CONCLUSIONS The bibliography of zoological publications from the region of the Danubian lowland elaborated by Kalivodova et al. [17] contains 1,979 items of zoological research published until 1985 by 729 domestic and foreign authors. Publications are dealing with 1,473 taxons (from level of species up to races), of which they are 716 taxons of evertebrates and 757 taxons of vertebrates. Publications contain faunistic and ecological data about numerous animal species in the period of existence of their nearly original inundation biotopes. There is a possibility to compare the present state with the state in the past. Based on the analysis of the state in the period of original biotopes it is possible to study direction and progress of changes of natural environment and changes in zoocoenoses in new, changed natural conditions. For the purposes of biota monitoring plots were established. They represent all types of hydrological changes. Based on observation of taxacoenoses of Mollusca, Chilopoda, Aranea, Acari, Colembola, Heteroptera, Lepidoptera and Coleoptera the hydrological changes are evaluated from the ecological point of view.
In spite of the fact that the year 1990 is indicated as a starting respectively zero state, animals as an important part of biota, were an object of interest of zoologists also in the previous years. This is documented by numerous data available in a large number of publications. The special feature of the whole Zitny ostrov island is its geographical position, and mainly unique and non-repeated biotopes like flowing waters of the Danube and its tributaries, stagnant waters of dead arms, floodplain forests, bogs, salt-grounds, meadows and pastures, steppe biotopes, gravel and sandy benches of the Danube, banks atc. This has called the attention of numerous specialists to faunistic, zoogeographical and ecological research, but also to commercial fishery and forestry already in the past.
An increased scientific activity oriented to the research of fauna on the territory and in the surrounding of the Gabcikovo project increased in eighties, in the time of the increased construction activity. Numerous zoologists concentrated their capacities to this region within the frame of their planned research works. Scientific reports and publications of various scientific institutions offered the results of this work. Several exemplars of the research of terrestrial animals are given in the following text.
The summarising publication, containing results of research of Mollusca in the region of the Danubian lowland before the construction of the Gabcikovo project is carried out by Steffek [37]. He summarises also data published earlier. The author in this publication determined malacocoenoses characteristic for soft and hard floodplain forests, for willow stands on the banks of the Danube and in the space among the river arms, in the forest steppe community (Crataegetum danubiale), at grassland stands of the Danubian dikes, at humid stands on the banks of canals and in humid meadows. In his further work [38] he also devotes attention to the territory of the Gabcikovo project from the aspect of gene-pool preservation of more species of Mollusca. Zitnanska [42] within the frame of the research dealing with spiders in the vicinity of Bratislava observed also arachnofauna of the floodplain forest, reed marshes vegetation and the Danubian dikes. Interesting is the author's finding, that up to 30 % of species settled in the floodplain forest is possible to order among so called expansive species, which are able to settle also devastated biotopes and they have the ability of adaptation to changed conditions of an environment. Gajdos [14] elaborated on communities of spiders on the island Kopac. In the forest steppe (Crataegetum danubiale) he determined arachnocoenoses in the community which is typical for a tree, shrub and herb layer and leaf litter. The ecological characteristic of the Araneae and changes in their taxacoenoses from 1977 to 1991 described Gajdos et al. [15] on 33 localities. Carnogursky at al. [4] dealt with diversity and the rate of similarity of some soil Arthropoda in the flood plain forest and their narrow argocoenoses. Kaluz [20] studied changes in the Acarina coenoses influenced by the absence of floods.
Heteroptera taxocoenoses of some biotopes in the influenced territory with the main stress to biotope of the forest steppe are characterised in work of Stepanovicova, Lapkova [41]. Heteroptera of grassland communities of the Danubian lowland was elaborated by Stepanovicova [39, 40]. Relations of free living bees (Apoidea) to nutritious plants on meadows in the region of Cicov characterises Belakova [1, 2]. Some authors devoted a special attention to the research of Coleoptera in the forest, grassland and coast communities, already before the construction of the Gabcikovo project and during various stages of construction works and thus under various changes of the biotopes. The first publication, which contains results of the research of Coleoptera since 1978-1979 is a work of Majzlan, Rychlik [31], who found 674 species on four localities and on more biotopes in the reach of the Danube river near Bratislava. They elaborated a prognoses of changes of taxocoenoses Coleoptera in connection with devastation of original biotopes. Their further work, mainly dealt with phytophagous and edaphic beetles [8, 9, 10, 12, 13, 26, 27, 28, 29, 30, 31, 32, and numerous others]. Information about fauna of Lepidoptera in the forest steppe on the Kopac island is presented by Kulfan [24] and the same author gives a complex picture about butterfly communities with daily activities on the whole influenced territory [25]. A number of faunistic and ecological data about an occurrence of Diptera in this area is sumarised in the works of Cepelak [5, 6], in which the results of research of following authors are described. They devoted their attention to this area already before the construction of the Gabcikovo project and also in the later period. There should be mentioned work of authors Gunarova, Halgos, Jedlicka, Kristofik, Kralikova, Orszagh, Slameckova, Stollar, Øehuøkova and Zajonc. A special attention deserves publication by Orszagh [33], which contains results of almost 20-year research (1967-1986) of some species of genus Culicoides from the surrounding of the whole Slovak stretch of the Danube river and in which the author is discussing changes in qualitative and quantitative composition of found species in connection with changes and eventual destruction of their biotopes. A complex view to species composition, their spread and potential explosive increase of the population density of some ectoparasites from orders Diptera and Siphonaphtera on influenced area is given by Jedlicka [16].
