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Invasive species can introduce parasites to, and/or acquire new parasites from, novel regions, thereby greatly influencing community interactions, including symbiotic relationships involving parasites. Host-switching of native and non-native parasites could enhance or dilute parasite transmission and spread among hosts. We investigated the effect of host invasion on trematode parasitism in 2 Newfoundland (Canada) bays: one invaded by European green crabs Carcinus maenas and the other not yet invaded. To determine the influence of C. maenas on host-parasite relationships, we assessed trematode prevalence in 3 native hosts: 2 Littorina spp. snails and Atlantic rock crabs Cancer irroratus (first- and second-intermediate hosts for microphallid trematodes, respectively). We found no difference in trematode prevalence between the bays among the 4 host species. However, cyst abundance was significantly higher in C. maenas versus C. irroratus in the bay where the crab distributions overlap, while it was lower in C. irroratus in the invaded versus uninvaded bay, suggesting a dilution of infection in the native host. Sequencing data of microphallid trematodes detected 4 genetically divergent lineages: a cosmopolitan lineage found in all host species; 2 lineages dominant in C. irroratus, suggesting a native origin for the trematodes that now use C. maenas as an additional host; and 1 lineage represented just in C. maenas in Europe. This is the first study to demonstrate the magnitude of trematode infection in crab hosts in Newfoundland, including the commercially valuable native C. irroratus. Our results demonstrate the influence that species introductions can have on parasite life cycles in native systems under recent host invasion.

Characterising interspecific interaction strengths, combined with population abundances of prey and their novel predators, is critical to develop predictive invasion ecology. This is especially true of aquatic invasive species, which can pose a significant threat to the structure and stability of the ecosystems to which they are introduced. Here, we investigated consumer-resource dynamics of two globally-established aquatic invasive species, European green crab (Carcinus maenas) and brown trout (Salmo trutta). We explored the mediating effect of prey density on predatory impact in these invaders relative to functionally analogous native rock crab (Cancer irroratus) and Atlantic salmon (Salmo salar), respectively, feeding on shared prey (Mytilus sp. and Tenebrio molitor, respectively). We subsequently combined feeding rates with each predator’s regional abundance to forecast relative ecological impacts. All predators demonstrated potentially destabilising Type II functional responses towards prey, with native rock crab and invasive brown trout exhibiting greater per capita impacts relative to their trophic analogues. Functional Response Ratios (attack rates divided by handling times) were higher for both invasive species, reflecting greater overall per capita effects compared to natives. Impact projections that incorporated predator abundances with per capita effects predicted severe impacts by European green crabs. However, brown trout, despite possessing higher per capita effects than Atlantic salmon, are projected to have low impact owing to currently low abundances in the sampled watershed. Should brown trout density increase sixfold, we predict it would exert higher impact than Atlantic salmon. Such impact-forecasting metrics and methods are thus vital tools to assist in the determination of current and future adverse impacts associated with aquatic invasive species.

We developed a new predictive approach to evaluate the relative invasion hazard posed by recreational boats as vectors for non-indigenous species (NIS) in marine ecoregions on the Atlantic coast of Canada. It combines data from behavioral boater questionnaires, surveys of boat macrofouling, and an extensive NIS monitoring program in marinas. The relative invasion hazard posed by boats in nine marine ecoregions was estimated by combining information on NIS infestation levels in source ecoregions, the probability that boats will be fouled, boat movements and environmental similarity between source and receiving marinas, and estimates of annual recreational traffic within and between ecoregions. A total of 52.1% of surveyed boats had macrofouling on hull or niche areas, suggesting a high potential for NIS transport. High-risk boats were those that had spent extended periods in water, traveled extensively from invaded locations, and received little maintenance. Further, the high degree of connectivity between and within ecoregions, and high survival probabilities of NIS, highlight the threat of NIS introduction and spread via recreational boating in Atlantic Canadian waters. Of all Atlantic Canadian ecoregions, the Scotian Shelf ecoregion was classified as having the “Highest” Final Hazard score. However, boats with Intermediate to Highest scores travel to most ecoregions, underlining the importance of this vector to the introduction and spread of NIS in Atlantic Canadian coast. A simulated out-of-water cleaning after 3 months reduced the hazard in ecoregions with greater scores.

