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Bibliography of the Maurice Lamontagne Institute

Réal GAGNON

POULIN, M., N. LUNDHOLM, L. BÉRARD-THERRIAULT, M. STARR, R. GAGNON, 2010. Morphological and phylogenetic comparisons of Neodenticula seminae (bacillariophyta) populations between the subarctic Pacific and the Gulf of St. Lawrence. Eur. J. Phycol., 45(2): 127-142 .

Neodenticula seminae is a very important member of modern diatom assemblages in the Bering Sea and at middle to high latitudes of the North Pacific. In the North Atlantic, this species was considered extinct until it was recorded in high abundance in the 2001 spring phytoplankton bloom of the Gulf of St. Lawrence, Eastern Canada. Here, we discuss some of the most distinctive features of its morphology, including variation in some characters between the subarctic Pacific and the Gulf of St. Lawrence specimens. Most importantly, we observed that the deck and basal ridges, and the solid-walled costae (formerly known as primary pseudosepta) characteristic of N. seminae were present in the subarctic Pacific material, but were absent or vestigial in the Gulf of St. Lawrence material and in cultures from both regions. This morphological variation was most likely due to differences in physico–chemical water properties between the subarctic Pacific and the Gulf of St. Lawrence. Phylogenetic analyses of the internal transcribed spacer regions of the nuclear ribosomal DNA showed that the strains of N. Seminae collected in the Gulf of St. Lawrence and the subarctic Pacific clustered in two sister clades, but differed from each other only slightly more than the variation among the subarctic Pacific strains. These results confirmed the reappearance of N. Seminae in the NW Atlantic after an absence of ˜0.8 Ma. In addition, the phylogenetic analyses based on the large subunit of the nuclear ribosomal DNA positioned N. seminae firmly within the Bacillariaceae (i.e. diatoms with a fibulate raphe system) and proved a close relationship to species of Fragilariopsis.©2010 British Phycological Society

FAUCHOT, J., M. LEVASSEUR, S. ROY, R. GAGNON, A.M. WEISE, 2005. Environmental factors controlling Alexandrium tamarense (dinophyceae) growth rate during a red tide event in the St. Lawrence Estuary (Canada). J. Phycol., 41(2): 263-272 .

The dinoflagellate Alexandrium tamarense (Lebour) Balech 1985 is responsible for recurrent outbreaks of paralytic shellfish poisoning in the St. Lawrence Estuary. In July 1998, an A. tamarense red tide developed in the estuary with maximum cell concentrations reaching 2.3 × 106 cells·L-1 in brackish surface waters. To estimate the growth rate of these cells, surface water samples from different locations and days during the bloom were incubated for 5 to 9 days under in situ temperature and light conditions. Growth rates varied both spatially and temporally between 0 and 0.55 day-1, reaching the maximum growth rate reported for this species in culture. High growth rates were measured even during the peak of the red tide, suggesting that the extremely high cell concentrations observed did not solely result from aggregation or physical concentration but also involved active cellular growth. Alexandrium tamarense cells were found over a large range of salinity (20.8-29.5 psu), but high densities and significant growth were only measured when salinity was lower than 24.5 psu. Under these conditions, the number of divisions achieved by A. tamarense was proportional to the amount of nitrate available at the beginning of the incubations, whereas variations in growth rate were apparently controlled by the availability of phosphate. We hypothesize that the ability of A. tamarense to perform vertical migrations and acquire nitrate at night pushes this species toward phosphate limitation in the St. Lawrence Estuary.©2005 Phycological Society of America

GAGNON, R., M. LEVASSEUR, A.M. WEISE, J. FAUCHOT, P.G.C. CAMPBELL, B.J. WEISSENBOECK, A. MERZOUK, M. GOSSELIN, B. VIGNEAULT, 2005. Growth stimulation of Alexandrium tamarense (dinophyceae) by humic substances from the Manicouagan River (eastern Canada). J. Phycol., 41(3): 489-497 .

In the St. Lawrence Estuary, annual recurrent blooms of the toxic dinoflagellate Alexandrium tamarense L. Balech are associated with brackish waters. Riverine inputs are suspected to favor bloom development by increasing water column stability and/or by providing growth stimulants such as humic substances (HS). A 17-day culture experiment was conducted to evaluate the importance of HS as growth factors for A. tamarense. Nonaxenic cultures were exposed to four HS extracts from three different sources: humic and fulvic acids isolated from the Manicouagan River, Quebec, Canada; humic acids from the Suwannee River, Georgia, United States; and a desalted alkaline soil extract. For each extract, four concentrations were tested as supplements to the artificial Keller medium, a nitrate-rich algal culture medium. Additions of HS from all sources significantly enhanced the overall growth rates relative to the controls. Concentrations of HS, estimated by UV spectrophotometry, remained constant throughout the exponential growth phase, suggesting that the HS were acting mainly as growth promoters during our experiment. Dose-response curves indicated that HS could increase the growth rate of A. tamarense even at low concentrations, such as those encountered in the St. Lawrence Estuary. Our results support the hypothesis that HS from the Manicouagan River plume can stimulate the development of toxic dinoflagellate blooms.©2005 Phycological Society of America

COUTURE, J.Y., M. LEVASSEUR, E. BONNEAU, C. DESJARDINS, G. SAUVÉ, S.S. BATES, C. LÉGER, R. GAGNON, S. MICHAUD, 2001. Spatial and temporal variation of domoic acid in molluscs and of Pseudo-nitzschia spp. blooms in the St. Lawrence from 1998 to 2000. Can. Tech. Rep. Fish. Aquat. Sci., 2375, 24 p .

