科学的挑战--重视成本效益,清洁波罗的海

波罗的海是世界上受人类活动影响最严重的海洋之一,虽然有减少向波罗的海排放营养物质的国际协议,但迄今为止采取的措施,既没有从根本上减少营养物质的排放,也没有促进环境的改善.部分原因可以归咎为缺少有关物理学、生物地球化学和生态特性之间大尺度关系和相互作用的知识,但是还缺少全流域范围的成本效益分析.错误的决策非常危险,例如,执行的减少排放的方案根本没有效果,或远远达不到成本效益.许多学科的研究者正面临着一个共同的挑战开发一个决策支持系统,作为整个波罗的海成本效益分析法的科学基础.研究项目海洋富营养化的研究(MARE)(http∥www.mare.su.se)正致力于这方面的研究.     

从富营养化状态中复原：减少对瑞典四大湖磷输入的经验

自20世纪60年代以来,人们一直在研究随着输入的减少韦特恩湖、维纳恩湖、梅拉伦湖以及哈马伦湖中磷(P)和氮(N)的浓度变化.在前两个水更新速度较慢的深水、贫营养湖中,自70年代以来磷输入的急剧减少只是造成较长一段时间内磷浓度的少量减小.同时在水团中出现了非有机氮的积累现象,本文对这一现象的可能原因进行了探讨.在后两个中等营养到高营养的湖中,哈马伦湖中的两个浅盆地由于沉积物释放的氮而显示出恢复较慢.这两个盆地以及梅拉伦湖中的两个盆地有氮缺乏现象,特别是在磷输入减少之前的数年中、而且表明存在固氮现象.在梅拉伦湖的两个盆地中,湖内磷浓度的恢复与用于湖泊从营养物污染中恢复的IMSA模型相比较预期的要好.在其他的5个湖泊/盆地中,20年之后的叶绿素浓度与那些模拟的情况相比类似.     

Rank-dependent hoarding effort in willow tits (<Emphasis Type="Italic">Parus montanus</Emphasis>): a test of theoretical predictions

Many birds and mammals store energy as hoarded food supplies. A supply of stored food is beneficial during periods when food is scarce, but building up and managing such a supply also entails costs. The optimal number of caches will be reached when the net benefit is at its maximum. If dominants can steal more stored food from subordinates than the other way around, the optimum will differ between these categories. A previous theoretical model of hoarding in groups with dominant and subordinate members produced three testable predictions: (1) hoarders should store more food as anticipated future conditions get worse; (2) subordinate flock members should store more food than dominants; and (3) dominants should increase hoarding relatively more than subordinates as conditions get worse. Here we present a field experiment on willow tits (Parus montanus) designed to test these predictions. We found support for all three. Hoarding increased as conditions got worse, subordinates stored at a higher rate than dominants, and dominants increased their hoarding effort relatively more than subordinates as conditions worsened. These results support the incorporation of information on dominance and food availability into models predicting food storage behaviour.Communciated by J. Dickinson     

Development of a diffusive sampling method for determination of methyl isocyanate in air

A diffusive sampling method for determination of methyl isocyanate in air has been developed. A glass fibre filter impregnated with 1-(2-methoxyphenyl)piperazine in a commercially available diffusive sampling device was used to collect methyl isocyanate and the derivative formed was analysed with LC-MS/MS. The sampling rate was determined to be 15.6 ml min(-1), with a relative standard deviation of 7.3%. The sampler was validated for sampling periods from 15 min to 8 h, for relative humidities from 20% to 80% and for concentrations from I to 46 microg m(-3). A field validation was also made and the diffusive sampling results showed no difference compared to a pumped reference method. The impregnated filters have to be stored apart from the diffusive sampler housing and loaded into the sampler prior to each sampling.     

Preferential allocation of food by magpies Pica pica to great spotted cuckoo Clamator glandarius chicks

Adult magpies Pica pica provide parasitic great spotted cuckoo Clamator glandarius nestlings with a diet very similar to that fed to their own chicks. In both naturally and experimentally parasitized nests, great spotted cuckoo chicks were fed at a higher rate than magpie chicks in the same nest. This preferential allocation of food by magpie parents to great spotted cuckoo chicks is consistent with the supernormal stimulus hypothesis, because this result implies that cuckoo chicks provide stronger stimuli for parental care than host chicks. Great spotted cuckoo chicks receive most of the food brought to the nest by the foster parents, because they exploit a series of stimuli which jointly (or sometimes individually) operate as a supernormal stimulus. This hypothesis predicts that if any stimulus is masked, the efficiency of the cuckoo in eliciting parental care will decrease. Here, we analyze experimentally the effects of two of these stimuli, preferential feeding of large nestlings and of nestlings with conspicuous palatal papillae. Firstly, when we experimentally introduced one medium-sized (7–9 days) cuckoo chick into an unparasitized magpie nest where the largest magpie chick was 12–15 days old, the cuckoo did not receive significantly more food than the average or the largest magpie chick. Secondly, when unparasitized nests were experimentally parasitized with a cuckoo chick that had its gape painted to mimic that of magpie chicks, the parasitic cuckoo received less food than the average magpie chick.     

