Test 2.2 Biotic & Abiotic Interactions Flashcards
What filters in order of size affect regional pools of species in terms of multiple species traits?
- (Biggest) Watershed/basin filters
- Valley/reach filters
- Channel unit filters
- (Smallest) Microhabitat filters
What is the idea of Trophic Structure
The relationships of different feeding groups and how the types of food and energy availability affects what’s present
Definition of particular organic carbon
Coarse particular organic matter (CPOM) + fine particular organic matter (FPOM)
What size is coarse particular organic matter
> 1mm
What size is fine particular organic matter
<1mm
What proportion of trophic groups are found in sand and mud mesohabitats of a river
Mesohabitat: middle of river
Dominated by collector gatherers and
In mud: >25% predators
In sand: <25% predators
What do food webs illustrate?
Trophic links and energy transfer
When does competition occur and in what forms?
What is the difference between interspecific and intraspecific
When resources are limited in supply.
What are the two forms of competition?
How can competition be reduced?
Exploitation: food or space is limited
Interference: aggression between competing species or individuals
Competition can be reduced through resource partitioning
Competition case study between reduced Glossosma (Caddisfly) and Baetis
Baetis: good coloniser but poor competitor. Fugitive species. Multivoltine. Quickly drifts into new areas.
Reduced Glossosma = increased Baetis
Meaning of uni, bi & multivoltine
Organisms with x number of generations per year
2 different types of partitioning?
Time (temporal):
Cyprinid fish feeding at different times of day
Space (spatial): Case less caddis larvae feeding at different sites e.g. Exposed boulder surface Crevices between boulders Gravel bed sites
What do predators consider when selecting prey
Size & activity
-Diurnal patterns, prey size, presence of fish predators
Contrast
-Visibility
What are prey vulnerability and avoidance tactics
Avoid encounter
- Spatial segregation, use of refuge
- Temporal segregation
- Low movement rates
- Reduced detectiveness (visual, mechanical & chemical)
Avoid capture
- Detect and flee
- Warning/ startling behaviour
Definition of instars
Development stages of arthropods
Examples of prey tactics to avoid capture
Morphological: Daphnia tail/ helmet spines
Fast swimming: Baetis
Thanotaxis: playing dead
Hide in vegetation if fish present: Gerridae (Water striders)
Adaptation of lifecycle in presence of predators: Baetis emerge as adults in smaller sizes faster. Although fewer eggs
Camouflage:
Body colouration
Use of materials to hide in e.g. cased caddisfly
What is aposematism?
The use of bright colours to warn predators not to eat the organism e.g. red water mites ‘distastefulness’
What is predation training bias?
Predators preferentially seek out a familiar food type
May switch prey type
What is top down or bottom up control
Classic assumption of bottom up trophic pyramid
But predators may exert top down control
What is the influence of grazing on periphyton growing on stones? (Diatoms)
Reduces standing crop of periphyton
Influences community composition of periphyton by selective feeding
Definition of disturbance
Events that remove existing organisms to open up for colonisation by new organisms
e.g. flooding, pollution events
What does the ‘harsh-benign’ concept of Peckarsky (1980) state?
A gradient from harsh to benign
Harsh- few competition/ predation effects
Benign- environment allows for well developed competition/ predation effects
What is the intermediate Disturbance Hypothesis (IDH)
Suggests the maximum species diversity tends to find an intermediate level of disturbance. Colonisers keep recolonising.
What is the Patch Dynamics Concept (PDC)
Disturbance continually opens up patches that can be colonised.
Fugitive species have recurrent opportunities for recolonisation
Meaning of fugitive species
Species that are quick to colonise a habitat but are poor competitors.
What are Patch Dynamics?
Patches can be made available at any scale:
- Reach after a major flood
- New gravel bar
- Small patch on a stone
Biological activity may create new patches ‘ecosystem engineers’
e.g. salmon & trout redds turn over gravel to lay eggs; removing diatoms
What is the impact of crayfish on freshwater systems?
Burrowing helps remove silt to create clean gravel patches
Create a lot of suspended sediment due to burrowing
What is the impact of beavers on freshwater systems?
Create dams in slow flowing areas; provides refuge for juvenile fish
What is the impact of blackly larvae on freshwater systems?
60m downstream of larvae current velocity reduced by 75%
Impact of Hydropsyche (net spinning caddis)
Increase stability of gravel by silk spinning. Making gravel adhesive to each other.
Increasing substrate stability; reduce flow/provide retreats for mayfly nymphs
What are Reciprocal Subsidies?
Subsidies between environments e.g.
Terrestrial <> freshwater
Marine > freshwater > terrestrial
What is a subsidy in ecology?
Payment in terms of energy, food and materials
What is the impact of movement of salmon?
Migratory fish: adults spend most time at sea. Lay eggs in freshwater.
All adults die when they spawn eggs (especially NA species).
Brings nutrients up glacial stream systems (nutrient poor) when salmon decay. Inputs C,N & P into the system
How does the terrestrial environment benefit from salmon movement?
Dead salmon dragged up into riparian zone by bears.
Left behind carcass decays-enriches soil
Why has no marine derived nitrogen been found in Wolf Creek food webs despite >10,000 pink salmon spawning?
How is this detected?
Stable isotope analysis of marine derived N not present in aquatic insects, juvenile fish or in leaves of willow or alder.
Due to low retention of carcasses
How much do terrestrial invertebrate prey subsidies contribute to stream fish?
As much as 250 mg/m^2
Terrestrial input may equal the production of benthic macro invertebrates within the stream
What are the temporal differences in subsidy through terrestrial invertebrates
Seasonally- peaks in summer
Year to year- lower in cooler wetter summers
Diurnal changes- highest during the afternoon
Quantity also varies according to type of riparian vegetation growing alongside the stream- higher in deciduous (alder) than coniferous
What is Allen’s Paradox?
Trout eating 30x more prey invertebrates than present.
Mainly eating terrestrial invertebrates entering the system. Can eat up to 80% benthic production of invertebrates
Meaning of allochthonous and autochthonous food source?
Autochthonous: food source from within system
Allochthonous food source from outside system
How does availability of allochthonous food source affect predators?
May lead to increase in predators or predator switching
How do terrestrial invertebrates affect aquatic insects?
Aquatic insects make up around 50% diet of spiders and 80% of beetles on braided river floodplain
Fewer of adult stonefly surviving
How can humans affect allochthonous inputs of terrestrial invertebrates?
Removal of riparian vegetation: forestry activity or channel modification
Balance can be redressed by importing salmon carcasses
