204 research outputs found
Evolutionary life-strategies of autotrophic planktonic microorganisms in the Baltic Sea
http://tartu.ester.ee/record=b1019947~S1*es
Algoloogia
BeSt programmi toetusel loodud e-kursuse eesmärk on anda põhjalik ülevaade vetikate ökoloogiast ja evolutsioonilisest süstemaatikast. Vetikate rakuehitus, morfoloogia ja füsioloogia. Vetikate fülogeneetiline süstemaatika eukarüootide fülogeneesi taustal. Vetikate ökoloogia. Vetikatega seotud keskkonnaprobleemid, vetikaõitsengud, toksilised vetikad meil ja mujal. Vetikate roll Maa biokeemilises ringes ja veekogude toiduahelates
Phytoplankton responses to meteorological and hydrological forcing at decadal to seasonal time scales
One of the challenges for predicting global
change effects on aquatic ecosystems is the vague
understanding of the mechanisms of multiple controlling
factors affecting phytoplankton dynamics at
different time scales. Here we distinguish between
hydrometeorological forcing of phytoplankton
dynamics at time scales from days to decades based
on a 54-year monthly phytoplankton time series from a
large shallow Lake Võrtsjärv (58 160N, 26 020E) in
Estonia, combined with daily data on forcing factors—
thermal-, wind-, light- and water-level regimes. By
using variance partitioning with linear mixed effect
modelling (LME), we found a continuum from the
large dominant K-selected filamentous cyanobacteria
with strongest decadal scale variation (8–30%) to
r-selected phytoflagellates with large stochastic variability
(80–96%). External forcing revealed strong
seasonal variation (up to 80%), while specifically
water level and wind speed had a robust decadal
variation (8% and 20%, respectively). The effect of
external variables was proportionally manifested in
the time scales of phytoplankton variation. Temperature,
with a clear seasonal variation, had no impact on
the dominant cold tolerant filamentous cyanobacteria
in Lake Võrtsjärv. We found the LME as a reliable
method for resolving the temporal cross-scale problem.
It yielded quantitative results that matched our
intuitive understanding of the dynamics of different
variables.Supplementary Information The online version of this
article (https://doi.org/10.1007/s10750-021-04594-x) contains
supplementary material, which is available to authorised users.This study was funded by MANTEL
ITN (Management of climatic extreme events in lakes and
reservoirs for the protection of ecosystem services) through
European Union’s Horizon 2020 research and innovation
programme under the Marie Skłodowska-Curie grant
agreement No 722518 and by the Estonian Research Council
grants (PRG1266 and PRG1167). We would also like to thank
Estonian Environment Agency for the long-term data used on
this study.This study was funded by MANTEL ITN (Management of climatic extreme events in lakes and reservoirs for the protection of ecosystem services) through European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 722518 and by the Estonian Research Council grants (PRG1266 and PRG1167). We would also like to thank Estonian Environment Agency for the long-term data used on this study
Classification of unknown primary tumors with a data-driven method based on a large microarray reference database
We present a new method to analyze cancer of unknown primary origin (CUP) samples. Our method achieves good results with classification accuracy (88% leave-one-out cross validation for primary tumors from 56 categories, 78% for CUP samples), and can also be used to study CUP samples on a gene-by-gene basis. It is not tied to any a priori defined gene set as many previous methods, and is adaptable to emerging new information
Decadal-Scale Changes of Dinoflagellates and Diatoms in the Anomalous Baltic Sea Spring Bloom
The algal spring bloom in the Baltic Sea represents an anomaly from the winter-spring bloom patterns worldwide in terms of frequent and recurring dominance of dinoflagellates over diatoms. Analysis of approximately 3500 spring bloom samples from the Baltic Sea monitoring programs revealed (i) that within the major basins the proportion of dinoflagellates varied from 0.1 (Kattegat) to >0.8 (central Baltic Proper), and (ii) substantial shifts (e.g. from 0.2 to 0.6 in the Gulf of Finland) in the dinoflagellate proportion over four decades. During a recent decade (1995–2004) the proportion of dinoflagellates increased relative to diatoms mostly in the northernmost basins (Gulf of Bothnia, from 0.1 to 0.4) and in the Gulf of Finland, (0.4 to 0.6) which are typically ice-covered areas. We hypothesize that in coastal areas a specific sequence of seasonal events, involving wintertime mixing and resuspension of benthic cysts, followed by proliferation in stratified thin layers under melting ice, favors successful seeding and accumulation of dense dinoflagellate populations over diatoms. This head-start of dinoflagellates by the onset of the spring bloom is decisive for successful competition with the faster growing diatoms. Massive cyst formation and spreading of cyst beds fuel the expanding and ever larger dinoflagellate blooms in the relatively shallow coastal waters. Shifts in the dominant spring bloom algal groups can have significant effects on major elemental fluxes and functioning of the Baltic Sea ecosystem, but also in the vast shelves and estuaries at high latitudes, where ice-associated cold-water dinoflagellates successfully compete with diatoms
Alexandrium fundyense cyst viability and germling survival in light vs. dark at a constant low temperature
Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 103 (2014): 112–119, doi:10.1016/j.dsr2.2013.05.010.Both observations and models suggest that large-scale coastal blooms of Alexandrium fundyense in the
Gulf of Maine are seeded by deep-bottom cyst accumulation zones (“seed beds”) where cysts
germinate from the sediment surface or the overlying near-bottom nepheloid layers at water depths
exceeding 100 m. The germling cells and their vegetative progeny are assumed to be subject to modest
mortality while in complete darkness as they swim to illuminated surface waters. To test the validity of
this assumption we investigated in the laboratory cyst viability and the survival of the germling cells
and their vegetative progeny during prolonged exposure to darkness at a temperature of 6°C,
simulating the conditions in deep Gulf of Maine waters. We isolated cysts from bottom sediments
collected in the Gulf of Maine under low red light and incubated them in 96-well tissue culture-plates
in culture medium under a 10:14h light: dark cycle and under complete darkness. Cyst viability was
high, with excystment frequency reaching 90% in the illuminated treatment after 30 days and in the
dark treatment after 50 days. Average germination rates were 0.062 and 0.038 d-1 for light and dark
treatments, respectively. The dark treatment showed an approximately two-week time lag in maximum
germination rates when compared to the light treatment. Survival of germlings was considerably lower
in the dark treatment. In light treatments, 47% of germinated cysts produced germlings that were able to survive for 7 days and produce vegetative progeny, i.e. there were live cells in the well along with an
empty cyst at least once during the experiment. In the dark treatments 12% of cysts produced germlings
that were able to survive. When dark treatments are scaled to take into account non-darkness related
mortality, approximately 28% of cysts produced germlings that were able to survive for at least 7 days.
Even though cysts are able to germinate in darkness, the lack of illumination considerably reduces
survival rate of germling cells. In addition to viability of cysts in surface sediments and the near-bottom
nepheloid layer, survivability of germling cells and their vegetative progeny at aphotic depths is an
important consideration in assessing the quantitative role of deep-coastal cyst seed beds in bloom
formation.E. Vahtera was funded by the Academy of Finland (grant #130934) and B. Gomez-Crespo was
supported by a Xunta de Galicia Ángeles Alvariño fellowship. Additional funding support was also
provided by the National Oceanic Atmospheric Administration ECOHAB program through grants
NA06NOS4780245 and NA09NOS4780193 and from National Science Foundation grants OCE-
0430724 and OCE-0911031 and National Institute of Environmental Health Sciences grant 1P50-
ES01274201 through the Woods Hole Center for Oceans and Human Health
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