Curated OJIP fluorescence and culture data for reagent-free prediction of free-ammonia toxicity in Chlorella, Acutodesmus, and Arthrospira

This dataset contains curated chlorophyll fluorescence and culture-condition data supporting the following article: Kishi, M.; Karachaliou, P.; Fujiki, T.; Noguchi Aita, M.; Muñoz, R. “Reagent-Free Prediction of Free-Ammonia Toxicity in Algal Systems Using Chlorophyll Fluorescence Transients and Interpretable Sparse Regression.” Environmental Science & Technology, 2026. https://doi.org/10.1021/acs.est.5c18003 The dataset includes OJIP fluorescence-derived parameters, OJIP curve data, selected culture metadata, free-ammonia calculations, auxiliary light-curve features, feature-set information, and quality-control flags for Chlorella vulgaris, Acutodesmus obliquus, and Arthrospira platensis exposed to controlled NH3 treatments. Culture 1 corresponds to the main ammonia-toxicity exposure experiments. Culture 2 corresponds to the independent external-validation experiments described in the article. These data were obtained from controlled laboratory cultures and not from real wastewater matrices. Free-ammonia concentrations were calculated from total ammoniacal nitrogen, pH, temperature, and ionic strength for each sampling time. OJIP-derived parameters were obtained after logarithmic resampling, spline smoothing, normalization, parameter calculation, and quality control. Quality-control flags indicate whether each measurement passed the predefined criteria used for model construction and evaluation. The ZIP file contains the complete dataset package, including CSV files, README, data dictionary, and a consolidated Excel workbook. The standalone Excel file is provided as a convenience copy for direct inspection. The associated Python code is archived separately as OJIP Lasso on Zenodo: https://doi.org/10.5281/zenodo.17398400