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Bibliography of the Maurice Lamontagne Institute

Sonia MICHAUD

LIZOTTE, M., M. LEVASSEUR, S. MICHAUD, M.G. SCARRATT, A. MERZOUK, M. GOSSELIN, J. POMMIER, R.B. RIVKIN, R.P. KIENE, 2012. Macroscale patterns of the biological cycling of dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) in the Northwest Atlantic. Biogeochemistry, XX(X): XX-XX Article in press .

LUCE, M., M. LEVASSEUR, M.G. SCARRATT, S. MICHAUD, S.-J. ROYER, R. KIENE, C. LOVEJOY, M. GOSSELIN, M. POULIN, Y. GRATTON, M. LIZOTTE, 2011. Distribution and microbial metabolism of dimethylsulfoniopropionate and dimethylsulfide during the 2007 Arctic ice minimum. J. Geophys. Res. (C Oceans), 116(11). Art. no C00G06, 8 p .

The distribution and biological cycling of the climate active trace gas dimethylsulfide (DMS) and its algal precursor dimethylsulfoniopropionate (DMSP) were characterized at 20 stations across the Canadian High Arctic during fall 2007. Transformation rates of DMSP and production rates of DMS from dissolved DMSP (DMSPd) were measured during 3 h onboard incubations with radioactively labeled 35S-DMSP. Particulate DMSP (DMSPp) in surface waters varied between 2 and 39 nmol L-1 and increased with chlorophyll a (Chl a) concentrations (r = 0.84). DMS concentrations in surface waters ranged from 0.05 to 0.8 nmol L-1 and were positively correlated with DMSPp (r = 0.89) and Chl a (r = 0.74). The DMSPd loss rate constant varied from 0.01 to 0.14 h-1 and was also positively correlated with Chl a concentrations (r = 0.67). The turnover time of the DMSPd pool varied between 0.3 and 3.4 days (mean = 0.96 day). Bacterial DMS production varied between 0.01 and 0.51 nmol L-1 d-1 (mean = 0.14 nmol L-1 d-1). Assuming local steady state conditions at the time scale of a day, the turnover time of the DMS pool based only on production from DMSPd was ˜6 days at the sampling stations. This long turnover time suggests that DMS production was dominated by nonbacterial processes during our study. Our results show that DMS production could persist at low rates in late fall under ice-free conditions. The magnitude of this production appears to be limited by the low algal and bacterial production prevailing at that time.© 2011 American Geophysical Union

REMPILLO, O., A.M. SEGUIN, A.-L. NORMAN, M. SCARRATT, S. MICHAUD, R. CHANG, S. SJOSTEDT, J. ABBATT, B. ELSE, T. PAPAKYRIAKOU, S. SHARMA, S. GRASBY, M. LEVASSEUR, 2011. Dimethyl sulfide air-sea fluxes and biogenic sulfur as a source of new aerosols in the Arctic fall. J. Geophys. Res. (D Atmospheres), 116(24): art. no. D00S04 .

Dimethyl sulfide (DMS) and its oxidation products, which have been proposed to provide a climate feedback mechanism by affecting aerosol and cloud radiative properties, were measured on board the Canadian Coast Guard ship Amundsen in sampling campaigns in the Arctic in the fall of 2007 and 2008. DMS flux was calculated based on the surface water measurements and yielded 0.1–2.6 μmol m-2 d-1 along the Northwest Passage in 2007 and 0.2–1.3 μmol m-2 d-1 along Baffin Bay in 2008. DMS oxidation products, sulfur dioxide (SO2), methane sulfonic acid (MSA), and sulfate in aerosols were also measured. The amounts of biogenic SO2 and sulfate were approximated using stable isotope apportionment techniques. Calculating the threshold amount of SO2 needed for significant new particle formation from the formulation by Pirjola et al. (1999), the study suggests that instances of elevated biogenic SO2 concentrations (between 8 and 9 September 2008) derived using conservative assumptions may have been sufficient to form new aerosols in clean air conditions in the Arctic region.© 2011 American Geophysical Union

CHANG, R.Y.-W., S.J. SJOSTEDT, J.R. PIERCE, T.N. PAPAKYRIAKOU, M.G. SCARRATT, S. MICHAUD, M. LEVASSEUR, W.R. LEAITCH, J.P.D. ABBATT, 2011. Relating atmospheric and oceanic DMS levels to particle nucleation events in the Canadian Arctic. J. Geophys. Res. (D Atmospheres), 116(21): art. no. D00S03 .

Measurements of ocean surface and atmospheric dimethyl sulfide (DMS) and particle size distributions were made in the Canadian Arctic Archipelago during the fall of 2007 and the late summer of 2008 aboard the Canadian Coast Guard Ship Amundsen. Nucleation-mode particles were observed during the 2008 cruise, which took place in the eastern Arctic from August to September when the atmosphere and ocean were more photo-active as compared to the October 2007 transit in the Beaufort Sea during which no nucleation/growth events were observed. The observed nucleation periods in 2008 coincided with high atmospheric and ocean surface DMS concentrations, suggesting that the particles originated from marine biogenic sources. An aerosol microphysics box model was used to simulate nucleation given the measured conditions in the marine boundary layer. Although other sources may have contributed, we find that the newly formed particles can be accounted for by a marine biogenic DMS source for combinations of the following parameters: [OH] ≥ 3 × 105 molecules cm-3, DMS mixing ratio is ≥ 100 pptv, the activation coefficient is ≥ 10-7 and the background particle concentration is ≥ 100 cm-3.©2011American Geophysical Union

BOURDAGE, H., P. GOUDREAU, 2010. Évaluation des stocks de pétoncles des eaux côtières du Québec en 2009 : données de la pêche commerciale ; Stock assessment on scallops of the inshore waters of Quebec in 2009: commercial fishery data. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2010/068, viii + 69 p .

