DWT’s Peter Tinsley explores the underwater terrain of Dorset’s coast, from the seabed’s physical features to mapping its elusive ecology

The land area of Dorset is roughly equivalent to its adjoining sea area, which stretches 12 nautical miles from the coast – an area you could call Dorset’s territorial sea. But look at any map and you will see far fewer features (if any) marked in the sea than on land.
The mappable features on the seabed are all physical – depth contours, reefs, sandbanks, even tidal currents are reliably predictable. Some of these features are named on Admiralty charts – such as the Shambles Bank, Adamant Shoal, Whitehouse Grounds. Others have local names – Lobster Rock, Blackers Bump. There is also a scattering of shipwrecks – many dating back to the two world wars – and a few man-made features such as maintained channels into Poole and Portland harbours, and pipelines such as the disused radio-active waste pipeline running out from Arish Mell.

Who sees the seashore?
The ecological features are harder to map. While land is conveniently divided into tidy packages by walls, fences or uses, the seabed is mostly in the hands of one owner – the Crown – and there are no fences and very few seabed-uses that make an obvious mark.
Gathering ecological information in the marine environment, therefore, poses challenges. Dorset Wildlife Trust makes use of a mixture of digital technology and old-fashioned volunteering. The latter ranges from shoreline strollers reporting anything from jellyfish to stranded whales (this year’s signings have included several seahorses, one caught by a child ‘crabbing’ in Poole Harbour)to Seasearch divers trained in the identification of marine species and habitats and Shoresearch volunteers grabbing that short opportunity when the tide is out to search for intertidal species.
Other volunteers use snorkels and kayaks to map out shallow water features, such as beds of snakelocks anemones in Kimmeridge Bay.
Repeat surveys of the same site can detect long-term changes – in Kimmeridge Bay, volunteers have noticed an increase in the number of furrowed crab among the ledges, compared with juvenile edible crabs, a trend which appears to hold across the south west. Another Kimmeridge Bay group is monitoring the population of peacock’s tail alga – a species which is one of the features of the Purbeck Coast Marine Conservation Zone
The use of photogrammetry underwater in Dorset has provided detailed, scaled views of garden-sized patches of seabed – views that are impossible in the real world, where underwater visibility is just a few metres. We have now established three monitoring sites, one of which has been surveyed three times over three years. The same technique has been applied to monitor one of the scars left on the seabed in Poole Bay by cruise ships during the lockdown – still very visible three years later. Photogrammetry has proved to be an invaluable way of documenting habitat change, be that recovery or damage, natural or anthropogenic. It has enabled a much better appreciation and understanding of seabed biotopes and repeat surveys provide an opportunity to monitor change in a way that has not been possible before.

Jane Adams delves into the peculiar world of lichen, revealing a vibrant, year-round splash of colour in the UK’s landscapes, even on the darkest days

This week, nature reminded me that even its tiniest wonders still have the capacity to surprise and amaze. I had been leaning on an old gate, watching a mother roe deer and her two youngsters. Since June, her fawn’s coats have morphed from camouflaged caramel swirls to the soft beige that now matches her own. Turning to leave, something caught my eye. Sprouting from the rotten wood of the gatepost were tiny cups on stalks, like miniature golf tees. For a while, I lost myself in this Lilliputian ecosystem raised four-feet above the ground, a place so intricate and delicate, yet completely beyond my comprehension – like peering into an alien world. Back home, and having taken lots of photographs, I identified the stalks as apothecia, the reproductive hubs of lichens, ready to release their spores.

Lichens are weird
These strange organisms aren’t plants. Instead they’re a mashup of fungus and alga and/or cyanobacterium. And with more than 1,800 recorded species in the UK – 710 of which grow in Dorset – it’s surprising we don’t notice lichens more. Not only do they grow on pretty much any undisturbed natural substance including stone, wood and bark, but they’ll also happily wander across metal, glass and even plastics. The fungus bit makes up roughly 95 per cent of the lichen and provides the structure, and the alga and/or cyanobacterium provide the nourishment, through photosynthesis.
Since then, of course, I’ve been noticing lichens everywhere. White blotchy ones, like paint splatters on walls. Bright orange ones creeping over gravestones. Some like green and yellow coral growing on bark, while other species hang like verdant tinsel from twigs.
Our trees may have lost their autumn leaves, but lichens keep their glowing colours year round. So if you’re looking for something a little bit different, something that glows on the bleakest of winter days, keep an eye out for lichens – and lose yourself in their other-worldly magic.

Lichen information
The British Lichen Society britishlichensociety.org.uk
Some fantastic photographs of Dorset lichens (and other local wildlife) on Jenny Seawright’s website dorsetnature.co.uk
Mike Sutcliffe’s photos and help with identification of British Lichens:
britishlichens.co.uk