Workspace▸ Science▸ Test 28
← Back to Science
Science · Drill 28

Science practice 28

15 questions ~9 min recommended
⏱ 00:00
Score
—

Trophic Classification

Oligotrophic
Mesotrophic
Eutrophic
Hypereutrophic

Phosphorus (μg/L)
0-12
12-24
24-96
96+

Bay Area 11 Phosphorus Levels Target: 10 μg/L
14-
12-
10
8
6
4
2
90 91 92 93 94 95 96 97 98 99
00 01 02 03 04 05 06 07
08
09
10 11
Year

level (μg/L)
70
60
50
40
30
10
South Lake2 Phosphorus Levels Target: 54 μg/L
90 91 92
93 94 95 96 97 98 99 00 01 02
Year
03
04
05
06
07
08
09 10 11

Bay Area 23 Phosphorus Levels Target: 14 μg/L
25
= 20 -
3
level
15 -
orus
10 -
5
90 91 92 93 94 95 96 97 98 99 00 01 02 03
Year
04 05 06 07 08 09 10 11

70
= 60 -
50
40
30
20
10
North Lake4 Phosphorus Levels Target: 25 μg/L
90 91
92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11
Year

5 6 7 8 9 10 11 12 13 14 15

Phosphorus is an essential nutrient that can negatively affect water quality, primarily by promoting excessive plant and algae growth. When this occurs, plants and animals that live in the water are affected by the reduced sunlight and lower oxygen levels that develop as organic matter decomposes. For humans, algal blooms lead to a reduction in the quality of drinking water, a decrease in the use of the water source for recreational activities, and a decline in property value along waterfront areas.

Lakes are often classified according to their trophic state, which indicates their biological productivity. The least productive lakes are called oligotrophic. Bodies of water classified as oligotrophic are typically cool and clear, have relatively low nutrient concentrations, and provide excellent drinking water. The most productive lakes are called eutrophic and are characterized by high nutrient concentrations that result in algal growth, cloudy water, and low dissolved oxygen levels. Table 8.6 shows the phosphorus levels that are found in lakes with different trophic classifications.

TABLE 8.6

Lake managers collected data over approximately two decades in four different ecological areas of a large lake. Each area had a different target phosphorus level based on the natural ecological factors of the area, as indicated in Figures 8.7 through 8.10. For proper lake health, the level must be at or below the target amount. Levels in excess of the target amount lead to an imbalance in nutrient flow.

Figure 8.7

Figure 8.8

Figure 8.9

Figure 8.10

1. In which area of the lake did the scientists fail to attain the target phosphorus level in any of the years of the study?

2. The target for Bay Area 2 falls in the trophic category of:

3. In 2011, flooding occurred in the region surrounding the lake. This caused:

4. In 2005, ecologists managing the lake began a concentrated effort to reduce agricultural runoff. This appears to have had the greatest effect on phosphorus levels in:

5. In 2002, the South Lake area had a trophic classification of:

6. For how many years of the study was Bay Area 2 found to be mesotrophic?

7. During which of the following years did Bay Area 1 have a trophic classification of mesotrophic?

8. Which of the following best describes the range in phosphorus levels in the North Lake over the 21-year period?

9. Which lake had the narrowest range of phosphorus levels over the time period of the study?

10. During how many years did Bay Area 1 meet or surpass the standard for proper lake health?

11. What was the difference in phosphorus concentration between Bay Area 1 and North Lake in 1993?

12. A neighboring lake was tested in 2005 and found to have a phosphorus level of 10 μg/L. It was most likely taken from a body of water similar to:

13. Which of the following statements is best supported by the information in the passage and figures?

14. The category of lake classification appearing most frequently in the North and South Lake areas was:

15. According to the information provided in the passage, which of the areas was the most likely to have the lowest dissolved oxygen levels in 2010?

← Prev test Next test →
Jump to