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-The relationship between the number of Paenibacillus larvae larvae spores fed individually to 24-28, 48-52 and 72-76 h old Apis mellifera ligustica larvae and the number of larvae dying from the P. l. larvae infection was investigated as well as the effect of sublethal infection with P. l. larvae on larval development time and adult weight. The larvae were laboratory reared, thus, excluding the influence of nurse bees. The results show that larvae 24-28 h old are most susceptible to infection with P. l. larvae with a clear dose-response relationship (LD 50 = 8.49). Older larvae become more and more resistant to infection with P. l. larvae so that no significant dose-mortality relationship exists in the 48-52 and 72-76 h age groups. Furthermore, a significant negative correlation exists between the development time and emergence weight for the adult bees in both the non-inoculated group and the inoculated group. There was no difference in development time between non-inoculated larvae and those that survived the inoculation. © Inra/DIB/AGIB/Elsevier, Paris Apis mellifera ligustica / American foulbrood / Paenibacillus larvae larvae / LD 50 / in vitro rearing

-Honey bee viruses in Apis mellifera colonies were studied at eight Nordic locations with disparate Varroa jacobsoni infestations. Cloudy wing virus (CWV) was the most prevalent infection in all apiaries irrespective of mite infestation. Detection of CWV was not associated with colony collapse in this study. In one apiary where colonies collapsed, deformed wing virus (DWV) was detected. When certain mite mortality levels were reached in this apiary, both live and dead bee samples were always positive for DWV. However, colonies with low values of mite mortality could also be positive for DWV, and this virus could be detected several weeks before colony death in some cases. In the second apiary with collapsing colonies acute paralysis virus (APV) was detected in a live bee sample from one colony, close to the time of colony collapse. The following viruses were detected for the first time in the respective countries, CWV: Denmark, Norway and Sweden; BQCV: Denmark; DWV: Sweden. © Inra/DIB/AGIB/Elsevier, Paris

-In a honey bee population of 150 colonies, the development of an introduced Varroa destructor mite population was monitored in swarming and non-swarming colonies for two years in a Nordic climate. The results demonstrated a reduced mite population as a result of swarming only for the first swarm season studied. In the second swarm season, there were much higher mite levels (based on debris counts of mites) and fewer colonies swarmed, but there was no significant difference in infestation levels of adult bees in the fall between swarming and non-swarming colonies. This result was interpreted as an effect of host-parasite interactions, where the detrimental influence from the infestation prohibited growth (and swarming) in some colonies, but allowed better mite reproduction opportunities (and swarming) in others. Surprisingly, the mite infestation levels of swarms in the late fall were not significantly different from those of swarming colonies the same year, indicating that swarm survival may be almost as much affected by V. destructor, as intact, swarming colonies. No horizontal mite transfer through robbing was observed. The results suggest that, horizontal mite transfer may not be as important in a Nordic climate where many bee colonies die over winter along with their mites, as it is in warmer climates.Varroa destructor / Apis mellifera / swarming / survival / nordic climate / population dynamics

Abstract. Dissolved CH 4 was measured in the water column at the Boknis Eck (BE) time series station in the Eckernförde Bay (SW Baltic Sea) on a monthly basis from June 2006 to November 2008. The water column at BE was always supersaturated with CH 4 and, therefore, CH 4 was released to the atmosphere throughout the sampling period: the mean CH 4 surface (1 m) saturation at BE was 554±317%. A pulse of enhanced CH 4 emissions occurs when the CH 4 accumulation in the hypoxic bottom layer during summer is terminated in late summer/autumn. We did not detect a straightforward relationship between periods of enhanced CH 4 in the bottom layer and hypoxic events at BE: the sedimentary release of CH 4 seemed to be mainly triggered by sedimenting organic material from phytoplankton blooms. We conclude that future CH 4 emissions from BE will be determined by the intensity of phytoplankton blooms, which in turn will be influenced by eutrophication. However, hypoxic events seem to have only a modulating effect on the enhancement of sedimentary methanogenesis and the subsequent release of CH 4 to the water column.

Abstract. The Boknis Eck (BE) time series station, initiated in 1957, is one of the longest-operated time series stations worldwide. We present the first statistical evaluation of a data set of nine physical, chemical and biological parameters in the period of 1957-2013. In the past three to five decades, all of the measured parameters underwent significant long-term changes. Most striking is an ongoing decline in bottom water oxygen concentration, despite a significant decrease of nutrient and chlorophyll a concentrations. Temperature-enhanced oxygen consumption in the bottom water and a prolongation of the stratification period are discussed as possible reasons for the ongoing oxygen decline despite declining eutrophication. Observations at the BE station were compared with model output of the Kiel Baltic Sea Ice Ocean Model (BSIOM). Reproduced trends were in good agreement with observed trends for temperature and oxygen, but generally the oxygen concentration at the bottom has been overestimated.