What are the 6 major stressors on aquatic systems?
1) Nutrient loading 2) Toxic materials and metals
3) Acid precipitation 4) Invasive species
5) Climate Change 6) Harvest of aquatic resources
How does climate change affect lakes?
- more extreme weather events, particularly in summer
- lower annual precipitation (possibly)
- changing temperature (ice formation, melting, duration, timing)
- temp affects turnover and stratification
How do humans affect lakes?
Harvest of aquatic resources:
- fishing--> removal of biomass leaves less overall
- hydroelectric power. Reservoirs alter lake functioning.
- Unique temperature-density relationship
- High specific heat and heat capacity
- hydrogen bonds
What is the significance of water's polarity?
The hydrogen bonds make water "sticky"
What is the significant of water's specific heat?
- only substance that exists in all 3 states under normal conditions
- can take in or give off a lot of heat with little change in temperature
- high thermal resistance makes aquatic environments stable for organisms
Why can water take in or give off a lot of heat without changing temperature?
It has high thermal resistance due to its high specific heat. Water has a high latent heat of fusion/melting and latent heat of vaporization/condensation which means that it takes in or gives off a lot of energy before changing state.
Why is the thermal stability of water important to aquatic organisms?
1) Allows them time to adapt to changing conditions/temperatures.
2) Allows life to exist at a wide range of temperatures
Why does ice float?
Why is this important to lakes?
Because water is less dense as a solid than as a liquid.
Because it means that ice forms on the top, allowing organisms to live underneath.
How does salt affect water?
Why do we add salt to boiling water or to icy roads?
It lowers both the boiling point and the freezing point of water.
This means that putting salt on icy roads melts the ice (to a point) because it allows water to stay a liquid at lower temperatures than normal.
Describe the viscosity of water and why it is the way it is.
Water is moderately viscous because its hydrogen bonds cause the molecules to "stick" to one another.
Describe the solvent properties of water.
Water is a universal, inert solvent.
This means that it does not change the solute in any way, and that organisms in the water can use the solutes without having to change them.
Describe the surface tension of water and the reasoning behind it.
Liquid water has a very high surface tension (second only to liquid mercury) because of COHESION, which is the "stickiness" of water molecules due to hydrogen bonding.
What is the cohesion-adhesion relationship of hydrophobic surfaces?
Cohesion > adhesion
The water molecules stick to each other more than the surface and appear as beads on the surface.
What is the cohesion-adhesion relationship of hydrophilic surfaces?
adhesion > cohesion
The water molecules are attracted to the surface and the surface appears wet.
How are tectonic basins formed?
by the movement of the Earth's crust
Where do tectonic basins occur?
All over the surface of the world where cracking occurs.
What is parallel cracking?
a way of forming lakes where two pieces of land pull apart and leave a long deep basin in the middle (parallel shores). Lake is long and narrow with very steep sides.
Describe Lake Baikal...location, characteristics, morphometry, formation, special features.
Siberia. Rift lake. Parallel cracking.
Earth's oldest (20-25 million years old), deepest, (one of) clearest lake
> 80% of species are endemic. - ultraoligotrophic
Why would Lake Baikal have so many endemic species?
Very high elevation -- little way for species to enter
The lake is extremely old -- evolution