ANNEX 3 Typology of the Danube River and its reference conditions

1. Brief characterisation of the abiotic characteristics of the Danube section types
Section Type 1: Upper course of the Danube
(rkm 2786: confluence of Brigach and Breg ­ rkm 2581: Neu Ulm)
Canyon reaches alternate with plain floodplain sections dominating at the right. Channel form is
sinuous to meandering and braided. The slope varies between 0.75 and 1.38 .
The main channel substrates are composed of bedrock, head-sized boulders with a variable percentage
of cobble, gravel and sand. In the floodplain section (with more than 300 m width) riffle and pool
sections vary moderately. The bank structure is abort and sliding.
Due to the karst landscape the highly dynamic discharge regime is characterised by water exfiltration
at section Immendingen to Möhringen and sporadically until Fridingen (MNQ 3 m3/s; MQ 7-8 m3/s;
MHQ approx. 20 m3/s). In case of total exfiltration the loss of water is substituted by tributaries and
springs.
The hydrological regime is characterised by a high water level in February and March and a low water
level between August and September.
The river shows a high percentage of eupotamon with primarily lotic side arms on the right side of the
floodplain section.

Section Type 2: Western Alpine Foothills Danube
(rkm 2581: Neu Ulm ­ rkm 2225: Passau)
In this section the Danube shows an anabranching channel form (more than 65 percent) interspersed
with a meandering morphology. Trough valley reaches alternate with meandering valley sections. A
highly dynamic breadth erosion causes varying widths of the channels and shallow water depths.
Gorge sections are at Steppberg (km 2486 - 2478) and the Weltenburger Enge (km 2422 - 2414).
The channel substrates are dominated by cobbles, gravel or sand. Sporadically a mixture of sand and
gravel is present.
The slope varies between 1.1 at Ulm and 0.3 at Regensburg.
The river shows a high percentage of eupotamon. The anabranching reaches are characterised by
numerous side channels providing predominantly lotic habitats. Due to highly dynamic channel
routing the in-channel islands are naturally unvegetated or covered by annuals.
The floodplain vegetation consists of alluvial softwood and hardwood forests and wetlands (mires and
swamps).

Section Type 3: Eastern Alpine Foothills Danube
(rkm 2225: Passau ­ rkm 2001: Krems)
This section type is composed of two main parts: the breakthrough section "Oberes
Donautal" (km 2225 - 2160) and the anabranching stretch "Austrian Machland region" (km 2094 -
2084).
The breakthrough section is characterised by a steep, narrow incised meander valley that confines the
lateral development of the river channel. Bedrocks interspersed with gravel are the dominant channel
substrates.
Four short river reaches with chutes formed by outcropping bedrocks (Kachlets) are present. Such
reaches feature high flow velocities and complex flow patterns. Gravel areas which fall dry in times of
extreme low water amount to 5 ha per km.
The average slope value for this section is 0.43 .
The channel system of the Machland stretch is branched by several islands and gravel bars. This reach
can be designated as a gravel-dominated, laterally active anabranching section. The sinuosity of the
main channel is 1.32, its mean width amounted to 550 m at low flow and 730 m at summer mean
water, and mean depth could reach 3.8 m along the thalweg.
Danube discharge is mainly influenced by alpine flow conditions and peaks in spring/summer due to
the snowmelt in the Alps. Shallow-water zones with gentle bed gradients are a formative element. This
enables a high diversity of depths, flow velocities and substrate conditions, resulting in a broad
spectrum of micro- and meso-habitats with extensive shorelines.

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The gravel banks/islands and highly outcropping rocks in the breakthrough area offer a lotic
environment almost throughout the whole reach. Most tributaries discharge into the Danube River at
locations with large gravel bars and therefore provide valuable spawning habitats for rheophilic fish
species. The backwaters offer interesting refuge habitats during floods and special lentic habitats for
stagnophilic species.
In the anabranching stretch the river-floodplain system is characterised by eupotamon water bodies
(main channel and side arms) to a very high extend, offering a primarily lotic environment (97 percent
of the overall water surface area at low flow). Para-, plesio- and palaeopotamon water bodies are less
frequent in relation to eupotamon ones. They represent a great variety of distinct lentic habitats and
contribute to the high extend of aquatic/terrestrial interfaces. The various floodplain elements are in
constant modification and renewal due to the strong erosion/sedimentation processes.

