Oligochaete Communities Research Articles

Assessing the diversity of the benthic oligochaete communities in urban and woodland ponds in an industrial landscape (Upper Silesia, southern Poland)

Studies were carried out in two mining pond complexes in an industrial landscape. The first complex (consisting of six ponds) was located in an urban area and the second one (consisting of six ponds) in a woodland area. The aims of the study were to assess the diversity of benthic oligochaetes and to evaluate which environmental variables are most important in determining variations in the community structure in ponds of varying location. In total, 21 oligochaete species were recorded (7–11 in the urban ponds, 11–15 in the woodland ponds). Aulodrilus pluriseta, Aulodrilus japonicus and Ophidonais serpentina were only found in the woodland ponds, while Potamothrix bavaricus only occurred in the urban ponds. Limnodrilus hoffmeisteri, Limnodrilus claparedeanus, Chaetogaster diaphanus and Ophidonais serpentina dominated in the woodland ponds, whereas Limnodrilus hoffmeisteri, Limnodrilus claparedeanus, Potamothrix bavaricus and Tubifex tubifex prevailed in the urban ponds. The total density of oligochaetes was higher in the urban ponds thought the values of the diversity indices were higher in the woodland ponds. The local diversity of the ponds was high, while the among-site diversity made only a small contribution to the regional diversity. Nonetheless, a cluster analysis divided all of the ponds into two distinct groups depending on their location. CCA analysis showed that conductivity, pH, total hardness, alkalinity, the concentration of chlorides and the content of organic matter in the bottom sediments were most associated with the distribution of some oligochaete species among the ponds studied.

Next-Generation Sequencing of Aquatic Oligochaetes: Comparison of Experimental Communities.

Aquatic oligochaetes are a common group of freshwater benthic invertebrates known to be very sensitive to environmental changes and currently used as bioindicators in some countries. However, more extensive application of oligochaetes for assessing the ecological quality of sediments in watercourses and lakes would require overcoming the difficulties related to morphology-based identification of oligochaetes species. This study tested the Next-Generation Sequencing (NGS) of a standard cytochrome c oxydase I (COI) barcode as a tool for the rapid assessment of oligochaete diversity in environmental samples, based on mixed specimen samples. To know the composition of each sample we Sanger sequenced every specimen present in these samples. Our study showed that a large majority of OTUs (Operational Taxonomic Unit) could be detected by NGS analyses. We also observed congruence between the NGS and specimen abundance data for several but not all OTUs. Because the differences in sequence abundance data were consistent across samples, we exploited these variations to empirically design correction factors. We showed that such factors increased the congruence between the values of oligochaetes-based indices inferred from the NGS and the Sanger-sequenced specimen data. The validation of these correction factors by further experimental studies will be needed for the adaptation and use of NGS technology in biomonitoring studies based on oligochaete communities.

Assessment of the restoration measures in a man-made reservoir: do oligochaete communities respond to the improvement of water quality?

Studies were carried out in a man-made reservoir that was undergoing restoration using selective hypolimnetic withdrawal (Pławniowice reservoir, Southern Poland). The aim of the research was to assess the changes in the composition of oligochaete fauna in relation to water quality and to estimate whether indices based on oligochaetes may be useful in the assessment of a reservoir's recovery from eutrophication. Samples were collected in the first, fifth, and eighth year of the restoration during the summer stratification at 22 sites along six transects that covered depths from 2 to 15 m. The results of the survey indicated an improvement in some physical and chemical water parameters in respect to those during the period prior to the restoration measures. The present study showed an increase in the oligochaete diversity and a decrease in their abundance accompanied by a shift toward a larger share of taxa that are characteristic of mesotrophic and oligotrophic conditions. This study detected slow changes in the values of the trophic indices based on oligochaetes toward mesotrophic conditions. Discriminant analysis, performed using stepwise forward selection, demonstrated a good separation of samples from 2004 and 2011 according to trophic condition (TC) and biotic quality index (BQI) indices. The present data shows that metrics based on Oligochaeta may be useful for detecting changes in the trophic status.

