Nick Upton / Hoverfly (Eristalis nemorum) nectaring on Wild marjoram (Origanum vulgare) flowers in a chalk grassland meadow, Wiltshire, England, UK, August.

Chris Mattison / Gutweed (Enteromorpha intestinalis) growing in shallow rock pool, Isle of Ulva, Mull, Scotland, June.

Philippe Clement / Gutweed / grass kelp (Enteromorpha intestinalis / Ulva intestinalis) washed ashore on Normandy coast, France, September

Adrian Davies / Enteromorpha (Enteromorpha intestinalis) seaweed in rock pool, Devon, England, UK, July.

Adrian Davies / Enteromorpha (Enteromorpha intestinalis) seaweed in rock pool, Devon, England, UK, July.

Nick Upton / Broad-clawed porcelain crab (Porcellana platycheles) hiding in a rockpool among Mussels (Mytilus edulis) and Gutweed (Ulva / Enteromorpha intestinalis), near Falmouth, Cornwall, UK, August.

Nick Upton / Gutweed (Ulva intestinalis / Enteromorpha intestinalis) growing in a rockpool high on the shore, with buoyant tubular fronds filled with air standing upright, Wembury, Devon, UK, August.

Nick Upton / Rockpool high on a rocky shore fringed with Gutweed (Ulva intestinalis / Enteromorpha intestinalis), Wembury, Devon, UK, August.

Nick Upton / Broad-clawed porcelain crab (Porcellana platycheles) hiding behind Gutweed (Ulva / Enteromorpha intestinalis) in a rockpool alongide a Flat / Purple top shell (Gibbula umbilicalis) and a Limpet (Patel...

Nick Upton / Gutweed (Ulva intestinalis / Enteromorpha intestinalis) growing in a rockpool high on the shore, with buoyant tubular fronds filled with air standing upright, Wembury, Devon, UK, August.

Nick Upton / Rockpool high on a rocky shore fringed with Gutweed (Ulva intestinalis / Enteromorpha intestinalis), with grassy cliffs rising behind it, Wembury, Devon, UK, August.

Nick Upton / Gutweed (Ulva intestinalis / Enteromorpha intestinalis) growing in a rockpool high on the shore, with buoyant tubular fronds filled with air standing upright, Wembury, Devon, UK, August.

Duncan Mcewan / Green alga in rock pool {Enteropmorpha intestinalis} Inverness-shire

Dan Burton / Gutweed in rock pool (Enteromorpha intestinalis). UK

Sue Daly / Gut weed (Ulva intestinalis) Sark, British Channel Islands

Alex Mustard / Black-lined periwinkle (Littorina compressa) on a bed of gutweed (Ulva intestinalis). St Brides Haven, Pembrokeshire, Wales, United Kingdom. British Isles. Irish Sea.

Philippe Clement / Gutweed / Sea lettuce (Ulva intestinalis / Enteromorpha intestinalis) green alga washed on rocky beach, Normandy, France, June

Philippe Clement / Gutweed (Ulva intestinalis / Enteromorpha intestinalis), sea lettuce (Ulva lactuca) and spiral wrack / flat wrack (Fucus spiralis) washed on beach, Normandy, France, June