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The presence of domoic acid (the toxin responsilbe for Amnesic Shellfish Poisoning - ASP) in shellfish has been monitored in the estuary and the northern Gulf of St. Lawrence since 1997 by the Canadian Food Inspection Agency (CFIA). The results indicate a spatial and temporal evolution of domoic acid contamination between 1998 and 2000. Trace amounts of this toxin were first detected in the gonads of sea scallops from fishing areas offshore of the Iles-de-la-Madeleine in the summer of 1998. In 1999, the concentration of domoic acid in the digestive glands of sea scallops from the same area reached 585 ug g -1, whereas the adductor muscles were not contaminated. At the same time, concentrations of domoic acid close to 25 ug g -1 digestive gland were measured in sea scallops from the Havre-aux-Maisons lagoon while trace amounts were measured for the first time in soft-shell clams collected on the Lower North Shore of the Gulf of St. Lawrence. In 2000, the digestive glands of sea scallops from the Iles-de-la-Madeleine remained toxic and trace amounts of domoic acid were measured in shellfish all along the North Shore, from Tadoussac to Havre-Saint-Pierre. In addition to the CFIA data, the Harmful Algae Monitoring Program of the Maurice Lamontagne Institute (Fisheries and Oceans Canada) revealed the presence of two potentially domoic-acid-producing diatoms in the St. Lawrence: Pseudo-nitzschia seriata and Pseudo-nitzschi delicatissima. Analysis of data showed a link between domoic acid in some shellfish from the Iles-de-la-Madeleine and North Shore and the presence of Pseudo-nitzschia seriata. Dense blooms of P. delicatissima (with no P. seriata) did not cause toxicity. Laboratory analyses performed on a P. seriata strain isolated from the St. Lawrence estuary during a toxic event showed the ability of P. seriata to produce domoic acid whereas all attempts made with P. delicatissima from other regions of eastern Canada have so far been negative. These new results show that P. seriata blooms in the St. Lawrence and the resulting shellfish toxicity due to domoic acid represent a potential risk that needs to be considered in the future.

COUTURE, J.Y., M. LEVASSEUR, E. BONNEAU, C. DESJARDINS, G. SAUVÉ, S.S. BATES, C. LÉGER, R. GAGNON, S. MICHAUD, 2001. Variations spatiales et temporelles des concentrations d'acide domoïque dans les mollusques et des abondances de Pseudo-nitzschia spp. dans le Saint-Laurent de 1998 à 2000. Rapp. tech. can. sci. halieut. aquat., 2375, 25 p .

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The presence of domoic acid (the toxin responsilbe for Amnesic Shellfish Poisoning - ASP) in shellfish has been monitored in the estuary and the northern Gulf of St. Lawrence since 1997 by the Canadian Food Inspection Agency (CFIA). The results indicate a spatial and temporal evolution of domoic acid contamination between 1998 and 2000. Trace amounts of this toxin were first detected in the gonads of sea scallops from fishing areas offshore of the Iles-de-la-Madeleine in the summer of 1998. In 1999, the concentration of domoic acid in the digestive glands of sea scallops from the same area reached 585 ug g -1, whereas the adductor muscles were not contaminated. At the same time, concentrations of domoic acid close to 25 ug g -1 digestive gland were measured in sea scallops from the Havre-aux-Maisons lagoon while trace amounts were measured for the first time in soft-shell clams collected on the Lower North Shore of the Gulf of St. Lawrence. In 2000, the digestive glands of sea scallops from the Iles-de-la-Madeleine remained toxic and trace amounts of domoic acid were measured in shellfish all along the North Shore, from Tadoussac to Havre-Saint-Pierre. In addition to the CFIA data, the Harmful Algae Monitoring Program of the Maurice Lamontagne Institute (Fisheries and Oceans Canada) revealed the presence of two potentially domoic-acid-producing diatoms in the St. Lawrence: Pseudo-nitzschia seriata and Pseudo-nitzschi delicatissima. Analysis of data showed a link between domoic acid in some shellfish from the Iles-de-la-Madeleine and North Shore and the presence of Pseudo-nitzschia seriata. Dense blooms of P. delicatissima (with no P. seriata) did not cause toxicity. Laboratory analyses performed on a P. seriata strain isolated from the St. Lawrence estuary during a toxic event showed the ability of P. seriata to produce domoic acid whereas all attempts made with P. delicatissima from other regions of eastern Canada have so far been negative. These new results show that P. seriata blooms in the St. Lawrence and the resulting shellfish toxicity due to domoic acid represent a potential risk that needs to be considered in the future.

ST-AMAND, L., R. GAGNON, T.T. PACKARD, C. SAVENKOFF, 1999. Effects of inorganic mercury on the respiration and the swimming activity of shrimp larvae, Pandalus borealis. Comp. Biochem. Physiol., C: Pharmacol. Toxicol. Endocrinol., 122(1): 33-43 .

GAGNON, R., E.A. LEHOUX, H.E. GUDERLEY, 1998. Manually operated freeze-clamping press. Anal. Biochem., 260(2): 251-252 .

DEMERS, S., S. ROY, R. GAGNON, C. VIGNAULT, 1991. Rapid light-induced changes in cell fluorescence and in xanthophyll-cycle pigments of Alexandrium excavatum (Dinophyceae) and Thalassiosira pseudonana (Bacillariophyceae) : a photo-protection mechanism. Mar. Ecol. Prog. Ser., 76: 185-193 .