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Spatial and temporal trends of marine harmful algal events in Canada over the last three decades were examined using data from the Harmful Algal Event Database (HAEDAT). This database contains the most complete record of algal blooms, phycotoxins and shellfish harvesting area closures in Canada since 1987. This 30-year review of 593 Canadian HAEDAT records from 1988 to 2017, together with other Canadian data and publications, shows that recurring harmful algal events have been widespread throughout both the Atlantic and Pacific coastal regions. The 367 paralytic shellfish toxin (PST) reports revealed annual and frequent recurrence throughout both the Atlantic and Pacific regions, including multi-year PST events in the Bay of Fundy, the Estuary and Gulf of St. Lawrence and the Strait of Georgia. The 70 amnesic shellfish toxin (AST) records revealed no recognizable trend, as these events were usually area specific and did not recur annually. The increasing frequency of diarrhetic shellfish toxin (DST) events over the period of this review, in total 59 records, can be at least partially explained by increased sampling effort. Marine species mortalities caused by harmful algae (including diatoms, dictyochophytes, dinoflagellates, and raphidophytes), were a common occurrence in the Pacific region (87 reports), but have been reported much less frequently in the Atlantic region (10 reports). Notable Canadian records contained in HAEDAT include the first detection worldwide of amnesic shellfish poisoning (ASP), attributed to the production of domoic acid (an AST) by a diatom (Pseudo-nitzschia multiseries) in Prince Edward Island in 1987. The first proven case of diarrhetic shellfish poisoning (DSP) in Canada and North America was recorded in 1990, and the first closures of shellfish harvesting due to DST (associated with the presence of Dinophysis norvegica) occurred in Nova Scotia in 1992, followed by closures in Newfoundland and Labrador in 1993. In 2008, mass mortalities of fishes, birds and mammals in the St. Lawrence Estuary were caused by Alexandrium catenella and high levels of PST. During 2015, the Pacific coast experienced a large algal bloom that extended from California to Alaska. It resulted in the closure of several shellfish harvesting areas in British Columbia due to AST, produced by Pseudo-nitzschia australis. Data from the Canadian Arctic coast is not included in HAEDAT. However, because of the emerging importance of climate change and increased vessel traffic in the Arctic, information on the occurrence of harmful algal species (pelagic and sympagic = sea ice-associated) in that region was compiled from relevant literature and data. The results suggest that these taxa may be more widespread than previously thought in the Canadian Arctic. Information in HAEDAT was not always robust or complete enough to provide conclusions about temporal trends. Compilation of spatial and temporal information from HAEDAT and other records is nevertheless important for evaluating the potential role of harmful algae as a stressor on Canadian marine ecosystems, and will support the next step: developing a knowledge gap analysis that will establish research priorities for determining their consequences on human and ecosystem health.

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.

Ships and boats may transport whole communities of non-indigenous species (NIS) through hull biofouling, some members of which may become invasive. Several studies have evaluated the diversity of these communities, but very few have analyzed the survival of organisms after their voyages into different and potentially inhospitable conditions. This factor is important to consider because the last port of call approach for risk assessments assumes that if the conditions observed in the last port of call are different from those observed in a receiving port, risks are diminished or null. Using an innovative experimental system, we tested the survival and recovery of the marine blue mussel (Mytilus edulis) and the freshwater zebra mussel (Dreissena polymorpha) by exposing them to adverse salinity conditions at varying temperatures to simulate ships and boats transiting to ports or marinas with contrasting environmental conditions. Both mussel species, which are well-known for their adaptability to new environments as aquatic NIS, survived better at colder temperatures, with blue mussels surviving up to 14 days in freshwater, and zebra mussels up to 8 days in marine water. This highlights the importance of considering the resistance of fouling organisms to adverse conditions in vector and species risk assessments.

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.

Non-indigenous species (NIS) are recognized as a global threat to biodiversity and monitoring their presence and impacts is considered a prerequisite for marine environmental management and sustainable develop- ment. However, monitoring for NIS seldom takes place except for a few baseline surveys. With the goal of serving the requirements of the EU Marine Strategy Framework Directive and the EU Regulation on the prevention and management of the introduction and spread of invasive alien species, the paper highlights the importance of early detection of NIS in dispersal hubs for a rapid management response, and of long-term monitoring for tracking the effects of NIS within recipient ecosystems, including coastal systems especially vulnerable to introductions. The conceptual framework also demonstrates the need for port monitoring, which should serve the above mentioned requirements but also provide the required information for implementation of the International Convention for the Control and Management of Ships Ballast Water and Sediments. Large scale monitoring of native, cryptogenic and NIS in natural and man-made habitats will collectively lead to meeting international requirements. Cost-efficient rapid assessments of target species may provide timely information for managers and policy-advisers focusing on particular NIS at particular localities, but this cannot replace long-term monitoring. To support legislative requirements, collected data should be verified and stored in a publicly accessible and routinely updated database/information system. Public involvement should be encouraged as part of monitoring programs where feasible. & 2015 Published by Elsevier Ltd.

