Changing Ocean Temperature Forces Phytoplanktons to Bloom 4 Weeks Earlier Than Usual

A new study from the Woods Hole Oceanographic Institution (WHOI) revealed that the increasing ocean temperature is forcing key species of phytoplankton to have their annual bloom four weeks earlier than usual.

The study, published in the journal Science, showed that Synechococcus, a tiny bacterium common in marine ecosystems tends to bloom earlier due to the warmer oceans. Researchers noted that the warmer ocean temperature is accelerating the cell division of Synechococcus, resulting to a much earlier annual bloom.

"If the bloom expands, or moves earlier in the year, higher-level organisms that expect to feed on those consumers at a certain time of year might miss them entirely," said Kristen Hunter-Cevera, a graduate of the MIT-WHOI Joint Program in Oceanography and lead author of the study, in a statement.

For the study, the researchers used an automated sensor known as "FlowCytobot", which was developed by the researchers to continually sample seawater for 13 years. Using a mathematical model, the researchers were able to determine division rates of Synechococcus. Synechococcus cells contain compounds that glow orange and red under laser light, allowing the researchers to focus on that species among thousands of other phytoplankton in the water.

The researchers discover that the annual bloom of Synechococcus is occurring four weeks earlier than usual. However, the researchers were surprise to find out that the earlier bloom of Synechococcus did not alter the overall levels of the bacteria during the study period. The researchers observed that as the bacteria grew more quickly, they were also consumed more quickly by tiny protozoa, viruses, and other single-celled organisms that prey on them.

Their findings showed that consumers were able to keep up with changing spring bloom of Synechococcus. These resulted to a similar bloom cycle year after year, but with a shift in timing. The researchers, however, are concerned on how long can the consumers keep up with the changing bloom cycle.