L5 - Ecological features of freshwater ecosystems Flashcards
what are the 3 primary ecological zones in lakes based on location?
- littoral - water edges
- central/ pelagic - open surface water
- benthic - bottom
how is light availability in lakes catergorized
INTO photic - light-penetrated)
APHOTIC = light deprived zones
what are the 3 stratification layers in a deep lake
- Epliminion = surface layer with circulation and warm water
- Metalimnion = middle layer with temperature gradient
- Hypolimnion = deep, cold and oxygen-depleted layer
what are the productivity categories of lakes?
- Oligotrophic = low nutrients, clear water and low productivity
- Mesotrophic = moderate nutrients and productivity
- Eutrophic = high nutrients, high productivity and possible algal blooms
what defines the biological communities in lake zones?
LITTORAL ZONE = autotrophs, macrophytes, periphytes, epiphytes and biofilms
PELAGIC ZONES = neuston, phytoplankton and zooplankton
BENTHIC ZONE = heterotrophic bacteria, protozoa and detritivores
what are the key features of a shallow unstratified lake
photic zone extends through the water column
limited distinction between littoral and pelagic zones
autotrophic benthic community, including algal mats and macrophytes
what are the implications of lake stratification in temperate regions?
- epilimnion = high primary production, low inorganic nutrients
- hypolimnion = no production, high nutrients, anaerobic decomposition affecting N and P movement
what causes nutrient enrichment in lakes
runoff from agriculture, wastewater, and human activities introduce N and P, altering lake ecosystems
how do wastwater and esthwaite water differ ecologically
WASTWATER = upland, oligotrophic, fully mixed and low productivity
ESTHWAITE = low land, eutrophic, stratified, high plankton populations, oxygen depletion in hypolimnion
what adaptations do phytoplankton like cyanobacteria have in stratified lakes
- Thrive in high temperature and low nutrients
- Resistant to grazing, influencing zooplankton populations
- Peak abundance occurs between July and November
what are the key features of flowing/ running water ecosystems
Erosional systems = high flow, coarse sediment, photic zones, epibenthic algae and benthic macroinvertebrates
Depositional systems = low flow, fine sediment, distinct littoral zones, rooted macrophytes
how do benthic macroinvertebrates adapt to their environment?
SUBSTRATE ADAPTATION = predatory and grazing species prefer coarse substrate
CURRENT VELOCITY = streamlined bodies, hooks, flattened shapes for stability
what are the functional feeding groups (FFGs) in aquatic ecosystems
- 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
what is the river continuum concept
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)
how do nutrient cycles differ in shallow vs. deep lakes
shallow = entire water column is photic; nutrients cycle more readily
deep = stratification creates nutrient rich hypolimnion and nutrient depleted epilimnion
how does stratification impact oxygen levels in lakes
oxygen is depleted in the hypolimnion due to sediment respiration, while the epilimnion remains oxygen rich
what are the implications of nutrient enrichment in lakes
species shift = increase in harmful algal blooms
productivity increase = more organic matter, lower oxygen levels, loss of aquatic life
what drives seasonal mixing in temperate lakes
wind energy and cooling temperatures break stratification, mixing nutrients and oxygen throughout the water column
how do sediment types influence benthic communities
coarse sediment = supports aerobic communities
fine sediment = promotes anoxic conditions and anaerobic decomposers
what are the key traits of oligotrophic lakes like Wastwater
clear water, low productivity, fully mixed oxygen profiles, and minimal organic decomposition
what adaptations do organisms in hard water develop
crustaceans and mollusks adapt to high calcium and magnesium concentrations necessary for their shells
