Question

Use the passage to answer the question.

Identify the most effective strategy for minimizing phytoplankton and eutrophication in this ecosystem based on the limiting nutrient(s).

Oreduce the amount of nitrogen-based fertilizers

replace nitrogen-based fertilizers with phosphorus- based fertilizers

(1 point)

use equal amounts of nitrogen and phosphorus-based fertilizers

This figure presents the results of an ecological study on the effects of runoff from various fertilizers into coastal marine environments. Phytoplankton density was measured at different collection sites enriched with nitrogen-based fertilizers

(ammonium), phosphorus-based fertilizers (phosphate ), and no fertilizers as the control group. The purpose of the study was to determine the limiting nutrient for phytoplankton to minimize eutrophication in coastal marine ecosystems.

Increase the amount of phosphorus-based fertilizers

G

Ammonium

enriched

Phosphate

enriched Unenriched control

A

18-

CD

E

Collection site

F

Data from J. H. Ryther and W. M. Dunston, Nitrogen, phosphorus, and eutrophication In the coastal marine environment, Science 171:1008-1013 (1971).

Limiting Nutrients

Results

30-

24-

Phytoplankton density (millions of cells per mL)

0

B

12-

6

Answer 1

The most effective strategy for minimizing phytoplankton and eutrophication in this ecosystem, based on the limiting nutrient(s) indicated in the passage, would be to reduce the amount of nitrogen-based fertilizers. This is because the study found that phytoplankton density was higher in sites enriched with nitrogen-based fertilizers compared to those enriched with phosphorus-based fertilizers. Therefore, reducing nitrogen-based fertilizers would help decrease the excess nutrients leading to eutrophication in the ecosystem.