The effect of repeated vibration signals on worker behavior in established and newly founded colonies of the honey bee, <Emphasis Type="Italic">Apis mellifera</Emphasis>

Communication signals used in animal social interactions are frequently performed repetitively, but the function of this repetition is often not well understood. We examined the effects of signal repetition by investigating the behavior of worker honey bees that received differing numbers of vibration signals in established and newly founded colonies, which could use signal repetition differently to help adjust task allocations to the labor demands associated with the different stages of colony development. In both colony types, more than half of all monitored workers received more than one vibration signal, and approximately 12% received ≥5 signals during a given 20-min observation period. Vibrated recipients exhibited greater activity and task performance than same-age non-vibrated controls at all levels of signal activity. However, vibrated workers showed similar levels of task performance, movement rates, cell inspection rates, and trophallactic exchanges regardless of the number of signals received. Thus, the repeated performance of vibration signals on individual bees did not cause cumulative increases in the activity of certain workers, but rather may have functioned to maintain relatively constant levels of activity and task performance among groups of recipients. The established and newly founded colonies did not differ in the extent to which individual workers received the different numbers of vibration signals or in the levels of activity stimulated by repeated signals. Previous work has suggested that compared to established colonies, newly founded colonies have a greater number of vibrators that perform signals on a greater proportion of the workers they contact. Taken in concert, these results suggest that vibration signal repetition may help to adjust task allocations to the different stages of colony development by helping to maintain similar levels of activity among a greater total number of recipients, rather than by eliciting cumulative effects that cause certain recipients to work harder than others.     

Adaptation of the ion exchange method for the determination of the free ionic fraction of cadmium in solution

The understanding of the availability of a metal in soil necessitates a minimum knowledge about its speciation in the soil solution. Here, we evaluated an alternative to the use of ion exchangers for estimating the free ionic fraction of cadmium (FCd) in solution. It is based on the exchange selectivity coefficient (VK) rather than the distribution coefficient (DK) to estimate FCd. Because VK for the Cd-Ca exchange for the used Amberlite resin was independent of the solution Ca concentration (0.5-7.5 mM) and pH (range: 4.5-6), the experiment on a solution mimicking the analyzed solution to estimate VK was not necessary. The influence of variable Ca and Mg concentrations in solution on FCd was assessed in synthetic solutions containing either citrate or malate. The best way to estimate FCd seemed to treat the exchange data as if Ca was solely present. However, neither the proposed approach nor those applying DK prevent the overestimation of FCd when Ca is partly complexed in the analyzed solution. A method intending to estimate two replicates of FCd for a given, unique solution was also studied on solutions issued from sorption-desorption experiments performed on a humic podzol. It consists of two successive supplies of a known resin mass to a unique sample. Both estimates were close and not significantly different.     

Immunoassays as high-throughput tools: Monitoring spatial and temporal variations of carbamazepine, caffeine and cetirizine in surface and wastewaters

Carbamazepine (CBZ), caffeine and cetirizine were monitored by enzyme-linked immunosorbent assays (ELISAs) in surface and wastewaters from Berlin, Germany. This fast and cost-efficient method enabled to assess the spatial and temporal variation of these anthropogenic markers in a high-throughput screening. CBZ and cetirizine were detected by the same antibody, which selectively discriminates between both compounds depending on the pH value used in the incubation step. To our best knowledge, this is the first dual-analyte immunoassay working with a single antibody.The frequent sampling with 487 samples being processed allowed for the repeated detection of unusually high concentrations of CBZ and caffeine. ELISA results correlate well with the ones obtained by liquid chromatography tandem mass spectrometry (LC-MS/MS). Caffeine concentrations found in surface waters were elevated by combined sewer overflows after stormwater events. During the hay fever season, the concentrations of the antihistamine drug cetirizine increased in both surface and wastewaters.Caffeine was almost completely removed during wastewater treatment, while CBZ and cetirizine were found to be more persistent. The maximum concentrations of caffeine, CBZ and cetirizine found in influent wastewater by LC-MS/MS were 470, 5.0 and 0.49 μg L⁻¹, while in effluent wastewater the concentrations were 0.22, 4.5 and 0.51 μg L⁻¹, respectively. For surface waters, concentrations up to 3.3, 4.5 and 0.72 μg L⁻¹ were found, respectively.     

Accounting for carbon stocks in models of land-use change: an application to Southern Yucatan

To assess the impact of land-use change on carbon stocks, we apply a new methodology, linking ecological and economic modeling, to southern Yucatan, Mexico. A spatial econometric multinomial logit model of ten land-cover classes is estimated (four primary forest categories, three secondary growth categories, an invasive species, and two agricultural land-cover categories), using satellite data on land cover, linked with census socioeconomic data and other biophysical spatial data from 2000. The analysis is novel in that it is the first attempt to link detailed satellite data on land use, with on-the-ground estimates of carbon stocks in a spatial econometric model of land use. The estimated multinomial logit model is then used with two scenarios of future economic growth (“low growth” and “high growth” changes in population, agricultural land use, market access, and education levels) in the region to predict land-cover changes resulting from the economic growth. The per hectare carbon (C) stocks in each land-cover class are derived from previously published estimates of biomass from field sampling across the study region. We consider aboveground-only, aboveground plus soil, transient and non-transient pools of carbon. These estimates are scaled up to the total area in each class according to the predictions of the model baseline and the two development scenarios. Subsequently, the changes in carbon stocks resulting from the predicted land-cover changes are calculated. Under the low growth scenario, carbon stocks declined by 5%; under the high growth scenario, losses were 12%. Including soil C, the proportional losses were lower, but the absolute amount lost was more than double (to 6 Tg C under the low and almost 15 Tg C under the high-growth scenario). This methodology could be further developed for applications in global change policy, such as payments for environmental services (PES) or reduction in emissions from deforestation and degradation (REDD).