Reproductive performance in lesser snow geese: are two parents essential?

Summary The roles of male and female lesser snow geese (Anser caerulescens) in offspring care are well documented, but we know little about flexibility in these roles and how essential they are for offspring survival. We asked whether uni-parental care was adequate, which sex was required at various stages of the reproductive cycle, and what the costs and consequences were of variable amounts of parental care. We found that two parents were important in acquiring nest sites and producing clutches. Widows losing mates during the latter part of laying or in early incubation experienced similar rates of success in hatching clutches to paired females, but males losing mates during incubation experienced total nest failure. Partial clutch loss, hatch loss, intraspecific nest parasitism, duration of incubation periods and gosling weights at hatch did not differ for pairs or widows. In 1983 at La Pérouse Bay, Manitoba, Canada, widows and pairs had similar incubation behaviour, but widows were harassed more and spent more time in full alert posture while on their nests. In 1952 and 1953 at Southhampton Island, Northwest Territories, widows were significantly lighter in body weight prior to hatch than paired females. Thus while widows can bring clutches to hatch successfully, the loss of mates may result in additional physiological costs. Although all possibilities have not been tested experimentally, it appears that costs to uni-parental care up to hatch are not significant. Data collected so far on consequences of uni-parental care provided during the post-hatch period are equivocal, as in one year survival of goslings from single parent broods seemed poor and in another it did not appeart to differ from pairs. The minimum amount of parental care required to raise snow goslings from hatch to recruitment has yet to be determined.     

The effect of wind direction on cross-pollination in wind-pollinated GM crops.

In Europe, regulatory thresholds restrict adventitious GM (genetically modified) presence in conventional crops. Minimum distances for the spatial separation of fields are often recommended to reduce field-to-field cross-pollination to an acceptable level. Field trials are typically the basis for setting separation distances. However, using records of wind direction and speed from weather stations across Europe, we predict theoretically that field-to-field windborne cross-pollination in maize, oilseed rape, sugar beet, and rice varies greatly according to the relative orientation of the GM and non-GM fields. Furthermore, at a given site and orientation from a GM field, we predict that the cross-pollination rate varies substantially from year to year. Consequently, even replicated field trials may inaccurately estimate typical levels of cross-pollination and therefore distort our perception of the separation distances required to achieve sub-threshold adventitious GM presence. We propose methods to predict the likely range in levels of cross-pollination based on the limited data typically available from field trials. Additionally, we suggest suitable time lags between peak flowering in adjacent fields that could be introduced to reduce cross-pollination to a specified level.     

Variability in grazer-mediated defensive responses of green and red macroalgae on the south coast of South Africa

Variabilities in the responses of several South African red and green macroalgae to direct grazing and the responses of one green alga to cues from grazers were tested. We used two feeding experiments: (1) testing the induced responses of three red and one green algae to direct grazing by mesograzers and (2) a multi-treatment experiment, in which the direct and indirect effects of one macrograzer species on the green alga Codium platylobium were assessed. Consumption rates were assessed in feeding assays with intact algal pieces and with agar pellets containing non-polar extracts of the test algae. Defensive responses were induced for intact pieces of Galaxaura diessingiana, but were not induced in pellets, suggesting either morphological defence or chemical defence using polar compounds other than polyphenols. In contrast, exposure to grazing stimulated consumption of Gracilaria capensis and Hypnea spicifera by another grazing species. In the multi-treatment experiment, waterborne cues from both grazing and non-grazing snails induced defensive algal traits in C. platylobium. We suggest that inducible defences among macroalgae are not restricted to brown algae, but that both the responses of algae to grazers and of grazers to the defences of macroalgae are intrinsically variable and complex.     

Enzymatische Umsetzung von Arsenkampfstoffen durch das Pilzenzym Mangan-Peroxidase

Degradation of organo-arsenical chemical warfare agents by fungal enzyme manganese peroxidase. The fungal enzyme manganese peroxidase was used to degrade different organo-arsenical chemical warfare agents in cell-free reaction mixtures (in vitro). The decrease in the concentration of arsenical chemical warfare agents was determined by gas chromatography after derivatization with thiols. All organo-arsenical compounds tested were converted by room temperature for more than 90%. Aliphatic arsenical compounds were attacked more rapidly than aromatic derivatives.     

