Across
- 3. / water pollution caused by microorganisms
- 4. / made up of fine particles
- 7. / reduction in the concentration of dissolved oxygen
- 8. water found underground
- 10. / process of many nutrients in the water
- 11. / a member of a large group of unicellular microorganisms.
- 12. / too small to be seen by light microscopy.
Down
- 1. / an organism that lives in or an organism of another species.
- 2. / leakage of petroleum
- 5. / contamination of our environment with chemicals
- 6. / uppermost layer
- 9. / a chemical or natural substance added to soil or land to increase its fertility.