Section Type 4: Lower Alpine Foothills Danube
(rkm 2001: Krems ­ rkm 1789.5: Göny / Klizská Nemá)
The section type represents the beginning of lowland reaches with meandering, anabranching and
braided channels exceptive two small breakthrough valleys at the Vienna Gate (km 1949 - 1935) and
Devin Gate (km 1880). Anabranching reaches are situated in the Vienna Basin and the Danube
Lowland downstream Bratislava. Here, the Danube forms an inland delta with three main river
branches of braided or anastomosing-meandering character: the Great Danube branch (middle), Malý
(Little/Lesser) Danube (north, km 1869 - 1768), Mosoni Danube (south, up to Gönyü km 1791). These
branches form a large accumulation zone composed by the Danubian islands: Large Danube Island
"Zitný ostrov" (on the north side) and Little Danube Island "Szigetköz" (on the south side). Low
current velocities and high groundwater levels generate a large wetland area. Some of the branches are
only active during floods. The slope value decreases from 0.35 to 0.10 at Gönyü.
The dominant main channel substrates are represented by large cobbles and gravel in the breakthrough
sections, and medium to coarse gravel layered by sands and loam in the accumulation zone of the
Danube Lowland. The gravel bed near Bratislava is characterised by rapid rates of lateral erosion and
an extensive area of point bars and gravel bars. These bars are partially covered by incipient and older
woodlands.
The active floodplain varies between 10 km upstream and downstream Vienna to 6 km upstream Váh.
The floodplain area of the inland delta (Schütt/Ostrov) amounts to more than 20,000 ha and is covered
by one of the largest floodplain forests in central and south-eastern Europe. It represents the habitat of
numerous macrophyte communities, humid willow-poplar forests, ash-elm stands and drier elm-oak
formations.
The breakthrough reaches show primarily lotic environments composed of gravel banks and islands.
Backwater sections form lentic habitats during floods for stagnophilic species.
In the anabranching reaches former braided segments that became disconnected from the main channel,
and old meanders or similar forms resulting from another morphological type without direct
connection to the main channel are frequent.

Section Type 5: Hungarian Danube Bend
(rkm 1789.5: Göny / Klizská Nemá ­ rkm 1497: Baja)
In this section the Danube passes breakthrough sections (the Danube bend) and lowland areas
(Hungarian plain), and changes its watercourse from eastward to southward. In the lowland area the
Danube flows in a plain floodplain valley and shows high anabranching (mainly cut-off loops)
intensity (35 to 65 percent) or meandering (>1.26 sinuosity degree).
The dominant main channel substrate consists of gravel in different sizes (from coarse gravel to fine
and medium sized gravel), frequently interspersed with sand and hand sized cobbles, organic sludge,
mud, silt and clay in small percentages. In the breakthrough section coarse blocks with variable
percentages of cobble and sand are present.
The average slope value varies between 0.10 at Gönyü and 0.17 to 0.07 in the Hungarian
bend.
The average width of the main channel amounts to 350 m; the mean depth is 4 to 5 m. The main
channel shows moderate breadth erosion. This section is characterised by a mean current velocity of
0.5 m/s.

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After passing the breakthrough section (Danube bend) the Danube forms two important isles:
Szentendre (km 1692 - 1657) and Csepel (km 1642 - 1586).
The bank structure is variable with multiple sliding banks, isolated fallen trees, wood collections and
spur banks.
The floodplain is between 300 m (upstream Budapest) and 1500 m (downstream Budapest) wide.
Lotic side arms and dead arms, cut off channels and oxbow lakes, temporary side arms and standing
water bodies fed by the tributaries are present in the floodplain.
The floodplain vegetation is represented by a dominant alluvial softwood forest. Isolated alluvial
hardwood forests and mixed native forests are also present.
The dominant aquatic habitat in this section is the eupotamon which has a mean width of 500 m. Less
than 10 percent parapotamon, plesiopotamon and palaeopotamon types are present. The percent area
of terrestrial habitats (e.g. banks, islands) makes up approx. 10 percent of the entire eupotamon.
Biotic microhabitats are frequently formed by living parts of terrestrial plants and tree trunks, rarely
accompanied by macrophytes, submerged plants, CPOM, FPOM and debris.

