When “The Blob” Made It Hotter Under the Water

Data from marine heatwave event may foreshadow climate change impact on marine microbial communities.

The Science

A team of researchers tracked the impact of a large-scale heatwave event in the ocean known as “The Blob.” The event was recorded during a long-term study of microbial communities in the northeastern subarctic Pacific Ocean.

The Impact

The microbial communities in the ocean drive the biological pump that takes carbon from the atmosphere and keeps it in the deep ocean. With genomic samples collected before, during and after The Blob, researchers developed a preliminary model of how marine microbial communities are affected by warming events. More time-series studies could help researchers improve predictive models on how climate change may impact marine microbes and by extension, the ocean’s capacity to act as a carbon sink.

Summary

As global temperatures rise, so do instances of extreme weather events such as hurricanes and droughts. Another one began in late 2013, when a large patch of warm ocean water about a third the size of the United States began forming in Alaska. Over the next two years it slowly spread, raising water temperatures by a few degrees. Eventually The Blob reached southern California.

Steven Hallam of the University of British Columbia was already collecting ocean water samples when The Blob started. The samples were taken up and down the water column along the Line P transect, a series of geographic coordinates which go from coastal to open ocean waters.

Between 2010 and 2016, Hallam and his colleagues collected more than 270 water samples. Genomic DNA extracted from the water samples were sequenced by the U.S. Department of Energy (DOE) Joint Genome Institute (JGI), a DOE Office of Science User Facility located at Lawrence Berkeley National Laboratory (Berkeley Lab), as part of Hallam’s approved proposal through the Community Science Program. The proposal focuses on uncovering the metabolic networks involved in carbon and nutrient flux in marine microbial communities.

Using the JGI-generated data, Sachia Traving, a former postdoctoral fellow in the Hallam lab now at the University of Southern Denmark, and colleagues at Hakai Institute, and Fisheries and Oceans Canada’s Institute of Ocean Sciences modeled the impact of The Blob on the microbial communities up and down the water column. They recently shared their findings in Communications Biology. They reported that the heatwave caused the microbial populations to cluster along the water column, like layers in a cake. Additionally, as nutrients became scarce during the heatwave, they saw populations shift. Smaller picoplankton and free-living microbes that can fix carbon dioxide replaced organic matter scavengers. This preliminary model aligns with several other studies on the potential effects of warming oceans on the microbial populations and the global carbon cycle.

Tracking large-scale marine events such as The Blob is difficult, but critical. By 2016, the microbial populations had begun to recover from the heatwave. Hallam said the work underscores the value of large-scale research collaborations and of conducting even more time-series studies.