Flashcards in Lecture 8 Notes Deck (18):
Past studies of fresh water environments
What are 7 interspecific differences in fundamental niches?
2. Nutrient status
5. Water depth
7. Ice cover
What are 4 examples of diatoms that effect fundamental niches?
- epiphytic and epilithic
3. Rheophilic (streams)
4. Cryophilic (ice)
Why are diatoms useful paleo-indicators? (4)
1. They are abundant in aquatic ecosystems
- abundant in lakes and marine sediment as fossils
2. Well preserved due to siliceous frustule that is resistant to decay
3. Readily identifiable
4. Short generation times
- response to environmental change is rapid
- pollen takes a while to respond to change
Is an organism whose presence, absence of abundance reflects a specific environmental condition
- can signal a change in the biological condition of a particular ecosystem
Relate modern communities to environmental
What do you need in order to create a transfer function?
Modern environmental data and abundances of taxa
How do you solve for past environments?
By applying function to fossil assemblages
What are 5 things that occur in a large lake at low elevation?
1. Productivity is low
2. Sediments are inorganic
3. Hard to carbon date
4. Poor chronological control
5. Slow sedimentation rate
What do you need in order to have moss grow?
A longer arctic ice free space
What is 1 thing that occurs in a small lake a low elevation?
Slow sedimentation rate
What are 2 things that occur in a small lake a higher elevation?
1. Slow sedimentation rate
- no change for 8,000 years
2. Massive explode of diversity of species right at the top
What does species turnover in arctic diatom assemblages do?
They increase littoral, epiphytic taxa that require longer ice- free seasons
What are transfer functions based on? (2)
1. Modern diatom communities
2. Measurements of environment variables
Why do most communities vary?
Because of the differences in lakes pH and phosphorus
What does a change in diatoms tell us?
That there is a change in pH and P
- cant argue then that changes in pH and P causes change in diatoms
- this is why it is beneficial to have multiple proxies
1. Little nutrients
2. O2 is rich on the bottom waters
- because it is not getting used up from decomposition of materials getting in the water
3. Occurs in clear cold water