OtterEstuary

Area: 33.3 hectares, 82.3 acres.

A new site. In East Devon Area of Outstanding Natural Beauty. In County Structure Plan Coastal Preservation Area. Part a Devon Trust for Nature Conservation Nature Reserve (leased).

Description and Reasons for Notification:

The Otter Estuary contains a wide range of saltmarsh communities which together with additional areas of tall herb and scrub, support high numbers of breeding and over-wintering bird species. Otterton Point is an important location for vertebrate palaeontology.

Flowing due south, the lower 2km reach of the River Otter is bounded by sea embankment to the west and a cliff of sandstone rising to some 10m on its eastern side. Below White Bridge the divergence of the embankment from the direction of the river channel allows the estuary to broaden to a maximum width of 0.5km. Here, the deep, fine alluvium has enabled a well-developed pan and creek system to form. A shingle ridge running eastwards from the west shore virtually closes the estuary from the sea, the river entering the sea at Otterton Point through a 5m gap.

The saltmarsh flora is particularly well developed, with successions of glassworts Salicornia spp. and common cord-grass Spartina anglica at the lower levels; common saltmarsh-grass Puccinellia maritimasea-purslane Halimione portulacoides and sea arrowgrass Triglochin maritima occurring on the middle marsh with annual sea-blite Suaeda maritimasea aster Aster tripolium and thrift Armeria maritima becoming more abundant on the higher areas. Characteristic of the uppermost levels are sea rush Juncus maritimus, spear-leaved orache Attriplex hastata and red fescue Festuca rubra. Areas subject to only occasional flooding support stands of common reed Phragmites australis or sea club-rush Scirpus maritimus, both of which support high numbers of invertebrates. Additional habitat variety is found along the western side of the sea wall. Here the damp areas support a marsh vegetation which includes yellow iris  Iris pseudacoruscommon fleabane Pulicaria dysentericapurple-loosestrife Lythrum salicariacross-wort Cruciata laevipes and divided sedge Carex divisa, as well as a small reedbed with areas of open water. Rock sea-lavender Limonium binervosum is present on the cliff ledges towards the sea. 

On the river terrace upstream of White Bridge, a dense growth of willow Salix spp. scrub and tall herbs provides undisturbed cover for many breeding birds, particularly for summer visitors such as the reed and sedge warblers Acrocephalus scirpaceus and A. schoenobaenus. Also breeding on the site are serinSerinus serinusnuthatch Sitta europaeastonechat Saxicola torquata, all three species of woodpecker, little owl Athene noctuashelduck Tadorna tadorna and mute swan Cygnus olor. Overwintering species include firecrest Regulus ignicapillussiskin Carduelis spinus and waterbirds such as teal Anas creccawater rail Rallus aquaticus and dunlin Calidris alpina

There are several distinct communities of mud-dwelling invertebrates in the estuary. Characteristic species include the bivalve peppery furrow-shell Scrobicularia plana, the ragworm Nereis diversicolor and the crustacean Corophium volutator. This variety, together with adjacent habitats, provides food for a corresponding variety of bird species, some of which can be present in large numbers, principally curlew Numenius arquata and lapwing Vanellus vanellus. The area is an important additional feeding station for birds from the nearby Exe Estuary, especially during severe weather. 

Otterton Point itself has yielded the best remains of the diagnostic tooth plates, as well as a lower jaw, of a fossil known as the Devon rhynchosaur. As the only fossils, these allow approximate mid-Triassic dating of the Otter Sandstone Formation. This is also the most southerly occurrence of Rhynchosaurus, and it is of interest as a feature of ancient geography. The lower jaw was collected recently, and there is potential for more finds and future research.

 

Marine Protected Zone

The Otter Estuary is a nursery area for many types of fish, including bass. The muddy seabed here provides a home to all sorts of worms and burrowing animals. In turn these provide a food source for large numbers of birds including curlews and lapwings. Seahorses are also found here.

1989 Salt marsh survey of GB (Burd 1989) states that the Otter has more salt marsh vegetation than any other site in Devon, and with the associated tidal mudflats, it provides an important feed and resting area for overwintering birds.

Salt marshes are considered to be one of the most productive ecosystems in the world. The economic value of productivity of marshes has been estimated in 1997 at £9,900/ha/yr. Many birds, juvenile fish, crustaceans and molluscs use marshes as nurseries, including commercially important fish species such as sea bass. Salt marshes are important for climate change, and are known to accumulate sediment and organic matter at a rate that compensates for sea level rise, as well as providing carbon storage at approximately 10 times the rate observed in temperate forests. The IUCN states that salt marshes are “critical components to future carbon management discussions and strategies”.

Intertidal mud is a highly productive ecosystem and is an important feeding ground for wading and migratory birds that is available all year round. This habitat plays a crucial role in primary biomass production through the biofilm made up of microalgae at the air-mud interface. Intertidal mudflats are desirable areas for carbon storage due to the higher sedimentation rates than some other habitats such as freshwater wetlands.

Intertidal sand, muddy sand and mixed sediments have an important role in fundamental ecosystem processes, including nutrient cycling. Intertidal sediments are important spawning and nursery grounds and provide habitats for various fish species, which contributes to commercial and recreational fisheries benefits. Soft-bottom environments create complex microhabitats supporting abundant populations of microphytobenthos. Estuarine soft sediments support a diverse group of microscopic and macroscopic organisms.

Habitats and special interest protected:

Subtidal sand

High energy infralittoral rock

Coastal salt marshes and saline reedbeds

Intertidal coarse sediment

Intertidal mud

European eel Anguilla anguilla