The wrack zone or wrack line is a coastal feature where organic material and other debris are deposited at high tide. This zone acts as a natural input of marine resources into a terrestrial system, providing food and habitat for a variety of coastal organisms.

Kelps are large brown algae or seaweeds that make up the order Laminariales. There are about 30 different genera. Despite its appearance, kelp is not a plant but a stramenopile, a group containing many protists.