The primary factor contributing to ocean stratification is density, which varies with temperature and salinity. Warmer, less dense water stays on top of cooler, denser water, leading to distinct layers in the ocean. This stratification can significantly affect the distribution of marine life, nutrient availability, and ocean circulation patterns. The interplay of water temperature and salinity influences the overall health of marine ecosystems and plays a crucial role in processes like photosynthesis and nutrient cycling.