Lec 19: Case Study - Microbes on a changing planet

Question 1

what are the to subcycles of the carbon cycle?

Answer 1

• rapid (biological) carbon cycle –> LIVING organisms

- long-term (geological) carbon cycle –> plate tectonics

Question 2

what is the role of microbes in the global carbon cycle?

Answer 2

microbes are hetetrophic. when they respire and decompose they release CO2.

Question 3

what is organic matter?

Answer 3

material coming from a recently living organism (dead plants and animals, their waste)

Question 4

Where is most organic matter derived from on earth?

Answer 4

plants

Question 5

Where is most organic matter derived from in the ocean?

Answer 5

phytoplankton (which are bacteria or eukaryotes)

Question 6

what is one of the major constituents of organic matter?

Answer 6

carbon

Question 7

what percentage of Earth’s organic carbon is stored in organic matter?

Answer 7

40%

Question 8

What is bioavailability of organic matter?

Answer 8

how much of the organic matter that microbes can eat

Question 9

what do we call organic matter that is most bioavailable?

Answer 9

labile

Question 10

what do we call organic matter that is least bioavailable?

Answer 10

recalcitrant

Question 11

which factors determine the bioavailability of a compound?

Answer 11

• size: smaller = easier to eat

- chemical structure (more rings = less edible)

Question 12

what are the three pools that make up organic matter

Answer 12

active, slow, and stable

Question 13

how many isotopes does carbon have? which one is radioactive?

Answer 13

3. C14 is radioactive

Question 14

which carbon signatures can you measure?

Answer 14

C13 and C14 signatures (least abundant isotopes)

Question 15

what do we use C13 values for?

Answer 15

do determine the source of carbon (land or water)

Question 16

What do we use C14 values for?

Answer 16

to date material

Question 17

What does the “you are what you ear principle” allow us to do

Answer 17

determine what an organism was eating or breathing

Question 18

how do microbes break down big pieces of organic matter?

Answer 18

with extracellular enzymes

Question 19

according to Nagissa’s study, what does organic matter degradation also depend on?

Answer 19

the types of microbes that are present and activee

Question 20

what will happen as permafrost warms?

Answer 20

microbes become active, eat organic matter, and release CO2

Question 21

what kinds of microbes are likely to become active after the thawing of the permafrost?

Answer 21

methanogens (prokaryotes)

Question 22

What are we still unsure about regarding the thawing of permafrost?

Answer 22

• don’t know how labile the organic matter in permafrost is
• don’t know how quickly microbes would degrade this organic matter
• don’t know WHICH microbes will become more active (methanogens?)

Question 23

Why are changes in microbial activity important?

Answer 23

they form the base of the food chain, therefore a change in their activity will affect the entire ecosystem