Open Access
Issue
Knowl. Manag. Aquat. Ecosyst.
Number 417, 2016
Article Number 11
Number of page(s) 19
DOI https://doi.org/10.1051/kmae/2015044
Published online 22 February 2016

© M. Płóciennik et al., published by EDP Sciences, 2016

Licence Creative Commons
This is an Open Access article distributed under the terms of the Creative Commons Attribution License CC-BY-ND (http://creativecommons.org/licenses/by-nd/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. If you remix, transform, or build upon the material, you may not distribute the modified material.

1 Introduction

thumbnail Fig. 1

Map of the study area.

Springs are ecotones between groundwater and surface waters (Webb et al., 1998) as well as between aquatic and terrestrial biocenoses (Cantonati et al., 2006). They reveal stable abiotic conditions in contrast to the rhithral and potamal zone (Van der Kamp, 1995). Chironomidae larvae are members of spring zoobenthos in both types of sites, eucrenal (or spring source) and hypocrenal (or springbrook) ones. In comparison to other groups of insects, Chironomidae are poorly studied in springs due to the difficulty of their larvae determination. However, it is known that ecological patterns of Chironomidae assemblages in springs can be influenced by various environmental factors (Lencioni et al., 2011; Mori and Brancelj, 2006) with an emphasis on anthropogenic activities (Ferrington, 1998), for example, by capturing springs (Lencioni et al., 2012). Although Chironomidae larvae are important community members of spring zoobenthos in Balkan Peninsula (Mori and Brancelj, 2006) and other European regions (Wagner et al., 1998), ecological patterns of their assemblages in springs of Dinaric karst are insufficiently known. This study focused on Chironomidae larvae assemblage of springs of Dinaric karst along the Cvrcka River mainstream (the NW Republic of Srpska, Bosnia and Herzegovina), where some of the investigated springs remain natural while the water quality and habitats of the others are substantially changed by human impact. Chironomidae larvae of Cvrcka River springs were not previously investigated, apart from Vilenjska Vrela spring (Filipović et al., 2009). Nevertheless, they determined collected chironomid larvae only to the family level, providing information on their density at the bottom unit area. Those data were an integral part of the research of spring macrozoobenthos community. The same approach is applied while investigating the other springs of the catchment area of the Vrbanja River, which left tributary is the Cvrcka River, (e.g. Pavlović et al., 2011) as well as the springs of the wider area of the Republic of Srpska (Pavlović et al., 2009, 2012; Mršić et al., 2009; Savić et al., 2011).

This study is conducted in the framework of a broader project focused on benthic fauna in Cvrcka River springs. One part of the springs is located in the canyon of the Cvrcka River. It is known that canyons as well as springs are refuges of many relicts and endemic species. That is why in the last years there have appeared several papers focused on the invertebrate fauna of Cvrcka River springs with the description of new probably steno-endemic species Hirudinea (Grosser et al., 2014), Gastropoda (Glöer and Pešić, 2014) and Trichoptera (Vitecek et al., 2015). All this further actualizes the importance of the research.

The aim of this study is: (1) to analyze the diversity and the distributional patterns of Chironomidae taxa in the springs along the Cvrcka River mainstream (the NW Republic of Srpska, Bosnia and Herzegovina), (2) to recognize the main environmental factors that influence Chironomidae assemblages in springs of Dinaric karst, (3) to verify how environmental classification of the springs is followed by chironomid communities themselves.

2 Materials and methods

2.1 Study area

The mainstream of the Cvrcka River (the NW Republic of Srpska, Bosnia and Herzegovina) is 14 745 km long with its source (785 m a.s.l.) in Kostići village and the water mouth (315 m a.s.l.) in the Vrbanja River, downstream of Večići village (Figure 1). The climate of the Vrbanja River basin is temperate with high annual precipitation (the first maximum of precipitation is in spring and the second in autumn). Winter is the driest period of the year. The bedrock of the Cvrcka River basin consists mainly of limestone and the river flows predominantly through a karst canyon. There are numerous karstic springs in the river valley and its near vicinity (Rajčević and Crnogorac, 2011).

The study included springs along 12 km of the Cvrcka River mainstream valley. This valley section is covered mostly by deciduous forest. Rheocrenes, rheopsammocrenes and captured springs were investigated (Appendix 1).

