Which marsh zone is associated with higher salinity and occurs at the upper tidal edge?

• A. Low Salt Marsh
• B. Dunes
• C. High Salt Marsh
• D. Lagoons

Answer: (C)

Salinity tends to increase as you move from the actively flooded, lower marsh toward areas that flood less often and are more exposed to evaporation. The upper tidal edge concentrates salts because there’s less frequent tidal flushing and any seawater that intrudes can evaporate, leaving behind higher salt concentrations. That combination creates a high-salinity environment, which is what defines the high salt marsh. The low salt marsh is more often flushed and diluted by freshwater inputs, so its salinity is typically lower. Dunes and lagoons aren’t marsh zones within the tidal gradient, so they don’t match this pattern.