghebuer, 1930 Polypedilum (P.) convictum (Walker, 1856) Polypedilum (P.) cu/tellatum Goetghebuer, 1931 Polypedilum (P.) /aetum (Meigen, 1818) Polypedilum (P.) nubeculosum (Meigen, 1804) Polypedilum (P.) pedestre (Meigen, 1830) Polypedilum (Tripodura) pul/um (Zetterstedt, 1838) Polypedilum (T.) scalaenum (Schrank, 1803) Polypedilum Pe 8 Langton, 1991 Stenochironomus (Petalopholeus) gibbus (Fabricius, 1794) Stictochironomus sticticus (Fabricius, 1781) Chironominae- Tanytarsini C/adotanytarsus mancus (Walker, 1856) C/adotanytarsus vanderwu/pi (Edwards, 1929) Microspectra atrofasciata agg. Paratanytarsus dissimi/is Johansen, 1905 Rheotanytarsus pentapoda (Kieffer, 1909) Rheotanytarsus photophi/us (Goetghebuer, 1921) Rheotanytarsus rhenanus Klink, 1983 Tanytarsus curticornis Kieffer, 1911 Tanytarsus ejuncidus (Walker, 1856) Tanytarsus gregarius Kieffer, 1909 Tanytarsus heusdensis Goetghebuer, 1923 Tanytarsus pallidicornis (Walker, 1856)
taxa
CoG ? CoG CoG CoFp CoFp CoFp CoG CoG CoG CoG CoG
?
R-L LF RB L-R
?
R-L LB RB RB RB
?
L-R
LB LF
? ?
RB RF RF RF L-R RF LF
-
? ?
CoG CoG CoG CoG CoG CoG CoG CoG CoG CoG CoG Sh
-
-
-
-
-
-
-
-
-
-
-
+
-
-
-
-
-
-
-
+
-
-
-
-
-
-
-
-
-
+
-
-
-
-
-
-
+ +
-
+
-
+
-
-
-
+
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
+
+
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
+
+
-
-
+
-
-
-
-
-
-
+
-
-
-
-
Bud
Vas
-
-
-
-
-
Ben
Val
Mea
-
-
-
-
-
-
-
Tel
flow
FFG
-
+ +
-
-
+ + + +
+
-
-
-
-
+ +
-
-
+
+
+
-
-
Rev
sampling sites Sal
+
-
+
-
+
-
-
-
+
-
-
+ -
-
+ + +
-
-
+
-
-
Rud
-
+ + +
-
+
-
+ + + + +
+ +
+ + + + +
-
+ + + +
Kal
+
+ + + + + + + + +
+
+ +
+ + +
+
Jur
+
-
+
+
+
+
+
+
Bin
+
+
+
+
Kam
Cricotopus bicinctus
Rheocricotopus chalybeatus
Tel Mea Val
I Ben
Vas Sal Bud
Rev Rud
Kal
Jur Bin Kam
Fig. 2: 1WINSPAN classification of sampling sites based on absence/presence of Chironomidae. Indicator species are displayed.
