Compilation of data on carbon stable isotopes in the macroalga Ulva spp. from an extensive literature data collection and from selected New England estuaries

This dataset is Supplementary materials for the article Lloret, J. 2025. High variability in carbon stable isotopes in the macroalga Ulva spp. and implications for eutrophication indicators. Scientific Reports, 15: 40889 (https://doi.org/10.1038/s41598-025-24788-w) An extensive literature search using online tools and bibliographic databases, including Web of Science (http://isiknowledge.com), and Google Scholar (http://scholar.google.com), was conducted by searching the keywords “stable isotope” AND “Ulva OR Enteromorpha”. Results from this search were carefully screened to ensure included data was relevant to this study. Several criteria were used to determine whether data could be included. Only full-tissue, naturally occurring δ13C algal signatures were used. Data on compound-specific stable isotope analyses, experimental manipulations and isotope enrichment experiments were excluded. When available, unique individual observations were used, but if data were aggregated and reported as averages, they were included only when the number of samples was small and collected over a relatively limited spatial area. A total of 188 publications, including 173 scientific journal articles, 10 theses, and 5 technical reports published between 1964 and 2025, were selected. The complete list of literature sources is included as Supplementary Materials inj the original article. Data presented in graphs were extracted by using the WebPlotDigitizer V5 software. Information on the sampling site location and typology was also collected.The dataset also includes observations from a comprehensive dataset from macroalgal surveys conducted in a subset of New England sites.