Wildlife - Invertebrates
The pond bed is covered in a layer of silty mud, deep in places, and supports a large range of life within it.
Three species are of particular note:
- a Tube Worm (Ficopomatus enigmaticus) which leaves very distinctive casts
on rocks and other objects in the pond
- the Tentacled Lagoon Worm (Alkmaria romijni)
- the Starlet Sea Anemone (Nematostella vectensis)
The latter two are endangered species which are the reason for the pond being classified as a Site of Nature Conservation Importance.
The Tube Worm was the subject of a study from the 1980s until 2009. Dr C. Thorp of Portsmouth University studied and logged the progress of the tube worm over this time and has presented papers to international conferences on its life in the pond.
The worm was first noticed in northern France in 1921 and first recorded in London docks in 1922 This origin of this species is not clear. It occurs in waters of variable salinity in temperate or warm temperate areas of both northern and southern hemispheres, and it was possibly introduced from Australia. Its preferred habitat is brackish water as found in estuaries. It is probable that it arrived on being transported on ships hulls or on commercial mollusc shells.
Tube worm casts form a white coral-like encrustation to stones and other underwater objects. An easy place to see a spectacular coating is to lean over the footpath parapet carefully, on the sides of the main A259 bridge piers.
Rock encrusted with tube worm casts
View down on the feeding tentacles at the mouth of the tube worm cast
The Tentacled lagoon worm is a tiny bristleworm, less than five millimetres long. It lives in a tube made of mud in sheltered estuaries and lagoons. It has six gills and a number of smooth thread-like tentacles, which it pushes out from around its mouth to gather food from the surrounding mud. The tentacled lagoon-worm appears to require muddy sediments in brackish water, which is not fully salty.
Tentacled lagoon-worms are included in national conservation legislation because they are scarce and are vulnerable to changes to, or loss of, the habitats in which they live.
Threats to tentacled lagoon-worms include pollution of the mud and seawater; changes in the currents and the nature of the mud; changes in saltiness of the water and mud; and disturbance from dredging and bait-digging.
Tentacled Lagoon Worm
The Starlet Sea Anemone lives in brackish lagoons at or above high water, usually in mud, muddy sand and muddy shingle but it is also found on tasselweed and seagrass.
This is a tiny anemone. The column of its body (which is usually buried in the seabed) is rarely more than 15 mm in length, and the disc from which its tentacles emerge is a miniscule 1.5mm across. Its sticky tentacles are very long in proportion to its body, and are colourless and translucent with pale tips.
The main threat to this rare anemone is loss and damage to lagoons and other sheltered brackish water habitats, caused by pollution, drainage and other activities. Coastal defence works and associated infilling can have a major impact. Some populations of the starlet sea anemone have already become extinct in some places, due to loss of habitat and pollution.
In the UK, the starlet sea anemone occurs in only a few coastal lagoons in the Isle of Wight, Sussex, Hampshire, and in Dorset and along the East Anglian coast. It may also occur in some brackish ponds and ditches. It is not known elsewhere in Europe.
Starlet Sea Anemone
Insects are to be seen mainly on the banks in summer months and include butterflies, such as the Small and Large White, Peacock, Red Admiral, Meadow Brown, Speckled Wood and Gatekeeper. Dragon Flies and Damsel Flies can also be seen, with Common Darters (Sympetrum striolatum) and Banded Demoiselle (Pyrrhosoma nymphula) most common.