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This document presents the commercial fishery index used for the Quebec inshore waters scallops stocks assessment following the 2007-2009 fishing seasons. This review process was held on January 26, 2010 at the Maurice Lamontagne Institute in Mont-Joli. During this meeting, the assembly reviewed the status of the scallop stocks commercially exploited in the Quebec Region. This ocument presents methodologies and data used during the review of the fishery statistics and commercial catches sampling

ROYER, S.-J., M. LEVASSEUR, M. LIZOTTE, M. ARYCHUK, M.G. SCARRATT, C.S. WONG, C. LOVEJOY, M. ROBERT, K. JOHNSON, A. PENA, S. MICHAUD, R.P. KIENED, 2010. Microbial dimethylsulfoniopropionate (DMSP) dynamics along a natural iron gradient in the northeast subarctic Pacific. Limnol. Oceanogr., 55(4): 1614-1626 .

We characterized the effect of an inshore–offshore gradient in Fe in the northeast subarctic Pacific on the bacterioplankton and phytoplankton assemblages and on the microbial cycling of particulate and dissolved dimethylsulfoniopropionate (DMSPp and DMSPd) and dimethylsulfide (DMS). Averaged concentrations of total dissolved Fe (TDFe) decreased linearly with increasing water density along the transect, from 3.4 nmol L-1 at the two inshore stations to 1.0 nmol L-1 at the offshore stations, as a result of the vertical and lateral mixing between the Fe-rich coastal water and the Fe-poor Alaska Current. The Fe-rich inshore stations were dominated by diatoms and characterized by low DMSPp : chlorophyll a (Chl a) ratios (ca. 26 nmol μg-1) and bacterial DMS yield (< 4 %). In contrast, the Fe-poor offshore stations were dominated by prymnesiophytes and exhibited high DMSPp : Chl a ratios (ca. 84 nmol μg-1) and bacterial DMS yield (8 %). Chl a, DMSPp, and the abundance of total bacteria and three bacterial clades (Gammaproteobacteria, Roseobacter, and Betaproteobacteria) were positively correlated with the TDFe gradient. At the Fe-poor offshore stations, the positive correlation found between TDFe and the DMSPp : Chl a ratios suggests that Fe supplied by mixing stimulated DMSP production in the prymnesiophyte-dominated assemblage, a response similar to that generally observed during the first days of most of the large-scale ocean iron fertilizations (OIFs). These results suggest that the stimulation of DMSP production takes place whatever the Fe supply mode: atmospheric dust deposition, as simulated by OIFs, or mixing, as reported in this study.©2010 American Society of Limnology and Oceanography, Inc.

YANG, G.-P., M. LEVASSEUR, S. MICHAUD, A. MERZOUK, M. LIZOTTE, M. SCARRATT, 2009. Distribution of dimethylsulfide and dimethylsulfoniopropionate and its relation with phytoneuston in the surface microlayer of the western North Atlantic during summer. Biogeochemistry, 94(3): 243-254 .

One of the key steps towards predicting dimethylsulfide (DMS) emission to the atmosphere is to understand the distribution and cycling of biogenic sulfur in the microlayer. In this study, we examined the distribution of DMS and dissolved and particulate fractions of dimethylsulfoniopropionate (DMSPd and DMSPp) in the surface microlayer and bulk water of the western North Atlantic during July 2003. DMS concentrations in the bulk water varied from 0.71 to 7.65 nM. In contrast, DMS concentrations in the surface microlayer were fairly low (0.17–1.33 nM). Average concentrations of DMSPd and DMSPp in the bulk water were 2.09 (1.87–6.25) and 44.1 (8.06–119.8) nM, respectively, and those in the surface microlayer were 15.4 (4.06–54.3) and 29.9 (7.32–97.0) nM. In general, DMS was depleted in the microlayer (mean concentration: 0.60 nM) relative to the bulk water (mean concentration: 2.38 nM) with enrichment factors (the ratio of the microlayer concentration to bulk water concentration) ranging from 0.13 to 0.54. There was no consistent enrichment of DMSPp and chlorophyll a in the microlayer. On the contrary, DMSPd appeared to be highly enriched in the microlayer with an average EF of 4.89. The concentration of phaeopigments was also generally greater in the microlayer than in the bulk water, presumably due to enhanced photo-oxidation of chlorophyll a under high surface light intensities in the microlayer. In the study area, the concentration of DMSPp was significantly correlated with the abundance of dinoflagellates in the microlayer. Moreover, a significant correlation between the distributions of DMS, DMSPp, chlorophyll a and phaeopigment concentrations in the microlayer and the bulk water demonstrated that the biogenic materials in the microlayer come primarily from the bulk water below.©2009 Springer Science+Business Media B.V.

MERZOUK, A., M. LEVASSEUR, M. SCARRATT, S. MICHAUD, M. LIZOTTE, R.B. RIVKIN, R.P. KIENE, 2008. Bacterial DMSP metabolism during the senescence of the spring diatom bloom in the Northwest Atlantic. Mar. Ecol. Prog. Ser., 369: 1-11 .

