The term salinity refers to the concentration of dissolved salts in water, particularly in ecosystems like oceans, lakes, and estuaries. Salinity affects the distribution and abundance of organisms, influencing species composition and ecological interactions. In marine ecosystems, for instance, varying salinity levels can determine the survival and reproduction of aquatic species. Salinity is crucial for organisms' osmoregulation, impacting their physiology and habitat selection. Additionally, changes in salinity due to human activities, such as pollution or climate change, can have far-reaching effects on ecosystem dynamics.