Q: If the annual net primary production in the North Pacific Subtropical Gyre is 48.5 GtC/year and 18% is exported to the deep sea, how much carbon is exported annually?

$$48.5 \times 0.18 = 8.73$$ GtC/year

Question 1

Which of the following best describes the role of the ocean in the global carbon cycle compared to land plants and soils?

Accepted Answer

The ocean stores significantly more carbon than both land plants/soils and the atmosphere.

Question 2

Which equation correctly represents the process of photosynthesis carried out by phytoplankton in the ocean?

Accepted Answer

$$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6$ + 6O_2$$

Question 3

What is the primary method used to measure primary productivity in oligotrophic ocean regions such as the North Pacific Subtropical Gyre?

Accepted Answer

Adding $$^{14}C-$$labeled bicarbonate and measuring its incorporation into phytoplankton

Question 4

Which group of microorganisms is the dominant contributor to primary production in both the upper and lower euphotic zones of the North Pacific Subtropical Gyre?

Accepted Answer

Prochlorococcus

Question 5

The 'biological pump' in the ocean refers to:

Accepted Answer

The gravitational sinking of particulate organic carbon from the surface to the deep ocean

Question 6

If the annual net primary production in the North Pacific Subtropical Gyre is 48.5 GtC/year and 18% is exported to the deep sea, how much carbon is exported annually?

Accepted Answer

$$48.5 	imes 0.18 = 8.73$$ GtC/year

Question 7

Which of the following statements about the Keeling Curve is correct?

Accepted Answer

It records the seasonal and long-term increase in atmospheric CO$$_2 at $$Mauna Loa.

Question 8

Which of the following best explains why the e-ratio (export ratio) varies seasonally in the North Pacific Subtropical Gyre?

Accepted Answer

It reflects the decoupling between primary production and particle export, influenced by factors such as nutrient supply and community composition.

Question 9

Which of the following is a key difference between free-living and sinking particle-attached prokaryotes in the ocean?

Accepted Answer

Sinking particle-attached prokaryotes are enriched in extracellular enzymes for degrading complex carbohydrates.

Question 10

A scientist is analyzing the nitrogen isotope composition of amino acids in sinking particles. What is the most likely purpose of this analysis?

Accepted Answer

To trace the sources and transformation of organic nitrogen in the ocean

Question 11

Which of the following best describes the fate of most particulate organic carbon (POC) exported from the euphotic zone?

Accepted Answer

It is largely remineralized by microbial degradation and fragmentation as it sinks.

Question 12

Which of the following polysaccharides is commonly found in macroalgae and is a substrate for marine carbohydrate-degrading bacteria?

Accepted Answer

Alginate

Question 13

Why is Prochlorococcus particularly successful in the oligotrophic (nutrient-poor) waters of the North Pacific Subtropical Gyre?

Accepted Answer

It is highly efficient at light capture and nutrient uptake due to its small size and specialized pigments.

Question 14

Which of the following best explains the observed increase in lower euphotic zone primary production from 1989-2018 at Station ALOHA?

Accepted Answer

Increased horizontal supply of nutrients and atmospheric deposition to the region.

Question 15

Which of the following is NOT a method used in the research background for studying microbial communities in the ocean?

Accepted Answer

Direct measurement of methane emissions from hydrothermal vents

Question 16

A decrease in the export ratio (e-ratio) at Station ALOHA would most likely indicate:

Accepted Answer

A greater proportion of primary production is being remineralized in the upper ocean.

Question 17

Which of the following best describes the relationship between atmospheric CO$$_2$$ and fossil fuel burning since the 1800s?

Accepted Answer

Atmospheric CO$$_2$$ has increased sharply in parallel with fossil fuel emissions.

Question 18

Which of the following is a plausible reason for the dominance of picophytoplankton in the North Pacific Subtropical Gyre?

Accepted Answer

Low nutrient concentrations favor small, efficient cells like picophytoplankton.

Question 19

Which of the following best describes the function of extracellular enzymes produced by particle-attached prokaryotes in the ocean?

Accepted Answer

They break down complex organic molecules, such as polysaccharides, into smaller, more accessible forms.

Carbon Cycle and Microbial Processes in the North Pacific Subtropical Gyre

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