Intraspecific sexual selection on a speciation trait, male coloration, in the Lake Victoria cichlid <I>Pundamilia nyererei</I>
The haplochromine cichlids of Lake Victoria constitute a classical example of explosive speciation. Extensive intra- and interspecific variation in male nuptial coloration and female mating preferences, in the absence of postzygotic isolation between species, has inspired the hypothesis that sexual selection has been a driving force in the origin of this species flock. This hypothesis rests on the premise that the phenotypic traits that underlie behavioural reproductive isolation between sister species diverged under sexual selection within a species. We test this premise in a Lake Victoria cichlid, by using laboratory experiments and field observations. We report that a male colour trait, which has previously been shown to be important for behavioural reproductive isolation between this species and a close relative, is under directional sexual selection by female mate choice within this species. This is consistent with the hypothesis that female choice has driven the divergence in male coloration between the two species. We also find that male territoriality is vital for male reproductive success and that multiple mating by females is common.
Fish habitat requirements as the basis for rehabilitation of eutrophic lakes by oxygenation
Eutrophic lakes often suffer from hypolimnetic oxygen depletion during summer and autumn, and the accumulation of reduced substances in the hypolimnion. The space fish can occupy is therefore reduced, and the potential for fish kills caused by toxic algae and the upwelling of anoxic water increases. Fish, such as coregonids, require at least 4 mg O<sub>2</sub> L<sup>−1</sup> to survive in the long-term. This critical level has been postulated as one of the major goals for the rehabilitation of several eutrophic Swiss lakes. It was predicted that this oxygen criterion would reduce phosphorus release from the sediment and increase phosphorus retention, and re-establish natural reproduction of coregonids. Rehabilitation measures applied to three eutrophic Swiss lakes were hypolimnetic oxygenation during summer stratification, and artificial mixing using compressed air to enhance circulation in winter. These lake-internal measures carried out for more than 15 years showed the 4 mg O<sub>2</sub> L<sup>−1</sup> criterion can be achieved most of the time. The measures have led to an expansion of habitat for oxygen-dependent organisms to greater depths. However, other goals were not attained, such as increasing phosphorus retention by the sediment. In addition, natural reproduction of coregonids could not be re-established. Excessive oxygen consumption by the sediment, arising from the decomposition of deposited organic matter produced during summer, caused death by suffocation of coregonid eggs developing on the sediment. Thus rehabilitation of eutrophic lakes by oxygenating the hypolimnion and artificial mixing will not be successful, unless it is accompanied by lowering the nutrient loading and thus primary production and oxygen consumption by the sediment. Nevertheless, positive effects of lake aeration were the expansion of living space for fish and benthic invertebrates, and the prevention of fish kills by upwelling anoxic hypolimnetic water.
Elimination von Kupfer aus Regenwasser durch Adsorption
Die Abtrennung der Oberflächenabflüsse von der Mischkanalisation weist zweifellos Vorteile auf. Allerdings gilt es auch die heute erkannten, problematischen Auswirkungen zu berücksichtigen. Um den Eintrag von unerwünschten Materialien, namentlich von Metallen, in die Versickerungsanlagen, Gewässer und Sedimente zu vermeiden, sind Massnahmen an der Quelle (source control) am wichtigsten. Wenn diese nicht möglich sind, können Barrierensysteme in Form von Adsorber-Anlagen auf der Basis von granuliertem Eisenhydroxid (GEH) die Umweltbelastung verringern.
The case study «Möhlinbach» deals with the conceptual planning of stormwater management in the Möhlintal situated in canton Aargau. It was carried out by local engineering companies, the cantonal authorities and the Urban Drainage Association Möhlintal, consisting of the communities of Möhlin, Zeiningen, Zuzgen, Hellikon, and Wegenstetten. The purpose of this case study was to test out the new planning procedure developed in the project «STORM».
The bases and literature review for conceptual planning and realization of technical solutions related with wet-weather discharges are presented in this paper. Special attention applies for combined sewer overflows. The future technical measures are based on redefined water protection requirements , which can be achieved, at optimal costs, usually only with a combination of different technical measures. A substantially large spectrum of technical possibilities, with costs and efficiency evaluation, are presented in this paper. This document contributes as a help for the choice of technical solutions in the future.
