M. gale is found in tidal wetlands in the Pacific Northwest, although it is more commonly described from bogs. Do you know what its salinity tolerance is (in ppt)?
Didn't know that was native in the PNW - it is also native here in Britain. Only in upland bogs though, never heard of it on tidal wetlands here.
Locals can see it at Tenant Lake Nature Center, near Ferndale, WA. Pojar/Mackinnon include "upper fringes of salt marshes" in list of habitats under 'Ecology'. Bet it can't take it too salty.