Aquatic Macrophytes of the Danube River near Novi Sad (Yugoslavia, river km 1255 - 1260)
Janauer, G. A.1, Vukov, D.2, Igic, R.2
With 3 figures and 2 tables in the text
Abstract: This study deals with a preliminary investigation of the aquatic vegetation of
the Danube system at Novi Sad (Yugoslavia). The macrophyte survey in the main
channel of the river and in one small oxbow was performed in 1998. Species richness in
this reach of the main channel was intermediate with respect to parts of the river in other
countries. The plant mass was very low and very small plant stands were developed. The
oxbow is directly connected to the main channel at its lower end, but a considerably
higher number of species was present than in the main channel. Again, only very small
stands with low biomass were found. This indicates that there are many small niches in
the near-bank habitats, but the hydrological dynamics prevent the development of larger
vegetation patches.
1 Institute of Ecology and Conservation Biology, University of Vienna, Althanstraβe 14, A-1090 Vienna, Austria. e-mail: [email protected] 2 Institute of Biology and Ecology, Faculty of Natural Science, University in Novi Sad, Trg Dositeja Obradovica 2, 21000 Novi Sad, Yugoslavia. e-mail: [email protected]
Introduction
The Danube is the second largest river in Europe. Its length is 2850 km and it flows through ten countries (Germany, Austria, Slovakia, Hungary, Croatia, Yugoslavia,
Romania, Bulgaria, Moldavia and Ukraine). This makes it the most important navigational artery of Central and South-Eastern Europe. Its catchment covers an area of
805000 km2, and includes seven more countries (Switzerland, Italy, Czech Republic,
Poland, Bosnia and Herzegovina and Albania). In Germany, the Brigach and Breg
headstreams create the Danube. Most of the water originates from the Alpine tributaries
Isar, Inn, Traun and Enns. Other main tributaries are: Drava, Sava, Tisa, Velika Morava,
Siret and Prut. In Romania, the Danube empties into the Black Sea. According to its length, and size of its catchment, the Danube is a system of high structural diversity.
Numerous tributaries of variable size, different types of active and relict back waters in flood plains, and morphologically different reaches of the main channel offer various
types of habitats to different aquatic macrophyte species.
In Yugoslavia the Danube flows for 588 km, and exhibits different geo-morphological
structures along its banks. According to its gradient and discharge regime the Danube in
Yugoslavia is a low-land river, and due to the foothills of mountain ridges the upland on
the right bank is higher than the one on the left (MILOJEVIC, 1960). Severe changes in hydrological regime occurred near Novi Sad in 1999. All bridges in the town were destroyed due to military actions and their broken structures became an obstacle for the flow of the river. Obtained data present the base for further monitoring and tracking of future changes. The study site is placed upstream of Novi Sad, where the main channel of the Danube River, between km 1255 and 1260, and the Ribarsko Ostrvo side arm at km
1258, on the left side, were studied. Forests and semi-natural areas line the right river
bank, and embankments are present on the left and adjacent to it artificial surfaces exist.
Concrete is the bank material used between km 1255 and 1260, but forest patches and
semi-natural areas are situated close to the river. Therefore this part is intensively used for recreation (km 1255-1258). The bed sediment consists of sandy material. At the end of the Ribarsko Ostrvo side arm a shipyard is located, which features concrete embankments and sandy sediment. The side arm is of urban character on the left side, featuring a marina and a nautical club, while on the right side sandy sediment is found and a flood plain forest covers the adjacent land. As the outlet of the Novi Sad sewage treatment plant is located downstream of the study site it is of no influence to the results of this survey.
Material and methods
The macrophyte survey was performed during the summer of 1999. Plant species were
determined after FELFÖLDY (1990), and nomenclature follows TUTIN et al. (1964-1980).
