Chapter 3: Microbial Ecology

Question 1

During trophic transfer, what happens with the energy/biomass lost?

Answer 1

• Most parts are respired and remineralized (recycled) to inorganic forms of C,N,P
• this source of energy and nutrients is what allows new production

Question 2

how does remineralization occur?

Answer 2

• breakdown of OM by decomposers

- decomposers produce CO2 ammonium and phospate

Question 3

describe decomposition

Answer 3

the conversion of insoluble OM into smaller molecules by enzymatic reactions of digestion, and subsequent metabolism

Question 4

marine detritus

Answer 4

• consists partly of the leftovers from feeding
• varies in biological dynamics
• low quality food source for lager organisms, but utilized by microorganisms

Question 5

the difference between DOM and POM

Answer 5

DOM:
-0.2-1um
-DOC(dissolved organic carbon) larges pool of OM in the sea, large fraction resistant to decay.
POM:
-larger than 1um
-consists of living and non-living material
-marine snow caused by collisions of transparent exopolymer particles

Question 6

how does detritus recycling compare to primary producers?

Answer 6

• recycling OM can be taken up several times by the same food web
• OM utilized by the food web is larger than what is produced by the primary producers

Question 7

how much OM is recycled each cycle?

Answer 7

~50%

Question 8

the microbial food web consists of which types of organisms?

Answer 8

virus, bacteria, algae, protozoa, and small larval zooplankton

Question 9

why aren’t virus classified as living?

Answer 9

• lack a cell wall

- incapable of reproduction w/o the aid of host DNA

Question 10

what are the two particular groups of interest of bacteria?

Answer 10

Organotrophs: heterotrophs that utilize OM, organic detritus, and breaking down all natural materials.
Chaemoautotrophic nitrifying bacteria: use CO2 and inorganic nutrients. some oxidizes ammonia to nitrite and some nitrite to nitrite.

Question 11

what type of ‘troph is algae classified?

Answer 11

photoautotroph

Question 12

what are the two main types of protozoa, and what classifies them?

Answer 12

Heterotrophic nanoflagellates
-bacterivores
-2-20um
-flagellated for movement and food capture
-autotrophic, mixotrophic, heterotrophic.
Microzooplankton protists
-20-200um
-include ciliates and larger dinoflagellates
-mostly heterotrophs that prey on phytoplanktons and bacteria

Question 13

As bacteria are quick-growing, but also quick to be eaten, what are the two methods to obtain field estimates of bacterial growth?

Answer 13

• DNA method

- Protein method

Question 14

describe the ‘DNA’ method of estimating microbial growth

Answer 14

• measures the rate of thymidine infused seawater are incorporated into bacterial DNA
• incubation, filtered samples, DNA extracted, radioactivity measured. able to estimate thymidine content.

Question 15

describe the protein method of estimating microbial growth

Answer 15

• measures leucine in synthesized protein.

- measures production of biomass directly, while DNA method measures the rate at which cells are produced.

Question 16

what are the key growth regulating mechanisms for micro-organisms?

Answer 16

grazing, resource limitation, virus attacks

Question 17

what is the relationship between bacteria and predatory protozoans?

Answer 17

predators populations have growth rates relatively close to that of bacteria, so they are able to respond to the numerically fluctuations of their prey. They are more capable of controlling prey populations than in the phytoplankton/mesozooplankton relationship

Question 18

what percentage of bacterial mortality is due to viruses? protozoans?

Answer 18

V: 5-40%
P: 5-65%

Question 19

photosynthesis and ________ are linked processes in the ecosystem

Answer 19

respiration

Question 20

Photosynthesis provides ___________ for respiration

Answer 20

organic material

Question 21

respiration reduces organic material into ____________ required for _________.

Answer 21

inorganic nutrients

photosynthesis

Question 22

P and R are not necessarily in phase with each other, and the difference (P-R) si the ______

Answer 22

net community production (NCP)

Question 23

the NCP rate is perhaps the most important measure of plankton systems as it is the basis for ________________

Answer 23

interpreting the dynamics of such systems

Question 24

describe the basic seasonal cycle of the plankton

Answer 24

spring: development of spring phytoplankton bloom
late spring/early summer: demise of the phytoplankton bloom
summer: recycling
autumn/winter: regenerative period

Question 25

describe the spring phase

Answer 25

• stratification begins (shallowing of mixed layer, deepening of critical depth)
• explosive growth phase of phytoplankton
• release of organic detritus, results in bacterial growth and energy flux in microbes
• • net community production

Question 26

describe late spring/early summer phase

Answer 26

• grazer community established, more growth in heterotroph community
• main players are bacteria, heterotroph nanoflagellates, and microzooplankton
• net community production falls, becomes negative
• limited nutrient availability due to grazers

Question 27

describe summer phase

Answer 27

• importance of recycled nutrients increase
• system more balanced w/ P and R as dominant groups
• predators better control their prey
• prey pops reduced, growth in predators
• similar to tropic plankton communities

Question 28

describe autumn/winter period

Answer 28

• thermal strat weakens, decreased phytoplankton activity
• heterotrophs consume OM available as detritus
• nutrients recycle to inorganic forms
• dominated by heterotroph activity, negative NCP

Question 29

what endows microorganisms with extrodinarily high metabolic rates?

Answer 29

small size and large surface-to-volume ratio

Question 30

the utilization of ‘waste’ organic detritus by the micro-organisms provides the basis of a ______________ that originates from __________

Answer 30

second food chain

marine bacteria

Question 31

what is a common nitrogenous waste product of heterotrophic metabolism?

Answer 31

ammonium