Elisabeth Nézan

Ovatoxin-a and Palytoxin Accumulation in Seafood in Relation to Ostreopsis cf. ovata Blooms on the French Mediterranean Coast

Dinoflagellates of the genus Ostreopsis are known to cause (often fatal) food poisoning in tropical coastal areas following the accumulation of palytoxin (PLTX) and/or its analogues (PLTX group) in crabs, sea urchins or fish. Ostreopsis spp. occurrence is presently increasing in the northern to north western Mediterranean Sea (Italy, Spain, Greece and France), probably in response to climate change. In France, Ostreopsis. cf. ovata has been associated with toxic events during summer 2006, at Morgiret, off the coast of Marseille, and a specific monitoring has been designed and implemented since 2007. Results from 2008 and 2009 showed that there is a real danger of human poisoning, as these demonstrated bioaccumulation of the PLTX group (PLTX and ovatoxin-a) in both filter-feeding bivalve molluscs (mussels) and herbivorous echinoderms (sea urchins). The total content accumulated in urchins reached 450 µg PLTX eq/kg total flesh (summer 2008). In mussels, the maximum was 230 µg eq PLTX/kg (summer 2009) compared with a maximum of 360 µg found in sea urchins during the same period at the same site. This publication brings together scientific knowledge obtained about the summer development of Ostreopsis spp. in France during 2007, 2008 and 2009.

Growth anomalies in Pecten maximus from coastal waters (Bay of Brest, France): relationship with diatom blooms

The aim of this study was to characterize the daily shell growth of Pecten maximus from early 1998 to late spring 1999 in the Bay of Brest with a careful qualitative and quantitative description of the pelagic primary production. Our results, in accordance with previous studies, demonstrate that there are episodic declines in the growth rate. Concurrent events of low growth rate and large bottom-concentrations of algae following diatom blooms (Cerataulina pelagica or Rhizosolenia delicatula), suggests that this high concentration of phytoplankton on the bottom layer may affect food intake or respiratory activity of the scallops by gill clogging or oxygen depletion. In this study, silicic acid or phosphorus are inferred to be limiting factors responsible for the collapse of the spring bloom. Further, we suggest that, in an N-enriched ecosystem, Si or P-limitation and the changing sinking velocities of phytoplankton, could affect the biology of benthic suspension-feeders.

Satellite and in situ observations of a late winter phytoplankton bloom, in the northern Bay of Biscay

A phytoplankton bloom was observed in late winter 2000, on the continental shelf offshore of southern Brittany, in northwestern Bay of Biscay. This bloom appeared initially along the 120-m isobath, in stratified and clear waters, at the interface between the oceanic water and the plumes of southern Brittany rivers (mainly the Loire and Vilaine). The development of the bloom was triggered by favourable meteorological conditions, characterised by solar irradiance reaching the maximum level expected for that period of the year. Outside of the bloom area, the phytoplankton photosynthesis was irradiance limited: inshore, because of the stronger attenuation of the light; offshore, because of the weak stratification. The hydrological conditions at the onset of the bloom were observed in the field, during the oceanographic cruise MODYCOT. However, without SeaWiFS, the only observations related to this major event in the primary production would have been those of the coastal phytoplankton network (REPHY (REseau PHYtoplankton)).

TAXONOMIC REVISION OF THE DINOFLAGELLATE AMPHIDOMA CAUDATA: TRANSFER TO THE GENUS AZADINIUM (DINOPHYCEAE) AND PROPOSAL OF TWO VARIETIES, BASED ON MORPHOLOGICAL AND MOLECULAR PHYLOGENETIC ANALYSES

The systematic position of Amphidoma caudata Halldal within the genus Amphidoma has remained uncertain as a result of its plate formula and the absence of molecular phylogenetic data. Also, this thecate dinoflagellate taxon has been used to designate two distinct morphotypes. The present study aims to clarify the generic affiliation of Amphidoma caudata and the taxonomic value of two different morphotypes M1 and M2. The new examination of the plate formula using SEM showed that it was the same for both morphotypes and that it corresponded to the tabulation of the recent erected genus Azadinium Elbrächter et Tillmann. Morphometric analysis, using cell size, length of apical projection in conjunction with the cell length, and the ratio of horn and spine showed that M1 and M2 formed two distinct groups. These results were supported by a molecular approach, revealing notable differences in the sequences of LSU rDNA and ITS region between these two morphotypes. Phylogenetic analyses inferred either from LSU and combined SSU, ITS region and COI data positioned M1 and M2 in a sister cluster of Azadinium species while Amphidoma languida Tillmann, Salas et Elbrächter, the only species of Amphidoma for which sequence data were available, was situated in a basal position of the Azadinium clade. Thus, we propose the transfer of Amphidoma caudata to the genus Azadinium and, consequently, the rehabilitation of the original tabulation of the genus Amphidoma Stein. To discriminate the two morphotypes, we propose a rank of variety with the following designations: Azadinium caudatum var. caudatum and Azadinium caudatum var. margalefii.

