This protocol describes the extraction process of RNA and\/or DNA from marine environmental samples. Samples are assumed to be collected via filtering sample seawater onto filters. Filters are then flash frozen in the first lysis buffer. The protocol describes the steps used to lyse and separate material from filters and use the lysate for RNA and\/or DNA extraction using Qiagen extraction kits (e.g. https:\/\/www.qiagen.com\/us\/shop\/Sample-Technologies\/Combined-Sample-Technologies\/).\u00a0Downstream RNA and DNA is used for molecular analyses such as tag sequencing (16S or 18S), (meta)genomic, or (meta)transcriptomic applications.\n\nList of materials needed before starting is in\u00a0Guidelines.