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\/).Using this protocol, RNA and DNA has been\u00a0used for molecular analyses such as tag sequencing (16S or 18S), (meta)genomic, or (meta)transcriptomic applicationsSee other Caron lab protocols that detail field work sampling and downstream PCR amplification\/libray prep for microbial eukaryotic-specific tag sequencing (18S rRNA gene).\nList of materials needed before starting is in\u00a0Guidelines.