Section Type 6: Pannonian Plain Danube
(rkm 1497 : Baja ­ rkm 1075 : Bazias)
The Danube in this section is passing through a floodplain landscape with areas of accumulation,
having a meandering and plain floodplain valley with an anabranching channel (mainly cut-off loops)
and meandering sections (degree of sinuosity: 1.06 ­ 1.25 and partially more than 2).
A moderate breadth erosion is present in the main channel (average width: approx. 750 m, mean depth:
6 m). The main channel substrates are dominated by sand, and frequently fine to medium-sized gravel
occurs. Mud, sludge, silt, loam, and clay are rare. The average slope value remains 0.04 , varying
between Baja and Drava from 0.07 to 0.05 .
Wood and fallen trees are frequently present on the river bank, the structure is partially sliding.
The large floodplain (max. width: 30 km) is characterised by a diversity of water bodies close to the
stream: lotic side arms and dead arms, cut off channels, oxbow lakes and standing water bodies fed by
the tributaries. Alluvial hardwood and softwood forests are dominant. Mixed native forests represent
the frequent vegetation types in the floodplain. The vegetation in few sections is sporadically
composed by meadow, wetland (mire) and reeds.
In the lower reach of this Danube-section (Croatia/Serbia and Montenegro) the largest tributaries
(Tisza and Sava) substantially increase the catchment area and changes the alpine runoff character of
the Danube.
The average current velocity in this section is 0.4 m/s.
The dominant aquatic habitat in this section is the eupotamon, frequently accompanied by para- and
palaeopotamon. The percent area of terrestrial habitats (e.g. banks, islands) represents approx.
20 percent of the entire eupotamon.
The biotic microhabitats are frequently represented by debris, CPOM, FPOM and sludge. Less than
30 percent submerged plants, filamentous algae, macrophytes, living parts of terrestrial plants as well
as dead wood (tree trunks) are present.

Section Type 7: Iron Gate Danube
(rkm 1075: Bazias ­ rkm 943: Turnu Severin)
Djerdap/Iron Gates canyon is composed of four canyons (necks) and three extensions.
The braided channel is mostly rocky and shows areas with deposits of medium and small particles of
alluvial materials (banks and islands). The main channel has an average width of about 750 m and runs
in a canyon or trough valley form. Its mean depth amounts to approx. 5.5 m. Slope values range from
0.04 to above 0.25 .
The dominant main channel substrates are represented by large cobbles, boulders and bedrocks
(numerous rocks are situated directly under the water surface), and frequent coarse, medium and
partial fine gravel interspersed with sand and mud in the slow-flowing parts.
The river bank is isolated abort and sliding, and fallen trees and wood collections are frequently
present. The breadth erosion is moderate. Spur banks are present. The section is characterised by high
current velocity (1.8 up to 5 m/s) and by longitudinal erosion. Shallow-water zones with gentle bed
gradients are dominant. This enables a high diversity of depth, flow velocity and substrate condition.

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The flooded area is reduced to an average width of about 150 m. Temporarily flooded areas (mostly to
the outflow of the Nera tributary) are present in the floodplain as well as deciduous native forest along
with the hardwood alluvial forest and meadow.
The potamon offers a primarily lotic environment. The area of terrestrial habitats represents only
10 percent of the entire eupotamon area. Living parts of terrestrial plants, FPOM and debris are rare.

Section Type 8: Western Pontic Danube
(rkm 943: Turnu Severin ­ rkm 375.5: Chiciu/Silistra)
The Danube is passing a floodplain landscape with higher plains of terraced accumulation in a
meander and plain floodplain valley. The right bank is high and steep, the left bank is low and terraced
with wide floodplains.
The channel is partially braided with bars and islands and partially anabranching (mainly cut-off
loops). Meandering reaches are also present (degree of sinuosity 1.06-1.25). The main channel has
moderate breadth erosion (average width of 830 m and mean depth of 8.5 m). Main channel substrates
frequently vary from fine and medium gravel to sand accompanied by small percentages of coarse
gravel and mud. The average slope values remains 0.04 .
Multiple wood collections and isolated fallen trees are present on the river banks. Their structure
varies: abort and sliding banks are present as well as bank spurs and nest banks. This section is
characterised by moderate values of current velocity (1.30 m/s).
The average width of the floodplain is about 8000 m and the diversity of water bodies in this area
close to the stream is large: lotic side arms connected to the main channel at both ends, cut off
channels, oxbow lakes and standing water bodies fed by the tributaries.
Deciduous native forest, wetlands (mire) and open grass is the dominant vegetation in the floodplain,
often accompanied by alluvial soft wood forest, meadow and reeds. Sporadically the vegetation is
missing.
Average width of the eupotamon is 1500 m. The area of terrestrial habitats represents 75 % of the
entire eupotamon.
The biotic microhabitats are frequently represented by filamentous algae and macrophytes as well as
CPOM and debris. In less than 30 percent living parts of terrestrial plants and FPOM are present.

