This dataset compiles previously published literature reporting threshold concentrations and toxicological responses of marine phytoplankton to dissolved trace metals. The dataset focuses on copper (Cu), cadmium (Cd), zinc (Zn), manganese (Mn), iron (Fe), and lead (Pb), and includes both field-based and laboratory-based experimental studies. For each study, the dataset records the geographic location of phytoplankton collection, the experimental setting or type (in-situ, on-board, or on-land laboratory experiments), the growth medium used (where applicable) and the dissolved trace metal investigated. Reported threshold concentrations (nM) include LC50 or IC50 values, along with exposure duration and response variables (e.g., growth rate, cell density, chlorophyll-a content, or pigment concentration) where available. The dataset further documents the observed biological impact, phytoplankton taxonomic identity, and full bibliographic references to the original studies. All values are reported as published in the source literature, including associated uncertainties, to preserve comparability and transparency. This dataset is intended to support meta-analyses, environmental risk assessments, and studies on trace metal toxicity and biogeochemical cycling in marine ecosystems.