Water testing could identify new species in Guernsey

Friday, 17 April 2026 07:10

The first round of water sampling that could identify new species in Guernsey is complete.

The Nature Commission has teamed up with Guernsey Water to gather eDNA (environmental DNA) which is the biological footprint left by small organisms that has only recently been able to be screened.

26 samples have been taken from douits, streams, and ponds across the island, and 26 more will be collected in October.

A lab in Wales, Trace Biomonitoring, will analyse the samples to identify which species of animals and plants are present.

They are focusing on fish, amphibians, algae and bacteria.

Commission CEO Jessi Jennings says the idea came about after data gaps were identified in the 2024 State of Nature report.

"We currently know very little about the ecology and the species in our freshwater environments.

"Essentially, we can't manage these things because we haven't measured them.

"(eDNA testing) is a really useful way to get lots and lots of species data without a hugely time-consuming process, so we thought that's a really great way to get our baseline for our freshwater species inventory for Guernsey.

"It's been really great to be able to work with Guernsey Water. A lot of the sites that we were interested in sampling are Guernsey Water assets, and of course, the results are going to be useful for those guys as well, because the presence of certain invertebrates in our freshwater is an indication of the quality of that water."

At each site, a syringe is used to collect a small amount of water, which is then filtered, and fixative is added to preserve any eDNA present.

Water quality scientist Tim Harris says the process may confirm the presence of some rumoured species in Guernsey.

"People talk about how they used to catch minnows in the water lanes when they were children, and that brown trout were present in some of the streams.

"We know what should be present because of where Guernsey sits within Europe, but we are hoping for a few surprises."