New data on the biology and habitat preferences of the oligochaete species Ripistes parasita (Annelida: Clitellata: Naididae): a case study in a temporary woodland pond

AbstractStudies carried out in woodland ponds located in an industrial area of southern Poland revealed the occurrence of a large population of Ripistes parasita (Schmidt, 1847) in one of them. This is a naidid species that is not usually abundant in oligochaete communities. Its ecology and biology is poorly known and thus the aim of this study was to characterise the environmental conditions influencing the occurrence of R. parasita and to assess its population dynamics and life history pattern. R. parasita occurred in a pond with soft water and a low level of mineralisation, a pH ranging from 6.1 to 7.0, and a high content of nitrogen and phosphorus. During our investigation, considerable seasonal changes in the occurrence and population density were detected. Specimens of this species inhabited alder leaf deposits in winter and early spring while in summer and autumn they occupied in large number floating Nuphar lutea leaves. A stepwise regression analysis showed a relationship between the temperature and dissolved oxygen content in the water and the density of R. parasita. The R. parasita reproduced asexually by paratomy (between May and November). The mean doubling time (days) for the population was 22.4. Only a few individuals (less than 1% of the population) matured in September and October.

<b>Partitioning beta diversity of aquatic Oligochaeta in different environments of a Neotropical floodplain

We tested the hypothesis that the contribution of the nestedness component is higher in environments with more similar features (lentic or lotic), whereas the contribution of the turnover component is higher in environments with more dissimilar features (lotic vs. lentic). To this end, we partitioned beta diversity of the Oligochaeta community into 12 environments of the Upper Parana River floodplain. We recorded 986 individuals of 17 taxa. Through Redundancy Analysis, we observed a differentiation between lentic and lotic habitats both by environmental features as species composition. Our hypothesis was partially supported, because in environments with more similar hydrological characteristics, we observed a greater contribution of the nestedness component only in lentic environments, whereas in lotic environments, the turnover component showed a higher value. Moreover, when analyzed the different environments (lentic vs. lotic), we noticed a very similar contribution of both components. Some species were more frequent, as A. pigueti and P. americana, while others were exclusive to some environments (N. bonettoi and H. aedeochaeta). We evidenced the importance of each component in structuring Oligochaeta community, nonetheless, in a different way between environments with more similar (nestedness to lentic and turnover to lotic) or dissimilar (almost the same contribution of both) features.

Utilisation des communautés d’oligochètes pour l’évaluation de la qualité biologique et du fonctionnement des cours d’eau : un bilan à partir de données genevoises (Suisse)

Use of oligochaete communities for the assessment of the biological quality and the functioning of watercourses : a review of data from the Geneva area (Switzerland). – Oligochaetes are used in some cantons in Switzerland to assess the biological quality of watercourse and lake sediments. The oligochaete index of sediment bioindication (IOBS) allows to assess the quality of fine/sandy sediments of watercourses, while the Functional traits method (TRF) is dedicated to assess the quality of surficial coarse sediments and of the hyporheic zone. The TRF method also allows to know the dynamics of hydrological exchanges between surface water and groundwater. In the Geneva area, the IOBS index was applied in routine from 2008 to 2013 (92 samples) and the TRF method was tested in 2012 and 2013. The IOBS index proved to be a good bioindicator of chemical quality of the sediments. Metal toxicity thresholds in sediments were established and proposed. The implementation of the IOBS index in complement to the Swiss Biotic Index (IBCH) allowed to refine the ecological diagnostics. The TRF approach proved to be of great interest to simultaneously assess the biological quality of coarse habitats and of the vertical hydrological exchanges. The IOBS and TRF methods should be more integrated in the monitoring programs of watercourse quality. The current development of methods based on the identification of oligochaetes using genetic barcodes could allow to overcome the problems related to the morphological identification of species and a wider use of oligochaetes as bioindicators.

Oligochaete Community Structure in Paddy fields and Channels in Kole paddy fields, Vembanad Kole wetland, India.