Collected plant material was conserved in 4% formaldehyde as a reference. All other information on the survey method is found in the respective chapter in this volume (see also KOHLER, 1978, KOHLER & JANAUER, 1995, PALL & JANAUER, 1995, JANAUER et al.
1993).
Results In the main channel 12 tracheophytes and 1 moss species occurred (Species list, Tab.1).
All of them except the moss Fontinalis antipyretica, which occurred in one survey stretch only, are associated with moderate to low current velocities (HASLAM 1978). In the oxbow a higher number of species was detected (17 phanerogams, 1 moss species). In comparison with other stretches of the Danube (Table 2) fewer species were found in the
Novi Sad reach than in Hungary, (15) and Slovakia, (17) in the Old Danube, which is the
relict of the river created after the construction of the Gabcikovo hydro-electric power
plant. In retainments of hydro-electric power plants sometimes more (Germany: 21
vascular species) sometimes fewer species (Austria: 4 vascular species) have been
reported (see respective chapters in this volume). The reach in Novi Sad is of
intermediate species richness.
The Distribution Diagram (Figure 1) shows how little plant mass is present in this stretch of the Danube. Although the niches in the littoral support the growth of many aquatic species no large stands are developed. This is the case even in the oxbow. The RPM
diagram (Figure 2) indicates that pleustophytes (LUTHER 1949) are dominant in the
littoral near the banks of the main river, as well as in the oxbow. Regarding the Mean
Mass Index diagram (Fig. 3) all values are extremely low. The Mean Mass Index of
Occurrence (MMO, white bar) is rarely close to the descriptor level 2, and most species
hardly reach over a level of 1.
Discussion
In the main channel of the Danube near Novi Sad the species richness of the aquatic vegetation is at a medium level as compared to other reaches in the river. Yet, little plant mass is developed in the near-bank littoral. Some species are ubiquitous, but their plant mass is also minimal.
The oxbow, which is open to the main channel of the river at its lower end, is rather
short. As the gradient of the river is also low (0,06%o, LASLÓFFY 1967) even small fluctuations in river discharge result in changing currents and water levels in the oxbow.
Regarding these conditions it is a surprise to find the high number of 18 aquatic species,
among them 17 phanerogams.
When considering trophic indication of the macrophytes found near Novi Sad almost the
whole set of species is well adapted to higher nutrient loads. The water quality is
considered β- to α- meso-saprobic near Novi Sad (HEUSS, 1996) and nutrients should be
well above any limiting level for species that indicate eutrophic conditions. This may
contrast with side channels of smaller size, and flood plain water bodies with lower
connectivity with the main river channel, and future studies here would be expected to
show very different aquatic vegetation communities.
In the Distribution Diagram the lack of development of larger plant stands is apparent.
This is true not only for the main channel, but also for the oxbow. Although the niches in the littoral near the banks support the growth of many aquatic species, none developed a
high plant mass. The oxbow is a typical remnant of the regulation of the river. Despite the
frequent water level changes species usually found in lentic sections, like Wolffia arrhiza,
are present, but niches where they can survive are small.
The Relative Plant Mass, which is weighted by the length of the survey units and
therefore is preferable to frequency as a metric for dominance, indicates that Lemnids
(five species at the top positions in the RPM-diagram. Fig. 2) dominate the aquatic
vegetation. Although the plant stands were small there are enough niches in the littoral
near the banks of the main river, as well as in the oxbow, in which non-rooted plants can
survive. Salvinia natans occurred in two survey units in the main channel and even
Ceratophyllum demersum, a species of much larger size, was present in most of the stretches. All other species occurred to a much smaller extent.