The impact of the decline of the vernal bloom on the bacterial metabolism of dimethylsulfoniopropionate (DMSP), the precursor of dimethylsulfide (DMS), was investigated during a 7 d Lagrangian study conducted in the Northwest Atlantic in spring 2003. Daily variations in bacterial leucine incorporation, dissolved DMSP (DMSPd) uptake and DMS production rates were measured in the surface mixed layer (SML) and in the deep chlorophyll a maximum (DCM) that formed as the bloom collapsed. Seawater samples were amended with 35S-DMSPd, and the products of bacterial DMSPd degradation were measured during 3 h on-board incubations. The gradual decrease in phytoplankton biomass and diatom abundance measured in the SML was accompanied by a sharp doubling of the bacterial abundance and a peak in leucine incorporation rate on Day 2, suggesting that bacteria responded to a transient pulse in dissolved organic matter. Bacterial DMSPd uptake and DMS production were highest on Days 1 and 2 (1.2 and 0.10 nmol l-1 h-1, respectively), but rapidly decreased by Day 3, suggesting that DMSPd was becoming a less important substrate for the growing bacterial assemblage as other substrates became available. Bacterial DMSPd uptake and DMS production rates were also low in the DCM despite very high DMS yields (40 to 50 %), showing that neither the decline of the diatom spring bloom in the SML nor the accumulation of cells in the DCM resulted in a stimulation of bacterial DMSP metabolism or accumulation of DMS. The present study provides new field evidence for the potential uncoupling between bacterial production and DMS dynamics likely due to variations in the availability of other S-containing organic compounds released during the decay of phytoplankton blooms.©2008 Inter-Research

LIZOTTE, M., M. LEVASSEUR, M.G. SCARRATT, S. MICHAUD, A. MERZOUK, M. GOSSELIN, J. POMMIER, 2008. Fate of dimethylsulfoniopropionate (DMSP) during the decline of the northwest Atlantic Ocean spring diatom bloom. Aquat. Microb. Ecol., 52(2): 159-173 .

A 7 d Lagrangian process study of the biogeochemical cycling of dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) was conducted within a decaying diatom bloom in the northwest Atlantic Ocean in spring 2003. Ambient profiles of DMSP and DMS were surveyed daily in the water column and were used to estimate in situ net transformation rates. Phytoplankton and bacterioplankton abundance were determined within the surface mixed layer (SML) as well as at the deep chlorophyll maximum (DCM), and sinking fluxes of particulate DMSP (DMSPp) below 75 to 100 m were assessed using free-drifting particle interceptor traps. Chlorophyll a (chl a) concentration and diatom abundance declined in the SML over the course of the study period, and the phytoplankton chl a biomass progressively settled above the nitracline forming the DCM. The decline of the diatom bloom coincided with the settling of DMSPp out of the SML and the formation of a DMSP-rich layer at the DCM. The low daily sinking loss rate of DMSPp at 75 m (<2 % d-1) provided confirmation of the efficient retention of DMSPp at the DCM. The decaying bloom gave rise to an initial release of dissolved DMSP (DMSPd) in the upper water column, which was rapidly consumed by the growing bacterial community. The rapid loss of DMSPd was accompanied by significant increases in net production of DMS in the SML and fluxes of DMS to the atmosphere. Despite this increase in DMS dynamics, overall in situ net production rates remained fairly low during the 7 d period (≤0.4 nmol DMS l-1 d-1), suggesting that demethylation by the developing bacterial community dominated DMSPd-consuming processes.©2008 Inter-Research

SCARRATT, M.G., M. LEVASSEUR, S. MICHAUD, S. ROY, 2007. DMSP and DMS in the Northwest Atlantic: late-summer distributions, production rates and sea-air fluxes. Aquat. Sci., 69(3): 292-304 .

DMSP and DMS were measured along a set of transects in the Northwest Atlantic during September, 1999. Six 24 h Lagrangian stations were occupied between 36° and 61° N latitude, covering subtropical to polar water types. Profiles of total DMSP (DMSPt), DMS, chl a, and oceanographic variables were determined at each station. Phytoplankton abundance and species assemblage were determined in surface waters and at the depth of the Chl a maximum in all profiles. Between profile stations, DMSPt and DMS samples were collected by a pump while the vessel was moving. Chl a and DMSPt were most abundant in the northern regions, with very low levels in subtropical waters. There was no direct correlation between DMSP t and Chl a. Maximum DMSPt concentrations reached 203 nM in coastal waters and 112 nM in the open ocean. A strong correlation was observed between DMSPt and the abundance of dinoflagellates (Spearman r=0.91; p <0.0001; n=13) and prymnesiophytes (Spearman r=0.91; p<0.0001; n=13). Cryptophytes also showed a weak but significant correlation (Spearman r=0.58; p=0.039; n=13). The waters around Greenland were the only site dominated by diatoms and their abundance was not correlated with DMSPt concentrations. DMS concentrations were low and fairly uniform, with maximum levels of 4.7 nM in coastal waters and 2.2 nM in the open ocean. DMS fluxes from surface waters were calculated based on observed sea-surface concentrations and wind speeds and showed a strong peak associated with a storm event, although no depletion of DMS resulting from the storm was observed. In situ incubation experiments showed DMSP consumption and DMS production rates to be relatively high, notwithstanding the generally low phytoplankton biomass.©2007 Eawag, Dübendorf

MICHAUD, S., M. LEVASSEUR, G. CANTIN, 2007. Seasonal variations in dimethylsulfoniopropionate and dimethylsulfide concentrations in relation to the plankton community in the St. Lawrence Estuary. Estuar. Coast. Shelf Sci., 71: 741-750 .

Weekly variations in total dimethylsulfoniopropionate (DMSPt) and dimethylsulfide (DMS) were investigated in relation to the phytoplankton assemblage from spring to fall 1994 at a coastal fixed station in the St. Lawrence Estuary. DMSPt and DMS concentrations showed a strong seasonality and were tightly coupled in time. Maximum concentrations of DMSPt and DMS were observed in July and August, during a period of warm water and low nutrient concentrations. Seasonal maxima of 365.4 nmol l-1 for DMSPt and 14.2 nmol l-1 for DMS in early August coincided with the presence of many phytoplankton species, such as Alexandrium tamarense, Dinophysis acuminata, Gymnodinium sp., Heterocapsa rotundata, Protoperidinium ovatum, Scrippsiella trochoidea, Chrysochromulin sp. (6 μm), Cryptomonas sp. (6 μm), a group of microflagellates smaller than 5 μ (mf < 5), many tintinnids, and Mesodinium rubrum. The abundance of mf &<lt; 5 followed the general trend of DMS concentrations. The temporal occurrence of high P. ovatum abundance and DMSPt concentrations suggests that this heterotrophic dinoflagellate can either synthesize DMSP or acquire it from DMSP-rich prey. The calculated sea-to-air DMS flux reached a maximum of 8.36 μmol 2 d1 on August 1. The estimated annual emission from the St. Lawrence Estuary is 77.2 tons of biogenic sulfur to the atmosphere.© 2007 Elsevier Ltd.

