Lecture 6 - RH Flashcards
What makes water life different to terrestrial life?
Low oxygen conditions under water
Pressure at depth
Animals are suspended in the medium rather than being on the ground
Easier dispersal of eggs/offspring than terrestrial ecosystems
Animals are surrounded by food and just have to strain the medium
Aquatic habitat is more diverse than the terrestrial habitat
Primary producers are smaller and more mobile in aquatic habitats compared to terrestrial
More sessile invertebrate animals in aquatic habitats
More complex food webs in aquatic habitats
What is water cycling like over land?
Precipitation > Evaporation and so excess precipitation is carried into the oceans by ground-water runoff.
Most precipitation over land comes from evaporation of ocean.
Evapotranspiration is more than evaporation of surface water highlighting the importance of plants for water balance
What has human activity done to the water balance and distribution?
Altered river flows by dams
Land clearing and changes in drainage patters
Redirection of water for irrigation, consumption, and industry
Exploitation of ground water reserves
Anthropogenic climate change, regional alterations of precipitation and evaporation
What is limnology?
The study of lakes, rivers, and wetlands.
OR
The study of the structural and functional relationships of inland waters and organisms as they are affected by their physical , chemical, and biotic environments.
What are lotic systems?
Flowing-water systems
What are lentic systems?
Standing-water systems
What are wetland systems?
Transition zone between terrestrial and aquatic systems. Soil is waterlogged or submerged at least part of the year typically having at least some rooted aquatic vegetation.
What is a catchment?
Area of land drained by a river system
Also known as a watershed or drainage basin
How does water move through a catchment?
Can run as surface runoff into a water body.
Different zones underground
What is an aquifer?
Subterranian body of water that is flowing
How long ago was Australia’s Great Artesian aquifer deposited?
300k years ago
What has the Great Artesian Basin used for?
Water extracted is used for irrigation, drinking, and industry. (100 times the volume of Sydney)
Why is it important to preserve confined aquifers?
Confined aquifers contain very old water that is non-renewable and is not part of the active hydrological cycle
What is the lag time in regards to river flow through a catchment?
Time taken for surface water to move into the stream moving towards the catchment
What does the absence of riparian vegetation do to the rate of water accumulation in streams moving towards catchments?
Water moves more freely with less riparian vegetation presence and so it accumulates quicker after heavy rains.
Rivers return to base flow more quickly
What does the presence of riparian vegetation do to the flow of water in streams?
Vegetation promotes infiltration of water under the soil via entrapment under litter and root channels in soil
Stabilizes soil and reduces erosion
Produces a way for water to evaporate again via transpiration reducing run off
What does forest clearcutting do to catchments?
Removes barrier to ultraviolet light
prevents the moderation of heating and cooling of the ground
Nutrient uptake from soil is diminished (nutrients are flushed out by water into catchment)
What are the zones found in lakes?
Littoral which is near the entry into the lake
Limnetic which is the surface layer of water where photosynthesis is possible
Profundal layer is deep under the limnetic zone and is dark and photosynthesis is not possible
What are the subdivisions of the limnetic and profundal zone of water?
Limnetic layer contains:
Epilimnion: surface layer that is mixed by wind - or temperature - driven currents
Profundal layer contains:
Metalimnion: Region of thermocline transition between epilimnion and the hypolimnion
Hypolimnion: the lowest layer of water where it is dark, cold, and relatively stagnant
What are pellagic and benthic organisms?
Pellagic: live suspended in the water
Benthic: Live on the floor of the ocean/lake
Where is the water’s maximum density?
4 the grease
What happens to waters density with salt concentration?
The more salty it is the more dense it is
Where is the thermocline located?
Under the point where wind mixing is taking place
What is the difference between holomixis and meromixis?
Holomixis refers to complete mixing to the bottom
Meromixis refers to incomplete mixing not reaching to the bottom
What is seasonal overturn?
Changes in temperature alter the density of different parts of the water.
In Spring, ice melts and surface water warms up. As a result, the water sinks mixing the water and creating an isothermal water column.
In Autumn, the surface water cools and stratification breaks down and surface water cools towards 4 degrees becoming more dense.
Why is seasonal overturn important?
It stimulates plankton growth by injecting nutrients back into surface water.
Amount and timing of biological production and decomposition is influenced by circulation regime
What does “dimictic cycle” refer to?
Semi-annual overturn
What happens in a warm monomictic lake?
water undergoes holomixis only once and is usually found in warm temperate climates. This happens because water never goes to 4 degrees or below meaning the water doesn’t need to warm back up to undergo another seasonal overturn.
