Markus Raubuch

Manganese toxicity in epiphytic lichens: chlorophyll degradation and interaction with iron and phosphorus

Abstract Concentrations of chlorophylls a and b decreased with increasing MnCl2 supply in the epiphytic lichen Hypogymnia physodes, but not in Lecanora conizaeoides. The reduction of chlorophyll concentrations in H. physodes was as strong (chlorophyll a) or even stronger (chlorophyll b) as in samples treated with CuCl2. FeCl3 compensated for MnCl2-induced chlorophyll degradation in H. physodes. Furthermore, MnCl2-induced growth inhibition of soredia cultivated on agar plates was alleviated by FeCl3. These results suggest that Mn causes intracellular Fe deficiency in H. physodes. A soredia growth test with MnCl2 and KCl in combination proved that mitigating effects of FeCl3 were not just caused by reduced chemical activity of Mn2+ due to the addition of another salt. Furthermore, the test showed that Cl− did not inhibit soredia growth. High FeCl3 concentrations applied alone or in combination with MnCl2 were even more detrimental to H. physodes than MnCl2. MnCl2 did not affect the concentrations of ATP, ADP and AMP in H. physodes. This suggests that Mn uptake does not induce intracellular P deficiency in H. physodes despite that Mn is known to be immobilized with P in H. physodes in intracellular polyphosphate granules and in extracellular encrustations.

Long‐term effects on soil microbial properties of heavy metals from industrial exhaust deposition

Soil samples were taken at 0-10 cm and 10-20 cm depth from 7 clay-marsh sites used as grassland close to Nordenham in the north of Lower Saxony, Germany. The sites had been contaminated by deposition of heavy metals from industrial exhausts, the level of contamination varying according to their distances from a lead factory. The soils were analyzed to assess the depth-specific effects of NH 4 NO 3 extractable and total amounts of Zn, Pb, and Cu on basal respiration, adenylates, ergosterol, and biomass C estimated by fumigation extraction (FE) and substrate-induced respiration (SIR). Most of the chemical and biological properties studied decreased with depth, but depth-specific differences in the relationships between these properties rarely occurred. The biomass C/soil organic C ratio was at a relatively high level, but most consistently reflected pollution as a decrease with increasing heavy metal load, independently of the method used for biomass C estimation. However, the SIR estimates were on average 44 % lower than those of FE, mainly due to pH effects. The metabolic quotient SIR- q CO 2 increased with increasing NH 4 NO 3 extractable and total heavy metal contents, but also with decreasing pH, whereas the FE- q CO 2 remained unaffected by heavy metals and pH. The ATP/FE-biomass C ratio was on average 8.2 μmol g -1 and negatively affected by soil pH, but also by total Zn, NH 4 NO 3 extractable Zn and Cu. The ergosterol/FE-biomass C ratio was on average 0.29 %, i.e. at a very low level, and increased with increasing heavy metal content. This indicates a change in the community structure towards fungi.

Soil microbial properties down the profile of a black earth burie by colluvium

The activity and biomass of soil microorganisms were determined in samples at 0—140 cm depth taken from an arable site, where the soil has been developed by erosion and colluvial deposition overlaying a black earth at 70—110 cm depth. The central aim was to get an insight into the breakdown of increasingly old and thus recalcitrant soil organic matter down the profile, effects on the availability of C to microorganisms and the microbial community structure. From 0 to 140 cm depth, microbial biomass C decreased by 96%, biomass N by 97%, the adenylates ATP, ADP, and AMP as well as the basal respiration rate by 89%. No ergosterol was measured at 120—140 cm depth. All soil biological properties decreased in distinct steps after 30 cm and 50 cm depth. At 30—90 cm depth, the amounts of soil organic C and microbial biomass C per hectare of the present colluvium exceeded nearly three-fold those in undisturbed aeolian loess sediments. The cation exchange significantly affected the relationships between microbial biomass C, biomass N, and the adenylates. As a consequence, none of the ratios between the soil microbial biomass properties revealed constant gradients throughout the profile. The adenylate energy charge (AEC) varied between the different soil layers insignificantly around a mean of 0.71. It was the most stable ratio down the profile showing absolutely no depth gradient, the lowest depth-to-depth variation, and also the lowest within depth variability. The other ratios between soil organic C, basal respiration, ergosterol, microbial biomass C and biomass N also did not reveal any marked changes in the microbial community structure. Mikrobielle Bodeneigenschaften eines Tschernosems unter Kolluvium Aktivitat und Biomasse von Bodenmikroorganismen wurden in Proben aus einer Tiefe von 0—140 cm untersucht, die von einer Ackerflache genommen wurden, auf der sich der Boden durch Kolluviation uber einer Schwarzerde in 70—110 cm Tiefe entwickelt hat. Das zentrale Ziel war es, einen Einblick in den Abbau von mit der Tiefe eines Profils zunehmend alter und deshalb schwer zersetzbarer organischer Bodensubstanz und die Auswirkungen auf die Verfugbarkeit von C fur Mikroorganismen und die Struktur der mikrobiellen Gemeinschaften zu untersuchen. Von 0 bis 140 cm Tiefe nahm C in mikrobieller Biomasse um 96% ab, N in mikrobieller Biomasse um 97%, die Adenylate ATP, ADP und AMP sowie die Basalatmung um 89 %. Ergosterol konnte in einer Tiefe von 120—140 cm nicht gemessen werden. Diskrete Stufen in der Abnahme traten nach 30 cm und 50 cm Tiefe fur alle bodenbiologischen Eigenschaften auf. In 30—90 cm Tiefe des Kolluviums ubertraf die Menge an C in organischer Bodensubstanz und C mikrobieller Biomasse pro Hektar diejenige in Boden aus ungestorten Lossen um nahezu das Dreifache. Die Kationen-Austausch-Kapazitat hatte einen signifikanten Einfluss auf die Beziehungen zwischen C und N in mikrobieller Biomasse und den Adenylaten. Das hat zur Konsequenz, dass keiner der Quotienten zwischen mikrobiellen Bodeneigenschaften konstante Gradienten im Profil aufwies. Der Adenylate-Energy-Charge (AEC) variierte zwischen den verschiedenen Tiefenstufen ohne Signifikanz um einen Mittelwert von 0.71. Im Profil abwarts war er damit der stabilste Quotient, ohne jeden Tiefengradienten, mit der geringsten Variation von Tiefen- zu Tiefenstufe, und ebenfalls der geringsten Variabilitat innerhalb einer Tiefenstufe. Auch die ubrigen Quotienten zwischen C in organischer Bodensubstanz, Basalatmung, Ergosterol, C und N in mikrobieller Biomasse zeigten keine deutlichen Veranderungen in der Struktur der mikrobiellen Gemeinschaften.