Section Type 9: Eastern Wallachian Danube
(rkm 375.5: Chiciu/Silistra ­ rkm 100: Isaccea)
The Danube changes its watercourse northward forming a wetland area with two large isles (374-
248 km Balta Ialomita and 238-169 km Balta Braila) and many natural lakes. The valley form is a
meander and plain floodplain valley with a braided channel (mostly long and narrow islands),
composite anabranching channel and meandering sections (>1.26 of sinuosity degree).
The main channel has an average width of 650 m, a mean depth of 10.5 m and shows moderate
breadth erosion. The dominant channel substrate is sand, frequently interspersed with mud, organic
sludge, silt, loam and clay. In small percentages gravel is present in fine to medium size.
The bank structure is variable with multiple abort and nesting banks and bank spurs. Fallen trees and
sliding banks are sporadically present.
The floodplain has an average width of 5500 m. Lotic side arms and dead arms, cut off channels and
oxbow lakes, temporary side arms and standing water bodies fed by the tributaries form the water
bodies in the floodplain. The average slope value remains 0.04 . The section is characterised by
slow current velocity (0.8 m/s).
More then 60 percent of the floodplain vegetation is represented by deciduous native forest, wetland
(mire) and open grass frequently accompanied by alluvial softwood forest, meadows and reeds.
Isolated mixed native forest and naturally unvegetated areas are present.
Eupotamon is the dominant aquatic habitat type and shows an average width of 1000 m. The percent
area of terrestrial habitats amounts to 60 percent of the entire eupotamon. Parapotamon,
plesiopotamon and the palaeopotamon types are frequently present.
The FPOM is the dominant biotic microhabitat in this section, frequently accompanied by
macrophytes, living parts of terrestrial plants, CPOM and debris. Tree trunks, branches and roots are
rarely present.

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Section Type 10: Danube Delta
(rkm 100: Isaccea ­ rkm 20 on Chilia arm, rkm 19 on Sulina arm and rkm 7 on Sf. Gheorghe arm)
The Danube Delta is Danube's "youngest" territory having three main water channels: Chilia/Kilia,
Sulina and Sf. Gheorghe, and numerous canals and floating islands ("plauri"). Close to the estuary the
three main branches are divided into numerous branches creating their own delta. At mean water
levels 60 percent of this area is covered by waters (90 percent at high levels). The shape of the delta is
triangular. A large variety of distinct lentic habitats is developed.
The valley form is plain floodplain and the channel form is diverse due to the complexity of the delta:
braided channel (braiding intensity 65 percent); split, sinuous and composite anabranching;
meandering channel (degree of sinuosity >1.26). The average width of the main channels is 450 m at
Chilia/Kilia, 400 m at Sulina and 450 m at Sf. Gheorghe. The mean depth of the three branches
amounts to 13 m. Slope values vary between 0.04 and 0.001 .
The dominant substrates are sand, mud, sludge, silt, loam and clay.
Multiple wood collections are present on the river bank; fallen trees are sporadic. At several reaches
the bank structure is abort. Lotic side arms and dead arms, cut off channels and oxbow lakes,
temporary side arms and standing water bodies fed by the tributaries constitute water bodies in the
floodplain. The average width of the floodplain is about 100 km.
This section is characterised by a medium current velocity of 0.7 m/s (Chilia/Kilia 0.7 m/s, Sulina
0.65 m/s, Sf. Gheorghe 0.68 m/s). Accumulations of sediment produce progression of the delta which
is permanently shaped by maritime currents.
The vegetation in this area is very complex, wetlands (mire) and reeds are dominant. Alluvial
hardwood forest, deciduous native forest and open grass land are frequently present. Alluvial softwood
forest, mixed native forest, meadow and naturally unvegetated areas are rare.
The percent area of terrestrial habitats represents 40 percent of the entire eupotamon. Para-, plesio-
and palaeopotamon show equal shares.
Living parts of terrestrial plants, FPOM and debris as biotic microhabitats are rare.

