L5 - Ecological features of freshwater ecosystems

Question 1

what are the 3 primary ecological zones in lakes based on location?

Answer 1

• littoral - water edges
• central/ pelagic - open surface water
• benthic - bottom

Question 2

how is light availability in lakes catergorized

Answer 2

INTO photic - light-penetrated)

APHOTIC = light deprived zones

Question 3

what are the 3 stratification layers in a deep lake

Answer 3

1. Epliminion = surface layer with circulation and warm water
2. Metalimnion = middle layer with temperature gradient
3. Hypolimnion = deep, cold and oxygen-depleted layer

Question 4

what are the productivity categories of lakes?

Answer 4

1. Oligotrophic = low nutrients, clear water and low productivity
2. Mesotrophic = moderate nutrients and productivity
3. Eutrophic = high nutrients, high productivity and possible algal blooms

Question 5

what defines the biological communities in lake zones?

Answer 5

LITTORAL ZONE = autotrophs, macrophytes, periphytes, epiphytes and biofilms

PELAGIC ZONES = neuston, phytoplankton and zooplankton

BENTHIC ZONE = heterotrophic bacteria, protozoa and detritivores

Question 6

what are the key features of a shallow unstratified lake

Answer 6

photic zone extends through the water column

limited distinction between littoral and pelagic zones

autotrophic benthic community, including algal mats and macrophytes

Question 7

what are the implications of lake stratification in temperate regions?

Answer 7

• epilimnion = high primary production, low inorganic nutrients
• hypolimnion = no production, high nutrients, anaerobic decomposition affecting N and P movement

Question 8

what causes nutrient enrichment in lakes

Answer 8

runoff from agriculture, wastewater, and human activities introduce N and P, altering lake ecosystems

Question 9

how do wastwater and esthwaite water differ ecologically

Answer 9

WASTWATER = upland, oligotrophic, fully mixed and low productivity

ESTHWAITE = low land, eutrophic, stratified, high plankton populations, oxygen depletion in hypolimnion

Question 10

what adaptations do phytoplankton like cyanobacteria have in stratified lakes

Answer 10

• Thrive in high temperature and low nutrients
• Resistant to grazing, influencing zooplankton populations
• Peak abundance occurs between July and November

Question 11

what are the key features of flowing/ running water ecosystems

Answer 11

Erosional systems = high flow, coarse sediment, photic zones, epibenthic algae and benthic macroinvertebrates

Depositional systems = low flow, fine sediment, distinct littoral zones, rooted macrophytes

Question 12

how do benthic macroinvertebrates adapt to their environment?

Answer 12

SUBSTRATE ADAPTATION = predatory and grazing species prefer coarse substrate

CURRENT VELOCITY = streamlined bodies, hooks, flattened shapes for stability

Question 13

what are the functional feeding groups (FFGs) in aquatic ecosystems

Answer 13

• shredders = break down coarse organic matter (e.g. leaves)
• grazers = feed on biofilm and algae
• filterers/ collectors = consume fine organic matter
• predators = feed on other organisms

Question 14

what is the river continuum concept

Answer 14

describes the gradient in physical and biological conditions from headwaters (high flow, oxygen and erosional systems) to river mouths (low flow, oxygen and depositional systems)

Question 15

how do nutrient cycles differ in shallow vs. deep lakes

Answer 15

shallow = entire water column is photic; nutrients cycle more readily

deep = stratification creates nutrient rich hypolimnion and nutrient depleted epilimnion

Question 16

how does stratification impact oxygen levels in lakes

Answer 16

oxygen is depleted in the hypolimnion due to sediment respiration, while the epilimnion remains oxygen rich

Question 17

what are the implications of nutrient enrichment in lakes

Answer 17

species shift = increase in harmful algal blooms

productivity increase = more organic matter, lower oxygen levels, loss of aquatic life

Question 18

what drives seasonal mixing in temperate lakes

Answer 18

wind energy and cooling temperatures break stratification, mixing nutrients and oxygen throughout the water column

Question 19

how do sediment types influence benthic communities

Answer 19

coarse sediment = supports aerobic communities

fine sediment = promotes anoxic conditions and anaerobic decomposers

Question 20

what are the key traits of oligotrophic lakes like Wastwater

Answer 20

clear water, low productivity, fully mixed oxygen profiles, and minimal organic decomposition

Question 21

what adaptations do organisms in hard water develop

Answer 21

crustaceans and mollusks adapt to high calcium and magnesium concentrations necessary for their shells