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Ecological Systems > Test 5 > Flashcards

Test 5 Flashcards

1
Q

why is there less diversity in freshwater organisms

A

Very dilute compared to body liquid which is a barrier for movement

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2
Q

What is the evolutionary history of lotic groups

A
  • Direct colonization many Crustacea and Mollusca
  • Secondary colonization of insects most importantly
  • Similar freshwater communities globally
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3
Q

Adaptations for respiration (4)

A
  • Air breathing
  • Plastron
  • Pigment
  • Tracheal gills
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4
Q

Adaptations for coping with flow (6)

A
  • Streamlined shape / body parts – ‘hydrofoils’
  • Suckers
  • Modified gills
  • Modified feeding appendages
  • Hooks
  • Silk
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5
Q

Adaptations related to drought and food availability (2)

A
  • Life cycle traits and niche separation

- Dormant stages

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6
Q

2 examples of aquatic plant adaptations

A
  • 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
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7
Q

5 Examples of invertebrates

A
  • Mayfly and Molluscs are streamlined, Tortois caddis (stone one), Cased caddis fly, mountain midges
  • Are more but didn’t write them all
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8
Q

How can dispersal occur (4)

A
  • Colonization of new habitats
  • through flying adults,
  • movement up or downstream
  • drift
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9
Q

why is movement important and give examples

A

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)
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10
Q

Why do macroinvertebrates drift

A

involuntarily through disturbance or voluntarily

- fish feed on drifting invertebrates

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11
Q

name the 3 types of drift

A
  1. catastrophic - due to unfavourable conditions
  2. Behavioural - normally specific time daily
  3. constant - occurring constantly at a low level
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12
Q

Behavioural Drift - information

A
  • peak time at darkness
  • max travelled 50-60m but varies
  • Varies with season (low at winter), day to day and insect stage
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13
Q

Features of research on drift (4)

A
  • 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
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14
Q

Advantages to drift

A
  • colonisation of downstream and disturbed areas
  • when food scarce
  • avoid unfavourable conditions
  • avoid predation
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15
Q

what are the 4 dimensional nature of stream ecosystem

A
  • lateral dimension - stream channel
  • longitudinal dimension - upstream to downstream
  • temporal scale
  • Vertical - stream to hyporheos
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16
Q

What is the hyporheic zone and explain

A
  • 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
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17
Q

What is the difference between Meiofauna and Ocassional hypotheos

A

M lives permanently in the hyporheic zone while OC spend part of their life in it

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18
Q

Factors of hyporheic zone

A
  • 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
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19
Q

Advantages to Hyporheic zone (4)

A
  • Lack of predators
  • Plentiful food; biofilm, protozoa and bacteria
  • More steady environment e.g. temperature
  • Survival during adverse conditions..e.g. floods
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20
Q

Disadvantages to hyporheic zone (5)

A
  • Limited space
  • Reduced current velocities
  • Low DO, High Co2
  • Lack of light
  • Accumulation of waste
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21
Q

Competition

A

occurs when individuals compete for resources which are in limited supply
can be interspecific (diff) or intraspecific (same)

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22
Q

What are the two forms of competition

A

Exploitation - where food or space is limited

Interference - aggressive interactions between competitor species

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23
Q

What is resource partitioning

A

The division of limited resources by species to help avoid competition in an ecological niche

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24
Q

Name aquatic predators

A
  • Fish

- Invertebrates: Odonata, Plecoptera and more

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25
Q

How is prey selected

A

Size and activity - drift patterns, size of pre, presence of fish
Contrast - visibility

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26
Q

Prey vulnerability and avoidance tactics

A
  • Avoid encounter - low movement rates

- Avoid capture - pre = detect and flee, post = chemical defences, amour

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27
Q

Examples of prey tactics to avoid capture

A
  • Morphological - daphnia tail/helmet spines
  • fast swimming - Baetis
  • Thanotaxis - ‘playing dead’
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28
Q

Camouflage - Aposematism (use of colour to warn predators) in water mites

A

Assume red colour ‘saying’ they are distasteful

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29
Q

Behavioural - Gerridae (water striders)

A

found only in vegetation where fish present and open water when fish are not

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30
Q

Adaptation to life cycle in presence of predators

A

trout presence cause Baetis mayflies to accelerate laval development results in metamorphosis so not threated by trout
- fish odor has the same affects

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31
Q

Training bias

A

predators may switch food type if original gets smaller numbers and other grown - similar family group

32
Q

Herbivory influence

A

reduces standing crop so influences community composition of periphyton by selective feeding

33
Q

what is abiotic

A

the physical environment may limit the opportunities for biotic interactions

34
Q

what is the ‘harsh-benign’ concept

A

harsh - few competition/predation effects (experience disturbance)
benign - well developed competition/predation

35
Q

Disturbance

A

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

36
Q

What is the Intermediate Disturbance Hypothesis (Townsend 1997) and compare to low and high ( Species richness = SR)

A

moderate disturbance fosters great diversity

  • Low - SR decrease as competition exclusion increases
  • High - SR decreases due to ^ species movement
  • Not widely demonstrated
37
Q

What is Patch Dynamics Concept

A

Disturbance continually opening up patches for colonization

38
Q

Biological activity may create new patches ‘ecosystem engineers’ - examples (4)

