Artificial Sweeteners and Daphnia Survival Tests

ISEF Category: Earth and Environmental Sciences

Subcategory: Environmental Effects on Ecosystems  ·  Difficulty: Intermediate  ·  Setup: School Lab  ·  Time: 1 to 2 Months

The Hook

Artificial sweeteners can pass through wastewater treatment and reach streams. That means a soda substitute can end up in a pond food web. Tiny water fleas like Daphnia react fast to water quality shifts, so they make a strong test species. You can turn that idea into a real environmental toxicology project.

What Is It?

This project asks whether artificial sweetener residues change how well Daphnia survive in small water systems called mesocosms. A mesocosm is a mini version of a natural habitat, like a controlled pond in a tank or jar. It lets you test a real environmental question without needing a full lake.

Think of the sweetener as a background chemical in the water, like salt in soup, except the effect may be subtle and long-term. Sucralose and acesulfame are both common in food products. Scientists worry because wastewater can carry them into rivers, and they do not break down quickly. Daphnia sit low in the food chain, so stress on them can ripple upward to fish and algae.

Why This Is a Good Topic

This is a good science fair topic because you can test a real pollutant class with clear outcomes. Survival, movement, and reproduction are measurable, and you can compare treated groups to controls. The topic connects to wastewater, freshwater health, and food web stability, so your results have real-world meaning. You can also learn experimental design, controls, and statistics without needing a university lab.

Research Questions

• How does sucralose concentration affect Daphnia survival in mesocosms? ?
• What is the effect of acesulfame concentration on Daphnia survival in mesocosms? ?
• Does a mixture of sucralose and acesulfame change Daphnia survival more than either compound alone? ?
• To what extent does exposure time change Daphnia mortality under the same sweetener concentration? ?
• Which sweetener, sucralose or acesulfame, causes a larger survival change at equal mass concentration? ?
• How does the presence of natural organic matter change Daphnia response to artificial sweeteners? ?

Basic Materials

• Daphnia culture from a biological supply company or classroom source.
• Clear containers or small aquaria for mesocosms.
• Dechlorinated water or aged tap water.
• Food-grade sucralose powder.
• Food-grade acesulfame powder.
• Digital kitchen scale with 0.01 g resolution.
• Disposable pipettes or transfer pipettes.
• Plastic beakers or cups for mixing.
• Magnifying glass or stereomicroscope.
• Thermometer.
• Notebook or spreadsheet for daily counts.
• Safety gloves and goggles.

Advanced Materials

• Daphnia magna or a locally approved Daphnia species.
• Temperature-controlled aquarium setup.
• Dissolved oxygen meter.
• pH meter.
• Conductivity meter.
• Stereomicroscope with camera attachment.
• Glass mesocosm tanks with lids.
• Analytical balance.
• Light meter.
• Water quality test kits for ammonia, nitrate, and phosphate.
• ImageJ for motion or body-size analysis.
• Statistical software for survival analysis.

Software & Tools

• Google Sheets: Organizes survival counts, concentrations, and summary tables.
• R: Runs survival curves, group comparisons, and concentration-response analysis.
• ImageJ: Measures body size, filtering rate proxies, or movement from images.
• PubMed: Helps you find review papers and toxicology studies on sucralose and acesulfame.
• NOAA Water Quality Portal: Helps you connect your topic to freshwater contaminant monitoring.

Experiment Steps

1. Define the exact response you will measure, such as survival, movement, or reproduction, and keep it consistent across all groups.
2. Choose one sweetener at a time first, then decide whether to add a mixture test after you have a clean baseline.
3. Plan a control group that matches everything except the sweetener exposure, including water source and container type.
4. Build a concentration series that gives you a low, medium, and high exposure range you can defend with prior research.
5. Design your mesocosms so you can track water quality, animal count, and treatment identity without mixing up samples.
6. Decide in advance how you will analyze the data, including survival curves, group averages, and any significance test you will use.

Common Pitfalls

• Using too few Daphnia per treatment, which makes normal random death look like a chemical effect.
• Letting temperature or light vary between mesocosms, which confounds stress from the sweeteners.
• Confusing the sweetener mass you added with the actual water concentration, which breaks dose comparisons.
• Skipping a vehicle control or water-only control, which makes it hard to tell whether handling caused the response.
• Counting only visible dead organisms and ignoring slower movement or reduced reproduction, which can hide early stress.

What Makes This Competitive

A stronger project will do more than report survival differences. You can compare two sweeteners, test a mixture, or add a water-quality variable that changes the response. A competitive entry also uses clean controls, enough replicates, and a survival analysis instead of only a final count. If you connect your lab results to real monitoring data from published studies or government sources, your project starts to look like environmental research, not just a classroom demo.

Project Variations

• Test how sucralose affects Daphnia in pond water versus dechlorinated tap water to look for matrix effects.
• Compare short-term survival with reproduction or clutch size to capture a subtler stress response.
• Add a second species, such as algae or copepods, to see whether the sweeteners change food-web interactions.

Learn More

• PubMed: Search for review articles on sucralose, acesulfame, and freshwater ecotoxicology.
• NOAA National Centers for Environmental Information: Use water quality background data and environmental context for freshwater systems.
• USGS Water Science School: Read clear explanations of how contaminants move through streams, lakes, and groundwater.
• EPA ECOTOX Knowledgebase: Look up toxicity data for aquatic organisms exposed to chemicals.
• NIH/National Library of Medicine Bookshelf: Search for free textbook chapters on aquatic toxicology and experimental design.