Passage VI

The concentration of dissolved oxygen (DO) in river water affects the fish in the river. Many freshwater fish species, including crappie, perch, and bass, require a minimum average DO concentration of 5 parts per million (ppm) to thrive. Other fish, such as carp and gar, can tolerate average DO concentrations as low as 3 ppm. Table 1 shows the DO concentration at saturation for water at various temperatures. Figures 1 and 2 show the measured changes in a river's water temperature and DO concentration, respectively, over a 24-hour period in midsummer. Table 2 shows how the DO concentration affects fish species in a river.

Table 1 and Figures 1 and 2 adapted from American ChemicalSociety, ChemCom: Chemistry in the Community, 2nd ed. ©1993 by American Chemical Society.

31. River water is often used in industrial processes and is then returned to the river much warmer than when it was removed. Based only on the information inTable 1, why would this warmed water be a potential danger to fish populations? The warmed river water most likely has:

Answer and Explanation

Your Answer is

Correct Answer is B

Explanation

Look at table 1, the higher the water temperature, the less O2 dissolved in the water. Fish breathe in water by filtering the oxygen dissolved in water through their gills, so the less DO, the fish will be hypoxic