A low-cost DNA sampling device could help scientists monitor marine wildlife more widely and affordably, according to new research conducted off the coast of Cornwall.

The study – led by researchers at the University of Exeter – compared a conventional environmental DNA (eDNA) sampling technique with a cheaper, simpler system known as Metaprobe 2.0.

Environmental DNA analysis identifies genetic traces left behind by organisms in the water – including skin cells, mucus, and excrement – enabling scientists to detect species without physically seeing or catching them. While eDNA is increasingly used in marine monitoring, traditional sampling approaches can be costly and logistically challenging.

To test whether a more accessible option could be effective, researchers evaluated the performance of the Metaprobe 2.0 – a plastic sphere containing rolls of gauze that is dropped into the sea, where it passively collects DNA before being retrieved for analysis.

Although the standard method slightly outperformed the experimental device, the Metaprobes delivered consistent results and detected the same target species in Cornish waters, including the European anchovy, Atlantic mackerel, and Blue shark.

A fourth species monitored in the study – the Thresher shark – was not detected by either technique.

While the research focused on just four species, a single eDNA sample can reveal the presence of a wide range of marine life. In the future, tools such as Metaprobes could potentially help scientists monitor UK waters for rare or unexpected arrivals, including the elusive Great white shark.

“With marine biodiversity under increasing pressure from climate change, overfishing and habitat degradation, governments and conservation organisations are keen to use eDNA at scale,” said Dr Molly Kressler, from the Centre for Ecology and Conservation at Exeter’s Penryn Campus in Cornwall.

“Our study suggests that Metaprobe 2.0, which is cheap and easy to deploy, performs well against a standard eDNA method that costs significantly more. Metaprobes might widen the accessibility of eDNA monitoring in the future – allowing sampling in remote places, or when cost is a significant factor.”

The project relied heavily on local support from sailors and tour operators across the South West. Dr Kressler trained staff from Marine Discovery Penzance to deploy and retrieve the Metaprobes, and joined vessels from Padstow Sea Safaris to collect seawater samples while delivering science talks to passengers.

“I also enlisted a citizen-science sailor fleet who would go out and collect samples for me, as they travelled around the South West,” Dr Kressler added. “I recruited volunteers via local yacht clubs and social media. In one case, someone in New Zealand saw my post and they knew a sailor in Cornwall, who then took part – showing how online appeals can go around the world and back.”

The researchers say that eDNA monitoring may also prove important for detecting species that are currently rare or absent in UK waters.

Commenting on great white sharks – which have never been positively identified in UK waters – Dr Kressler said: “With warming waters and seal populations increasing, it’s likely that we will see a white shark here within a few decades. At present, any white shark coming here would have to be very large and very bold to make the journey from their current hot spots like the northwest Atlantic.

“Given the nature and behaviour of white sharks, eDNA would be the primary way of knowing they were here.”

The research was funded through an Exeter Marine student project grant and published in the journal Environmental DNA under the title “Passive gauze-based eDNA sampler proves efficient and cost-effective in the marine environment.”

Instructions for printing and deploying a Metaprobe 2.0 have been made publicly available by the authors, who also encourage interested citizen scientists to get involved in future sampling efforts.

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