Sterols are key to coral larvae survival, swimming capacity, and thermal tolerance

Corals at very early life stages face high mortality bottlenecks, limiting natural stock-recruitment and the success of restoration and aquaculture strategies reliant on sexual reproduction. Nutrient availability and quality, particularly lipids, are critical for larval survival, dispersal, and settlement, yet the specific lipids influencing early-stage fitness remain unclear. Since measuring lipid depletion in non-surviving larvae is impractical, we developed a targeted supplementation approach to identify nutrients that enhance larval fitness. Supplementing Acropora spathulata larvae with nanoparticle-encapsulated triacylglycerols and sterols significantly improved swimming distance and speed, indicating enhanced dispersal potential. Supplementation with sterols, which are essential for cell structure and metamorphosis, also increased settlement rates. Furthermore, juveniles developed from larvae fed with sterols and omega-3-rich fish oils demonstrated superior performance under controlled and thermal stress conditions during the first six months, while those supplemented with Calanus oil also enhanced survival under elevated temperatures. Lipid profiling revealed key sphingolipids, glycerophospholipids, and fatty acids likely responsible for the improved fitness of fed larvae. Our approach highlights the critical role of lipid composition and availability during coral early life stages and demonstrates the potential of targeted nutritional supplementation to address nutrient deficiencies, enhance coral resilience, and support restoration and aquaculture efforts.