Intertidal Zone

The intertidal zone, or littoral zone, is the shore strip between the highest and lowest tide marks, submerged at high water and exposed at low water. Its vertical extent equals the tidal range, from a meter on microtidal coasts to over 10 m in macrotidal embayments such as the Bay of Fundy. Organisms zone sharply across it by tolerance to desiccation and immersion, giving the classic upper, mid, and lower shore bands. The zone spans the foreshore on beaches and the tidal flat on low-gradient muddy coasts. Survey of it underpins chart datums, since the foreshore lies between MHWS and LAT.