Variations in food intake of Pecten maximus (L.) from the Bay of Brest (France): influence of environmental factors and phytoplankton species composition.

Previous studies carried out in the bay of Brest on daily shell growth of Pecten maximus have demonstrated that temperature is a major control on daily shell growth in contrast to food supply. However, repeated events of slow growth have been observed during diatom and dinoflagellate blooms. The aim of this study was to determine how fluctuations in environmental parameters influence P. maximus food intake and daily shell growth rate. In 1995, P. maximus food intake and growth were highest when Cerataulina pelagica (diatom) blooms occurred and lowest during Gymnodinium cf. nagasakiense (dinoflagellate) blooms. During blooms of other diatom species, P. maximus food intake and growth were high when the algal concentration did not exceed a critical threshold, dependent upon the dominant species and sedimentation rate of diatoms. These results demonstrate that the morphological and physiological features of phytoplankton bloom species strongly affect benthic microphytophagy, a component of benthic-pelagic coupling.

MORPHOLOGY AND MOLECULAR PHYLOGENY OF PROROCENTRUM CONSUTUM SP. NOV. (DINOPHYCEAE), A NEW BENTHIC DINOFLAGELLATE FROM SOUTH BRITTANY (NORTHWESTERN FRANCE)1

A new marine benthic Prorocentrum species from sandy habitats of South Brittany (northwestern France), P. consutum sp. nov., is described using LM and SEM and molecular phylogenetic analyses. Cells have a subcircular to broadly ovoid shape and are plainly flattened. They are 57–61 μm long and 52–55 μm wide. A central pyrenoid is present, and the kidney‐shaped nucleus is positioned in the posterior region. In right valve view, the periflagellar area is deeply excavated, and the left valve forms a prominent apical ridge. The periflagellar area consists of nine platelets, and a small narrow collar is present around the flagellar pore. The ornamentation of this new species is very peculiar and is characterized by a ring of round areolae located at the periphery of the valves, each areola containing three or four pores. Apart from this ring of areolae, the cell surface is smooth and with scattered pores. Pores are not present in the center of the right or left valve. The intercalary band is generally narrow and faintly striated horizontally. The molecular phylogenetic position of P. consutum sp. nov. was inferred using SSU and LSU rDNA. In both analyses, this species branched with high support in the clade comprising species with a symmetric shape and appeared to be a sister group to that formed by P. lima and other tropical benthic species, such as P. arenarium, P. belizeanum, P. hoffmannianum, and P. maculosum.

Interactions between scientists, managers and policy makers in the framework of the French MediOs project on Ostreopsis (2008-2010)

Abstract The main goal of the multidisciplinary MediOs project was to acquire and analyze pertinent scientific knowledge in fields as diverse as ecology, biology, chemistry, epidemiology or socio-economics concerning the occurrence of species belonging to genus Ostreopsis (toxic benthic dinoflagellates) in the Mediterranean. The economic impact of Ostreopsis was estimated, based on the intensity and frequency of blooms. Results obtained allowed science-based recommendations concerning the management of risk, with suggestions to optimize environmental surveys, to initiate a food risk survey, and to structure actions at the national level.

Prorocentrum glenanicum sp. nov. and Prorocentrum pseudopanamense sp. nov. (Prorocentrales, Dinophyceae), two new benthic dinoflagellate species from South Brittany (northwestern France)

