Deck 11: Processes in the Water Column

Question 1

A phytoplankton bloom at a site will likely occur

A) If water turbulence is very strong there
B) If nutrients are abundant and water turbulence is minimal
C) If nutrients are low but inorganic particle density is very high
D) All of the above

Answer 1

B

Question 2

Plankton may be concentrated

A) At the thermocline
B) At convergences near the surface
C) In quiet bays with little turbulence
D) All of the above

Answer 2

D

Question 3

The Spring diatom increase

A) Reaches its peak of biomass at the time of day length is longest
B) Reaches its peak of biomass after the time of day length is longest
C) Attains a maximum of biomass when nutrients are still very concentrated in the surface waters
D) Does not end because of reduced day length

Answer 3

D

Question 4

At the compensation depth

A) Phytoplankton oxygen production per cell equals cell respiration
B) Total phytoplankton oxygen production in the water column equals total respiration
C) Phytoplankton cells are stationary in position
D) There is no light present

Question 5

A phytoplankton bloom will begin to increase if the mixing depth

A) Is greater than the critical depth
B) Is equal to the critical depth
C) Is less than the critical depth
D) Is less than the compensation depth

Question 6

The classic Sverdrup model of the initiation of a phytoplankton bloom has been criticized because

A) Phytoplankton have been found to mainly bloom in the summer
B) When the phytoplankton bloom begins, the water column is surprisingly cold and vertically mixed
C) Measures of the mixing depth show that is actually gets deeper as the spring progress.
D) Nutrients have been found to be more limiting in winter surface waters than previously supposed.

Question 7

In the temperate zone, toward the end of the spring

A) The water column becomes more stable vertically
B) The water column becomes less stable vertically
C) Mixing from below brings bottom nutrients toward the surface
D) The phytoplankton begin a secondary early summer increase

Question 8

Benthic-planktonic coupling

A) Occurs only in the deep sea
B) Is restricted to waters where a strong thermocline is permanent
C) Is correlated with the development of an isothermal water column
D) Can only occur when wind action is nil

Question 9

In turbid nearshore ocean waters

A) Light penetration is at wave lengths that are shorter than for the open sea
B) Light penetration is deeper than in the open sea
C) Light penetration is greatest at the far red end of the spectrum
D) Light penetration is at visible wave lengths that are longer than for the open sea

Question 10

Grazing by zooplankton

A) Is always the reason for the demise of the spring diatom increase
B) Is independent of phytoplankton density
C) Never affects the phytoplankton
D) Has variable effects on phytoplankton, depending on differing conditions

Question 11

Marine snow

A) Forms only in Antarctic waters
B) Is formed only in tropical clear ocean waters
C) Is extremely pure particulate organic matter
D) Is found throughout the ocean water column

Question 12

Auxotrophic phytoplankton

A) Require only inorganic nutrients to grow
B) Depend upon dissolved organic matter alone for nutrient uptake
C) Probably can grow only in the presence of other living organisms in the water column
D) Appear very early in the spring phytoplankton bloom

Question 13

Nitrogen is usually taken up the fastest by phytoplankton in the form of

A) Nitrite
B) Ammonium
C) Nitrate
D) Dissolved amino acids

Question 14

Nitrogen

A) Is mainly controlled by the breakdown of organic particles
B) Is mainly controlled in the ocean by different types of bacteria
C) Rarely limits phytoplankton growth
D) Is decreasing in estuaries in recent decades

Question 15

Nitrogen

A) Tends to exchange less rapidly than phosphorus between phytoplankton and the water
B) Tends to exchange more rapidly than phosphorus between phytoplankton and the water
C) Is never limiting during the phytoplankton season
D) Only occurs in one form at a time in the water column

Question 16

In contrast to phosphorous, nitrogen

A) Is only limiting in estuaries
B) Is strongly controlled by microbial processes
C) Is a major factor in energy metabolism in phytoplankton cells
D) Is very insoluble in sea water

Question 17

In the tropical gyre centers

A) Nitrogen often comes mainly from excretion processes
B) Nitrogen is supplied mainly on windless days from regeneration across the thermocline
C) Nitrogen mainly circulates in the form of nitrate
D) Nitrogen is surprisingly abundant

Question 18

In the sea the nitrogen:phosphorus ratio

A) Varies greatly between phytoplankton and the water column
B) Varies strongly between winter and summer
C) Of phytoplankton resembles that of the water column
D) Is strictly constant at 1:15

Question 19

In the water column

A) Bacteria consume far more dissolved nutrients than do phytoplankton
B) Bacteria are consumed mainly by larger zooplankton
C) Bacteria are consumed by protozoans, which provides a link to the rest
D) All of the above

Question 20

In phytoplankton in offshore waters

A) We would expect phytoplankton to be relatively inefficient at nutrient uptake
B) We would expect saturation of nutrient uptake at nutrient concentrations higher than for inshore forms
C) Only nitrate can be taken up
D) We would expect saturation of nutrient uptake at nutrient concentrations lower than for inshore forms

Question 21

For phytoplankton,

A) Light is captured by chlorophyll only in the infrared
B) The entire visible spectrum of wavelengths is captured by chlorophyll
C) A wide spectrum of visible light is captured by chlorophyll along with other light-harvesting pigments
D) Light penetrates to several thousand meters, allowing phytoplankton cells to live there

Question 22

Transparent exopolymers

A) Are secreted by zooplankton to attract prey
B) Cause dissolved nutrients to stick together and increase nutrient uptake
C) Are secreted by phytoplankton cells
D) Arise mainly in gyre centers

Question 23

Iron is often limiting

A) At the heads of estuaries
B) In areas remote from continents
C) Toward the end of an estuarine phytoplankton bloom
D) To diatoms but not cyanobacteria

Question 24

Nuisance blooms

A) Have become more frequent in recent years
B) Are dominated by dinoflagellates only
C) Are dominated by phytoplankton that lack resting stages
D) Are only associated with turbulent and well mixed water columns

Question 25

Toxic algal blooms

A) Have only been observed in species of dinoflagellates
B) Are always characterized by red colored waters
C) Have been observed in some species of diatoms
D) Have been observed in floating green seaweeds off of Japan

Question 26

Phytoplankton living in offshore low nutrient conditions

A) Are expected to have high values of K
B) Are expected to have low values of K
C) Will always be limited by silica
D) Will be swept onshore at the end of the phytoplankton season

Question 27

Zooplankton grazing

A) Is not required for a Spring diatom increase to end
B) May produce alternate areas of abundant and less abundant phytoplankton
C) Can fail to increase beyond an upper limit of phytoplankton cell concentration
D) All of the above

Question 28

Phytoplankton species that appear early in succession are likely to be

A) Autotrophic
B) Auxotrophic
C) Heterotrophic
D) Mixotrophic

Question 29

The presence of a microbial loop is important because

A) It means that microbes are very abundant
B) It means that microbes are incorporated into most planktonic food chains
C) Microbes will poison species in the water column
D) None of the above