2. Reference conditions of the Danube River (biological elements)
The reference conditions of the Danube River have been defined in a very first draft. These will need
to be further developed and validated with other biological data.
The macroinvertebrate reference communities for the individual section types have mainly been
compiled from data on existing "reference" sites and from literature sources. Results of the Joint
Danube Survey (JDS, LITERÁTHY 2002) have been used, not regarding data on impounded sections. In
this survey more than 100 sampling sites have been investigated. As additional historical information
the huge taxa list for the whole Danube compiled by DUDICH (1967) has been used which goes back
beyond 1920. Many of the major hydromorphological alterations (dams, hydropower plants etc.) have
been established later than DUDICH's review.
The information given here provides a first overview of macroinvertebrate reference data.
The JDS data have been analysed by checking the presence/absence and abundances of species to
identify these taxa which are mainly occurring in certain sections.
Four groups of species have been distinguished:
· section type-specific species, occurring predominantly in a certain section type, e. g. the
Danube Delta (example: the Venus mussel Chamelea gallina)
· reach specific species, occurring predominantly in a certain region, e. g. Upper Danube River
(example: the snail Ancylus fluviatilis)
· Danube-specific species, predominantly restricted to the Danube (e. g. pontic fauna elements
like the snail Theodoxus danubialis)
· large river-specific species, occurring predominantly in large rivers, e. g. river Rhine (example:
the caddisfly Hydropsyche contubernalis).
To get a first impression of the macroinvertebrate fauna of a certain section type not only the `section
type-specific species' should be considered. Additionally, the taxa of the `reach specific species', the
`Danube specific species', and the `large river specific species' may occur.
The results of the analysis are presented in table 1.

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6

Table 1: Preliminary list of macroinvertebrate "reference species" for the section types and reaches of the Danube river. Species selected from data of the Joint Danube Survey
(2001) and from literature (DUDICH 1967, KUSEL-FETZMANN et al. 1998, RUSSEV et al. 1998). Large river type-specific species after SCHÖLL & HAYBACH (2001).

Section type 1
Section type 2
Section type 3
Section type 4
Section type 5
Section type 6
Section type 7
Section type 8
Section type 9
Section type 10
River km
100-20 Chilia arm.
2786 - 2581
2581 - 2225
2225 - 2001
2001 - 1789.5
1789.5 - 1497
1497 - 1075
1075 - 943
943 ­ 375.5
375.5 - 100
100-19 Sulina arm
(from ­ to)
100-7 Sf Gheorghe a
Eastern
Name of Upper course of
Western Alpine
Eastern Alpine
Lower Alpine
Hungarian
Pannonian Plain
Western Pontic
Iron Gate Danube
Wallachian
Danube Delta1
section
the Danube
Foothills Danube Foothills Danube Foothills Danube
Danube Bend
Danube
Danube
Danube
Dendrocoelum
Dugesia lugubris Ephoron virgo
Erpobdella
Ephoron virgo
Paludicella