Benthic invertebrates including oligochaetes are important components of paddy field fertility due to its significant role in organic matter decomposition and nutrient translocation, but have been studied less. The oligochaete community structure in paddy fields and channels/agricultural ditches of Kole wetlands (a part of Vemband Kole wetlands, a Ramsar site on the south west coast of India) was studied during Punja (summer crop season- January to May 2011). The benthic fauna belonged to the phyla Mollusca, Annelida and Arthropoda. Fifteen oligochaete species of family Naididae, Tubificidae and Lumbriculidae were identified. Seven taxa; Aulodrilus pluriseta, Aulodrilus sp., Aulodrilus piguiti, Branchiodrilus semperi, Stephensonia trivandriana, Pristinella minuta and Pristinella jenkinae were present both in the paddy fields and channels. Six species; Allonais gwaliorensis , Allonais paraguensis, Dero zeylanica, Pristinella accuminata, Pristina menoni, Lumbriculus variegates were exclusively found in the channels and two taxa; Branchiodrilus hortensis, Homochaeta sp. exclusively in the paddy fields. ANOSIM results revealed a similarity in oligochaete composition among paddy fields and channels (Global R=0.19, p>0.05); the lack of environmental specialization in aquatic oligochaetes could be a reason for this. Abundance significantly varied among them, a lower abundance observed in paddy fields (102±161 ind/m 2 ) than channels (891±1409 ind/m 2 ) (ANOVA F 1, 24 =6.02, p<0.05). Less habitable area in paddy field due to the compartmented substratum by paddy root structures resulted in a reduced abundance in paddy fields. Species richness and diversity showed no significant variation but evenness showed a significant variation between paddy fields and channels (ANOVA F 1, 8 =10.40, p<0.05). As oligochaetes are characterized by less dispersal and migration ability evenness component would have been more sensitive than other diversity indices.

Influência de variáveis ambientais sobre a comunidade de oligoquetos (Annelida: Clitellata) em um córrego neotropical

Among the organisms of the benthic community, oligochaetes play a key role in the energy low and recycling of organic matter in aquatic ecosystems, where their distribution is mainly influenced by local hydrological patterns. Thus, this study aimed to investigate the influence of environmental variables on the community of limnic oligochaetes in a neotropical lotic system. Galharada stream is located within the Campos do Jordão State Park (PECJ), in the state of São Paulo, Brazil, 1,600 m above sea level; 192 samples were collected from 4 sites selected according to their hierarchical order within the river basin (first to fourth order). To correlate the environmental variables to the oligochaete fauna, the Canonical Correspondence Analysis (CCA) was performed. We identified 16 species divided into 4 families (Enchytraeidae, Naididae, Pristinidae, and Tubiicidae). The results of CCA revealed that the physical characteristics of stretches, such as stream depth and width, low speed, and low rate were the factors that most inluenced on the structure of the aquatic Oligochaeta community in Campos do Jordão. The species Aulodrilus limnobius and Nais communis were considered along with the variables electrical conductivity and turbidity, indicating a possible association with environments enriched with organic matter. The occurrence of Enchytraeidae, Pristina rosea, Chaetogaster diastrophus, Pristina proboscidea, and Limnodrilus hoffmeisteri was seemingly uncorrelated to the environmental variables analyzed in this study. Our findings reinforce using the Oligochaeta community as bioindicators, by participating in the environmental assessment of continental aquatic ecosystems.

Tributaries as richness source for Oligochaeta assemblage (Annelida) of Neotropical dammed river.

