Lecture 34. Freshwater Ecosystems: Rivers and Lakes Flashcards
What percentage of worlds fish species live in rivers ?
40%
How long does it take for a river to renew its self ?
5-20 days
What is the function of rivers ?
Link ground water and lakes by estuaries to sea
How are rivers formed ?
- Springs
- Snow fed rivers
- Glacial rivers
- Bog fed rivers
What is the river continum concept ?
Calssifys rivers by size, substrate, abiotic factors and biota
What are the classifications of rivers ?
- Headwater (1st to 3rd order)
- Mid reaches (4th to 6th order)
- Large rivers (6+ order)
What happens to flow speed as river order increases ?
FLow speed decreases
How would you describe the light penetration of rivers as river order increases ?
Positive curve ie. n-shaped
What can effect light penetration ?
- Overshadowed by trees
3. High turbulence
How would you describe temperature as river order increases ?
Positive curve - n-shaped (steeper slope)
What are some abiotic factors affecting the river continum concept ?
- Flow speed
- Light penetration
- Temperature fluctuation
- Nutrients
- Organic matter
What is periphyton ?
Organic matter produced in river itself
What are the different types of organic matter in rivers ?
- Terrestrial coarse detritus
- Periphyton
- Macrophytes
- Phytoplankton
- Fine detritus particles
- Upstream accrual
What sort of animals live in each area of the river ?
- Shredders
- Fine particle collectors
- Periphyton grazers
- Benthic filter feeders
- Sediment burrowers
- Water column filter feeders
Where is biodiversity highest in rivers ?
Middle reaches
Why is the biodiversity in rivers highest in middle regions ?
- Temperature fluctuations
- Energy source
- Most light available
What are shredders ?
Large organic matter into smaller pieces
What are collectors ?
Small dead organic matter
What are grazers ?
Scraping algae or filtering
What are threats to river systems ?
- Dams block migration routes and disrupt habitat
- Overexploitation
- Global warming, floods, pollution and drought
- Eutrophication from agricultural and urban areas
- Water withdrawal for human use
- Invasion of exotic species can harm native animals and plants
What are some stressors to rivers in farming ?
- Dissolved nutrients like nitrogen and phosphorous increase
- Deposition of fine sediments increase - disturbed by cattle
- Water temperature increases due to loss of shading
- Water input decreases - as water extracted for irrigation
- Chemical pollutants increases - pesticides and herbicides
When does the macroinvertebrate decrease ?
- Increasing nutrient addition
2. Increasing presence of fine sediment
What does the decrease in macroinvertebrate result in ?
Reduce in stream health
Which is more influential fine sediments or nutrients ?
Sediments
