WOODS HOLE, Mass. — Could warming ocean temperatures leave vitamin shelves empty in the future? A new study suggests that it may become harder and harder to find omega-3 fatty acids as climate change continues to change the oceans.
Researchers with the Woods Hole Oceanographic Institution conducted a survey of planktonic lipids in the oceans and predict that levels of these healthy fats will decrease as temperatures rise. This would lower the amount of essential omega-3 fatty acids available to both fish and people.
Normally, plankton produce omega-3 fatty acids, which sit at the base of the food web, where fish consume it — giving them an abundant supply in their bodies. Omega-3 is an essential fat that the human body can’t produce on its own, making oily fish one of the key sources of the nutrient. Previous studies show that this “good” fat can play a key role in lowering the risk of developing heart disease and possibly other diseases as well.
The team analyzed 930 lipid samples across the ocean using high-resolution accurate mass spectrometry. They revealed “heretofore unknown characteristics of ocean planktonic lipidomes,” covering the entirety of hundreds and possibly thousands of lipid species in their samples.
“Focusing on ten molecularly diverse glycerolipid classes we identified 1,151 distinct lipid species, finding that fatty acid unsaturation (i.e., number of carbon to carbon double bonds) is fundamentally constrained by temperature. We predict significant declines in the essential fatty acid eicosapentaenoic acid [EPA] over the next century, which are likely to have serious deleterious effects on economically critical fisheries,” the researchers write in the journal Science.
‘The lipids in the ocean affect your life’
EPA is one of the most nutritious omega-3 fatty acids. It’s also one of the most widely available and popular dietary supplements in the world. In the United States alone, Americans spent roughly $50 billion on vitamins and supplements last year.
“The lipids in the ocean affect your life,” says journal article co-author Benjamin Van Mooy, senior scientist in WHOI’s Marine Chemistry and Geochemistry Department, in a media release. “We found that the composition of lipids in the ocean is going to change as the ocean warms. That is a cause for concern. We need those lipids that are in the ocean because they influence the quality of the food that the ocean produces for humanity.”
“All organisms in the ocean have to contend with water temperatures. With this study, we have revealed one of the important biochemical ways cells are doing that,” adds journal article lead author Henry C. Holm, a doctoral student at the Massachusetts Institute of Technology. “These findings about EPA were made possible by using a method that gives us a very complete picture of the gylcerolipids in each sample. We saw that temperature was linked with the saturation of cell membranes everywhere we looked in the ocean.”
What makes lipids so special?
Lipids are in a category of biomolecules which all sorts of living organisms use for energy storage, membrane structure, and signaling. They also make up nearly one-fifth of all the plankton in the surface ocean, where lipid production is greatest.
Oceanographers have been using these fats as biomarkers for chemical and biological processes for years. However, the recent advances in high-resolution mass spectrometry and other analytical tools have allowed scientists to perform more comprehensive studies of ocean lipids.
The new study examined global-scale mass spectral datasets of planktonic lipidomes, collected from 146 different locations between 2013 and 2018. The results show that temperature has “the most fundamental control” over the composition of ocean plankton and, therefore, fatty acids.
“Temperature was highly influential in structuring the relative abundance of fatty acid species,” the study notes.
Study authors discovered a transition from lipid species with more unsaturated fatty acids in colder ocean temperatures to fully saturated species in warmer water.
“These trends are also evident in all the other glycerolipid classes as well as the total aggregated lipidomes of all glycerolipid classes,” the paper states. “Indeed, it is striking that the relationship between temperature and unsaturation emerges from our dataset despite spanning such diverse and disparate planktonic communities, from the nutrient-depleted subtropical gyres to the highly-productive Antarctic coastal shelf.”
The study estimates that by the end of the century, sea surface temperature conditions may be so warm that the number of species creating EPA could significantly die off. In their worst-case scenario, higher greenhouse gas emissions and warming waters could lead to a 25-percent drop-off in worldwide EPA coming from plankton.