2.2 Field Sampling

Chironomidae larvae were collected from 27 springs of the Cvrcka River basin. Main spring sets (PSS) representing broad springs series typical for the Cvrcka River basin, aggregates 26 springs (Appendices 2 and 4). It was used to recognize general pattern of assemblages, and macrohabitats quality. Springs S 3, S 6 from PSS set and additionally site S 31 were sampled seasonally in spring, summer and autumn. They formed together EHSS spring set (Appendices 3 and 5) and were analyzed separately to find ecological distinctness between eucrenon and hypocrenon microhabitats. Chironomids from PSS were collected during September and October 2012 and 2013 (Appendix 2). From EHSS near Rastik village chironomids were taken seasonally during the year, specific for the source (eucrenal) and water flow directly downstream (hypocrenal) (Appendix 3). Samples were collected with a hand net (350 ¯m mesh apertures) from all the microhabitats of the investigated springs. All the collected chironomids were preserved in 96% ethanol.

2.3 Environmental variables

Water temperature and pH values were measured with pH-meter HI 98127 accuracy 0.1, air temperature with thermometer accuracy 0.5 °C, conductivity with conductometer Nahita accuracy 2 cF and oxygen concentration with oximeter HI 9142 accuracy 0.1 mg·L-1. Spring positions were recorded with GPS Oregon 550. Water discharge was determined by eye and grouped in classes: 1 (<1 L·min-1), 2 (>1 and <5 L·min-1), 3 (>5 and <20 L·min-1) according to Fumetti et al. (2006). Substrate types were categorized in five classes of frequency: 0 (absent), 1 (little), 2 (medium), 3 (much), 4 (throughout) according to Hahn (2000).

2.4 Material identification

The material was determined mostly with Moller Pillot and Klink (2003) and Brooks et al. (2007). Ecological interpretation of taxa occurrence and their environmental preferences follow Moller Pillot (2009a, 2009b, 2013), Vallenduuk and Moller Pillot (2007), Wiederholm (1983), Moller Pillot and Klink (2003) and Brooks et al. (2007).

thumbnail Fig. 2

(A) Similarity distance between sites in groups A, B and C reflecting environmental characteristics of the PSS. (B) Bray-Curtis similarity of Chironomidae assemblages within the PSS.

thumbnail Fig. 3

(A) Results of PCA showing environmental characteristics of the PSS under classification into abiotic defined groups A, B, C. (B) Results of PCA showing environmental characteristics of the PSS under biotic classification into groups I, II, III, O (outliers).

thumbnail Fig. 4

Results of CCA for the PSS.

2.5 Statistical analyses

Multivariate statistics were performed for ecological interpretation of the data. Centered and standardized environmental data from the PSS were classified by Euclidean Distance similarity index and illustrated by complete linkage dendrogram (Figure 2A). For classification of biota samples, Bray-Curtis similarity index on the square root transformed data was used, its results are illustrated by group average dendrogram (Figure 2B). PCA for PSS was undertaken on centered and standardized environmental data to recognize habitat diversification of the site groups used in the previous cluster analysis. Its results are presented on Figure 3, at first with marked by different colors groups of sites distinguished with environmental classification (Figure 3A, compare with Figure 2A) and secondly with sites marked after biota assemblages classification (Figure 3B, compare with Figure 2B). This is only picturing treatment, both plots (Figures 3A and 3B) illustrate the same mathematically PCA. SIMPER analysis was performed to test differences within faunal composition of the above mentioned groups A, B and C, and I, II and III (Table 3). Detrended Correspondence Analysis (DCA) was done to recognize variability gradient. As there were more than 7.1 SD units on the first two DC axes, Canonical Correspondence Analysis (CCA) was performed to find an environmental relation in taxa distribution among the samples (Figure 4, Appendix 6). Rare species were downweighted with method available in CANOCO 4.5 software. Biotic data for CCA were previously log transformed. Branches and algae were excluded from the analysis due to autocorrelation.

