What is an estuary?

An estuary is defined as a habitat where fresh water from rivers and streams meets and mixes with salt water from the ocean. This unique environment is characterized by its brackish water, which is a mixture of fresh and salt water, and supports a diverse range of plant and animal life adapted to these conditions. Estuaries play a crucial role in ecological processes, serving as nurseries for fish and other marine species, and providing rich habitats for a variety of wildlife.

The other choices describe different aquatic environments but do not capture the specific nature of an estuary. A body of salt water refers exclusively to oceanic or sea environments without the mixing of fresh water. A land area that is regularly flooded can describe wetlands or floodplains, but does not specifically pertain to the mix of fresh and salt water. A deep ocean trench highlights a geological feature found in oceanic settings, which is unrelated to the mixing of water types. Therefore, the choice defining an estuary as a habitat where fresh and salt water meet is accurate and reflects its ecological significance.