Detecting the minimum reliable sample volume is the first step toward standardizing the eDNA metabarcoding for detecting marine phytoplankton (including microzooplankton) species. Future work focusing on harmonizing the subsequent steps in the workflow is needed. For monitoring purposes, it would be beneficial to utilize a consistent molecular marker between projects and monitoring programs. Therefore, as a next step, comparison of different molecular markers could be conducted to identify the universal marker most suitable for detecting a wide range of phytoplankton species. Additionally, it is crucial to improve reference databases with taxonomically verified sequences from various phytoplankton species to ensure accurate taxonomic identification of species based on eDNA.