Crustose refers to a type of growth form commonly found in certain lichens and algae. These organisms grow tightly attached to surfaces, forming a crust-like layer that can be difficult to remove. Crustose lichens often appear flat and can be found on rocks, tree bark, and soil, contributing to the ecosystem by helping to break down substrates and create soil. In addition to lichens, crustose can also describe certain types of coral and other marine organisms that exhibit a similar flat, encrusting growth pattern. This growth form allows them to maximize surface area for nutrient absorption while providing protection from environmental factors.