Lecture 12 Flashcards
What are the salinity and trophic ranges of Antarctic lakes?
Range from hyper saline to freshwater.
Range from oligotrophic to mesotrophic
What is missing from the Antarctic lake food web?
Top predators (vertebrates)
What is a dry valley lake?
Lakes that are permanently covered in an upper layer of ice that never thaws
What percentage of surface photosynthetically active radiation (par) reaches the water column? Why is it this number?
Four percent. Humid material settles atop of the ice, significantly reducing the ability of light to penetrate.
What is the stratification in dry valley lakes? Why?
All lakes meromictic (permanently stratified), due to nutrient availability and NOT temperature
Why do dry valley lakes have instead of a thermocline?
A chemocline
How to cladocerans and rotifers in dry valley lakes reproduce?
ALWAYS by parthenogenesis
What is mixotropy?
The ability of an organism to photosynthesise and eat bacterial prey
In which organism does mixotropy? occur?
Occurs in flagellates algae and flagellated heterotrophic Protozoa
Explain mixotropy in autotrophs and heterotrophs.
Autotrophs preferentially gain energy by photosynthesis, but will become heterotrophs when light is limiting.
Prey limitations cause heterotrophs to become autotrophs
How do algae stay active in the polar night (no sunlight)
They undergo mixotropy, and feed on bacteria
Explain subgalcial lake features
They are situated below 2.5 miles of ice, and have an insulating upper layer of light locking in their geothermal heat. No photosynthetic organisms are though to be present, as light never penetrates
