Lecture 11

Question 1

What nutrients are essential for algal growth?

Answer 1

Nitrogen (N), phosphorus (P), silica (Si), and sometimes iron (Fe).

Question 2

What is Liebig’s Law of the Minimum?

Answer 2

Growth is limited by the nutrient present in the lowest concentration relative to requirements.

Question 3

What is co-limitation?

Answer 3

When multiple nutrients simultaneously limit growth.

Question 4

What is the Michaelis-Menten uptake model?

Answer 4

A model describing nutrient uptake rates as dependent on nutrient concentration and a half-saturation constant.

Question 5

How does light interact with nutrient availability in algal growth?

Answer 5

Surface layers receive more light but may have nutrient depletion, while deeper layers have more nutrients but less light.

Question 6

What is the Redfield Ratio and why is it important?

Answer 6

The Redfield Ratio (N:P = 16:1) is a rule of thumb indicating the limiting nutrient in aquatic systems. A ratio higher than 7 suggests phosphorus limitation, while lower indicates nitrogen limitation.

Question 7

Which nutrients are typically limiting in marine and freshwater environments?

Answer 7

Phosphorus is usually the limiting factor in marine environments, while nitrogen is more commonly limiting in freshwater systems.

Question 8

What role does silicon play in nutrient limitation?

Answer 8

Silicon is essential for diatoms, as it forms their skeletons. Coastal development and water depth can cause silicon limitation.

Question 9

What happens during a diatom bloom in terms of chlorophyll-a and silicon?

Answer 9

There is typically a negative correlation: as diatoms grow and use silicon, chlorophyll-a levels deplete.

Question 10

What is co-limitation at the community level?

Answer 10

Co-limitation occurs when different algae species are limited by different nutrients. Adding either nutrient can increase overall algal biomass.

Question 11

What is biochemical limitation?

Answer 11

Biochemical limitation occurs when essential elements for nutrient uptake are lacking, such as iron for photosynthetic machinery.

Question 12

What is the role of phosphorus in living organisms?

Answer 12

Phosphorus is crucial for ATP production, DNA/RNA structures, and cell membranes, making it essential for energy metabolism.

Question 13

Why is phosphorus often found in fertilizers?

Answer 13

Phosphorus is a key nutrient for plant growth, commonly added to increase productivity in agriculture.

Question 14

How does water flow affect nutrient load transport?

Answer 14

Nitrogen, being dissolved, is proportional to water flow, while phosphorus (often particulate) is transported mainly during high-flow events like floods.

Question 15

What is grazing “G” in ecological models?

Answer 15

Grazing represents zooplankton consumption of algae and is often modeled using Lotka-Volterra equations where zooplankton biomass influences grazing intensity.

Question 16

How does temperature influence grazing?

Answer 16

Grazing rates are often proportional to temperature due to its effect on metabolic rates.

Question 17

Why is phosphorus cycling considered slow?

Answer 17

Phosphorus has no gas phase and is mainly stored in sedimentary deposits, making its cycle slower compared to nitrogen.

Question 18

What is the significance of adsorption in phosphorus availability?

Answer 18

Phosphorus binds to particles like clays or forms complexes with metal ions. Adsorbed phosphorus can become bioavailable under certain conditions (e.g., low oxygen).

Question 19

What are common sources of phosphorus loads in aquatic systems?

Answer 19

Sources include agricultural runoff, wastewater, industrial discharge, and internal loading from sediment release.

Question 20

How does internal phosphorus loading occur?

Answer 20

Internal loading happens when phosphorus is released from sediments due to factors like low oxygen (anoxia), turbulence, or bioturbation.

Question 21

What is co-limitation due to synergistic effects?

Answer 21

This occurs when the addition of one nutrient enhances the uptake of another limiting nutrient, improving growth.

Question 22

How does grazing overlap between water-quality and fishery models?

Answer 22

Zooplankton grazing impacts both algae biomass (water quality) and fish production, making it essential to couple these models.

Question 23

what’s the limiting factor?

Answer 23

nitrogen

Question 24

what’s the limiting factor?

Answer 24

phosphorus

Question 25

what’s the limiting factor?

Answer 25

Question 26

what’s the limiting factor?

Answer 26