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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.

Global trends in the occurrence, toxicity and risk posed by harmful algal blooms to natural systems, human health and coastal economies are poorly constrained, but are widely thought to be increasing due to climate change and nutrient pollution. Here, we conduct a statistical analysis on a global dataset extracted from the Harmful Algae Event Database and Ocean Biodiversity Information System for the period 1985-2018 to investigate temporal trends in the frequency and distribution of marine harmful algal blooms. We find no uniform global trend in the number of harmful algal events and their distribution over time, once data were adjusted for regional variations in monitoring effort. Varying and contrasting regional trends were driven by differences in bloom species, type and emergent impacts. Our findings suggest that intensified monitoring efforts associated with increased aquaculture production are responsible for the perceived increase in harmful algae events and that there is no empirical support for broad statements regarding increasing global trends. Instead, trends need to be considered regionally and at the species level. The global occurrence of harmful algal bloom events is not increasing uniformly over time and the increase in recorded events is due to enhanced coastal monitoring and aquaculture, according to an analysis of a 33-year global dataset.

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.

Two genetically distinct lineages of European green crabs (Carcinus maenas) were independently introduced to eastern North America, the first in the early 19th century and the second in the late 20th century. These lineages first came into secondary contact in southeastern Nova Scotia, Canada (NS), where they hybridized, producing latitudinal genetic clines. Previous studies have documented a persistent southward shift in the clines of different marker types, consistent with existing dispersal and recruitment pathways. We evaluated current clinal structure by quantifying the distribution of lineages and fine‐scale hybridization patterns across the eastern North American range (25 locations, ~39 to 49°N) using informative single nucleotide polymorphisms (SNPs; n = 96). In addition, temporal changes in the genetic clines were evaluated using mitochondrial DNA and microsatellite loci (n = 9–11) over a 15‐year period (2000–2015). Clinal structure was consistent with prior work demonstrating the existence of both northern and southern lineages with a hybrid zone occurring between southern New Brunswick (NB) and southern NS. Extensive later generation hybrids were detected in this region and in southeastern Newfoundland. Temporal genetic analysis confirmed the southward progression of clines over time; however, the rate of this progression was slower than predicted by forecasting models, and current clines for all marker types deviated significantly from these predictions. Our results suggest that neutral and selective processes contribute to cline dynamics, and ultimately, highlight how selection, hybridization, and dispersal can collectively influence invasion success.

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.

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.

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.

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.

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 ...

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

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.

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 (

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

Previous literature documents Atlantic Silverside, Menidia menidia, as occurring from the southern Gulf of St. Lawrence to northeastern Florida. Beach seining in St. George’s Bay, Newfoundland, revealed the presence of this species in coastal waters of southwestern Newfoundland. This is the first documented report of M. menidia in Newfoundland waters. This report extends the range of this species north of the Laurentian Channel, a significant biogeographic barrier to small coastal fishes. All M. menidia collected were young-of-the-year, less than 90 mm SL (Standard Length). These fish may be representative of a larger relict population originating from the Mid-Hypsithermal Interval (7000 years ago) that spawn in St. George’s Bay and migrate offshore for winter. Alternatively, these M. menidia may be survivors of a more southern spawning population carried northward by ocean currents.