The nectar report: quantitative review of nectar sugar concentrations offered by bee visited flowers in agricultural and non-agricultural landscapes

There is growing concern that some bee populations are in decline, potentially threatening pollination security in agricultural and non-agricultural landscapes. Among the numerous causes associated with this trend, nutritional stress resulting from a mismatch between bee nutritional needs and plant community provisioning has been suggested as one potential driver. To ease nutritional stress on bee populations in agricultural habitats, agri-environmental protection schemes aim to provide alternative nutritional resources for bee populations during times of need. However, such efforts have focused mainly on quantity (providing flowering plants) and timing (during flower-scarce periods), while largely ignoring the quality of the offered flower resources. In a first step to start addressing this information gap, we have used literature data to compile a comprehensive geographically explicit dataset on nectar quality (i.e., total sugar concentration), offered to bees both within fields (crop and weed species) as well as outside fields (wild species) around the globe. Social bees are particularly sensitive to nectar sugar concentrations, which directly impact calorie influx into the colony and consequently their fitness making it an important resource quality marker. We find that the total nectar sugar concentrations in general do not differ between the three plant communities studied. In contrast we find increased variability in nectar quality in the wild plant community compared to crop and weed community, which is likely explained by the increased phylogenetic diversity in this category of plants. In a second step we explore the influence of local habitat on nectar quality and its variability utilizing a detailed sunflower (Helianthus annuus L.) data set and find that geography has a small, but significant influence on these parameters. In a third step we identify crop groups (genera), which provide sub-optimal nectar resources for bees and suggest high quality alternatives as potential nectar supplements. In the long term this data set could serve as a starting point to systematically collect more quality characteristics of plant provided resources to bees, which ultimately can be utilized by scientist, regulators, NGOs and farmers to improve the flower resources offered to bees. We hope that ultimately this data will help to ease nutritional stress for bee populations and foster a data informed discussion about pollinator conservation in modern agricultural landscapes

Untersuchungen benthischer Organismen im Profundal unter besonderer Berücksichtigung der Sedimentation

Bergtold M. Untersuchungen benthischer Organismen im Profundal unter besonderer Berücksichtigung der Sedimentation. Bielefeld; 2001

Factors influencing the vertical distribution of nematodes in Sediments

Teiwes M, Bergtold M, Traunspurger W. Factors influencing the vertical distribution of nematodes in Sediments. JOURNAL OF FRESHWATER ECOLOGY. 2007;22(3):429-439.The effects of oxygenation of sediment and the presence of macrobenthic organisms (gammarids, tubificids, and chironomid larvae) on the vertical distribution and species segregation of nematodes were studied in laboratory microcosms with freshwater sediment. The abundance of nematodes was positively affected by oxygenation, particularly in the deep sediment layers. Small nematodes increased in the deeper layers of oxygenated treatment. Macrobenthic animals did not influence abundance or vertical distribution of nematodes but had an impact on nematode community structure. The families Tobrilidae and Monhysteridae dominated the community. In the control treatments the monhysterids were abundant, whereas the importance of tobrilids increased in the treatments with macrobenthic animals

Using meiofauna to assess pollutants in freshwater sediments: A microcosm study with cadmium

Brinke M, Ristau K, Bergtold M, et al. Using meiofauna to assess pollutants in freshwater sediments: A microcosm study with cadmium. Environmental Toxicology and Chemistry. 2011;30(2):427-438.The direct and indirect effects of Cd on benthic communities were assessed in a freshwater microcosm study over a period of seven months (218 d). Cadmium was regarded as a model substance to evaluate the usefulness of small-scale laboratory microcosm with microscopic fauna. In particular, effects on the meiofauna community, an ecologically important but rather neglected benthic component, were investigated. In addition, some microfaunal parameters (protozoan abundance and microbial activity) were determined. The sediment was spiked with nominal Cd concentrations of 10, 100, and 1,000 mg/kg dry weight. Because of the strong binding of Cd to sediment particles, measured Cd pore-water concentrations never exceeded 129.5 +/- 40.7 mu g/L. At 1,000 mg/kg dry weight, the abundances of the two dominant meiofauna taxa, nematodes and oligochaetes, were significantly reduced throughout the present study. Regarding nematodes, species of bacterivorous taxa (Daptonema, Eumonhystera) decreased, whereas species of predacious and omnivorous taxa (Mononcluts, Dorylaimus, and Ironus) increased in dominance in microcosms of the highest Cd concentration. Transient effects on microfauna were observed, especially in the first half of the present study, with a reduction in microbial activity and protozoan abundance. However, in microcosms receiving the highest Cd concentration, the abundance of the flagellate Euglena mutabilis increased significantly toward the end of the present study. The results of the present study support the use of small-scale microcosms with natural meiofauna communities as a suitable tool to assess the impact of pollutants in freshwater sediments. Environ. Toxicol. Chem. 2011;30:427-438. (C) 2010 SETA

Drivers and pressures behind insect decline in Central and Western Europe based on long-term monitoring data.

