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Hydrobiology (Fach) / VO I (Lektion)

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• Hydrobiology / Limnology =science of inland waters -biology of aquatic/water-related organisms (biotic components) -influencing chemical and physical enviromental factors (abiotic components)  -sub-discipline of ecology  -NOT dealing with sea/ocean -JUST inland water like stagnant water bodies (lakes) and running waters (streams, rivers)
• Natural river systems -in Europe almost all river systems are influenced by humans -in Austria: "cultural landscape rivers"   ->very much used and regulated due different reasons
• Major attributes of running waters / rivers -always in motion -open ecosystems -interaction / exchange with their surrounding area  -origin, course, development: tectonic / self-dynamic (like rivers running their way down a mountain) -longitudinal change of general conditions from origin to estuary (geology, altitude, topography of the terrain, gradient, morphology etc.) -runoff transport bed load / suspended solids / nutrients / organic material - the river transports a lot of material down the stream -habitat conditions are influenced by flow, substrate, structural compliation, O2-content, temperature, nutrient load etc. -strong longitudinal zoning of biocenosis as well as abiotic characteristics
• River Morphology - the shape of rivers from the source to the delta Source Zone  -sediment supply > deposition -straight  In between -braided or oscillating Transport Zone -sediment supply - deposition -anabranching In between -sinuous Deposition Zone -sediment mobilisation < deposition  -meandering Delta -anastomosing
• River Morphology Morphology = the shape of flowing waters; attempts to explain the processes that lead to their development and to describe the underlying causes The shaping of the riverbed is influenced by  -tectonics -bedrock (Grundgestein) -climate -vegetation ->these basic natural conditions result in runoff and sediment transport, which directly determine the channel geometry
• River type: straight (source zone) -generally straight channel, few bends -can be sinuous when the brook / river is forced to follow a very narrow valley -usually found in the headwaters and the source region -frequently occurs in narrow canyons and V-shaped valleys, whereby the riverbed is mostly formed by bedrock and large boulders -steep channel slope and high flow velocity, often cascade-style series of pools and riffles -the main current can oscillate slightly, permitting the creation of small-scale alternating gravel bars -constrained
• River type: braided (between source and transport zone) -divided into many branches and side channels, caused by high bedload transport rates (largely gravel) in conjunction with reduced slope -the rivers transport capacity does not suffice to transport all bedload immediately so that a part of the load is temporarily deposited and redistributed -often occurs after the inflow of bedload-abundant tributaries into a larger river with reduced slope -can occupy the entire valley floor -several subtypes depending on shift intensity:   ->bar-braided, if there are almost only unvegetated gravel bars   ->island-braided, if gravel bars are partly / largely overgrown with shrubs
• River type: oscillating (between source and transport zone) -sinuous single-bed river constrained by close valley sides  -the valley floor provides space for the river to oscillate and deviate from the centre valley line, forming cutbanks and slip-off slopes -changes in direction are usually caused by valley sides, alluvial cones or terrace systems -lesser bedload deposition in comparison to braided rivers; the transport capacity of the river is sufficient to carry the bedload further -wide slip-off banks with gravel bars in inner river bends and small islands in wider stretches
• River type: anabranching (transport zone) -mixed type of braided and sinuous-meandering channel forms -primarily found on larger rivers in wide valleys -typical in areas of glacial lakes, which formed right after the end of the last glacial period (Würm) and progressively filled with sediments during the Holocene -several river arms, which may be straight, braided, sinuous or meandering -single arms are usually separated by large vegetated islands, with the same terrain elevation as the adjacent floodplain -thereby - in contrast to braided river types - individual arms might behave as independent rivers
• River type: sinuous (between transport and deposition zone) -transitory type between braided/oscillating/anabranching rivers and meandering rivers -the course of the river is more sinuous but has no or only few meander bends -the proportion of course length and length of the valley axis (channel sinuosity) is between 1.1 and 1.5 -in wider river reaches, braiding with islands may occur locally 
