Stream and River Ecosystems

Question 1

What are characteristics of streams?

Answer 1

-Orders 1 - 6
-Rapid flow
-Shallow
-Average temp <20 degrees
-Low decomposition rates
-Accumulates allochthonous material
-Oxygen saturated waters

Question 2

What are characteristics of rivers?

Answer 2

-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

Question 3

What is the river habitat templet theory?

Answer 3

Organisms are adapted to aspects of habitat, such that traits of organisms reflect features of the environment (Townsend and Hildrew 1994)

Question 4

What is the relationship of habitat and evolution?

Answer 4

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

Question 5

How are key habitat needs identified?

Answer 5

-Environmental variables that best correlate with its distribution and abundance

Question 6

What are some key adaptations for benthic invertebrates?

Answer 6

-Dorsoventrally flat
-Streamlining
-Reduced projecting structures
-Suckers
-Friction pads

Question 7

What advantage is there for being dorsoventrally flat?

Answer 7

Allows crawling in slow current boundary layer on substrate
eg. gomphidae, glossosoma

Question 8

What advantage is there to streamlining?

Answer 8

Fusiform body minimises resistance to current
eg. diptera
Relatively rare body form

Question 9

What is the advantage of reduced projecting structures?

Answer 9

Reduces resistance to current
eg. baetis

Question 10

What is the advantage of suckers?

Answer 10

Attach to smooth surfaces
eg. diptera

Question 11

What is the advantage of friction pads?

Answer 11

Increased contact reduces chances of being dislodged
eg. coleoptera

Question 12

How do dissolved inorganic nutrients enter streams?

Answer 12

From upstream, groundwater and surface runnoff and atmospheric inputs

Question 13

Do streams or rivers have higher nutrient concentrations?

Answer 13

Streams have very small concentrations while rivers are rich in accumulated nutrients

Question 14

Why are inorganic nutrients important?

Answer 14

Nutrients in this form are bioavailable

Question 15

What is the temperature range for temperate rivers?

Answer 15

0 - 25 degrees

Question 16

Are there seasonal changes in water temperature?

Answer 16

Yes, they closely follow seasonal trends in mean monthly air temperature

Question 17

What happens to rocky streams in relation to temperature?

Answer 17

-Lose more heat compared to gravelly streams
-Daily temperature variations of up to 10 degrees rocky unshaded areas

Question 18

Does the temperature fall below 0 in temperature rivers?

Answer 18

No

Question 19

What does riparian vegetation affect temperature wise?

Answer 19

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

Question 20

Why is temperature so important?

Answer 20

-Determines metabolic rate of organisms
-Biotic distribution along length of a river
-Successful biotic interactions

Question 21

What process are affected by temperature?

Answer 21

Species competition, biological rates, leaf breakdown, nutrient uptake, biological production

Question 22

What varies with temperature?

Answer 22

Seasonally and diurnally
Climate
Streamside vegetation
Groundwater inputs

Question 23

What are the direct impact of flow/discharge on organisms?

Answer 23

-Eroded from a substrate
-Energy reserves are depleted, work to maintain position in the water

Question 24

What is an indirect impact of flow/discharge on organisms?

Answer 24

Delivery of food particles, nutrients or dissolved gases influencing their metabolism and growth

Question 25

Ecological processes affect by flow?

Answer 25

Dispersal (removal of wastes)
Habitat use (influence species occupying a site)
Resource acquisition (delivery of nutrients and gases)
Competition
Predator-prey interactions