Test 5 Flashcards
why is there less diversity in freshwater organisms
Very dilute compared to body liquid which is a barrier for movement
What is the evolutionary history of lotic groups
- Direct colonization many Crustacea and Mollusca
- Secondary colonization of insects most importantly
- Similar freshwater communities globally
Adaptations for respiration (4)
- Air breathing
- Plastron
- Pigment
- Tracheal gills
Adaptations for coping with flow (6)
- Streamlined shape / body parts – ‘hydrofoils’
- Suckers
- Modified gills
- Modified feeding appendages
- Hooks
- Silk
Adaptations related to drought and food availability (2)
- Life cycle traits and niche separation
- Dormant stages
2 examples of aquatic plant adaptations
- Water crowfoot – fine prong like leaves, trap sediment around roots, survives as rhizomes
- Brandy Bottle – Thick leaves on top like lily but floppy below, think floppy as have less resistance but could also be for trapping sediment for leaves
5 Examples of invertebrates
- Mayfly and Molluscs are streamlined, Tortois caddis (stone one), Cased caddis fly, mountain midges
- Are more but didn’t write them all
How can dispersal occur (4)
- Colonization of new habitats
- through flying adults,
- movement up or downstream
- drift
why is movement important and give examples
for colonisation of new habitats and repopulation of existing
- freshwater shrimp can swim upstream but mainly at night
- flying adult stage can also move upstream (mayfly)
Why do macroinvertebrates drift
involuntarily through disturbance or voluntarily
- fish feed on drifting invertebrates
name the 3 types of drift
- catastrophic - due to unfavourable conditions
- Behavioural - normally specific time daily
- constant - occurring constantly at a low level
Behavioural Drift - information
- peak time at darkness
- max travelled 50-60m but varies
- Varies with season (low at winter), day to day and insect stage
Features of research on drift (4)
- peak occurs at night
- most drift occurs in summer and autumn
- large instars only drift at night while smaller more 50:50
- where no fish less obvious pattern
Advantages to drift
- colonisation of downstream and disturbed areas
- when food scarce
- avoid unfavourable conditions
- avoid predation
what are the 4 dimensional nature of stream ecosystem
- lateral dimension - stream channel
- longitudinal dimension - upstream to downstream
- temporal scale
- Vertical - stream to hyporheos
What is the hyporheic zone and explain
- middle zone between river and groundwater
- the community that live there are called hypotheos contain a wide variety of taxa
- depth varies >100cm but width can get up to 2km from stream
What is the difference between Meiofauna and Ocassional hypotheos
M lives permanently in the hyporheic zone while OC spend part of their life in it
Factors of hyporheic zone
- very little temp variation
- very little light penetration - >4-5 x grain size of sediment
- 1/1000 velocity compared to surface
- DO declines with depth - at 30cm can be 5% of surface
- acts as a buffer zone for nitrate
Advantages to Hyporheic zone (4)
- Lack of predators
- Plentiful food; biofilm, protozoa and bacteria
- More steady environment e.g. temperature
- Survival during adverse conditions..e.g. floods
Disadvantages to hyporheic zone (5)
- Limited space
- Reduced current velocities
- Low DO, High Co2
- Lack of light
- Accumulation of waste
Competition
occurs when individuals compete for resources which are in limited supply
can be interspecific (diff) or intraspecific (same)
What are the two forms of competition
Exploitation - where food or space is limited
Interference - aggressive interactions between competitor species
What is resource partitioning
The division of limited resources by species to help avoid competition in an ecological niche
Name aquatic predators
- Fish
- Invertebrates: Odonata, Plecoptera and more
How is prey selected
Size and activity - drift patterns, size of pre, presence of fish
Contrast - visibility
Prey vulnerability and avoidance tactics
- Avoid encounter - low movement rates
- Avoid capture - pre = detect and flee, post = chemical defences, amour
Examples of prey tactics to avoid capture
- Morphological - daphnia tail/helmet spines
- fast swimming - Baetis
- Thanotaxis - ‘playing dead’
Camouflage - Aposematism (use of colour to warn predators) in water mites
Assume red colour ‘saying’ they are distasteful
Behavioural - Gerridae (water striders)
found only in vegetation where fish present and open water when fish are not
Adaptation to life cycle in presence of predators
trout presence cause Baetis mayflies to accelerate laval development results in metamorphosis so not threated by trout
- fish odor has the same affects
Training bias
predators may switch food type if original gets smaller numbers and other grown - similar family group
Herbivory influence
reduces standing crop so influences community composition of periphyton by selective feeding
what is abiotic
the physical environment may limit the opportunities for biotic interactions
what is the ‘harsh-benign’ concept
harsh - few competition/predation effects (experience disturbance)
benign - well developed competition/predation
Disturbance
any relatively discrete event in time that removes organisms and opens up space that can be colonized by individuals of the same or difference species
What is the Intermediate Disturbance Hypothesis (Townsend 1997) and compare to low and high ( Species richness = SR)
moderate disturbance fosters great diversity
- Low - SR decrease as competition exclusion increases
- High - SR decreases due to ^ species movement
- Not widely demonstrated
What is Patch Dynamics Concept
Disturbance continually opening up patches for colonization
Biological activity may create new patches ‘ecosystem engineers’ - examples (4)
- Salmon and trout redds
- Grazing by Chironomidae creates new patches for benthic algae
- Aquatic plants - reduced flow traps sediment for nutrients