Isochaetides
Mytilus
Angulus exiguus
lacteum
Gammarus
Heptagenia
nigricollis
Heptagenia flava articulata
michaelseni
galloprovincialis Anodonta cygnea
Gammarus
fossarum
coerulans
Ecdyonurus
Propappus volki
Ostrea
Chamelea gallina
fossarum
Gammarus pulex Brachyptera
aurantiacus
Lithoglyphus
sublamellosa
Mytilus
Baetis alpinus
Gammarus roeseli trisfasciata
Ephoron virgo
naticoides
Pseudoanodonta galloprovincialis
Baetis lutheri
Baetis alpinus
Isogenus nubecula Heptagenia flava
Dreissena
complanata
Ostrea
Caenis rivulorum Baetis fuscatus
Xantoperla apicalis Isogenus nubecula
polymorpha
sublamellosa
Ecdyonurus
Ephoron virgo
Ceraclea dissimilis Brachyptera
Corophium
Unio pictorum
torrentis
Heptagenia
C. annulicornis
trisfasciata
curvispinum
Gyraulus laevis
Dinocras
sulphurea
Hydropsyche
Xantoperla apicalis
Pontogammarus
Corophium
cephalotes
Potamanthus luteus contubernalis
Agapetus laniger
obesus
volutator
Leuctra fusca
Dinocras
Oecetis notata
Ceraclea
Pontogammarus
Hemimysis
Section Brychius elevatus cephalotes
Psychomyia pusilla annulicornis
sarsi
anomala
type-
Limnius volckmari Leuctra fusca
C. dissimilis
Jaera sarsi
Caenis horaria
specific Riolus subviolaceus Aphelocheirus
Hydropsyche
Dikerogammarus
species Micropterna
aestivalis
bulgaromanorum
haemobaphes
lateralis
Elmis maugetii
Hydropsyche
Hydropsyche
Polycentropus
Elmis rietscheli
contubernalis
bulgaromanorum
flavomaculatus
Hydropsyche
Psychomyia pusilla
Rhyacophila
contubernalis
dorsalis
Hydropsyche
Sericostoma
exocellata
flavicorne
Hydropsyche
Silo nigicornis
pellucidula-Gr.
Atherix ibis
Rhyacophila

dorsalis
Tinodes pallidulus
1 Within this section the Danube divides into the three main branches of the Danube Delta. Each arm also has transitional waters with the following limits: Chilia arm: rkm 20 ­ 0, Sulina arm: km 19 ­ 0, Sf.
Georghe arm: rkm 7 ­ 0.

Table 1 (continued)

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7


Section type 1
Section type 2
Section type 3
Section type 4
Section type 5
Section type 6
Section type 7
Section type 8
Section type 9
Section type 10
River km
100-20 Chilia arm.
2786 - 2581
2581 - 2225
2225 - 2001
2001 - 1789.5
1789.5 - 1497
1497 - 1075
1075 - 943
943 ­ 375.5
375.5 - 100
100-19 Sulina arm
(from ­ to)
100-7 Sf Gheorghe a
Eastern
Name of Upper course of
Western Alpine
Eastern Alpine
Lower Alpine
Hungarian
Pannonian Plain
Iron Gate
Western Pontic
Wallachian
Danube Delta1
section
the Danube
Foothills Danube Foothills Danube Foothills Danube
Danube Bend
Danube
Danube
Danube
Danube
Upper Danube reach
Middle Danube reach
Lower Danube reach
Ancylus fluviatilis
Brachycentrus subnubilus
Branchiura sowerbyi
Ephemera danica
Cordylophora caspia
Theodoxus fluviatilis
Baetis rhodani
Ceraclea dissimilis
Stylaria lacustris
Calopteryx splendens
Dugesia tigrina
Cardium edule
Reach Ephemera danica
Hydropsyche pellucidula
Cordylophora caspia
Gomphus flavipes
Branchiura sowerbyi
Unio pictorum
specific Heptagenia sulphurea
Psychomyia pusilla
Esperiana esperi
Ischnura elegans
Stylaria lacustris
Limnomysis benedeni
species Calopteryx splendens
Tinodes waeneri
Lymnaea stagnalis
Brachycentrus subnubilus
Esperiana esperi
Caenis horaria


Stagnicola palustris
Ferrissia wautieri
Caenis robusta
Theodoxus danubialis
Hydrobia ventrosa
Gomphus flavipes
Theodoxus fluviatilis
Lymnaea stagnalis
Ischnura elegans
Limnomysis benedemi
Stagnicola palustris
Theodoxus danubialis
Danube - Cordylophora caspia, Microcolpia daudebartii, Lithoglyphus naticoides, Theodoxus danubialis, Theodoxus transversalis, Viviparus acerosus, Dreissena polymorpha, Corophium curvispinum,
specific Dikerogammarus haemobaphes, Dikerogammarus villosus, Echinogammarus ischnus, Obesogammarus obesus, Jaera istri
species
Large Dina lineata, Dina punctata, Erpobdella nigricollis, Pisidium supinum, Sphaerium rivicola, Heptagenia flava, Gomphus flavipes, Gomphus vulgatissimus, Brychius elevatus, Limnius spec., Orectochilus
river-
villosus, Brachycentrus subnubilus, Ceraclea annulicornis, Ceraclea dissimilis, Hydropsyche bulgaromanorum, Hydroptila sparsa, Psychomyia pusilla
specific
species
1 Within this section the Danube divides into the three main branches of the Danube Delta. Each arm also has transitional waters with the following limits: Chilia arm: rkm 20 ­ 0, Sulina arm: km 19 ­ 0, Sf.
Georghe arm: rkm 7 ­ 0.