was further subdivided into two subgroups. At this level, separation of the site Ben (for abbreviations of locality names see Tab. 1) from the remaining sites was indicated by presence of R. chalybeatus. Lower situated sites were clustered into three groups. At the first division, D. starmachi was indicator for sites Vas, Sal and Bud. The other localities were divided by E. ilkleyensis as indicator species. In indirect ordination, eigenvalue of the first axis (A1 =0.385) was more than three times greater than second eigenvalue (A 2 =0.11 0) that indicates dominant faunistic gradient in chironomid data. The patterns of site segregation revealed by DCA (not presented) were similar to those evident in 1WINSPAN, suggesting high importance of changes along river continuum. DCA gradient length(> 3.0 SD units) confirmed a good approximation to unimodal models. CCA with forward selection and considering each group of environmental variables separately, indicated that each environmental group could be adequately represented, in a statistical sense, by just one variable. Selected model involved three variables (slope, temperature and human influence) with VIFs less than 4.0. As an evident arch-effect appeared in initial CCA, detrended canonical correspondence analysis (DCCA) was used. Detrending by second order polynomials was applied to prevent the second axis from being obscured by dependence on the first axis and improve the interpretation of the underlying environmental gradients (ter Braak & Srnilauer 1998). The results of CCA are graphically plotted in Fig. 3. Intra-set correlations indicated that the fust ordination axis (A 1 = 0.363) was strongly correlated with slope (r = 0.96), temperature (r = -0.88) and somewhat weakly with human influence (r =-0.62). The second axis ()..2 =0.085) was most strongly correlated with human influence (r = 0.57). However, only the first axis was significant (F = 2.839, p = 0.001), so the second axis is not considered further. The model involving three environmental variables significantly accounted for 41% of variation in chironomid data. However, it was not possible to distinguish individual contribution of each variable
12
anthropic influence! j
Kal
Sal
Ben
0 0
slope
0 Vas 0
Rev
Val
8Mea
0
Tel
Bin ~ ..... I
+-------r-------------~---------------r--------------,-------4 DCCA1 2.5 -1.5
Fig. 3: Detrended canonical correspondence analysis (DCCA) ordination plot with sampling sites and environmental variables. Only environmental variables explaining significant amount of species variation are displayed. Diameter of circle is related to the number of species recorded at sampling site.
(non-significant results of pCCAs) probably due to strong relation between environmental variables (cf. Leps & Smilauer 2003). When the variable of the lowest importance (human influence) was excluded from the model, overall explanatory power slightly decreased to 35%, and we were able to exactly decompose the variation in chironomid data set. Slope appeared to be potentially the most important variable which uniquely accounted for 14.1% of variation in the species data set. Temperature alone explained 12.1% of variation in the data set. 8.9% in species variation was attributable to the interaction between temperature and slope. Patterns revealed by DCA and DCCA and eigenvalues of their axis were similar. Also, Pearson product-moment correlation showed similarity between first DCA and DCCA axis site scores (r = -0.99, p < 0.001) suggesting that the important sources of species variation were captured by the selected environmental variables (0kland 1996). All biotic classification of stream and rivers assume a predictable relationship between biota and gradients of environmental factors. Numerous studies have documented the existence and strength of such gradients (e.g. Schaeffer & Perry 1986). Each division of TWINSPAN and the results of DCCA, as well, fully reflect the real geographic position of sampling sites along the stream. The first axis of DCCA can be identified as crena! - rithral - potamal faunal gradient of classical limnology. Only slope and temperature were found to contribute to explaining variation in chironomid data significantly, but other factors correlated with them (e.g. current, substrate, oxygen, food, etc.) can be expected to change along the stream simultaneously. Human impact (including organic pollution stress) increased downstream at the same time.
13
In spite of fact that TWINSPAN distinguished five groups of chironomid assemblages, the Hron section demarcated by the sites Tel and Bud can be considered as rithral. The uppermost river section corresponds with epirithral - mountain brook (Bitusik, et al. 1996): altitude- 900 m a.s.l., stream order II, channel width-3m, slope 24.3%o. Epirithral is considered to be the extreme zone (Laville & Vin~on 1991) with relatively good characterized coenoses. However, the composition of chironomid assemblage at the site Tel was not as distinctive like as has been observed in other West Carpathian streams with higher altitudinal gradient (Bitusik, 2000). The chironomid assemblage on this site was species poorest (Fig. 2) and only Parametriocnemus Pel and P. nudipennis were recorded there. Other recorded species were common with the lowermost situated localities. The group of the sites Mea, Val, Ben, Vas, Sal, and Bud can be characterized by: D. cinerella, D. hamaticomis, D. starmachi, 0. fulva, E. devonica, E. minor, 0. frigidus, 0. rivulorum, P. niger; P. stylatus and T. bavarica. A different position of the Mea and Val among the other localities is caused by 1) lower number of species, 2) absence of species of genera Cricotopus and Cardiocladius, and 0. rivulorum, 0. thienemanni, R. chalybeatus, S. semivirens, 3) no representation of Chironominae, with