REBEKA II - Software zur Unterstützung der Massnahmenplanung
The software REBEKA was originally developed to estimate the impact of combined sewer overflows and stormwater discharges on receiving waters and to test measures with respect to reduce the impairments. It is widely used for the SWISS Master Plan of Urban Drainage (GEP). One aspect of the project «STORM» is to extend this software by implementing a stochastic routine. This enables it to handle uncertainties in model parameters and to quantify their impact on the results. The enhanced stochastic version, REBEKA II, is presented in this paper. This version handles, in addition to parameter uncertainties, impacts by total suspended solids.
Waste water discharges from sewers during wet weather, especially combined sewer overflows, contain a high concentration of faecal pollutants. Possibly also pathogens like bacteria, protozoan, and viruses, which can lead to hygienic problems in the waterbodies and a constricted use for recreational purposes. So far, this aspect has not been taken into account in the planning and evaluating process of protective measures. Therefore, this paper is dedicated to the relevance of hygienic problems, the causes, the requirements for water quality, results of examinations, the planning procedure, and possible measures.
Temperaturveränderungen im Gewässer bei Regenwetter
A sudden temperature increase due to urban stormwater discharges in receiving waters can be detrimental for aquatic organisms. Is this a real problem for our environment? How important is the initial temperature increase during a rain event? These questions will be discussed in this article. In addition to the definition of limiting values, a simple approach for runoff temperature estimation is presented. Various examples in Switzerland for different impervious surfaces are illustrated.
Modélisation des matières en suspension (MES). Dans les rejets urbains en temps de pluie
Total suspended solids (TSS) play an essential role in the urban wet-weather discharges, as many pollutants, in particular heavy metals, are in adsorbed form on these TSS. Within the framework of project STORM, a model of simulation of the behaviour of TSS was developed and is presented in this article. This model allows a risk evaluation of TSS for the receiving waters and also helps engineers to deal with the environmental problems related with particles.
A phenomenological study of the long-term cosmic ray modulation, 850–1958 AD
The modulation of the galactic cosmic radiation over the past 1150 years is investigated using <sup>10</sup>Be data from Greenland and the South Pole. For this purpose, we introduce the use of 22-year averages to study the long-term modulation. After allowance for secular changes in the geomagnetic dipole, it is shown that the 22-year mean intensity of the galactic cosmic radiation (GCR) in the vicinity of 1–2 GeV/nucleon returned to approximately the same high level at the widely separated times of the Oort (1050 AD), Spoerer (1420–1540), and the latter portion of the Maunder (1645–1715) periods of low solar activity. In terms of the modulation potential, ϕ, this asymptotic intensity corresponds to a mean residual modulation of ∼84 MV. The GCR intensity was significantly less during the Wolf (∼1320) and Dalton (1810) minima, and ϕ ∼ 200 MV. The higher temporal resolution data from Greenland shows that there were large 11-year and other fluctuations superimposed upon these high intensities during the Spoerer and Maunder minima (Δϕ ≈ 200–300 MV), indicating the continued presence of a substantial and time-dependent heliomagnetic field. Throughout the Spoerer minimum, the GCR intensity repeatedly returned to a condition of very low modulation, indicating that the cosmic ray spectrum incident on the Earth approached the level of the local interstellar spectrum. These results imply the continued presence of either (or both) (1) the normal cyclic variation of the heliospheric current sheet and/or (2) a cyclic variation of the diffusion coefficients throughout these periods of low solar activity. The data indicate that the modulation (i.e., depression) of the cosmic ray intensity during the instrumental era (1933–present) has been one of the greatest in the past 1150 years. Further, approximately the same low value has been attained on five previous widely separated occasions since 850 AD, and we speculate that the heliospheric magnetic field has reached an asymptotic limit at those times<em>.</em> The <sup>10</sup>Be data exhibit a previously unrecognized feature, which we have named “the precipitous decrease,” in which the 1–2 GeV/nucleon intensity decreased by ∼40–45% between 1700 and 1739 corresponding to Δϕ > 500 MV, at a time of low but increasing solar activity. A lower cosmic ray intensity than that attained in 1739 was not observed again until after 1950, at a time of high solar activity. These features and the large 11-year modulation events during the Spoerer and Maunder minima indicate that the long-term variations in the GCR intensity are poorly related to sunspot number during epochs of low solar activity. It is shown that there is better agreement between the variations in the <sup>10</sup>Be data, and the changes in the open solar magnetic flux predicted by the <em>Schrijver et al.</em>  and <em>Solanki et al.</em>  models based on historic sunspot numbers. In particular, they both exhibit characteristics consistent with the precipitous decrease in the <sup>10</sup>Be data, although the amplitudes are smaller than implied by the <sup>10</sup>Be data.