Ulva spp. have outstanding survivability in copper-rich environments, but research into the interactions between these algae and copper is required. This study combined transcriptomics, proteomics, and metabolomics to investigate the expression of various metabolites in Ulva prolifera after exposure to 10 mg L −1 of copper sulfate for 12 h. The results showed that copper stress in U. prolifera mainly manifested as a reduction in transcription and translation, which was related to gene expression, protein activity, and metabolite content in cell division and energy metabolism. However, the resistance, signal transduction, and metabolism of U. prolifera were enhanced to respond actively to acute copper stress in many aspects. These findings demonstrate the impact of 12 h of 10 mg L −1 copper sulfate exposure on U. prolifera.

The main algal species of Ulva prolifera green tide in the coastal areas of China are four species, but after reaching the coast of Qingdao, U. prolifera becomes the dominant species, where the light intensity is one of the most important influencing factors. In order to explore the effects of short-term high light stress on the internal molecular level of cells and its coping mechanism, the transcriptome, proteome, metabolome, and lipid data of U. prolifera were collected. The algae were cultivated in high light environment conditions (400 μmol·m−2·s−1) for 12 h and measured, and the data with greater relative difference (p < 0.05) were selected, then analyzed with the KEGG pathway. The results showed that the high light stress inhibited the assimilation of U. prolifera, destroyed the cell structure, and arrested its growth and development. Cells entered the emergency defense state, the TCA cycle was weakened, and the energy consumption processes such as DNA activation, RNA transcription, protein synthesis and degradation, and lipid alienation were inhibited. A gradual increase in the proportion of the C4 pathway was recorded. This study showed that U. prolifera can reduce the reactive oxygen species produced by high light stress, inhibit respiration, and reduce the generation of NADPH. At the same time, the C3 pathway began to change to the C4 pathway which consumed more energy. Moreover, this research provides the basis for the study of algae coping with high light stress.

Ulva prolifera is the main species of green tide algae in the Yellow Sea, China, and its growth process is significantly affected by light intensity. The work used four omics to reveal the molecular mechanism of U. prolifera responding to high light. Four-omics conjoint analysis showed the interconversion of sugars in the algae, fatty acid synthesis, steroid synthesis, photosynthesis, pyrimidine metabolism and carbohydrate metabolism. After 12 hours of high light, the photosynthetic capacity of U. prolifera increased and the carbon sequestration mode changed from C3 pathway to C4 pathway. At the same time, the glucose metabolism pathway was enhanced, but the energy metabolism pathway was weakened, and the overall energy consumption showed a decreasing trend. Different resistance modes have different response mechanisms to high light stress. In addition, the growth, development and reproduction of U. prolifera were inhibited, indicating that U. prolifera may be in a dormant state after 12 hours of hight light stress, reducing energy consumption caused by unnecessary developmental physiological processes. The response mechanism of U. prolifera to high light stress was preliminarily obtained through the combined analysis of four kinds of omics, which provided the basis for future research.

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