Tributaries may serve as richness source for the river main channel and the zoobenthos community is a good tool to verify this kind of pattern. In this study, we aimed to characterize the benthic invertebrate assemblage in three tributaries associated to the Paraná River main channel, focusing in Oligochaeta community. We hypothesized that (i) in tributaries, Oligochaeta are richer than the main river (Paraná River) and (ii) dammed tributary (Paranapanema River) is poorly diverse than the others. Samples were conducted in Paranapanema, Baía and Ivinhema tributaries using a modified Petersen grab along three transects (samples conducted inside the tributary, in the mouth of each tributary and inside Paraná River). To analyze (i) the difference between the richness and density among the tributaries and the Paraná River and (ii) effect of each tributary transect on the Oligochaeta richness we used a nonparametric Kruskal-Wallis test. Changes in environmental variables and in richness and composition of Oligochaeta were summarized by Canonic Correspondence Analysis. It was registered 21 different benthic invertebrates taxa, being Oligochaeta assemblage with the highest density. Within Oligochaeta, Narapa bonettoi was the most abundant species, followed by Haplotaxis aedochaeta and Paranadrilus descolei. In our results we refused both hypotheses, because we did not found significant differences for richness and density between the tributaries and the main river, and also no difference between the three transects of each tributary were found. However, the tributaries less influenced by damming, especially the Baía recorded high richness. This corroborates their importance to diversity in the floodplain and the species of Oligochaeta reflect the peculiar characteristics of habitats within each tributaries.

Preferência de Habitat de Oligochaeta (Annelida, Clitellata) em Macrófitas Aquáticas na Represa Ribeirão das Anhumas (Américo Brasiliense-Sp)

As macrófitas possuem complexidades estruturais morfológicas diferentes, oferecendo aos animais a disponibilidade de vários nichos. Esses vegetais também são um importante substrato para o desenvolvimento de perifíton, que possui grande valor nutricional e constitui um dos principais alimentos dos invertebrados aquáticos, principalmente naidídeos. Este estudo teve como objetivo verificar a diversidade da comunidade de Oligochaeta em macrófitas dos gêneros Egeria sp. e Salvinia sp., em lagoas marginais da represa do Ribeirão das Anhumas. Essas macrófitas possuem características tridimensionais distintas e hábitos diferentes, sendo a Egeria submersa fixa e a Salvinia flutuante livre. As coletas das macrófitas foram realizadas entre os meses de agosto de 2012 e abril de 2013. Das amostras vegetais foram tomadas 100 gramas de biomassa (peso úmido) de cada gênero e a remoção das plantas do ambiente foi feita com o auxílio de uma peneira com malha 0,21 mm. Entre as duas macrófitas analisadas, a Egeria sp. foi a que obteve maior diversidade, riqueza e abundância em relação à Salvinia sp. Esses resultados demonstram que as macrófitas aquáticas são importantes para o estabelecimento dos oligoquetos, fornecendo principalmente proteção e alimento, e que possivelmente a morfologia e hábito das plantas são os fatores que mais influenciam na associação da oligogauna com esses vegetais.

Use of oligochaete communities for assessing the quality of sediments in watercourses of the Geneva area (Switzerland) and Artois-Picardie basin (France): proposition of heavy metal toxicity thresholds

The aim of the study was to validate biological tools based on the analysis of sediment-dwelling oligochaete assemblages for assessing the biological quality of sediments in watercourses. The study intended to establish and compare heavy metal toxicity thresholds in streams of two different ecoregions (Geneva area in Switzerland and Artois-Picardie basin in France). The metals Cr, Ni, Cu, Zn, Hg, Pb, Cd, As, Co, Fe and Mn were analyzed. The PEC-Q (Probable Effect Concentration-Quotient) and TEC-Q (Threshold Effect Concentration-Quotient) were used as metal contamination indices. The results showed a significant negative correlation between the oligochaete index of sediment bioindication IOBS and metal contamination indices. Moreover a significant positive correlation between the percentage of Tubificinae without hair setae and metal contamination indices was noticed. Toxicity thresholds of PEC-Q=0.14–0.18 and TEC-Q=0.4–0.6 were established. The toxicity thresholds established in the two different ecoregions were consistent. At some sites, the sediment biological quality evidenced by the oligochaete analysis was poor, yet moderate PEC-Q were observed. The effects of confounding factors such as the bioavailability of metals and the presence of other pollutants (PCBs, PAHs and organic pollution) are discussed. Other conflicting results seemed to be explained by a reduced bioavailability of metals due to organic matter and Mn/Fe oxides.

