Live Algae in Deep Sediment Layers

Examination of sediment cores taken from shallow coastal regions of the Baltic showed that some algae were still alive at depths beyond the depth of light penetration. Their cells contained chlorophyll and photosynthesis resumed when they were exposed to light. Photosynthesis was detected by simultaneous measurement of oxygen production and ¹⁴C uptake. Autoradiography was used to detect incorporated ¹⁴C. The autoradiographic method was improved by a few modifications.     

The Effect of Zostera noltii, Spartina maritima and Scirpus maritimus on Sediment Pore-water Profiles in a Temperate Intertidal Estuary

The objective of the present work was to study the effect of plants common in temperate latitudes (Zostera noltii, Spartina maritima and Scirpus maritimus) on sediment nutrient profiles, and to compare it to sand- and mud-flats without vegetation. The study focused on the organic matter contents, the concentration of dissolved inorganic nutrients (PO₄–P, NH₃–N, NO₃–N), an on the estimation of the total amount of these nutrients during day and night conditions and their potential net-fluxes. It was also hypothesised that in an estuarine system, different plants may have specific effects, and consequently different contributions to the system nutrient dynamics as a whole. Sediment profiles of loss on ignition (LOI) showed an increase of the organic matter contents from sand-flat, to Zostera, Spartina, mud-flat and Scirpus. Statistically, there were significant differences between sediment profiles of phosphate, ammonia and nitrate (Mann-Whitney test, p<0.05), during day and night periods. These results suggest that there is an intense mobility of nutrients in the sediment, showing a day-night variation of nutrient concentrations in the pore-water. In the plants’ rhizosphere, the day-night variation of nutrients seemed dependent on plant biomass and penetration of the roots. Additionally, coupling between plant and sediment seems to be a species-specific process. In spring, Scirpus salt marsh reaches the maximum density and biomass, and despite the higher organic matter contents in the plant covered sediment, Scirpus acts as a sink of nutrients. In contrast, the top 10 cm of the sediment in the Spartina salt marsh and in the Zostera beds may contribute to the efflux of nutrients during the night period, especially phosphate.     

Resolving UV Bioactinometric Results with Intensity and Time Distributions

A UV reactor with an annular design, a total liquid volume of 460[emsp4 ]ml, and outfitted with a single lamp with 1690[emsp4 ]mW of germicidal power was tested. Coliphage MS2 was used as a bioactinometer to measure the UV dose at a flow rate of 56.7[emsp4 ]ml/sec in water with a very low absorbance. The Beers Law coefficient was A₁₀0.003. The measured dose (MS2 bioactinometry) was 35.2±1.1[emsp4 ]mW-sec/cm².A retention time distribution was generated with a dye tracer study. The reactor was modeled as if flow was confined to ten equal volume paths existing as concentric rings around the lamp. The UV intensity along each path (ith intensity) was calculated to generate a simulated distribution of UV intensity in the reactor. The retention time distribution was subdivided to estimate the retention time associated with each decile jth time) of the total flow.Seven methods of associating the ith intensity with the jth retention time were used to produce simulated dose distributions for the reactor. The average UV dose for each distribution was calculated as the average of the products of I and t (AP protocol) and by the apparent survival (AS protocol), in which the predicted survival along each path was averaged to back-calculate dose from the reference batch inactivation curve. The average dose predicted assuming that time and intensity were independent was 51.5[emsp4 ]mW-sec/cm² based on the arithmetic average (AP protocol). Using the apparent survival method, the predicted dose for the independent distribution (I independent of t) was 36.4[emsp4 ]mW-sec/cm². Three methods of developing dependent structure between time and intensity were tested. In the best possible case for stratified flow (I negatively correlated with t) the calculated (AS) intensity was 46.3[emsp4 ]mW-sec/cm^2. In the worst case for stratified flow (I positively correlated with t) the AS intensity was 32.0[emsp4 ]mW-sec/cm². In a rational case where flows were assumed to be distributed parabolically (low flow at the wall and at the lamp) produced an AS intensity of 37.7[emsp4 ]mW-sec/cm². When either time or intensity was averaged, while the other variable was allowed to keep its distribution, the (AS) dose (time averaged 43.3[emsp4 ]mW-sec/cm², intensity averaged 41.0[emsp4 ]mW-sec/cm²), yielded a poor prediction compared to the measured value.The errors associated with averaging time, intensity, or both, far outweigh the errors associated with choosing a rational distribution or an independent distribution of time and intensity in the prediction. This observation is generally true whenever an organism is exposed to UV light in a flow through reactor such that the range of doses is within the portion of the inactivation curve exhibiting strong exponential decay.     