Aim: The introduction of aquatic non-indigenous species (ANS) has become a major driver for global changes in species biogeography. We examined spatial patterns and temporal trends of ANS detections since 1965 to inform conservation policy and management.Location: Global. Methods: We assembled an extensive dataset of first records of detection of ANS (1965–2015) across 49 aquatic ecosystems, including the (a) year of first collection, (b) population status and (c) potential pathway(s) of introduction. Data were analysed at global and regional levels to assess patterns of detection rate, richness and trans-port pathways.Results: An annual mean of 43 (±16 SD) primary detections of ANS occurred—one new detection every 8.4 days for 50 years. The global rate of detections was rel-atively stable during 1965–1995, but increased rapidly after this time, peaking at roughly 66 primary detections per year during 2005–2010 and then declining marginally. Detection rates were variable within and across regions through time. Arthropods, molluscs and fishes were the most frequently reported ANS. Most ANS were likely introduced as stowaways in ships’ ballast water or biofouling, although direct evidence is typically absent.Main conclusions: This synthesis highlights the magnitude of recent ANS detections, yet almost certainly represents an underestimate as many ANS go unreported due to limited search effort and diminishing taxonomic expertise. Temporal rates of detec-tion are also confounded by reporting lags, likely contributing to the lower detection rate observed in recent years. There is a critical need to implement standardized, repeated methods across regions and taxa to improve the quality of global-scale comparisons and sustain core measures over longer time-scales. It will be fundamen-tal to fill in knowledge gaps given that invasion data representing broad regions of the world's oceans are not yet readily available and to maintain knowledge pipelines for adaptive management. Fil: Bailey, Sarah A.. Great Lakes Laboratory For Fisheries And Aquatic Scienc; Canadá Fil: Brown, Lyndsay. Marine Scotland Science; Reino Unido Fil: Campbell, Marnie L.. Deakin University; Australia Fil: Canning-Clode, João. Marine And Environmental Sciences Centre; Portugal Fil: Carlton, James T.. Williams College. Maritime Studies Program; Estados Unidos Fil: Castro, Nuno. Marine And Environmental Sciences Centre; Portugal Fil: Chainho, Paula. Marine And Environmental Sciences Centre; Portugal Fil: Chan, Farrah T.. Great Lakes Institute For Enviromental Research; Canadá Fil: Creed, Joel C.. Universidade do Estado de Rio do Janeiro; Brasil Fil: Curd, Amelia. Ifremer Institut Francais de Recherche Pour L'exploitation de la Mer; Francia Fil: Darling, John. United States Environmental Protection Agency; Estados Unidos Fil: Fofonoff, Paul. Smithsonian Environmental Research Ctr; Estados Unidos Fil: Galil, Bella S.. The Steinhardt Museum Of Natural History; Israel Fil: Hewitt, Chad L.. Murdoch University; Australia Fil: Inglis, Graeme J.. National Institute Of Water & Atmospheric Research Lt; Nueva Zelanda Fil: Keith, Inti. Charles Darwin Foundation; Ecuador Fil: Mandrak, Nicholas E.. University Of Toronto Scarborough; Canadá Fil: Marchini, Agnese. University of Pavia; Italia Fil: McKenzie, Cynthia H.. Fisheries And Ocean Canada. Northwest Atlantic Fisheries Centre; Canadá Fil: Occhipinti‐Ambrogi, Anna. University of Pavia; Italia Fil: Ojaveer, Henn. University of Tartu; Estonia Fil: Pires‐Teixeira, Larissa M.. Universidad de Lisboa; Portugal. Universidade do Estado do Rio de Janeiro; Brasil Fil: Robinson, Tamara B.. Stellenbosch University; Sudáfrica Fil: Ruiz, Gregory M.. United States Environmental Protection Agency; Estados Unidos Fil: Seaward, Kimberley. National Institute of Water & Atmospheric Research Ltd.; Nueva Zelanda Fil: Schwindt, Evangelina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina Fil: Son, Mikhail O.. Institute of Marine Biology; Ucrania Fil: Therriault, Thomas W.. Pacific Biological Station; Canadá Fil: Zhan, Aibin. Chinese Academy of Sciences; República de China

