Bacteria

Question 1

What type of cell is a bacteria?

Answer 1

Prokaryotes
Membrane bound with no organelles

Question 2

What technique made it possible to estimate bacterial concentrations

Answer 2

Epifluorecent microscopy

Question 3

Most oceanic bacteria are heterotrophs, what are they eating?

Answer 3

• Carbon!
• Bacteria feed on DOC from phytoplankton (respiration)
• Bacterial abundance will increase with phytoplankton abundance

Question 4

What is remineralization

Answer 4

Taking organic matter and turning it into inorganic matter (mineral form)
Ex:
DOC —> CO2
DON —> NH4+
DOP —> PO4^-3

Question 5

Describe phytoplankton-bacterial coupling

Answer 5

• Phytoplankton produce organic matter via photosynthesis
• Bacteria consume the DOM released by phytoplankton
• Bacteria remineralize organic matter (ammonium (NH4+), phosphate (PO4 ^-3) etc.) providing nutrients that phytoplankton need to grow

Question 6

What increases the rate of bacteria remineralization?

Answer 6

Temperature

Question 7

What increases the rate of bacterial growth (respiration)?

Answer 7

Temperature

Question 8

What is labile organic matter?

Answer 8

• Bioavailable/decays fast (seconds old)
• Larger molecules
• Surface ocean
• Near Redfield ratio (106:16:1)

Question 9

What is refractory organic matter?

Answer 9

• Resilient to degradation (thousands of years old)
• Smaller molecules
• Deep ocean

Question 10

How do bacteria degrade large organic compounds?

Answer 10

Ectoenzymes located on the surface break down large complex molecules for bacteria to take in

Question 11

What is autochthonous?

Answer 11

Generated in the ecosystem (ex: phytoplankton)

Question 12

What is allochthonous?

Answer 12

External, introduced from the land

Question 13

Net autotrophic

Answer 13

Phytoplankton C production exceeds bacterial community respiration (oxygen is produced)
Only autochthonous C is supported

Question 14

Net heterotrophic

Answer 14

Bacterial community respiration exceeds phytoplankton C production (oxygen is consumed)
* Large allochthonous contribution*

Question 15

What is marine snow?

Answer 15

• Sinking organic matter
• Will be highly colonized by bacteria
• Production from bacteria feeds into pelagic food web

Question 16

What are the four different zones of the ocean?

Answer 16

• Epipelagic (0-200m)
• Mesopelagic (200-1000m)
• Bathypelagic (1000-4000m)
• Abyssopelagic (4000-6000m)

Question 17

Where is the euphotic zone?

Answer 17

Epipelagic

Question 18

Where is the aphotic zone?

Answer 18

Mesopelagic and below

Question 19

Where do bacteria dominate in the ocean?

Answer 19

The aphotic zone (top of the mesopelagic)

Question 20

Describe the epipelagic zone?

Answer 20

• Only zone with photosynthesis
• Phytoplankton processes dominate
• O2 = high
• Nutrients = low
• Organic matter = produced

Question 21

Describe the top of the mesopelagic?

Answer 21

• Aphotic
• Flux of labile organic matter from above
• Remineralization dominates
• O2 = consumed
• Organic matter = consumed
• Nutrients = regenerated

Question 22

Describe the bottom of the mesopelagic?

Answer 22

• High quality and quantity of organic matter consumed
• Bacterial respiration/O2 consumption slows

Question 23

Describe the bathypelagic?

Answer 23

• All labile organic matter gone
• Horizontal mixing dominates over biological processes

Question 24

What causes hypoxia in the ocean?

Answer 24

• The ideal gas law: PV=nRT
• As temperature goes up dissolved gas concentrations go down

Question 25

What are processes that contribute to hypoxia?

Answer 25

- Warm temperatures - Stratification - Increased bacterial growth (respiration) - Nitrogen loading

Question 26

Where is the OMZ located?

Answer 26

Top of the mesopelagic (200-1000m) *Why?*

Question 27

How does a dead zone form?

Answer 27

- Excess nutrients enter the water from agricultural runoff, sewage etc. resulting in a phytoplankton bloom - The bloom will eventually die off and the dead phytoplankton will sink to the bottom - The DOC fuels bacterial growth (respiration) using up O2 in the process - Sustained phytoplankton decomposition results in hypoxia (ex: Gulf of Mexico from Mississippi River runoff - the higher the river runoff the larger the dead zone)

Question 28

As hypoxia increases what happens to fishery yields?

Answer 28

As hypoxia increases, fishery yields decrease

Question 29

What can occur as a result of hypoxia?

Answer 29

Ocean acidification *Increase in CO2 leads to low PH*

Question 30

What is the ocean conveyor belt?

Answer 30

Cold water + ice formation exudes salt making ocean water dense (sink)

Question 31

Do algal blooms drive a high or low PH?

Answer 31

High *Why?*

Question 32

Does bacterial respiration drive a high or low PH?

Answer 32

Low (acidification) *Why?*

Question 33

Describe diurnal gasification and acidification

Answer 33

- Day: photosynthesis dominates (DO and PH = high) - Night: bacterial respiration dominates (DO and = PH low)

Question 34

What is ammonification?

Answer 34

DON ---> NH4

Question 35

What is denitrification?

Answer 35

NO3 ---> N2

Question 36

What is nitrification?

Answer 36

NH4 ---> NH2OH ---> NO2 ---> NO3

Question 37

How can bacteria be a source or sink for N?

Answer 37

- When C:N ratio of organic matter is low, more N is remineralized (bacterial growth efficiency is maximum) - When C:N ratio of organic matter is high, more N is taken up