Because of low abundances (see Appendix 8) eukrenon-hyopocrenon biotic data were not transformed. Because CCA didn’t gave satisfactory results for EHSS data, Non-Metric MultiDimensional Scaling (NMDS) was performed on Bray-Curtis similarity index with 25 restarts, to find a general biota compositional pattern among the samples (Figure 5). Similarity Percentage (SIMPER) analysis was done to test differences between eucrenon and hypocrenon fauna (Table 4). Principal Component Analysis (PCA) was performed on centered and standardized environmental data to find diversification of the eucrenon and hypocrenon sampling sites (not illustrated).

Shannon diversity index was calculated on both EHSS and PSS data sets. Statistical differences for diversity index between the groups were analyzed by the t-test for the EHSS data set and the ANOVA for the PSS data set.

Canoco 4.5 statistical software was used for computing DCA and CCA, C2 software for centering and standardizing environmental data (except for CCA computed by Canoco) and PRIMER 6 for all the other multivariate analysis.

thumbnail Fig. 5

Results of the NMDS analysis showing a general gradient in chironomid assemblages in the eucrenon-hypocrenon spring zone.

3 Results

3.1 Environmental features in the springs

Water temperature of the PSS (S 2S 48) ranged between 7.9 and 17.1 °C (mode: 13.9 °C) with coefficient of variation 19.20% and air temperature near the spring ranged between 15.0 and 27.0 °C (mode: 17.0 °C) with coefficient of variation 18.36%. All the springs which belong to the PSS had alkaline pH value which varies around a mean of 7.83 ± 0.22 from 7.3 to 8.2 with coefficient of variation 2.82%. Conductivity of the PSS ranged between 3 and 5 cF (mean ± SD: 3.85 ± 0.67 cF) with coefficient of variation 17.55% and oxygen concentration varied around a mean of 6.75 ± 1.11 mg·L-1 from 4.0 to 8.5 mg·L-1 with coefficient of variation 16.41%.

Table 1

Physical and chemical characteristics of the EHSS.

Descriptive statistics of physical and chemical characteristics of the EHSS were analyzed by spring parts (Table 1).

Discharge at both site sets (PSS and EHSS) ranged from <1 L·min-1 to >5 and <20 L·min-1. Substrate composition of the PSS consisted of: anoxic mud, detritus, leaf litter, dead branches, moss, roots, macrophytes, clay, sand, gravel, stones, lime sinter, calcareous sinter, algae and waste materials (Appendix 4). Except algae and waste materials, all the substrate components were present in the EHSS, too (Appendix 5).

3.2 Assemblage composition

473 specimens from 23 taxa were collected from the PSS (S 2S 48) in September and October 2012 and 2013 (Table 2). They represented four chironomid subfamilies (Tanypodinae, Prodiamesinae, Orthocladiinae and Chironominae). Subfamily Orthocladiinae accounted for 52% (12 taxa) of the total, followed by Chironominae (seven taxa or 30%), Tanypodinae (three taxa or 13%) and Prodiamesinae (one taxon or 4%).

All the collected chironomids were larvae. From one to seven taxa were found per spring. Only two springs (S 40 and S 41) hosted more than 50 individuals. The most frequent taxon was Micropsectra type A (87 specimens present in 12 springs or 46% of the total 26 springs with chironomids) and the most abundant taxon was Chironomus (252 individuals).

140 specimens from 15 taxa, including larvae and singular pupal exuviae, were collected from springs S 3, S 6 and S 31 (EHSS) (Table 2). Chironomidae were collected from 16 or app. 67% of the total 24 samples (Appendix 3). From one to five taxa were found per sample. Only one sample (e3103) hosted more than 20 individuals. The most frequent and the most abundant taxon was Prodiamesa olivacea (present in eight or 50% of the total 16 samples with chironomids) with 36 collected individuals.

3.3 Community patterns

Altogether 26 springs from the PSS may be divided into three groups (A, B and C) according to environmental conditions (Figure 2A).

