Alex Hyde / Bladder Wrack (Fucus vesiculosus) and Channelled Wrack (Pelvetia canaliculata) exposed at low tide in middle-shore zone. Isle of Mull, Scotland, UK. June.

Alex Hyde / Channelled Wrack (Pelvetia canaliculata), Bladder Wrack (Fucus vesiculosus) and Spiral Wrack (Fucus spiralis) seaweeds, exposed at low tide in upper-shore zone. Isle of Mull, Scotland, UK. June.

Adrian Davies / Channelled wrack (Pelvetia canaliculata), Devon, England, UK, July.

Nick Upton / Close up views of Spiral / Flat wrack (Fucus spiralis) surrounded by Channelled wrack (Pelvetia canaliculata) on rocks high on the shoreline, exposed at low tide, Rhossili, The Gower Peninsula, UK, Ju...

Laurie Campbell / Channelled Wrack Seaweed (Pelvetia canaliculata) exposed at low tide, South Uist, Outer Hebrides, Scotland, July

Adrian Davies / Channelled wrack (Pelvetia canaliculata) growing on rock, UK, August

Adrian Davies / Channelled wrack (Pelvetia canaliculata) showing detail of channel on underside of frond, UK, August

Adrian Davies / Channelled wrack (Fucus canaliculata) on rock face, at low tide, UK, August

Philippe Clement / Channelled / Channel wrack (Pelvetia canaliculata) and Limpets (Patella sp.) on rock exposed at low tide. Brittany, France, September.

Philippe Clement / Channelled / Channel wrack (Pelvetia canaliculata) on rock exposed at low tide. Brittany, France, September.

Robert Thompson / Channelled wrack {Pelvetia canaliculata} exposed at low tide, Ballyhenry Point, Strangford Lough, County Down, Northern Ireland, UK, September

Duncan Mcewan / Seaweeds exposed at low tide {Pelvetia canaliculata} and {Fucus spiralis} Scotland, UK