substrate substratethe surface or medium on which an organism lives or grows, or the material on the bottom of the ocean. Related Articles: Glossary: essential fish habitat (EFH)Underwater Sound and Coral Reef RestorationHow do marine invertebrates produce sounds?Pile drivingSea Urchin (Kina)How do marine invertebrates detect sounds?Wind TurbinePile DrivingHow does sound propagate through sediment? Chris Knowlton2019-09-10T09:41:25-05:00