Nutrient Recylcing

Question 1

What percentage of ocean life is microbial?

Answer 1

90%

Question 2

What are the 2 major groups of prokaryotes?

Answer 2

The Eubacteria: exist in the water column and sediments

Archaea: Exist in extreme environments

Question 3

Ranking of highest to lowest bacterial cell density in different habitats

Answer 3

Estuary: 5 x 10^6
Coastal: 1-5 x 10^6
Open Ocean: 0.5-1 x 10^6
Deep Sea: 0.01 x 10^6

Question 4

How much of marine bacteria is heterotrphic?

Answer 4

90-95%

Question 5

What percentage of living carbon do heterotrophic bacteria make up

Answer 5

70%

Question 6

What percentage of living carbon do marine bacteria make up?

Answer 6

Including cyanobacteria and heterotrophic bacteria it is 95%

Question 7

Living carbon turnover in marine environment

Answer 7

20% of bacterial biomass in ocean turns over every day
This means that most living carbon in marine environment is completely turned over every 5 days
25-70 gigatonnes of Carbon annually

Question 8

Why was marine bacteria so hard to identify? And how did we first detect it?

Answer 8

Due to its small size it was very difficult to see
But in the 70’s fluorescent microscopy allowed us to see them
Later flow cytometry made this much easier

Question 9

How do oceanographers study marine bacteria?

Answer 9

Use uptake of tritiated thymide (TdR)
Incubate bacteria with TdR
Use TdR because Thymide is only in DNA not RNA
You then filter out bacteria and use fluorescence to measure uptake of TdR
This gives reproduction of heterotrophic bacteria and thus production

Question 10

How does bacterial production and growth compare to phytoplankton?

Answer 10

Bacterial production is generally 10-25% of primary production
Bacterial growth is 15% of phytoplankton growth rates

Question 11

What happens to bacteria in food web

Answer 11

Consumed by zooplankton and microzooplankton
Lysed by viruses

Question 12

What do heterotrophic marine bacteria eat

Answer 12

Mostly consume DOM

Question 13

Where does DOM come from

Answer 13

Phytoplankton exudates (DOC)
Excretory products from marine organisms
Viral lysis of host cells
Sloppy feeding
Sinking zooplankton faecal pellets

Question 14

What was Steeles dillema

Answer 14

He observed that there were too many fish, for the amount of phytoplankton production occurring

Question 15

What is the microbial loop and what is important about it

Answer 15

It is the loop of carbon/energy in marine systems facilitated by microbes

Micro food chain works within and alongside classic food chain

Key for maintaining flux of Carbon and energy

DOM is key for the functioning of the loop

Question 16

Draw the complete trophic loop in marine systems

Answer 16

REFER TO NOTES

Question 17

Ecological Roles of Marine Heterotrophic Bacteria

Answer 17

Recycling Nutrients:
Bacterial breakdown of DOC returns inorganic nutrients to the water column
Recycled nutrients used by phytoplankton

Increases overall food chain efficiency:
Microzooplankton are consumed by mesozooplankton
Provides way to channel bacterial carbon back into classic food chain

Question 18

Reminerilazation

Answer 18

breakdown or transformation of organic matter into its simplest inorganic forms

Question 19

Marine virus concentrations

Answer 19

10^7-10^11 per mL

Question 20

Where are marine viruses most abundant

Answer 20

Mostly in the upper 200m
Thats where there host cells are found
Infect heterotrophic bacteria

Question 21

Ecological Roles of Viruses in Marine Environment

Answer 21

Recycling of Nutrients (indirect):
Remineralization/respiration of lysed cell contents by bacteria
10-20% of all bacteria in euphotic zone lysed every day

Regulation of Primary production:
viral destruction of eukaryote phytoplankton, could terminate blooms

Other Roles:
Major source of mortality
Cause disease in organisms, affect community composition
Introduction of new genetic material, can drive evolution