Chapter 7

The biological monitoring of agreed groups of aquatic and terrestrial fauna and flora is carried out on six complex monitoring areas on the Slovak side. The same groups of fauna and flora, agreed in the frame of joint monitoring, were monitored at 21 monitoring sites on the Hungarian side in 2007 (Fig. 7-1). The list of the complex monitoring areas on the Slovak side and monitoring sites on the Hungarian side is given in Tab. 7-1. From the methodological point of view there are still differences in some monitoring methods on both sides, which should be eliminated after introducing classifications according to the Water Framework Directive during next years. Since 2006 the Hungarian side started to introduce an evaluation according to the Water Framework Directive in case of several groups, however the methodology and results are mentioned in the National and Joint Report marginally.

No.

Name

Locality

M o n i t o r e d g r o u p s

Macrozoobent.

Zoopl.

Slovak side – complex monitoring areas

B-6

2600

Dobrohošť – Dunajské kriviny

●

B-9

2603

Bodíky – Bodícka brána

●

B-10

2604

Bodíky – Kráľovská lúka

●

B-14

2608

Gabčíkovo – Istragov

●

B-15

2609

Sap – Erčéd

●

B-18

2612

Kľúčovec – Sporná sihoť

●

Hungarian side – monitoring sites

28a

B-01

Dunasziget – forest

●

28b

B-02

Dunasziget – meadow

●

B-03

Halászi – forest Derék

●

B-04

Lipót – Gombócos closure

●

H-04

Dunasziget – Schisler arm

●

H-05

Zátonyi Danube

●

5, 6

H-06

Lipót – Lipóti marsh

●

H-07

Danube, rkm 1828

●

H-08

Zátonyi Danube

●

H-09

Dunasziget – Csákányi Danube

●

H-10

Danube, rkm 1833

●

2, 11

H-11

Danube, rkm 1839

●

F-31

Zátonyi Danube, Gázfűi Danube, rkm 28,5

●

F-04

Mosonmagyaróvár – riverine forest

F-26

Kisbodak – Pálfi island, forest

●

F-27

Rajka – forest Felső

●

F-28

Novákpuszta – Nováki channel

●

F-22

Lipót – Zsejkei channel

●

F-33

Danube, rkm 1849

F-34

Lipót – river arm

F-35

Mosonmagyaróvár – Mosoni Danube

●

F-17

Arak – Nagy Kerek

●

F-19

Danube, rkm 1824

●

F-N3

Arak, Nováki channel

●

● – data provided x – no data provided, mentioned in connection with WFD only

F - Dragonflies (Odonata – aquatic larvae on the Slovak side + flying imagines as supplement, flying imagines on the Hungarian side)

G - Mayflies (Ephemeroptera - aquatic larvae on the Slovak side + flying imagines as supplement, flying imagines on the Hungarian side)

H - Caddisflies (Trichoptera - aquatic larvae on the Slovak side + flying imagines as supplement, flying imagines on the Hungarian side)

A short description of climatic and hydrological conditions in the year 2007, which influenced the development of observed groups of fauna and flora on both sides of the Danube, is given above in Part 6.

7.1. Phytocoenology

In the evaluated year the phytocoenoses in the inundation area were very considerable influenced by the summer drought and flood absence during the vegetation period. Another determining factor was the cutting off the tree layer at monitoring areas No. 2608 and 2609. On these areas rapid growing of the plant layer was observed. On both areas invasive or neophyte species dominate, but the presence of original hygrophilous species remains. The phytocoenoses on areas No. 2600, 2603, 2604 and 2612 are stabilised, although during the dry summer decrease of plant layer coverage was recorded. Unsettling is the high portion of invasive species on the area No. 2604, which was characterised by typical lowland forest vegetation so far.

The average species diversity of phytocoenoses of observed areas have not changed significantly in comparison wit previous years. The general slight coverage increase of the plant layer is attributed to the weed species Galium aparine. Due to the absence of flood several plant species produced extraordinarily high amount of biomass. On the other side, retreat of invasive species and nettle (Urtica dioica) continued in poplar stands at Lipót, which was attributed to occurrence of flood in the previous year.

