14 research outputs found
Picobiliphytes: A marine picoplanktonic algal group with unknown affinities to other eukaryotes
Environmental sequencing has revealed unimagined diversity among eukaryotic picoplankton. Here, a distinct picoplanktonic algal group (table S1), initially detected from 18S rDNA sequences, was hybridized with rRNA probes, detected by Tyramide Signal Amplification - Fluorescent In Situ Hybridization (TSA-FISH) and showed an organelle-like body with orange fluorescence indicative of phycobilins. Using this fluorescence signal, cells were sorted by flow cytometry and probed. Hybridized cells contained a DAPI staining organelle resembling a plastid with a nucleomorph. This suggests that they may be secondary endosymbiotic algae. Pending isolation of living cells and their formal description these algae have been termed picobiliphytes
Seasonal occurrence at a Scottish PSP monitoring site of purportedly toxic bacteria originally isolated from the toxic dinoflagellate genus Alexandrium
Seasonal occurrence at a Scottish PSP monitoring site of purportedly toxic bacteria originally isolated from the toxic dinoflagellate genus Alexandrium
Intercalibration of classical and molecular techniques for identification of Alexandrium fundyense (Dinophyceae) and estimation of cell densities
A workshop with the aim to compare classical and molecular techniques for phytoplankton enumeration took place at Kristineberg Marine Research Station, Sweden, in August 2005. Seventeen different techniques - nine classical microscopic-based and eight molecular methods - were compared. Alexandrium fundyense was the target organism in four experiments. Experiment 1 was designed to determine the range of cell densities over which the methods were applicable. Experiment 2 tested the species specificity of the methods by adding Alexandrium ostenfeldii, to samples containing A. fundyense. Experiments 3 and 4 tested the ability of the methods to detect the target organism within a natural phytoplankton community. Most of the methods could detect cells at the lowest concentration tested, 100 cells L-1, but the variance was high for methods using small volumes, such as counting chambers and slides. In general, the precision and reproducibility of the investigated methods increased with increased target cell concentration. Particularly molecular methods were exceptions in that their relative standard deviation did not vary with target cell concentration. Only two of the microscopic methods and three of the molecular methods had a significant linear relationship between their cell count estimates and the A. fundyense concentration in experiment 2, where the objective was to discriminate that species from a morphologically similar and genetically closely related species. None of the investigated methods were affected by the addition of a natural plankton community background matrix in experiment 3. The results of this study are discussed in the context of previous intercomparisons and the difficulties in defining the absolute, true target cell concentration
Hierarchical probes at various taxonomic levels in the Haptophyta and a new division level probe for the Heterokonta
The overwintering of Antarctic krill, Euphausia superba, from an ecophysiological perspective
A major aim of this review is to determine
which physiological functions are adopted by adults and
larvae to survive the winter season with low food supply
and their relative importance. A second aim is to clarify the
extent to which seasonal variation in larval and adult krill
physiology is mediated by environmental factors with a
strong seasonality, such as food supply or day light. Experimental
studies on adult krill have demonstrated that speciWc
physiological adaptations during autumn and winter,
such as reduced metabolic rates and feeding activity, are
not caused simply by the scarcity of food, as was previously
assumed. These adaptations appear to be inXuenced
by the local light regime. The physiological functions that
larval krill adopt during winter (reduced metabolism,
delayed development, lipid utilisation, and variable growth
rates) are, in contrast to the adults, under direct control by
the available food supply. During winter, the adults often
seem to have little association with sea ice (at least until
early spring). The larvae, however, feed within sea ice but
mainly on the grazers of the ice algal community rather
than on the algae themselves. In this respect, a miss-match
in timing of the occurrence of the last phytoplankton
blooms in autumn and the start of the sea ice formation, as
has been increasingly observed in the west Antarctic Peninsula
(WAP) region, will impact larval krill development
during winter in terms of food supply and consequently the
krill stock in this region