Habitats on the Dart – Saltmarshes & Tidal Reedbeds
The main Saltmarsh areas on the Dart are located between Sharpham and Baltic Wharf at Totnes. The most ‘typical’ saltmarshes can be found on the east bank of the river, between the hole in the wall and Sharpham. At mid-high tide these can be viewed from a small boat, or from the Dartmouth – Totnes riverboat, but don’t try to step ashore – you will damage these very fragile habitats.
Other smaller areas of Saltmarsh are found at the heads of Old Mill, Dittisham Mill and Hackney Creeks, and in Stoke Gabriel mill pool.
Our largest and most accessible tidal reedbeds are found in the ‘hole in the wall’ area on the west bank south of Totnes. These can be accessed by small boat – at high tide you can explore deep into the reedbeds, or there is a board walk ashore. Please be careful not to damage these important habitats. There is another area in Fleet Mill creek, but this is not accessible.
Description – Saltmarshes
Saltmarshes are a very special wildlife community, only found locally within our estuaries, that you have probably seen quite often but not noticed. Within our narrow & steep sided ria-type estuaries, they are a fringe community of specialist plants right at the top of the foreshore but before it becomes land proper. Saltmarshes support a quite special community of animals – some of them that migrate with the tides but their hidden claim to fame is their ability to lock away significant amounts of carbon for a very long time.
Saltmarsh plants, the critical part of a saltmarsh, are flowering plants that have evolved a variety of strategies to be tolerant to partial or even total tidal submergence by saltwater – salt is quite toxic to the majority of land plants. Contrary to popular belief, saltmarsh plants don’t need to be flooded by saltwater with each tide – that’s the realm of seaweeds just a bit further down the shore. They more need to at least get their ‘feet wet’ on the majority of tides to keep non-salt tolerant plants from out competing them.
Saltmarsh plants have evolved a number of strategies to being ‘salt tolerant’; an ability to actively excrete the salt, effective exclusion of salt by harbouring other salts, succulence to effectively dilute any salt uptake and a passive removal by transporting the salt to older leaves and discarding them. Many saltmarsh plants have a very fast reproductive cycle, so that the plant grows from seed, flowers and sets its own seeds before succumbing to the effects of the salt. Maybe for this reason, saltmarshes tend to die right back over the winter months … not helping our recognition of their special qualities or inner beauty!
During their more prolific growing season, the plant material and cover are in important food and shelter for many animals. Those that stay, need to in themselves be able to tolerate not just the saltwater but total immersion too. There are many worms, snails, crustaceans and even insects that the saltmarsh their primary habitat; on, within and under the saltmarsh plants. All this diversity and cover attracts fish at high tide (saltmarshes are important nursery grounds for some fish), and different birds at different states of tide.
The special position of saltmarshes at the extreme height of the foreshore have other positive functions too; they mop up nutrients from the water that flows over them from the land and tidal waters, they buffer the energy of waves that may erode the coast, and give us an aesthetic backdrop to the estuary view that might not notice unless it disappeared!
And the carbon storage? The saltmarsh plants sequester carbon from carbon dioxide through the age-old process of photosynthesis themselves, carbon that may then be trapped within the sediment beneath the saltmarsh when the plants (and animals) die … but this may only account for 20% of the carbon they store. The erect nature of the plants up into the water at high tide, slows the energy of that water and it drops its load of organic matter (detritus) that accumulates within the saltmarsh and builds up with time – trapping, removing and storing its carbon within the sediment for potentially 100s+ of years.
Tidal reedbeds are a particular type of saltmarsh, usually highly dominated by one species of reed that is also found in freshwater conditions. Tidal reedbeds typically develop along areas of foreshore where there is an upwelling of freshwater within the foreshore or a stream flows out over the foreshore and often with a freshwater reedbed community behind.
The Saltmarsh Project
Dart Harbour is currently taking part in a major project to study, survey and restore the saltmarshes along the Dart Estuary, as well as to educate the public about their importance. For more information visit https://bioregion.org.uk/project/thesaltmarshproject/
Other partners include the Bioregional Learning Centre, the Environment Agency, the South Devon National Landscape and Devon Wildlife trust.