The Mean Mass Index describes the distribution pattern of species. The white bar (MMO,
Mean Mass Index of Occurrence) indicates the average mass of a species in the survey units where it occurs. The black bar (MMT, Mean Mass Index calculated over all survey units) indicates the average mass of a species in all the stretch of river surveyed. In the case of the Novi Sad reach of the Danube all values are extremely low. The MMO (white bar) is rarely close to the descriptor level 2, and most species hardly reach over a level of
1. This equates to “rare” to “very rare”. In many cases the MMT (black bar) is of rather
similar size, which is true for all species with a “d”-value higher than 0.5. About six
species out of 14 show this type of distribution. They are more or less evenly distributed over all survey units. All species with a low “d” are only occurring in one or a few survey
units. They may be unstable with regard to season and/or successive years.
The overall picture of the reach near Novi Sad and the adjacent oxbow is that of an aquatic environment supporting an intermediate number of macrophyte species when compared to other reaches of the main channel of the river. However, there is no development of larger plant mass and further investigations may reveal the possible reasons for this unexpected situation.
Acknowledgements
The authors thank Karin Pall for the preparation of the Standard Graphs. They also thank
the Austrian National Committee of the International Association for Danube Research
(ÖN-IAD) for funding a substantial part of this study. References
FELFÖLDY, L. (1990): Hinar határzó. Vízügy hidrobiológija, 18. kötet, Környezetvédelmi
és terület fejlesztési Minisztérium, Budapest.
HASLAM, S.M. (1978): River Plants. Cambrindge University Press. 396 pp.
JANAUER, G. A., ZOUFAL, R., CHRISTOF-DIRRY, P. & ENGLMAIER, P. (1993): Neue
Aspekte der Charakteridierung und vergleichenden Beurteilung der
Gewasservegetation. Ber. Inst. Landschafts - Pflanzenökologie, Univ.
Hohenheim, 2: 59 - 70.
KOHLER, A. (1978): Methoden der Kartierung von Flora und Vegetation von
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KOHLER, A. & JANAUER, G. A. (1995): Zur Methodik der Untersushung von aquatischen
Makrophyten in Flieβgewässern. In Steinberg, Ch., Bernhardt, H., Klapper, H.
(eds.): Hanbuch Angewandte Limnologie, VIII-1.1.3, p. 1-22, Ecomed Verlag,
Landsberg/Lech.
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LIEPOLT, R. (Ed.): Limnologie der Donau. Stuttgart. 591 pp.
LUTHER, H. (1949): Vorschlag zu einer ökologischen Grundeinteilung der Hydrophyten.
Acta Bot. Fenn. 44: 1 - 15.
MILOJEVIC, B. (1960): Panonski Dunav na teritoriji Jugoslavije. Zbornik Matice Srpske
za prirodne nauke, 18: 5 - 65.
PALL, K. & JANAUER, G. A. (1995): Die Makrophytenvegetation von Fluβstauen am
Beispiel der Donau zwischen Fluβ-km 2552.0 und 2511.8 in der Bundesrepublik
Deutschland. Arch. Hydrobiol. Suppl, 101 (Large Rivers, 9): 91-109. RATH, B. (1997). Verbreitung von aquatischen Makrophytenbeständen im Flußbett des
früheren Hauptarmes der Donau (Szigetköz, Str.-km 1826 – 1843). 32.Konferenz
IAD, Wien/Österreich. Limnol.Ber.Donau 1997, Bd.I, Wiss.Referate: 227 – 232.
TUTIN, T. G., HEYWOOD, V. H., BURGES, N. A., MOORE, D. M., VALENTINE, D. H.,
WALTERS, S. M., WEBB, D. H. (1968 - 1980): Flora Europaea (II - V). Cambridge
University Press, Cambridge.
TUTIN, T. G., HEYWOOD, V. H., BURGES, N. A., VALENTINE, D. H., WALTERS, S. M.,
WEBB, D. H. (1964): Flora Europaea (I). Cambridge University Press, Cambridge.
Figure captions:
Figure 1: Novi Sad Area (Yugoslavia) - Distribution Diagram
Danube - Main Channel: Wide columns; Oxbow: narrow columns
The width of the columns is equivalent to the real length of the survey units.
