An ocean is an aquatic ecosystem, not a terrestrial one, because its organisms live in saline water and its physical structure is governed by depth, currents, light penetration, salinity, and marine chemistry. Deserts, forests, and tundra are terrestrial biome types defined primarily by climate and land vegetation. Deserts are water-limited, forests support tree-dominated canopies where moisture and temperature permit, and tundra has low-growing vegetation under cold conditions, often with permafrost. Terrestrial ecosystems exchange gases with the atmosphere and organize much of their producti
Ref:
Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17