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Latvijas Zinātņu akadēmijas, Latvijas Universitātes Astronomijas institūta populārzinātnisks gadalaiku izdevums
2012
Contents: JĀNIS IKAUNIEKS – 100: N.Cimahoviča. Subjacent Was Venture ; I.P. Articles on Jānis Ikaunieks and Articles by Jānis Ikaunieks in Zvaigžņotā debess ; “ZVAIGŽŅOTĀ DEBESS” FORTY YEARS AGO: A.Balklavs. Ball Lightning and Solar Activity (abridged) ; Streamer with the USSR State Emblem on Mars (TASS materials) ; NEWS: I.Eglītis. Asteroid Baldone – Christmas Gift for Latvia ; I.Eglītis. LUAI Astrophysics Observatory Discovers First Trojan Asteroid ; V.Kalniņš. Exceeding Speed of Light in CERN Experiment from the Theory of Relativity Viewpoint ; O.Dumbrājs. Higgs Boson ; NOBEL PRIZE WINNERS: D.Docenko. Nobel Prize in Physics for Discovery of Accelerating Expansion of Universe ; SPACE RESE…
Seasonal zooplankton patterns in a shallow oligotrophic lake: Loch Rusky (Scotland)
1990
The zooplankton taxa and their seasonal distribution are describeb for Loch Rusky, a shallow oligotrophic lake in the central region of Scotland. 15 species were indentified: 11 Rotifera, 2 Cladocera and 2 Copepoda. Only 5 species Polyarthra remata, Keratella cochlearis, Filinia terminalis, Trichocerca sp. and Eudiaptomus gracilis occurred in sufficient numbers to facilitate a description of their seasonal pattern. The annual zooplankton variation was dominated by rotifers for most of the year, but copepods (E. gracilis, Cyclops sp.) only were dominant in the epilimnion during summer. It is presumed that this pattern was the result of the rotifers faster rate of reproduction and higher graz…
Latvijas ūdeņu vides pētījumi un aizsardzība: LU Bioloģijas fakultātes Bioloģijas sekcijas referātu tēžu krājums (Rīga, 2013. gada 18. februāris)
2013
Latvijas Universitātes 71. zinātniskās konferences Bioloģijas sekcijas sēde (Rīga, 2013. gada 18. februāris) veltīta Prof. Heinriha Skujas 120. dzimšanas dienai.
Zvaigžņotā Debess: 2010, Pavasaris (207)
2010
Contents: E.Cielēns. Have Events in Space Influenced Evolution of Life on the Earth? ; A.Balklavs. Do Pulsars Radiate also in X-Rays? ; Soviet Press materials. Satellite of Friendship In Orbit ; I.Kalviņš. Innovation in Latvia: an Illusion or Reality? ; I.Eglītis. Half Comet-Half Asteroid Discovered With Baldone Schmidt Telescope ; A.Alksnis. While Rosetta is on the Fly from Steins to Lutetia ; M.Gills. Astronomy beyond 2009 ; IAU1001 Press Release. The International Year of Astronomy 2009: The Largest Science Education and Public Outreach Event in History ; J.Limansky. The International Year of Astronomy 2009 in Philately. Series EUROPA ; A.Bruņeniece, I.Dudareva. Wonders of the Solar Syst…
Suitability of Phytosterols Alongside Fatty Acids as Chemotaxonomic Biomarkers for Phytoplankton
2016
The composition and abundance of phytoplankton is an important factor defining ecological status of marine and freshwater ecosystems. Chemotaxonomic markers (e.g., pigments and fatty acids) are needed for monitoring changes in a phytoplankton community and to know the nutritional quality of seston for herbivorous zooplankton. Here we investigated the suitability of sterols along with fatty acids as chemotaxonomic markers using multivariate statistics, by analyzing the sterol and fatty acid composition of 10 different phytoplankton classes including altogether 37 strains isolated from freshwater lakes. We were able to detect a total of 47 fatty acids and 29 sterols in our phytoplankton sampl…
Impairing the largest and most productive forest on our planet: how do human activities impact phytoplankton?
2012
This article summarizes the outcomes of the 16th Workshop of the International Association for Phytoplankton Taxonomy and Ecology. Four major issues dealing with the impact exerted by human activities on phytoplankton were addressed in the articles of this special volume: climate change and its impacts on phytoplankton, the role of land use in shaping composition and diversity of phytoplankton, the importance of autecological studies to fully understand how phytoplankton is impacted by stressors and the role of ecological classification to evaluate community changes due to the different impacts. Case studies from different types of aquatic environments (rivers, deep and shallow lakes, reser…
Potential predation pressure of littoral mysids on herring (Clupea harengus membras L.) eggs and yolk-sac larvae
2008
The predation potential of littoral mysid shrimps (Mysidacea) on Baltic herring (Clupea harengus membras L.) eggs and yolk-sac larvae was studied experimentally. The results showed that littoral mysids feed actively on both eggs and yolk-sac larvae. It was shown that Neomysis integer preys on eggs, which are not attached to the substrate. Alternative food (yolk-sac larvae or zooplankton) did not decrease feeding rate on eggs. Only gravel as a bottom material lowered the ingestion rate to nearly zero. The largest of the mysid species Praunus flexuosus ate yolk-sac larvae more than other mysids and most efficiently. Mysids switched to feed on eggs when larvae and eggs were offered simultaneou…
Light and Primary Production Shape Bacterial Activity and Community Composition of Aerobic Anoxygenic Phototrophic Bacteria in a Microcosm Experiment
2020
ABSTRACT Phytoplankton is a key component of aquatic microbial communities, and metabolic coupling between phytoplankton and bacteria determines the fate of dissolved organic carbon (DOC). Yet, the impact of primary production on bacterial activity and community composition remains largely unknown, as, for example, in the case of aerobic anoxygenic phototrophic (AAP) bacteria that utilize both phytoplankton-derived DOC and light as energy sources. Here, we studied how reduction of primary production in a natural freshwater community affects the bacterial community composition and its activity, focusing primarily on AAP bacteria. The bacterial respiration rate was the lowest when photosynthe…
Influence of Nutrients and Mixing on the Primary Production and Community Respiration in the Gulf of Riga
1999
Abstract Rates of plankton community production and respiration in relation to wind, solar radiation, biomass and nutrients were measured in the mixed layer during a late spring, a mid-summer and an early autumn situation in the Gulf of Riga. System metabolism was estimated by the in vitro oxygen method and from oxygen mass balance directly in the water. Gross production (GPP) remained fairly stable throughout the investigation periods with a mean of 1.8 g C m−2 day−1 (range: 0.5–3.9 g C m−2 day−1). Community respiration varied from 0.5 to 6.4 g C m−2 day−1 during the two summer studies (the high respiration rates ranging from 3.0 to 10.4 g C m−2 day−1 found during the autumn cruise were pr…
Genetics for Pseudoalteromonas provides tools to manipulate marine bacterial virus PM2
2008
ABSTRACT The genetic manipulation of marine double-stranded DNA (dsDNA) bacteriophage PM2 ( Corticoviridae ) has been limited so far. The isolation of an autonomously replicating DNA element of Pseudoalteromonas haloplanktis TAC125 and construction of a shuttle vector replicating in both Escherichia coli and Pseudoalteromonas enabled us to design a set of conjugative shuttle plasmids encoding tRNA suppressors for amber mutations. Using a host strain carrying a suppressor plasmid allows the introduction and analysis of nonsense mutations in PM2. Here, we describe the isolation and characterization of a suppressor-sensitive PM2 sus2 mutant deficient in the structural protein P10. To infect an…