Nitrogen cycle through salmon to trees

Follow the nitrogen as it breaks down from salmon flesh to ammonia (ammonification). Plants can absorb ammonia from soil.
Science content
Biology: Life Cycles (2)
Biology: Food Webs, Ecosystems, Biomes (3, 4)
Chemistry: Atoms, Molecules (3-7)

Salmon bring nitrogen from the ocean into the temperate rainforest of the Pacific Northwest.
This activity shows how using molecule models.

Spawning salmon swim upstream, into the forests of the Pacific Northwest.
They either die on the river banks after spawning, or are caught by animals and taken into the forest to be eaten. Carcasses are left behind by bears, coyotes, cougars, racoons, eagles, crows etc.

See what happens to the salmon's carcass as it decomposes on the forest floor:
Inside the salmon is muscle which is made of protein. (That's why fish is a good source of protein for us.)
Zoom into the muscle to the molecules that make it up:…
(Molecules are tiny tiny particles that make up matter. Too small to see individually, but trillions of them together make up everything areound us.)
Lay out molecule model of protein in a salmon’s body.
The molecule is made up of atoms.
We will look at one atom, the nitrogen, and see how it moves through the food web.
Find the nitrogen atoms in this protein molecule - the blue atoms. (Blue is the international symbol for a nitrogen atom worldwide.)

The salmon protein first is broken down by bacteria in the soil, into its units.
Break the protein apart and give each student a piece. Ask students to combine their piece with water, as the soil bacteria do. (show image)
The nitrogen atoms are now part of single units of protein (amino acids).
The decomposition does not stop here.
The amino acid breaks apart to form ammonia (show image). Ask students to make a molecule of ammonia from their amino acid.
Ammonia is taken up by plant roots, and is a rich nutrient, allowing our Pacific Northwest trees to grow huge.
Plants get nitrogen from salmon! 3/4 of plant nitrogen in the temperate rainforest is from salmon!

Give students another oxygen so that they can make the other decomposition products, water and carbon dioxide (show image).
Make these molecules of decomposition these extra oxygens.

Then if time, free play molecule building.

Grades taught
Gr 2
Gr 3