Similarly to the previous year the average leaf area values for pedunculate oak (Quercus robur) at Dunasziget reached average values. The average leaf area on white willow (Salix alba) and alder (Alnus glutinosa) stands remained unchanged in comparison with the previous years. The structure of phytocoenoses along the Mosoni Danube, where the water level is stabilized, remained unchanged as well. On most observed areas damages caused by forest game (biting) were registered.

7.2. Terrestrial molluscs

The terrestrial mollusc’s community on a large part of inundation area is stabilized, observed changes in most cases could be assigned to the impact of the silviculture or actual hydro-meteorological conditions. Clearing of forest stands mostly influences monitoring areas No. 2608 and 2609 at present. On both areas gradual decrease of hygrophilous and poly-hygrophilous species and increase of eurytopic species was registered. In addition the water supply would be necessary to solve in the region around the monitoring area No. 2608, which could contribute to regeneration of communities of surviving poly-hygrophilous species. The least changes were registered at monitoring area No. 2612, which is occupied by a malakocoenoses typical for drier softwood forest.

The terrestrial malakofauna in the inundation and in the flood-protected area is rich in species and stabilised. Although in individual years fluctuation can be registered, no worsening tendency can be observed. In last two years many species (including hygrophilous species) occur in amount of several hundreds of individuals. The young forest in the strip on the bank of the Danube (at rkm 1824) is occupied by very varied malakocoenoses, which can play an important role in regeneration of other low-in-species places, where species can be spread during floods.

7.3. Aquatic macrophytes

In the Danube old riverbed two Hungarian monitoring sites are situated (No. 2 and 7). The monitoring area No. 2 is situated in the main riverbed downstream of the bottom weir, in the bay at a guiding structure. Banks and the guiding structure are already overgrown by almond-leaved willow shrubs (Salicetum triandrae); macrophytes were not registered. More interesting macrophyte vegetation is observed on the monitoring area No. 7, which is separated from the Danube old riverbed by shoreline vegetation of Salicetum triandrae and Scirpo-Phragmitetum. In this isolated part with stagnant water area macrophyte community rich in species occur.

The development of macrophyte vegetation in evaluated year was determined by two main factors – the low surface water levels and low amount of precipitation. Higher flow rates were registered only at monitoring area No. 2603, which is situated in the main arm of the water supply. Although there were valuable and invasive species present in the species spectrum, the macrophyte growth was poor. The macrophyte community in the dead arm on monitoring area No. 2604 was relatively stable in last years, however due to early uncoveraging of littoral in the summer spreading of marshy species was observed. Destruction of the true water vegetation in the summer was recorded on monitoring areas No. 2608 and 2612 as well. In the river arm on area No. 2608 ruderal species appeared coming from neighbouring cleared areas. On the area No. 2612 high species diversity was recorded, but mainly due to the presence of marshy species.

The discharges supplied into the active floodplain were similar to discharges in previous years. Large parts of the floodplain river branches are characteristic by higher water depth. The water flow on monitoring site No. 4 is very slight and the water level is covered by fibrous green algae and submersible macrophytes. The water on monitoring site No. 9 flows moderately; large flecks of submersible macrophytes were registered, including the invasive species Elodea canadensis.

The hydrological conditions of the flood-protected area (monitoring sites No. 6 and 8), thanks to the continuous water supply, remained unchanged in last few years. The species composition in the evaluated year was richer, although the number of protected species was slightly lower. Occurrence of the invasive species Elodea canadensis increased on the monitoring site No. 6, on the site No. 8 it was not registered.

7.4. Aquatic molluscs

The evaluation of the aquatic molluscs’ community in the Danube is based on the data provided by the Slovak Party (Slovak observation areas No. 2600, 2608 and 2612); the Hungarian Party did not provided data for the Danube in the frame of the Joint monitoring for the evaluated year. Similarly to previous years the results of the Slovak Party demonstrate significant decrease in the species diversity and species abundance as well. The malakofauna is composed almost entirely by ubiquistic and invasive species. The reason of retreat of the original species is not clear so far.

