LEC 26 - BACT PTON

Question 1

what is a bacteria for our purposes?

Answer 1

“bacteria” refers to heterotrophs that decompose organic matter that prod CO2

Question 2

what are some problems associated with the traditional view of bact abundance and ppton abundance?

Answer 2

traditionally, it was thought that, since there was a [+] correlation bw bact and ppton abundance, heterotroph microbes controlled algal productivity.
in other words, it was very linear:
nutrients –> ppton –> microbes

problems:
- heterotroph bact depend on carbon prod by algae
- catchment inputs aren’t considered (all in lake nutrients)
- P is definitely important for algae, but not for algae

Question 3

ok so lets compare algal-bact interactions in diff nutrient environs

Answer 3

in eu systems:
- P is high (ppton high)
- alloch C is relatively low (bact low)
–> ppton > bact

in oligo systems:
- P is low (ppton is low)
- alloch C is relatively high (bact high)
–> ppton < bact

graph is on slide 9, where phytoC is ppton biomass and BoC is bact biomass

Question 4

if the classical view is not correct, what do algal-bact interactions look like?

Answer 4

algae and bact do both need P, but algae is just better at soaking it up.

C inputs regulate bact, and external factors influence both bact and algae

Question 5

what are bacteria’s three roles in FW systems?

Answer 5

1. nutrient regeneration: organic nutrient form to inorganic (ammonification, phosphatase and generation of orthophos, etc)
2. ‘links’ to higher trophic levels: scavenging organic carbon, breaking it downand providing an alternate pathway for organic carbon to get into the food web
3. ‘energy dead ends’: organic carbon gets turned to inorganic C through respiration - exits the C cycle

Question 6

what are some forms of detrital carbon that microbes most often use?

Answer 6

• cell death/lysis
• sloppy feeding
• unbalanced photosynth (sometimes when theres not enough nutrients but theres enough inorganic carbon, photosynth will still continue so the system doesnt shut down)

Question 7

what is bacteria growth efficiency? what is its relevance?

Answer 7

bact growth efficiency =
(production of biomass) /
(prod of biomass + resp)

aka BP / (BP + BR)

ie BGE tells us, of the energy consumed, how much is devoted to growth

(what we end up seeing is that energy transfer is really ineffiecient - in a sense, a dead end)

Question 8

bacteria produce biomass. is more entering the C cycle, or is more leaving through the production of CO2?

Answer 8

more is always entering into the cycle first, since

Question 9

we’ve looked at the microbial loop and the importance of bacteria. forgive me - what was this importance again?

Answer 9

shunt energy to higher trophic levels

bacteria scavenge organic carbon (heterotrophic microbes), providing a new pathway for organic carbon to be taken up