- Crayfish - increase availability of FPOM in headwater streams BUT may create loss of diversity
Reciprocal Subsidies - Salmon - explain
- Spawning salmon brings nitrogen from ocean to freshwater when they decay
- Aquatic organisms benefit from food source
- Terrestrial environment benefits - on banks bears eat
How tree rings were used to see abundance of salmon
Used to find marine N in years previously
- was in 5/7 rivers used the N in tree rings of known data to work out salmon numbers in unknown data
- Wolf point creek had none even though >10 000 salmon per year - retention is key
Reciprocal subsidies - terrestrial invertebrates
Terrestrial invertebrates as prey subsides for stream fish therefore more macroinvertebrates occur as don’t have as many predators - but still eaten by fish
what is the Allens paradox
Trout consume 30x more prey biomass of invertebrates then available - 60% diet is terrestrial invertebrates
Why does the availability of allochthonous food source change predator patterns
predator increase, or predator switching
How much of diets of dominant spiders and carabid beetles is aquatic insects on a braided floodplain river
50%
80%
How do humans affect subsides
- removal of riparian vegetation can affect allochthonous inputs of terrestrial invertebrates
- Degraded in stream habitats can reduce stream communities
Name the threats to freshwater systems
Demands for water - reduced flow, impoundments
Demands for space - channelization, flood protection
Land use changes
Pollution
Exploitation of species
Introduction of non-Native species
Climate change
What are the uses for water
- Public and private water supply
- Agriculture - globally biggest 67%
- Electricity
- Fish farming
- Water cress
- Amenity ponds
- Water treatment and transport
Why are channels modified
- Flood control
- Navigation
- Urbanisation
- Relocation
- Prevention of erosion
What is a ‘natural river channel like
- Meandering
- Riffle/pool structure
- Erosion/deposition features
- Rich riparian vegetation
What a modern river channel is like
- Straightened
- Loss of riffle/pool structure
- Reinforced banks
- Loss of heterogeneity
Give 2 examples of river channelling
Rhone, France
- one dried arm one embanked canal
- lowered table so now very little river
Willamette, Oregon
- Multi channelled with lots of forestry in stream blocking channels but now little forest and almost 1 channel
‘natural river’ = Rich Riparian zone
- high inputs if CPOM
- Terrestrial invertebrates
- Shading
modern river = loss of riparian zone
- Reduced CPOM and LWD
- Reduced cover for fish
- Reduced shade - more variable temps - v low DO
‘natural’ river of high and low flowing condition
high - in pools, lower in riffles - resting areas abundant low - sufficient water depth to support aquatic life
modern river of high and low flowing conditions
high
- lack of slow low refuge and lack of depth
low
- insufficient depth of flow and no support diversity
Natural river infiltration
3
- Water percolates through soils and groundwater
- Flows into soil all the way along
- Many points of entry of water into natural stream after filtration through solid
Modern river infiltration
- Hard surfaces
- focussed inputs to river through storm drains
- Rain hits impervious surfaces and run though storm drains to the stream
Main river pollutants - urban wastewater
- Sewage treatment works (STWs)
- Combined sewer overflow (CSOs)
- Misconnected sewers
- Sewage contains organic material plus soaps (high in phosphates), heavy metals, and other pollutants
Main river pollutants - Agricultural waste
- Slurry
- silage clamps
- Dairy washings
- Disinfectants
- Pesticides
- Fertilizers
Main river pollutants - Industrial wastes
- Heat pollution
- Oxygen depleting substances
- Heavy metals
- Carcinogens
- PAHs, oestrogen mimics, mine drainage
Main river pollutants - Transport system
- Road waste and storm drain effluent
- De-icer runoff (salt and urea)
Main river pollutants - Light pollution
- Affects drift, and aerial flight patterns of aquatic insects
Organic compounds that act as substrate for microorganisms
- Proteins (NH2 +COOH)
- Carbohydrates (Cx H2 Oy)
- Fats (RCOOH)
Biochemical Oxygen Demand
Amount of oxygen consumed by microorganisms in decomposing organic ma‘er
Learn slide on BOD
aghhhhh
Sources of organic waste
- Domestic sewage
- Industrial - brewing; dairy; meat packing; other food processing; textiles and paper
- Agricultural - slurry; milk and dairy washings; silage liquor
Impacts of organic pollution
- Breakdown of organic material leads to reduction in dissolved oxygen
- Extent depends on
- BOD of the discharge
- BOD of the receiving river water
- Dilution
- Temperature
- Aeration
Nitrogen curve linked to oxygen sag curve
NH3>NH4>NO2>NO3
Oxygen sag curve - algae order of return
Bacteria - slow decrease
Sewage fungas high increase as bacteria decreases
Protozoa increases at same time as SF then both decrease as Algae and Cladophora increase then decrease again
Fish - polluted river
- mobile so can move out of polluted area
- areas can become fishless due to fish dying or leaving
Oxygen sag curve - invertebrates order of return
Clean water fauna fall straight away and start rising when Chironomus peak which is after the tubificidae peak. Asellus then rises
What polluted the river thames
- First sewers straight into river in 1800
- Organic pollution killing river life
- Last salmon was caught in 1833
- 1930s sewage works built - e.g. Beckton
Recovery of thames
- Salmon reintroduced in 1980s and ladders built
- 383 1993 but 2005 none left
- huge tunnel being built under thames
How has thames been recovered
- replacing concrete with rubble> traps silt/mud > plant colonize
- Planting reed beds
Biological monitoring
Give early warning of pollution
- track dispersal of discharge
- Identify affects of discharge
- Identify affects of atmospheric deposition
Advantages over chemical methods
Integrates info over time
simple to collects organisms
- might pick up pollutants chemicals missed
