Lecture 15: Impacts on Ecosystems Flashcards
How did an aquatic plant invasion cause bald eagle deaths?
- Hydrilla-cyanobacterial mats spread, which mallard ducks are highly exposed to. The mats produce a neurotoxin causing degenerative brian disease in the ducks. Bald eagles die via eating the duck.
- Hydrilla on it’s own does not produce this…needs the cyano
- removal of a top predator like the eagle will have ripple effects in the ecosystem
What is an ecosystem?
a set of organisms the interact with each other and their physical environment
*energy flow
What was the ecosystem impact of the gypsy moth?
- defoliation of oak and pine forests brought down net carbon uptake by 40-55%
How do invaders alter ecosystem processes?
- when they alter a limiting resource
- When they alter the flow of energy within the system
- When they alter the frequency / intensity of disturbance
**such invaders tend to differ greatly from resident species in how they acquire and use resources
Alterations of Ecosystem ex via limiting resource:
- Myrica faya
- nitrogen fixing tree
- native to azores, introduce in Hawaii
- facilitates invasions by other exotics
- in lava fields which are nutrient poor
- altered soil chemistry
Explain the primary succession in the lava fields after Myrica entered it.
- increased N
- plants were able to take advantage of this change i availability
- For this to be true:
1. N must be a limiting nutrient
2. N-fixation by Myrna must alter the ecosystem’s N budget
3. N fixed by Myrica must become available to other organisms - *experiment found that addition of N to young lava field promoted native plant growth where as it didn’t in old fields
Alterations of Ecosystem ex via limiting resource:
- Saltceder trees
- deeply rooted in groundwater
- have high transpiration rate
- desiccate streams and marshes
- threaten stream pool habitats of endangered pupfish
Alterations of Ecosystem ex via limiting resource:
- Pine and Eucalyptus in South Africa
- heavy water uptake
- caused many rivers to dry up or flow infrequently
Alterations of Ecosystem ex via Alter the flow of energy within ecosystems?
- introduction of piscivores to small lakes
- filter feeders introduced to isolated systems
Explain alteration in energy flow via zebra mussels?
- they clear the water
- deposit feces and pseudofeces on sidemoits
- pseudofeces are material not digested, wrapped in mucous. The sheath has some carbon in it, so it is an energy deposit for others
- take materials from the water column and release these
- so they provide food
- they also provide shelter, interstitial space providing refuge for small invertebrates
*density of invertebrates increased with zebra
Alterations of Ecosystem ex via alter the frequency or intensity of disturbance?
- Broomsedge (invasive grass)
- European earthworms
- Feral pigs
Alterations of Ecosystem ex via alter the frequency or intensity of disturbance:
1. Broomsedge
- perennial weed
- invaded slopes in wet mountain forest areas
- dring winter, the weed is dormant and transpires very little water
- soils on mountain slopes become saturated with water , resulting in landslides
Alterations of Ecosystem ex via alter the frequency or intensity of disturbance:
2. Earthworms?
- exotic earthworms (night crawlers) effect on deciduous forest floors
- chew up leaf litter which normally takes 3-5 years to decay
- they speed up decomp
- causes habitat to change bc they remove understory which needs leaf litter
Alterations of Ecosystem ex via alter the frequency or intensity of disturbance:
3. Feral pigs?
- native to Eurasia
- introduced for farms and game
- disturb soil through their digging activities
- remove litter
- trample soil
- disturbance causes erosion, releasing nitrogen, change soil chemistry and water
- changes understory veg
- pits they create fill up with water which is a great place for mosquitos
L> enhance malaria which can infect birds
Explain the invasion of the mediterranean sea by the green alga Caulerpa taxifolia
- used in aquaria
- grows in many temp regimes
- it spread like crazy
- spreading via cuttings from boats
- genetically all the same strain , spreading colonially
- homogenizing the habitat
- algal also has toxins to resist grazers
What are the effects of introducing goldfish to a pond?
stir up fine sediment, suspending them, increasing turbidity
- gold fish are shiny which attracts attention of birds
- more gold fish = more turbidity, their activity can reduce visibility to predators = niche construction
- increased turbidity hurts macrophytes bc it lowers illumination
- epiphytic inverts tha live on plants, will be harmed as well
L> spotted newts feed on these inverts, it’s a visual predator, so turbidity reduces it’s sight and foraging success
L> newts pop will lower
**doesn’t always need to be a predator causing a change
Impact of common carp on rooted aquatic plants?
