Comments on a method allowing permanent preparations of phytoplankton for light microscopy and the accurate selection and positioning of its cells for transmission electron microscopy

A new flat embedding method is commented. This method allows embedding of the same phytoplankton sample for light and transmission electron microscopy. Rare or interesting field specimens can then be easily selected and sectioned without the need of cultures. A great range of biological material can be handled with this method.     

Strömungsdynamische Untersuchungen im Zürich- und im Luganersee Ein Vergleich von Feldmessungen mit Resultaten theoretischer Modelle

Density distribution and temperature and current data which were measured in Lake of Zürich and Lake of Lugano in two summer field programs are scrutinized and interpreted by means of hydrodynamic models. Barotropic surface seiches and baroclinic internal seiches are studied using a one-and two-layer model and measured data permit identification of the respective resonant periods. Wind induced barotropic and baroclinic circulation dynamics is also studied by means of three-dimensional finite difference models of the hydrodynamic viscous equations on the rotating earth. In general the predictions of these models agree favorably with observed data.     

Problems in the determination of freshwater dinoflagellates (Dinophyceae)

According to the most recent findings mainly from the life cycles and multiplication of dinoflagellates it is shown that using only the external morphology is not sufficient for the determination of many species nor for the key. Dinoflagellates are characterized by many transient features between protozoa and algae and they cannot be introduced without difficulties.     

Biologische Untersuchung der Limmat zwischen Zürichsee und Wettingen, 1974 bis 1980

Biological investigations of that part of the River Limmat lying between Quaibrücke and Wettingen were carried out from 1974 to 1980. An influence of the waste water from the Werdhölzli sewage treatment plant on the plant and animal communities of the river bed was evident. This influence was especially plain to be seen immediately below the point of introduction of the waste water. The incidence of pollution indicators decreased downriver from this point. Biotests, using periphyton from stones taken from the shore of the Zürichsee, yielded harvests which were clearly higher in Limmat water taken from points downstream from the sewage works than in water taken from points upstream.     

Restoration of submerged vegetation in shallow eutrophic lakes – A guideline and state of the art in Germany

One of the most serious problems caused by eutrophication of shallow lakes is the disappearance of submerged macrophytes and the switch to a turbid, phytoplankton-dominated state. The reduction of external nutrient loads often does not result in a change back to the macrophyte-dominated state because stabilising mechanisms that cause resilience may delay a response. Additional internal lake restoration measures may therefore be needed to decrease the concentration of total phosphorus and increase water clarity. The re-establishment of submerged macrophytes required for a long-term stability of clear water conditions, however, may still fail, or mass developments of tall-growing species may cause nuisance for recreational use. Both cases are often not taken into account when restoration measures are planned in Germany, and existing schemes to reduce eutrophication consider the topic inadequately. Here we develop a step-by-step guideline to assess the chances of submerged macrophyte re-establishment in shallow lakes. We reviewed and rated the existing literature and case studies with special regard on (1) the impact of different internal lake restoration methods on the development of submerged macrophytes, (2) methods for the assessment of natural re-establishment, (3) requirements and methods for artificial support of submerged macrophyte development and (4) management options of macrophyte species diversity and abundance in Germany. This guideline is intended to help lake managers aiming to restore shallow lakes in Germany to critically asses and predict the potential development of submerged vegetation, taking into account the complex factors and interrelations that determine their occurrence, abundance and diversity.     

Consequences of explosive eruptions on small Solar System bodies: the case of the missing basalts on the aubrite parent body

Aubrite meteorites are composed of constituents which are almost certainly of igneous origin. If they were generated by the melting and fractionation of enstatite chondrite-like parental material, as seems very likely, then plagioclase-rich, basaltic complements to the aubrites should have formed. However, such materials are not known as individual meteorites, and the compositions of two plagioclase-silica clasts and one albite-silica-(diopside-anorthite) clast (probably an impact melt) in the Norton County aubrite breccia suggest that they are not the putative enstatite-plagioclase basalts. We propose a new mechanism that explains the absence of these materials, showing that the expansion of even very small amounts of volatiles present in a melt approaching the surface of a small, low-gravity body will be enough to disrupt the melt into a spray of droplets moving faster than the local escape velocity. This explosive volcanic process of melt removal requires larger melt volatile contents on larger bodies, and data on the solubility of volatiles in basaltic melts suggest that the process was limited to bodies smaller than about 100 km in radius.