Science Buddies: "Ask an Expert"

My question I plan to investigate is "Does Sediment from parking lots contain compounds that are toxic to Daphnia." I need to purchase the Daphnia but don't know when I should? I will be observing the effects on the Daphnia over 48 hours. Should I make sure that the Daphnia are well established before I subject them to the sediment? What type of containers should I put the Daphnia in? Im purchasing the Daphnia kit but need to purchase smaller container to put daphnia and sediment in. Please help. Thank You

Hi Graceann,

You should let the daphnia start eating and growing before you run the experiment, so just follow the instructions that come with the kit. Daphnia don't like it too warm or too cold so try to keep the water temperature between 65 and 70F.

Here's a website that has lots of information about growing daphnia: http://www.aka.org/wako/DaphniaCultureMadeSimple.htm

I read the Procedure for the Scibuddies project [https://www.sciencebuddies.org/science- ... #procedure] and it does not say what kind of 'small container' to use for the experiment but I would think a 6 oz, clear plastic cup would work nicely. Also, the instructions don't say how much water to use for each test solution, just transfer 30-50 daphnia into each container. I would guess 4 oz would be sufficient but maybe if one of the other experts has done this project they could say how much to use.

I would also think that you should continue feeding the daphnia in the test containers as well as those in the aquarium. You could add more spring water or distilled water to the aquarium to replace what you took out for the experiment.

Let us know if you have more questions about the procedure. This is a really fun project! If you can do it try to look at your daphnia under the low power of a microscope or even with a 10X hand lens. They are really neat little critters!

Good luck!

Sybee

Thank you for your response. My mom is ordering the Daphnia today. Do the small containers need lids on them?

Hi Grace,

The Daphnia do need air so i would not put a tight lid on the cups. You could put something like a piece of paper towel that the air can go through just to keep dust out and secure it with a rubber band.

Good luck!

Sybee

Hi Grace,

I see you got some good help but I just wanted to check in and make sure everything worked out. How is the experiment going?

Cheers,
Colin

Thank you for your help. The Daphnia were just delivered. I have put water in the container. How long should I leave the water in before I put the Daphnia into the container. Also once the Daphnia are stable and I move some to the containers with sediment. Can I just use water pipette to transfer? One more question: Im testing the water toxicity from runoff in parking lot. Should I take couple samples from just one parking lot or samples from more than one parking lot. I don't want to make too complicated.

thanks

Hi Grace,

Your water fleas arrived! Good! Are they swimming around happily? You can go ahead and put spring water into the aquarium and put in the Daphnia. The water does not need to sit before you add them. Just don’t use chlorinated tap water as that is harmful to the little critters.

The Scibuddies project guide suggests that you make two cultures of your Daphnia just in case something happens to one of them, and I think that is a good idea. You can use a large glass jar or plastic container as a second aquarium.

Yes, the pipettes are for transferring the Daphnia. Transfer about half the Daphnia into the aquarium and half into another container. This way you will have a back-up culture. Just follow the instructions that came with the Daphnia for feeding them.

When you are ready to do the experiment you will use the pipette again, this time to transfer an exact number of live Daphnia into each container. Be sure you write down how many Daphnia you put into each container and label the containers. For the run-off sample I would use just one parking lot for now. Take at least 3 different sediment samples from different parts of the parking lot. Record each location and take a photograph so you know exactly where it was. If you have time, you could take samples from a second parking lot, maybe from around your school where the buses and service vehicles park.

This is a really neat project and I am very curious to know what happens to your Daphnia! Please keep us posted on your progress and of course, always ask about anything that you are not sure of.

Good luck!

Sybee