Growth and DNA damage in young Laminaria sporophytes exposed to ultraviolet radiation: implication for depth zonation of kelps on Helgoland (North Sea)

Growth as an integrative parameter of all physiological processes was measured in young sporophytes of temperate Laminaria digitata, Laminaria saccharina and Laminaria hyperborea exposed in the laboratory to irradiance consisting of either only photosynthetically active radiation (PAR) or to a spectrum including ultraviolet radiation (UVR) (PAR+UVA+UVB) by use of cut-off glass filters. Size increment was measured every 10 min over a period of 18–21 days using growth chambers with on-line video measuring technique. In the chamber, plants were grown at 10±2°C and 16:8 h light–dark cycles with 6 h additional UVR exposure in the middle of the light period. Tissue morphology and absorption spectra were measured in untreated young sporophytes while chlorophyll a content and DNA damage were measured in treated thalli at the end of the experiment. Sensitivity of growth under UVR was found to be related to the observed upper depth distribution limit of the upper sublittoral L. digitata, upper to mid sublittoral L. saccharina and lower sublittoral L. hyperborea. Tissue DNA damage is, however, dependent on thallus thickness which minimizes UVR effect where outer cell layers shade inner cells and provide longer pathlength for UVR. Exposure to UVR causes cellular, enzymatic and molecular damage. Presence of UV-absorbing compounds further reduces effective UVR from reaching physiological targets. The cost of producing higher amount of UV-absorbing compounds and effective DNA repair mechanism can, however, divert photosynthate at the expense of growth. Tissue chlorophyll a content was not significantly different between treatments suggesting a capacity for acclimation to moderate UVR fluence. Growth acclimation to repeated UVR exposure was observed within a period of 12 days while growth inhibition was observed after a longer UVR exposure period of 21 days. The results give further insight into the effects of UVR on the cellular level and show how ecological parameters such as the upper depth distribution limit are dependent on cellular processes.     

CO2 Emission Trends in the Cement Industry: An International Comparison

We present an in-depth decompositionanalysis using physical indicators oftrends in Carbon dioxide (CO₂) emissions in the cementindustry in Brazil, China, South Korea andthe United States. Physical indicatorsallow a detailed analysis of intra-sectoraltrends, in contrast to the often usedmonetary indicators. We assess thecontribution of different factors affectingCO₂ emissions in the cement industry,including change in product mix, efficiencyof power generation, changes in fuel mixand changes in energy efficiency. Thedecomposition results show that in allexamined countries, increased productionwas the main contributor to the increase intotal CO₂ emissions. Energy-efficiencyimprovement is the most important factorthat led to the reduction of emissionintensities for all countries except Korea.For Korea, structural change in the productmix is the most important factorcontributing to the emission intensityreduction.     

Untersuchungskonzept zur Charakterisierung toxischer Stoffe in belastetem Wasser

Zusammenfassung  Zur ?kotoxikologischen Beurteilung von belastetem Wasser werden h?ufig einfache Biotests eingesetzt. Nicht selten werden dabei toxische Effekte festgestellt. Es stellt sich dann die Frage nach den verantwortlichen Wasserinhalts-stoffen. Durch Festphasenextraktion (SPE) werden diese angereichert, gewonnen und dünnschichtchromatographisch unter Verwendung der automatisierten Mehrfachentwicklung aufgetrennt. Von der DC-Platte wird ein Streifen abgetrennt und darauf direkt die biologische Detektion mit Mikroorganismen (Bacillus subtilis, Leuchtbakterien) durchgeführt. Dadurch k?nnen toxische Banden erkannt werden, Auf dem DC-Plattenrest wird von der toxischen Bande mit einem DC-scanner ein UV-Spektrum aufgenommen, die entsprechende Bande herausgekratzt, der toxische Stoff eluiert und infrarotspektroskopisch untersucht. Durch Spektrenvergleich gelingt es meistens, den Stoff zu charakterisieren. In der vorliegenden Arbeit wird am Beispiel eines Zitzengummieluates das Analysenkonzept vorgestelit. Es zeigte sich, dass dieser Gummiartikel einen Vulkanisationsbeschleuniger (2-Mercaptobenzothiazol) freisetzt. Online-Publikation am: 21.12.1999     

The ocean as part of the global carbon cycle

The ocean plays a central role in the global carbon cycle being by far the largest active reservoir. Atmospheric CO₂ level depends on the CO₂concentration in the ocean surface layer, which is relatively low compared to mean oceanic values due to biological and physical carbon pumps. Although the ocean may take up much of the carbon released by the increased burning of fossil fuels, this capacity is limited because of the chemical buffering and a mismatch in time scales (oceanic mixing is much slower than anthropogenic perturbations).