The aquatic molluscs’ community in the river branch system on the Slovak side is monitored at sites No. 2603 and 2604. Relatively rich malakocoenoses was recorded on the monitoring site No. 2603, which is situated in the main arm of the water supply. Semi-rheophile and limnophile species dominated. The situation in dead arm on monitoring area no. 2604 was less favourable. The malakofauna was poor, abundant occurrence of one ubiquistic species was an exemption, however more favourable situation can be expected after the autumn flooding.

The malakofauna variedness of the water bodies in the flood-protected area exceeds the variability of drier forest communities, but it does not reach the variety registered in the inundation area. Fluctuation of results depends on actual site-specific conditions. The malakocoenose of the branch in the inundation area (Pálfi island) was rich in species and abundant.

7.5. Dragonflies (Odonata)

The general situation of odonatocoenoses in the river branch system was more favourable in comparison with previous years. Although on several monitoring areas only flying imagines were registered (areas No. 2600 and 2608), they proved their settling in the neighbourhood area. Richer odonatocoenoses were registered in the through-flowing river arm on the monitoring area No. 2603, where the increase of limnophilous species indicate the return to the state before damming the Danube. Shallowing and overheating of the dead arm had negative influence on the rich dragonflies community of the monitoring area No. 2604. This could be mitigated or eliminated by artificial flooding of this area. High species richness on the monitoring area No. 2612 represents three different types of neighbouring biotopes – the Danube, sporadically through-flowing river arm and periodic depressions.

The dragonflies’ community monitoring in 2007 did not proved significant, tendentious changes. As the most rich in species site in the Szigetköz region the Nováki channel at Arak village is considered, with slowly flowing water and abundant aquatic vegetation.

7.6. Crustaceans (Cladocera, Copepoda)

Evaluation of the development of Cladoceras and Copepods communities is based on the results of the Slovak Party at monitoring site No. 2600 and 2608. Both communities were poor along the whole observed section of the Danube, especially in autumn, when they were flushed out by high flow rates. In most of the samples unusual dominance of tychoplanktonic species was observed. The explanation of this phenomenon is not clear so far.

Actual development of Cladocera and Copepod communities on the monitoring area No. 2603 is significantly influenced by growing of littoral macro-vegetation after cutting off the riparian forest stand, on the monitoring areas No. 2604, 2608 and 2612 by interruption of shallowing and overgrowing of river branches due to occurrence of higher discharges on the Danube during last years. As a consequence of these influences dominance of tychoplanktonic Cladocera and Copepoda species was observed on the monitoring area No. 2603 in last two years; on the monitoring areas No. 2604, 2608 and 2612 both communities rich in species were recorded, where the euplanktonic species mostly dominate.

There were recorded 21 Cladocera species and 10 Copepoda species in observed river arms in the evaluated year. New species was not detected, but repeated presence of several species was proved, which were missing in samples for several years. On the other side several species, which were permanently present, were not recorded in 2007.

The species richness of the Cladocera and Copepod communities was significantly lower in the Schisler dead arm in comparison with the high value recorded in the last year. Similarly to the previous year the proportion of phytophilous species was low, which is related to the interconnection of the dead arm with the Csákányi river arm artificially created in 1998. The euplanktonic species dominated in the dead arm.

In the Csákányi Danube 6 species were recorded again (5 Cladoceras and 1 Copepod). Their abundance was very low, several species had irregular occurrence in individual samples. The weak inhabitancy of the river arm can be connected to stronger flow of water because the river arm form a part of the water supply system in the inundation area.

At monitoring site in the Zátonyi Danube, situated in the flood-protected area, 14 species of Cladocera and Copepoda were registered in the evaluated year, similarly as in 2006. The species composition was similar to the composition in the previous year and it can be stated again that it indicates the diversity and stability of habitats in the Zátonyi Danube.

The species diversity of Cladocera and Copepod communities was repeatedly low in the Lipóti marsh. Similarly to the previous year species number decrease was registered, although the highest abundance was recorded from among the observed river arms. The most abundant were phytophilous species of stagnant water bodies. Several rare species were not registered, probably due to exploitation of the marsh lake for fishing.