LEVASSEUR, M., M.G. SCARRATT, S. MICHAUD, A. MERZOUK, C.S. WONG, M. ARYCHUK, W. RICHARDSON, R.B. RIVKIN, M. HALE, E. WONG, A. MARCHETTI, H. KIYOSAWA, 2006. DMSP and DMS dynamics during a mesoscale iron fertilization experiment in the Northeast Pacific-Part I: temporal and vertical distributions. Deep-Sea Res., Part II, Top. Stud. Oceanogr., 53: 2353-2369 .

This paper reports on the influence of the Fe fertilization conducted during the subarctic ecosystem response to iron enrichment study (SERIES) on the distribution of the biogenic sulfur compounds dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) in the context of changes in plankton composition. The Fe enrichment resulted in a rapid increase in the abundance of a nanoplankton assemblage dominated by Prymnesiophyceae, Prasinophyceae, small diatoms (<5 μm), heterotrophic dinoflagellates, and zooflagellates. This first assemblage persisted for 8 days before collapsing abruptly due to an increase in microzooplankton herbivory. The abundance of large diatoms started to increase shortly after the initial Fe fertilization but peaked 1-2 days after the crash of the nanoplankton bloom. Inside the Fe patch, particulate DMSP (DMSPp) increased from 100 to 285 nmol L-1 during the nanoplankton bloom, decreased rapidly back to initial level as this bloom collapsed, and remained low during the bloom of large diatoms. Outside the patch, phytoplankton and protists abundance and DMSPp concentrations remained low and relatively stable throughout the experiment. DMS concentrations were elevated at the onset of the experiment outside the patch (maximum of 15.7 nmol L-1 on day 1), increased up to 26.5 nmol L-1 10 days after the enrichment, and decreased to ca. 6 nmol L-1 by the end of the experiment. This large natural pulse in DMS coincided with conditions of high irradiance and decreasing wind speed. Inside the Fe patch, DMS concentrations exhibited the same general pattern, but with distinctive features related to the Fe fertilization. First, DMS concentrations tended to increase more rapidly inside the patch during the initial nanoplankton bloom, leading to DMS concentrations ca. 2 times higher inside the patch than outside on day 6. Second, DMS concentrations became consistently lower inside the patch (often below our limit of quantification of 0.03 nmol L-1) than outside (ca. 6 nmol L-1) during the peak of the diatom bloom. Our results thus confirm the rapid increase in nanoplankton and DMSPp reported during all previous Fe-fertilization experiments. On the other hand, the decrease in DMS concentrations measured inside the Fe patch during SERIES is unique and shows that adding Fe to HNLC waters may not always lead to conditions that could mitigate climate warming.©2006 Elsevier Ltd.

SCARRATT, M.G., A. MARCHETTI, M.S. HALE, R.B. RIVKIN, S. MICHAUD, P. MATTHEWS, M. LEVASSEUR, N. SHERRY, A. MERZOUK, W.K.W. LI, H. KIYOSAWA, 2006. Assessing microbial responses to iron enrichment in the Subarctic Northeast Pacific: Do microcosms reproduce the in situ condition?. Deep-Sea Res., Part II, Top. Stud. Oceanogr., 53: 2182-2200 .

A microcosm experiment was conducted in the NE Pacific in July 2002 to compare the microbial response between microcosms and the Subarctic Ecosystem Response to Iron-Enrichment Study (SERIES) in situ iron-enrichment experiment. Seawater microcosms (20 L) were incubated aboard ship under natural light using three treatments: (1) low-iron seawater amended with 4 nmol l-1 FeSO4 (+Fe); (2) low-iron seawater amended with 4 nmol l-1 FeSO4 and 86 nmol l-1 GeO2 (+Fe+Ge); (3) seawater collected from the in situ Fe-enriched patch (PW). The +Fe+Ge treatment used germanium to control diatom growth to assess the role of diatoms in dimethylsulfoniopropionate (DMSP) production. The following variables were measured in the microcosms and in situ: chlorophyll a (chl a), nitrate (NO‾3), silicic acid (Si(OH)4), phytoplankton abundance and species identification, bacterial abundance (including estimates of low- and high-DNA bacteria), bacterial production, bacterial specific growth rate, particulate and dissolved DMSP and dimethylsulfide (DMS) concentrations. There was little or no significant difference (ANCOVA) in the response of most variables between the +Fe and PW microcosms, but large differences were observed between both these treatments and the in situ data from the enriched patch. Chl a in all microcosms increased from ambient levels (approx. 0.5-1 μg l-1) to approx. 4.5-6.2 μg l-1 after 11 d incubation, when NO‾3 was fully depleted from all microcosms. During this same period, in situ chl a increased more slowly to a maximum of 2.9 μg l-1 on day 11. Nanophytoplankton and picophytoplankton were more abundant in the microcosms relative to the in situ community, which became dominated by large diatoms. Bacterial abundance was similar in the microcosms and in situ, but bacterial production was significantly higher in the microcosms. While neither DMSPd nor DMS accumulation showed significant differences between the microcosms and in situ, particulate DMSP concentrations increased significantly faster in the +Fe and PW treatments. These differences represent bottle effects resulting from the containment of the microcosms, which suppresses grazing, alters community and food web structure, enhances iron and nutrient regeneration, and isolates the community from physical transport and export processes including sinking. Thus during this experiment, the microcosms were not a good model for the in situ system in terms of the effects of iron on the phytoplankton biomass, nutrient uptake, bacterial dynamics and DMSPp production. In the germanium-amended treatment, the inhibition of diatom growth resulted in enhanced growth of other taxa and a suppression of bacterial production, leading to increased production of DMSP and DMS and strong correlations between DMSP, DMS and non-diatom phytoplankton taxa. Diatoms did not contribute significantly to particulate DMSP concentrations. Crown Copyright © 2006 Published by Elsevier Ltd.