Achieving environmental standards with stochastic discharges

The inherent stochastic nature of the levels and composition of environmental waste discharges are well known to environmental control agencies, who recognize that realistically environmental quality constraints must be formulated in probabilistic terms. Given the specification of environmental constraints in such terms, it is shown that the set of activity vectors which satisfy the constraint will, in general, be nonconvex. This militates against the determination of an efficient solution. A means of avoiding the potentially high computational and informational costs associated with the determination of an efficient solution in such cases is proposed.     

Effects of temperature on oocyte growth in the Mediterranean terebellid Eupolymnia nuebulosa (Annelida: Polychaeta)

Eupolymnia nebulosa (Montagu) is a widely distributed terebellid polychaete that builds its tubes on the coastal shelf in areas with mixed soft and hard bottoms. From a long-term survey in the Bay of Banyuls, France (NW Mediterranean), we found an advancement of the timing of the spawning period coincident with a delayed breakdown of the thermocline. We postulate that persistent high temperatures can influence gamete development by stimulating oocyte growth, resulting in earlier spawning. During 1992 and 1993, we used a between-individuals experimental approach to assess the possible effect of temperature on oocyte growth based on: (1) determination of the growing fraction of the oocyte population (i.e. oocyte net growth); (2) identification of differences in oocyte growth-rate among females; (3) comparison of non-significantly different size-distributions of the growing oocyte fraction (net oocyte size-distributions) at the beginning of the experiments with those at the end. No effect of temperature on oocyte growth was detectable at the population level, but a positive individual response to prolonged high temperature was evident. Thus, the lack of a significant response by the population to prolonged high temperature does not imply a lack of individual response. We propose a model of oocyte-growth dynamics based on temperature that incorporates previous observations of extended oogenesis and oocyte growth during periods of both increasing and decreasing temperature and on the scattered pattern of oocyte size-distributions at the onset of spawning. Received: 4 November 1996 / Accepted: 18 January 1997     

Aktuelle Entwicklungen bei Umweltindikatorensystemen

The current monitoring of the status of the environment and natural resources is a substantial basis for the implementation of a sustainable development as a model of the environmental policy in the terms of Agenda 21. For the 90s, in particular by the mandate of Rio 1992, both the international institutions (international level), e.g. the OECD, the United Nation Commission of Sustainable Development and the European Environmental Agency, and the environmental protection authorities of the different countries (national level) e.g. Germany, and of the federal states of Germany (regional level) are developing environmental indicator systems. In the context of the Local Agenda 21, indicators for the ecological, economic, social and institutional categories are set up on a communal level. In the environmental indicator systems different issues, e.g. climate change, ozone layer depletion, water quality and water resources, waste, toxic contamination, biodiversity, landscape protection, soil resources, forest resources, etc., are described. Concepts with driving forces, pressure, state, impact and/or response indicators are applied. The German Council of Environmental Advisors (SRU) requires that the selection and aggregation of indicators must be transparent and comprehensibly documented and that the chosen indicators must be oriented at political targets. The following article gives an overview of relevant actual environmental indicator systems, their concepts and structuring, and points to the further research and developmental requirements within this area.     

Radon from drinking water — evaluation of water-borne transfer into house air

To determine the transfer of²²²Rn from domestic water into air, nine houses were measured for²²²Rnt, house volume, water use and air exchange by SF₆ and radon. Measurements were done in Maine during April and May, 1986, when sealed up for the winter. Radon in water concentration ranged from 35,000 to 1,250,000 pCi/l. Air peaks of²²²Rn ranged from 13 to 200 pCi/l due to a water use burst experiment. Use of water filters was also examined by repeats with filters on and off. Water use ranged from 200 to 1922 litres/day. House volumes ranged from 380 to 999 m³. Air exchange rates measured by SF₆ was twice as large as air exchange rate measured by²²²Rn.