From terrestrial vertebrates is devoted attention to the fauna of Reptilia, Aves and Mammalia in the last decade. Kminiak [21] was carried out a research of Amphibia on the wider surrounding of Bratislava in 1987-1989 and within the frame of this research he observed their occurrence also in 10 localities of the Danubian lowland, on the stretch Bratislava - Petrzalka - Dobrohost. There are numerous publications about avifauna of the Danube river, eventually about the whole Zitny ostrov area, which are presented in the bibliography [17]. In the last period the research of ornitocoenoses was made by Kalivodova, Darolova and Kropil. From their publications and reports we are presenting first of all those, characterising bird communities in the area of the Gabcikovo project. Such contributions are for example work from the surrounding of Cicov [18, 19] and Gabcikovo [7, 22, 23]. From the data introduced in their work results show 109 bird species in the area of the Gabcikovo project. The area of the project became an important biotope for migrating and hibernating aquatic bird species [19]. The research of mammals in the Danubian lowland was orientated first of all to study small earthy mammals and important hunting species in the past. Tens of these researche papers are cited in the above-mentioned zoological bibliography [17]. Some specialists dealt with research of mammals, mainly micromammals in the area, mainly in its northern part, in the last decade. First of all there is works of Pachinger [34, 35, 36], which deals with a research of small earthy mammals in this territory since 1978. He records gradual changes in their synusia in consequence of a decline of their origin biotopes, mainly floodplain forests and the Danubian river arms. The work of this author about an occurrence of Mustela nivalis on the Danube river banks in the vicinity of Bratislava [34] is also important, as well as the work of Brtek [3], which evaluates an influence of the large flood in 1965 to populations of small earthy mammals. The occurrence of more rare species of Insectivora and Rodentia in the near-bank zone of the Danube river and in the river arm system is discussed by Dudich et al. [3], Brtek [3] and Pachinger [35].
A research of the terrestrial animals as an important particle of biota is covered in the project "Monitoring of natural environment influenced by the construction and operation of the Gabcikovo project". It is obvious, that in the scientific group monitoring the terrestrial fauna remained more zoologists, who were dealing with a faunistic and ecological research in this area also in the previous years. To provide the most complex knowledge other scientific workers of the Institute of Zoology of the Slovak Academy of Sciences and Faculty of Natural Sciences of Comenius university in Bratislava joined the team. It means that at present 19 zoologists there are involved in monitoring of the selected groups of terrestrial animals within the frame of the professional group "biota". In consequence of their specialisation is there a research of Mollusca (Lisicky, Cejka), Araneae (Gajdos, Krumpalova), Acari (Kaluz), Chilopoda (Orszagh, Orszaghova), Collembola (Carnogursky), Dermaptera Majzlan), Planipennia (Jedlicka), Megaloptera (Jedlicka), Panorpata (Jedlicka), Heteroptera (Bianchi, Stepanovicova), Coleoptera (Majzlan, Steklova, Sustek, Kodada) Hymenoptera (Lukas), Lepidoptera (Kulfan), Aves (Darolova), Mammalia ( Pachinger, Kristofik Masan).