BOUILLON, R.-C., W.L. MILLER, M. LEVASSEUR, M. SCARRATT, A. MERZOUK, S. MICHAUD, L. ZIOLKOWSKI, 2006. The effect of mesoscale iron enrichment on the marine photochemistry of dimethylsulfide in the NE subarctic Pacific. Deep-Sea Res., Part II, Top. Stud. Oceanogr., 53: 2384-2397 .

Measurements of underwater light fields and available quantum yield spectra were used to calculate photochemical removal rates of DMS for surface waters of the northeast subarctic Pacific during the SERIES mesoscale iron-fertilization experiment in July 2002. We observed that the UV portion of the solar spectrum was most important in inducing DMS photo-oxidation, and calculated that UV-B accounted for more than 20 % and UV-A for more than 68 % of the total DMS photo-oxidation near the sea surface. Vertically resolved rates showed that most (>90 %) of the DMS photo-oxidation occurs in the upper 15m of the water column. During the study, calculated rates of DMS photo-oxidation, just below the ocean’s surface ranged from 0.34 to 5.9 μmol m-3d-1. As the study progressed, an initial increase in photo-oxidation rates occurred within the iron-enriched patch and this was followed by a dramatic decrease in rates, whereas little change was observed outside the patch. Changes in DMS concentrations and decreases in the photochemical removal efficiency for DMS were the dominant factors explaining the variation in the DMS photo-oxidation rates. The turnover rate constants for DMS photo-oxidation, calculated for the upper mixed layer (UML) of the water column, (0.03-0.25 d-1) were in the range of those previously published and were at times higher than those calculated for biological consumption of DMS during SERIES. Our results suggest that iron fertilization of an oceanic patch in the northeast Pacific Ocean considerably altered the photochemical removal rates and turnover rate constants of DMS.©2006 Elsevier Ltd.

MERZOUK, A., M. LEVASSEUR, M.G. SCARRATT, S. MICHAUD, R.B. RIVKIN, M.S. HALE, R.P. KIENE, N.M. PRICE, W.K.W. LI, 2006. DMSP and DMS dynamics during a mesoscale iron fertilization experiment in the Northeast Pacific-Part II: biological cycling. Deep-Sea Res., Part II, Top. Stud. Oceanogr., 53: 2370-2383 .

Dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) biological cycling rates were determined during SERIES, a mesoscale iron-fertilization experiment conducted in the high-nutrient low-chlorophyll (HNLC) waters of the northeast subarctic Pacific. The iron fertilization resulted in the rapid development of a nanoplankton assemblage that persisted for 11 days before abruptly crashing. The nanoplankton bloom was followed by a diatom bloom, accompanied by an important increase in bacterial abundance and production. These iron-induced alterations of the plankton assemblage coincided with changes in the size and biological cycling of the DMSP and DMS pools. The initial nanoplankton bloom resulted in increases in particulate DMSP (DMSPp; 77-180 nmol L-1), dissolved DMSP (DMSPd; 1-24 nmol L-1), and biological gross (0.11-0.78 nmol L-1 h-1) and net (0.04-0.74 nmol L-1 h-1) DMS production rates. During the nanoplankton bloom, DMSPd consumption by bacteria exceeded their sulfur demand and the excess sulfur was probably released as DMS, consistent with the high gross DMS production rates observed during that period. The crash of the nanoplankton bloom was marked by the rapid decline of DMSPp, DMSPd, and gross DMS production to their initial values. Following the crash of the nanoplankton bloom, bacterial production and estimated sulfur demand reached transient maxima of 9.3 μCL-1d-1 and 14.2 nmol S L-1d-1, respectively. During this period of high bacterial production, bacterial DMSPd consumption was also very high (6 nmol L-1h-1), but none of the consumed DMSPd was converted into DMS and a net biological DMS consumption was measured. This transient period initiated a rapid decrease in DMS concentrations inside the iron-enriched patch, which persisted during the following diatom bloom due to low biological gross and net DMS production that prevented the replenishment of DMS. Our results show that the impact of Fe fertilization on DMS production in HNLC waters result from a complex interplay between the dynamics of the algal blooms and their influence on bacterial DMSP and DMS metabolism. ©2006 Elsevier Ltd.

LE CLAINCHE, Y., M. LEVASSEUR, A. VÉZINA, R.-C. BOUILLON, A. MERZOUK, S. MICHAUD, M. SCARRATT, C.S. WONG, R.B. RIVKIN, P.W. BOYD, P.J. HARRISON, W.L. MILLER, C.S. LAW, F.J. SAUCIER, 2006. Modeling analysis of the effect of iron enrichment on dimethyl sulfide dynamics in the NE Pacific (SERIES experiment). J. Geophys. Res. (C Oceans), 111, art. no C01011, 15 p .