- ## uproots plants, eat plants, increases turbidity which reduces light, which reduces plant biomass
What four things do we know so far about ecosystem impacts?
- many invasions cause no detectable ecosystem impacts
- Invasions can alter a varied of ecosystem properties: productivity, nutrient cycling, hydrology etc
- To cause ecosystem level impacts, invaders must be able to acquire and use resources differently than native species (e.g. by altering energy flow or disturbance regimes)
- Some keystone invaders can cause cascading impacts that affect multiple components of the ecosystem
Explain the root rot fungus
wrt death of threes and shrubs
- soil fungus
- attacks roots of shrubs and trees
- antive to SE Asia
- introduced to Aus with orange trees from Indonesia
- caused dieback of plants
- spread widely in Australia via soil on wheels
- caused death of threes and shrubs
- understory increases
- loss of nesting sites and refuges –> therefore reduction in pollinators and seed disposals -> loss of prey for predators
- loss of nectar insects and birds, therefore reduced food for predators
- loss of transpiration -> increase water table
- reduced plant biomass -> reduced nutrient cycling
Explain the root rot fungus
wrt increase in herb cover
- increased food for marsupials (increase dung beetles )
- increased food for some insects –> increase in certain predators
- suppressed germination of wood plants -> reduction in associated animals-> reduction of certain predators
What are the three ways zebra mussels impact the ecosystem
- Removal of suspended particles
- Biodeposition
- Biofouling
Zebra mussel invasion:
1. Removal of Suspended particles?
1 loss of phytoplankton
- reduced food source for zooplankton
- reduced food for planktivores
- reduced food for piscivores
2. Increased light penetration - increase in benthic algae and plants
- increased food and habitat for consumers
3. Altered nutrient and contaminant cycles
Zebra mussel invasion:
2. Biodeposition
- Increased sedimentation
- lower dissolved oxygen
- habitat for burrowing fauna - increased food source for detritivores
- increased food for predators
Zebra mussel invasion:
3. Biofouling
- Habitat for interstitial fauna
- increased food for predators - Mortality of native mussels
- reduced sediment mixing
- lower dissolved oxygen
Cascading ecosystem impacts are caused by?
- species that create or disrupt energy pathways
i. e. those that cut or build links between species from different trophic groups or ecosystem compartments - solid lines = transfer of organic
- Dashed= pathways of inorganic
*ex = zebra mussels
altered links from carnivore all the way to detritus
- Ex: mnemiopsis jelly fish altered the link btwn herbivore and carnivore via feeding on anchovy
- Ex: goats on islands and chestnut blight both alter links between plants and herbivores + detritus
Explain the cascade in Hawaii upon the intro of goats and pigs
- took out nectar producing plants
- which lowered levels of nectivorous birds
- which lowered hawaiian hawk
Invasiveness vs impact of exotic sp?
- high impact = higher rate of spread
- higher prob of establishment success too
Summarize key points of this chapter.
- An important determinant of an invaders impact or native species i the naivete of the recipient community
- The greatest ecological impacts are caused by uncontrolled generalist consumers
- Ecosystem level impacts tend to be caused by invaders that acquire and use resource differently from resident species.
- Cascading ecosystem impacts are caused by invaders that create or disrupt energy pathways
- The potential impact of an exotic species is not correlated with its ability to spread
Explain the zebra mussel impact one more timeee.
- overgrow on other mussels
- facilitate other inverts via providing interstitial spaces
- stimulate success of grazing inverts which can also leave and go to other areas
- can cause benthic algal to increase via increasing light and water clarity
- submerged macrophytes do well with zebra
- phytoplankton will reduce bc of the filtrations, zooplankton which feed on them will decrease and larval fish that feed o zooplankton will decrease primary production, habitat structure, nutrient cycling all effected.
