Studland’s underwater meadows
The fact that Studland Bay in Dorset is a breeding site for both spiny and short-snouted seahorses is well documented, with 2009 having proved to be an exceptionally good year. But the bay is also important for a wide variety of animals, some rare or endangered, others of commercial value and some supremely adapted for this special habitat.
The seabed in Studland Bay is mostly sandy with the occasional rocky
outcrop poking through, offering a hard surface for species such as the
native oyster to attach. In places, the mobile sand is bound
together by the
dense roots of seagrass, a type of marine flowering plant and not a
Studland’s extensive seagrass meadow provides a rare and productive undersea habitat for a very diverse and specialised wildlife community. It offers shelter and an abundance of food for juvenile animals and as such is an important nursery area for a number of valuable commercial species such as black bream, cuttlefish, pollack, bass, plaice and sole to name but a few. The bay has also been identified as a likely nursery ground for the endangered undulate ray, one of very few such sites in the UK. However a host of other marine species breed there too. A few of the many examples are the delightful 15-spined stickleback, all six British species of pipefish (close relatives of seahorses), black gobies, dragonets and corkwing wrasse.
In addition to the charismatic species and those of commercial value
there are a host of bizarre inhabitants to be found, many evolved
specifically for this unusual environment. There are tiny,
pencil-thin crustaceans, Idotea linearis, disguised as pieces of dead
seagrass that roll around on the seabed, and masked crabs, Corystes
cassivelaunus, that burrow beneath the sand with a breathing tube
extended to the surface. The broad-nosed pipefish has evolved to
look just like a blade of seagrass and swims with a swaying motion as if
being moved by the swell and there are sea anemones, Sagartiogeton
undatus, that attach to shells beneath the sand as there is no other
hard attachment for them.
The species of seagrass found at Studland is the common eelgrass, Zostera marina. The underground rhizomes and roots of the plant help bind together and stabilise the seabed sediment, reducing rates of erosion and providing a natural coastal defence - potentially important in a site like Studland. The grass-like leaves are long and narrow and the flowers are partially hidden in a sheath. The waterproof pollen filaments produced by seagrass are thought to be the longest in the world. Seeds are dispersed by the sea although a meadow’s main method of spread is by its rhizomes. Nevertheless, the seed bank stored beneath a seagrass meadow could be vital in enabling the plants to recolonize following decline.
Until a wasting disease wiped out much of Europe’s seagrass in the 1930s it was a common habitat in estuaries and shallow waters in Britain and its economic value was recognised. It provided important shrimping areas and was regarded as an important fish nursery and habitat for eels, mullet and bass. Dried Zostera straw was used for stuffing mattresses and was a good sound-proofer, reportedly being used in the early BBC studios.
Globally, seagrass meadows are under threat. Growing, as it does, in shallow, sheltered bays and estuaries, seagrass meadows inevitably come into conflict with human activity. A recent study reported that 58% of the world's seagrass meadows are declining, with 110km2 of seagrass disappearing every year since 1980 - the main causes being direct loss from coastal development and dredging and indirect impacts of declining water quality. Other impacts include boating, fishing and natural impacts such as storms and disease.
Studland Bay is one of the most popular anchorages on England’s south coast, sheltered from the prevailing south westerly winds by the chalk cliffs of the Isle of Purbeck and in close proximity to Poole Harbour, a busy boating area. Concerns have been raised that the seagrass meadow is being fragmented by anchors and mooring chains that leave holes in the seagrass bed. On a busy summer day up to 300 boats may visit the bay and research has shown that recovery of the damaged areas is far from straight-forward. Currently there is no protection in place.
Dorset Wildlife Trust (DWT) has been collecting evidence and support to have Studland Bay designated as a Marine Conservation Zone (MCZ) for a number of years. It has published its vision for what a Studland Bay MCZ could look like, bringing a range of benefits for both people and wildlife. It also dispels the myths and misinformation that have been circulating, that the site would be closed to visitors if designated. During a survey carried out by DWT in 2013, 88% of boaters questioned expressed support for protection for Studland Bay.
Potential benefits arising from good management of the Bay include:
economic benefits to the local community from protecting the fish nursery ground;
improved safety on the water which would open the bay up to snorkelers, kayakers and swimmers, as well as benefitting visiting boaters;
provision of eco-friendly moorings and anchoring zones to enable visiting boats to enjoy the area without harming the underwater flora and fauna;
enhancement of the seagrass meadows’ role in coastal defence and as an important sink for CO2.
To view DWT’s vision for Studland Bay and see how you can help go to www.dorsetwildlifetrust.org.uk/studland
Marine Awareness Officer
Dorset Wildlife Trust