Oligochaeta community of the main Serbian waterways

Ana Atanacković¹, Dunja Jakovčev-Todorović¹, Vladica Simić², Bojana Tubić¹, Božica Vasiljević¹, Zoran Gačić³ and Momir Paunović¹

¹ University of Belgrade, Institute for Biological Research “Sinisa Stankovic”, Despota Stefana 142, 11000 Belgrade, Serbia; e-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it
² University of Kragujevac, Institute of Biology and Ecology, Faculty of Science, Radoja Domanovica 12, 3400 Kragujevac, Serbia
³ Institute for Multidisciplinary Research, Kneza Viseslava 1, 11030 Belgrade, Serbia

Abstract

The aim of this paper is to present a checklist and the distribution of Oligochaeta in Serbia’s major rivers: the Danube, the Sava, and the Tisa. The data presented serve as principal inputs for the design of an effective biomonitoring system, as a part of routine monitoring of water status under the EU Water Framework Directive. The rivers under investigation flow through numerous industrial and urban centers and receive significant amounts of pollution. The effects of pollution and hydromorphological alterations are important for the distribution of Oligochaeta, which are one of the principal members of the macroinvertebrate community. A total of 52 taxa of aquatic worms from 32 genera, belonging to 9 families, have been recorded. Most of the observed species are typical of potamon-type rivers in the region, adapted to high and moderate organic loads. The recorded community is dominated by limnophylous and limno to rheophilous, as well as pelophylous, argillophylous and psammophylous taxa. Although the investigated river stretches are considered to be of similar water types, characterized as large lowland rivers, a certain differences within the Oligochaeta species composition has been identified.

Key words: Oligochaeta, biological quality elements, water status, watercourses, large rivers,

Introduction

This paper provides a list of recorded taxa and discusses the distribution of Oligochaeta (aquatic worms, oligochaetes) species in three large rivers in Serbia: the Danube, the Sava, and the Tisa. The results are especially interesting because aquatic worms were found to be among the principal members of the macroinvertebrate community in the investigated rivers (Paunovic, 2004; Paunovic et al., 2008; Paunovic et al., 2007). The community in the investigated rivers, which are similar with regard to their overall characteristics (SCG ICPDR, 2004), is highly complex. Data on the Oligochaeta community in substantial stretches of large rivers in the region are scarce, generally limited to descriptions of relatively small reaches (Paunovic, 2004).
The results presented below constitute an important input for the design of an effective approach to ecological status assessment. After the EU Water Framework Directive (European Commission, 2000) came into the force, biological investigations of aquatic ecosystems became an important component of water management. According to the EU Water Framework Directive (WFD), biological status assessment is primarily based on analyses of aquatic communities – Biological Quality Elements (BQEs). In particular, BQEs including aquatic macroinvertebrates, and oligochaetes as their principal member, were underscored as the most important element for water status assessment. Thus, the aim of this paper is to present the data needed to contribute to the knowledge of the aquatic worm community and its potential use in ecological status assessment.
The Danube River Basin is the second largest river basin in Europe, with a surface area of some 800,000 km². The basin extends into 17 countries. The total length of the Danube River is 2,857 km.
The Serbian stretch of the Danube is 588 km long and includes the middle and a part of its lower, 220 km long, course. A major portion of this stretch of the Danube (358 km) lies within the Pannonian Basin. In Serbia, the Danube is a typical lowland river, with a gradient of 0.05-0.04‰. The largest tributaries of the Danube in Serbia are the Tisa and Sava rivers. The Danube River Basin is considered to be a “hot spot” for European freshwater biodiversity, due to its geographical location, extent and history (Sommerwerk et al., 2009).

The catchment area of the Tisa River (157,186 km²) is the largest sub-basin of the Danube River Basin. The Tisa is the longest tributary (966 km) of the Danube; it comes from Hungary and empties into the Danube in Serbia, near Slankamen (at km 1215). Only 5% of its catchment area lies within the territory of Serbia, and this 164 km long stretch of the Tisa is a typical lowland river (Lower Tisa). In Serbia, the Tisa receives the Begej River directly and a number of smaller tributaries indirectly, via the Danube-Tisa-Danube Canal System (HS DTD). The main structure of the HS DTD is a dam erected at the 63rd km of the Tisa River. The dam has increased low and average water levels, whose effects are felt beyond the Serbian/Hungarian border.
The Sava River rises from the Sava Dolinka and the Sava Bohinjka in Slovenia. With numerous tributaries along its 940km-long course to the Danube, it represents one of the most significant basins in the region (surface area 95,419 km²). The lower course of the Sava (206 km long) flows through Serbia. This stretch is a typical lowland watercourse: it is located at an altitude of less than 80 m , its gradient is 0.098 ‰, the river channel is up to 1000 m wide, and there are relatively thick deposits dominated by small fractions of sand and silt. The long-term average water discharge at Sremska Mitrovica (about 100 km upstream from the mouth) is nearly 1500 m³ s-1. The Sava River joins the Danube at Belgrade (km 1170).
The Danube, the Sava and the Tisa are important waterways, not only for Serbia, but also for other countries in the region. Besides intensive ship traffic, the rivers are under the influence of hydromorphological alterations, settlements, industrial “hot-spots”, and agriculture (for details see: Csanyi, 2002; ICPDR WFD Roof Report, 2004; Literathy et al., 2002; Paunovic, 2004; SCG ICPDR, 2004).
One of the most important problems which affect the Danube is river engineering. In Serbia, the erection of a dam on the Danube near Sip (km 943), has resulted in the creation of a large artificial lake, the Iron Gate Reservoir, which is 100 km long and extends to Golubac. Following damming, the flow rate of the Danube decreased upstream all the way to Slankamen (km 1215), and resulted in intensified sedimentation.
The investigated rivers are affected by urban wastewater originating from numerous settlements, as well as wastewater from industrial facilities and agricultural activities. Radioactive contamination has been detected in sediments sampled from the Sava River (Ajdacic and Martic, 1989) and in groundwater (Jankovic, 1989).