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Hydrobiologie (Fach) / UBRM (Lektion)

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• Which plants disappear first, after a falling carbon dioxide content? Fontinalis (Quellmoostyp) (use just the dissolved carbon dioxide)
• At which point of the aquatic food chain can you find the pike? He is a consumer, especially a „following-consumer“ (Carnivore) on the top (secondary consumer)
• Where can you find a stratified O2 saturation? In eutrophic (=nährstoffreichen) lakes (or just in lakes)
• Where does zooplankton live? In the midwater (Freiwasserkörper) (larvae on the bottom)
• How does the O2-content behave in potamals (Tieflandflüssen)? Low O2-content: mostly in polluted river sections, which are polluted by sewage and waste heat, also there is more during the day (because of photosynthesis)
• Which factors influence the density of water? Temperature, hydrostatic pressure, and salt content
• What does salinity mean? Salt content in ‰ in lakes (1 g salt in 1 l water ? 1 ‰ salinity)
• Which plants are not common or don´t exist in the Rhithral? Riverplankton or Phytoplankton, attached algae (periphyton), macrophytes
• What is the compensation level? The aphotic layer where production and degradation are balanced and approximately 1 % of surface radiation remains
• How do you call the unexposed layer in lakes? Aphotic layer or tropholytic zone
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• What are the specific features from metalimnion? It’s the area of the greatest temperature change (decrease), which occurs with increasing depth (=thermocline)
• Which circulation type possess most Austrian lakes? dimictic/ holomictic or dimictic/meromictic
• How did most Austrian lakes originate? by glacier movements in the ice age and exogenous forces
• What promotes summer stagnation? V horizontal demarcation of water layers because of excessive heating of top layer, wind can only mix epilimninon so hypolimnion remains cool and at the bottom of the lake
• What does the Secchi Disk show? visibility depth (secchi disk visibility depth times 2.5 = compensation level)
• What´s the name of the layer with digested sludge? (Faulschlamm) Sapropel, orginates on the bottom of eutroph – low in oxygen – waterbodies. anaerobic depletion causes hydrogen sulphide – and methanogenesis
• Where is „Endorheism“ present? in arid areas with low precipitation (Niederschlag) and high evaporation (Verdunstung) (evaporation > percipitation
• What does it depend on whether plankton float in the water? water temperature and density
• Which animal species are most frequent in mud (Schlammbank)? sludge worm (tubifex)Schlamm-Röhrenwürmer
• What does meromixis mean? partial mixing of water
• What does the “critical load“depend on? mean depth and retention period (of water)
• Which species lay “permanent eggs”? Crustacea (crayfish): Cladocera (water fleas), Copepoda (copepods) and Rotatoria (rotifers)
• Which characteristics do groundwater inhabitants have? No sight organs, no pigments, exposed to low seasonal fluctuation (over the year), daily to annual living conditions, reproduction and circadian rhythm ceased to exist
• Who lives in extreme habitats/ raised moors? Species that are very few in types but massive in population.
• What does “Henry`s law“ state? The solubility decreases along with increasing temperature and decreasing pressure. Cs = Ks x Pt (When the amount of gas dissolved in the water corresponds to the solution equilibrium, 100% saturation is reached)
• Which measure counteracts the eutrophication? Outside: the keeping away from wastewater, riparian protection stipes/buffer stripes (Uferschutzstreifen), less fertilisation. Inside: suction of the hypolimnion with pipes, insertion of organic suspended sediment
• Who (producer, consumer, decomposer) consumes the O2/oxygen content in the epilimnion? Consumer (and decomposer)
• Why is the temperature regulation of the water so good/acceptable? Because of the high specific heat
• In which part of the river are the most ramifications (Verzweigungen)? Delta (potamal = the lower reaches of a river, the part with the ramification is called furcation)
• How is O2/oxygen consumed at night? By consumption (breathing) and destruction (no primary production because you need sunlight for that)
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• Where is the allochthonous entry main carbonsource? In nutrient-poor Rhitral-waters
• What acts against Meromixxie? wind, tributary (Zufluss)
• What does the “Beer-Lambert Law“ define? As the depth increase, the light attenuation increases exponentially
• On what does the heat balance in running waters depend on? Volume, evaporation, condensation, the water mass distribution, the absorbed and reflected radiation and the air and ground heat exchange
• What is mainly responsible for warming up of lakes? The long-wave red radiation (which gets absorbed at the upper layers)
• How does the vertical heat exchange work in Lakes? With wind- dependent mixingprocesses
• When does homothermy occur? with uniform temperature
• In which zone does mixing not occur? Monimolimnion
• What is „Trophity“? The intensity of primary production
• What is „Saprobity“? the intensity of the degradation of organic matter
• Up to which area does primary production take place in standing waters? Up to the compensation level
• Where do Zoobenthos live? In the benthic region (lake bottom)
• What is important for the solubility of gases in water? The solubility reduces with rising temperature or sinking pressure (temperature, pressure and a specific solubility coefficient are important)
• The production in the pelagic region (mid water) occurs through…? Phytoplankton
• How is the sediment with brown mud called? Dy
• The model of the “Critical loading“ provides information about what? The “Critical loading“ from Vollenweider provides information on the load-carrying capacity and critical phosphorous exposure of lakes.
• At which level of the food-chain are “decomposers“ standing? At the end of the food-chain, but can also interfere with every other level
• The oxygen distribution in a lake shows a characteristic profile over the year. Where can you find an orthograde oxygen distribution? Orthograde in oligotrophic (nutrient-poor) lakes with little production
• Which communities are predominant in the rhithral rivers? In rhithral rivers, benthic invertebrates and fish are the predominant communities.
• What do you know about the O2 ration in rhithral rivers? In rhitual rivers the O2 entry from atmosphere is so vast that the O2 content is always close to the saturation value

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