Horizontal bars indicate the plant mass estimate (PME) for each species in each
survey unit. Small bar: estimate levels 1 and 2. Medium bar: estimate level 3.
Large bar: estimate levels 4 and 5.
Figure 2: Novi Sad Area (Yugoslavia) - Relative Plant Mass (RPM)
Danube - Main Channel: upper diagram; Oxbow: lower diagram
Figure 3: Novi Sad Area (Yugoslavia) - Mean Mass Indices (MMO/MMT) and
Distribution Ratio (d)
Danube - Main Channel: upper diagram; Oxbow: lower diagram
White bar: Mean Mass Index, calculated on the basis of survey units of
occurrence of a species (MMO). Black bar: Mean Mass Index, calculated on the
basis of all survey units (MMT). Distribution ratio (d): Ratio between MMO and
MMT. It is of special importance when comparing very low numerical values (=
very small bars) of MMO and MMT. Detailed explanation in the “Methods”
chapter in this volume. Tables:
Table 1: Species list
The names of authors follow TUTIN et al. (1964;1968-1980) and FELFÖLDY (1990). Species Abbrevation Occurance Growth form Main Channel Side Arm Fontinalis antipyretica L. Fon ant Bp
Alisma plantago-aquatica L. Ali pla A Carex pseudocyperus L. Car pse Ceratophyllum demersum L. Cer dem Bp Iris pseudacorus L. Iri pse A Juncus compressus Jacq. Jun com H Lemna gibba L. Lem gib Ap Lemna minor L. Lem min Ap Lemna trisulca L. Lem tri Mp Mentha aquatica L. Men aqu A Myriophyllum verticillatum L. Myr ver R Najas minor All. Naj min R Phragmites australis (Cav.) Trin. Phr aus H Polygonum amphibium L. Pol amp A Potamogeton crispus L. Pot cri R Potamogeton pectinatus L. Pot pec R Salvinia natans (L.) All. Sal nat Ap Spirodela polyrhiza (L.) Sch. Spi pol Ap Wolfia arrhiza (L.) Horkel Wol arr Ap
Table 2: Number of species in different water bodies in the fluvial corridor of the Danube river
Water body Number of Reference species*
Impoundment Höchstädt, Germany 21 PALL & JANAUER (2002)**
Impoundment Abwinden – Asten, Austria 4* JANAUER & PALL (2002)
Main river channel, Old Danube, left bank, 17 OTAHEĽOVÁ & VALACHOVIC Slovakia (2002)
Danube river, Old Danube, right bank, 15 RATH (1997) Hungary
Danube river, Novi Sad, Yugoslavia 12* JANAUER ET AL. (this study)
Oxbow, Novi Sad, Yugoslavia 17 JANAUER ET AL. (this study) * Total number of species in all respective stretches [excluding algae and mosses, which were not surveyed in all studies used for this comparison] ** all citations 2002 refer to this volume
Fig. 1
Cer dem Fon ant Lem gib Lem min Lem tri Men aqu Myr ver Naj min Pol amp Pot cri Pot pec Sal nat Spi pol Wol arr Ali pla Car pse Iri pse Jun com Phr aus Fig. 2
20
% ( 10
RPM
0 r r p n n b e r i i m v a pol gi nat l r i dual pec l m m i j t dem a p a l r s on ant o en aqu S e S e Wo My Na F P r Lem Po C Lem M
90
80
70
60
50 % (
RPM 40
30
20
10
0 e e a l m
s s o p aus p i li p r r Ir
h A un c Ca P J
Fig. 3
Cer dem
Fon ant
Lem gib
Lem min
Lem tri
Men aqu
Myr ver
Naj min
Pol amp
Pot cri
Pot pec
Sal nat
Spi pol
Wol arr 12 3 4 5 00,51 MMT, MMO d
Ali pla
Car pse
Iri pse
Jun com
Phr aus
12 3 4 5 00,51 MMT, MMO d