Uran in Wässern

The study presents 172 measurements of the uranium²³⁸U and²³⁴U isotopes in ground water and 21 measurements of these substances in the rivers of Eastern Germany. The uranium concentration in the ground water ranged from under 0.1 mBq/l to over 1000 mBg/l with a mean of 12 mBq/l. The respective activity relationships of²³⁴U/²³⁸U ranged from 0.85 to 12.6 with a mean of 1.66. A comparison of these values with those in the literature demonstrates an agreement with more recent measurements obtained from water in Thuringia and Saxony which were seen to have a mean value of 19 mBq/l. The activity relationships of²³⁴U/²³⁸U which were seen to be substantially over the equilibrial value of 1.0 and which were found in a quite high proportion of the samples must be taken into consideration when evaluating these. The measurements of river water demonstrated values for the Elbe river which are related to the periods of extensive uranium mining in Saxony and Thuringia. Measurements performed in the catchment regions going into the Baltic Sea revealed substantially higher values than would be expected from the distribution of uranium in these areas. A number of reasons are discussed here in an attempt to explain these findings.     

Seasonal variations in distribution patterns of sympagic meiofauna in Arctic pack ice

During two expeditions of the R.V. Polarstern to the Arctic Ocean, pack ice and under-ice water samples were collected during two different seasons: late summer (September 2002) and late winter (March/April 2003). Physical and biological properties of the ice were investigated to explain seasonal differences in species composition, abundance and distribution patterns of sympagic meiofauna (in this case: heterotrophs >20 µm). In winter, the ice near the surface was characterized by extreme physical conditions (minimum ice temperature: –22°C, maximum brine salinity: 223, brine volume: 5%) and more moderate conditions in summer (minimum ice temperature: –5.6°C, maximum brine salinity: 94, most brine volumes: 5%). Conditions in the lowermost part of the ice did not differ to a high degree between summer and winter. Chlorophyll a concentrations (chl a) showed significant differences between summer and winter: during winter, concentrations were mostly <1.0 µg chl a l^–1, while chl a concentrations of up to 67.4 µmol l^–1 were measured during summer. The median of depth-integrated chl a concentration in summer was significantly higher than in winter. Integrated abundances of sympagic meiofauna were within the same range for both seasons and varied between 0.6 and 34.1×10³ organisms m^–2 in summer and between 3.7 and 24.8×10³ organisms m^–2 in winter. With regard to species composition, a comparison between the two seasons showed distinct differences: while copepods (42.7%) and rotifers (33.4%) were the most abundant sea-ice meiofaunal taxa during summer, copepod nauplii dominated the community, comprising 92.9% of the fauna, in winter. Low species abundances were found in the under-ice water, indicating that overwintering of the other sympagic organisms did not take place there, either. Therefore, their survival strategy over the polar winter remains unclear.Communicated by O. Kinne, Oldendorf/Luhe     

Distribution,abundance and survival of juvenile hermatypic corals (Scleractinia) and the importance of life history strategies in the parent coral community

The distribution and abundance of juvenile corals were examined at depths from 3 to 37 m on the reefs of Curaçao and Bonaire (Netherlands Antilles). Juveniles of Agaricia agaricites were most abundant (60.6%), followed by Helioseris cucullata (8.3%). The large massive corals such as Montastrea annularis, M. cavernosa and branched species such as Madracis mirabilis and Acropora palmata had few juveniles. This, combined with species characteristics, shows that these species employ very different life history strategies. In some species the abundance of juveniles over the reef paralleled that of larger colonies, but not for example in Agaricia agaricites. The composition of the coral community was apparently no direct function of juvenile abundance. A change in angle of settlement of A. agaricites juveniles with increasing depth, from vertical to horizontal surfaces, seems to reflect the preferred light intensity. We studied the survival of juvenile corals during a half-year period. One-third remained unharmed, one-third died or disappeared, and one-third was limited in growth by factors such as spatial competition. This was the same for all depths, but factors influencing survival varied with depth.     