After overcoming some problems with the introduction of the monitoring system and the monitoring of "biota", which were in the conception and in the organisation, than also in personnel and monitoring methods, it is possible to state, that the results obtained since 1990 confirm the hypothesis and give at least a partial answer to the question how the changes in natural environment and the whole ecosystems in the influenced area have manifested to structure and function of terrestrial zoocoenoses. The yearly results of the research (1990-1994) were submitted in the form of annual reports. The research gradualy improved. Monitoring started by the inventory of species composition of certain animal groups, continued by recording gradual changes in qualitative and quantitative composition of species, up to the evaluation of the state after finishing of the majority of technical and water-management interference and after setting into operation the Gabcikovo project. In spite of the fact that the period of five years is from the aspect of the final goal of the monitoring only a starting stage, the character of up to present results has its specific significant achievements. These are mainly recording of the state, which followed such an important interference as the essential lowering of the area of floodplain forests, the construction of the by-pass canal, turning a large part of waters from the main Danube river-bed aside, establishing of the Cunovo reservoir water area, supplying river branches with water and numerous others interferences. Large changes of numerous biotopes and their physical qualities were carried out, first of all in the soil moisture conditions. As a consequence of such an essential interference the character of vegetation changed gradually followed by changes in the composition of animal communities.
Based on the results of the observation of qualitative-quantitative structure of taxocoenoses Mollusca, Chilopoda, Araneae, Acari, Collembola edaphic and epigean Heteroptera and Coleoptera there two essential phenomena were manifested during five years. The first one is a lowering (decrease) of humid conditions in the soil of floodplain forests on area, which is situated between the by-pass canal and the old Danube close to the river-bed and which was manifested in 1992 after the diversion of the Danube water to the by-pass canal. The second phenomenon is an increase of soil moisture in the upper part of territory at reservoir, after 1993, after start of operation of the Gabcikovo structures.
As a consequence of groundwater level decrees, which was manifested most expressively at MA 6 (Dunajske kriviny - Dobrohost) situated on the northern margin of the inner Danube delta, close to the beginning of the by-pass canal, it was possible to observe gradual changes in the species composition of almost all epigean and edaphic communities of evertebrates, tending to retreat of typical hygrophilous species, to decreasing of their population density and to increasing of presence of less pretentious mesohygrophilous species, which in consequence of gradual aridization and with this connecting ruderalization of the vegetation penetrated the floodplain forest from surrounding biotopes. This situation was manifested in malacocoenoses by a retreat of typical hygrophilous species, mainly Carychium minimum, Succinea putris and Zonitoides nitidus which occurred here only rarely in the terrain depressions, where there were still preserved relatively suitable humid conditions. Changes in qualitative representation of Chilopoda are manifested by increasing their species spectrum about species, which prefer drier biotopes and since 1993 also by population density increase of of eurytopic species Lithobius forficatus, which documents the gradual ruderalization in consequence of soil desiccation and a decrease of the groundwater level almost by about 1 m. These changes of hydrological conditions were gradually manifested also within arachnocoenoses, mainly by a retreat of hygrophilous species, typical for soft floodplain forests and by an increase of a number of euryecnic, but also xerophilous species as for example Ozyptyla praticola and Pardosa lugubris. Collembola which belongs to bioindication significant groups of edaphon, reacted also very sensitively to desiccation and aerating of the soil, which was manifested at all MP situated in floodplain forests between the power canal and the old Danube river-bed. The character of Collembola taxocoenoses was gradually determined by a retreat of stenoecious hygrophilous species, by an increase of occurrence of more tolerant but even xerothermophilous species and by increased population density of euedaphic species, which are typical for drier, more aerated soils. Changes in the qualitative composition of taxocoenoses of epigean Coleoptera were also manifested by changes of species spectrum, a retreat of stenoecious hygrophilous species respectively by lowering of their population density and immigration of forest-mesohygrophilous but also euryecnic species from the surrounding field and grassland communities, which represent in a soft floodplain forest xenoceous elements. From family Carabidae there are in forest community Salici-Populetum such species as Abax ater, Carabus coriaceus, Carabus ullrichi, Carabus hortensis and Carabus nemoralis. Also in taxocoenoses of epigean Heteroptera we recorded a lowering population density of eudominant hygrophilous species Drymus brunneus and an increased qualitative composition of epigean bugs about some meso- to xerophilous species as Graptopeltus lynceus, Xantochilus quadratus, Peritrechus geniculatus, which again correspond to changes of the hydrological regime of floodplain forests, decrease of soil moisture and to following ruderalization of the vegetation. The only exception are edaphic Curculionidae, with not manifested influence of aridization and ruderalization by lowering of population density of dominants, neither by immigration of more tolerant species, which would represent in floodplain forests xenocoenous elements. Occurring species represent typical geobionts, with a limited motion activity and with good ability of adaptation to fluctuations of soil moisture.
