Molecular response of Sargassum vulgare to acidification at volcanic CO2 vents: Insights from proteomic and metabolite analyses

Functional changes across marine habitats due to ocean acidification

Global environmental change drives diversity loss and shifts in community structure. A key challenge is to better understand the impacts on ecosystem function and to connect species and trait diversity of assemblages with ecosystem properties that are in turn linked to ecosystem functioning. Here we quantify shifts in species composition and trait diversity associated with ocean acidification (OA) by using field measurements at marine CO2 vent systems spanning four reef habitats across different depths in a temperate coastal ecosystem. We find that both species and trait diversity decreased, and that ecosystem properties (understood as the interplay between species, traits, and ecosystem function) shifted with acidification. Furthermore, shifts in trait categories such as autotrophs, filter feeders, herbivores, and habitat-forming species were habitat-specific, indicating that OA may produce divergent responses across habitats and depths. Combined, these findings reveal the importance of connecting species and trait diversity of marine benthic habitats with key ecosystem properties to anticipate the impacts of global environmental change. Our results also generate new insights on the predicted general and habitat-specific ecological consequences of OA.

Comparison and improvement of RNA extraction methods in Sargassum (Phaeophyta)

Sargassum (Sargassaceae) is widely distributed globally and plays an important role in regulating climate change, but the landscape of genomes and transcripts is less known. High-quality nucleic acids are the basis for molecular biology experiments such as high-throughput sequencing. Although extensive studies have documented methods of RNA extraction, these methods are not very applicable to Sargassum, which contains high levels of polysaccharides and polyphenols. To find a suitable method to improve the quality of RNA extracted, we compared and modified several popular RNA extraction methods and screened one practical method with three specific Sargassum spp. The results showed that three CTAB methods (denoted as Methods 1, 2, and 3) and the RNAprep Pure Plant Kit (denoted as Method 4) could, with slight modifications, effectively isolate RNA from Sargassum species, except for Method 4 used with S. fusiforme. By performing further screening, we determined Method 4 was the best choice for S. hemiphyllum and S. henslowianum, as revealed by RNA yields, RNA Integrity Number (RIN), extraction time, and unigene mapped ratio. For S. fusiforme, Methods 1, 2, and 3 showed no obvious differences among the yields, quality, or time to perform. In addition, one other method was tested, but we found the quality of the RNA extracted by TRIzol reagent methods (denoted as Method 5) performed the worst when compared with the above four methods. Therefore, our study provides four suitable methods for RNA extraction in Sargassum and is essential for future genetic exploration of Sargassum.

Seaweed metabolomics: A review on its nutrients, bioactive compounds and changes in climate change

Seaweed, an important food resource in several Asian countries, contains various metabolites, including sugars, organic acids, and amino acids; however, their content is affected by prevailing environmental conditions. This review discusses seaweed metabolomics, especially the distribution of primary and functional secondary metabolites (e.g., carotenoids, polyphenols) in seaweed. Additionally, the effects of global warming on seaweed metabolite profile changes are discussed. For example, high temperatures can increase amino acid levels in seaweeds. Overall, understanding the effects of global warming on seaweed metabolite profiles can be useful for evaluating the nutritional composition of seaweeds as food. This review provides an overview of recent applications of metabolomics in seaweed research as well as a perspective on the nutrient content and cultivation of seaweeds under climate change scenarios.

Responses of the Macroalga Ulva prolifera Müller to Ocean Acidification Revealed by Complementary NMR- and MS-Based Omics Approaches

Ocean acidification (OA) is a dramatic perturbation of seawater environments due to increasing anthropogenic emissions of CO₂. Several studies indicated that OA frequently induces marine biota stress and a reduction of biodiversity. Here, we adopted the macroalga Ulva prolifera as a model and applied a complementary multi-omics approach to investigate the metabolic profiles under normal and acidified conditions. Our results show that U. prolifera grows at higher rates in acidified environments. Consistently, we observed lower sucrose and phosphocreatine concentrations in response to a higher demand of energy for growth and a higher availability of essential amino acids, likely related to increased protein biosynthesis. In addition, pathways leading to signaling and deterrent compounds appeared perturbed. Finally, a remarkable shift was observed here for the first time in the fatty acid composition of triglycerides, with a decrease in the relative abundance of PUFAs towards an appreciable increase of palmitic acid, thus suggesting a remodeling in lipid biosynthesis. Overall, our studies revealed modulation of several biosynthetic pathways under OA conditions in which, besides the possible effects on the marine ecosystem, the metabolic changes of the alga should be taken into account considering its potential nutraceutical applications.