GEOLOGY

Detailed explanation-1: -The difference in river water and sea-water sedimentation, wind movement, and tidal activity allow the nutrients to be trapped and transported. The estuaries are covered from the influences of the ocean by reefs, deltas, and barrier islands. So, the correct answer is, ‘River and seawater’.

Detailed explanation-2: -Despite these challenges, estuaries are also very productive ecosystems. They receive nutrients from both bodies of water and can support a variety of life. Because of their access to food, water, and shipping routes, people often live near estuaries and can impact the health of the ecosystem.

Detailed explanation-3: -On average, estuaries are biologically more productive than either the adjacent river or the sea, because they have a special kind of water circulation that traps plant nutrients and stimulates primary production.

Detailed explanation-4: -Estuaries are very productive ecosystems because they constantly receive fresh nutrients from the river and from the ocean.

Detailed explanation-5: -An estuary is an area where a freshwater river or stream meets the ocean. In estuaries, the salty ocean mixes with a freshwater river, resulting in brackish water. Brackish water is somewhat salty, but not as salty as the ocean. An estuary may also be called a bay, lagoon, sound, or slough.