Chomérat N., Zentz F., Boulben S., Bilien G., van Wormhoudt A. and Nézan E. 2011. Prorocentrum glenanicum sp. nov. and Prorocentrum pseudopanamense sp. nov. (Prorocentrales, Dinophyceae), two new benthic dinoflagellate species from South Brittany (northwestern France). Phycologia 50: 202–214. DOI: 10.2216/10-12.1 Two new marine benthic Prorocentrum species, Prorocentrum glenanicum sp. nov. and Prorocentrum pseudopanamense sp. nov., are described from sandy sediments of South Brittany (northwestern France). The morphology was examined using light and scanning electron microscopy, and the molecular phylogeny was inferred from sequences of the small ribosomal subunit (SSU rDNA). Morphologically, cells of Prorocentrum glenanicum sp. nov. have a broadly oval to circular shape and measure 30–33 µm in length and 29–31 µm in width. Prorocentrum pseudopanamense sp. nov. is slightly asymmetrically oval, 46–51 µm long and 44–47 µm wide. The theca of Prorocentrum glenanicum sp. nov. is smooth and ornamented with shallow circular depressions containing a pore while it is areolated in Prorocentrum pseudopanamense sp. nov. Both species exhibit an asymmetric ornamentation between left and right valves. In Prorocentrum glenanicum sp. nov., two distinct groups of areolae are observed on the right valve only: a group of about 20 is located just above the centre of the valve, and another dense group is present in the posterior part of the cell. In Prorocentrum pseudopanamense sp. nov., a large depression containing several pores is present in the posterior part of the valves. In both species, the periflagellar area comprises nine platelets and is very slightly excavated. The molecular analysis confirmed the establishment of the taxa as new species. In the molecular tree inferred from SSU rDNA they grouped with Prorocentrum panamense and formed a distinct group within clade 1 of Prorocentrum, which comprised mostly asymmetric species.

Some Prymnesiaceae (Haptophyta, Prymnesiophyceae) from the Mediterranean Sea, with the description of two new species: Chrysochromulina lanceolata sp. nov. and C. pseudolanceolata sp. nov.

Five species belonging to the family Prymnesiaceae (one Prymnesium and four Chrysochromulina) have been identified in cultures obtained from water collected in the Bay of Banyuls‐sur‐Mer (Mediterranean Sea, France) using LM, SEM, and TEM. Two are described as new species, Chrysochromulina lanceolata sp. nov. and C. pseudolanceolata sp. nov. Both species are large and lanceolate with an acute posterior and two anterior arms. They are easily detectable with LM but difficult to distinguish to species level with live cells, without experience. EM reveals two completely different scale patterns in the two species. Cells of C. lanceolata are 21–38 μm long, 7–12 μm wide, and 3–7 μm thick. They possess two subequal flagella (30–51 and 29–44 μm), and the haptonema is shorter than the flagella (23–37 μm). The cell body is covered by plate and spine scales. Cells of C. pseudolanceolata sp. nov. are slightly smaller (15–18 × 6–8 μm) with more rounded extremities, two subequal flagella (19–26 and 17–24 μm), and the haptonema is longer than the flagella (about 35 μm). Three types of plate scales are observed in this species. Other findings are C. alifera Parke et Manton and C. throndsenii Eikrem (a new record for the Mediterranean Sea). Prymnesium faveolatum Fresnel, a new toxic species recently described, is illustrated with both LM and SEM.

First records of Amphidoma languida and Azadinium dexteroporum (Amphidomataceae, Dinophyceae) from the Irminger Sea off Iceland

Species of dinophycean Amphidomataceae are producers of phycotoxins classified as azaspiracids. We provide the first records of two of their constituent species, Amphidoma languida and Azadinium dexteroporum, for the Irminger Sea off Iceland. Morphological examination and molecular characterization, including uncorrected mean pairwise distances between sequences of the Internal Transcribed Spacer (ITS), doubtlessly assigned the sub-Arctic strain 2A11 to the reference of Amphidoma languida. Strain 2A11 produced AZA-38 and AZA-39, corresponding to the toxin profile described for the type material. The sub-Arctic isolate 1D12 differed significantly in terms of ITS genetic distance (p = 0.04) from a Mediterranean Azadinium dexteroporum strain, but our morphological analysis did not reveal any major or stable diagnostic traits between the reference strain of Azadinium dexteroporum and the new strain described here. In contrast to the Mediterranean strain of Azadinium dexteroporum, the sub-Arctic strain 1D12 did not produce any known azaspiracids. The new records of Amphidoma languida and Azadinium dexteroporum from the Irminger Sea imply an important range extension of the species, formerly known from the northern and eastern Atlantic (Amphidoma languida) and from the Mediterranean area (Azadinium dexteroporum) only. Together with three new species of Azadinium recently described from the same expedition, the results clearly show that the biodiversity of the Amphidomataceae in the sub-Arctic is remarkably large.