The large-scale iron enrichment conducted in the NE Pacific during the Subarctic Ecosystem Response to Iron Enrichment Study (SERIES) triggered a phytoplankton bloom dominated successively by nanophytoplankton and large diatoms. During the first 14 days, surface dimethyl sulfide (DMS) levels increased both inside (up to 22 nmol L-1) and outside (up to 19 nmol L-1) the patch, with no consistent Fe effect. Later, DMS concentrations became sixfold lower inside the patch than outside. In this study, we used a DMS budget module embedded in a one-dimensional ocean turbulence model to investigate the contribution of the interacting physical, photochemical, and biological processes to this particular DMS response. Temporal variations in biological net DMS production were reconstructed using an inverse modeling approach. Our results show that short-term (days) variations in both the physical processes (i.e., turbulent mixing and ventilation) and the biological cycling of DMS are needed to explain the time evolution of DMS concentrations both outside and inside the Fe-enriched patch. The biological net DMS production was generally high (up to 0.35 nmol L-1 h-1) and comparable outside and inside the patch during the first 10 days, corresponding to the observed accumulation of DMS inside and outside the patch. Later, it became negative (net DMS biological consumption) inside the patch, suggesting a change in dimethylsulfoniopropionate bacterial metabolism. This study stresses the importance of short-term variations in biological processes and their sensitivity to the physical environment in shaping the DMS response to iron enrichment.©2006 American Geophysical Union

YANG, G.-P., M. LEVASSEUR, S. MICHAUD, M. SCARRATT, 2005. Biogeochemistry of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) in the surface microlayer and subsurface water of the western North Atlantic during spring. Mar. Chem., 96(3-4): 315-329 .

Sixteen surface microlayer samples and corresponding subsurface water samples were collected in the western North Atlantic during April-May 2003 to study the distribution and cycling of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) and the factors influencing them. In the surface microlayer, high concentrations of DMS appeared mostly in the samples containing high levels of chlorophyll a, and a significant correlation was found between DMS and chlorophyll a concentrations. In addition, microlayer DMS concentrations were correlated with microlayer DMSPd (dissolved) concentrations. DMSPd was found to be enriched in the microlayer with an average enrichment factor (EF) of 5.19. However, no microlayer enrichment of DMS was found for most samples collected. Interestingly, the DMS production rates in the microlayer were much higher than those in the subsurface water. Enhanced DMS production in the microlayer was likely due to the higher concentrations of DMSPd in the microlayer. A consistent pattern was observed in this study in which the concentrations of DMS, DMSPd, DMSPp (particulate) and chlorophyll a in the microlayer were closely related to their corresponding subsurface water concentrations, suggesting that these constituents in the microlayer were directly dependent on the transport from the bulk liquid below. Enhanced DMS production in the microlayer further reinforces the conclusion that the surface microlayer has greater biological activity relative to the underlying water.©2005 Elsevier B.V.

MERZOUK, A., M. LEVASSEUR, M. SCARRATT, S. MICHAUD, M. GOSSELIN, 2004. Influence of dinoflagellate diurnal vertical migrations on dimethylsulfoniopropionate and dimethylsulfide distribution and dynamics (St. Lawrence Estuary, Canada). Can. J. Fish. Aquat. Sci., 61: 712-720 .

The influence of the diurnal vertical migration of the dinoflagellates Alexandrium tamarense and Scrippsiella trochoidea on dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) dynamics was studied during a 34-h Lagrangian experiment in the St. Lawrence Estuary in July 2000. Particulate DMSP (DMSPp), dissolved DMSP (DMSPd), and DMS exhibited diel patterns with minimum concentrations during the night and maximum concentrations around noon. DMSPp concentrations were correlated with the abundance of the two vertically migrating DMSP-rich dinoflagellates. The DMSPp:Chl a ratio exhibited similar diel variations, suggesting a light-induced de novo DMSP synthesis during the day. Diel variations of the DMS:Chl a ratio suggest that the accumulation of DMS around noon resulted from physiological responses of the algae and (or) bacteria to light. Biological gross DMS production and bacterial DMS consumption were decoupled, leading to rapid fluctuations in DMS. These results show that in systems dominated by DMSP-rich dinoflagellates containing DMSP lyases, DMS concentrations may vary by as much as a factor of 10 over a 24-h period. Such diel variations must be considered when estimating the contribution of such systems to the DMS sea to air flux.©2004 NRC Canada

LEVASSEUR, M., M. SCARRATT, S. ROY, D. LAROCHE, S. MICHAUD, G. CANTIN, M. GOSSELIN, A. VÉZINA, 2004. Vertically resolved cycling of dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) in the Northwest Atlantic in spring. Can. J. Fish. Aquat. Sci., 61: 744-757 .

In May 1998, profiles of ambient concentration and net changes of particulate dimethylsulfoniopropionate (DMSPp), dissolved dimethylsulfoniopropionate (DMSPd), and dimethylsulfide (DMS) were measured in three bio geographic provinces of the Northwest Atlantic: Northwest Atlantic Continental Shelf (Grand Banks), North Atlantic Drift, and North Atlantic Subtropical Gyre (Sargasso Sea). All stations/depths exhibited large losses of DMSPp (up to 18.0 nmol·L-1·day-1). DMSP and DMS cycling varied in relation to the type and development stage of the plankton assemblages. The postdiatom bloom conditions on the Grand Banks were associated with an efficient utilization of DMSP by microzooplankton and bacteria. Bacterial DMS production balanced the DMS bacterial consumption, resulting in little net DMS production (0.3 nmol·L-1·day-1). This contrasted with the North Atlantic Drift and Sargasso Sea stations where flagellates were thriving and most of the DMSPp loss was recovered in the dissolved pool, indicating a less active microbial DMSP metabolism. DMSPd cleavage was high in these latter cases and exceeded DMS bacterial consumption, allowing a net production of DMS (up to 1.8 nmol·L-1·day-1). These results indicate that maximum DMS net production occurs in growing algal systems where the production of DMSPd resulting from microzooplankton grazing exceeds the bacterial requirement in carbon and sulfur.©2004 NRC Canada

LEVASSEUR, M., J.-Y. COUTURE, A.M. WEISE, S. MICHAUD, M. ELBRACHTER, G. SAUVÉ, E. BONNEAU, 2003. Pelagic and epiphytic summer distributions of prorocentrum lima and P. mexicanum at two mussel farms in the Gulf of St.Lawrence, Canada. Aquat. Microbiol. Ecol., 30: 283-293 .

