On a recent expedition to the inhospitable North Atlantic Ocean, scientists at the University of Washington and collaborators studying the annual growth of tiny plants were stumped to discover that the plankton had started growing before the sun had a chance to offer the light they need for their growth spurt.
For decades, scientists have known that springtime brings the longer days and calmer seas that force phytoplankton near the surface, where they get the sunlight they need to flourish.
But in research results published this week in the journal Science, scientists report evidence of another trigger.
Eric D'Asaro and Craig Lee, oceanographers in the UW's Applied Physics Laboratory and School of Oceanography, are among the researchers who found that whirlpools, or eddies, that swirl across the North Atlantic sustain phytoplankton in the ocean's shallower waters, where the plankton can get plenty of sunlight to fuel their growth even before the longer days of spring start.
The eddies form when heavier, colder water from the north slips under the lighter, warmer water from the south. The researchers found that the eddies cause the bloom to happen around three weeks earlier than it would if it was spurred just by spring's longer days.
"That timing makes a significant difference if you think about the animals that eat the phytoplankton," said D'Asaro, the corresponding author on the paper.
Many small sea animals spend the winter dozing in the deep ocean, emerging in the spring and summer to feed on the phytoplankton.
"If they get the timing wrong, they'll starve," Lee said. Since fish eat the animals, a reduction in their number could harm the fish population.
Scientists believe that climate change may affect oceanic circulation patterns such as the one that causes the eddies. They've found some evidence that warm waters from the subtropics are penetrating further to the north,
|Contact: Nancy Gohring|
University of Washington