To recognize environmental patterns in PSS, PCA was performed. The first, second and third PC axes explain respectively 21.8%, 17.3% and 10.6% variation of environmental variables. Results of PCA on the PSS (Figure 3A) show that the sites in group A reveal a strong gradient in waste and algae amount. These sites are characterized by intermediate values and near 0 variation in temperature, discharge, macrophyte occurrence and calcium content, as well as by high content of anoxic mud and low concentration of lime stones. The sites from group B are distinct in high macrophyte abundance and calcium content. These sites reveal higher water temperature but lower discharge than groups A and C, intermediate to low algae and waste amount, the highest lime stone concentration and the lowest amount of anoxic mud. The sites from group C manifest a relatively small variation of sediment composition (lime stones to anoxic mud), high discharge, macrophyte and calcium concentration and low temperature. Table 3 presents taxa mostly associated for each of site groups and dissimilarity in taxonomic composition between each of the groups. Micropsectra type A is characteristic for groups A and C. Chironomus is characteristic for the sites from group A, Prodiamesa olivacea show higher contribution to group C, whereas Paraphaeonocladius type A and Brillia bifida are characteristic for group B.

The chironomid assemblages from the PSS may be divided into three groups (Figure 2B).

Most of the springs aggregates in group II, two smaller supplementary groups are I and III. Outliers encompasses 4 sites (S 44, S 40, S 41 and S 20) which do not belong to any cluster. PCA (Figure 3B) shows environmental conditions that favor such defined communities recorded at the study sites. Assemblages of the springs in group I form on the lime stone bottom, species belonging to communities I avoid anoxic mud. Algae and waste do not seem to correlate to occurrence of this group, while temperature, discharge, amount of calcium and macrophyte presence reveal a strong gradient within the sites of group I. The communities from group II are present on diverse bottom from anoxic mud to lime stones habitats. They reveal a strong variation along discharge, temperature, macrophyte amount and calcium content values. The species from this group clearly avoid waste and algae. The species from group III occur generally on the lime stone bottom, without anoxic mud content and do not seem to have a clear preference in terms of discharge, temperature, waste, algae and macorphye appearance. The outlier assemblages reveal a stronger correlation with algae and waste appearance. The species from this group prefer higher discharge, lower temperature and avoid habitats with macrophytes but reveal a strong variation according to anoxic mud and lime stone content.

Table 3 clearly indicates that the community groups specified in the biotic site classification (I, II, III) are much better defined, have higher internal similarity and are more dissimilar to each other than assemblages of A, B and C groups separated it on the habitat site classification. Brillia bifida and Rheocricotopus effusus are characteristic representatives of assemblages type I., while Micropsectra type A and Prodiamesa olivacea are distinct for assemblages type II. Paraphaenocladius type A and Zavrelimyia are typical of springs from group III and Chironomus separates outliers from the others.

Table 2

List of Chironomidae taxa collected in all the investigated spring sites.

Table 3

A) Results of SIMPER analysis for PSS assemblages of site groups A, B and C. B) Results of SIMPER analysis for PSS assemblages of site groups I, II, III and O (outliers).

ANOVA found significant difference (P = 0.0001) for the Shannon diversity index between PSS assemblages of site groups I, II and III. Highest diversity reveal assemblage type II (mean: 1.19, SD: ±0.35), lowest assemblage type I (mean: 0.35, SD: ±0.45), intermediate values keeps type III (mean: 0.53, SD: ±0.30).

Results of CCA (Figure 4, Appendix 6) summarize main trends of chironomid-environmental relation. The first two axes explain 32.5% of species-environment relation. Two environmental factors significantly influence chironomid communities: stones (explaining 6.98% of variation with P = 0.012) and elevation (explaining 7.34% of variation with P = 0.014). The factor which has almost a similar significance in terms of influence on chironomid communities is oxygen concentration (explaining 5.19% of variation with P = 0.11). Ten factors are associated with Axis 1: elevation and detritus positively, while stones, moss, gravel, sand, air temperature, clay, leaf litter and water temperature negatively. Two factors are associated with Axis 2: oxygen concentration positively and conductivity negatively. Discharge is associated with Axis 1 and Axis 2 positively. Although most of the environmental factors, including significant ones, are associated with Axis 1, they differentiate only assemblages of springs from 40 and 41 from outliers and taxa Chironomus and Limnophyes from all the other assemblages and species. Chironomus and Limnophyes tend to occur on higher elevated sites more enriched by detritus. According to CCA, all the other taxa are more associated with lower elevated sites with the mineral bottom, including coarse fractions such as stones, leaf litter and moss. These taxa are found in higher temperatures. A much stronger variation is revealed by taxa and assemblages according to the gradient in oxygen concentration and conductivity. Axis 2 divides assemblages from group I, which is associated with higher oxygen concentration and lower conductivity, from assemblages II, which are more related to higher conductivity and appear in lower oxygen concentration. Groups III and outliers reveal intermediate oxygen and conductivity conditions.

