Temperature and Dissolved Oxygen Use by Goldfish

PROBEWARE INVESTIGATION 13  A

Temperature and Dissolved Oxygen Use by Goldfish

Note: The teacher may wish to do this investigation as a demonstration.

Goldfish are cold-blooded animals. These animals, unlike their warm-blooded counterparts, maintain a body temperature slightly below their surroundings to prevent loss of moisture through evaporation. They also have the ability to decelerate or accelerate their metabolism proportionally to their body temperature. Hence, a slow metabolism would be present in colder temperatures, and a faster metabolism would be present in warmer temperatures.

In this investigation, you will attempt to measure the metabolism of goldfish exposed to different temperatures of water. You will then attempt to find a relationship between the two variables.

Problem

How can you determine the relationship between water temperature and goldfish metabolism?

Prediction

Sketch a graph incorporating the above variables that accurately portrays what you think will happen in the following experiment. Think carefully about the units you will use to identify your variables.

CAUTION

The utmost care must be taken with the fish being used in this experiment. They must be treated with tremendous respect. When testing for respiration rate, the proper container must be used. It is suggested that for the fish used in this particular experiment, a 400 mL beaker is sufficient in size.

The testing time must be kept to a minimum. This ensures that CO2 levels in the container are kept well below the safety limits and are not harmful to the fish.

Constant monitoring of the dissolved oxygen level in the container is also crucial in conducting this experiment. As soon as a recognizable slope is obtained, the experiment should be halted. This also ensures that the fish do not tire out from swimming against the mild current required for the dissolved oxygen probe to function properly.

The water temperature must be carefully monitored to ensure that the fish are kept within their optimum range.

Materials

computer system and interface
1 dissolved oxygen sensor
2 thermometers
magnetic mixer (with heater)
1 goldfish
aquarium and fish necessities (e.g., fish food and fish net)
1 Bunsen burner and lighter

wire gauze
1 electronic scale
masking tape
distilled water
tap water

1 bucket or deep tray
2 1 L beakers
1 retort stand
1 utility clamp
1 ring clamp

plastic wrap

PROBEWARE INVESTIGATION 13  A

Temperature and Dissolved Oxygen Use by Goldfish (continued)

Procedure

1. Copy the table below.

2. Set up the computer, interface, and dissolved oxygen probe. Set the data collection software to take 1 sample every 5 s and allow your experiment clock to run for 10 min.

3. Fill a 1 L beaker, Beaker A, with enough distilled water such that when the goldfish is placed in the water, the dorsal fin will be underneath the water. Do not put the goldfish in the beaker yet.

4. Place Beaker A on the electronic scale and push the tare function.

5. Put the goldfish into the beaker and record the mass of the goldfish in your table.

6. Plug in the magnetic mixer and place the retort stand with the rod as close as possible to the magnetic mixer. Attach the utility clamp to the retort stand such that it is over the top of the middle of the magnetic mixer. Do not worry about the height of the clamp from the surface of the magnetic mixer yet.

7. The first range that will be tested will be 20°C–25°C. Pour distilled water into another 1 L beaker, Beaker B, until it is brim full.

8. Using the fish net, put the goldfish into Beaker B and place the beaker on the magnetic mixer.

9. Drop the magnet from the magnetic mixer into Beaker B and take a sheet of plastic wrap and cut a small X-shaped slit in the middle.

10. Put the tip of the probe through the X-shaped slit so it is approximately 3 cm below the plastic wrap and tape the plastic wrap to the probe using the masking tape. Make sure the seal is airtight.

11. Dip the probe into Beaker B at an angle such that the water in the beaker is touching the bottom of the plastic wrap. Make sure there is not a bubble on the membrane. If there is, take the probe out of the water and lightly flick the end.

12. Fasten the probe in the clamp’s jaws such that the bottom of the plastic wrap is touching the water and tape the plastic wrap over the top of the beaker.

13. Turn on the magnetic mixer. The speed needs to be fast enough to move the water past the tip of the membrane, but not so fast as to tire the fish out too quickly.

14. Begin collecting data and stop the experiment when enough data have been collected to obtain a fairly accurate slope. Record the slope in your table.

15. Repeat the experiment in the other temperature ranges and record data in your table. Use the ice and Bunsen burner to help you attain the desired temperatures.

16. When all data have been collected, divide the slope attained by the mass of the fish to obtain the metabolic rate per gram of fish. This step is necessary if the experiment proceeds over several days or if several different fish are used in the study.

17. Generate a graph comparing goldfish metabolism (use of dissolved oxygen) with water temperature.

PROBEWARE INVESTIGATION 13  A

Temperature and Dissolved Oxygen Use by Goldfish (continued)

Observations

Mass of goldfish
(g) / Temperature (oC) / Slope
(mg/L/min) / Metabolic rate (mg/L/min/g)
10–15
15–20
20–25
25–30

Post-lab Questions

1. At what temperature is the goldfish using the least amount of dissolved oxygen? Why?

2. Predict the goldfish’s dissolved oxygen rate per gram in a temperature range of
35C–40C.

3. List 5 possible errors that would affect the data obtained in this experiment.

Conclude and Apply

4. Why does it take longer to gather results in the 10°C–15°C range?

Exploring Further

5. During the course of this experiment, having an airtight seal was an integral factor in achieving accurate results. Suggest an idea that could be employed using only items readily available around the home to ensure a better airtight seal.