Cycle synchrony and probability of conception in female hamadryas baboonsPapio hamadryas

We investigated the factors affecting conception in a captive population ofPapio hamadryas. We collected data on reproductive states from 16 females over 12 years. Probability of conception was related to the outcome of the immediately preceding pregnancy and the fate of the preceding offspring. After abortions or when an infant survived more than 6 months, a female needed more cycles to conceive than when an infant died within the first 6 months post partum. The degree of estrus synchrony within, but not between, one-male units influenced the probability of conception. Females experiencing conceptive estrus showed less synchrony than those experiencing nonconceptive estrus. The number of females simultaneously in estrus within a one-male unit was negatively correlated with the probability of conception. Within our captive population, group size and male and female age had no influence on the probability of conception. The results indicate that sperm may be a limited resource in the one-male reproductive units of hamadryas baboons. Female-female competition for conception may exist and should influence the demography of one-male units.     

Toxicity of cupric lon to eggs of the spot Leiostomus xanthurus and the Atlantic silverside Menidia menidia

Experiments were conducted to determine the toxicity of free cupric ion to the eggs of two marine fish: the spot Leiostomus xanthurus, and the Atlantic silverside Menidia menidia. A cupric ion buffer consisting of 5 mM of the chelator, trishydroxymethylamino methane (Tris), and varied concentrations of CuSO₄ was employed to achieve stable cupric ion activities in experimental seawater media. Egg hatch of the silverside appears to be more sensitive to cupric ion than that of the spot. The silverside had 60% inhibition of hatch at a pCu (negative logarithum of cupric ion activity) of 9.4 with complete supporession of hatching at pCu values below 8.2, while the spot had 50% inhibition at a pCu of 9.0 and complete suppression at a pCu of 8.0. Cupric ion was most toxic to the eggs of silverside at or around the time of hatching, whereas a pronounced sensitivity at hatching was not apparent with the eggs of spot. Calculated estimates of the range of cupric ion activity in seawater indicate that natural activity levels may in some instances inhibit the hatching of silverside and spot eggs.     

The application of geographic information systems to geochemical studies in Jamaica

The Centre for Nuclear Sciences (CNS) uses a raster based geographic information system (GIS), integrated with a relational database to store information on point sampled data, including concentrations of over 50 elements and/or ions in a variety of sample materials. These data are filtered in the GIS to create surface layers and are assigned colours according to percentile ranges allowing visual inspection to be used to identify significant features and trends. The database currently contains raster map layers for soils and geologic features, point site data for water and air, and vector data for roads, rivers and streams. While data are still being added to the database interesting results are already being obtained and a few instances where the GIS was used to assist in the data interpretation are reported.     

Antimicrobial activities of extracts from tropical Atlantic marine plants against marine pathogens and saprophytes

Studies investigating disease resistance in marine plants have indicated that secondary metabolites may have important defensive functions against harmful marine microorganisms. The goal of this study was to systematically screen extracts from marine plants for antimicrobial effects against marine pathogens and saprophytes. Lipophilic and hydrophilic extracts from species of 49 marine algae and 3 seagrasses collected in the tropical Atlantic were screened for antimicrobial activity against five ecologically relevant marine microorganisms from three separate kingdoms. These assay microbes consisted of the pathogenic fungus Lindra thalassiae, the saprophytic fungus Dendryphiella salina, the saprophytic stramenopiles, Halophytophthora spinosa and Schizochytrium aggregatum, and the pathogenic bacterium Pseudoaltermonas bacteriolytica. Overall, 90% of all species surveyed yielded extracts that were active against one or more, and 77% yielded extracts that were active against two or more assay microorganisms. Broad-spectrum activity against three or four assay microorganisms was observed in the extracts from 48 and 27% of all species, respectively. The green algae Halimeda copiosa and Penicillus capitatus (Chlorophyta) were the only species to yield extracts active against all assay microorganisms. Among all assay microorganisms, both fungi were the most resistant to the extracts tested, with less than 21% of all extracts inhibiting the growth of either L. thalassiae or D. salina. In contrast, over half of all lipophylic extracts were active against the stramenopiles H. spinosa and S. aggregatum, and the bacterium P. bacteriolytica. Growth sensitivity to hydrophilic extracts varied considerably between individual assay microorganisms. While 48% of all hydrophilic extracts were active against H. spinosa, 27% were active against P. bacteriolytica, and only 14% were active against S. aggregatum. Overall, more lipophilic extracts inhibited microbial growth than hydrophilic extracts. The variability observed in the antimicrobial effects of individual extracts against each assay microorganism reflects the importance of choosing appropriate test microbes in assays from which ecologically relevant information is sought. Results from this survey demonstrate that antimicrobial activities are prevalent among extracts from marine algae and seagrasses, suggesting that antimicrobial chemical defenses are widespread among marine plants.