Our directory of things of interest

University Directory

Moonlight migration for Arctic zooplankton

Zooplankton, such as jellyfish, fish eggs or these crustaceans, are small marine animals that spend all or most of their lives as plankton Zooplankton, such as jellyfish, fish eggs or these crustaceans, are small marine animals that spend all or most of their lives as plankton (NOAA)
15 Jan
2016
Solving the paradox of Arctic darkness, a new study finds that zooplankton migration is being guided by the light of the moon

Zooplankton migrate to deeper waters when the sun comes up. But what happens if the sun sinks below the horizon for weeks at a time?

This is the question scientists at the Scottish Association for Marine Science (SAMS) are hoping they have solved. In a new study, they argue that in the absence of sunlight, zooplankton move up and down the water column using the light of the moon. The study shows that even under a layer of ice, during the darkest days of the polar winter, there is a significant zooplankton response to what might be considered very subtle changes in illumination.

‘The findings were incredibly exciting,’ says Laura Hobbs, Arctic researcher at SAMS and co-author of the study. ‘The fact that some of the zooplankton population remains active throughout the Polar Night (instead of entering a hibernation phase) has been suggested for some years. However, up until now, we had little understanding of what they were responding to.’ The data was collected from instruments deployed all across the Arctic and according to the findings, the lunar response is ubiquitous across the region – in fjords, ice shelves and the open sea.

moon
The Arctic moon (Image: Incredible Arctic)

The vertical migration of zooplankton takes place in all water bodies. It is seen as the world’s greatest migration according to biomass. Thought to be avoiding being seen and eaten, the zooplankton migrate on a 24-hour cycle – to the deep in the day and the shallows at night. According to the study, the so-called ‘werewolf’ behaviour of Arctic zooplankton means adjusting their daily migrations to the 24.8-hour lunar day, when the moon has a greater impact than the partial sun, with a time of transition in spring and autumn. When the full moon is bright, they sink to depths of around 50 metres.

Understanding the Arctic-wide movement of zooplankton could reveal much about the Polar ecosystem at large. ‘The existence of a vertical migration (whether it be on a 24 or 24.8-hour cycle) throughout winter suggests that active predation is a continued threat,’ says Hobbs. She believes it could also be creating natural patterns: ‘a dense layer of zooplankton at 50 metres, during the full moon, could actually lead to higher rates of predation, through more chance encounters between predator and prey.’

Related items

NEVER MISS A STORY - Follow Geographical on Social

Want to stay up to date with breaking Geographical stories? Join the thousands following us on Twitter, Facebook and Instagram and stay informed about the world.

More articles in NATURE...

Wildlife

James Wallace, Chief Executive of Beaver Trust, shares an unlikely…

Wildlife

The winners of the most hotly anticipated photography competition have…

Polar

Artist and geographer Nick Jones was appointed artist in residence…

Oceans

Photojournalist Tommy Trenchard joins a research expedition to the Saya…

Climate

So far, carbon offsets have focused mostly on tree-planting. But…

Oceans

Marine scientists are often too few and too underfunded to…

Wildlife

Indigenous marmosets are under threat from released pets and forest fragmentation

Wildlife

A rare encounter with a leopard in the mountains of…

Oceans

The Saildrone Surveyor, a type of uncrewed autonomous vehicle, has…

Climate

Australia has the highest per-capita use of rooftop solar power…

Wildlife

Ecoacoustics – a way to listen in closely to the…

Wildlife

Ash dieback is set to transform the British landscape. Robert…

Geophoto

Photographer Patrick Wack documents documents changes in the Chinese province 

Climate

A growing tide of legal action is increasing pressure on…

Wildlife

Classifying a group of organisms as a separate species has…

Geophoto

Artist Sarah Gillespie used the historic mezzotint technique for her…

Geophoto

The winners of the 2021 competition of Earth Photo have…

Climate

As climate change dysregulates weather patterns, cases of pest explosions…

Polar

Arctic nations are gearing up to exploit the region’s abundant natural…