3.4 Eucrenon-hypocrenon distinctness

The analyzed environmental EHSS data do not provide clear separation of the eucrenon and hypocrenon zone. PCA indicates that eucrenon sites (not illustrated) reveal slightly higher values of temperature and macrophyte amount, while hypocrenon stretches have higher oxygen concentration, branches and sand on the bottom but this pattern is very weak and insignificant. According to community composition, they have clearly distinct assemblages (Figure 5). Hypocrenon communities manifest a strong gradient in assemblage composition from near similar to eucrenon to very distinct from one, whereas eucrenon assemblages are more concentrated.

Prodiamesa olivacea and Paraphaenocladius type A separate eucrenon from hypocrenon zone communities (Table 4) but Micropsectra type A inhabits both types of mesohabitats. Both zones do not differ clearly in biodiversity and species richness. Eucrenon assemblages seem to reveal higher larvae abundance, whereas hypocrenon communities reveal slightly higher evenness.

A t-test found no significant difference in mean values for Shannon diversity index between eucrenon and hypocrenon (P = 0.250).

4 Discussion

Chironomidae larvae are an important component of mountain spring communities in the Balkan Region (Mori and Brancelj, 2006) and other European countries (Wagner et al., 1998). As many as 20% of all chironomid species appear in spring habitats in the Holarctic region (Ferrington, 1998). In 27 springs of Cvrcka valley, there were 23 taxa recorded, whereas in the Italian Alps the number of species ranges from 81 taxa collected from 124 springs (Lencioni et al., 2012) to as many as 104 species/groups in 81 springs (Lencioni et al., 2011). Although it is difficult to distinguish truly crenobiotic species, many chironomid taxa are recognized to be crenophilous (Marziali et al., 2010; Lencioni et al., 2011). Therefore, they have a higher potential for spring bioassessment and conservation than other insects. Nevertheless, Lencioni et al. (2011) and Lencioni et al. (2012) report only few taxa to achieve high abundance and frequency within their site sets. As in the Dinaric Mountains, in the Alps and other Holarctic localities, Orthocladiinae are the species richest group (Ferrington, 1998; Marziali et al., 2010), whereas in Cvrcka River valley the presence of Diamesinae was not recorded. This may indicate some degradation of springs in this valley compared to the Alpine highlands (Lencioni et al., 2011). The midge fauna of mountain springs is relatively diverse. Species richness tends to increase from the uplands to mountain elevations 12502250 m a.s.l., due to higher habitat heterogeneity (Lencioni et al., 2011, Lencioni et al., 2012).

Table 4

Results of SIMPER analysis for EHSS assemblages.

