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Build an eco-friendly snow globe to mimic coral spawning

by Shelley Brown 16 Dec 2020 06:57 UTC
Mass coral spawning © GBRMPA

Once a year, an underwater blizzard with billions of colorful flakes occurs in coral reef ecosystems. This natural phenomenon is called coral spawning. Corals are essential to our oceans, but they can't move around the seafloor to find mates. Instead hard corals reproduce by releasing their eggs and sperm into the water.

Based on cues from the lunar cycle and water temperature, entire colonies of coral reefs simultaneously release their tiny eggs and sperm, called gametes, into the ocean once a year. The synchronization is crucial because the gametes of many coral species are only viable for a few hours. The underwater snowstorm makes it more likely fertilization will occur.

Once the gametes are released they rise to the surface where the process of fertilization takes place. When a coral egg and sperm join together as an embryo, they develop into a coral larva. The coral larva will float with the currents as they develop over the next several weeks until they become heavy enough to sink to the seafloor. If they settle in an area with proper conditions, they will mature into a coral polyp and grow into a new coral colony.

In this kid's activity, children can create eco-friendly snow globes to mimic coral spawning with materials found at home or a local drug store.


  • Glass jar with lid
  • Modeling clay
  • Bump chenille pipe cleaners
  • Paintbrush with narrow handle
  • Scissors
  • Epsom salt
  • Mineral oil
  • Hot glue gun

Build a coral reef snow globe:

  1. Use the modeling clay to create a small reef of boulder corals on the inside of the jar lid. Press down firmly around the edges to make it adhere firmly to the lid.

  2. Use the handle end of the paintbrush to poke shallow holes into the coral to represent individual coral cups found on the surface of a coral colony.

  3. To add Christmas tree worms to the coral, cut the chenille pipe cleaner apart between each of the fluffy segments. Fold the segment in half and stick into the coral.

  4. Fill jar with mineral oil, leaving room for displacement by the coral colony.

  5. Add one tablespoon of Epsom salt to the jar. These represent the sperm and egg bundles released by the corals during spawning.

  6. Screw the lid onto the jar. Check to make sure the jar is full and add more mineral oil if needed. Use hot glue around jar lid to prevent leaks.

  7. Shake the jar to mimic the mass spawning event.
Our Kids Environmental Lesson Plans (KELP) program features fifty hands-on activities that teach children the importance of protecting our oceans. These lessons require minimal preparation and simple materials that you can find at home or in a grocery store. Download all of the KELP marine science activities here.

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