1. Lake Biota Classification by trophic level Classification by zonation
Factors affecting the distribution of aquatic organisms
Characteristic organisms for each lake zone

2. Classification by Trophic Level
Primary Producers
Produce organic material from elemental nutrients
Ex:
photosynthesis where light is used as an energy source
chemosynthesis where a chemical reaction is used as an energy source
Add reactions?

3. Consumers Decomposers Feed on primary producers or other consumers
Ex: zooplankton, fish, people
Decomposers
Convert organic material back to nutrients, e.g. mineralization
Ex: bacteria, fungi

4. Classification by Zonation
Psammolittoral zone
In the beach sand
Ex: specialized copepods, rotifers, nematodes
Limnetic, Pelagic zone
In the water
Ex: phytoplankton, zooplankton, fish

5. Benthic zone On the bottom
Epifauna – those that live and move about on the lake bottom
ex: crayfish, dragonfly larvae
Infauna – those that live beneath the mud surface
ex: nematodes, some insect larvae

6. Factors Affecting the Distribution of Aquatic Organisms
General principles
Leibig’s “Law of the Minimum”
Shelford’s “Law of Tolerance”
eurothermal – withstands a large temperature range, ex: carp
stenothermal- only withstands a small temperature range

7. Stratification Light temperature ex: refuge for daphnia chemical
ex: oxygen distribution, only certain organisms can withstand anoxia
Light
photic zone – need light for photosynthesis
photoinhibition – high levels of light, especially in the UV range, inhibits photosynthesis

8. Nature of the substrate
interstitial space – minimum space requirements
erodability
ex: macrophyte rooting
Water movement
gas and nutrient supply/replenishment
transports organisms
ex: build of up of algae downwind

9. Availability of nutrients and/or prey
ex: zooplankton migrations to graze in shallow zones
ex: blue-green algae sink to deeper, nutrient-rich water at night than float to the surface during the day for light
Species interactions
physical avoidance of predators
competition for nutrients, prey, and light

10. Characteristic Organisms for Each Lake Zone
Limnetic zone
Plankton
Phytoplankton – plant plankton
Major Groups:
Cyanophyta – Blue-green algae
Chrysophyta – Golden-yellow algae
Dinophyta – Dinoflagellates
Euglenophyta – Euglena
Chlorophyta – Green algae
Bacillariophyta – Diatoms
Cryptophyta - Cryptomonads

11. Diatoms

12. zooplankton – animal plankton
Major Groups:
Copepoda – Copepods
Diaptomus
Cladocerans
e.g. Bosmina, Daphnia, Rotifers

13. Copepods

14. Bosmina

15. Daphnia

16. Nekton – swimmers
Vertebrates
fish

17. Invertebrates
mysis shrimp

18. Littoral Zone Plants Aquatic macrophytes emergent plants cattails
rooted plants with floating leaves
lily pads
submerged vegetation
Eurasian milfoil

19. Giant Water Lilies: Victoria amazonica

20. Eurasian Milfoil at Tahoe

21. Algae – attached and free
Major groups:
Bacillariophyta - diatoms
Chlorophyta – green algae
Filamentous green algae (pond scum)
Spirogyra, which are often attached
Oedogonium
Cynanophyta - blue-green algae

22. Spirogyra, sp.

23. Attached Periphyton at Tahoe

24. Periphyton – attached algae
“aufwuches”
Epilithic periphyton
Epipelic periphyton
Epiphytic periphyton
Epizoic periphyton
defined by the zone where they are found

25. Animals Invertebrates:
snails (gastropods) and mussels (Bivalve mollusks)
damsel, mayfly, and dragonfly nymphs
rotifers
flatworms
hydra
midges
crayfish (crustaceans)
isopods
copepods
cladocerans

26. Various Macroinvertebrates

27. Burrowing organisms (infauna)
clams
annelids
snails
chironomids
Nekton
fish
diving beetles (insects)
Vertebrates
frogs, toads
salamanders
turtles
water snakes

28. Profundal zone Pleuston Bacteria and fungi are the major components
Blood worms (chironomid larvae)
Clams
Chaoborus (phantom larvae)
Pleuston
moved by the wind
floating on the surface

29. Neuston Epineuston attached to the top of the surface Hyponeuston
attached to the bottom of the surface