The research in Cvrcka River valley prove that environmental and biotic classification of springs may not match. Environmental classification provides three clear groups of sites which indicate human impact on the habitat, landscape transformation and spring typology. Springs which belong to group A are under a strong human influence, particularly springs S 39, S 40 and S 41, which are captured springs in the central part of villages and their water is extensively used for drinking and watering livestock. Spring S 27 and S 6 are also captured, but they are located outside villages. Rheocrene springs S 3 and S 4 are located on the forest edge near Rastik village. All the other springs avoided a direct human impact. Most of the springs from groupB are located in a valley with a deciduous forest. Some of the springs are captured, but they are not in use. Most of the springs from group C are upstream (S 46 and S 48) or downstream (S 2, S 7, S 9 and S 32) in relation to Cvrcka River canyon. They are more easily accessible to people compared to the springs from group B, but their water is not used intensively, due to the fact that most of them are located in the forest. Lencioni et al. (2011, 2012) and Ivković et al. (2015) prove human impact on terrestrial spring surroundings and canopy cover has a strong influence on midge communities. Nevertheless, chironomid communities in Cvrcka valley divide sites into three groups and this biotic classification does not match the one based solely on environmental characteristics. Midge communities are also much more dissimilar than springs according to their environmental character. High faunistic dissimilarity between springs, even located nearby, is indicated by Lencioni et al. (2011). PCA indicates that midge communities in the Dinaric Mountains are strongly correlated to the bottom character, whereas such conditions as temperature and discharge are variable within assemblage types. Algae and waste are an important factor that influences species composition. Peryphyton is an important food supply for many midge species. Waste is often an artificial substrate for algae, especially if the natural bottom is composed of fine sediments. Algal vegetation is also enhanced by supply of nutrients, therefore eutrophicated, garbled springs should have specific chironomid fauna. It is symptomatic that communities type II, which reveal highest diversity, do not exist in garbled springs with ample algae vegetation. Assemblage II with Micropsectra and Prodiamesa olivacea seems to be natural, typical for the Cvrcka River basin, as it comprises the highest number of sites. Prodiamesa olivacea is also the most common species in springs in the Volga basin (Chuzhekova, 2014). It is likely that communities type I with Brillia bifida and Rheocricotopus effusus as well as III with Paraphaenocladius and Zavrelimyia inhabit two accessory natural spring types, and their occurrence depends on oxygen saturation and bottom type. Outliers reveal strong Chironomus domination. They are rheocrenes of cold, fast flowing water on higher elevation. They seem to be less typical for Cvrcka valley and associated with more garbled sites with ample algae vegetation. Springs S 40 and S 41 are situated in a village. These are huge captured springs with a high flow rate. Spring S 20 is located in the forest but in proximity of a settled area. Spring 44 is located in a small cave. This habitat diversity can be the reason why its assemblages do not aggregate with any other. CCA clearly separates sites of higher Chironomus and Limnophyes domination as being higher elevated, with more detritus on the bottom. A similar pattern was found in the Evortas River basin (Southern Greece). The mountain spring assemblages revealed higher Chironomus domination. Limnophyes and Chironomus tend to co-occur in the Evortas springs in more degraded sites (Karaouzas and Płóciennik, 2016). Ferrington (1998) indicates that springs influenced by human impact, frequented by cattle, are inhabited be taxa typical to lower-order enriched streams and have higher domination of Chironomini, namely Chironomus species. Lencioni et al. (2012) indicate Limnophes to be also associated with captured springs. This species prefers the hygropetric zone in limnocrenes and appears on the rocky bottom with bryophytes (Lencioni et al., 2011). Barquín and Death (2004) suggest that moss mats may accumulate detritus and provide good habitat for algaedevelopment. This may explain higher dominance of the above mentioned taxa in some of the springs, disturbed and natural as well. All the other species recorded in Cvrcka valley are associated with lower elevation and the stony bottom with a more mineral fraction. It is symptomatic that only stones and elevation shaped assemblages to a statistically significant degree. Factors such as presence of hard bottom, temperature, current and stream permanence associated with these two significant factors might have an indirect influence on the communities. Elevation and temperature are factors influencing chironomid communities on the broad, geographical scale (Ferrington, 1998). Mori and Brancelj (2006), Marziali et al. (2010) and Lencioni et al. (2011, 2012) indicate altitude, peryphiton, sediment quality, temperature and flow character to be the main drivers of biotic diversity in springs. In the Italian Alps, there is a strong positive correlation of habitat quality and chironomid diversity with altitude. Lencioni et al. (2012) find bed modification to cause diversity decrease whereas moderate eutrophication to favor species richness. In fact, all the other communities and species in Cvrcka River springs are more spread along the second CCA axis. Oxygen concentration and conductivity may play an important role while they remain insignificant according to the Monte Carlo Permutation test. We suppose they may be underestimated in this case. Communities II aggregating sites typical of Cvrcka valley occur in higher conductivity and lower oxygen concentration, whereas types I and III appear usually in better oxygen conditions and lower conductivity. Assemblages variability along the second CCA axis may in fact reflect water chemical composition. We have only information on pH, oxygen concentration and conductivity but other compounds such as nutrients and/or e.g.: sulfides, not measured, may have an influence on chironomids. In the Italian Alps (Marziali et al., 2010, Lencioni et al., 2011, 2012) pH, conductivity and water trophy are primary conditions differing highland pristine springs from upland disturbed ones. This pattern is not so relevant in boreal springs where mean annual temperature changing through climatic zones in a longitudinal gradient plays the main role. Ferrington (1998), Staudacher and Füreder (2007) draw attention to microhabitat complexity as the main driver of aquatic insect species composition, biodiversity and abundance. In the Eastern Alps, microhabitat heterogeneity and moister of the spring zones – from fully aquatic, semiaquatic, to terrestrial – is linked to insect diversity. Chironomidae were spread through all those zones. In Eastern Alpine springs, chemical factors (such as conductivity) and altitude have only a weak influence on invertebrate communities (Staudacher and Füreder, 2007). Species composition and community structure manifest variability not only between spring types spread along Cvrcka valley but also in microhabitats within springs. In this study, no differences in diversity or species richness were observed between eu- and hypocrenon. Mc Cabe (1998) reviews a number of examples from North America and Europe where a decrease or an increase of species richness with distance from the source was observed, so there is no general pattern, whereas individual gradients in species distribution were commonly observed. Rheocrene springs are proved to contain diverse niches and are species rich in chironomids (Lencioni et al., 2012) and other insects (Cianficconi et al., 1998). It is difficult to separate clearly defined types of springs, a gradual transition from one spring type to another is what can be observed instead (Lencioni et al., 2011). NMDS and SIMPER analyses show that eucrenon and hypocrenon have different community composition in Cvrcka valley. Eucrenon assemblages are more specific due to higher uniformity of such habitats. Hypocrenon assemblages reveal a gradient ranging from more similar to more distinct from eucrenon. This is visible in the characteristic species groups for these two kinds of mesohabitats. In other studies Prodiamesa olivacea species was found in helocrenes and rheo-limnocrenes, Micropsectra species was recorded in the hygropetric zone with mineral sediment and bryophytes, Paraphaenocladius is usually found in brooks and telmatic margins of spring on the soft bottom, whereas Apsectrotanypustrifascipennis and Rheocricotopus effusus are typical for soft sediments in small flowing waters and helocrenes (Moller Pillot, 2013; Vallenduuk and Moller Pillot, 2007; Lencioni et al., 2011). Clear differences in assemblage composition indicated by NMDS and SIMPER are not confirmed by PCA which does not confirm environmental differences between these two kinds of habitats.

