Ecosystem Ecology of Lakes

Question 1

What are the 4 properties of Ecosystems?

Answer 1

• Thermodynamically open
• Hierarchically organized
• Include biotic and abiotic factors
• Flow of energy and circulation of materials

Question 2

What are pools and fluxes?

Answer 2

They are the key features of ecosystems
* Pools
○ standing stocks and rates of production
○ For example different trophic levels
* Fluxes
○ movement of energy and materials among pools
For example carbon flux

Question 3

There are 4 ecological currencies, name 2

Answer 3

Ecological currencies
* Evolution
○ Examples: change in gene & fitness
* Population
○ Example: size
* Communities
○ Examples: Trophic levels, interactions, size, & biomass
* Ecosystem
○ Examples: Energy and Biomass

Question 4

What is difference between standing stocks and rates?

Answer 4

Standing stocks (in a lake)
- How much is there now (biomass)
Rates
- How much change over time (production)

Question 5

Arrange trophic levels (Primary producers, herbivores, predators, top predators, and decomposers) in which has the largest biomass.

Answer 5

1. Primary producers (800 g/m^2)
2. Herbivores (50 g/m^2)
3. Predators (25 g/m^2)
4. Top predators and decomposers (10 g/m^2)

Question 6

Arrange trophic levels (Primary producers, herbivores, predators, top predators, and decomposers) in which has the largest production.

Answer 6

1. Primary producers (35,000 kcal/m^2/y)
2. Decomposers (10,000 kcal/m^2/y)
3. Herbivores (5,000 kcal/m^2/y)
4. Predators 1,000 kcal/m^2/y)
5. Top predators (500 kcal/m^2/y)

Question 7

Arrange trophic levels (Primary producers, herbivores, predators, top predators, and decomposers) in which has the production to biomass ratio.

Answer 7

1. Decomposers (1,000 kcal/m^2/y)
2. Herbivores (100 kcal/m^2/y)
3. Predators (70 kcal/m^2/y)
4. Primary producers (50 kcal/m^2/y)
5. Top predators (30 kcal/m^2/y)

Question 8

What does carbon budget in a lake include? Name at least 2.

Answer 8

A lake’s carbon budget includes the following factors:

Carbon burial: Organic carbon from recently living organisms sinks to the bottom of the lake and becomes buried in sediments. A 2020 study found that lakes have tripled the amount of carbon they bury over the last 100 years.

Carbon emissions: Carbon is re-emitted back into the atmosphere from lakes. Carbon dioxide (CO2) emissions from lakes are estimated to be around 530 Tg carbon per year.

Carbon sequestration: Carbon is sequestered along the land-ocean aquatic continuum, mainly in sediments.

Carbon transport: Carbon is transported downstream.

Carbon mineralization: Organic carbon is mineralized to calcium carbonate, CO2, or CH4.

Question 9

What is the primary driver of lake succession?

Answer 9

The primary driver of lake successions is sedimentation.

Question 10

What is net primary production (NPP) in different lakes? (from low to high) You have to include: Groundwater, wetland, and lakes.

Answer 10

Low

Groundwater
Wetlands
Lakes

High

Question 11

What is the turnover time (how much time it takes to replace the water in the system) in different lakes? (from months to centuries) You have to include: Groundwater, wetland, small lakes, and big lakes.

Answer 11

months

Small lakes
Wetlands
Large lakes
Groundwater

centuries

Question 12

What is the spatial linkages (allochthonous C input, nutrient input, and terrestrial influence) in different lakes? (from low to high) You have to include: Groundwater, wetland, small lakes, and big lakes.

Answer 12

low

Groundwater
Big lakes
Small lakes
Wetlands

high