Genetic-environment associations are increasingly revealed through population genomic data and can occur through a number of processes, including secondary contact, divergent natural selection, or isolation by distance. Here, we investigate the influence of the environment, including seasonal temperature and salinity, on the population structure of the invasive European green crab (Carcinus maenas) in eastern North America. Green crab populations in eastern North America are associated with two independent invasions, previously shown to consist of distinct northern and southern ecotypes, with a contact zone in southern Nova Scotia, Canada. Using a RAD-seq panel of 9,137 genomewide SNPs, we detected 41 SNPs (0.49%) whose allele frequencies were highly correlated with environmental data. A principal components analysis of 25 environmental variables differentiated populations into northern, southern, and admixed sites in concordance with the observed genomic spatial structure. Furthermore, a spatial principal components analysis conducted on genomic and geographic data revealed a high degree of global structure (p < .0001) partitioning a northern and southern ecotype. Redundancy and partial redundancy analyses revealed that among the environmental variables tested, winter sea surface temperature had the strongest association with spatial structuring, suggesting that it is an important factor defining range and expansion limits of each ecotype. Understanding environmental thresholds associated with intraspecific diversity will facilitate the ability to manage current and predict future distributions of this aquatic invasive species.

The threat posed by invasive non-native species worldwide requires a global approach to identify which introduced species are likely to pose an elevated risk of impact to native species and ecosystems. To inform policy, stakeholders and management decisions on global threats to aquatic ecosystems, 195 assessors representing 120 risk assessment areas across all six inhabited continents screened 819 non-native species from 15 groups of aquatic organisms (freshwater, brackish, marine plants and animals) using the Aquatic Species Invasiveness Screening Kit. This multi-lingual decision-support tool for the risk screening of aquatic organisms provides assessors with risk scores for a species under current and future climate change conditions that, following a statistically based calibration, permits the accurate classification of species into high-, medium-and low-risk categories under current and predicted climate conditions. The 1730 screenings undertaken encompassed wide geographical areas (regions, political entities, parts thereof, water bodies, river basins, lake drainage basins, and marine regions), which permitted thresholds to be identified for almost all aquatic organismal groups screened as well as for tropical, temperate and continental climate classes, and for tropical and temperate marine ecoregions. In total, 33 species were identified as posing a 'very high risk' of being or becoming invasive, and the scores of several of these species under current climate increased under future climate conditions, primarily due to their wide thermal tolerances. The risk thresholds determined for taxonomic groups and climate zones provide a basis against which area-specific or climate-based calibrated thresholds may be interpreted. In turn, the risk rankings help decision-makers identify which species require an immediate 'rapid' management action (e.g. eradication, control) to avoid or mitigate adverse impacts, which require a full risk assessment, and which are to be restricted or banned with regard to importation and/or sale as ornamental or aquarium/fishery enhancement. (c) 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/)., Cefas Science Excellence fund; [TKP2020-NKA-16], This study is dedicated to our co-author, the late Prof. Olaf Weyl, whose sudden passing during field work in November 2020 was received by us with great sadness. This study represents a contribution to the term of reference 'd' (Advance knowledge base to further develop indicators to evaluate the status and impact of non-indigenous species in marine environments) of the ICES working group on Introductions and Transfers of Marine Organisms. The participation of GHC was supported by the Cefas Science Excellence fund. AW and AF were supported by TKP2020-NKA-16 project.

Genomic studies of invasive species can reveal both invasive pathways and functional differences underpinning patterns of colonization success. The European green crab (Carcinus maenas) was initially introduced to eastern North America nearly 200 years ago where it expanded northwards to eastern Nova Scotia. A subsequent invasion to Nova Scotia from a northern European source allowed further range expansion, providing a unique opportunity to study the invasion genomics of a species with multiple invasions. Here, we use restriction-site-associated DNA sequencing-derived SNPs to explore fine-scale genomewide differentiation between these two invasions. We identified 9137 loci from green crab sampled from 11 locations along eastern North America and compared spatial variation to mitochondrial COI sequence variation used previously to characterize these invasions. Overall spatial divergence among invasions was high (pairwise FST ~0.001 to 0.15) and spread across many loci, with a mean FST ~0.052 and 52% of loci examined characterized by FST values >0.05. The majority of the most divergent loci (i.e., outliers, ~1.2%) displayed latitudinal clines in allele frequency highlighting extensive genomic divergence among the invasions. Discriminant analysis of principal components (both neutral and outlier loci) clearly resolved the two invasions spatially and was highly correlated with mitochondrial divergence. Our results reveal extensive cryptic intraspecific genomic diversity associated with differing patterns of colonization success and demonstrates clear utility for genomic approaches to delineating the distribution and colonization success of aquatic invasive species.

