Final answer:
An estuary is a biome that occurs where freshwater and seawater meet. It is a protected area where many young organisms begin their lives. Salinity plays a crucial role in influencing the organisms and their adaptations in estuaries.
Step-by-step explanation:
An estuary is a biome that occurs where a source of fresh water, such as a river, meets the ocean. It is characterized by a strong surface flow of freshwater and a strong influx of seawater. Estuaries form protected areas where many young organisms begin their lives. Salinity, which varies based on the rate of flow of freshwater sources, is an important factor that influences the organisms and their adaptations in estuaries.