5 Conclusions

The investigated springs defy simple classification. Communities reflect well environmental parameters measured, but the environmental parameters alone do not give information how the community uses them. Whereas habitat structure, namely bottom composition, discharge and temperature, may explain to some extend community diversification, in this case only elevation and hard-bottom availability were significantly important factors. It seems that other, chemical factors, such as oxygen concentration, nutrients or diverse compounds responsible for conductivity that influence groundwater quality, may also play an important role for chironomids in springs in the Dynaric Mountains, but only investigation of a larger area and more detailed environmental data may prove that. Ecology of Balkan Peninsula springs remains relatively poorly recognized compared to temperate Europe, Apennine and Iberian Peninsulas. Unique climatic and geological conditions indicate a significant need for broader research of spring fauna of the region, especially due to the role which it plays in karstic landscape. Chironomidae are a key group of habitat quality indicators especially on the species level. Taxa, which here were recognized to be ‘characteristic’ for certain habitat quality, comprise high number of species (e.g. Chironomus, Limnophyes, diverse Micropsectra morphotypes) and are only ecological units. They leave only restricted space for exact interpretation or an ecological relation of environment and community. Further studies in the region should pay more attention to a wide database (including also a robust number of individuals) and high taxonomical resolution.

Acknowledgments

We would like to thank Slaven Filipović, Goran Šukalo and Siniša Škondrić for help in the field works to Rafal Szperna and Paulina Wyszkowska for Laboratory works and professional translator Marta Koniarek for linguistic correction.

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Cite this article as: M. Płóciennik, D. Dmitrović, V. Pešić and P. Gadawski, 2016. Ecological patterns of Chironomidae assemblages in Dynaric karst springs. Knowl. Manag. Aquat. Ecosyst., 417, 11.

Appendices

Appendix 1

General characteristics of springs sampled along the Cvrcka River mainstream. The spring code follows general spring classification according to benthological studies in the Cvrcka River.

Appendix 2

Date of sampling at PSS (S 2–S 48) in September and October 2012 and 2013.

Appendix 3

Date of sampling at three springs (S 3, S 6 and S 31) (EHSS) by spring parts (eucrenal and hypocrenal) and four seasons during 2013.

