Biologie et Quebec-Ocean, Takuvik-IBIS

Pellicle or temporary cysts of Pyrodinium bahamense var. compressum (Böhm) Steidinger, Tester & F.J.R. Taylor and their role in bloom dynamics have not yet been adequately characterized and understood. We investigated the role of temperature-and nutrient-mediated stress as factors that could induce pellicle formation in batch cultures. Cellular features and their implications for temporary cyst viability were examined using confocal laser scanning microscopy (CLSM). Our data suggest that temperature change is one of the key factors influencing pellicle formation, preserving viability at low temperature (i.e. 13°C). Hypnocysts (resting cysts) were not observed. During pellicle formation, motile cells generally undergo ecdysis, extrusion of cytoplasmic materials and bacteria, compaction of the nucleus and non-motility. The outermost covering of the temporary cysts shows red autofluorescence and it contains lower concentrations of chlorophyll (chl) a and no detectable chl c. The nuclear region is surrounded by transitional red bodies and other unidentified cellular structures. Temporary cysts can immediately revert back to the motile state upon exposure to optimum conditions. This is accompanied by the expansion of the nuclear region, regeneration of the chloroplasts and enlargement of the cell. Developmental changes during reversal of temporary cysts to motile forms were also observed to cause breaks in the cell covering that could serve as sites for bacterial entry. Though observed in vitro, such behaviour may also be occurring in nature especially as a response to drastic short-lived environmental changes. This is the first detailed report on the characteristics of temporary cysts of P. bahamense var. compressum.

Many aspects of the biology and ecology of the toxic dinoflagellate Pyrodinium bahamense var. compressum are still poorly understood. In this brief note, we present identification of its associated intracellular bacteria or endosymbionts via PCR cloning and 16s rRNA gene sequencing and their localization by confocal microscopy, a first for Pyrodinium. The most frequently observed species in the endosymbiotic microflora were from Roseobacter clade (Alphaproteobacteria, 68 %) and Gilvibacter sediminis (Flavobacteriaceae, 20 %). Roseobacter lineage, the most abundant taxa in this study, is known to be involved in dimethylsulfoniopropionate metabolism which is highly produced in dinoflagellates—a possible strong factor shaping the structure of the associated bacterial community.

Recent studies have focused on how climate change could drive changes in phytoplankton communities in the Arctic. In contrast, ciliates and dinoflagellates that can contribute substantially to the mortality of phytoplankton have received less attention. Some dinoflagellate and ciliate species can also contribute to net photosynthesis, which suggests that species composition could reflect food web complexity. To identify potential seasonal and annual species occurrence patterns and to link species with environmental conditions, we first examined the seasonal pattern of microzooplankton and then performed an in-depth analysis of interannual species variability. We used high-throughput amplicon sequencing to identify ciliates and dinoflagellates to the lowest taxonomic level using a curated Arctic 18S rRNA gene database. DNA-and RNA-derived reads were generated from samples collected from the Canadian Arctic from November 2007 to July 2008. The proportion of ciliate reads increased in the surface toward summer, when salinity was lower and smaller phytoplankton prey were abundant, while chloroplastidic dinoflagellate species increased at the subsurface chlorophyll maxima (SCM), where inorganic nutrient concentrations were higher. Comparing communities collected in summer and fall from 2003 to 2010, we found that microzooplankton community composition change was associated with the record ice minimum in the summer of 2007. Specifically, reads from smaller predatory species like Laboea, Monodinium, and Strombidium and several unclassified ciliates increased in the summer after 2007, while the other usually summer-dominant dinoflagellate taxa decreased. The ability to exploit smaller prey, which are predicted to dominate the future Arctic, could be an advantage for these smaller ciliates in the wake of the changing climate.

