The effects of global climate change are already causing sea ice loss, accelerated sea level rise and longer and more intense heat waves, among other threats.
Today, the first planktonic lipid survey in the global ocean predicts a temperature-related decrease in the production of omega-3 essential fatty acids, an important subset of lipid molecules.
An important implication of the survey is that as global warming progresses, there will be fewer and fewer omega-3 fatty acids produced by plankton at the base of the food web, which will mean fewer omega-3 fatty acids. available for fish and humans. . Omega-3 fatty acid is an essential fat that the human body cannot produce on its own and is widely considered a “good” fat that links seafood consumption to heart health.
The survey analyzed 930 lipid samples from across the global ocean using a uniform analytical workflow for accurate, high-resolution mass spectrometry, “revealing previously unknown features of oceanic planktonic lipidomas,” which is the totality of hundreds or thousands of lipid species in a sample. , according to a new article directed by authors from the Woods Hole Oceanographic Institution (WHOI).
“By focusing on ten molecularly diverse classes of glycerolipids, we identified 1,151 different lipid species, finding that unsaturated fatty acids (i.e., the number of carbon-carbon double bonds) are fundamentally limited by temperature. We expect significant decreases in eicosapentaenoic acid, an essential fatty acid [EPA] over the next century, which is likely to have serious harmful effects on economically critical fisheries, ”states the document,“ Global Ocean Lipidomes Show Universal Relationship Between Temperature and Lipid Unsaturation, ”published in Science.
EPA is one of the most nutritious omega-3 fatty acids, has been linked to numerous health benefits, and is widely available as a dietary supplement. “Ocean lipids affect your life,” says co-author of the review article Benjamin Van Mooy, a senior researcher in the OMSI’s Department of Marine Chemistry and Geochemistry. “We have found that the composition of lipids in the ocean will change as the ocean warms. This is a cause for concern. We need these lipids that are in the ocean because they influence the quality of the food that the ocean has. it produces for humanity. ”
“All organisms in the ocean have to deal with water temperature. With this study, we have revealed one of the important biochemical means used by cells,” says the lead author of the article in the Henry C. Holm magazine, PhD student at the Massachusetts Institute of Technology (MIT) – OMSI Joint Program in Oceanography / Applied Ocean Science and Engineering. “These EPA findings were made possible by a method that gives us a very complete picture of the glycerolipids in each sample. We saw that temperature was related to the saturation of cell membranes everywhere we look at the the ocean. ”
Lipids are a class of biomolecules produced and used by organisms in all walks of life for energy storage, membrane structure, and signaling. They account for about 10 to 20 percent of plankton on the ocean surface, where lipid production and reserves are highest. Oceanographers have used lipids as biomarkers of chemical and biological processes for decades, and extensive research into their biogeochemistry has been conducted. However, the combination of high-resolution mass spectrometry and downstream analytical tools has recently allowed for complete, unfocused assessments of oceanic lipids at scales similar to investigations of other molecules such as nucleic acids and proteins. .
In this new research, the researchers examined a global mass spectral data set of planktonic lipidomas from 146 sites collected during seven oceanographic research cruises from 2013 to 2018. The researchers note that although community lipidomas planktonics are affected by many environmental factors such as nutrient availability, the article reports “the relationship between lipids and arguably the most fundamental control of their composition: temperature.”
The researchers examined the saturation status of the top 10 classes of lipids with glycerol (i.e., glycerolipids) and found that among these classes, “temperature had a major influence on the structuring of the relative abundance of glycerol. ‘fatty acid species’. In addition, the researchers found a clear transition from lipid species with more unsaturated fatty acids at colder temperatures to fully saturated species at warmer temperatures.
“These trends are also evident in all other classes of glycerolipids, as well as in the aggregate total lipidomes of all classes of glycerolipids,” the paper states. “In fact, it’s amazing that the relationship between temperature and unsaturation arises from our data set despite such diverse and disparate planktonic communities, from nutrient-depleted subtropical gyps to the highly productive Antarctic coastal shelf.”
The researchers also found that the percentage of eicosapentaenoic acid (EPA) species abundance showed a strong relationship to temperature. To determine how the upper and lower limits of EPA composition may change under future warming conditions, the researchers generated maps using late-century sea surface temperature conditions for different climatic scenarios. Under the SSP5-85 climate scenario, which the document says is considered the worst case scenario with high greenhouse gas emissions, some ocean regions, especially at higher latitudes, see a drastic decline to -25% of EPA in relation to the amount. they have now, according to the newspaper.
Van Mooy said the research “is another example of how human activities are altering the oceans in a way we did not expect, and the uncertainty about how the ocean will react to warming.”
This work was supported by grants from the National Science Foundation, the Marine Microbiology Initiative division of the Gordon and Betty Moore Foundation, and the Simons Foundation.