Thermal Pollution p. 183

Human activity can result in warming of aquatic ecosystems - thermal pollution.

Most aquatic organisms cannot maintain a constant body temperature; their body temperature (and metabolic rate) varies with the environment, making them sensitive to temperature changes in the water.

The amount of dissolved oxygen (DO) decreases as temperature increases, making it difficult for fish to obtain enough oxygen to maintain metabolism.

Some organisms can tolerate high temperatures and/or low oxygen levels better than others.

Goldfish can tolerate temperatures up to 106°F (41°C), see Table 18-1.

Please note: goldfish is an invasive species; do not release goldfish into our streams and lakes.


Use breathing as a measure of metabolic rate in goldfish.

State your hypothesis on the effect of water temperature on breathing rate on data sheet (p. 187)

Observe goldfish breathing rate - keep fish calm, look at opercula (gill covers), not the mouth.

Establish a basal rate, then at 3 different water temperatures, 3 trials each p. 185.

DO NOT use temperatures near 40°C or 0°C: do not COOK or FREEZE the fish!

Note the preferred range for goldfish is 5 - 30°C - see Table 18-1.

instead of heating water in a separate beaker and pouring the hot water into the experimental beaker,
try heating the experimental beaker (with fish in it) on the hot plate, and heat the water SLOWLY.

If time permits: try another temperature, perhaps around 15°C.

Let the water temperature return back to room temperature before returning the fish to the tank.

Copyleft Peter Chen