A
  • 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
39
Q

Reciprocal Subsidies - Salmon - explain

A
  • Spawning salmon brings nitrogen from ocean to freshwater when they decay
  • Aquatic organisms benefit from food source
  • Terrestrial environment benefits - on banks bears eat
40
Q

How tree rings were used to see abundance of salmon

A

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
41
Q

Reciprocal subsidies - terrestrial invertebrates

A

Terrestrial invertebrates as prey subsides for stream fish therefore more macroinvertebrates occur as don’t have as many predators - but still eaten by fish

42
Q

what is the Allens paradox

A

Trout consume 30x more prey biomass of invertebrates then available - 60% diet is terrestrial invertebrates

43
Q

Why does the availability of allochthonous food source change predator patterns

A

predator increase, or predator switching

44
Q

How much of diets of dominant spiders and carabid beetles is aquatic insects on a braided floodplain river

A

50%

80%

45
Q

How do humans affect subsides

A
  • removal of riparian vegetation can affect allochthonous inputs of terrestrial invertebrates
  • Degraded in stream habitats can reduce stream communities
46
Q

Name the threats to freshwater systems

A

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

47
Q

What are the uses for water

A
  • Public and private water supply
  • Agriculture - globally biggest 67%
  • Electricity
  • Fish farming
  • Water cress
  • Amenity ponds
  • Water treatment and transport
48
Q

Why are channels modified

A
  • Flood control
  • Navigation
  • Urbanisation
  • Relocation
  • Prevention of erosion
49
Q

What is a ‘natural river channel like

A
  • Meandering
  • Riffle/pool structure
  • Erosion/deposition features
  • Rich riparian vegetation
50
Q

What a modern river channel is like

A
  • Straightened
  • Loss of riffle/pool structure
  • Reinforced banks
  • Loss of heterogeneity
51
Q

Give 2 examples of river channelling

A

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

52
Q

‘natural river’ = Rich Riparian zone

A
  • high inputs if CPOM
  • Terrestrial invertebrates
  • Shading
53
Q

modern river = loss of riparian zone

A
  • Reduced CPOM and LWD
  • Reduced cover for fish
  • Reduced shade - more variable temps - v low DO
54
Q

‘natural’ river of high and low flowing condition

A 
high
 - in pools, lower in riffles
- resting areas abundant 
low 
- sufficient water depth to support aquatic life
55
Q

modern river of high and low flowing conditions

A

high
- lack of slow low refuge and lack of depth
low
- insufficient depth of flow and no support diversity

56
Q

Natural river infiltration

3

A
  • 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
57
Q

Modern river infiltration

A
  • Hard surfaces
  • focussed inputs to river through storm drains
  • Rain hits impervious surfaces and run though storm drains to the stream
58
Q

Main river pollutants - urban wastewater

A
  • Sewage treatment works (STWs)
  • Combined sewer overflow (CSOs)
  • Misconnected sewers
  • Sewage contains organic material plus soaps (high in phosphates), heavy metals, and other pollutants
59
Q

Main river pollutants - Agricultural waste

A
  • Slurry
  • silage clamps
  • Dairy washings
  • Disinfectants
  • Pesticides
  • Fertilizers
60
Q

Main river pollutants - Industrial wastes

A
  • Heat pollution
  • Oxygen depleting substances
  • Heavy metals
  • Carcinogens
  • PAHs, oestrogen mimics, mine drainage
61
Q

Main river pollutants - Transport system

A
  • Road waste and storm drain effluent

- De-icer runoff (salt and urea)

62
Q

Main river pollutants - Light pollution

A
  • Affects drift, and aerial flight patterns of aquatic insects
63
Q

Organic compounds that act as substrate for microorganisms

A
  • Proteins (NH2 +COOH)
  • Carbohydrates (Cx H2 Oy)
  • Fats (RCOOH)
64
Q

Biochemical Oxygen Demand

A

Amount of oxygen consumed by microorganisms in decomposing organic ma‘er

65
Q

Learn slide on BOD

A

aghhhhh

66
Q

Sources of organic waste

A
  • Domestic sewage
  • Industrial - brewing; dairy; meat packing; other food processing; textiles and paper
  • Agricultural - slurry; milk and dairy washings; silage liquor
67
Q

Impacts of organic pollution

A
  • 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
68
Q

Nitrogen curve linked to oxygen sag curve

A

NH3>NH4>NO2>NO3

69
Q

Oxygen sag curve - algae order of return

A

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

70
Q

Fish - polluted river

A
  • mobile so can move out of polluted area

- areas can become fishless due to fish dying or leaving

71
Q

Oxygen sag curve - invertebrates order of return

A

Clean water fauna fall straight away and start rising when Chironomus peak which is after the tubificidae peak. Asellus then rises

72
Q

What polluted the river thames

A
  • 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
73
Q

Recovery of thames

A
  • Salmon reintroduced in 1980s and ladders built
  • 383 1993 but 2005 none left
  • huge tunnel being built under thames
74
Q

How has thames been recovered

A
  • replacing concrete with rubble> traps silt/mud > plant colonize
  • Planting reed beds
75
Q

Biological monitoring

A

Give early warning of pollution

  • track dispersal of discharge
  • Identify affects of discharge
  • Identify affects of atmospheric deposition
76
Q

Advantages over chemical methods

A

Integrates info over time
simple to collects organisms
- might pick up pollutants chemicals missed

Ecological Systems (5 decks)

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