Seasonal patterns and interannual variability of phytoplankton in Lake Stechlin

The paper presents results of detailed phytoplankton investigations in Lake Stechlin between 1994 and 2003. The analysis includes the picoplankton fraction (dominated by Cyanobium sp.) that regularly appears as a deep-layer chlorophyll maximum (DCM). Planktothrix and Aulacoseira are successful competitors against Cyanobium in the isothermal period, the consequences differ markedly due to the fact that Planktothrix is able and Aulacoseira is unable to accumulate in the DCM after the onset of thermocline. The „regular-Cyanobium” and „irregular-Planktothrix, -Aulacoseira” patterns of DCM development has a basic influence on ecosystem functioning. Lake Stechlin a pristine, oligo-mesotrophic deep lake, with an established and detailed monitoring system and thus has been an ideal reference site for studying the influence of global climate changes on plankton that may improve our predictive tools for impact assessment

Peter F.M. Coesel, Koos J. Meesters. Desmids of the Lowlands—Mesotaeniaceae and Desmidiaceae of the European Lowlands. KNNV Publishing, Zeist, The Netherlands (2007). 351 pp., 123 plates, 20 figures in the text and one CD-ROM with extra information, 89.95 €, ISBN: 978-90-5011-265-9

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Comparative proteomics of the two T. brucei PABPs suggests that PABP2 controls bulk mRNA

<div><p>Poly(A)-binding proteins (PABPs) regulate mRNA fate by controlling stability and translation through interactions with both the poly(A) tail and eIF4F complex. Many organisms have several paralogs of PABPs and eIF4F complex components and it is likely that different eIF4F/PABP complex combinations regulate distinct sets of mRNAs. Trypanosomes have five eIF4G paralogs, six of eIF4E and two PABPs, PABP1 and PABP2. Under starvation, polysomes dissociate and the majority of mRNAs, most translation initiation factors and PABP2 reversibly localise to starvation stress granules. To understand this more broadly we identified a protein interaction cohort for both <i>T</i>. <i>brucei</i> PABPs by cryo-mill/affinity purification-mass spectrometry. PABP1 very specifically interacts with the previously identified interactors eIF4E4 and eIF4G3 and few others. In contrast PABP2 is promiscuous, with a larger set of interactors including most translation initiation factors and most prominently eIF4G1, with its two partners TbG1-IP and TbG1-IP2. Only RBP23 was specific to PABP1, whilst 14 RNA-binding proteins were exclusively immunoprecipitated with PABP2. Significantly, PABP1 and associated proteins are largely excluded from starvation stress granules, but PABP2 and most interactors translocate to granules on starvation. We suggest that PABP1 regulates a small subpopulation of mainly small-sized mRNAs, as it interacts with a small and distinct set of proteins unable to enter the dominant pathway into starvation stress granules and localises preferentially to a subfraction of small polysomes. By contrast PABP2 likely regulates bulk mRNA translation, as it interacts with a wide range of proteins, enters stress granules and distributes over the full range of polysomes.</p></div

Magma genesis by rifting of oceanic lithosphere above anomalous mantle: Terceira Rift, Azores

[1] The Terceira Rift formed relatively recently (∼1 Ma ago) by rifting of the old oceanic lithosphere of the Azores Plateau and is currently spreading at a rate of 2–4mm/a. Together with the Mid-Atlantic Ridge, the Terceira Rift forms a triple junction that separates the Eurasian, African, and American Plates. Four volcanic systems (São Miguel, João de Castro, Terceira, Graciosa), three of which are islands, are distinguished along the axis and are separated by deep avolcanic basins similar to other ultraslow spreading centers. The major element, trace element and Sr-Nd-Pb isotope geochemistry of submarine and subaerial lavas display large along-axis variations. Major and trace element modeling suggests melting in the garnet stability field at smaller degrees of partial melting at the easternmost volcanic system (São Miguel) compared to the central and western volcanoes, which appear to be characterized by slightly higher melting degrees in the spinel/garnet transition zone. The degrees of partial melting at the Terceira Rift are slightly lower than at other ultraslow mid-ocean ridge spreading axes (Southwest Indian Ridge, Gakkel Ridge) and occur at greater depths as a result of the melting anomaly beneath the Azores. The combined interaction of a high obliquity, very slow spreading rates, and a thick preexisting lithosphere along the axis probably prevents the formation and eruption of larger amounts of melt along the Terceira Rift. However, the presence of ocean islands requires a relatively stable melting anomaly over relatively long periods of time. The trace element and Sr-Nd-Pb isotopes display individual binary mixing arrays for each volcanic system and thus provide additional evidence for focused magmatism with no (or very limited) melt or source interaction between the volcanic systems. The westernmost mantle sources beneath Graciosa and the most radiogenic lavas from the neighboring Mid-Atlantic Ridge suggest a mantle flow from Graciosa toward the Mid-Atlantic Ridge and hence a flux of mantle material from one spreading axis into the other. The Terceira Rift represents a unique oceanic rift system situated within the thickened, relatively old oceanic lithosphere and thus exhibits both oceanic and continental features