The annual routines and seasonal ecology of herbivorous zooplankton species are relatively well known due to their tight coupling with their pulsed food source, the primary production. For higher trophic levels of plankton, these seasonal interactions are less well understood. Here, we study the mid-winter feeding of chaetognaths in high-Arctic fjord ecosystems. Chaetognaths are planktivorous predators which comprise high biomass in high-latitude seas. We investigated the common species Parasagitta elegans around the Svalbard archipelago (78–81°N) during the winters of 2012 and 2013. Our samples consisted of individuals (body lengths 9–55 mm) from three fjords, which were examined for gut contents (n = 903), stable isotopes, fatty acid composition, and maturity status (n = 352). About a quarter of the individuals contained gut contents, mainly lipid droplets and chitinous debris, whilst only 4 % contained identifiable prey, chiefly the copepods Calanus spp. and Metridia longa. The δ15N content of P. elegans, and its average trophic level of 2.9, confirmed its carnivorous position and its fatty acid profile [in particular its high levels of 20:1(n-9) and 22:1(n-11)] confirmed carnivory on Calanus. Observations of undeveloped gonads in many of the larger P. elegans, and the absence of small individuals <10 mm, suggested that reproduction had not started this early in the year. Its average feeding rate across fjords and years was 0.12 prey ind.−1 day−1, which is low compared to estimates of spring and summer feeding in high-latitude environments. Our findings suggest reduced feeding activity during winter and that predation by P. elegans had little impact on the mortality of copepods.

Bio-optical measurements off Visakhapatnam Coastal Waters (VCW) East
Coast of India along Bay of Bengal (BoB) were carried out over several field
campaigns in 2009 and 2010. These campaigns were performed over different
periods of the year in order to obtain separate samplings of the system’s
seasonal cycles. The goal of these field campaigns is to arrive at a consistent
remote sensing algorithm for the estimation of the chlorophyll concentration in
the Case-2 waters (where optical properties are influenced not just by
phytoplankton and co varying constituents, but also by non-co varying
constituents such as gelbstoff and suspended sediments), of the VCW. The
optical components of these missions included measurements of inherent and
apparent in-situ optical parameters. Preliminary results using profiling
radiometer were carried out for the characterization and classification of the
Visakhapatnam coastal waters. In this presentation focus will be given on the
observation and analysis of variations in the optical constituents and
reflectance characteristics.

Measurements of the spectral absorption coefficient of natural particulates in
Visakhapatnam coastal waters of Bay of Bengal, along the East Coast of India
were performed to determine the principal pigments responsible for the
absorption of spectral irradiance in seawater. Overlapping spectra of the
individual pigments shows a characteristic of a continuous envelope for the
absorption of photosynthetic algae. This feature makes it complex to estimate
the contribution of each pigment to the total absorption spectra. Derivative
analysis is an objective tool for isolating absorption peaks in phytoplankton.
The spectral absorption coefficient, ap (λ), was then analyzed by taking the
fourth derivative with respect to wavelength. The wavelength and magnitude
of these derivative values provide useful information regarding the
identification and quantification of phytoplankton pigments responsible for a
given spectral signature. The peaks found in Visakhapatnam Coastal waters
with the fourth derivative analysis are consistent of Chlorophyll a (438 nm),
Chlorophyll c (467, 632, 648 nm) and carotenoid pigments, fucoxanthin (462,
509-518 nm).

Abstract Absorption spectra, particulate pigments, and
hydrochemical constituents were measured in the western
Bay of Bengal (BoB) during July-August 2010 when influence
of river discharge is at peak. Chromophoric dissolved
organic matter (CDOM) absorption coefficient (aCDOM(440))
displayed a significant inverse linear relationship with salinity
in the surface waters implying conservative mixing of marine
and terrestrial end members. The northern part of the study
area is influenced by discharge from the river Ganga and a
dominant terrestrial CDOM signal is seen. The southern part
receives discharge from peninsular rivers with corresponding
signals of higher CDOMthan the linear model would indicate
and higher UV-specific absorption coefficient (SUVA) indicating
more aged and humified DOM. Lower contribution of
CDOM to total non-water absorption and higher phytoplankton
biomass (chlorophyll a absorption coefficient, aph(440))
but lower chlorophyll a specific phytoplankton absorption
coefficient (aph
* (440)) characterize the northern part, compared
to the southern part. Chlorophyll b had a distinct linear relationship
with chlorophyll a in the latter. The size index (SI)
indicated dominance of microphytoplankton in the northern
and nano and picophytoplankton in the southern parts.
Chlorophyll a is significantly related to aph
* (440) by an inverse
power model in the northern part but by an inverse linear
model in the southern part. Our study suggests that knowledge
of the phytoplankton community structure is essential to improve
chlorophyll a algorithm in the coastal Bay of Bengal.

