Dwarf eelgrass ( Zostera noltii ) fatty acid remodelling induced by climate change

Dwarf eelgrass Zostera noltii meadows are found in estuarine coastal areas across the north-eastern Atlantic, where they provide key ecosystem services, including nursery grounds, sediment stabilization, nutrient cycling and carbon sequestration. These blue carbon ecosystems are being subjected to several anthropogenic pressures, including climate change-related effects. In the present study, we investigated the biochemical changes (fatty acid profiling) under different climate change scenarios (present-day conditions, ocean acidification, ocean warming and combined warming and acidification), following IPCC RCP scenario 8.5. Significant modifications in the percentage of saturated (SFA) and polyunsaturated fatty acids (PUFAs) in response to warming and low pH levels were detected. The changes suggest a rearrangement of membrane composition to maintain membrane fluidity, especially under warming conditions. Individuals under warming treatment showed higher plastidial pathway activity, while acidification induced a shift in the fatty acid synthesis pathway towards the extra-plastidial pathway, indicating a need to readjust the chloroplastidial monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) lipids under thermal stress to counteract excessive membrane fluidity. Regarding PUFA fatty acids, α-linolenic acid (ALA, C18:3, n-3) showed a pronounced decrease under the combined treatment, a tendency that can be connected to reactive oxygen species (ROS) quenching and membrane remodelling. Thus, and observing the changes in the fatty acid profile, these essential molecules appear as good candidate biomarkers to detect changes in seagrass ecophysiology under acute climate change-related events. Our findings suggest that future global warming will pose a serious threat to these already endangered blue ecosystems.