Nigel Cattlin / Dog's mercury (Mercurialis perennis). Berkshire, England, UK. April.

Charlie Summers / Transit of Mercury in front of the sun as seen from Denver, Colorado at 07:09 on 9 May 2016 Mercury is the dot in the lower portion of the sun, all other dots are sun spots.

John Abbott / Caddisfly (Hydropsychidae) in flight and attracted to mercury vapour light, Lamar County, Texas, USA, August. August

Pete Oxford / Great barracuda (Sphyraena barracuda) laid out on beach. Research MAR Alliance is performing population assessments on Sharks, Rays, and Great Barracuda to aid with management and protection. They are...

Pete Oxford / MAR Alliance research team returning tagged Caribbean reef shark (Carcharhinus perezi) to water after collecting samles to determine methyl mercury levels. Lighthouse Reef Atoll, Belize. May 2015.

Pete Oxford / MAR Alliance researchers taking samples from Great barracuda (Sphyraena barracuda) with Nurse shark (Ginglymostoma cirratum) in the water below after samples have been taken. The samples are to deter...

Pete Oxford / Caribbean reef shark (Carcharhinus perezi) about to be released after sampling to determine methyl mercury levels by MAR Alliance, Lighthouse Reef Atoll, Belize.

Will Watson / Primroses (Primula vulgaris) growing in Ash (Fraxinus excelsior) woodland with Dog's Mercury (Mercurialis perennis) Broadfield Wood Nature Reserve, Essex Wildlife Trust, England. March.

Bert Willaert / Villager showing an intermediate product during gold extraction, Village in the Andes, Bolivia, November 2013.

Bert Willaert / Villager using his bare hands to mix the toxic mercury during gold extraction, Bolivia, November 2013.

Bert Willaert / Gold extracted from sand using mercury, Totora, Andes, Bolivia, November 2013.

Brent Stephenson / Pycroft's petrel (Pterodroma pycrofti) in flight against a blue sky, showing the underwing. Mercury Islands, Coromandel, New Zealand, February. Vulnerable species.