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Section type 1 (Upper course of the Danube) The macroinvertebrate fauna of this section type is
characterised by lithophilous species adapted to higher stream flow velocities. The macroinvertebrate
community can be regarded as `alpine-influenced'. Typical species are the amphipod Gammarus
fossarum, the mayflies Baetis alpinus, B. lutheri and Ecdyonurus torrentis, the stoneflies Dinocras
cephalotes and Leuctra fusca, the beetles Brychius elevatus and Limnius volckmari, the caddisflies
Polycentropus flavomaculatus, Rhyacophila dorsalis and Sericostoma flavicorne and the true fly
Atherix ibis.

Section type 2 (Western Alpine Foothills Danube). Occurrence of rhithral to epipotamal species,
which in part are transported into the main river from tributaries. Species composition provides in
conjunction with the high habitat diversity a very diverse aquatic fauna. Grazers dominate the
community, which also hosts many detritus and sediment feeders. Stone dwelling species are most
abundant, few fine sediment inhabitants occur as well. Typical species are the triclad Dugesia
lugubris, the Amphipods Gammarus pulex and Gammarus roeseli, the mayflies Potamanthus luteus,
Heptagenia sulphurea, and Baetis fuscatus, the water bug Aphelocheirus aestivalis,the beetles Elmis
maugetii and E. rietscheli, and the caddisflies Rhyacophila nubila, Hydropsyche pellucidula and
Tinodes pallidulus.

Section type 3 (Eastern Alpine Foothills Danube). Also this section type is mainly influenced by
prealpine features, typical species are mainly lithophilous species e. g. the mayfly Heptagenia
coerulans which are supplemented by other species of larger rivers like the mayfly Ephoron virgo and
a Danube-specific element, the flatworm Dendrocoelum romanodanubiale.

Section type 4 (Lower Alpine Foothills Danube). In this section type the morphological features
change to a lowland situation. Beside the caddisfly Psychomyia pusilla several taxa which are not
restricted to this section but live in all three sections of the upper Danube can be found, e. g. the sand-
living mayfly Ephemera danica, the dragonfly Calopteryx splendens and some caddisfly species
which are specific for larger rivers in general e. g. Brachycentrus subnubilus, Ceraclea dissimilis and
Tinodes waeneri.

The Section types 5 ­ 7 are difficult to differentiate in terms of macroinvertebrate community.
Specific for all three sections are taxa which inhabit finer substrate types (sand, mud) and
macrophytes, e. g. the aquatic earthworms (Oligochaeta) Stylaria lacustris and Branchiura sowerbyi,
the snails Esperiana (Fagotia) esperi, Stagnicola palustris, Lymnaea stagnalis, Theodoxus danubialis
and T. fluviatilis, the dragonflies Gomphus flavipes and Calopteryx splendens and Ischnura elegans.
The shrimp Limnomysis benedemi is an important brackish element which intruded into this area from
the Black Sea via the Danube Delta.
Section type-specific for Section type 5 (Hungarian Danube Bend) with its naturally constrained
channel form and gravelly or sandy substrates are the mayfly Heptagenia flava and the shrimp
Dikerogammarus villosus. In Section type 6 (Pannonian Plain Danube) with its finer substrates
(sand, loam and clay) and macrophytes e. g. the Hydrozoan Hydra spec. and Paludicella articula, a
river-specific Bryozoan, are to be found. In Section type 7 (Iron Gate Danube) with coarse blocks
and gravels in the breakthrough itself most lowland and large species rivers which are usually to be
found upstream and downstream of this section are lacking (most leeches, snails, shrimps,
dragonflies). There are no specific taxa which are restricted to this section type.
With Section type 8 (Western Pontic Danube) the Danube flows through the Romanian plain. This
section is completely located in ecoregion 12 (Pontic Province). Only a few species are characteristic
for this section, additionally a lot of species which are characteristic for the lower reach of the
Danube in general are to be found, e.g. the flatworm Dugesia tigrina, the mussel Unio pictorum, the
mayflies Caenis robusta and C. horaria and the snails Theodoxus danubialis and Ferrissia wautieri.
With Cardium edule, Cordylophora caspia and Hydrobia ventrosa mussels from the Black Sea are
intruding into these sections types.

