Jeff Vanuga / Ephydrid flies (Ephydra sp) that eat microscopic algae and survives during the winter in thermal pools. Biscut Basin, Yellowstone National Park, Wyoming, USA, January.

Roberto Rinaldi / Yellow fan coral / Seafan (Paramuricea clavata) amongst mass of invasive algae (Caulerpa taxifolia) with Rainbow wrasse fish (Coris julis), Strait of Messina, Southern Italy

SCOTLAND: The Big Picture / Mysid on algae (Fucus serratus), Shetland Isles, Scotland, UK, June.

Georgette Douwma / Funnelweed (Padina gymnospora) and Green Algae (Halimeda sp.). West Papua, Indonesia. Indo-West Pacific.

John Cancalosi / Red-eared slider (Trachemys scripta elegans) in blue-green algae (Woronichinia naegeliana). Microcystin produced is toxic to wildlife and humans. Maryland. October 2018.

Ashley Cooper / Pool coloured red from algae that have been fertilized by seabird guano on the Farne Islands, Northumberland, England, UK. July.

Alex Mustard / Weedy seadragon (Phyllopteryx taeniolatus) male carries eggs through a kelp forest (Macrocystis pyrifera) in Tasmania, Australia. Tasmania is the only part of Australia with giant kelp forests. The ke...

Alex Mustard / View upwards through a giant kelp forest (Macrocystis pyrifera). Santa Barbara Island, the Channel Islands, California, United States of America. East Pacific Ocean

Alex Mustard / Detail of the gas bladders and fronds of Giant kelp (Macrocystis pyrifera) plant. Santa Barbara Island, the Channel Islands, California, United States of America. East Pacific Ocean

Alex Mustard / Detail of the gas bladders and fronds of Giant kelp (Macrocystis pyrifera) plant. Santa Barbara Island, the Channel Islands, California, United States of America. East Pacific Ocean

Nick Hawkins / Yellow-spotted salamander eggs (Ambystoma maculatum) showing symbiosis with green algae, New Brunswick, Canada, May 2015.