Subsidies, stoichometry resilience exam 3 Flashcards
(39 cards)
Movements of materials (e.g., nutrients, organisms) across ecosystem boundaries, affecting structure and function
subsidies in ecosystem ecology
What do subsidies reflect?
Inefficiencies in retention within ecosystems.
Name two common gradients driving subsidies.
- Gravitational (e.g., downhill flow), 2. Productivity (movement from high to low productivity systems).
list types of subsidy transport.
passive, mediated, active
define passive
flooding, leaf fall, upwelling
define mediated
animal transport (e.g., feces)
define active
migration, directed movement
How is the 13C labeling experiment used to trace subsidies in lakes?
It alters the stable carbon isotope ratio in algae, revealing carbon source reliance in organisms.
How do terrestrial subsidies affect aquatic food webs?
They enhance the production of higher trophic levels by supplementing energy and nutrient inputs.
Example of a cross-ecosystem subsidy involving salmon:
Migrating salmon transport marine nutrients upstream into freshwater and terrestrial systems.
How do marine-derived nutrients affect desert island ecosystems?
Increase gecko populations, support plants (via seabird guano), and buffer dry years.
An indirect interaction where predators suppress prey, leading to cascading effects down the food web.
trophic cascade
How can prey subsidies affect resource dynamics?
Can increase predators and opportunistic herbivores, reduce plant biomass, and disrupt nutrient retention.
Give an example of indirect prey subsidy effects.
Midges emerging from lakes feed birds and spiders, which then prey on terrestrial insects, altering land food webs.
The ability of an ecosystem to absorb disturbance and return to its original state.
ecosystem resilience
A tipping point beyond which a small change causes a large, often irreversible, shift in ecosystem state.
a threshold in ecological systems
The phenomenon where returning to prior conditions does not restore the original ecosystem state.
hysteresis
What are the two alternate stable states in shallow lakes?
Clear state and turbid state
Define Clear state
rooted plants, low phytoplankton, high oxygen
Define Turbid State
algae-dominated, no rooted plants, low oxygen
How do rooted plants influence lake stability?
Reduce P movement
Oxygenate sediments
Provide refuge for grazers (e.g., Daphnia)
What happens when P inputs exceed a critical level?
Phytoplankton reduce light, kill rooted plants, increase nutrient release, leading to a turbid state.
Why can eutrophication be hard to reverse?
Nutrients stored in sediments sustain high productivity even after external inputs decrease.
What happens to oxygen when phosphate supply is high?
Deep water becomes anoxic, causing further phosphate release from sediments.