Managers and policymakers in eastern Canada embrace science-based management of nonindigenous species and may benefit from having comprehensive regional species checklists at subnational jurisdictional levels. In this paper, regional checklists provide an account of the richness of ascidians in eastern Canada. Records of 58 ascidians resulted from reviewing 108 published sources, accessing data from two online databases, and collecting some common indigenous ascidian specimens. Analysis comparing the similarity of species among nine regions indicates that there is greater similarity in species composition between contiguous regions than between noncontiguous regions and suggests that there are four zoogeographic clusters in eastern Canada. Our checklists can inform managers and policymakers of the diversity of the ascidian taxa and can minimize taxonomic uncertainties of established nonindigenous and prospective invading species, for example, by identifying indigenous species that are congeners of nonindigenous species. The maintenance of checklists can be a valuable tool for the management of nonindigenous species as baselines to estimate changes in richness and to document the invasion status of nonindigenous species over time. For example, more importance can be placed on the spread of nonindigenous ascidians from one zoogeographic cluster to another than spread within the same cluster.

Marine species invasions pose a global threat to native biodiversity and commercial fisheries. The European green crab (Carcinus maenas) is one of the most successful marine invaders worldwide and has, in the last decade, invaded the southern and western coastal waters of the island of Newfoundland, Newfoundland and Labrador (NL), Canada. Impacts of green crab on the American lobster (Homarus americanus), which are native to Newfoundland, are not well understood, particularly for interactions around deployed fishing gear. Declines in lobster catch rates in invaded systems (i.e., Placentia Bay, NL), have prompted concerns among lobster fishers that green crab are interfering with lobster catch. Here, we conducted a field experiment in a recently-invaded bay (2013) in which we deployed lobster traps pre-stocked with green crab, native rock crab (Cancer irroratus) (a procedural control), or empty (control). We compared catch per unit effort across each category, and used underwater cameras to directly observe trap performance in situ. In addition, we used SCUBA surveys to determine the correlation between ambient density of lobster and green crab in the ecosystem and the catch processes of lobster in traps. We found: (1) Regardless of the species of crab stocked, crab presence reduced the total number of lobster that attempted to enter the trap, and also reduced entry success rate, (2) lobster consumed green crab, rock crab and other lobster inside traps and (3) there was a positive association between lobster catch and ambient lobster density. Our results suggest that while there was a relationship between in-trap crab density and trap catch rates, it was not linked to the non-native/native status of the crab species.

The European green crab (Carcinus maenas) is a crustacean species native to European and North African coastlines that has become one of the world’s most successful marine invasive species. Targeted fishing programs aimed at removing green crabs from invaded ecosystems commonly use Fukui multi-species marine traps. Improving the efficiency of these traps would improve the ability to respond to green crab invasions. In this study, we developed four distinct trap modifications that were designed to facilitate the successful capture of green crabs, with the goal of improving the performance of the Fukui trap. We tested these modificationsin situduring the summer of 2016 at two locations in Placentia Bay, Newfoundland. We discovered that three of our modified Fukui trap designs caught significantly more green crabs than the standard Fukui trap, increasing catch-per-unit-effort (CPUE) by as much as 81%. We conclude that our top-performing modifications have great potential for widespread use with existing Fukui traps that are being used for green crab removal efforts.

Following their first detection in Newfoundland in 2007, populations of invasive European green crabs Carcinus maenas (Linnaeus, 1758) have increased and spread throughout eelgrass Zostera marina meadows. Green crabs can reduce eelgrass biomass by damaging rhizomes and plant shoots when burrowing for shelter and digging for prey. Empirically demon- strating large spatial-scale impacts of green crabs on eelgrass and subsequent cascading effects on the ecosystem has proven difficult because of the general absence of effective baseline studies prior to an invasion of green crabs. We conducted surveys in Placentia and Bonavista bays, New- foundland (20 sites) to compare eelgrass and associated fish communities before and after an invasion of green crabs. We analyzed eelgrass surveys from 1998 and 1999 (before green crab) and again in 2012 (after green crab) using a Before-After-Control-Impact (BACI) study design in order to isolate effects of crab-induced eelgrass loss from effects independent of green crabs. Underwater video sampling evaluated eelgrass change over time and indicated a 50% decline in eelgrass percent cover since 1998 at sites with green crabs, and eelgrass declines up to 100% at sites with highest abundances and longest established presence of green crabs. Beach seining showed a sharp decline in abundance and biomass of fish (~10-fold between sites with and with- out green crabs) and indicated changes in fish community structure after green crab arrival at a site. Our results suggest cascading effects on fish communities and substantial potential impacts in coastal ecosystems occur following green crab invasion.