Abstract
The light absorption properties of a dinoflagellate (Noctiluca scintillans Macartney)
bloom in Manila Bay were analysed during the onset of a whole-bay-scale bloom in
March 2004. The chlorophyll a concentrations varied over a very wide range from
1.4 μg l−1 to extremely high values of 521 μg l−1. The chlorophyll specific absorption
coefficients of phytoplankton (a
ph()) varied significantly in shape and magnitude.
The spectrally averaged values of a
ph() varied by two orders of magnitude Abstract
The light absorption properties of a dinoflagellate (Noctiluca scintillans Macartney)
bloom in Manila Bay were analysed during the onset of a whole-bay-scale bloom in
March 2004. The chlorophyll a concentrations varied over a very wide range from
1.4 μg l−1 to extremely high values of 521 μg l−1. The chlorophyll specific absorption
coefficients of phytoplankton (a
ph()) varied significantly in shape and magnitude.
The spectrally averaged values of a
ph() varied by two orders of magnitude within and outside the bloom patch. The total suspended solid concentration was
high in the middle of the bay (4 mg l−1). The non-photosynthetic pigment
(NPP) index was 0.6 at most of the stations, mainly due to the presence of
photoprotective pigments like zeaxanthin, lutein and neoxanthin, which led to
variations in the blue absorption maxima of the chlorophyll-specific absorption
coefficients. The absorption properties of the accessory pigments were masked
owing to the presence of overlapping pigment absorption bands. The fourth
derivative of the absorption spectra was able to resolve these overlapping features
and enhance the absorption characteristics of prominent accessory pigments.

The light absorption properties of a dinoflagellate (Noctiluca scintillans Macartney) bloom in Manila Bay were analysed during the onset of a whole-bay-scale bloom in March 2004. The chlorophyll a concentrations varied over a very wide range from 1.4 µg l −1 to extremely high values of 521 µg l −1 . The chlorophyll specific absorption coefficients of phytoplankton (a * ph (λ)) varied significantly in shape and magnitude. The spectrally averaged values of a * ph (λ) varied by two orders of magnitude

Transcranial Doppler (TCD) is a diagnostic tool that can be used at bedside to assess the cerebral vasculature noninvasively. It is inexpensive, safe, and reliable when compared with other techniques. It can be repeated multiple times and can be used for continuous monitoring if needed. Screening of children with sickle cell disease to assess and prevent ischemic strokes and monitoring for vasospasm after subarachnoid hemorrhage are well established, evidenced based utilizations of TCD. It is useful for the evaluation of occlusive intracranial vascular lesions with many emerging indications in the management of ischemic stroke. TCD with micro-bubble enhancement has comparable sensitivity to transesophageal echocardiogram in detecting right-to-left atrial cardiac shunts. TCD is underused as a clinical tool despite well established indications. The pressure to contain increasing medical cost will likely result in increased utilization of this test in future. (J Am Board Fam Med 2007;20:65-71.)

This review article reveals that men are generally more influential than women, although the gender difference depends on several moderators. Relative to men, women are particularly less influential when using dominant forms of communication, whereas the male advantage in influence is reduced in domains that are traditionally associated with the female role and in group settings in which more than one woman or girl is present. Males in particular resist influence by women and girls more than females do, especially when influence agents employ highly competent styles of communication. Resistance to competent women can be reduced, however, when women temper their competence with displays of communality and warmth.

Almost all of the exisiting known antagonists at the glycine site of the N-methyl-D-aspartate (NMDA) receptor have a low propensity for crossing the blood-brain barrier. It has been suggested that in many cases this may be due to the presence of a carboxylic acid which is a common feature of most of the potent full antagonists at this receptor. In this study, 2-aryl-VI-pyrazolo[3,4-clquinoline-l,4(fL'J-n-diones were found to have high-affinity binding at the glycine receptor. In particular, structure-activity studies identified 7-chloro-3,5-dihydro-2-~4-methoxyphenyl)-V-l-pyrazolo~3,4-clquinoline-1,4(~-dione as the most potent of a series of analogues with an 1% of 3.3 nM. "he measured pKa values in this class of compounds (typically 4.0) indicate they are of equivalent acidity to carboxylic acids. Functional antagonism was demonstrated by inhibition of NMDA-evoked responses in rat cortical slices. Anticonvulsant activity in DBN2 mice was achieved afier dosing by direct injection into the cerebral ventricles, but no activity was seen after systemic administration, suggesting low brain penetration with this class of antagonists. 0 1995 American Chemical Society