IMIS

The settling panel study followed the protocols for monitoring of hard bottom organisms as set up in the international ARMS (Autonomous Reef Monitoring Structures) project (Leray & Knowlton, 2015; Obst et al. 2020). A total of 16 ARMS settling panels were deployed during the winter and spring months and were submerged between 3–4 months before taken up for further processing and analysis. Plankton samples were taken from six of these sites, on three different occasions, and two samples from each site / each occasion. DNA was extracted from the settling panels and plankton and metabarcoding libraries prepared for three molecular markers (COI, 18S, ITS), together with positive and negative controls, altogether 284 libraries. Thirty-four NIS were recorded, of which fourteen are classified as invasive alien species (IAS) nationally and on the list of Invasive Alien Species of Union concern. The remaining 20 NIS are listed on the Aqua-NIS list and need to be further investigated for their alien and invasive status in the country. The tested methods perform well both for early detection of unknown NIS as well as for regular monitoring of already known NIS. The chosen markers COI and 18S performed well, while ITS did not produce sufficient species observations and can be omitted as a marker gene.