Stressors on Freshwater Ecosystems - T

Question 1

Animal species richness

Answer 1

%species / % area
freshwater has the most by far

Question 2

extinction rate

Answer 2

rate = 1 - proportion of species that survive over that period
raised to 1/time period

Question 3

background extinction rate of freshwater fish

Answer 3

3 million years
1 extinction per 3 million fish species per year = 0.33 E / MSY

much much higher recently (1000%)

Question 4

river channelization effect (3)

Answer 4

reduced habitat complexity, reduced biodiversity, more generalist species

Question 5

river impoundment (dams)

Answer 5

habitat fragmentation, loss of natural flow, altered water quality
2/3 of world’s large rivers affected by dams

Question 6

environmental impacts of large dams

Answer 6

flow waters converted to still waters
lower oxygen, higher turbidity and sedimentation and temp stratification
fish migration is blocked
downstream flow is altered, reduced water temp, messed up stream bed
releases GHGs and adds mecury to foodwebs

Question 7

effects of water removal and diversion (2)

Answer 7

altered flow regimes, loss of habitat

Question 8

watershed alteration

Answer 8

deforestation, urban development, ag)
altered nutrient inputs, flash flood, increased delivery of sediments + contamination, invasions

Question 9

organic pollution
causes and effects

Answer 9

(nutrients from agri, sewage)
increased productivity –> algal blooms, altered water quality

Question 10

toxin effects

(2)

Answer 10

food chain effects (more concentrated in higher trophic levels), loss of vulnerable species

Question 11

acidification effects (2)

Answer 11

altered water quality (low calcium, pH), molluscs and crabs most heavily impacted (thins out shells)

Question 12

temperature changes

Answer 12

altered Et + flow regimes, change in water quality, species range shifts

Question 13

precipitation changes

Answer 13

altered flow regimes, greater extremes

Question 14

biological invasion local and global scale effects

2 for each

Answer 14

local scale: reduced native populations, net gain or loss of species richness
global scale: loss of species richness, increased biotic homogenization

Question 15

2 ecological consequences of extinctions

Answer 15

extinctions reduce ecosystem functioning and efficiency, more diversity uses resources more efficiently, better protection

a diverse group of species is insurance in a fluctuating environment, all jobs will be performed under varying conditions
species function optimally at different parameters