BIOL213 Ecology of Freshwaters Univ of Liverpool
By Dr Rick Leah
Jones Building
School of Biological Sciences
1) Overview of this document:
This is a brief summary of the lecture. The main aim was to give an introduction to the zooplankton, the composition of the open water community and the influence of predation in structuring it. Fish play a major role through changing the balance of cladocera and copepoda which in turn alter the nature and composition of the phytoplankton through grazing.
2) Suggested Reading:
Moss Chapter 7: The plankton and fish communities of the open water of lakes
3) Lake Abiotic Conditions
The most influential factors in lakes:
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Zones
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Flow
Mixing
Nutrients
4) Pelagic Community
The main components of the lake pelagic community
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Phytoplankton
Zooplankton
Fish
5) Zooplankton
An introduction was given to the members of the zooplankton
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Rotifers
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Crustaceans
Rotifers
Rotifers
Copepods
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Calanoid
– Filter feeding Grazers
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Cyclopoid – Raptorial feeders
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BIOL213 Ecology of Freshwaters Univ of Liverpool
6) Zooplankton Feeding
A discussion of zooplankton feeding methods followed including the significance of size
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Rotifers
Copepods
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Cladocerans
Bosmina
Daphnia
Daphnia lge
7) Zooplankton
Interactions between components of the zooplankton were discussed including the predatory midge larva Chaoborus
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Rotifers
Copepods
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Cladocera
Insect larvae (eg Chaoborus)
8) Life History Strategies
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Parthenogenesis
– Cladocera & Rotifers
Sex when times are hard
Generation times
Copepods
– many stages - long
9) Lake Community Structure
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Limiting Factors?
10) Lake Community Structure
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Algal production : nutrients
Algal community structure : nutrients : grazing : zooplankton
Zooplankton composition : fish and other predators
11) Grazing
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Selective removal of phytoplankton
Leads to changes in phytoplankton composition
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Overall reduction in standing crop
12) Fish Feeding
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Feeding dependent on the range of food items available
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BIOL213 Ecology of Freshwaters Univ of Liverpool
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Prey characteristics
Predator Characteristics
Predator learning
13) Food Characteristics
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Size and visibility
Too small to see/ or not worth the effort
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Too large to capture (physical size or swimming ability)
The example of Broads Plankton composition was used
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Palatability
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Digestibility
Requirements for nutrients
Choice – availability and abundance
15) Selectivity
16) Planktivores
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Facultative planktivores
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Obligate planktivores
17) Eutrophication
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Nutrients
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Algae
Zooplankton
Fish
18) Size-Efficiency Hypothesis
Brooks and Dodson (1965)
Introduction of fish
Crystal Lake Connecticut
19) Size-Efficiency Hypothesis
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Large efficient grazers
– filter feeding Cladocera
Smaller Cladocera – Bosmina
Less efficient grazers – Calanoid copepods
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BIOL213 Ecology of Freshwaters Univ of Liverpool
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Raptorial predators – Cyclopoid copepods
20) Competition
Algal Grazers
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Unstructured environment
Similar food items
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Vulnerability to predation
21) Predation
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Vertebrate
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Size-selective
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Invertebrate
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Not size selective
22) Planktonic Predators
23) Cyclomorphosis
Daphnia galeata mendotae
24) Daphnia hyalina/longirostris
25) Blue-green Algal Blooms
26) Daphnia lge
27) Conclusions: Cladocera
– Key Organisms
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