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In this experimental study the patterns in early marine biofouling communities and possible implications for surveillance and environmental management were explored using metabarcoding, viz. 18S ribosomal RNA gene barcoding in combination with high-throughput sequencing. The community structure of eukaryotic assemblages and the patterns of initial succession were assessed from settlement plates deployed in a busy port for one, five and 15 days. The metabarcoding results were verified with traditional morphological identification of taxa from selected experimental plates. Metabarcoding analysis identified > 400 taxa at a comparatively low taxonomic level and morphological analysis resulted in the detection of 25 taxa at varying levels of resolution. Despite the differences in resolution, data from both methods were consistent at high taxonomic levels and similar patterns in community shifts were observed. A high percentage of sequences belonging to genera known to contain non-indigenous species (NIS) were detected after exposure for only one day.

Tunicates are useful models for exploring microbiomes because they have an innate immune system resembling that of chordates. Automated ribosomal RNA intergenic spacer analysis and High-Throughput Sequencing were used to compare the tunic microbiomes of Ciona robusta (formerly Ciona intestinalis type A), Ciona savignyi, Botrylloides leachi and Botryllus schlosseri sampled from three distinct locations with limited genetic connectivity. Bacterial phylotype profiles were conserved within each species, and there were no detectable differences between tunic and tunic + cuticle subsamples from an individual. Bacterial operational taxonomic unit (OTU) diversity was lowest for C. savignyi (320 ± 190 OTUs) and highest for B. schlosseri (1260 ± 190 OTUs). Each species had a distinct set of bacterial OTUs (pseudo-F = 3.0, p > 0.001), with the exception of B. leachi and B. schlosseri from one sampling location (t = 1.2, p = 0.09). Of note were OTUs assigned to Alphaproteobacteria from C. robusta plus Phyllobacteriaceae and Endozoicomonas from C. savignyi. These OTUs contributed 51, 22 and 10% of sequence reads, respectively, and are related to known bacterial symbionts. The within-species conservation of core OTUs across three distinct and co-occurring populations of tunicates provides compelling evidence that these tunicates foster defined microbiomes.

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Marine biofilms are precursors for colonization by larger fouling organisms, including non-indigenous species (NIS). In this study, high-throughput sequencing (HTS) of 18S rRNA metabarcodes was used to investigate four sampling methods (modified syringe, sterilized sponge, underwater tape and sterilized swab) for characterizing eukaryotic communities in marine biofilms. Perspex™ plates were sampled in and out of water. DNA collected with tape did not amplify. Otherwise, there were no statistical differences in communities among the remaining three sampling devices or between the two environments. Sterilized sponges are recommended for ease of use underwater. In-depth HTS analysis identified diverse eukaryotic communities, dominated by Metazoa and Chromoalveolata. Among the latter, diatoms (Bacillariophyceae) were particularly abundant (33% of reads assigned to Chromalveolata). The NIS Ciona savignyi was detected in all samples. The application of HTS in marine biofilm surveillance could facilitate early detection of NIS, improving the probability of successful eradication.

Hopkins, G. A., and Forrest, B. M. 2008. Management options for vessel hull fouling: an overview of risks posed by in-water cleaning. – ICES Journal of Marine Science, 65: 811–815. Hull fouling has been identified as an important pathway for the spread of non-indigenous marine species. However, the management of associated biosecurity risks has proven challenging. Left unmanaged, a fouled vessel can pose a biosecurity risk through the detachment and dispersal of viable material, and through spawning by adult taxa upon arrival in a recipient port or region. These risks can be managed effectively through the removal of the vessel to land for defouling (e.g. dry-docking). However, alternative methods are needed for small (e.g. recreational) vessels, as well as for large vessels fouled outside their dry-docking schedule. Among the various treatment options, in-water cleaning is relatively common, although some countries have placed restrictions on this method because of perceived biosecurity risks. Here, we present a conceptual framework that identifies risks posed by in-water cleaning compared with alternatives, including no management. Decisions on the appropriate management option will be influenced by many factors, including the species present, the level of fouling, and the time a vessel spends in a recipient region. It is important that any regulatory changes regarding in-water defouling be supported by relevant research that quantifies the risks associated with the various management options.

Summary 1.Biofouling, the accumulation of biological growth on submerged surfaces such vessel hulls and artificial structures, is an important transport pathway that can facilitate the establishment of marine non-indigenous species in new locations. Despite efforts to develop effective tools to eradicate newly established populations before they become widespread and beyond control, eradication successes are scarce in the marine environment. This paper describes a dredge-based eradication of the brown mussel Perna perna from a deep (c. 44 m) soft-sediment habitat in central New Zealand, following the discovery of this species amongst biofouling organisms physically removed (i.e. defouled) from a drilling rig. 2. We evaluated the efficacy of dredging in removing P. perna and other target species, and determined whether a density-based eradication success criterion had been achieved. The catchability coefficient (q) of the defouled material was estimated using catch data, and the dredge efficiency (E) was determined. Initial and remaining mussel densities were then calculated using estimates of E. The reliability of these estimates was tested by simulations. 3. A total of 227 dredge tows covering c. 94% of a 12AE6 ha target area were undertaken, and an estimated 35 tonnes of material defouled from the rig was dredged from the seabed and disposed of in a landfill. 4. Estimates of q and E were 0AE0054 and 0AE30 (respectively) and mussel densities at the completion of the eradication programme were estimated to be c. 0AE5 m )2 , well below the success criterion of 10 m )2 . From our simulations, it was estimated that 71 dredge tows would be required to remove 50% of the initial population, whilst 232 dredge tows would be needed to achieve a 90% reduction in population size. 5. Synthesis and applications. The eradication of non-indigenous bivalves from a relatively deep (>40 m) soft-sediment environment is unprecedented and highlights that, with appropriate tools and other resources, eradication is feasible even in challenging circumstances. Where complete elimination of a pest is not feasible, alternative density-based success criteria can be developed that, if achieved, can effectively mitigate risks. This study highlights the need for further development of both vector treatment options and pest eradication tools, and improved policy surrounding in-water defouling in the coastal environment.

In June 2012 a single non-native snakehead fish was captured by local officials in a small pond within an urban park in Burnaby, British Columbia. This single snakehead fish garnered significant attention in the local and national media. DNA analysis determined it to be a blotched snakehead (Channa maculata) or possibly a hybrid; a warm water species native to China and Vietnam which is commonly sold in the live food fish trade, and occasionally kept by hobbyists. By collecting prey items from the pond and snakehead specimens from fish markets we used a novel stable isotope approach to estimate how long it had been since the snakehead had been released into the pond. Using a diet-switching tissue turnover model, we estimated that the snakehead was in the pond between 33 and 93 days. Subsequently, provincial legislation was amended to ban all species of snakehead fish, as well as numerous other potentially invasive fish and invertebrate species.