Zur Flora coccaler Grünalgen im Phytoplankton des Naturschutzgebietes Cösitzer Teich (Kreis Köthen, Bezirk Halle)

Die Hercynia publiziert Originalbeiträge mit dem Schwerpunkt Ökologie (mit ihren vielseitigen Aspekten der Biodiversität), Botanik, Zoologie, Geologie und Geografie, den anwendungsorientierten Bereichen des Natur- und Umweltschutzes, sowie der Land- und Forstwirtschaft

Zur Flora coccaler Grünalgen im Phytoplankton einiger Flachgewässer des Micheln-Trebbichauer Teichgebietes (Kreis Köthen, Bezirk Halle)

Die Hercynia publiziert Originalbeiträge mit dem Schwerpunkt Ökologie (mit ihren vielseitigen Aspekten der Biodiversität), Botanik, Zoologie, Geologie und Geografie, den anwendungsorientierten Bereichen des Natur- und Umweltschutzes, sowie der Land- und Forstwirtschaft

Zur Flora coccaler Grünalgen im Phytoplankton einiger Gewässer des Biosphärenreservates Steckby-Lödderitzer Forst (Kreis Schönebeck, Bez. Magdeburg)

Die Hercynia publiziert Originalbeiträge mit dem Schwerpunkt Ökologie (mit ihren vielseitigen Aspekten der Biodiversität), Botanik, Zoologie, Geologie und Geografie, den anwendungsorientierten Bereichen des Natur- und Umweltschutzes, sowie der Land- und Forstwirtschaft

Sinking properties of some phytoplankton shapes and the relation of form resistance to morphological diversity of plankton – an experimental study

Form resistance (Phi) is a dimensionless number expressing how much slower or faster a particle of any form sinks in a fluid medium than the sphere of equivalent volume. Form resistance factors of PVC models of phytoplankton sinking in glycerin were measured in a large aquarium (0.6 x 0.6 x 0.95 m). For cylindrical forms, a positive relationship was found between Phi and length/ width ratio. Coiling decreased Phi in filamentous forms. Form resistance of Asterionella colonies increased from single cells up to 6-celled colonies than remained nearly constant. For Fragilaria crotonensis chains, no such upper limit to Phi was observed in chains of up to 20 cells ( longer ones were not measured). The effect of symmetry on Phi was tested in 1 - 6-celled Asterionella colonies, having variable angles between the cells, and in Tetrastrum staurogeniaeforme coenobia, having different spine arrangements. In all cases, symmetric forms had considerably higher form resistance than asymmetric ones. However, for Pediastrum coenobia with symmetric/asymmetric fenestration, no difference was observed with respect to symmetry. Increasing number and length of spines on Tetrastrum coenobia substantially increased Phi. For a series of Staurastrum forms, a significant positive correlation was found between arm-length/cell-width ratio and Phi: protuberances increased form resistance. Flagellates (Rhodomonas, Gymnodinium) had a Phi 1. The highest value ( Phi = 8.1) was established for a 20-celled Fragilaria crotonensis chain. Possible origin of the so-called 'vital component' ( a factor that shows how much slower viable populations sink than morphologically similar senescent or dead ones) is discussed, as is the role of form resistance in evolution of high diversity of plankton morphologies