Diverse organisms living in marine ecosystems each contribute uniquely to the ecological stability and productivity of ocean ecosystems. Marine plants are foundational to many marine food webs, serving as primary producers. These plants also play critical roles in maintaining the physical structures of coastal habitats, reducing erosion, removing carbon from the atmosphere, improving water quality through filtration, and ensuring resilience against environmental changes and disturbances. Algae, although not classified scientifically as plants, are photosynthetic organisms that mirror many functions of marine plants. In addition to being a primary food source for other marine species, they produce a significant portion of Earth’s oxygen through photosynthesis — more than all the rainforests combined — and act as a major sink for carbon dioxide. They also contribute to nutrient cycling.