Eutrophication; Primary and Secondary Succession

Algal bloom absorbs sunlight

• TRUE

• FALSE

Which of the following is NOT a source of nitrates and phosphates into a river?

• Fertilizers

• Animal waste

• Wastewater

• Burning fossil fuels

In eutrophication, what directly causes the death of fish?

• The plants use up oxygen in respiration

• The fish are poisoned by high CO₂ levels

• Bacteria use up oxygen in respiration

• The fish use up oxygen in respiration

Eutrophication is defined as a change that occurs to an aquatic ecosystem. This change is mainly due to what?

• Newly introduced fish

• Depletion of the ozone layer

• Increased nutrient concentration

• Increase in atmospheric carbon dioxide.

The size of hypoxic/dead zones will ________ with more nitrogen run-off.

• Increase

• Stay the same

• Decrease

In a dead zone, _________ levels are really low such that living organisms are not able survive.

• nitrogen

• oxygen

• fertilizer

• carbon dioxide

Why do nitrates and phosphates cause algal blooms?

• They are critical plant nutrients.

• They kill off competition.

• Because algae grow faster than decomposers.

• Nitrates and phosphates are density independent limiting factors.

Based on the diagram, which fish species is in a breeding zone with higher oxygen levels?

• Fish Species 1

• Fish Species 2

Increases in algae may also cause

• Brown tides that suffocate shellfish

• release of toxins in the water

• Red Tides that may cause toxic shellfish poisoning

• All of these are possible effects

What is true of nitrogen fixation?

• It converts nitrogen gas to nitrates

• It is carried out by bacteria but can also happen by lightning

• It converts ammonia to nitrates

• It converts nitrogen gas to ammonia