An invasive species called "Carpet Sea Squirt" - or "sea vomit" - has been spotted in Jersey's Elizabeth Marina.
The organism originates in Japan but has spread around the world, and was first seen in the British Isles in 2008.
Four colonies of 'sea vomit' were initially detected on the underside of several pontoons in the harbour last month.
Since then it has been found on boats in the marina.
Marine experts are concerned that the organism could damage stocks and native marine life, as well as impact marine leisure as boats become covered in the so-called "vomit".
Alastair Christie, Senior Scientific Officer for Invasive Species in Jersey, says very little can be done once the organism is well-established.
"The hope is that this current incursion is minimal and that swift removal, followed by continued monitoring, will avoid a significant infestation and the impacts will be low,” he said.
Jersey's coast and harbours will continue to be monitored to assess how far the organism has spread.
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