eDNA - Subsurface eDNA Sampling Methods
Research has also shown that simply placing filter paper or other absorbent material in an aquatic environment for a period of time can act as an effective eDNA collection mechanism that is nearly as effective as active filtration of water to collect an eDNA sample. To do this, you can mount the filter paper in some manner and deploy at depths and locations of interest.
For example, a research group has used 3D printing technology to build an apparatus, called the PESCA, to hold filter paper and orient it such that water flows through it in current-influenced locations. WilderLab, an eDNA service provider, has also developed passive eDNA sample kits for deployment.
Autonomous eDNA sampling
Increasingly, technology for autonomous eDNA sample collection and filtration is being developed.
Many of the newest sampling devices are reviewed in this publication A State-Of-The-Art Review of Aquatic eDNA SamplingTechnologies and Instrumentation: Advancements,Challenges, and Future Prospects. Autonomous eDNA sample collection was pioneered by the Monterey Bay Aquarium Research Institute (MBARI) with its Environmental Sample Processor, with many new devices being developed since, including the RoCSI, Ocean Diagnostics Ascension eDNA sampler and the Dartmouth Ocean Technologies eDNA Sampler. The Ocean Diagnostics Ascension, in particular, is a possible substitute for using niskins to collect depth profiles of eDNA samples while the other autonomous devices are often deployed at a fixed depth and location to collect samples over time. Some companies are incorporating these eDNA sampling devices into their autonomous sampling platforms as a means to remotely collect eDNA samples over space and time.