Appendix 4

Physical and chemical characteristics from measurements in September and October 2012 and 2013 and substrate composition of 26 investigated springs (PSS) (S2S48) of the Cvrcka river basin. Discharge (estimated by eye): 1 (<1 L·min-1), 2 (>1 and <5 L·min-1), 3 (>5 and <20 L·min-1). Substrate type classes of frequency: 0 (absent), 1 (little), 2 (medium), 3 (much), 4 (throughout).

Appendix 5

Physical and chemical characteristics from measurements during 2013 and substrate composition of three investigated springs (S3, S31 and S6) (EHSS) of the Cvrcka river basin which are analyzed by seasons and spring parts. Discharge (estimated by eye): 1 (<1 L·min-1), 2 (>1 and <5 L·min-1), 3 (>5 and <20 L·min-1). Substrate type classes of frequency: 0 (absent), 1 (little), 2 (medium), 3 (much), 4 (throughout).

Appendix 6

Main parameters of CCA for the PSS.

Appendix 7

List of Chironomidae species and number of individuals collected at 26 springs representing the PSS (S 2S 48) in September and October 2012 and 2013.

Appendix 8

List of Chironomidae species and number of individuals collected at three springs (S 3, S 6 and S 31) representing EHSS by spring parts (eucrenal and hypocrenal) at four seasons during 2013.

All Tables

Table 1

Physical and chemical characteristics of the EHSS.

Table 2

List of Chironomidae taxa collected in all the investigated spring sites.

Table 3

A) Results of SIMPER analysis for PSS assemblages of site groups A, B and C. B) Results of SIMPER analysis for PSS assemblages of site groups I, II, III and O (outliers).

Table 4

Results of SIMPER analysis for EHSS assemblages.

Appendix 1

General characteristics of springs sampled along the Cvrcka River mainstream. The spring code follows general spring classification according to benthological studies in the Cvrcka River.

Appendix 2

Date of sampling at PSS (S 2–S 48) in September and October 2012 and 2013.

Appendix 3

Date of sampling at three springs (S 3, S 6 and S 31) (EHSS) by spring parts (eucrenal and hypocrenal) and four seasons during 2013.

Appendix 4

Physical and chemical characteristics from measurements in September and October 2012 and 2013 and substrate composition of 26 investigated springs (PSS) (S2S48) of the Cvrcka river basin. Discharge (estimated by eye): 1 (<1 L·min-1), 2 (>1 and <5 L·min-1), 3 (>5 and <20 L·min-1). Substrate type classes of frequency: 0 (absent), 1 (little), 2 (medium), 3 (much), 4 (throughout).

Appendix 5

Physical and chemical characteristics from measurements during 2013 and substrate composition of three investigated springs (S3, S31 and S6) (EHSS) of the Cvrcka river basin which are analyzed by seasons and spring parts. Discharge (estimated by eye): 1 (<1 L·min-1), 2 (>1 and <5 L·min-1), 3 (>5 and <20 L·min-1). Substrate type classes of frequency: 0 (absent), 1 (little), 2 (medium), 3 (much), 4 (throughout).

Appendix 6

Main parameters of CCA for the PSS.

Appendix 7

List of Chironomidae species and number of individuals collected at 26 springs representing the PSS (S 2S 48) in September and October 2012 and 2013.

Appendix 8

List of Chironomidae species and number of individuals collected at three springs (S 3, S 6 and S 31) representing EHSS by spring parts (eucrenal and hypocrenal) at four seasons during 2013.

All Figures

thumbnail Fig. 1

Map of the study area.

In the text
thumbnail Fig. 2

(A) Similarity distance between sites in groups A, B and C reflecting environmental characteristics of the PSS. (B) Bray-Curtis similarity of Chironomidae assemblages within the PSS.

In the text
thumbnail Fig. 3

(A) Results of PCA showing environmental characteristics of the PSS under classification into abiotic defined groups A, B, C. (B) Results of PCA showing environmental characteristics of the PSS under biotic classification into groups I, II, III, O (outliers).

In the text
thumbnail Fig. 4

Results of CCA for the PSS.

In the text
thumbnail Fig. 5

Results of the NMDS analysis showing a general gradient in chironomid assemblages in the eucrenon-hypocrenon spring zone.

In the text

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