exception of Micropsectra atrofasciata agg. Locality Ben has a transition position among the sites Mea and Val on the one hand, and Vas, Sal, Bud on the other hand, because of the common occurrence of species characteristic for both of locality subgroups. The upper part of the Hron rithral zone (Mea, Val) could be classified as metarithral (sub-mountain brook) (altitude 700--800 m a.s.l., stream order III-IV, channel width -5-13 m, slope -11-6.6%o). The rest of this river zone corresponds with the hyporithral (sub-mountain river), while 2 sub-zones could be distinguished. The sites Ben and Vas are representatives of the upper sub-zone (altitude 540-480 m a.s.l., stream order VI, channel width 21-25 m, slope 3.5-2.7%o). The localities Sal and Bud are representatives of the lower sub-zone (altitude 355-270 m a.s.l., stream order VII, channel width 48-50 m, slope 2.5-1.5%o). In fact, taxonomic composition of the assemblage at locality Vas resembles the sites situated below more than locality Ben. It is supposed that this similarity is most probably the result of pollution rather than similar natural conditions. Section of the river between sites Rev and Kam can be considered as epipotamal with two sub-zones: 1) upper sub-zone (foothill river) corresponds with localities Rev and Rud (altitude-200m a.s.l., stream order VII, channel width -60 m, slope 1.2--0.8%o), 2) lower sub-zone (lowland river) is demarcated by sites Kal and Kam (altitude 100--150 m a.s.l., stream order VII, channel width -70 m, slope 1.0--0.5%o). Some studies revealed faunal discontinuity between the foothill rithral to the plain potamal (Ward 1986, Laville & Vin~on 1991). Absence of Diamesinae, some Orthocladiinae (e.g. E. ilkleyensis), and presence of many species/ taxa from Tanypodinae (e.g. Procladius spp., A. barbitarsis, R. ornata) and Chironominae (e.g. C. rostratus, D. nervosus, C. vanderwulpi, T. ejuncidus) can be distinctive characteristics of the lower sub-zone of the epipotamal. Chironomid assemblages of the sites Rev and Rud consist of some species characteristic both for the rithral zone (D. cinerella, P. olivacea P. niger, P. stylatus), and the potamal zone
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(C. fuscus, H. fuscimana, M chloris Paratendipes Pel, P. nubeculosum, P. pedestre, P. pullum, P. dissimilis, R. photophilus, T. gregarius, T. heusdensis). A presence of nearly all feeding groups is identified in this river zone. Relative contribution of predators and filter feeders is higher (especially at Kal and Jur) in comparison with rithral zone. Percentage proportion of limnorheophilic, limnophilic and limnobiont taxa increases in epipotamal zone, whilst rheobiont and rheophilic taxa decrease along the longitudinal gradient of the river at the same time. In spite of fact that the zones of the zonation concept (Illies & Botosaneanu 1963) were distinguished, the actual changes in chironomid assemblages along the river Hron seem to be gradual (clinal) rather than zonal. In 1980s chironomids of the river Hron were studied using the same methods (Bitusfk 1997). The present data provided a better legible longitudinal scheme of the river in comparison with the historical ones. The past zonation pattern was largely dependent on pollution stress and the transitions between zones were not identified correctly. Despite of it, author stated that chironomid species composition of an unpolluted upper section of the river closely resembles the meta- and hyporithral assemblages identified in the river Turiec (Bitusik 1995). Even some common characteristics with the Pyrenean typological scheme (Laville & Vin~on 1991) have been found. Temperature and flow regime are considered the overall factors controlling the distribution patterns of Chironomidae along river systems. Moreover, these factors control substantially the availability of food and substrate composition. The importance of substrate and food is correlated very well to the proportion of Orthocladiinae (mostly scrapers of periphyton) and Chironomini (gathering collectors of detritus and filtering feeders). Consequently, the longitudinal chironomid succession reflects the idea of the river continuum concept (Vannote et al. 1980) that has been documented in other Slovak streams (Bitusik 1992). The longitudinal distribution of the chironomid functional feeding groups in the river Hron exhibits conformance with an expectation. Gathering collectors and scrapers predominate by all sampling sites. The share of scrapers declines more or less continually downstream from the site Val, while the proportion of gathering collectors increases. High proportion of gathering collectors observed at the site Mea can be explained by the channel morphology. The river meanders at this section and the changes in the flow support the deposition of organic material. The increase of predators in the lower reaches of the river is connected with the highest number of Tanypodinae species recorded. Chironomidae were never involved in describing the system of running water classification. However, the first attempt to correlate chironomids with river zonation (Thienemann 1954) has been confirmed by a number of studies. Generalized patterns of chironomid distribution along longitudinal gradients in the northern hemisphere temperate rivers have been widely accepted (Lindegaard 1995). As far as a good agreement of opinions on succession of high chironomid taxa (subfamilies, tribe) can be seen, so the doubts growth when species level is taken into account. In the past decades a number of typological studies were carried out on chironomids of Europaean streams and rivers (see Lindegaard 1995 for review). Some results doubt the indicative value of chironomids for recognition of water types (Verdonschot et al. 1993).