Seagrass meadows are ecologically important habitats that are declining globally at an accelerating rate due to natural and anthropogenic stressors. Their decline is a serious concern as this habitat provides many ecosystem services. Eelgrass (Zostera marina) is the dominant seagrass species in the western North Atlantic. It has recently been established that invasive tunicate species possibly threaten the health of eelgrass beds. Colonization of eelgrass leaves by tunicates can inhibit eelgrass growth and may cause shoot mortality. To document the distribution and diversity of tunicate species that attach to eelgrass in the western North Atlantic, we surveyed twenty-one eelgrass sites from New Jersey to Newfoundland. Eight species of tunicates were found to be colonizing eelgrass, of which 6 are considered invasive. Botrylloides violaceus and Botryllus schlosseri were most commonly attached to eelgrass, with B. schlosseri having the largest latitudinal range of any species. Tunicate faunas attached to eelgrass were less diverse north of Gloucester, Massachusetts, where individual survey sites exhibited two species at most and only 4 of the 8 species observed in this study. Percent tunicate cover on eelgrass tended to fall within the 1–25 range, with occasional coverage up to >75–100. Density of eelgrass was highly variable among sites, ranging from

The European green crab (Carcinus maenas) is a destructive marine invader that was first discovered in Newfoundland waters in 2007 and has since become established in nearshore ecosystems on the south and west coast of the island. Targeted fishing programs aimed at removing green crabs from invaded Newfoundland ecosystems use Fukui traps, but the capture efficiency of these traps has not been previously assessed. We assessed Fukui traps usingin situobservation with underwater video cameras as they actively fished for green crabs. From these videos, we recorded the number of green crabs that approached the trap, the outcome of each entry attempt (success or failure), and the number of exits from the trap. Across eight videos, we observed 1,226 green crab entry attempts, with only a 16% rate of success from these attempts. Based on these observations we believe there is scope to improve the performance of the Fukui trap through modifications in order to achieve a higher catch per unit effort (CPUE), maximizing trap usage for mitigation. Ultimately, a more efficient Fukui trap will help to control green crab populations in order to preserve the function and integrity of ecosystems invaded by the green crab.

Screening-level risk assessment tools for non-indigenous species are useful to inform management and policy decisions. While a number of tools have been developed to evaluate the risk of introductions in terrestrial and freshwater environments, only one tool is available for marine invertebrates [Marine Invertebrate Invasiveness Scoring Kit (MI-ISK)] and it has not been calibrated or evaluated previously. This paper introduces the Canadian Marine Invasive Screening Tool (CMIST), a tool based on a series of questions related to the sequence of events in the invasion process. We assessed the performance of both CMIST and MI-ISK using 60 species/ecosystem combinations of non-indigenous marine invertebrate species known to have been introduced to three Canadian marine ecoregions. Assessment scores were compared to the results of an expert opinion survey about the level of ecological risk posed by these species in these ecoregions. In addition, a simple way to quantify uncertainty and compute confidence limits surrounding expert evaluations and CMIST scores is presented; the technique could be incorporated into other existing tools. The risk scores returned by the two tools generally were similar, had comparable levels of inter-assessor variability, and correlated well with the results of the expert opinion survey for two of the three ecoregions. In the third ecoregion, we believe the lack of highly problematic species and greater uncertainty (linked to less reliable information) contributed to the weaker correlation. For all ecoregions, CMIST scores were more strongly correlated with expert opinion scores when compared to MI-ISK scores. Finally, we demonstrate how CMIST can be used for new incursions; for each ecoregion we scored 15 additional species not yet introduced and compared these scores with those of species already present. Overall CMIST is a promising screening-level tool; it distinguishes between elements of invasion risk (likelihood and impact), has fewer questions to score than similar tools, and could easily be adapted for other taxa.

Invasive green alga Codium fragile spp. fragile (Suringar) Hariot, 1889 thalli were first detected in Newfoundland (Canada) within Mortier Bay (southwestern Placentia Bay) in August 2012. Subsequent SCUBA surveys in 2013 found Codium attached to subtidal substrates in Arnold’s Cove (northeastern Placentia Bay) and on the northern coast of central Newfoundland near Pilley’s Island (Notre Dame Bay), which is currently the most northern location of Codium in Atlantic Canada. Due to large distances between confirmed sightings, further surveys are recommended to determine the distribution range of Codium and its possible dispersal vectors in Newfoundland coastal waters. Implications of an invasion by Codium on coastal Newfoundland ecosystems are yet to be determined but potential concerns include the replacement of native kelp species, as previously documented elsewhere in Atlantic Canada.

