Plankton sparkle even in the Arctic’s winter dark
It has been called the longest night – the period when the sun can disappear from view for months at a time in polar regions. For centuries, people assumed these long polar nights created a dead zone of sorts, with any life frozen in a kind of suspended animation. For the first time, however, researchers have shown that dark Arctic seas can sparkle with light-producing plankton – raising new questions about how Arctic ecosystems function, and maybe even providing a clue as to how some seabirds hunt in the cold winter blackness.
In January 2010, researchers from Norwegian and U.S. universities launched a robotic submarine into the chilly waters off the high Arctic island of Svalbard, “where the long periods of continuous darkness… create an environment, at least with respect to light, that is similar to the deep-sea,” they note in the Journal of Marine Biology. On board were instruments able to measure the flickers of light produced by bioluminescent plankton, which researchers have speculated use light to do everything from attracting prey to warding off predators.
The sub detected flashes “throughout the water column both night and day,” they report, “with higher bioluminescence at depth during the day and increased surface bioluminscence at night.” That suggests the largest plankton with the brightest flashes were migrating upward during the night. Exactly what triggers the daily vertical migration was unclear, however. Although differences between day and night light levels have been shown to trigger vertical migrations in many kinds of plankton, in this case human eyes could detect no difference in light levels between night and day.
Another mystery is how five kinds seabirds seen by the researchers were finding food. “These seabirds have, to the best of our knowledge, not been reported to overwinter at these latitudes,” the researchers write. “Whether bioluminescence and/or [the vertical plankton migrations] are playing roles in the foraging behavior of these visual predators is an exciting possibility, although still an open question.”
The “results open new lines of enquiry regarding the function and process during a time of year when classical paradigms of Arctic ecosystems postulate that organisms are predominately in a state of hibernation,” the researchers conclude. And the discovery of the natural night lights raises questions about how human activities, such as oil drilling, might affect “the high Arctic, which up until to now has been considered ‘without life’ during the polar night.” – David Malakoff | January 10, 2012
Source: Berge, J., Båtnes, A., Johnsen, G., Blackwell, S., & Moline, M. (2011) Bioluminescence in the high Arctic during the polar night. Marine Biology, 159(1), 231-237. DOI: 10.1007/s00227-011-1798-0
Image Wikipedia Commos/Maria Antónia Sampayo, Instituto de Oceanografia, Faculdade Ciências da Universidade de Lisboa