s part of the Ocean Molecular Ecology (OME) group’s effort to optimize eDNA collection techniques and broaden our sample collection capabilities at sea, we are conducting a study to compare a new filter produced by an American small business, the Smith-Root self preserving eDNA filter to our current filter, the Millipore sterivex capsule filter. The collection and filtration of eDNA samples at sea is limited in part by the technical skills required to filter and preserve these sensitive samples without contamination. With our current filter, the flammable preservative and low-temperature storage requirements also present a barrier to shipping and sample storage in some field applications.
The self-preserving filter, developed by a small business in Vancouver WA, is designed to capture and preserve eDNA from multicellular organisms. It has been found to perform as well as ethanol-based preservation for a 6 month period. Rather than a preservative, the Smith-Root filter utilizes a proprietary desiccating filter housing to preserve captured DNA and cells, eliminating the need for chemical preservatives. This design simplifies operation, requires less training, and streamlines shipping. However, these filters have not been tested against the sterivex filter, nor have they been tested on their ability to capture DNA from single-celled organisms. Our current study aims to address these gaps by testing the sterivex head-to-head against the Smith-Root filter using the same filter material and pore size.
For this study, Han Weinrich and Zack Gold collected water samples from local fresh and seawater sources alongside water from the Olympic Coast National Marine Sanctuary, then they filtered them in the lab - half with sterivex filters and half with the Smith-Root filters. To avoid any degradation of DNA before preservation, Han and Zack filtered the samples immediately after collection, resulting in several 12 hour days. DNA extractions at six time points, from one day to six months post-collection, will assess the preservation performance of the Smith-Root filter relative to the sterivex filter. Preliminary results from extractions conducted up to three months post-collection indicate that the Smith-Root filter preserves DNA comparably to the sterivex filter. Further analyzes will include sequencing the extractions to determine if both filters capture and preserve the same organisms at the same proportions - a critical metric for the OME as we aim to capture biodiversity at all levels of the ecosystem, from bacteria to whales.
If the Smith-Root filters perform comparably to the sterivex in meeting OME's eDNA objectives, they may offer an alternative to sterivex filters in certain field applications - saving time and space on research vessels while enabling eDNA monitoring in a broader range of environments. In addition, the National Aquatic eDNA Strategy seeks to advance eDNA sampling technologies by developing low-cost, high fidelity devices to enable large-scale collection. The Smith-Root filter could be employed in the development of a new eDNA sampler.