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Other studies suggested that results of stream typology based on chironomids can be applied only within restricted areas (Laville & Vin~on 1991). It could be true but the deficiency of data about the effects of environmental variables on chironomid species structure can lead to different conclusions concerning the species distribution in rivers of the same region. The call for more detailed study of environmental factors responsible for chironomid species distribution (Rossaro 1991) is fully justified.
ACKNOWLEDGEMENTS We are indebted to Dr. Eva Bulankova who provided results of River Habitat Survey analysis. We wish to thank Martin Bitusik for language improvements. This study was supported by the grants No. l/0200/03, No. l/1292104 and No. l/1282104 of the Scientific Grant Agency of the Ministry of Education of Slovak Republic and the Slovak Academy of Sciences.
REFERENCES Brrus!K P., 1992: Can chironomids (Diptera: Chironomidae) reflect the state of vegetation in stream envimn. In: Saly R. (ed.): Forest, wood, ecology: Section 1: Forest and landscape ecology. Technical University in Zvolen, pp. 281-287. BrruS!K P., 1995: A biological assessment of the Turiec river and its selected tributaries using chironomid pupal exuviae (Diptera, Chironomidae). Dipterologica bohemoslovaca, 7: 17-26. BrruS!K P., 1997: The use of chironomid pupal exuviae (Diptera: Chironomidae) for characterizing of the river Hron (Slovakia, West Carpathians). Acta Facultatis Ecologiae, 4: 61-76. BrruSIK P., 2000: Klasifikacia horskych potokov Nizkych Tatier na zaidade zoskupeni pakomarov (Diptera: Chironomidae). Acta Facultatis Ecologiae, 7: 187-197. BrruS!K P., BULANKovA E., CERNY J., FAIMoNovA E., HALGOS J., KoDADA J., KRNo L, SPORKA F. & VRANovsKY M., 1996: Tecuce vody, in: RuiiCkova H., Halada r..., JedliCkaL. & Kalivodova E. (eds.), Biotopy Slovenska. Prirucka k mapovaniu a katal6gbiotopov. UKE SAY, Nitra, pp. 117-125. BoRCARD D., LEGFNDRE P. & DRAPEAu P., 1992: Partialling out the spatial components of ecological variation. Ecology, 73: 1045-1055. BuLANKOYA E., 2006: Hodnotenie hydromorfol6gie Hrona pomocou met6dy River Habitat Survey. Acta Facultatis Ecologiae (Zvolen), 14: (in press). HiLL M.O., 1979: TWINSPAN- A FORTRAN program for arranging multivariate data in an ordered two-way table by classification of the individuals and attributes. Section of Ecology and Systematics, Cornell University, Ithaca, New York, USA. HoLM S., 1979: A simple sequentially rejective multiple test procedure. ScaruiiiUliJian Journal ofStatistics, 6: 65-70. ILLIEs J. & BOTOSANEANU L., 1963: Problemes et methods de Ia classification et de Ia zonation ecologique des eaux courantes, considerees surtout du point de vue faunistique. Mitt. Internal. Verein. Limnol., 12: 1-57. LANGTON P.H., 1991: A key to pupal exuviae of West Palaearctic Chironomidae. Privately published by P.H. Langton, 3 St. Felix Road, Ramsay Forty Foot, Cambridgeshire, England, PE 17 1YH, 386 pp. LANGTON P.H. & VISSER H., 2003: Chironomidae exuviae. A key to pupal exuviae of the West Palaearctic Region. Interactive Identification System for the Europaean Limnofauna (llSEL), World Biodiversity Database, CD-ROM Series. LAYlll.E H. & VIN«;ON G., 1991: A typological study of Pyrenean streams: Comparative analysis of the Chironomidae (Diptera) communities in the Ossau and Aure Valleys. Verh. lntemat. Verein. Limnol., 24: 1775-1784. LEPS J. & SMILAUER P., 2003: Multivariate analysis of ecological data using CANOCO. Cambridge University Press, Cambridge, UK, 269 pp.
