Swedish Agency for Marine and Water Management

Denna rapport beskriver metod och resultat för identifiering av optimala övervakningsstationer för tidigt upptäckt av marina invasiva främmande arter samt uppföljning av dess spridningsmönster. Metoden är baserad på beräkning av en samlad invasionsrisk för 34 målarter som analyseras individuellt och samlade i relevanta ekologiska grupperingar som till exempel sötvattenstoleranta arter, marina arter eller bentiska arter. I analysen ingår tre faktorer:

• Geografisk fördelning av lämpliga habitat beräknat med hjälp av utbredningsmodeller för varje art.

• Artspecifik riskbedömning.

• Introduktionsrisk i samband med fartygstrafik och vattenströmmar. 

Resultatet pekar på två separata spridningsmönster för invasiva arter till marina miljöer i Sverige; spridning av marina arter längs nordeuropeiska kustvatten och spridning av sötvattenstoleranta arter via den europeiska kontinenten. Dessa två spridningsvägar analyserades separat och resultaten stöder en jämn fördelning av övervakningsstationer längs den svenska kusten mellan Strömstad och Gävle, med fokus på de områden som pekas ut av de marina modellerna på västkusten och de områden som pekas ut av sötvattensmodellerna på östkusten. De mest lämpliga övervakningsplatserna är hamnområden.

Collecting marine hard bottom organism with autonomous techniques in combination with DNA analyses for species identification has proven to be efficient monitoring of biodiversity and detection of non-indigenous species. This methodology provides well to early warning surveillance of invasiv alien species. 

The University of Gothenburg has, on behalf of the Swedish Agency for Marine and Water Management and in collaboration with SeAnalytics AB, carried out two pilot studies to investigate whether plankton samples and settling panels in combination with DNA-based species identification is an effective method for early detection and continuous monitoring of non-indigenous species (NIS). The surveys were conducted during the winter, spring and summer of 2020 at various locations along the Swedish west coast, from the fjord Brofjorden in the north to Helsingborg in the south. The sites were chosen based on previous modelling (Bergkvist et al. 2020a) hotspots for introduction of alien species.

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 or 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) by the Swedish Species Information Center 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.

Global shipping carries over 90 percent of world goods and is expected to play an increasing role in the future in terms of global trade. Shipping affects the environment in various ways, one being the transfer of harmful aquatic organisms and pathogens with ballast water releases. The significance of ballast water as a vector for foreign and invasive alien species (IAS) eventually led to the adoption of the UN International Convention for the Control and Management of Ship’s Ballast Water and Sediments. The Convention entered into force in September 2017, and states that the spread of harmful (invasive) species with ships' ballast water and sediment shall be prevented and ultimately eliminated. It is the responsibility of ships in international traffic to install facilities for the management of ballast water, although it is possible to apply for exemption subject to certain conditions. In order to apply for exemption, listed IAS which are likely to be spread by ship transport must be investigated in current ports. Port surveys are also important for management purposes.   

In this report, traditional methods are compared with novel approaches of conducting fauna surveys in port areas. To this end, plankton and benthos samples were taken and then manually sorted to identify all specimens to species or higher taxonomic level (genus, family, phylum). At the same time, parallel samples were processed with a genomic approach where DNA was extracted from bulk samples without previous sorting, and species were identified based on DNA metabarcoding. DNA was sequenced using next generation sequencing techniques (Illumina), and the resulting sequences were matched against taxonomic reference sequences from public archives and target species databases.  The traditional method found 212 taxa overall, of which 131 taxa (62 percent) could be identified to species level. Four of these are listed as nonindigenous/invasive alien, and two of them are on the target species list of the HELCOM/OSPAR area: Mnemiopsis leydi och Crassostrea gigas. The DNA method recognized 153 taxa, of which 119 taxa (77 percent) could be determined to species level. This approach found five invasive alien species, all on the target species list : Acartia tonsa, Crassostrea gigas, Crepidula fornicata, Amphibalanus improvisus and Caprella mutica. Mnemiopsis leydi had been excluded from the plankton samples before they were put into ethanol and prepared for DNA extractions. Of the EU list of IAS where only one marine species exists, no match was made.  More species were identified from the settling plates (75 percent) and the benthic samples (82 percent), using the manual method compared to the DNAbased (56 percent and 64 percent respectively). However, when it comes to the zooplankton, the DNA based method identified more species (66 percent), compared to the traditional approach (9 percent) and found four invasive alien species, compared to none in the case of the traditional method. The DNA based method found three invasive species in the benthic sample, compared to none analysed by the traditional method.   A conclusion of the comparison between the two methods is that the traditional method found, and identified, more species in general. However, the DNA based method found (i) more invasive alien species (higher specificity); (ii) found invasive alien species more often (higher taxonomic sensitivity); and (iii) could detect invasive alien species in the plankton samples (early warning).