Final answer:
An estuary is a biome where a river meets the ocean, and a well-mixed estuary has a seaward flow of water with uniform salinity at all depths.
Step-by-step explanation:
Estuaries: Where the Ocean Meets Fresh Water
An estuary is a biome that occurs where a source of fresh water, such as a river, meets the ocean. In a well-mixed estuary, there is a seaward flow of water with uniform salinity at all depths. This means that the salt content of the water remains the same throughout the estuary, regardless of the depth. This uniform salinity is influenced by the rate of flow of freshwater sources and the tidal movements of the ocean.
For example, consider the San Francisco Bay, which is one of the great estuaries of the world. Fresh water from rivers flows into the bay, while high tides bring salt water from the ocean. The mixing of these waters creates a well-mixed estuary where the salinity is uniform at all depths.