The River Danube - Biodiversity and Habitat Assessment Based on Trichoptera Assemblages

The river Danube - biodiversity and habitat assessment based on Trichoptera assemblages

Wolfram Graf1, Johann Waringer2, Philipp Wenzl2, Andreas Chovanec3, Otto Moog1

Keywords: Trichoptera, Danube, wetlands, biodiversity, habitat assessment

Introduction Within the last two decades intensive studies on wetlands were carried out along the river Danube at Altenwörth, Greifenstein and Klosterneuburg west of Vienna (Waringer 1991, Graf 1999, Chovanec et al. 2005). Trichoptera were chosen as indicators of overall habitat quality of wetland areas because this insect order has evolved a wide range of physiological, morphological and behavioural adaptations, allowing them to colonise a variety of lotic and lentic habitats typically present in functioning floodplain systems in a very specific way. Species composition is heavily dependent on the backwater type and its connectivity with the main channel thus reflecting environmental conditions as demanded by the EU Water Framework Directive. Species inventories and Floodplain Indices according to Chovanec et al. (2005) are presented. The relatively high biodiversity of wetlands compared to the main channel and their importance as a vital segment of aquatic ecosystem functioning is documented.

Methods For setting up of a complete species inventory, light traps combined with sweeping net catches were used. Larval and pupal records as well as adults catched by emergence traps were documented. The battery-driven light traps were equipped with blacklight tubes. One sampling period encompassed at least one night per month between April and October. A representative number of sampling sites was chosen along transects of the wetlands investigated. The procedure for calculating the Caddisfly Habitat Index (CHI) is given elsewhere (Waringer & Graf 2002, Chovanec et al. 2005), species-specific habitat values for CHI calculation follow the classifications of Waringer et al. (2005). The description of the habitat types follows the gradient of lateral connectivity ranging from dynamic H1-waters (Eu-/Parapotamon) to H5-waters (Palaeopotamon) (Amoros et al. 1987, Amoros & Roux 1988). The criteria for the differentiation of the habitat types are water permanency, connectivity with the main channel and the coverage by macrophytes. A low CHI value indicates species preferences for lotic habitats, whereas a high CHI (>2) is indicative for elements of Plesio- and Palaeopotamon habitats or temporary waterbodies.

1 University of Natural Resources and Applied Life Sciences, Hydrobiology and Aquatic Ecosystem Management, Max Emanuel-Straße 17, A-1180 Vienna, Austria 2 University of Vienna, Institute of Ecology and Conservation Biology, Althanstraße 14, A-1090 Vienna, Austria 3 Federal Environment Agency, Spittelauer Lände 5, A-1090 Vienna, Austria 241 Results and Discussion A total of 106 species were documented along the Danubian wetlands at the three investigation sites (Table 1); this number exceeds the caddisfly inventory given earlier for the whole Austrian part of the Danube by Moog et al. (1995, 2000) and represents more than one third of the well known overall species inventory of Austria (Graf et al. 1995, 2002). The species compositions as well as the species numbers are quite similar for Greifenstein (73 species) and Klosterneuburg (72 species). Altenwörth shows the highest number with 86 species. Caddisfly Habitat Indices range from 1 to 4.8 at Greifenstein and Altenwörth, and from 1 to 4.1 in Klosterneuburg, respectively. The median of the CHI values decreases from 2.6 at Greifenstein to 1.6 at the other wetlands, which indicates a shift to plesio- and palaeopotamal habitats (Fig. 1).

3 CHI

CHI range Greifenstein Altenwörth Klosterneuburg Median Fig. 1: Range plot of CHI values, CHI ranges and medians at the three sites.