Characterization of serotypes and outer membrane protein profiles in enteroaggregative Escherichia coli strains.

Twenty-four Escherichia coli strains mainly isolated from children with diarrhea in São Paulo, and showing characteristics of enteroaggregative E. coli (EAEC), were characterized by serotyping and outer membrane protein (OMP) profiles. The relationship between these characteristics was evaluated, as well as the usefulness of OMP profiles in the clonal analysis of EAEC strains. All strains presented aggregative adherence to HeLa cells and were classified in two groups based on their interaction with the EAEC DNA probe. A diversity of serotypes and OMP profiles was observed in both groups studied. Although no significant correlation between serotypes and OMP profiles was observed, unique OMP profiles were identified in 80% of the probe-positive strains which were distributed in only 4 OMP profiles. This result may indicate the presence of a few clones in the probe-positive group. On the other hand, probe-negative strains seem to constitute a more diverse group. In general, the observed heterogeneity in serotypes and OMP profiles described in the present study suggest a great genetic diversity in EAEC isolates of either the same or different serotypes and in strains presenting the same EAEC markers identified in our community.     

Diversity and composition of trees and shrubs in Kasagala forest: a semiarid savannah woodland in central Uganda

The diversity and composition of trees and shrubs of ≥5 cm diameter at breast height (DBH) were investigated in Kasagala woodland in central Uganda using 1 ha permanent sample plots. A total of 2745 trees and shrubs with a mean stem density of 686 ha⁻¹ were recorded. These included 69 tree species belonging to 28 families and 47 genera. There was a larger number of small stems compared with that of larger stems. There was significant variation in stem size class distribution between the plots ( F  =   3.14, P  =   0.027). The variation in stem densities (counts) across different size classes was significant ( F  =   8.31, P  <   0.001). Species diversity was higher in the low lands compared with that in the elevated sites in the woodland. The species encountered were unevenly distributed across the plots. Species abundance was not significantly different across the sample plots ( F  =   2.63, P  =   0.053). We suggest that the structure of the forest is typical of any regenerating forest, but other human influences may have played a part in the dominance of size classes <10 cm DBH. The causes of the present status and composition of the woodland require further investigation.     

Distribution-free R sample tests for the hypothesis of parallelism of response profiles

In this paper two nonparametric tests are given for testing the nullhypothesis of parallelity of response curves in r samples. The first procedure is done by a permutation test, whose practical applicability is ensured by a FORTRAN-subroutine available from the author. As the computational work and time grows rapidly with sample sizes, a Monte-Carlo-solution is optionally given by the same procedure. Alternatively an asymptotically distribution-free test based on quadratic forms is constructed for large sample situations.     

Adult transport in the ant Cataglyphis iberica: a means to maintain a uniform colonial odour in a species with multiple nests

Abstract. . Societies of the ant Cataglyphis iberica (Hymenoptera, Formicidae) comprise several satellite queenless nests around a queenright nest. During spring, at the end of hibernation, the incidence of adult transport between these nests is high, but it decreases during summer. Quantitative analyses of the contents of postpharyngeal glands of transporter and transportee ants reveal the amounts of hydrocarbons to be lower in the latter, indicating that these ants are generally younger. Moreover, the more diverse composition of the transportees' secretion may reflect their individual makeup. Transporters, in contrast, maintained a uniform colony odour uirough trophallactic exchanges before entering hibernation. The odour disparity between the transportees and the general colony odour may stimulate the transporters to bear them to the nest containing the queen where they can obtain the colony odour via trophallaxis. The intense traffic between satellite nests in the spring may thus be the means by which a uniform colonial odour is regained after hibernation. Adult transport seems also to be necessary since the young transportee ants are not able to orient themselves and find the other nests.