Spatial distribution of aquatic Oligochaeta in Ilha Grande National Park, Brazil

Ilha Grande National Park is an important conservation unit localized in the Southern part of the upper Parana river floodplain (Brazil) that includes diverse aquatic environments. Oligochaeta (Annelida) is a large group of invertebrates, with several small specimens inhabiting almost every possible niche at most freshwater ecosystem. The goal of the present study was to examine the spatial variation of Oligochaeta community in five floodplain lakes from the Ilha Grande National Park and relate the distribution with abiotic variables. Samples were taken at five sampling stations using a modified Petersen grab. Thirteen species of Oligochaeta belonging to two families Naididae and Tubificidae were recorded. Different patterns of richness and abiotic factors were identified among the lakes located in the island and at the margin of Parana river. The different patterns of granulometric texture affected directly the distribution of the Oligochaeta assemblage of theses environments. The results of this study permit to infer that the Oligochaeta assemblage, in preserved areas, present a higher richness in relation to long term studies with more frequent samplings. We concluded that Ilha Grande National Park contributes for the preservation of benthic invertebrates.

Using real-time PCR and Bayesian analysis to distinguish susceptible tubificid taxa important in the transmission of Myxobolus cerebralis, the cause of salmonid whirling disease

Aquatic oligochaetes have long been appreciated for their value in assessing habitat quality because they are ubiquitous sediment-dwelling filter feeders. Many oligochaete taxa are also important in the transmission of fish diseases. Distinguishing resistant and susceptible taxa is important for managing fish disease, yet challenging in practice. Tubifex tubifex (Oligochaeta: Tubificidae) is the definitive host for the complex life-cycle parasite, Myxobolus cerebralis, the causative agent of salmonid whirling disease. We developed two hydrolysis probe-based qualitative real-time PCR (qPCR) multiplex assays that distinguish among tubificid taxa collected from the Madison River, Montana, USA. The first assay distinguishes T. tubifex from Rhyacodrilus spp.; while the second classifies T. tubifex identified by the first assay into two genetic lineages (I and III). Specificity and sensitivity were optimized for each assay; the two assays showed specificity of 94.3% and 98.6% for the target oligochaetes, respectively. DNA sequencing verified the results. The development of these assays allowed us to more fully describe tubificid community composition (the taxa and their abundance at a site) and estimate the relative abundances of host taxa. To relate tubificid relative abundance to fish disease risk, we determined M. cerebralis infection prevalence in samples identified as T. tubifex using similar molecular techniques. Given prior information (i.e., morphological identification of sexually mature worms), Bayesian analysis inferred that the first qPCR assay improved taxonomic identification. Bayesian inference of the relative abundance of T. tubifex, combined with infection assay results, identified sites with a high prevalence of infected T. tubifex. To our knowledge, this study represents both the first assessment of oligochaete community composition using a qPCR assay based on fluorescent probes and the first use of Bayesian analysis to fully characterize the dominant infected taxa in streams where whirling disease is observed.

Effect of trophic status and sediment particle size on diversity and abundance of aquatic Oligochaeta (Annelida) in neotropical reservoirs

