1. Finally, biology Ways of classifying lake organisms: phylogenetic
functional
autotrophs
heterotrophs
(herbivores, carnivores, omnivores, detritovores, mixotrophs)
chemotrophs (methane, sulfur)
mixotrophs
habitat
benthic vs. pelagic

2. Bacteria (prokaryotes)
Can fill any functional roles in lakes
Play a number of roles in food web
Defy species concept
Key questions about bacteria:
How many are there?
How do we measure their diversity?
Other prokaryotes- cyanobacteria, purple sulphur bacteria, Nitrosomas

3. Ways of counting bacteria- culturing prehistoric
Limitation- not all bacteria grow in the lab, some can’t use organic medium supplied, others are dormant
Culturing typically finds 100s-1000s of cells/ml

4. Ways of counting bacteria- staining, e. g. DAPi, FISH Azam et al
Ways of counting bacteria- staining, e.g. DAPi, FISH Azam et al Marine Ecology Progress Series 10:257
Typically finds 1,000, ,000,000cells/ml
Two possibilities:
1. All those glowing cells are dead or dormant (culturing is correct)
2. Most bacteria can’t be cultured in the lab (staining is correct)

5. How much do bacteria contribute to biomass. Gasol et al
How much do bacteria contribute to biomass? Gasol et al Limnology and Oceanography 42:1353

6. Ways of measuring bacterial diversity- Ancient (1970s): culturing and morphological diversity

7. Ways of measuring bacterial diversity- 1980’s: use of different organic resources, Biolog plates
Functional diversity

8. Measuring bacterial diversity- Modern: PCR to amplify, gels to separate (DGGE) and sequencing

9. What determines bacterial diversity in BC lakes
What determines bacterial diversity in BC lakes? Longmuir, Shurin and Clasen 2007 Ecology 88:1663
Light
Dissolved O2
How is bacterial richness related
to zooplankton and phytoplankton richness?

10. What determines bacterial diversity in BC lakes
What determines bacterial diversity in BC lakes? Longmuir, Shurin and Clasen 2007 Ecology 88:1663

11. Bacteria, zooplankton and algae
biomass are positively related
slope <1, heterotrophs don’t keep up with autotrophs
diversity unrelated
determined by different processes

12. What ecological roles to bacteria play?
Interactions with phytoplankton
predators (pathogens)
compete for nutrients (autotrophs)
recycle nutrients (heterotrophs)
Interactions with zooplankton
pathogens
prey
Recycling detritus (POM -> DOM)

13. Bacteria and nutrient cycles- the microbial loop

14. Biology 302 revisited- the food chain
classical food chain

15. The brown world- death and decay
classical food chain
everything dies, becomes detritus

16. The central role of bacteria
classical food chain
but wait, there is recycling
everything dies, becomes detritus

17. Closing the loop 1- Ecology is about recycling
classical food chain
but wait, there is recycling
inorganic
nutrients
(N,P,DIC)
everything dies, becomes detritus

18. Closing the loop 2- Feeding the beast
classical food chain
but wait, there is recycling
inorganic
nutrients
(N,P,DIC)
everything dies, becomes detritus

19. How much zooplankton carbon comes from bacteria vs. phytoplankton?
Using stable isotopes of Carbon (13C and 12C)
to measure bactivory
consumer
prey 1
prey 2
Percent 13C in tissues

20. How much zooplankton carbon comes from bacteria vs. phytoplankton?
If Daphnia eats 50% algae, 50% bacteria, it will have
13C concentration half way between the two
Daphnia 5%
bacteria 2%
phytoplankton 8%
Percent 13C in tissues

21. How much zooplankton carbon comes from bacteria vs. phytoplankton?
If Daphnia eats 90% algae, 10% bacteria, it will have
13C concentration that is
0.9*[algae]+0.1*[bacteria] = .074
Daphnia
7.4%
bacteria 2%
phytoplankton 8%
Percent 13C in tissues

22. How much zooplankton carbon comes from bacteria vs. phytoplankton?
Grey et al Limnology and Oceanography 46:505
50% averaged over the year, 80-90% in winter, 10-20% in summer

23. How much zooplankton carbon comes from bacteria vs. phytoplankton?
Pace et al Nature 427:240
added NaH13CO3 (radio labeled DIC)
DIC can be used by phytoplankton but not bacteria
Measured 13C in POM and Daphnia
Accumulation of 13C in Daphnia indicates amount of bacteria eaten
20-50% in summer

24. How do infectious diseases influence Daphnia reproduction
How do infectious diseases influence Daphnia reproduction? Decaestecker et al Oecologia 144: 382
4 fungi
1 amoeba
2 bacteria
1 nematode

25. How does zooplankton diversity influence disease transmission
How does zooplankton diversity influence disease transmission? Hall et al. Ecology 2009
Daphnia species

26. How does zooplankton diversity influence disease transmission
How does zooplankton diversity influence disease transmission? Hall et al. Ecology 2009
more susceptible hosts
less susceptible hosts

27. How does zooplankton diversity influence disease transmission
How does zooplankton diversity influence disease transmission? Hall et al. Ecology 2009
high zooplankton diversity lowers transmission- less susceptible
competitors can benefit one another

28. Bacteria and disease- cholera Pascual et al. 2000 Science 289: 1766

29. Vibrio cholerae (cause of cholera) has zooplankton as intermediate host
attached to Daphnia
in gut of Daphnia
Do high plankton populations in El Niňo years
cause cholera outbreaks?

30. How do bacteria get energy?
Autotrohs (cyanobacteria)
Heterotrophs (DOC)
Inorganic chemotrophs (purple sulfur bacteria, methanotrophs)

31. What do parasites do in ecosystems? Kuris et al. Nature 2008

32. What do parasites do in ecosystems? Kuris et al. Nature 2008

33. Chemical communication in bacteria
allelopathy (chemical warfare)
quorum sensing (switch between dormant and active stages)

34. Mutualism between bacteria and phytoplankton

35. What about viruses? (Suttle 2005 Nature 437:356)

36. Viruses and you (Suttle 2005 Nature 437:356)

37. Viruses rule the world Suttle et al. 1990 Nature 347:467
no viruses
per ml
Reduce algal production by up to 78% (in cultures)
viruses
viruses are in the
micron size class

38. What determines viral abundance. Jessie Clasen et al
What determines viral abundance? Jessie Clasen et al Freshwater Biology 53: 1090
Same things that determine algal and bacterial abundance,
but things work differently in lakes and the ocean