Combination of two indication systems in pre-alpine lakes — diatom index and macrophyte index

Since the climax of eutrophication in the early 1980s mainly greater lakes have been investigated and monitored in terms of their nutrient charge. In the future there will still be a need to develop guidelines for monitoring the trophic status of smaller lakes. Four small lakes were investigated by the author in the years 1996 and 1997. In order to define the nutrient charge of those lakes more precisely, special emphasis has been put upon the two criteria diatoms and macrophytes. Eventually an evaluation of the lakes' catchment areas will also be an important component of these studies. Benthic diatoms are the main part of periphyton. As unicellular fast reproducing organisms they are excellent indicators for trophic situations in lakes. The diatom index denotes the trophic status of the littoral zone during the last few weeks before sampling. The macrophytes, however, reflect the nutrient charge over a longer period, i.e. several years. The macrophyte index is based on the fact that some species are most prevalent at certain nutrient loads. The effort to combine these two indication systems carries a high resolution of spatial nutrient changes as well as in temporally changes.     

Long-term reactions of plants and macroinvertebrates to extreme floods in floodplain grasslands

Extreme summertime flood events are expected to become more frequent in European rivers due to climate change. In temperate areas, where winter floods are common, extreme floods occurring in summer, a period of high physiological activity, may seriously impact floodplain ecosystems. Here we report on the effects of the 2002 extreme summer flood on flora and fauna of the riverine grasslands of the Middle Elbe (Germany), comparing pre- and post-flooding data collected by identical methods. Plants, mollusks, and carabid beetles differed considerably in their response in terms of abundance and diversity. Plants and mollusks, displaying morphological and behavioral adaptations to flooding, showed higher survival rates than the carabid beetles, the adaptation strategies of which were mainly linked to life history. Our results illustrate the complexity of responses of floodplain organisms to extreme flood events. They demonstrate that the efficiency of resistance and resilience strategies is widely dependent on the mode of adaptation.     

Critical Loads Exceedances in Germany and their Dependence on the Scale of Input Data

Critical load exceedances have been used as an effects-related parameter for guiding international air emission control negotiations. High-resolution critical load data are combined with low-resolution deposition data.This article shows that doing so systematicallyunderestimates `true' critical load exceedances as obtainedfrom combining critical load and deposition data of identicalhigh spatial resolution. 95th percentile critical loadexceedances in EMEP grids based on high resolution depositiondata are 60 and 150% higher (mean values for nutrientnitrogen and acidity, respectively) than critical loadexceedances based on the low resolution EMEP depositionmodel. The latter are used in international negotiations. Differences in individual EMEP grid squares vary betweeninsignificantly different from zero and 340%, depending onregional deposition and critical load characteristics andcritical load types (nutrient nitrogen versus acidity).Exceedances based on high-resolution deposition values arealso compared to EMEP grid averages of these values forforests only. This comparison excludes the effect ofsystematically higher depositions to forests. Still, thescale difference of (averaged, low-resolution) deposition and(high-resolution) critical loads data yields underestimatesof the 95th percentiles by on average ca. 20%.These systematic errors due to the scale dependence should beborne in mind when interpreting effects of internationalemission control measures.     

纳米二氧化钛在老化环境条件下对铜诱导毒性的影响

纳米二氧化钛颗粒(nTiO₂)可以通过吸附表层水中共生重金属来改变它们对淡水无脊椎动物的毒性。然而,影响这种交互过程的几种环境因子的相对重要性仍不清楚。因此,本研究通过连续72 h的培养试验,评估了老化对Cu与nTiO₂对大型蚤Daphnia magna联合急性毒性的影响。在老化过程中,对老化时间以及离子强度、pH值和不同质量有机物质等因子都进行了考察。研究结果表明,尽管影响效应的大小不同,nTiO₂的存在往往减少了老化后Cu对大型蚤的诱发毒性,在没有nTiO₂的情况下,Cu对大型蚤急性毒性的EC₅₀值提高了3倍之多。此外,各种形态Cu的形成受到介质中的离子组成、pH值以及有机添加剂存在的影响,这一过程受到极大的调控,并随着老化时间对大型蚤生态毒性的响应有一定影响。尽管如此,该研究的结论对nTiO₂在淡水生态系统中不同环境条件下,改变重金属诱发毒性的潜在作用提供了有力的支持。然而,这种模式需要进一步验证,比如结合不同性质的重金属离子与不同的环境因素,如紫外线照射。
精选自Ricki R. Rosenfeldt, Frank Seitz, Ann-Cathrin Haigis, Johanna H?ger, Jochen P. Zubrod, Ralf Schulz, Mirco Bundschuh. Nanosized titanium dioxide influences copper induced toxicity during aging as a function of environmental conditions. Environmental Toxicology and Chemistry: Volume 35, Issue 7, pages 1766–1774, July 2016. DOI: 10.1002/etc.3325
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.3325/full
     

Why are metapopulations so rare?

Roughly 40 years after its introduction, the metapopulation concept is central to population ecology. The notion that local populations and their dynamics may be coupled by dispersal is without any doubt of great importance for our understanding of population-level processes. A metapopulation describes a set of subpopulations linked by (rare) dispersal events in a dynamic equilibrium of extinctions and recolonizations. In the large body of literature that has accumulated, the term "metapopulation" is often used in a very broad sense; most of the time it simply implies spatial heterogeneity. A number of reviews have recently addressed this problem and have pointed out that, despite the large and still growing popularity of the metapopulation concept, there are only very few empirical examples that conform with the strict classical metapopulation (CM) definition. In order to understand this discrepancy between theory and observation, we use an individual-based modeling approach that allows us to pinpoint the environmental conditions and the life-history attributes required for the emergence of a CM structure. We find that CM dynamics are restricted to a specific parameter range at the border between spatially structured but completely occupied and globally extinct populations. Considering general life-history attributes, our simulations suggest that CMs are more likely to occur in arthropod species than in (large) vertebrates. Since the specific type of spatial population structure determines conservation concepts, our findings have important implications for conservation biology. Our model suggests that most spatially structured populations are panmictic, patchy, or of mainland-island type, which makes efforts spent on increasing connectivity (e.g., corridors) questionable. If one does observe a true CM structure, this means that the focal metapopulation is on the brink of extinction and that drastic conservation measures are needed.