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• River type: meandering (deposition zone) -strongly winding river course with a sinuosity greater than 1.5 -meander bends can 'wander' and might touch in doing so, thereby cutting of isolated oxbows and shortening the course of the river -lateral erosion causes steep outside banks (cutbanks), while the inside banks (point bars) show sediment deposition, creating new land surfaces -sand, silt and clay are dominant due to the low current velocity -incised meanders as a special variant: meanders cutting down into the bedrock result in a meandering form of the river valley
• River type: anastomosing (delta) -strongly branched with vegetated islands between channels -similar to anabranched, but much lower flow velocity -usually found in river deltas but also at the inflow into lakes or in basins with very low channel slope (inland delta) -dominance of finer sediments like sand, silt and clay Headwaters: erosion - deepening Middle courses: sediment turnover Lower courses: deposition / aggradation
• Flow regimes - the distribution of flow within a year nivo-pluvial regime (NIP): Opponitz (Ybbs) -max. April / Mai -sec. max. summer, autumn/winter -min. October pluvio-nival regime (PLN): Zwettl (Kamp) -max. March / April -sec. max summer (Jun, Jul) -min. autum  winterpluvial regime (WIP): Niederabsdorf (Zaya) -max. winter months (low evaporation) -sec. max. summer (not distinct) -min. later summer / autumn
• Flow regimes - the distribution of flow within a year nivo-pluvial regime (NIP): Opponitz (Ybbs) -max. April / Mai -sec. max. summer, autumn/winter -min. October ->influenced by snow (nivo) and rain (pluvial) regimes. When snow is melting, the highest force is between pluvio-nival regime (PLN): Zwettl (Kamp) -max. March / April -sec. max summer (Jun, Jul) -min. autum  winterpluvial regime (WIP): Niederabsdorf (Zaya) -max. winter months (low evaporation) -sec. max. summer (not distinct) -min. later summer / autumn ->no snow left - rain events during winter
• Transport capacity (Qc) and sediment supply (Qs) Cascade: highest Qc, lowest Qs Step-pool: high Qc, low Qs Plane-bed: Qc = Qs Pool-riffle: low Qc, high Qs Dune-ripple: lowst Qc, highest Qs ->sediment transport and sediment supply are in balance (but dynamic)!
• Geology: Influences on morphology Granite "Bohemian mountains" vs. Limestone Pre-Alps Granite: higher grain size Limestone: lower grain size
• The riverbed as habitat -dynamic changes -turnovers are vital -habitat for pioneers Substrate = as habitat named choritop
• Ther riverbed as habitat: the hyporheic zone =transition area between river and groundwater -golden algae (hydrurus foetidus) -microhabitats
• Interstitial spawners Egg development: 3-18 weeks -Bachforelle -Äsche -Huchen -Seeforelle -Lachs
• Substrate spawners Egg development: 1-2 weeks -Barbe -Aitel -Nase -Frauennerfling -Nerfling -Schied
• Water temperature and oxygen -organismic oxygen demand increases with temperature -temperature dependent oxygen saturation decreases with higher temperature -higher biological and chemical oxygen consumption in lower course
• Water temperature Danube: very stable ->large and stable waterbody Melk river: sinuous ->slightly shaded small river Lunzer Seebach: little higher from 12 to 18 ->well shaded mountain stream
• Water temperature - example brown trout Development of fish larvae - from the fertilized egg to the free ranging stages - is strictly temperature dependent Egg deposition -November: 3°C, 80 days -Febuary: 5°C, 40 days -March: 8°C, 50 days
• Trout (Forelle) Epirithral / troutregion -slope: >3% -temperature max.: <18°C -mean width: <15m -distance from source: <40 km -biggest substrate
• Grayling (Äsche) Hyporithral / graylingregion -slope: >1% -temperature max.: <20°C -mean width: <70m -distance from source: <100 km -big substrate
• Barbel (Bartel) Epipotamal / barbelregion -slope: >0,7% -temperature max.: <22°C -mean width: <200m -distance from source: <300 km -tiny substrate
• Bream (Brasse) Metapotamal / breamregion -slope: >0,3% -temperature max.: <24°C -mean width: <600m -distance from source: <600km -tiniest substrate
• Alluvial areas / floodplains -from the headwaters towards the lower course, the floodplain zone increases in importance and usually remains closely linked to the "active channel" -meandering lowland rivers have an alluvial zone that extends far into the area ("floodplain"), with old waters that are in part "optically" clearly seperated from the "active channel" -the diversity of water body types and species in the floodplain zone increases significantly towards the lower course of a river catchment

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