The influence of the sediment grain size and the trophic status of the reservoirs on the composition, richness and biomass of Oligochaeta community was tested. Samples were taken from the littoral and profundal zones of 30 neotropical reservoirs from six different watersheds during two hydrological periods (dry and rainy seasons). The sample units were ordinated, with principal component analyses, according to differences in the sediment grain size, sample depth and dissolved oxygen. The results of a multiple response permutation procedure (MRPP) analysis revealed significant differences in species composition between littoral and profundal zones, trophic status (oligotrophic, mesotrophic and eutrophic) and different watersheds. The environment–species relationship was tested using redundancy analyses. In order to test which environmental variables, either granulometric or limnological, influenced the Oligochaeta community variability we used a partitioning procedure of inertia. Local variations, including reservoir zone and trophic status, were primarily influenced by differences in sediment type and depth. Significant differences in the total biomass between zones, trophic status, watershed and hydrological period were also demonstrated by a Kruskal–Wallis or Mann–Whitney test. The most prevalent taxa were the cosmopolitan tubificids Bothrioneurum sp. and Branchiura sowerbyi , and the naidids Dero (Dero ) digitata and Pristina breviseta , which are dependent on periphyton for food. Higher biomass values were recorded in mesotrophic reservoirs, due to increased nutrient availability and adequate dissolved oxygen supply. Our results indicate that the Oligochaete community structure is directly influenced by local environmental variation in neotropical reservoirs; and that the sediment grain size is the most important factor in determining the Oligochaete community structure.

Spatial and seasonal toxicity in a stormwater management facility: Evidence obtained by adapting an integrated sediment quality assessment approach

Stormwater ponds have been widely used to control increased surface runoff resulting from urbanization, and to enhance runoff quality. As receiving waters, they are impacted by intermittent stormwater pollution while also serving as newly created aquatic habitats, which partly offset changes of aquatic ecosystems and their biodiversity by urbanization. Thus, determining ecological risks in stormwater ponds is important for the preservation and rehabilitation of biodiversity in urban areas. Limitations of the conventional toxicity assessment techniques in stormwater ponds have led us to use the sediment quality triad approach with the specific analyses of oligochaetes. The latter analyses build on the earlier work by the Cemagref (Lyon, France) and use the oligochaetes as bioindicators of the sediment quality. This integrative approach was tested at eight sites in the Terraview–Willowfield stormwater facility in Toronto, Ontario, in all four seasons (summer 2008–spring 2009). The facility receives direct runoff from the MacDonald-Cartier freeway with a traffic intensity of 340,000 vehicles/d. Sediment chemistry results indicate that several heavy metals and PAH compounds exceeded the Ontario sediment quality guidelines in the facility. Regardless of the season, laboratory bioassays revealed a strong spatial variation in sediment toxicity along the flow path from the inlet to the outlet, agreeing with decreasing concentrations of contaminants in sediment, especially of heavy metals. However, in situ assessments of the benthic macroinvertebrate community structure and in particular of the oligochaete community revealed an overriding influence of seasonally varying toxicity. This seasonal pattern was described as high toxicity in spring and recovery in fall and corresponded to the influx and flushing-out of road salts and of several heavy metals within the facility.

Impact of Environmental Conditions on Bottom Oligochaete Communities in Subsidence Ponds (The Silesian Upland, Southern Poland)

AbstractThe aim of the study was to estimate the influence of environmental conditions resulting from coal mining on the diversity of bottom oligochaete communities in subsidence ponds. In the ponds studied 17 oligochaete species representing the families Lumbriculidae (1 species), Enchytraeidae (1 species) and Naididae (15 species), in the new sense (Erséus et al., 2008) were collected. The presence of Aulodrilus japonicus Yamaguchi, 1953 and Potamothrix bavaricus (Oschmann, 1913), rare species in anthropogenic water bodies, is noteworthy. Canonical correspondence analysis (CCA) showed that the important factors influencing oligochaete distribution in the subsidence ponds studied were the type of substratum, the organic matter content of the sediment as well as the mineralization of the water. (© 2011 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Littoral Oligochaeta (Lumbriculidae and Enchytraeidae) communities of some mountain lakes in the Eastern Black Sea Range (Turkey)

