Willem Kolvoort / Water filled ditch with shadow of a tree on water with Fringed waterlily (Nymphoides peltata) Star duckweed (Lemna trisulca) Netherlands. July 2015. Commended in the Underwater World Category of the G...

Claudio Contreras / Canal between chinampas, a wetland agricultural system, with Fat Duckweed (Lemna gibba), Xochimilco wetlands, Mexico City, October

Claudio Contreras / Men paddling through canal with Fat Duckweed (Lemna gibba) between chinampas, a wetland agricultural system. Xochimilco wetlands, Mexico City, October

Will Watson / Circular mass of Duckweed (Lemna minor) formed as a consequence of vegetative/asexual reproduction located on a pond, Herefordshire, England.

Willem Kolvoort / Common Duckweed (Lemna minor) in brook in central Holland. August.

Will Watson / Red algae (Rhodophyta) and Least Duckweed (Lemna minuta) on Radnorshire pond, Powys, Wales, UK, May.

Paul Harcourt Davies / Common / Lesser duckweed (Lemna minor) on pond water, Italy

Wild Wonders of Europe / della Ferrera / Common duckweed (Lemna minor) covering a water channel at dusk, riparian forest mainly consisting of Willow trees (Salix sp) Lonjsko Polje Nature Park, Sisack-Moslavina county, Slavonia region, Posavi...

Oriol Alamany / Iberian Green / Western Marsh Frog (Rana perezi) in pond with Common / Lesser Duckweed (Lemna minor), Ebro Delta Natural Park, Catalonia, Spain, September, Captive

GEORGETTE DOUWMA / Whooper swan (Cygnus cygnus) parent with juvenile feeding on Common Duckweed (Lemna minor) UK

GEORGETTE DOUWMA / Coot (Fulica atra) on pond covered with Common duckweed (Lemna minor) UK

Willem Kolvoort / Underside view of Lesser duckweed (Lemna minor) in a nutrient rich ditch near Lake Naarden, Holland

Will Watson / Water fern {Azolla filiculoides} + Duckweed {Lemna minor} cover pond, UK

Andrew Parkinson / Lesser duckweed growing on canal water surface {Lemna minor

Ashley Cooper / Common frog (Rana temporaria) in a garden pond covered in Duckweed (Lemna minor), Ambleside, Lake District, Cumbria, UK. February.

Ashley Cooper / Common frog (Rana temporaria) in a garden pond surrounded by Duckweed (Lemna minor), Ambleside, Lake District, Cumbria, UK. February.

Doug Wechsler / Group of five Northern watersnakes (Nerodia sipedon) mating or attempting to mate on log in Duckweed (Lemnoideae) covered pond. Maumee Bay State Park, Ohio, USA. May.

Will Watson / Greater duckweed (Spirodela polyrhiza) fronds up to 1 cm, Least duckweed (Lemna minuta) fronds elliptic, Common duckweed (Lemna minor) fronds ovate, Ivy-leaved duckweed (Lemna trisulca) fronds narrow...

Jack Dykinga / Cypress dome swamp with water surface covered with Water-spangles (Salvinia minima) and Duckweed (Lemna), Big Cypress Seminole Indian Reservation, Florida, USA.

Jack Dykinga / Cypress dome swamp with water surface covered with Water-spangles (Salvinia minima) and Duckweed (Lemna), Big Cypress Seminole Indian Reservation, Florida, USA.

Andy Rouse / European otter (Lutra lutra) swimming in a pond covered with Common duckweed (Lemna minor), West Country Wildlife Centre, Okehampton, Devon, UK. August. Controlled conditions.

Andy Rouse / European otter (Lutra lutra) swimming in pond covered with Common duckweed (Lemna minor), West Country Wildlife Centre, Okehampton, Devon, UK. August. Controlled conditions.

Andy Rouse / European otter (Lutra lutra) jumping from jetty into a pond covered with Common duckweed (Lemna minor), West Country Wildlife Centre, Okehampton, Devon, UK. August. Controlled conditions.

Andy Rouse / European otter (Lutra lutra) jumping from jetty into a pond covered with Common duckweed (Lemna minor), West Country Wildlife Centre, Okehampton, Devon, UK. August. Controlled conditions.

Andy Rouse / European otter (Lutra lutra) jumping from jetty into a pond covered with Common duckweed (Lemna minor), West Country Wildlife Centre, Okehampton, Devon, UK. August. Controlled conditions.

Andy Rouse / RF - European otter (Lutra lutra) jumping from jetty into a pond covered with Common duckweed (Lemna minor), West Country Wildlife Centre, Okehampton, Devon, UK. August. Controlled conditions. (Thi...

Brian Bevan / Grass snake (Natrix natrix) at pond edge sensing with tongue, Bedfordshire, UK, September.

Brian Bevan / Grass snake (Natrix natrix) sensing with tongue while swimming through duckweed in pond, Bedfordshire, UK, September.

Brian Bevan / Grass snake (Natrix natrix) moving through grass at pond edge, Bedfordshire, UK, September.

Robin Chittenden / Water vole (Arvicola amphibius) looking out of hole in root curtain covered with Duckweed (Lemna sp). Norwich, Norfolk, England, UK. May.

Nigel Cattlin / Pond skater (Gerris lacustris) on water surface with duckweed and algae, Devon, England, UK, July

Nigel Cattlin / Pond skater (Gerris lacustris) on water surface with duckweed and algae, Devon, England, UK, July

Nigel Cattlin / Pond skater (Gerris lacustris) small early instar nymph on water surface with duckweed, Devon, England, UK, July

Linda Pitkin / Rootless duckweed (Wolffia arrhiza) in pond. A rare plant in Surrey, Least Duckweed (Lemna minuta) is also present. North of Haxted, Surrey England, August. Vulnerable in England.

Linda Pitkin / Rootless duckweed (Wolffia arrhiza), in a pond. Locally rare plant. Least Duckweed (Lemna minuta) is also present. North of Haxted, Surrey England, August. Vulnerable species in England.