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9

In Section type 9 (Eastern Wallachian Danube) the river is divided into several channels forming
extended wetland areas, the dominant substrates are sand or finer substrates. Additional species for
this section are the mussels Pseudanodonta complanata, Mytilus galloprovincalis and Ostrea
sublamellosa, which can also be found in Section type 10.

Section type 10 (Danube Delta) represents the Danube Delta where the Danube is divided into 3
major arms, the dominant substrates are of a very fine grain size (clay, loam). The share of brackish
species invading from the Black Sea increases, beside the species mentioned above there are several
species which seem to be restricted to this section type like the mussels Chamelea gallina, Donax
trunculus, and Angulus exiguus, and the shrimps Hemismysis anomala and Corophium volutator.
Typical insect species are the dragonflies Gomphus flavipes and Ischnura elegans and mayflies
Caenis horaria and C. robusta. C. robusta is tolerant against higher salinity and is to be found in
Delta areas in general (e. g. the Delta of the Odra on the Baltic Sea).

Danube-specific taxa: Beside the species mentioned above which are more or less specific for
certain section types or certain reaches of the Danube (Upper-, Middle-, Lower Danube) there are
several macroinvertebrate species which are to looked at as "Danube-specific". They have their main
distribution area within the Danube river (some of them are restricted to the Danube) e.g. the snails
Fagotia acicularis, Lithoglyphus naticoides, Theodoxus danubialis, the isopod Jaera istri, and the
shrimps Corophium curvispinum, Dikerogammarus haemobaphes and Echinogammarus ischnus.
According to SCHÖLL & HAYBACH (2001) several macroinvertebrates (most of them widespread and
common in the Danube River) can be regarded as typical species for large rivers in general. They
inhabite the different longitudinal zones of the Potamal, e.g. the leeches Dina punctata, D. lineata and
Erpobdella nigricollis, the mussels Pisidium supinum and Sphaerium rivicola, the dragonflies
Gomphus flavipes and G. vulgatissimus, the beetle Brychius elevatus and the caddisflies Hydroptila
sparsa, Psychomyia pusilla, Hydropsyche bulgaromanorum, Brachycentrus subnubilus, Ceraclea
anulicornis and C. dissimilis.
REFERENCES
DUDICH, E. (1967): Systematisches Verzeichnis der Tierwelt der Donau mit einer zusammenfassen-
den Erläuterung. In: Liepolt, R. (ed.): Limnologie der Donau ­ Eine monographische
Darstellung. Kapitel V: 4-69, Schweizerbart, Stuttgart.
KUSEL-FETZMANN, E., NAIDENOW, W. & B. RUSSEV (1998): Plankton und Benthos der Donau.
Ergebnisse der Donauforschung, Band 4. E.d. by Internationale Arbeitsgemeinschaft
Donauforschung, WUV, Wien.
LITERÁTHY, P., KOLLER-KREIMEL, V. & I. LISKA (eds.) (2002): Joint Danube Survey.- Technical
Report of the International Commission for the Protection of the Danube River, 261 pp.
RUSSEV, B., PETROVA, A., JANEVA, I. & S. ANDREEV (1998): Diversity of Zooplankton and
Zoobenthos in the Danube River, its tributaries, and adjacent water bodies. Bulgaria's
Biological Diversity: Conservation Status and Needs Assessment. Biodiversity Support
Program. Volumes I and II.
POTTGIESSER, T. & M. SOMMERHÄUSER (2004): Steckbriefe der bundesdeutschen Fließgewässer-
typen. - http://www.wasserblick.net/servlet/is/18727/?lang=de
SCHÖLL, F. & A. HAYBACH (2001): Bewertung von großen Fließgewässern mittels Potamon-Typie-
Index (PTI). Verfahrensbeschreibung und Anwendungsbeispiele. BfG-Mitteilungen Nr. 23.
Bundesanstalt für Gewässerkunde, Koblenz.

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