MICHAUD, S., M. LEVASSEUR, G. DOUCETTE, G. CANTIN, 2002. Particle size fractionation of paralytic shellfish toxins (PSTs): seasonal distribution and bacterial production in the St. Lawrence estuary, Canada. Toxicon, 40: 1451-1462 .

WEISE, A.M., M. LEVASSEUR, F.J. SAUCIER, S. SENNEVILLE, E. BONNEAU, S. ROY, G. SAUVÉ, S. MICHAUD, J. FAUCHOT, 2002. The link between precipitation, river runoff, and blooms of the toxic dinoflagellate Alexandrium tamarense in the St. Lawrence. Can. J. Fish. Aquat. Sci., 59: 464-473 .

Blooms of the toxic dinoflagellate Alexandrium tamarense, which is responsible for paralytic shellfish poisoning, are annually recurrent events in the Estuary and Gulf of St. Lawrence, Quebec, Canada. The analysis of abundance data for this algal species between 1989 and 1998 at Sept-Iles, a presumed initiation site in the north-western Gulf of St. Lawrence, revealed yearly fluctuations in the onset, duration, and magnitude of toxic A. tamarense blooms. Hydrological and meteorological data for the region indicate that rainfall, Moisie River runoff, and wind are highly related to the pattern of bloom development each year. Results from the 10-year data set reveal that in this system: 1) high Moisie River runoff from a prolonged spring freshet or from heavy rainfall events in the summer and fall can initiate A. tamarense blooms; 2) high Moisie River runoff combined with prolonged periods of weak winds (<  4 m times s-1) favour the continued development of blooms; and 3) winds > 8 m times s-1 disrupt blooms. Salinity, which reflects the general state of the water column in terms of freshwater input and stability, had a strong negative correlation with the probability of observing A. tamarense cells at this station and could thus be used as a predictive tool for the presence of cells in this system.

SCARRATT, M.G., M. LEVASSEUR, S. MICHAUD, G. CANTIN, M. GOSSELIN, S.J. DE MORA, 2002. Influence of phytoplankton taxonomic profile on the distribution of dimethylsulfide and dimethylsulfoniopropionate in the northwest Atlantic. Mar. Ecol. Prog. Ser., 244: 49-61 .

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.

LEVASSEUR, M., J.-Y. COUTURE, G. SAUVÉ, S. MICHAUD, 2001. Contamination des mollusques du Québec par les phycotoxines diarrhéiques (DSP) et amnestiques (ASP) et recherche des sources potentielles de phycotoxines DSP. Rapp. tech. can. sci. halieut. aquat., 2350, 41 p .

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This study was initiated following the detection for the first time of DSP and ASP phycotoxins in shellfish (blue mussel and scallop) from the Magdalen Islands during the summer of 1998. Our objectives were 1) to determine if Prorocentrum lima may be the source of DSP in cultured mussels from the Magdalen Islands and 2) to evaluate the extent of the contamination by DSP and ASP of molluscs from different areas in Quebec. Our sampling, carried out at two cultured mussel sites in the Magdalen Islands, revealed the regular presence of P. lima fixed on the epibionts growing on the mussel socks. P. lima was frequently found in the digestive glands of the mussels, but apparently in concentrations too low to cause contamination during our study. In other regions of Quebec, 9.5 % of the 252 shellfish analysed (mostly mussels) showed low levels of DTX with a maximum of 0.4 mug/g in the digestive gland. During the sampling conducted in the Magdalen Islands, we also identified, for the first time in Eastern Canada, another toxic microalga: Prorocentrum mexicanum, P. mexicanum is known to produce DSP-type toxins, but different from those produced by P. lima. These toxins were not measured during our study but could represent a risk that needs to be evaluated. Finally, elevated concentrations of ASP (up to 550 mug/g) were measured in the digestive glands of scallops from the Magdalen Islands. The source of these toxins and the importance of the contamination remain to be determined.

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.

SCARRATT, M., G. CANTIN, M. LEVASSEUR, S. MICHAUD, 2000. Particle size-fractionated kinetics of DMS production : where does DMSP cleavage occur at the microscale?. J. Sea Res., 43(3-4): 245-252 .

SCARRATT, M.G., M. LEVASSEUR, S. SCHULTES, S. MICHAUD, G. CANTIN, A. VÉZINA, M. GOSSELIN, S.J. DE MORA, 2000. Production and consumption of dimethylsulfide (DMS) in North Atlantic waters. Mar. Ecol. Prog. Ser., 204: 13-26 .

SCHULTES, S., M. LEVASSEUR, S. MICHAUD, G. CANTIN, G. WOLFE, M. GOSSELIN, S. DE MORA, 2000. Dynamics of dimethylsulfide production from dissolved dimethylsulfoniopropionate in the Labrador Sea. Mar. Ecol. Prog. Ser., 202: 27-40 .

WOLFE, G.V., M. LEVASSEUR, G. CANTIN, S. MICHAUD, 2000. DMSP and DMS dynamics and microzooplankton grazing in the Labrador Sea : application of the dilution technique. Deep-Sea Res., Part I, 47: 2243-2264 .

WOLFE, G.V., M. LEVASSEUR, G. CANTIN, S. MICHAUD, 1999. Microbial consumption and production of dimethyl sulfide (DMS) in the Labrador Sea. Aquat. Microbiol. Ecol., 18: 197-205 .

