Energy Flow and Trophic Levels in Marine Ecosystems

What is the source of energy to an ecosystem?

Sunlight, captured by producers through photosynthesis and spread through trophic levels.

How does energy change form in an ecosystem?

Energy is converted into mechanical and thermal energy and ultimately dissipated.

What is a trophic level? Give an example for the first 4 levels.

A trophic level is an organism's position in the food chain. Examples: Producer - phytoplankton, Primary consumer - zooplankton, Secondary consumer - small fish, Tertiary consumer - larger predatory fish.

How does a food chain differ from a food web?

A food chain is a linear sequence of what eats what, while a food web is more complex with multiple feeding relationships.

Approximately how much energy is transferred to the next higher trophic level? Why is this energy transfer so inefficient?

About 10% is transferred; most energy is lost as heat through metabolism and unconsumed material.

How does the biomass of organisms and number of organisms change with trophic level?

Both biomass and number of organisms decrease with each higher trophic level.

What is the most important 2nd trophic level organism in Antarctica?

Krill.

Why is the microbial loop important?

It recycles dissolved organic matter back into the food web, enhancing nutrient cycling and productivity.

Where are the major fisheries generally located?

In coastal areas, usually upwelling zones and continental shelves with high nutrient levels/productivity.

How similar is productivity on land versus in the ocean?

They are about the same; land is more productive per square meter, while the ocean is larger, making them equal overall.

How is theoretical maximum harvest related to NPP and trophic level?

Maximum harvest is limited by net primary production (NPP) and decreases with each trophic level due to energy loss.

Why are fish mainly bottom feeders in the North Atlantic?

The sediments are nutrient-rich, leading to greater food availability.

What happened to the cod fishery in Canada versus swordfish in the North Atlantic?

The cod fishery collapsed due to overfishing, while swordfish were managed better due to stricter regulations.

How has the trophic level of the fisheries catch changed over time?

It has shifted down to lower food webs due to the depletion of top predators.

Approximately what percentage of seafood is farmed vs. wild catch? How has this changed over time?

60% wild caught; 40% farmed, with the percentage of farmed seafood increasing over time.

Name one issue with fishing regulations.

Bycatch quotas and enforcement issues, including poor monitoring and loopholes.

What is bycatch?

The unintended capture of a non-target species during fishing, typically turtles or dolphins.

What is a coral and how does it function?

Corals are marine invertebrates that build calcium carbonate skeletons and form reefs.

Why does a coral have algal symbionts? What does coral supply to the algal symbionts?

Coral provides algae with shelter and nutrients; in return, algae perform photosynthesis and supply energy to the coral.

What role do grazers (fish) play in the reef ecosystem?

They prevent algae from overgrowing coral and help maintain reef health.

Under what conditions are coral reefs found?

In warm, shallow, clear, low-nutrient waters, typically in tropical regions.

What is bleaching? How is it different than death?

Bleaching occurs when algal symbionts are stressed, causing coral to lose color; it is reversible, unlike death.

Explain another benthic ecosystem besides corals.

Hydrothermal vent communities rely on chemosynthesis, using bacteria to convert chemicals into energy.

How does a detrital food chain at the sea floor differ from the food chain in the sunlit layer?

Detrital food chains depend on organic matter sinking from above and are slower and less efficient, while sunlit layers rely on direct photosynthesis.