Passive Versus Active eDNA Sampling: A Field Comparison of Methods for Detecting Non-Indigenous Species on Marine Structures

Passive eDNA samplers promise a cheaper and simpler way to survey communities on structures that are difficult and expensive to reach, but the approach is new enough that its performance against established methods remains largely untested. This field experiment benchmarks passive samplers (sponges and filters soaked in place for 24 hours) against active methods (water filtration and plankton tows), scoring each against the true fouling community recovered from settlement plates on the three criteria that decide whether a protocol gets adopted: how much of the community it detects, how long it takes to deploy, and what it costs.