Q: Which equation best represents the change in phytoplankton concentration over time in a physical-biogeochemical model?

$$\frac{dP}{dt} = \text{rateUptake} - \text{Grazing} - \text{Mortality}$$

Question 1

Which of the following best describes a 'bottom-up' control in marine food webs?

Accepted Answer

Environmental factors such as nutrient input drive changes in primary production, which propagate up the food web.

Question 2

In the context of food web analysis, what is the primary function of a 'state variable' in a biogeochemical model?

Accepted Answer

It quantifies the concentration of a component (e.g., nitrogen, phytoplankton) in the ecosystem.

Question 3

Which equation best represents the change in phytoplankton concentration over time in a physical-biogeochemical model?

Accepted Answer

$$\frac{dP}{dt} = 	ext{rateUptake} - 	ext{Grazing} - 	ext{Mortality}$$

Question 4

A 'wasp-waist' ecosystem is characterized by:

Accepted Answer

A single or few intermediate trophic species dominate, influencing both higher and lower trophic levels.

Question 5

Which of the following is a justification for studying biological oceanography?

Accepted Answer

To understand how plankton produce half of Earth's oxygen.

Question 6

In a top-down controlled food web, what type of correlation would you expect between adjacent trophic levels?

Accepted Answer

Negative correlation.

Question 7

Which of the following best explains the role of krill in the Western Antarctic Peninsula food web?

Accepted Answer

Krill serve as a central trophic link, transferring energy from phytoplankton to higher trophic levels such as penguins and seals.

Question 8

Which of the following is a plausible consequence of climate change on marine food webs?

Accepted Answer

Altered recruitment levels of key species such as krill, affecting higher trophic levels.

Question 9

Which method is most appropriate for quantifying the diet composition of a marine species using molecular techniques?

Accepted Answer

Gut content barcoding.

Question 10

In a biogeochemical model, which parameter reflects the half-saturation constant for phytoplankton nutrient uptake?

Accepted Answer

$$K_p$$

Question 11

Which of the following statements about energy transfer in marine food webs is correct?

Accepted Answer

Energy is lost at each trophic transfer, often as heat or waste.

Question 12

Which of the following is a key difference between mechanistic and mass-balance (e.g., Ecopath) food web models?

Accepted Answer

Mechanistic models use differential equations to describe functional relationships, while mass-balance models focus on energy or mass flows without specifying mechanisms.

Question 13

A regime shift in a marine ecosystem is most likely to occur when:

Accepted Answer

Intermediate trophic levels are dominated by a single species with a complex life history, leading to unstable feedback loops.

Question 14

Which of the following best describes the 'Oscillating Control Hypothesis' in food web dynamics?

Accepted Answer

Control alternates between top-down and bottom-up regulation depending on environmental conditions.

Question 15

If summer chlorophyll-a concentrations increase in the Western Antarctic Peninsula, what is the most likely effect on krill recruitment?

Accepted Answer

Krill recruitment will increase, as more food is available for larval krill.

Question 16

Which of the following is NOT a plausible reason for the intrinsic worth of the ocean?

Accepted Answer

It prevents all environmental change.

Question 17

Which of the following is a direct effect of increased fishing pressure in a top-down controlled marine food web?

Accepted Answer

Increase in populations of lower trophic level organisms due to removal of predators.

Question 18

In a concentration-based biogeochemical model, which of the following is a transfer function?

Accepted Answer

The equation describing how zooplankton graze on phytoplankton.

Question 19

Which of the following best describes the role of physical-biogeochemical models in food web analysis?

Accepted Answer

They use differential equations to simulate changes in state variables over time.

Question 20

Which of the following is a plausible outcome of unstable feedback loops in a wasp-waist ecosystem?

Accepted Answer

Regime shifts, where the ecosystem rapidly changes state.

Biological Oceanography: Food Webs

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