Lecture 1; Adaptations, movements and colonization Flashcards
Direct colonization
direct movement of species from organisms evolved in oceans moving into freshwaters
Secondary colonization
Terrestrial/land ancestors evolved into freshwater organisms
examples of direct colonized organisms
- crustaceas, molluscs and fish
examples of secondary colonized organisms
- insect groups, mollusca
some adaptations for respiration
- air breathing
- plastron
- pigments
- tracheal gills
adaptations for coping with flow
- streamlines shape/body parts ‘hydrofoils’
- suckers
- modified gills
- modified feeding appendages
- hook and silk
Adaptations related to coping with drought and food availability
- life cycle traits
- niche separation
- dormant stages; diapause
leaves on Nuphar lutear ‘Brandy Bottle’
- large flat leaves on water surface
- under water; thinner leaves
Adaptation of leaves on nuphar lutear
- under water leaves; fold up and reduce resistance when there is an increase In flow velocity
colonization
a process where organism disperse, come into contact with a new habitats
choose an area suited to
What time of day/year are organisms more likely to move upstream?
at night and summer
Macroinvertebrate drift
movement downstream of invertebrates either involuntarily due to disturbance or volunatirly
3 types of drift
- catastrophic
behavioural
Constant
catastrophic drift
due to unfavourable conditions, may be washed into the flow,
Behavioural drift
some form of diurnal periodicity involved
actively enter the drift by choice
Constant drift
Occurring all the time at low levels
why drift at night?
avoid predation by fish
4 adaptive advantages of drift
- colonization of downstream areas and of disturbed patches
- when food is scarce
- avoid unfavourable condition-pollutants, temperature, ice, floods, drought, low DO
- avoid predation
Definition of hyporheic
- Saturated interstices beneath the stream bed and into the stream banks that contains some portion of channel water or surface water infiltration
Hyporheos
community which lives in the hyporheic zone
temperature in hyporheic zone
less variation diurnally and seasonally
light in hyporheic zone
light doesn’t penetrate > 4.5 X grain size of sediment
Current velocity in hyporheic zone
reduced when water infiltrates
DO in hyporheic zone
declines with decreasing depth ( at 30cm deep, can be 5% of that at surface)
