Mesohaline

Part of speech: adjective

Definitions

1. Describing water or an aquatic environment with a salt concentration intermediate between freshwater and full seawater, typically containing between 5 and 30 parts per thousand
2. Pertaining to aquatic systems with moderate levels of dissolved salts, neither purely fresh nor fully marine, usually measuring 5 to 30 ppt salinity
3. Relating to brackish water conditions with a medium degree of salt content, falling between the extremes of freshwater ecosystems and oceanic environments

Etymology: "Mesohaline" describes water of moderate salinity, the brackish middle ground of an estuary where fresh river water meets the sea. It is built from two pieces: "meso-", from Greek "mesos" meaning "middle," and "haline," from Greek "hals," meaning "salt," which also gives English words like "halite" for rock salt. Put together, the term literally means "middle-salt," a label that places the water between the freshwater upstream and the fully saline ocean beyond. The word is a technical coinage rather than an ancient term. Scientists formed it in modern times from classical Greek roots, so no ancient writer ever described a mesohaline estuary. Its usefulness lies in giving oceanographers and ecologists a precise category for a salinity range that otherwise needed a clumsy description every time it came up.