The mussel aquaculture industry has raised concerns following the discovery of green crab Carcinus maenas in Placentia Bay Newfoundland in August 2007. Post-larval green crabs have been found in feral mussel beds in high densities in Europe. If this is true for other green crab populations, mussel seed transfers from Placentia Bay could provide a vector for post-larval juvenile crab transfer to other areas like Notre Dame Bay where provincial mussel aquaculture is concentrated. Green crab is currently not found in this area of Newfoundland. Newly settled green crab juveniles were collected and used in a series of lab scale mitigation trials. Crab and seed mussels were exposed to thermal shocks applicable and feasible for mussel seed management in Placentia Bay. Crab mortality was measured in the treatments and seed mussels were monitored for stress response using the lysosomal destabilization assay. Exposure to heated salt water to 45, 50 and 55°C was effective in culling juvenile green crab while causing minimal stress to mussel seed. The method can be employed in mussel seed management and transfer operations where there are concerns related to potential introductions of hitch-hiking green crab.

Vase tunicate, Ciona intestinalis (Linnaeus, 1767) Type B (sensu Sato et al. 2012), was first recorded in Newfoundland (Canada) in Burin, Placentia Bay, by SCUBA divers conducting rapid visual surveys for invasive species on 19 September 2012. Follow-up surveys of Burin and adjacent communities were conducted in October and November 2012. Ciona intestinalis was present in relatively low abundance in Burin, but a well-established population was located in Little Bay, approximately 15 km north of Burin. Little Bay is located within Mortier Bay, an area of high vessel traffic and the possible introduction source of C. intestinalis. Further surveys are recommended to delineate the present distribution and monitor future dispersal of C. intestinalis in coastal Newfoundland waters. Due to the demonstrated high ecological and economic impacts of this species in other previously invaded regions, options for mitigating population growth and dispersal should be examined to minimize effects of this non-indigenous species.

Invasive green crab populations initially established in Canada within the Bay of Fundy, New Brunswick in the 1950s and were present in all five Atlantic provinces by 2007. Genetic evidence suggests that the Atlantic Canadian populations originated from two separate introductions with differences in time of establishment among regions and possible population-level behavioural differences. In this study, we examine intraspecific foraging behaviour among crabs from different populations, and interspecific foraging behaviour between genetically similar crabs and juvenile lobsters. Both sets of foraging experiments involved competition for a limited food source over a 1-h period. In intraspecific match-ups, recent invaders from Newfoundland (NL) were significantly superior foragers than long-established invaders from Nova Scotia (NS) and New Brunswick (NB) populations; however, we found no differences between NL and Prince Edward Island (PE) invaders. Crabs from PE were better competitors than those from NS and NB, but these differences were not significant. Interspecific competition experiments indicated that the feeding behaviour of recent invaders (NL) and genetically similar, but long-established invaders (NS), differed in the presence of juvenile lobsters. Our study documents striking behavioural differences among populations of green crab from a small geographic region, which may reflect a combination of both genetic differences and time since establishment. These differences may result in varying impacts on newly invaded habitats.

Aim To determine timing, source and vector for the recent introduction of the European green crab, Carcinus maenas (Linnaeus, 1758), to Newfoundland using multiple lines of evidence. Location Founding populations in Placentia Bay, Newfoundland, Canada and potential source populations in the north-west Atlantic (NWA) and Europe. Methods We analysed mitochondrial and microsatellite genetic data from European and NWA populations sampled during 1999‐2002 to determine probable source locations and vectors for the Placentia Bay introduction discovered in 2007. We also analysed Placentia Bay demographic data and shipping records to look for congruent patterns with genetic analyses. Results Demographic data and surveys suggested that C. maenas populations are established and were in Placentia Bay for several years (c. 2002) prior to discovery. Genetic data corroboratively suggested central/western Scotian Shelf populations (e.g., Halifax) as the likely source area for the anthropogenic introduction. These Scotian Shelf populations were within an admixture zone made up of genotypes from both the earlier (early 1800s) and later (late 1900s) introductions of the crab to the NWA from Europe. Placentia Bay also exhibited this mixed ancestry. Probable introduction vectors included vessel traffic and shipping, especially vessels carrying ballast water. Main conclusions Carcinus maenas overcame considerable natural barriers (i.e., coastal and ocean currents) via anthropogenic transport to become established and abundant in Newfoundland. Our study thus demonstrates how non-native populations can be important secondary sources of introduction especially when aided by human transport. Inference of source populations was possible owing to the existence of an admixture zone in central/western Nova Scotia made up of southern and northern genotypes corresponding with the crab’s two historical

