Colors of Great Salt Lake

Phenomenon:

The color of the water at Great Salt Lake changes with the seasons. The south arm of the lake is green in early spring. The north arm of the lake is pink in late summer and fall.

Student Task:

Construct an explanation for what causes seasonal changes in water color at the Great Salt Lake.

Explanation:

The water color at Great Salt Lake changes seasonally due to populations of microbes that thrive in high-salt conditions. Pink algae in the North Arm increase in the late summer and fall due to increased temperatures and evaporation of lake water. Green algae in the South Arm increase in springtime due to an influx of nitrogen as the mountain snow pack melts and waterways empty into the lake. The green water color changes back to blue by mid-summer due to brine shrimp that hatch and eat the algae, controlling the growth of the algae population.

Formative Assessment:

Use what students have written in their science notebooks as a formative assessment.

Do students understand...?