Chick recognition and acceptance: a weakness in magpies exploited by the parasitic great spotted cuckoo

Hosts of brood parasites have evolved the ability to discriminate non-mimetic and even mimetic eggs, but not non-mimetic chicks. Here we demonstrate that the great spotted cuckoo Clamator glandarius does not provide its magpie Pica pica host with a super-normal stimulus that helps to avoid recognition, because single cuckoo chicks introduced into otherwise unparasitized magpie nests are not fed at a higher frequency than single magpie chicks introduced to parasitized magpie nests. Another series of experiments demonstrated that magpies have the ability to discriminate cuckoo chicks, mainly when these are introduced at the end of the nestling period, and especially when the cuckoo chick together with a magpie chick is presented to adult magpies outside the nest. This supports the idea that cuckoos exploit the obligatory reaction of magpies to feed all young that have been hatched in their nests and whose signatures they have learnt. Furthermore, the experimental cuckoo chicks in parasitized magpie nests were more likely to be accepted than they were in non-parasitized nests. This supports the hypothesis that magpies may learn to recognise their own nestlings as those present in the nest and may indicate that a comparison between cuckoo and magpie nestlings is the basis of discrimination.     

Models for waste life cycle assessment: Review of technical assumptions

A number of waste life cycle assessment (LCA) models have been gradually developed since the early 1990s, in a number of countries, usually independently from each other. Large discrepancies in results have been observed among different waste LCA models, although it has also been shown that results from different LCA studies can be consistent. This paper is an attempt to identify, review and analyse methodologies and technical assumptions used in various parts of selected waste LCA models. Several criteria were identified, which could have significant impacts on the results, such as the functional unit, system boundaries, waste composition and energy modelling. The modelling assumptions of waste management processes, ranging from collection, transportation, intermediate facilities, recycling, thermal treatment, biological treatment, and landfilling, are obviously critical when comparing waste LCA models.This review infers that some of the differences in waste LCA models are inherent to the time they were developed. It is expected that models developed later, benefit from past modelling assumptions and knowledge and issues. Models developed in different countries furthermore rely on geographic specificities that have an impact on the results of waste LCA models. The review concludes that more effort should be employed to harmonise and validate non-geographic assumptions to strengthen waste LCA modelling.     

Food or sex—males and females in a sex role reversed pipefish have different interests

In a sex role reversed pipefish, Syngnathus typhle, we found that basic life history allocations were directly influenced by sexual selection. We investigated time allocation to foraging and mating, respectively, in a choice experiment, giving males and females, of small or large body size, a choice between food and a potential partner. We found that males were more interested in foraging than mating, i.e., were more frequently observed in front of the food than in front of the partner, whereas females were more interested in the potential partner. This reflects sexual selection operating differently on the two sexes, as males and females are relatively similar in other life history traits, such as growth, mortality, age of maturity, dispersal, and parental expenditure. Moreover, large individuals allocated more time to mating activities, small to feeding. Individuals more interested in mating compared to food were subsequently more critical when given a choice between a large (high-quality) and a small (low-quality) partner, whereas individuals more interested in food were not selective. These findings are consistent with our predictions: sex-role reversed males can be relatively sure of achieving one or more matings, and should allocate more time to feeding and, hence, to parental investment, growth and/or future reproduction. Females, on the other hand, have more uncertain mating prospects and should allocate time to imminent reproductive activities, thereby foregoing other life history traits such as growth and future egg production. By this, they also sacrifice future fecundity and attractiveness.     

The selective advantage of host feminization: a case study of the green crab Carcinus maenas and the parasitic barnacle Sacculina carcini

Male crabs infected by parasitic barnacles (Rhizocephala) are known to be morphologically feminized. Here, we investigate morphological chances in green crabs, Carcinus maenas, induced by the parasitic barnacle Sacculina carcini. Infected males acquire a broader, longer and segmented abdomen, fringed with marginal setae. Copulatory appendages and pereopods are reduced in length, and the chelae become smaller. The feminization show great individual variation. Males with scars from lost externae, the parasites reproductive organ situated under the abdomen, are less modified than males carrying an externa, and the feminization is more pronounced in smaller than in larger males. No super-feminization is evident in female crabs that remain morphologically unaffected by infection. The protective value of a parasitically induced enlargement of the male abdomen may constitute an adaptation that increases parasite longevity. The additional effects on male morphology are viewed as pleiotropic side effects of the main adaptive value of enlarging the abdomen.