Six surveys were carried out during July and August 2005–2007 in order to determine the Oligochaeta fauna of high-altitude lakes located in the Eastern Black Sea Range. With the highest peak, Kaçkar Dagi (elevation 3937 metres), and mountain plateaus at about 3000 metres in elevation, are the highest part of the Eastern Black Sea Range. This range is one of the most important glacial region in Turkey. Some physico-chemical features and Oligochaeta fauna of 39 lakes were determined for the first time, where no previous faunistic studies took place. As a result of the study, a total of 10 taxa was identified, comprising 3 species from Lumbriculidae [(Stylodrilus parvus (Hrabë & Černosvitov, 1927), Stylodrilus heringianus Claparede, 1862, and Lumbriculus variegatus (Müller, 1774)], 7 taxa from Enchytraeidae [(Cognettia sphagnetorum (Vejdovsky, 1878), Cognettia glandulosa (Michaelsen, 1889), Mesenchytraeus armatus (Levinsen, 1884), Mesenchytraeus sp., Henlea ventriculosa (d’Udekem, 1854), Henlea perpusilla Friend, 1911, and Henlea sp.)]. All the taxa represent new records for the region. Stylodrilus heringianus is recorded for the first time in Turkey.

The bottom Oligochaeta communities in sand pits of different trophic status in Upper Silesia (Southern Poland)

Oligochaeta, occurring in the littoral zones of two sand pits, were sampled in order to determine the relationship between the oligochaete species and the waters’ trophic level. Differences between sand pits attributable to community structure and to an overall higher abundance of oligochaetes, especially tubificids, were observed in Dzierzno Male. Multivariate analyses (correspondence analysis [CA] and canonical correspondence analysis [CCA]) reveal correlations between the distribution patterns of oligochaete species and the concentration of nitrates, phosphates and dissolved oxygen. Some species, e.g. Dero digitata, Limnodrilus hoffmeisteri, Potamothrix hammoniensis, Nais simplex, Limnodrilus claparedeanus, Limnodrilus udekemianus and Tubifex tubifex, were more abundant in eutrophic sites. The results of the study showed that the richness of Oligochaeta species is not a good method for estimating the trophic levels of the studied sand pits. Indicators based on the share of oligo-, meso- and eutrophic species in Oligochaeta communities are better for evaluating the water quality in the studied reservoirs.

Oligochaete Assemblages Associated with Macrophytes in the Liangzi Lake District, China

ABSTRACT The assemblage of oligochaetes in the Liangzi Lake District, located in middle reaches of the Changjiang River, was studied from May to August, 2001. To establish species composition, richness, and abundance and detect the influence of environmental variables on oligochaete distributional patterns, 45 localities were sampled. All total, 20 species belonging to the families Naididae (eight species), Tubificidae (11 species), and Lumbriculidae (one species) were found. Branchiura sowerbyi, Tubifex sp. 1, and Aulodrilus pluriseta were the dominant species and contributed nearly 70% of the total abundance. The 45 sampling sites were separated into three groups based on composition and relative abundance of benthic oligochaete communities using two-way indictor species analysis associated with detrended correspondence analysis. Canonical correspondence analysis indicated that two plant variables (total plant cover and total submersed macrophyte biomass) were strongly correlated with the faunal gradient (p<0.05). Other predicator variables were water depth and total nitrogen.

Bottom fauna communities of the Sava River (r-km 61.5-0.5) in Serbia

Samples for analysis of qualitative composition of the bottom fauna were taken from five sampling sites along 61.5 km of the Sava's course in Serbia during the period between 2002 and 2006. In this five-year period, samples were collected under conditions of high and low water levels at five standard localities in the Belgrade region. A total of 106 taxa were recorded, including 31 identified species/taxa of oligochaetes, 28 of chironomids, 11 of gastropods, and 11 of bivalves. The purpose of the investigations was to present the results of qualitative study of the bottom fauna communities with more detailed treatment of the Oligochaeta and Chironomidae communities in the Sava on the territory of Serbia. These groups, together with Nemaloda, Isopoda (two species), and Amphipoda (five taxa), were the most frequent in the bottom fauna. Other faunistic groups were less diverse and showed sporadic distribution. The index of participation of the recorded taxa in bottom fauna communities varies and generally depends on the substrate at the investigated locality. Faunistic similarity between localities was estimated according to calculated values of SORENSEN'S Quotient of Similarity (QS). The majority of recorded benthocenoses showed a medium level of faunistic similarity (QS = 41-60 %).