7.7. Caddisflies and Mayflies (Trichoptera, Ephemeroptera)

No caddisflies and mayflies observation results from the Hungarian side were available in the evaluated year. The summarizing list of species of benthic invertebrates recorded during the period of observation according to the Water Framework Directive, which is a part of the Hungarian National Report on environmental monitoring in 2007, contains every species recorded on 4 sampling profiles without their abundance. Based on this table was not possible to conduct conclusions on development of these taxocoenoses in the evaluated year. So far there do not exist definitive classification schemes for evaluation of macrozoobenthos groups. Generally the presence of relatively rich caddisfly and mayfly communities in the Szigetköz region can be stated. However, the results of the Slovak Party given below show significant impoverishment, even absence of these communities in the Danube and in the whole area on Slovak side.

The Danube, according to the results of the Slovak Party (monitoring areas No. 2600, 2603, 2608 and 2612), is inhabited by caddisflies and mayflies sporadically. Mayflies were recorded only in the upper section of the Danube old riverbed and below the confluence with the tailrace channel. Caddisflies in the Danube were registered irregularly represented by semi-rheophile and rheophile species. Surviving of further rheophilous caddisfly and mayfly species under changed conditions in the Danube old riverbed was proved by results obtained after sampling the hard-to-get medial sections during low flow rates period in autumn.

Every observed river branches in the left side inundation area (monitoring sites No. 2603, 2604 and 2612) are very poor from the point of mayfly and caddisfly communities. Only one limnophilous mayfly species had stable occurrence in samples. Caddisflies were represented by irregular occurrence of semi-rheophilous or limnophilous species.

7.8. Fish (Osteichtyes)

The ichtyofauna monitoring on both sides is carried out by electro-fishing. Difference exists in the power-output of the apparatus, which decreases the comparability of results obtained by both Parties.

The evaluation is based on Slovak observation results at monitoring areas No. 2600 and 2608, and Hungarian observation results at monitoring sides No. 10 and 11. Samples taken in the year 2007 prove the retreat of rheophilous species; the ichtyocoenoses of this Danube section is created by eurytopic and littoral species. Spreading of foreign species is unambiguous, but not intensive. The results of the Hungarian Party show significant species richness in the Danube.

On the monitoring areas No. 2603 and 2604 stable, rich in species ichtyocoenoses occur. On both monitoring areas increased abundance of ichtyofauna was recorded in the evaluated year: in the river branch on area No. 2603 due to high amount of juvenile individuals, in the dead arm on area No. 2604 due to excessive breeding of one expansive foreign species. Ichtyocoenoses on both partial sites at monitoring area No. 2608 were rich in species and abundant in the evaluated year. This state on the sub-area above the Foki weir is usual due to regular connection with the Danube, but the situation on the sub-area below the Foki weir prove restoration of the connection with the Danube during high discharges in last few years. The ichtyocoenoses on monitoring area No. 2612 was composed mainly by eurytopic and limnophilous species, which settled the river arm after its drying out in 2004.

The ichtyofauna on the Hungarian side is monitored at two monitoring sites in the inundation area (No. 4 and 9) and at two monitoring sites in the flood protected area (No. 5 and 12).

The ichtyofauna of the Schisler river arm (monitoring site No. 4) was restored and enriched after its artificial reconnection with Csákányi Danube in 1997. At present there is rich in species and stabilised ichtyofauna. In parts overgrown by macrophytes phytophilous and limnophilous species occur, but in the channel interconnecting the dead arm and Csákányi Danube seasonal occurrence of rheophilous fish species were observed.

The ichtyofauna species diversity in Csákányi Danube (monitoring site No. 9) is high since introduction the water supply in 1995; however, there were fluctuations in some periods (e.g. 2000-2003), which were not clearly clarified. There were 17 species recorded in the evaluated year, along with very high abundance of one tolerant species.

After introducing the water supply (in 1995), regeneration of ichtyofauna is observed at monitoring site No. 5 – Lipóti marsh. The species richness of this site is significant and balanced in last years. In the evaluated year benthic litophilous species dominated.

The ichtyocoenoses in the Gazfűi Danube (monitoring site No. 12) is stabilized as well since introducing the water supply to the flood-protected area. Moderately rich species diversity is composed by marshy and phytophilous species, although eurytopic fish species remained dominant.

PART 7

Biological Monitoring