What best describes the change in salinity in a estuary at high tide (as water enters the area) ?

Increase in salinity

Explanation:

During high tide, the salinity of estuary increases.

An estuary is a transitional area between land and sea. It is richly furnished with both salty sea water and fresh river water from the land. The mixture of the two produces what is known as brackish water.

Freshwater lacks salt in its composition, and as it is brought from land, it mixes with the ever-restless sea water. During high tide when the level of seawater rises, more sea water is brought into the estuary. This makes the water very salty and thus increases the percentage of dissolved salt in the estuary.

Therefore, at high tide, the salinity of an estuary increases significantly.