Insect declines have been discussed intensively among experts, policymakers, and the public. Albeit, decreasing trends have been reported for a long time for various regions in Europe and North America, but the controversial discussion over the role of specific drivers and pressures still remains. A reason for these uncertainties lies within the complex networks of inter-dependent biotic and abiotic factors as well as anthropogenic activities that influence habitats, communities, populations, and individual organisms. Many recent publications aim to identify both the extent of the observed declines and potential drivers. With this literature analysis, we provide an overview of the drivers and pressures and their inter-relationships, which were concluded in the scientific literature, using some of the best-studied insect groups as examples. We conducted a detailed literature evaluation of publications on Carabidae (Coleoptera) and Lepidoptera trends with data for at least 6 years in countries of Central and Western Europe, with a focus on agricultural landscapes. From the 82 publications identified as relevant, we extracted all reported trends and classified the respective factors described according to the DPSIR model. Further, we analysed the level of scientific verification (presumed vs correlated vs examined) within these papers for these cited stressors. The extracted trends for both species groups underline the reported overall declining trend. Whether negative or positive trends were reported in the papers, our semi-quantitative analysis shows that changes in insect populations are primarily anthropogenically driven by agriculture, climate change, nature conservation activities, urbanisation, and other anthropogenic activities. Most of the identified pressures were found to act on habitat level, only a fraction attributed to direct effects to the insects. While our analysis gives an overview of existing research concerning abundance and biodiversity trends of carabids and lepidopterans, it also shows gaps in scientific data in this area, in particular in monitoring the pressures along with the monitoring of abundance trends. The scientific basis for assessing biodiversity changes in the landscape is essential to help all stakeholders involved to shape, e.g. agriculture and other human activities, in a more sustainable way, balancing human needs such as food production with conservation of nature

Nematode functional guilds, not trophic groups, reflect shifts in soil food webs and processes in response to interacting global change factors

Soils store ~80% of global terrestrial organic carbon and alterations in fluxes into and out of this pool may interact with ongoing climate change. Belowground food webs drive soil C dynamics, but little is known about their responses to co-occurring global change agents. We investigated open-air experimental grassland communities at ambient and elevated atmospheric CO2 concentration, ambient and enriched nitrogen input, and ambient and reduced summer precipitation to evaluate how these agents interactively affect soil nematodes, which are often used as an indicator group for soil food web structure and soil health. The aim of the study was to elucidate the response of the functional diversity of soil nematodes to changing environmental conditions by using nematode functional guilds and indices as indicators.The results suggest that nematode functional guilds surpass nematode trophic groups as soil indicators, suggesting that more detailed data on nematode community structure is essential to capture functional changes in response to environmental change. For instance, the density of opportunistic fungal feeders increased due to N addition with the response being more pronounced at elevated CO2, whereas densities of sensitive fungal-feeders were increased at ambient N and elevated CO2, illustrating opposing responses within one trophic group. Opportunistic bacterial feeders increased at elevated N, but did not respond to other environmental factors studied. Root-feeding Longidoridae were significantly reduced at elevated CO2 and elevated N compared to ambient conditions, whereas other plant feeders were little affected by the manipulations. Predacious nematodes were less abundant at elevated N, and the Structure Index (which indicates food web structure) suggested reduced top-down forces and simplified soil food webs, although omnivores did not vary significantly. Elevated CO2 buffered the effect of reduced precipitation on the Enrichment Index (which indicates increased resource availability) and the Channel Index (which indicates changes in decomposition channel) probably due to reduced stomatal conductance at elevated CO2. Further, the results suggest that the decomposer community switched from a bacterial-dominated to a fungal-dominated system at elevated N, indicating shifts in the microbial community as well as in the functioning of belowground food webs. Overall, the studied global change agents interactively and differentially affected functional guilds of soil nematodes, suggesting complex changes in soil processes. We highlight that detailed information on the functional guilds of nematodes is likely necessary to fully understand alterations in soil food webs and related processes due to global environmental change