Eutrophication

Eutrophication is caused by

• excess nutrients building up in the water.

• industrial point-source pollution.

• unlined landfills and septic tanks.

• wastewater from homes mixing with drinking water.

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As P and N build up, the probability of _______________ increases.

• lower BOD

• algal blooms

• oxygenation

• increased DO

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How does eutrophication cause the death of aquatic organisms

• the build up of carbon dioxide in the water

• the lack of nitrogen in the water

• the lack of carbon dioxide in the water

• the lack of oxygen in the water

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NGSS.MS-LS2-4

How can an algal bloom (eutrophication) lead to a decrease in dissolved oxygen? Select all that apply.

• Algae is a heterotroph and consumes more oxygen than it produces.

• Decreased light penetration limits photosynthesis below the surface.

• Bacteria consume oxygen as they decompose dead algae and other organisms.

• Decomposes that would have produced oxygen are outcompeted by algae.

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NGSS.MS-LS2-4

The two critical nutrients in eutrophication are... (select two)

• nitrates

• phosphates

• carbon dioxide

• dissolved oxygen

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In eutrophication, dissolved oxygen levels decrease because

• bacteria use it as they decompose organic material

• algae uses it during photosynthesis

• it reacts with hydrogen to form H2O (water)

• fish use it up as they consume algae

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NGSS.MS-LS2-3

A new golf course is built next to a river. Over the past several months, the nitrate levels of the water in the river have been increasing. Which best explains the cause of the increasing nitrate levels?

• increased growth of algae

• decreased biodiversity

• runoff from fertilizer

• chemical reactions with pesticides and fertilizers

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Which would most likely happen if too many nutrients entered an estuary?

• Nutrients would be used up by the fish and plants, keeping the estuary in balance.

• Algal blooms would lower dissolved oxygen levels, causing fish to suffocate.

• Algal blooms would decrease, leaving few food resources for fish.

• Nutrients would sink to the bottom, increasing soil deposition.

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Why should farmers be concerned about unused nitrates contaminating surface water and groundwater supplies?

• Unused nitrates reduce algae growth.

• Unused nitrates increase oxygen in the water.

• Excessive amounts of nutrients cause overpopulation of fish.

• Excessive amounts of nutrients speed up the eutrophication process.

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NGSS.MS-ESS3-4

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Which process would most likely increase the dissolved oxygen level in a freshwater lake?

• algae bloom

• lake turnover

• photosynthesis

• respiration

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