News / Science & Technology

Scientists Report Steep Decline in Algae Critical to Marine Food Chain

Enlargement of phytoplankton cells
Enlargement of phytoplankton cells

The global population of a marine algae called phytoplankton has declined by 50 percent since the middle of the last century, threatening marine creatures that depend on the microscopic plant for food. Scientists blame global warming for the trend.

Tiny green phytoplankton are a food staple for many ocean creatures, according to marine biologist Daniel Boyce of Dalhousie University in Nova Scotia, Canada.  Boyce says phytoplankton are similar to trees and grass on land.

"They produce energy through the process of photosynthesis.  So in the presence of sunlight, they convert inorganic energy to organic energy.  And by doing this, they form the base of the entire marine ecosystem.  So they are the food for everything -- from little zooplankton up to the big whales," he said.

Boyce and his colleagues compiled and analyzed data going back to the 1800s.  Researchers found that the amount of phytoplankton had decreased about one percent of the global average per year with about a 40 percent decline since 1950.  The strongest trends were found in the Northern Hemisphere.  

Boyce says researchers analyzed the data derived from a low tech device called a secchi disc.

"It looks like a white dinner plate.  It's a disc with a rope attached to it.  And the person collecting data lowers this disc into the water, while [it is] attached to the rope.  And they measure the depth where the disc can no longer be seen.  And that's recorded as the water clarity or the secchi depth.  And it turns out that this depth, this water clarity, correlates quite well to the amount of phytoplankton in the upper oceans.  So it's a good measure of the amount of algae in the upper oceans," he said.

Combining the secchi disc data with information from more modern algae measurement tools, Boyce says researchers constructed a database of almost a half-a-million ocean measurements dating to the year 1899.

Biologists then plugged the measurements into a computer model that estimated global changes in the amount of phytoplankton over time.  Scientists say the greatest algae declines have occurred in the polar and tropical regions and the open oceans, where most phytoplankton production occurs.

Researchers say that rising ocean surface temperatures, due to global warming, are affecting the growth of phytoplankton, which need sunlight and nutrients from below the surface to grow.  They say that warmer water limits the amount of nutrients that are delivered to the surface from the cooler ocean depths.

Phytoplankton are critical to the health of our planet, according to Boyce, who says ocean algae produce half of the oxygen we breathe and reduce the amount of carbon dioxide that otherwise would contribute to global warming. "They affect the stability of our global climate.  And they can have the potential to affect our fisheries as well.  So phytoplankton are extremely important to us and we should be very concerned that phytoplankton has declined over this long time period," he said.

An article highlighting global reductions in marine algae is published in the journal Nature.

You May Like

Syrian Rebels Poised for Anti-Russia Collaboration

Forty-one insurgent groups issue joint statement vowing retaliation for Russian air offensives More

Political Maneuver Revives Export-Import Bank's Chances

Parliamentary tactic gets bill out of committee, but it faces opposition in the Senate More

Beijing Warns US on S. China Sea Patrols

Warning follows news reports Thursday that US military is planning to sail warships close to artificial islands Beijing has been aggressively building More

This forum has been closed.
There are no comments in this forum. Be first and add one

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
House Republicans in Chaos as Speaker Favorite Withdrawsi
Jim Malone
October 09, 2015 12:32 AM
The Republican widely expected to become the next speaker of the House of Representatives shocked his colleagues Thursday by announcing he was withdrawing his candidacy. The decision by Majority Leader Kevin McCarthy means the race to succeed retiring Speaker John Boehner is now wide open. VOA National Correspondent Jim Malone reports.

Video House Republicans in Chaos as Speaker Favorite Withdraws

The Republican widely expected to become the next speaker of the House of Representatives shocked his colleagues Thursday by announcing he was withdrawing his candidacy. The decision by Majority Leader Kevin McCarthy means the race to succeed retiring Speaker John Boehner is now wide open. VOA National Correspondent Jim Malone reports.

Video German, US Officials Investigate Volkswagen

German officials have taken steps to restore some of the reputation their car industry has lost after a recent Volkswagen diesel emissions scandal. Authorities have searched Volkswagen headquarters and other locations in an effort to identify the culprits in the creation of software that helps cheat on emission tests. Meanwhile, a group of lawmakers in Washington held a hearing to get to the bottom of the cheating strategy that was first discovered in the United States. Zlatica Hoke reports.

Video Why Are Gun Laws So Hard for Congress to Tackle?

Since taking office, President Barack Obama has spoken out or issued statements about 15 mass shootings. The most recent shooting, in which 10 people were killed at a community college, sparked outrage over the nation's gun laws. But changing those laws isn't as easy as many think. VOA's Carolyn Presutti reports.

Video Hungary Criticized for Handling of Refugees

Amnesty International has accused Hungary of breaking multiple international and European human rights laws in its handling of the refugee crisis. As Henry Ridgwell reports, thousands of migrants and refugees continue to travel through the Balkans to Hungary every day.

Video Iraqi-Kurdish Teachers Vow to Continue Protest

Sixteen people were injured when police used tear gas and rubber bullets to disperse teachers and other public employees who took to the streets in Iraq’s Kurdish north, demanding their salaries from the Kurdish Regional Government (KRG). VOA’s Dilshad Anwar, in Sulaimaniya, caught up with protesting teachers who say they have not been paid for three months. Parke Brewer narrates his report.

Video Syrian Village Community Faces Double Displacement in Lebanon

Driven by war from their village in southwestern Syria, a group of families found shelter in Lebanon, resettling en masse in a half-built university to form one of the biggest settlements of its kind in Lebanon. Three years later, however, they now face being kicked out and dispersed in a country where finding shelter as a refugee can be especially tough. John Owens has more for VOA from the city of Saida, also known as Sidon.

Video Bat Colony: Unusual Tourist Attraction in Texas

The action hero Batman might be everyone’s favorite but real bats hardly get that kind of adoration. Put more than a million of these creatures of the night together and it only evokes images of horror. Sarah Zaman visited the largest urban bat colony in North America to see just how well bat and human get along with each other.

Video Device Shows Promise of Stopping Motion Sickness

It’s a sickening feeling — the dizziness, nausea and vomiting that comes with motion sickness. But a device now being developed could stop motion sickness by suppressing certain signals in the brain. VOA’s Deborah Block reports.

Video Making a Mint

While apples, corn, and cranberries top the list of fall produce in the US, it’s also the time to harvest gum, candy, and toothpaste—or at least the oil that makes them minty fresh. Erika Celeste reports from South Bend, Indiana on the mint harvest.

Video Activists Decry Lagos Slum Demolition

Acting on a court order, authorities in Nigeria demolished a slum last month in the commercial capital, Lagos. But human rights activists say the order was illegal, and the community was razed to make way for a government housing project. Chris Stein has more from Lagos.

Video TPP Agreed, But Faces Stiff Opposition

President Barack Obama promoted the Trans-Pacific Partnership on Tuesday, one day after 12 Pacific Rim nations reached the free trade deal in Atlanta. The controversial pact that would involve about 40 percent of global trade still needs approval by lawmakers in respective countries. Zlatica Hoke reports Obama is facing strong opposition to the deal, including from members of his own party.

Video Ukranian Artist Portrays Putin in an Unusual Way

As Russian President Vladimir Putin was addressing the United Nations in New York last month, he was also being featured in an art exhibition in Washington. It’s not a flattering exhibit. It’s done by a Ukrainian artist in a unique medium. And its creator says it’s not only a work of art - it’s a political statement. VOA’s Tetiana Kharchenko has more.

VOA Blogs