Coastal saltmarshes consist of vegetation that occurs on muddy shores lying between mean high water neap & mean high spring tides. They are dominated by species that can tolerate flooding by seawater.
- Site: Low energy areas; shelter from wave energy, intertidal mudflats
- Main species: Halophytic, glasswort, saltmarsh grass, sea aster
- UK: 45,500 ha.
- NI: 250 ha
- Coastal saltmarshes are usually restricted to low energy environments where wave action is limited (JNCC, 2004).
- They consist of vegetation of intertidal mudflats lying between mean high water neap tides & mean high water spring tides, where there is a net accumulation of sediment.
- Saltmarshes generally form in estuaries (most common), saline lagoons, at the heads of sea loughs, on beach plains, extensive tidal flats, behind barrier island & on shingle pits.
- Where there is an influence of freshwater, saltmarshes may be transitioned to other habitats such as reed beds or fen.
- Vegetation of saltmarshes is highly specialised. Halophytic (salt-tolerant) plants first colonise sheltered tidal flats. Pioneer plants such as the glasswort Salicornia spp. colonise mud & sand flats if there is a high amount of sediment in the water. These plants trap & stabilize the sediment, leading to accumulation of sediment which raises the surface & vegetation, therefore becomes covered by fewer tides. This enables the colonisation of other species such as saltmarsh grass Puccinellia maritima & sea aster Aster tripolium. Through succession, stands of vegetation develop which are out of reach of all but the highest tides, supporting communities of plant & animal species.
- Some plant species, such as Blysmus rufus occur in Northern Ireland’s saltmarshes but are rare in Britain & Ireland.
- Eleven of the 25 NVC salt marsh categories have been found in NI (JNCC, 2004). The most commonly found are SM16b Festuca rubra – Juncus gerardii & SM13 Puccinellia maritime (Cooper et al., 1992). The rare SM19 Blysmus rufus community & SM20 Eleocharis uniglumis community have been found.
Current Status in UK & Northern Ireland
- Saltmarsh is a relatively rare habitat in the UK, with an estimated 45,500 ha.
- Ireland as a whole contains some extensive saltmarshes but larger systems occur in ROI (JNCC, 2004). Saltmarshes are small in extent in NI, making up only 250 ha (Boorman, in press; NIEA, 2005). This may be a result of smaller tidal ranges compared to the rest of the UK & Ireland, and therefore less area for saltmarsh development.
- In NI there are two main types of saltmarsh. Estuarine saltmarshes are found in five main sites (90% of the saltmarsh area) in the Roe Estuary in Lough Foyle, at Ballycarry in Larne Lough, in the Bann Estuary, around Strangford Lough & at Mill May in Carlingford Lough. Smaller beach-head type saltmarshes tend to occur as small pockets on rocky shores (NIEA, 2005). Small developing saltmarshes are widespread in the south & east of Rathlin Island coast.
- Saltmarshes are threatened by cutting for turf, agricultural improvement (e.g. re-seeding & draining), grazing, recreation (sporting activities, walking etc.), chemical pollution, litter, eutrophication, land reclamation, ‘saltmarsh squeeze’ & introduced species.
- Bann Estuary
- Ballycarry in Larne Lough
- Giant’s Causeway & Dunseverick
- Rathlin Island Coast
- Roe Estuary in Lough Foyle