The negative influence of changes of hydrological regime in the floodplain forest in the region of the by-pass canal, which influenced structure of taxocoenoses of the edaphic and the epigean evertebrates was forced up also by climatic conditions, mainly by high average daily temperatures, a long-lasting drought and an absence of floods in last years. Cumulating of all negative anthropogenous even natural factors and synergism of its impact were manifested on the changes of the structure of monitoring zoocoenoses, which are loosins a character of communities typical for soft floodplain forests since 1992. In spite of that, at present it is impossible to predict decline of stability of the whole floodplain forest ecosystem. To continue in monitoring of bioindicatively significant animal communities will be necessary for observation of intensity and trend of these changes, its incidental reversibility or beginning of succession development of this ecosystem.
Further phenomenon, which is characteristic for the territory and acts contradictory as the above-mentioned aridization of floodplain forests in the region of by-pass canal, is a change of hydro-pedological conditions in the upstream part of this area, influenced by the Cunovo reservoir and manifested since 1993 by an increase of soil moisture. At monitoring plots (MP 1, 2a, 2b, 3). we observed terrestrial evertebrates in forest communities mainly at MP 1 and 3, where monitoring is taking place since 1991. Results, which were obtained by a research of taxocoenoses Mollusca, Chilopoda, edaphic Coleoptera, epigean Heteroptera and Lepidoptera were different. The most expressive they were manifested on the structure of malacocoenoses, which react to changes of soil moisture conditions most sensitively. By increasing of the groundwater level there were also created conditions at some MP for an occurrence of typical hygrophilous species, which did not occurre here in the previous years. Also in taxocoenoses of Chilopoda it is possible to observe changes of species spectrum, even changes in the population density of dominant species. For example on the Kopac island a number of eurytopic species Lithobius forficatus decreased and there is an increase of the qualitative representation of Lithobius aeruginosus, which is a typical species of floodplain forests in the Danubian lowland if compared with the year 1991. At the other MP in this area changes were not so essentially manifested, and species characteristic for floodplain forests occurred here during the whole monitoring period. The only differences in their number expressed by values of dominance document gradual regeneration and a higher stability of Chilopoda taxocoenoses, influenced by increasing of soil moisture conditions.
From other monitoring groups of terrestrial animals the changes begun to manifest in taxocoenoses of Lepidoptera with a daily activity after 1993. Meanwhile in the previous years of a long-term research (1981-1994) at MP 1, 2a, 2b, 3 almost only xerotermophilous species, characteristic for dry open biotopes occured. After creating the Cunovo reservoir in 1993, more essential changes in species composition of Lepidoptera took place as well as an occurrence of some meso-hygrophilous species. For example at MP 1 it was hygrophilous species Heteropterus morpheus, at MP 3, mesophilous species Hesperia comma and hygrophilous species - indicator of humid meadows Lyceana dispar, at which air-raid of this species was recorded also at MP 2a, and 2b.
There were not recorded any decisive changes, neither in the species spectrum, nor in the population density of occurring species after the creation of the Cunovo reservoir and increasing of groundwater level in communities of edaphic Coleoptera and epigean Heteroptera, monitored in the period from 1991 to 1994. Dominant distribution had mesohygrophilous to xerophilous species during the whole monitoring period. Qualitative structure of taxocoenoses Coleoptera and Heteroptera at MP 1 and 3 had a different character than at the other plots. This was manifested first of all by absence of hygrophilous species, mainly species Drymus brunneus (Heteroptera), which is a very sensitive indicator of sufficient moisture in floodplain forests. Eudominant position had here mesohygrophilous species Legnotus limbosus, which populations occur more abundantly only in floodplain forests of a drier character. An important factor, which influences a qualitative structure of Heteroptera even Coleoptera taxocoenoses at MP 1 and 3, is also a tight vicinity of the forest steppe community Crataegetum danubiale, from where xerothermophilous and psamophilous species penetrate the floodplain forest, mainly in the spring and autumn period (in connection with hibernation). Based on the many year monitoring it will be possible to express whether the specific character of edaphic Coleoptera and epigean Heteroptera taxocoenoses will be changed in the areas influenced by the increased groundwater level since 1993.
Based on the data obtained by monitoring of terrestrial animals it is possible to state, that numerous results have a bioindicative validity. It is possible to use them to estimate a degree of changes and their progress in the natural environment, mainly floodplain forests and. The results have shown, that the structure of terrestrial zoocoenoses is influenced by natural factors, mainly soil moisture conditions influenced by a depth of the groundwater level, surface floods, a long-lasting drought and so on and by anthropogenous factors, like cutting away of woods and harvesting of forests and devastation of the terrain in connection with construction works, causing aridization, ruderalization of vegetation and followed also by changes in the structure of the observed zoocoenoses. To evaluate an intensity and further tendency of these changes will be possible only on the basis of a long-term monitoring using indicative animal communities as sensitive indicators of changes in this territory.