Invasive, non-indigenous ascidians have been a significant biofouling problem for the aquaculture industry in Nova Scotia and Prince Edward Island since the mid-1990's. The problematic species in Atlantic Canada include Styela clava, Ciona intestinalis, Botryllus schlosseri and Botrylloides violaceus. Newfoundland harbour surveys that we have performed over the past three years revealed the presence of B. schlosseri and B. violaceus. As of yet, neither of these species has reached invasive abundance in Newfoundland. Portions of the COI genes of two non-indigenous ascidians (Botryllus schlosseri and Botrylloides violaceus) and two indigenous ascidians (Boltenia echinata and Halocynthia pyriformis) were cloned and sequenced. We then determined intraspecific and interspecific COI sequence variation. The BLASTN results showed that Botryllus schlosseri and Halocynthia pyriformis match the other listings for these species in GenBank. However, the BLAST results from Botrylloides violaceus were more similar to B. schlosseri than B. violaceus. While there were no other entries for Boltenia echinata, it was similar to other species in the Pyuridae family. Intraspecific similarity in the COI sequence for Newfoundland populations was >99.7% for B. violaceus, H. pyriformis and B. echinata, and 86.5-96.6% for B. schlosseri. Interspecific similarities among all four species were

To test the hypothesis that low temperature inhibits utilization of sinking spring bloom material, we studied the formation and fate of the bloom in Conception Bay, Newfoundland, Canada, where the entire water column is

Fluctuations in mussel (Mytilus edulis) growth have been attributed to large-scale fluctuations in temperature, salinity and the abundance of phytoplankton. This study examined the effect of fatty acids on the growth (wet weight) of cultured mussels during 2000 and 2001 in Notre Dame Bay, Newfoundland. Mussels were socked in June 2000 and harvested in October 2001. On a monthly basis, the mussels grew at variable rates (mean 10.73 ± 6.86, range 5.9–18.8 mg d− 1 in 2000 and 10.09 ± 8.91, range 5.1–22.9 mg d− 1 in 2001) with the highest growth rate in September of each year. The growth, however, did not demonstrate localized differences. The proportion of polar lipid (PrL) as a percent of total lipid was much higher in mussel samples (mean 71.1 ± 4.8%) than the phytoplankton (mean 44.3 ± 21.2%), and the opposite was observed for the neutral lipid (NL: mean 30.2 ± 4.4% in mussels and 45.3 ± 11.7% phytoplankton). The fatty acid profiles of phytoplankton and mussels were, in general the same, except that the pentaenoic fatty acid, 18:5ω3, was not detected in mussels, and no C22 non-methylene interrupted dienes (NMIDs) were detected in phytoplankton. However, proportions of 22:2NMIDs (as percent of total identified fatty acids) in mussels were relatively high (range 2.5–3.5%) particularly in 2000. The 22:6ω3, 20:5ω3, 16:0, 14:0, 16:1ω7 and to some extent 16:4ω3 were the most abundant fatty acids in the phytoplankton and mussel samples. Of these fatty acids, 20:5ω3 was the only fatty acid in both phytoplankton and mussels that showed a significant positive correlation with growth, while correlations with other fatty acids varied in magnitude or direction (positive or negative) depending on the source of the acid being either phytoplankton or mussel. An interesting observation within the essential fatty acids was that neither 22:6ω3 nor 20:4ω6 was significantly correlated with growth, but when their levels were combined with 20:5ω3 to give the total essential fatty acid in phytoplankton or mussels, the result was a significant positive correlation with growth for both phytoplankton and mussel essential fatty acids. Moreover, the coefficients of correlation for the other physiologically important acids in bivalves, namely the 20:2NMIDs were by far the most significant ones, but only with the mussel NMID, and their correlation with growth was negative. Approximately 140 variables from mussels and phytoplankton were tested in order to construct a model to predict the growth of mussels. Of these variables, four were found to be significant (r2 = 0.725): 20:2NMID1, 18:2ω4 and 22:5ω6 in mussels and 16:1ω9 in phytoplankton.

