|Salt marshes develop between the mean high and low water marks in areas of soft sediments (mud or fine sand) that are relatively sheltered from wave action. Saltmarsh vegetation has to be salt-tolerant (halophytic) in order to survive being covered by the tides. Tolerance to salt water creates zonation of different plant communities in the salt marsh. Those plants nearer low water need to be more tolerant of salt water, as they spend longer being covered by the tide.
Atlantic salt meadows form the middle and upper reaches of salt marshes, where the vegetation is still covered by the tide but less often and for shorter times. Much of the Milford Haven waterway is characterised by extensive salt marsh and Atlantic salt meadows. These meadows flank both sides of the waterway and extend into the large shallow bays of Dale, Angle Bay, Sandy Haven, Pembroke River and further upstream in the Carew and Cresswell Rivers and Western and Eastern Cleddau.
|Species of particular nature conservation importance, including nationally rare and scarce salt- meadow / salt-marsh transition species have been recorded within the SAC. Populations of notable salt-marsh species include: Limonium humile, L. procerum, Salicornia pusilla, Althaea officinalis, Apium graveolens, Carex punctata, Hordeum secalinum, and Lathyrus palustris. A particularly good area for Atlantic salt-meadow is within the Pembroke River.