Stream and River Ecosystems Flashcards
What are characteristics of streams?
-Orders 1 - 6
-Rapid flow
-Shallow
-Average temp <20 degrees
-Low decomposition rates
-Accumulates allochthonous material
-Oxygen saturated waters
What are characteristics of rivers?
-Order >6
-Deep waters
-Muddy sediments
-Primary production plays a major role
-Rapid currents
-Periphyton forms the main diet of grazing benthic inverts
-Autochthonous primary production dominates
What is the river habitat templet theory?
Organisms are adapted to aspects of habitat, such that traits of organisms reflect features of the environment (Townsend and Hildrew 1994)
What is the relationship of habitat and evolution?
Habitat provides the templet on which evolution forges characteristic life history strategies
-Individual taxa are adapted to specific range of habitat conditions
-Direct link of biotic traits and physicochemical environment
How are key habitat needs identified?
-Environmental variables that best correlate with its distribution and abundance
What are some key adaptations for benthic invertebrates?
-Dorsoventrally flat
-Streamlining
-Reduced projecting structures
-Suckers
-Friction pads
What advantage is there for being dorsoventrally flat?
Allows crawling in slow current boundary layer on substrate
eg. gomphidae, glossosoma
What advantage is there to streamlining?
Fusiform body minimises resistance to current
eg. diptera
Relatively rare body form
What is the advantage of reduced projecting structures?
Reduces resistance to current
eg. baetis
What is the advantage of suckers?
Attach to smooth surfaces
eg. diptera
What is the advantage of friction pads?
Increased contact reduces chances of being dislodged
eg. coleoptera
How do dissolved inorganic nutrients enter streams?
From upstream, groundwater and surface runnoff and atmospheric inputs
Do streams or rivers have higher nutrient concentrations?
Streams have very small concentrations while rivers are rich in accumulated nutrients
Why are inorganic nutrients important?
Nutrients in this form are bioavailable
What is the temperature range for temperate rivers?
0 - 25 degrees
Are there seasonal changes in water temperature?
Yes, they closely follow seasonal trends in mean monthly air temperature
What happens to rocky streams in relation to temperature?
-Lose more heat compared to gravelly streams
-Daily temperature variations of up to 10 degrees rocky unshaded areas
Does the temperature fall below 0 in temperature rivers?
No
What does riparian vegetation affect temperature wise?
Important role in regulating stream temperature especially when stream widths <10m
-Buffer strips of 30m reduce back side erosion, preventing large temperature increases and preserving benthos
Why is temperature so important?
-Determines metabolic rate of organisms
-Biotic distribution along length of a river
-Successful biotic interactions
What process are affected by temperature?
Species competition, biological rates, leaf breakdown, nutrient uptake, biological production
What varies with temperature?
Seasonally and diurnally
Climate
Streamside vegetation
Groundwater inputs
What are the direct impact of flow/discharge on organisms?
-Eroded from a substrate
-Energy reserves are depleted, work to maintain position in the water
What is an indirect impact of flow/discharge on organisms?
Delivery of food particles, nutrients or dissolved gases influencing their metabolism and growth
Ecological processes affect by flow?
Dispersal (removal of wastes)
Habitat use (influence species occupying a site)
Resource acquisition (delivery of nutrients and gases)
Competition
Predator-prey interactions
