Direct male-male competition can facilitate invasion of new colour types in Lake Victoria cichlids

The possibility that disruptive sexual selection alone can cause sympatric speciation is currently a subject of much debate. The initial difficulty for new and rare ornament phenotypes to invade a population, and the stabilisation of the resulting polymorphism in trait and preference make this hypothesis problematic. Recent theoretical work indicates that the invasion is facilitated if males with the new phenotype have an initial advantage in male-male competition. We studied a pair of sympatric incipient species of cichlids from Lake Victoria, in which the red (Pundamilia nyererei) and blue males (P. pundamilia) vigorously defend territories. Other studies suggested that red phenotypes may have repeatedly invaded blue populations in independent episodes of speciation. We hypothesised that red coloration confers an advantage in male-male competition, assisting red phenotypes to invade. To test this hypothesis, we staged contests between red and blue males from a population where the phenotypes are interbreeding morphs or incipient species. We staged contests under both white and green light condition. Green light effectively masks the difference between red and blue coloration. Red males dominated blue males under white light, but their competitive advantage was significantly diminished under green light. Contests were shorter when colour differences were visible. Experience of blue males with red males did not affect the outcome of a contest. The advantage of red over blue in combats may assist the red phenotype to invade blue populations. The apparently stable co-existence of red and blue incipient species in many populations of Lake Victoria cichlids is discussed.Communicated by C. St. Mary     

Great cormorants (<Emphasis Type="Italic">Phalacrocorax carbo</Emphasis>) can detect auditory cues while diving

In-air hearing in birds has been thoroughly investigated. Sound provides birds with auditory information for species and individual recognition from their complex vocalizations, as well as cues while foraging and for avoiding predators. Some 10% of existing species of birds obtain their food under the water surface. Whether some of these birds make use of acoustic cues while underwater is unknown. An interesting species in this respect is the great cormorant (Phalacrocorax carbo), being one of the most effective marine predators and relying on the aquatic environment for food year round. Here, its underwater hearing abilities were investigated using psychophysics, where the bird learned to detect the presence or absence of a tone while submerged. The greatest sensitivity was found at 2 kHz, with an underwater hearing threshold of 71 dB re 1 μPa rms. The great cormorant is better at hearing underwater than expected, and the hearing thresholds are comparable to seals and toothed whales in the frequency band 1–4 kHz. This opens up the possibility of cormorants and other aquatic birds having special adaptations for underwater hearing and making use of underwater acoustic cues from, e.g., conspecifics, their surroundings, as well as prey and predators.     

Responses to accidents in different industrial sectors

Accidents produce external pressures on companies leading to new regulations and renegotiation of enforcement of regulations. Our perspective is institutional with a focus on the extended dialogue among regulators and the industry. The empirical focus is offshore oil and gas production, deep sea and coastal fisheries, and maritime transportation with a segment of older bulk carriers. The findings are that structural characteristics of both the industries and the regulatory regime determine the interactions between the regulated and the regulator. The paper illustrates that in industrial sectors where hazards and risks are visible and of public interest, it is easier to implement regulations through outside pressure from regulators and other stakeholders such as internationally organised unions.     

Assessment of long-term pH developments in leachate from waste incineration residues.

Environmental assessment of residue disposal needs to account for long-term changes in leaching conditions. Leaching of heavy metals from incineration residues are highly affected by the leachate pH; the overall environmental consequences of disposing of these residues are therefore greatly influenced by changes in pH over time. The paper presents an approach for assessing pH changes in leachate from municipal solid waste incineration (MSWI) air-pollution-control (APC) residues. Residue samples were subjected to a stepwise batch extraction method in order to obtain residue samples at a range of pH values (similar to common pH-dependence tests), and then on these samples to determine leaching of alkalinity as well as remaining solid phase alkalinity. On a range of APC residues covering various pretreatment and disposal options, this procedure was used to determine leachable and residual alkalinity as a function of pH. Mass balance calculations for typical disposal scenarios were used to provide data on pH as a function of the liquid-to-solid (L/S) ratio in the leaching system. Regardless of residue type and pretreatment, pH was found to stay above 7 for L/S ratios up to about 2000 L kg(-1) corresponding to about 100,000 years in typical landfill scenarios. It was found that pH changes were mainly governed by alkalinity decreases from leaching processes rather than neutralization reactions. The results suggest that leaching testing for assessment purposes should be carried out in the alkaline range, for example, at pH 9. The paper offers a thorough basis for further modelling of incineration residue leaching and for modelling the environmental consequences of landfilling and utilization of these residues.     

Time and moisture effects on total and bioavailable copper in soil water extracts

Environmental risk assessment of heavy metals in soil frequently involves testing of freshly spiked soils kept under stable humidity conditions, but it has been questioned whether these assessments are representative of the field situation. Furthermore, the poor correspondence that is often found between total metal content and metal toxicity calls for integrated chemical and biological analysis. The aim of this work was to determine time- and moisture-dependent changes in total water-extractable Cu as well as bioavailable Cu in soil water extracts. Measurements of total water-extractable copper ([Cu]tot) were performed using furnace atomic absorption spectrometry. An in vitro assay employing a Cu-specific Pseudomonas fluorescens reporter strain was used to estimate Cu that was biologically available to the reporter strain. We refer to this copper fraction as "bioavailable," [Cu]bio. We found a time-dependent decrease in [Cu]tot and [Cu]bio during incubation for up to 220 d at field capacity. Hence the [Cu]bio was reduced to between 32 and 40% of the initial values. Furthermore, the [Cu]bio to [Cu]tot ratio correlated positively with the amount of added Cu and tended to increase with time. The moisture content of the soil was important for Cu retention. Dry soil had higher [Cu]tot concentrations than humid soil, but the [Cu]bio to [Cu]tot, ratio was lower in the dry soil. Alternating drying and wetting did not lead to a more rapid Cu retention than observed under constant humid conditions. Our observations underline the need for considering both time and moisture effects when interpreting short-term toxicity studies and when making predictions concerning possible long-term effects of Cu in the soil environment.     

Numerical dating of the Eckfeld maar fossil site, Eifel, Germany: a calibration mark for the Eocene time scale

 Sediments of the Eckfeld maar (Eifel, Germany) bear a well-preserved Eocene fauna and flora. Biostratigraphically, Eckfeld corresponds to the Middle Eocene mammal reference level MP (Mammals Paleogene) 13 of the ELMA (European Land Mammal Age) Geiseltalian. In the maar crater, basalt fragments were drilled, representing explosion crater eruption products. By ⁴⁰Ar/³⁹Ar dating of the basalt, for the first time a direct numerical calibration mark for an Eocene European mammal locality has been established. The Eckfeld basalt inverse isochron date of 44.3±0.4 Ma suggests an age for the Geiseltalian/Robiacian boundary at 44 Ma and, together with the 1995 time scale of Berggren et al., a time span ranging from 49 to 44 Ma for the Geiseltalian and from 44 to 37 Ma for the Robiacian, respectively. Additional ⁴⁰Ar/³⁹Ar dating on a genetically related basalt occurrence close to the maar confirms a period of volcanism of ca. 0.6 m.y. in the Eckfeld area, matching the oldest Eocene volcanic activity of the Hocheifel volcanic field. Received: 27 December 1999 / Accepted in revised form: 6 April 2000