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LINDEGAARD C., 1995: Classification of water-bodies and pollution, in: Armitage P.O., Cranston P.S. & Pinder L.C.V. (eds.), The Chironomidae. Biology and ecology of non-biting midges. Chapman & Hall, London, pp. 385-405. NAIMAN R.J., 1998: Biotic Stream Classification, in: Naiman R.J. & Bilby R.E. (eds.), River Ecology and Management. Lessons from the Pacific Coastal Region. Springer-Verlag, New York, Inc., p. 97-119. 0KLAND R.H., 1996: Are ordination and constrained ordination alternative or complementary strategies in general ecological studies? Journal of Vegetation Science, 7: 289-292. RAVEN P.J., Fox P.J.A., EvERARD M., HoLMES N.T.H. & DAWSON F.H., 1997: 'River Habitat Survey: a new system for classifying rivers according to their habitat quality', in: Boon P.J. & Howell D.L. (eds.), Freshwater quality: defining the indefinable? The Stationery Office, Edinburgh, pp. 215-234. RossARo B., 1991: Cbironomids of stony bottom streams: a detrended correspondence analysis. Arch. Hydrobiol., 122:79-93. Sc:l!AEFFER D.J. & PERRY J.A., 1986: Gradients in the distribution of riverine benthos. Freshwater Biology, 16: 745-757. SEABY R.M.H. & HENDERSON P.A., 2004: Community Analysis Package 3.0. Pisces Conservation Ltd, Lymington. SroRKA F. (ed.), 2003: Vodne be:zstavovce (makroevertebnita) Slovenska. Supis druhov a autekologicke charakteristiky. Slovensk9 hydrometeorologick9 ustav, Bratislava, 590 pp. TER BRAAK C.J.F., 1995: Ordination, in: Jongman R.H.G., ter Braak C.J.F., van Tongeren O.E.R. (eds.), Data analysis in community and landscape ecology. Cambridge University Press, Cambridge, UK, pp. 91-173. TER BRAAK C.J.F. & SMU..AUER P., 1998: CANOCO release 4. Reference manual and user's guide to Canoco for Windows: Software for canonical community ordination. Microcomputer Power, Ithaca, 353 pp. THIENEMANN A., 1954: Chironomus. Leben, Verbreitung und wirtschaftliche Bedeutung der Chironomiden. Binnengewiisser, 20: 1-834. VANNOTE R.L., MINSHALL G .W., CuMMINS K.W., SEDELL J .R. & CUSHING C. E. 1980: The river continuum concept. Can. J. Fish. Aquat. Sci., 37: 130--137. VERDONSCHOT P.F.M., REALM. & SCHor J.A., 1992: Chironomids and regional water types. Netherlands Journal of Aquatic Ecology, 26: 513-520. WARD J.V., 1986: Altitudinal zonation in a Rocky Mountain stream. Arch. Hydrobiol., Suppl., 74: 133-199. WIEDERHOLM T. (ed.) 1986: Cbironomidae of the Holarctic region. Keys and Diagnoses. Part II. Pupae. Ent. Scand. Suppl., 28: 1--482. WILSON R.S. & RusE L.P., 2005: A guide to the identification of genera of chironomid pupal exuviae and their use in monitoring !otic and lentic fresh waters. Freshwat. Bioi. Assoc., 164 pp. WRIGHT J.F., Moss D., ARMITAGE P.O. & FuRsE M.T., 1984: A preliminary classification of running water sites in Great Britain based on macro-invertebrate species and the prediction of community type using environmental data. Freshwater Biology, 14: 221-256.
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