Aquatic environments Flashcards
Lecture 2
Water is not static, explain.
Water moves from the air to earth and back in hydrologic or water cycles.
Surface runoff doesn’t go into the environment system it flows into rivers.
Why is water very stable?
Has a high specific heat = 1
needs a lot of heat to change the temp
1 calorie needed to raise the water temp by 1degree C
Which reduces drastic heat change in temp:
* acts as a buffer
* important for thermoregulation within living organisms
Explain the structutre of water?
In liquid and solid form
Denser than air.
Ice is less dense but takes up more space - ice floats, due to hyrdogen bond lattice. Insulates water bodies so organisms don’t freeze to death.
Water in liquid form has a hydrogen bond network that can freely move.
Explain viscosity.
Water molecules bind to each other strongly (hydrogen bonds)
High resistance, which makes water difficult to move through > streamlining.
What is buoyancy ?
combination of density and viscosity.
upward face of water acts on the less dense object
most aquatic animals are neutrally buoyant:
* upward force cancels out the force of gravity
* reduces energy needed to maintain position in water
* support to body means they need less strong structural support.
Pressure
at sea level = 1 atm
Under water surface pressure increase with 1atm with every 10m
sea bed = 20-1000 atm
(organisms at extreme depths need to adapt to survive at such high pressures)
Light
light striking the surface of water may be
* reflected or
* absorbed or
* scattered
Light decreases with depth
influecnes the 1 degree production of where organisms can live.
What changes with the depth?
Heat is distributed down as wind mixes surface water.
Minimum effects of solar radiation & mixing of surface water.
Different densities keep warm and cold water separate.
oxygen
Oxygen (and carbon dioxide) diffuse from the atmosphere into surface waters.
The rate of diffusion depends on the diffusion gradient & the solubility of oxygen which is affected by:
* Temperature
* Salinity
* Pressure
The colder the temp the greater the solubility
as pressure increases oxygen increases.
Water functions as a solvent
All water eventually ends up in the ocean
Oceans have more solutes than freshwater
* Salinity
* Freshwater = 0.065 ‰ to 0.30 ‰
* Open sea = 35 ‰
* Na & Cl most soluble salts
Salinity measured as parts per thousand (ppt/ ‰) or g solute per kg water
How does acidity have a widespread influence on aquatic environments?
The pH of natural waters = 2 to 12 (seawater = 7.5 – 8.4.)
pH depends on how much CO2 enters system
* CO2 + H2O ↔ H2CO3 (carbonic acid)
* H2CO3 ↔ HCO3– (bicarbonate) + H+ (hydrogen ion)
* HCO3– ↔ H+ + CO32– (carbonate)
- In freshwater systems, nature of sediment influences pH.
The pH of aquatic environments influences distribution and abundance of organisms.
Low pH has direct effects:
* Physiological processes
* Decalcification (corals, molluscs, crustaceans, coralline algae)
* Reproduction inhibited at pH <4.5
Low pH has indirect effects:
* Increases concentration of toxic metals
* Aluminium dissolves as pH decreases
How Do Water Movements Shape Freshwater Environments?
Fast moving rivers:
* Beds
* O2 concentration
* Decaying matter
* Temperature
* Stony
* High
* Little
* Lower
Slow Moving rivers:
* Silty
* Lower
* High
* Higher
How Does Water Movements Shape Marine Environments?
Waves generated by wind
Coastal regions
- Waves bring O2, food & sediment etc. to shore
- Impact depends
- on whether it is a rocky or sandy shore
- Degree of wave action
- May be sheltered or exposed
- Influences species composition
- Mobile or sedentary spp?
- Predators or filter feeders?
Explain upwelling.
winds drive surface waters to shore.
deep nutrient rich water is welled up to replace the water and feuls plankton blooms
where cold water meets warmer oceanic water it sinks beneath it, and rapid jet flows towards the equator.
below warmer oceanic water lies sluggish poleward undercurrent.
What is the intertidal zone?
Region between high and low tide.
harsh conditions
organisms need to be able to withstand aquatic and terrestrial environments.