The wetlands at Greifenstein are ecologically dominated by the Giessgang's discharge that restores to some degree the historic wetland situation. Due to reduced dynamics, hydrologically more stable habitats of palaeopotamon characteristics can be found, resulting in a high proportion of littoral elements. For example, all Central European Holocentropus-species, which are adapted to macrophyte-rich and shallow waters, are documented here. Altenwörth seems to be more dynamic at first sight, but the high species number as well as the lower median of the CHI values is a result of tributaries like the Mühlkamp and the Kamp which flow into the Danube at this floodplain section. The wetlands of Klosterneuburg cover a comparatively smaller area and are dominated by the “Gschirrwasser”, an irrigation channel inhabited by Danubian faunal elements. The CHI range is not higher than 4.1, because palaeopotamon habitats and their fauna decline in favour of rheophilous species. Despite the loss of dynamics due to human activities, Trichoptera biodiversity can still be regarded as high. The species inventories at each of the wetlands investigated consist of a quite stable compartment of the Eu- and Parapotamon (the main channel-fauna e.g. Glossosomatidae, Hydropsychidae and Brachycentridae species) and – according to the specific hydrologic and geomorphologic conditions within the floodplain – a high share of faunal elements of standing waterbodies which are well adapted to different succession stages (Plesio- and Palaeopotamon, including intermittent waters: Leptoceridae, Hydroptilidae, Phryganeidae, Polycentropodidae and Limnephilini species). One typical species inhabiting main channels of large rivers, Rhyacophila 242 pascoei was not recorded later than 1989 in Austria and has to be considered to have undergone a dramatic population loss. This illustrates the fact that the Trichoptera wetland fauna is especially sensitive and endangered due to the decline of dynamic processes and habitat fragmentation. In the present case study these species (characterised by CHI values > 2) contributed 39 % at Altenwörth, 43 % at Klosterneuburg and 52 % at Greifenstein to the overall biodiversity. Table 1 gives the Trichoptera species inventory at the three floodplain sections investigated. Table 1: Species inventory at the three floodplain sections investigated; CHI = Caddisfly Habitat Index according to Waringer et al. (2005); - = species not classified

Species/Site Greifenstein Altenwörth Klosterneuburg CHI

Rhyacophila dorsalis (CURTIS, 1834) X X X 1 Rhyacophila fasciata HAGEN, 1859 X 1 Rhyacophila pascoei MCLACHLAN, 1879 X 1 Rhyacophila nubila (ZETTERSTEDT, 1840) X 1 Agapetus delicatulus MCLACHLAN, 1884 X X X 1 Agapetus laniger (PICTET, 1834) X X X 1 Agapetus ochripes CURTIS, 1834 X X 1 Glossosoma boltoni CURTIS, 1834 X X X 1 Agraylea sexmaculata CURTIS, 1834 X X X 3.6 Agraylea multipunctata CURTIS, 1834 X 3.6 Hydroptila angulata MOSELY, 1922 X X 1.8 Hydroptila pulchricornis PICTET, 1834 X 3.4 Hydroptila sparsa CURTIS, 1834 X X X 1.6 Hydroptila forcipata EATON, 1873 X X 1.2 Hydroptila vectis CURTIS, 1834 X X 1.2 Ithytrichia lamellaris EATON, 1873 X X 1.6 Allotrichia pallicornis (EATON, 1873) X 1.5 Orthotrichia costalis (CURTIS, 1834) X X X 3.4 Orthotrichia tragetti MOSELY, 1930 X X X 3.5 Oxyethira flavicornis PICTET, 1834 X X X 2.9 Wormaldia cf. subnigra MCLACHLAN, 1865 X - Cheumatopsyche lepida (PICTET, 1834) X X 1 Hydropsyche angustipennis (CURTIS, 1834) X X X 1.2 Hydropsyche bulbifera MCLACHLAN, 1878 X X X 1.2 Hydropsyche bulgaromanorum MALICKY, 1977 X X X 1.2 Hydropsyche guttata PICTET, 1834 X X 1 Hydropsyche incognita PITSCH, 1993 X X X 1 Hydropsyche instabilis (CURTIS, 1834) X - Hydropsyche pellucidula (CURTIS, 1834) X X X 1 Hydropsyche contubernalis MCLACHLAN, 1865 X X X 1.2 Hydropsyche modesta NAVAS, 1925 X X X 1.2 Hydropsyche ornatula MCLACHLAN, 1878 X 1 Hydropsyche saxonica MCLACHLAN, 1884 X 1 Hydropsyche siltalai DÖHLER, 1963 X X 1 Cyrnus crenaticornis (KOLENATI, 1859) X X 3.8 Cyrnus flavidus MCLACHLAN, 1864 X 3.8 Cyrnus trimaculatus (CURTIS, 1834) X X X 2.6 Holocentropus dubius (RAMBUR, 1842) X 3.6 Holocentropus picicornis (STEPHENS, 1836) X 3.6 Holocentropus stagnalis (ALBARDA, 1874) X X 3.4 Neureclipsis bimaculata (LINNAEUS, 1758) X X X 1.7 Polycentropus flavomaculatus (PICTET, 1834) X X X 1.5 Polycentropus schmidi NOVAK & BOTOSANEANU, 1965 X - Lype phaeopa (STEPHENS, 1936) X X X 2.3 Psychomyia pusilla (FABRICIUS, 1781) X X X 1.6 Tinodes waeneri (LINNAEUS, 1758) X X X 2.9 Tinodes pallidulus MCLACHLAN, 1878 X - Ecnomus tenellus (RAMBUR, 1842) X X X 2.9 Phryganea bipunctata RETZIUS, 1783 X X X 3.5 Phryganea grandis LINNAEUS, 1758 X X X 3.5 Agrypnia varia (FABRICIUS, 1793) X X X 3.5 Agrypnia pagetana CURTIS, 1835 X X 3.5 243 Species/Site Greifenstein Altenwörth Klosterneuburg CHI

