Dunbeg study reveals mystery of the deep
AN EXPERIMENT conducted in a Scottish loch has revealed how a microscopic animal – the main food source for many larger marine species – schedules its day using its own genetic clock.
The ‘body clock’ of the copepod Calanus finmarchicus shapes its metabolic rhythms and movement through the water column.
This, in turn, has an enormous influence on the entire food web in the North Atlantic and Arctic oceans where Calanus finmarchicus is a central plankton species.
As part of the study, which has been published in the journal Current Biology, scientists from the Dunbeg-based Scottish Association for Marine Science (SAMS) carried out research on Loch Etive, where one of the only known isolated populations of Calanus finmarchicus is found.
In the world’s oceans, countless zooplankton species, such as copepods and krill, rise to the surface at dusk to gorge themselves on single- celled algae that can only thrive where there is sufficient sunlight.
The cover of night offers the zooplankton protection from predators such as fish, which need light to hunt. When dawn approaches however, they sink back into the dark depths where they can hide from their predators throughout the day – completing a cycle that likely represents the largest daily movement of biomass on the entire planet. Researchers are still working to decipher which signals these marine organisms use to decide when to rise and when to descend.
The SAMS team, alongside the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) and the University of Oldenburg in Germany, showed that Calanus finmarchicus possesses an internal genetic clock, also called the circadian clock, which produces a 24hour rhythm that functions without a day/night cycle. This could be important during the constantly dark polar winter and in the deep sea.
Co-author Dr Kim Last of SAMS added: ‘We have long looked to uncover the mysteries of zooplankton migrations and it appears that the circadian clock, much like our own, has a very important role to play in helping the animals be in the right place at the right time.
‘Such fundamental mechanistic understanding is crucially important if we want to predict how marine ecosystems will respond to the complexities of future climate change.’