CANTIN, G., M. LEVASSEUR, S. SCHULTES, S. MICHAUD, 1999. Dimethylsulfide (DMS) production by size-fractionated particles in the Labrador Sea. Aquat. Microbiol. Ecol., 19: 307-312 .

DESBIENS, M., J. ROY, S. MICHAUD, M. LEVASSEUR, 1998. Absence de biotoxines PSP dans les gonades d'oursins. MAPAQ, DIT, Doc. rech., 98/07, 5 p .

SAKKA, A., M. GOSSELIN, M. LEVASSEUR, S. MICHAUD, P. MONFORT, S. DEMERS, 1997. Effect of ultraviolet radiation on the marine production of dimethylsufoniopropionate and. Mar. Ecol. Prog. Ser., 149(1-3): 227-238 .

LEVASSEUR, M., S. SHARMA, G. CANTIN, S. MICHAUD, M. GOSSELIN, L. BARRIE, 1997. Biogenic sulfur emissions from the Gulf of Saint Lawrence and assessment of its impact on the Canadian east coast. J. Geophys. Res. (D Atmospheres), 102(D23): 28025-28039 .

CASTONGUAY, M., M. LEVASSEUR, J.-L. BEAULIEU, F. GRÉGOIRE, S. MICHAUD, E. BONNEAU, S.S. BATES, 1997. Accumulation of PSP toxins in Atlantic mackerel : seasonal and ontogenic variations. J. Fish Biol., 50: 1203-1213 .

CANTIN, G., M. LEVASSEUR, M. GOSSELIN, S. MICHAUD, 1996. Role of zooplankton in the mesoscale distribution of surface dimethylsulfide concentrations in the Gulf of St. Lawrence, Canada. Mar. Ecol. Prog. Ser., 141: 103-117 .

LEVASSEUR, M., S. MICHAUD, J. EGGE, G. CANTIN, J.C. NEJSTGAARD, R. SANDERS, E. FERNANDEZ, P.T. SOLBERG, B. HEIMDAL, M. GOSSELIN, 1996. Production of DMSP and DMS during a mesocosm study of an Emiliania huxleyi bloom : influence of bacteria and Calanus finmarchicus grazing. Mar. Biol., 126: 609-618 .

BEAULIEU, J.-L., M. CASTONGUAY, M. LEVASSEUR, F. GRÉGOIRE, S. MICHAUD, E. BONNEAU, S.S. BATES, 1996. Rôle des toxines IPM (intoxication paralysante par les mollusques) dans une mortalité de maquereau bleu (Scomber scombrus) en Nouvelle-Écosse en 1993 ; Role of PSP (Paralytic Shellfish Poisoning) toxins in an Atlantic mackerel (Scomber scombrus) mortality in Nova Scotia in 1993. Rapp. can. ind. sci. halieut. aquat. ; Can. Ind. Rep. Fish. Aquat. Sci., 236, 17 p .

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A mortality of Atlantic mackerel reported in Cape Breton in May 1993 prompted us to determine if paralytic shellfish poisoning (PSP) toxins could be identified as a potential cause of the kill. Live and dead mackerel collected in nearby traps had similar levels of PSP toxins in their livers. Additional mackerel were sampled from the commercial fishery in the southern and northern Gulf of St. Lawrence from June to October 1993. The total amount of PSP toxin per liver increased gradually with the age and the length of the fish, showing that mackerel bioaccumulate PSP toxins in their livers throughout their life. The quantity of PSP toxins per liver also increased during the summer, indicating that mackerel become comtaminated during their summer stay in the Gulf of St. Lawrence. By storing toxins in the liver, mackerel become potential lethal PSP vectors to their natural predators. However, eating mackerel poses no risk for humans as long as viscera are not consumed.

GOSSELIN, M., M. LEVASSEUR, N. SIMARD, S. MICHAUD, S. SHARMA, P. BRICKELL, T. BATES, 1996. Contribution of planktonic and ice algae to dimethylsulfide production across the Arctic ocean in Summer. Pages 42-44 in W. Tucker, D. Cate & V. Keating (ed.). The 1994 Arctic Ocean Section : the first major scientific crossing of the Arctic Ocean. U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, N.H. (Special report, 96-23) .

BRATBAK, G., M. LEVASSEUR, S. MICHAUD, G. CANTIN, E. FERNANDEZ, B.R. HEIMDAL, M. HELDAL, 1995. Viral activity in relation to Emiliania huxleyi blooms : a mechanism of DMSP release. Mar. Ecol. Prog. Ser., 128: 133-142 .

LEVASSEUR, M., T. GAMACHE, I. ST-PIERRE, S. MICHAUD, 1995. Does the cost of NO3- reduction affect the production of harmful compounds by Alexandrium excavatum?. Pages 463-468 Harmful Marine Algal Blooms : proceedings of the Sixth International Conference on Toxic Marine Phytoplankton, October 1993, Nantes, France. Lavoisier, Paris and Intercept Ltd, Andover, England .

LEVASSEUR, M., M. GOSSELIN, S. MICHAUD, 1994. A new source of dimethylsulfide (DMS) for the arctic atmosphere : ice diatoms. Mar. Biol., 121: 381-387 .

LAYCOCK, M.V., S.W. AYER, M. BILODEAU, J.-P. GAGNÉ, S. HSIAO, J.F. JELLETT, A. LAWRENCE, M. LEDOUX, P. MASSELIN, D. McLACHLAN, S. MICHAUD, S.K. MOHAPATRA, K. SOHET, I. ST-PIERRE, K. THOMAS, B.M. TWAROG, 1992. Detection and quantification of toxic algae and toxins. Pages 81-90 in J.-C. Therriault & M. Levasseur (ed.). Proceedings of the Third Canadian Workshop on Harmful Marine Algae, Maurice-Lamontagne lnstitute, Mont-Joli, Québec, 12-14 May, 1992 .

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