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Aquatic invasive species (AIS) represent a significant threat to aquatic ecosystems, and early detection is a crucial step in mitigating risks of establishment and spread. In this study, we designed and/or optimized species-specific qPCR assays for 9 marine invertebrates considered invasive in Eastern Canada for use in conjunction with environmental DNA (eDNA) sampling. All qPCR assays showed high analytical sensitivity with theoretical limit of detection (LOD) ranging from 0.045 to 9.24 picogram (pg) of DNA. Comparison of two eDNA water sampling methods showed an increased detection sensitivity using the grab sample approach. eDNA AIS detections were also compared to results obtained using a traditional in situ biofouling monitoring method (i.e., biofouling monitoring lines), and a high concordance between the two was observed. We also determined temporal variability in the amount of DNA found in the environment for some of the targeted AIS, which will help target seasonal monitoring efforts. The results provided herein clearly demonstrate the usefulness of including eDNA for early AIS detection in ongoing monitoring, rapid response investigations and mitigation/eradication efforts. [ABSTRACT FROM AUTHOR]

A mechanistic understanding of the factors that influence establishment and secondary spread of introduced species is critical for predicting the spatial extent and magnitude of negative impacts of species invasions. In the northwest Atlantic, an ecologically significant invasive bryozoan (Membranipora membranacea) has expanded its range northwards over the last 30 years. Warm ocean temperature has been linked to population outbreaks of M. membranacea within its established invasive range in southwestern Nova Scotia; however, rates of spread and the physical and biological factors affecting establishment of founding populations have not been explicitly quantified. Here, we use unique baseline data on presence/absence and abundance of this bryozoan near its current northern range limit to quantify rates of spread and identify factors influencing its establishment in three regions in the Gulf of St. Lawrence. Except for one potential incident of human-facilitated long-distance dispersal, the rate of spread of M. membranacea in the northwest Atlantic was comparable to that of other invasive marine invertebrates. Contrary to our predictions based on long-established populations in Nova Scotia, the abundance of M. membranacea was not strongly related to regional differences in ocean temperature at its northern range limit. Our results suggest that colder temperatures are not limiting the northward spread of this bryozoan in the northwest Atlantic. Instead, relationships between temperature and abundance of M. membranacea in the Gulf of St. Lawrence may be moderated by a lack of available kelp substrate. Our findings, therefore, have important implications regarding the potential for M. membranacea to impact vulnerable Arctic ecosystems where laminarian kelps are widespread. [ABSTRACT FROM AUTHOR]

We report new observations of two invasive ascidian species, the solitary Ascidiella aspersa and the colonial Diplosoma listerianum, from Eastern Canada, which include some records from new sites. Because these species share many superficial characteristics with native and non-native species in the region, identifications based on detailed taxonomic studies of internal structures--and not only on external features--are essential and can complement molecular methods. In this report, specimens of A. aspersa collected from Nova Scotia in 2013 and D. listerianum from New Brunswick and Quebec in 2017 were described morphologically to confirm species identity. Specimens of both were collected one year after initial discoveries in Nova Scotia and New Brunswick, respectively. Specimens of D. listerianum from Quebec were collected after a six-year hiatus. This report contributes a new record of A. aspersa 30 km (by sea) north of the site of the first record in Canada. It also confirms the first record of D. listerianum and documents its rapid spread in New Brunswick. This report is the first time that A. aspersa from Eastern Canada and D. listerianum from New Brunswick and the second time that D. listerianum from Quebec was explicitly identified based on an examination of internal features. Species confirmation of these easily overlooked or misidentified taxa contributes a time-stamp on current invasion fronts and suggests that the risk of further introductions and spread of these invasive species is present at un-invaded sites throughout Eastern Canada. [ABSTRACT FROM AUTHOR]

In eastern Canada, the initial suspected discovery of the non-indigenous colonial ascidian Diplosoma listerianum in Quebec was followed by species identification and increased awareness for its detection in the neighbouring provinces of Nova Scotia and Prince Edward Island. A phylogenetic analysis was conducted based on sequences generated from the 18S ribosomal DNA gene isolated from tissues of two Canadian samples (Quebec and Nova Scotia) and samples from several species belonging to the Diplosoma genus, which confirmed the species identity of the eastern Canadian specimens. Colonies of D. listerianum found in Quebec (2008) and Nova Scotia (2012) are currently the only tissue records of this species in eastern Canada. Water samples of concentrated plankton collected in Quebec (2010 and 2011) and in Prince Edward Island (2011) tested PCR positive for D. listerianum DNA, but colonies were not observed concurrently. As a case study for early detection, this paper documents how D. listerianum was detected in eastern Canada by different groups (government monitoring, academic research) and with different methods (dive surveys, genetic analysis of water samples, collector plates). This case study suggests that the co-operation between groups and the breadth of the methods used contributed to the early detection of this species in three eastern Canadian provinces. In particular, we show that (i) partnerships between government, academia, and industry, (ii) a national capacity for species-specific molecular detection tools, and (iii) the recognition that the effectiveness and limitations of different monitoring methods may be site-specific can have positive early detection and monitoring outcomes. [ABSTRACT FROM AUTHOR]