25April2019

Algae blooms discovered beneath Arctic ice

Phytoplankton can grow explosively over a few days or weeks. This satellite image shows a bloom that formed east of New Zealand between October 11 and October 25, 2009. (NASA images by Robert Simmon and Jesse Allen, based on MODIS data. Credit: NASA MODIS/Robert Simmon and Jesse Allen

A NASA mission to study the tiny algae vital to the ocean’s food chain has turned up a massive amount of phytoplankton where scientists least expected it – under the Arctic ice.

In a project that uses both satellites and on-site measurements to study this important food source for many of the ocean’s creatures, NASA sent a team to sample the ice pack off the Chukchi Sea along Alaska’s coast.

Researchers sampled deep beneath the 0.8-1.3 meter (yard) thick first-year sea ice on the Chukchi continental sea shelf and found “phytoplankton biomass was extremely high, about fourfold greater than in open water.”

Bloom extends 100km into ice shelf

The “massive under-ice bloom” also appeared to extend about 100 kilometres (62 miles) into the ice shelf, according to the study published in the journal Science.

Phytoplankton were scarcer and deeper in the open waters, according to the latest data from the mission, known formally as “Impacts of Climate on Ecosystems and Chemistry of the Arctic Pacific Environment,” or ICESCAPE.

“In contrast, phytoplankton biomass in open waters was markedly lower than that beneath the ice and was greatest at depths of 20 to 50 meters (66-164 feet) because of nutrient depletion near the surface,” said the study.

Blooms peaking 50 days earlier than usual

The study suggested that the Arctic Ocean is more productive than previously thought, but more research is needed to determine how these under-ice phytoplankton affect local ecosystems.

Phytoplankton blooms in the Arctic have been observed to peak as many as 50 days earlier than they did a dozen years ago, a development that could have implications for the larger food web, scientists have said.

The microscopic organisms are the base of the food chain and drive the food and reproductive cycles of fish, seabirds and polar bears. How larger animals may react to phytoplankton changes remains unknown.

Phytoplankton mass dropped by 40% since 1950

Phytoplankton are also important because through the process of photosynthesis they remove about half of the harmful carbon dioxide produced by the burning of fossil fuels worldwide.

Previous research has shown the microscopic organisms have been disappearing globally at a rate of 1% per year.

Since 1950, phytoplankton mass has dropped by about 40%, most likely due to the accelerating impact of global warming, said a 2010 study in the journal Nature.

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