Insektizid-Auswirkungen auf Fließgewässer-Lebensgemeinschaften

Event-triggered sampling from a stream in agricultural terrain has revealed a level of contamination considerably higher than that which has generally been assumed, although only moderate amounts of insecticides had been washed away from the cultivated fields. Macroinvertebrate sampling carried out in parallel with the contamination measurements documented severe negative effects of the insecticide inputs on the aquatic community; 8 of the 11 species disappeared from the water for a period of 3 to 6 months. In field investigations, as well as inin situ bioassays,L. lunatus andG. pulex exhibited acute responses (drifting, mortality during drifting) which were seen to be significantly higher than those values noted at an uncontaminated control site as far as even 2000 m from the input site. In these bioassays, where the animals are confined in cages, the insecticide toxicity inG. pulex may be overestimated compared to the field data since the drifting behavior of this species normally helps it to avoid contamination.     

气候变暖期间波罗的海海冰的模拟分布及对环斑海豹冬季栖息地的影响

本文调查研究了在目前和未来气候条件下的波罗的海海冰.采用了罗斯比区域大气-海洋模型进行了一系列为时30年的时间片试验.对于两个驱动全球模型HadAM3H和ECHAM4/OPYC3中每一个,都根据SRESA2和B2辐射情景进行一次对照操作(1961～1990年)和两次情景操作(2071～2100年).波罗的海中未来海冰量将平均减少83%.波的尼亚海,芬兰湾和里加湾的大片海域以及芬兰西南群岛的外部将基本上变成无冰区.本文提出的情景是用来研究气候变化对波罗的海环斑海豹(Phoca hispida botnica)的影响.气候变化看来是对所有南方种群的主要威胁.惟一还算不错的冬季海冰生境只限于波的尼亚湾.     

波罗的海高盐传送带,或波罗的海中的翻转环流及咸、淡水的混合

我们使用三维波罗的海模型模拟的做法进行了一项波罗的海水团环流的研究.来自北大西洋的咸水经丹麦海峡流入波罗的海,在波罗的海上涌并与从各河流流入的淡水混合形成"波罗的海高盐传送带".我们利用翻转流量函数和拉格朗日轨迹线对来自大贝尔特和厄勒海峡的成水与淡水的混合情况进行了调查.该翻转流量函数被作为一种具有4个不同垂直坐标(深度、盐度、温度和密度)的函数进行计算,以便了解水的路径以及它在什么地方上涌并混合.在波罗的海本体内发现了与南大洋中的迪肯环流(Deacon Cell)类似的虚拟深度翻转环流的存在,它与哥特兰岛附近的旋转环流相符,当翻转流量函数投射在密度层上时,这一虚拟深度翻转环流就消失了.我们已经开展了一项拉格朗日轨迹线研究,以便更好地认识该环流以及咸水与淡水的混合情况.对这些水团在波罗的海中的停留时间的计算结果为26～29年,而拉格朗日扩散在5年后达到海盆饱和.     

The phylogeny of archaebacteria,including novel anaerobic thermoacidophiles in the light of RNA polymerase structure

DNA-dependent RNA polymerases of archaebacteria are distinct from those of eubacteria both in structure and in function. They show similarities to those of the eukaryotic cytoplasm. Extremely thermophilic anaerobic sulfur-respiring archaebacteria isolated from solfataric waters represent four different families, the Thermoproteaceae, the “stiff filaments”, the Desulfurococcaceae and the Thermococcaceae, of a novel order, Thermoproteales. Together with the Sulfolobales, they form the second branch of the urkingdom of the archaebacteria besides that of the methanogens and extreme halophiles. Thermoplasma appears isolated.     

Pastoralists' responses to variation of rangeland resources in time and space.

We explore the response of pastoralists to rangeland resource variation in time and space, focusing on regions where high variation makes it unlikely that an economically viable herd can be maintained on a single management unit. In such regions, the need to move stock to find forage in at least some years has led to the evolution of nomadism and transhumance, and reciprocal grazing agreements among the holders of common-property rangeland. The role of such informal institutions in buffering resource variation is well documented in some Asian and African rangelands, but in societies with formally established private-property regimes, where we focus, such institutions have received little attention. We examine agistment networks, which play an important role in buffering resource variation in modern-day Australia. Agistment is a commercial arrangement between pastoralists who have less forage than they believe they require and pastoralists who believe they have more. Agistment facilitates the movement of livestock via a network based largely on trust. We are concerned exclusively with the link between the characteristics of biophysical variation and human aspects of agistment networks, and we developed a model to test the hypothesis that such a link could exist. Our model builds on game theory literature, which explains cooperation between strangers based on the ability of players to learn whom they can trust. Our game is played on a highly stylized landscape that allows us to control and isolate the degree of spatial variation and spatial covariation. We found that agistment networks are more effective where spatial variation in resource availability is high, and generally more effective when spatial covariation is low. Policy design that seeks to work with existing social networks in rangelands has potential, but this potential varies depending on localized characteristics of the biophysical variability.     

Evenly dispersed social groups and intergroup competition for juveniles in a coral-reef fish

Summary A model based on current knowledge of recruitment of settling juveniles of coral-reef fishes suggests that adult social groups far removed from their nearest neighbors can expect to attract larger numbers of juveniles than groups that are close to nearest neighbors. For protogynous fishes in which females change to males when intragroup, female-to-male sex ratios rise above threshold values, selection should favor individuals occupying groups that attract many juveniles. The model predicts that social groups should, in consequence, be regularly dispersed and that, in effect, groups compete with each other to attract juveniles. Dispersion of social groups was measured in two populations of the protogynous fish Anthias squamipinnis. The location of all groups were plotted on maps of the reef. A set of nearest-neighbor analyses applied to the data all showed significant departures of observed nearest-neighbor distances from randomness, in the direction of regularity. At both sites, neighboring groups were separated by much unoccupied space. In one population, the substrate consisted of discrete coral aggregates scattered over open sand bottom, while in the second population groups occupied a relatively continuous vertical reef face. Although regular dispersion could, in theory, result from regular distribution of food patches, current evidence does not favor this explanation. It is more likely that regular dispersion results either from the reproductive advantage of occupying groups that are highly attractive to juveniles, as seen in the model, or from limited perceptual and locomotor abilities of juveniles at the time of settlement.     

Climate Science and Climate Policy: Improving the Science/Policy Interface

The development of an international climate policy builds on national policy perspectives. These depend on the perceived risks of climate change, socioeconomic and cultural characteristics of the nations and regions involved, and the technical feasibility of policy measures. Scientific and technological research supports the policy making process about these issues. The perspectives of the scientific community and the policy makers differ and as a consequence communication is often troublesome. The construction and utilization of knowledge under such circumstances can only be effective if all parties involved engage in a continuous dialogue about causes, effects, impacts and responses. This paper describes a project carried out in the Netherlands. It has as its major objective the articulation of a variety of perceptions and positions related to climate change. As a result of the project, policy actors produced five policy options and formulated research questions. The policy options are linked in the framework of a policy life cycle. Research questions focus on the risks of climate change and on feasible social, economic, cultural and technological responses to it. As to the policy options, striving for common means appears to be more promising than pursuing shared goals and philosophies.