Populations of green crab (Carcinus maenas) have expanded within Newfoundland, and this has raised concern from fish harvesters and scientists regarding bivalve predation in coastal areas on species such as juvenile sea scallops (Placopecten magellanicus). We used 2 microcosm experiments to determine (1) the effects of water temperature (5°C and 12°C) on scallop predation; (2) scallop size selection in small and large green crabs and a large indigenous predator, the rock crab (Cancer irroratus); and (3) bivalve prey selection in large green crabs between softshell clams (Mya arenaria), blue mussels (Mytilus edulis), and sea scallops. Overall, green and rock crabs captured 4 times more scallops in warm water (12°C) than cold (5°C). Large green (60–70 mm) and rock (75–90 mm) crabs captured similar numbers of scallops, selected medium-size (30–40 mm) scallops, and avoided small (10–20 mm) scallops. Small green crabs (40–50 mm) captured only small scallops. Large green crabs selected softshell clams ...

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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The main objective of recent international legislative measures and policies concerning marine ecosystems is to ensure sustainable environmental management to maintain a good status for marine waters, habitats and resources, with the ultimate target of achieving an integrated ecosystem-based approach to management. Because bioinvasions pose significant threats to marine ecosystems and the goods and services these provide, non-indigenous species (NIS) are included in the more recent legislative documents. A major challenge for the scientific community is to translate the principles of the legislative directives into a realistic, integrated ecosystem- based approach and at the same time provide stakeholders with best practices for managing NIS. The aim of this paper, prepared by members of the Working Group on Introductions and Transfers of Marine Organisms (WGITMO) of the International Council for the Exploration of the Sea (ICES), is to provide guidance for the application of NIS related management in the European Union Marine Strategy Framework Directive (MSFD). Ten recommendations, including NIS identification, standardization of sampling and data, indicators, propagule pressure and management issues are considered in this paper. While most of these suggestions were developed to improve the implementation of the MSFD, several may be more widely applicable.

Temporal variability in the quantity, organic content, and phytoplankton composition of the particulate food supply available to a cultured mussel population was assessed for a 3-year period in a small inlet of Notre Dame Bay, Newfoundland, Canada. The study site had a restricted flushing rate estimated at 1–2·75 times wk−1for a complete water exchange. The quantity of both total (TPM) and organic (POM) seston varied temporally from 0·7–23·7 mg l−1and 0·05–1·97 mg l−1respectively during the 3-year sampling period. TPM typically remained relatively high (>10 mg l−1) through the winter and spring period. Most of the seasonal variation in total seston was due to seasonal variability in the PIM component. Both PIM and POM concentrations were seasonally lowest during summer. The organic fraction of the seston (POM/TPM ratio) was seasonally low in winter and increased steadily through spring and summer to reach its maximum in the autumn. The living phytoplankton component of the seston was typically dominated, both numerically and in biomass, by a variety of diatom and autotrophic nanoflagellate species in the 2– 20-μm diameter size range. Discrete diatom population blooms occurred in the autumn of all three years and largely consisted of a single species, Skeletonema costatum. Phytoplankton:detritus ratios were significantly lower during winter. Total phytoplankton biomass levels were seasonally low during winter and summer and were associated with seasonal variation in diatom biomass. We conducted modelling simulations of relationships among seston organic food levels, their temporal variability, tidal flushing rates, cultured mussel biomass and production indices, and estimates of mussel maintenance ration requirements to predict the adequacy of northern inlets to sustain commercial-scale mussel farm development. We conclude from these simulations that small, semi-enclosed, northern inlets likely frequently experience periods when naturally occurring organic seston levels are insufficient to meet basic mussel stock maintenance ration requirements when such inlets are stocked to commercial-scale densities. We infer that periods of food-limited mussel growth and/or production are likely to occur at these high mussel population levels, particularly during summer. Qualitatively poor (low POM:TPM ratio; low phytoplankton:detritus ratio) food supply during winter may also be a further limiting factor. The implications of our conclusions in relation to aquaculture industry development and environmental management are discussed.

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.

During routine feeding experiments in the field we discovered that adult Placopecten magellanicus were releasing large numbers of particles from the mantle cavity. These particles ranged in size from 6 to 15 μm with a prominent peak at ≈10 μm making it possible to recognize them using an electronic particle counter/sizer. Tissue samples were collected from individuals that were known to have released particles and from scallops that apparently had not. Light and scanning electron microscopy (SEM) were used to identify these particles as ciliated and non-ciliated epithelial cells. The number of scallops exfoliating cells was related to increasing water temperatures and the maximum stage of gamete development. SEM photomicrographs showed that at least some areas of the gill were devoid of cilia including those that comprise the lateral, laterofrontal and frontal tracts of the filaments. Exfoliation of these ciliated cells has obvious implications for the animal's ability to capture and transport food particles.

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