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Fatty acid biomarkers were used to investigate the biogeochemistry of a former blue mussel (Mytilus edulis) aquaculture site in a shallow, sheltered cove in northeastern Newfoundland. High levels of polyunsaturated fatty acids (PUFA) in net-tow and sediment trap samples indicated a substantial phytoplankton source of organic matter, and fluctuations in specific fatty acid biomarkers reflected the changing abundances of diatoms and dinoflagellates. In comparison, sediments contained very low levels of PUFA (

Water samples from six bays were taken over a 5-year period (1988 to 1992) to determine the distribution and abundance of loricate choanoflagellates in coastal Newfoundland, and to assess the impact that these organisms might have on this cold ocean food web. Scanning electron microscopy was used to study the morphology of these flagellates, allowing us to identify 11 species of loricate choanoflagellates. Parvicorbicula socialis (Meunier) Deflandre was the most abundant species (80 × 103 cells l−1), particularly during the spring diatom bloom. Single-cell species, such as Bicosta spini fera (Throndsen) Leadbeater and Calliacantha natans (Grontved) Leadbeater, were found more commonly after the spring diatom bloom in the summer months. Many of the single-cell choanoflagellates were attached to bacteria-rich microaggregates and debris in the water column and in unpoisoned sediment traps. The P. socialis cell flux was calculated to be 5.3 × 106 cells m−2 d−1 in late May sediment traps. P. socialis in the upper 100 m of the water column was removing 0.3% of the standing crop of bacteria each day (April/May), and the equivalent of 7.4% of the daily bacterial production over the water column. Diel studies of P. socialis in Conception Bay suggest that the sharp decline in population numbers observed in midnight samples may be related to the high number of grazing zooplankton observed during the same period. Pelagic tunicate and zooplankton fecal pellets were found to contain large numbers of choanoflagellate costae, thus providing a direct link from the microbial loop to the macrozooplankton.

The concentration and nutritional awlity of suspended particulate matter at an experimental scallop aquaculture site on the east -1 of Newfoundland, Canada, was determined at 3 depths over an 8 mo sampling period. Lipid classes and fatty acids were measured chromatographically and the seston components were identified and quantified by microscopy. These measurements were correlated and then related to the growth of juvenille scallops Placopecten magellanicus introduced to the site. The low seston concentrations obsewad throughout the year were punctuated by 4 large inputs: the spring diatom bloom, a resuspension ment. a summer microzooplankton and nanoflagellate bloom, and a fall increase in zooplankton faecal :pellet and heterotrophic dinoflagellate concentrations. The largest inputs of lipids were associated with the resuspension event and the summer bloom. The resuspended particles included the benthic permate diatom Cyrosigrna spp. which contained large lipid globules. High concentrations of polvunwrmated triacylglycerols occurred at this time; more saturated triacylglycerols were prominent in the sunmer The acyl lipids contained unusually high proportions of the long-chain polyunsaturated fatty acid 20:406 which was correlated (p < 0.05) with the proportion of mlcrozooplankton in the seston. The C16 fatty acid ratio 16:1~7/16:0, used previously as a diatom biomarker, was strongly correlated (p < O.01) with the proportion of centric diatoms. Scallop growth appeared to be related less to the major-ts of total lipids to the water column and more to the proportion of the essential fatty acid 22:6 in the acyl lipids. This fatty acid was associated principally with cryptophytes (p < 0.02).

Fecal pellets produced by the copepod Calanus finmarchicus and the tunicate Oikopleura vanhoeffeni in coast Newfoundland waters were examined throughout the year using scanning electron microscopy and found to contain numerous species of nanoplankton (i. e. cells 2−20 μm in diameter). Annually nanoplankters composed 20-70% of the identifiable species in both the copepod and tunicate feces, except during the spring diatom bloom. The diatoms, choanoflagellates, euglenoids, chrysophytes, coccolithophorids and cyanobacteria identified, illustrate that nanoplankters are ingested by macrozooplankters and thus may contribute more significantly to the particulate flux than previously thought

Inorganic membrane filters (Anopore) were examined qualitatively by epifluorescence and scanning electron microscopy to determine their suitability for the study of nanoplankton and picoplankton. Compared with filters currently used, the Anopore filters allowed for increased resolution of the specimen with epifluorescence microscopy because of filter flatness and increased illumination caused by the large number of pores cm -2 . The inorganic filters had a lower filtration rate than polycarbonate filters. For scanning electron microscopy, the metal oxide (Anopore) filters were efficient support for the plankton, with little charging of cells or background.