Trichostegia minor (CURTIS, 1834) X X 4.8 Micrasema setiferum (PICTET, 1834) X 1.2 Brachycentrus subnubilus CURTIS, 1834 X X X 1.2 Anabolia furcata BRAUER, 1857 X X X 2.6 Enoicyla reichenbachi (KOLENATI, 1848) X - Glyphotaelius pellucidus (RETZIUS, 1783) X X X 3.5 Grammotaulius nigropunctatus (RETZIUS, 1783) X 4.1 Halesus radiatus CURTIS, 1834 X X X 1.3 Halesus digitatus (SCHRANK, 1781) X 1.3 Halesus tessellatus (RAMBUR, 1842) X X 1.3 Ironoquia dubia (STEPHENS, 1837) X - Limnephilus affinis CURTIS, 1834 X X 3.8 Limnephilus auricula CURTIS, 1834 X X 3.8 Limnephilus binotatus CURTIS, 1834 X X 3.8 Limnephilus decipiens (KOLENATI, 1848) X X 3.8 Limnephilus extricatus MCLACHLAN, 1865 X 2 Limnephilus flavicornis (FABRICIUS, 1787) X X X 4 Limnephilus griseus (LINNAEUS, 1758) X 4.8 Limnephilus hirsutus (PICTET, 1834) X 2 Limnephilus ignavus MCLACHLAN, 1865 X 2.5 Limnephilus lunatus CURTIS, 1834 X X X 3 Limnephilus rhombicus (LINNAEUS, 1758) X X 3.4 Limnephilus sparsus CURTIS, 1834 X X 4 Limnephilus stigma CURTIS, 1834 X 3.5 Potamophylax cingulatus STEPHENS, 1837 X 1 Potamophylax rotundipennis (BRAUER, 1857) X 1.5 Stenophylax permistus MCLACHLAN, 1895 X X - Goera pilosa (FABRICIUS, 1775) X X X 1.1 Silo nigricornis (PICTET, 1834) X X 1 Lepidostoma hirtum (FABRICIUS, 1775) X X X 1.5 Lepidostoma basale (KOLENATI, 1848) X X X 1.2 Athripsodes albifrons (LINNAEUS, 1758 X X 1.2 Athripsodes aterrimus (STEPHENS, 1836) X X X 3.6 Athripsodes bilineatus (LINNAEUS, 1758) X 1.2 Athripsodes cinereus (CURTIS, 1834) X X X 1.2 Ceraclea albimacula RAMBUR, 1842 X X X 1.4 Ceraclea annulicornis (STEPHENS, 1836) X X X 1 Ceraclea dissimilis (STEPHENS, 1836) X X X 1 Ceraclea fulva (RAMBUR, 1842) X X 4 Ceraclea nigronervosa (RETZIUS, 1783) X X 1.5 Ceraclea senilis (BURMEISTER, 1839) X 3.7 Leptocerus tineiformis CURTIS, 1834 X X X 4 Mystacides azurea (LINNAEUS, 1761) X X X 3 Mystacides longicornis (LINNAEUS, 1758) X X X 2.8 Mystacides nigra (LINNAEUS, 1758) X X X 3 Oecetis furva (Rambur, 1842) X X X 4 Oecetis lacustris (PICTET, 1834) X X X 3.5 Oecetis ochracea (Curtis, 1825) X X X 3.8 Oecetis notata (RAMBUR,1842) X X X 1.5 Oecetis testacea (CURTIS, 1834) X X 1.7 Setodes punctatus (FABRICIUS, 1793) X X X 1.4 Triaenodes bicolor (CURTIS, 1834) X X X 4 Notidobia ciliaris (LINNAEUS, 1761) X - Molanna angustata CURTIS, 1840 X 1.5 Total 106 73 86 72

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