Effects of nitrogen limitation on biofilm formation in a hydrocarbon-degrading trickle-bed filter

The effect of nitrogen limitation on young and mature steady-state biofilm in a trickle-bed filter was studied. Toluene and n-heptane were the sole carbon source. Biomass concentration, respiration, substrate-induced respiration, metabolic quotient, and total hydrocarbon degradation efficiency were measured. The aim of the experiment was to control excess biomass production in the trickle-bed filter by limiting the mineral nutrients and to achieve increased mineralization of the carbon source. Biofilm growth responded strongly to the amount of available nitrogen, whereas hydrocarbon degradation efficiency reached a maximum of 60% and could not be increased even by further addition of nitrogen. The experiments showed that 95% of the adsorbed carbon was mineralized completely and only 5% was used for biofilm formation. This complete mineralization can also be concluded from the metabolic quotient. The value of the latter was about 6–10 mg CO₂-C g⁻¹C_mic h⁻¹, indicating an expanded energy demand due to stress effects in the presence of nutrient deficiency. It was postulated that determination of the metabolic quotient could be an simple instrument to measure the rate of mineralization of carbon sources and also the rate of biomass formation in trickle-bed filters or biofilters. Received: 11 November 1998 / Accepted: 5 December 1998     

Stem respiration of ponderosa pines grown in contrasting climates: implications for global climate change

We examined the effects of climate and allocation patterns on stem respiration in ponderosa pine (Pinus ponderosa) growing on identical substrate in the cool, moist Sierra Nevada mountains and the warm, dry, Great Basin Desert. These environments are representative of current climatic conditions and those predicted to accompany a doubling of atmospheric CO₂, respectively, throughout the range of many western north American conifers. A previous study found that trees growing in the desert allocate proportionally more biomass to sapwood and less to leaf area than montane trees. We tested the hypothesis that respiration rates of sapwood are lower in desert trees than in montane trees due to reduced stem maintenance respiration (physiological acclimation) or reduced construction cost of stem tissue (structural acclimation). Maintenance respiration per unit sapwood volume at 15°C did not differ between populations (desert: 6.39 ± 1.14 SE μmol m⁻³ s⁻¹, montane: 6.54 ± 1.13 SE μmol m⁻³ s⁻¹, P = 0.71) and declined with increasing stem diameter (P = 0.001). The temperature coefficient of respiration (Q ₁₀) varied seasonally within both environments (P = 0.05). Construction cost of stem sapwood was the same in both environments (desert: 1.46 ± 0.009 SE g glucose g⁻¹ sapwood, montane: 1.48 ± 0.009 SE glucose g⁻¹ sapwood, P = 0.14). Annual construction respiration calculated from construction cost, percent carbon and relative growth rate was greater in montane populations due to higher growth rates. These data provide no evidence of respiratory acclimation by desert trees. Estimated yearly stem maintenance respiration was greater in large desert trees than in large montane trees because of higher temperatures in the desert and because of increased allocation of biomass to sapwood. By analogy, these data suggest that under predicted increases in temperature and aridity, potential increases in aboveground carbon gain due to enhanced photosynthetic rates may be partially offset by increases in maintenance respiration in large trees growing in CO₂-enriched atmospheres. Received: 4 November 1996 / Accepted: 23 January 1997     

Photosynthetic acclimation of maize to growth under elevated levels of carbon dioxide

The effects of elevated CO₂ concentrations on the photochemistry, biochemistry and physiology of C₄ photosynthesis were studied in maize (Zea mays L.). Plants were grown at ambient (350 μL L⁻¹) or ca. 3 times ambient (1100 μL L⁻¹) CO₂ levels under high light conditions in a greenhouse for 30 d. Relative to plants grown at ambient CO₂ levels, plants grown under elevated CO₂ accumulated ca. 20% more biomass and 23% more leaf area. When measured at the CO₂ concentration of growth, mature leaves of high-CO₂-grown plants had higher light-saturated rates of photosynthesis (ca. 15%), lower stomatal conductance (71%), higher water-use efficiency (225%) and higher dark respiration rates (100%). High-CO₂-grown plants had lower carboxylation efficiencies (23%), measured under limiting CO₂, and lower leaf protein contents (22%). Activities of a number of C₃ and C₄ cycle enzymes decreased on a leaf-area basis in the high-CO₂-grown plants by 5–30%, with NADP-malate dehydrogenase exhibiting the greatest decrease. In contrast, activities of fructose 1,6-bisphosphatase and ADP-glucose pyrophosphorylase increased significantly under elevated CO₂ condition (8% and 36%, respectively). These data show that the C₄ plant maize may benefit from elevated CO₂ through acclimation in the capacities of certain photosynthetic enzymes. The increased capacity to synthesize sucrose and starch, and to utilize these end-products of photosynthesis to produce extra energy by respiration, may contribute to the enhanced growth of maize under elevated CO₂. Received: 30 April 1999 / Accepted: 17 June 1999     

Adaptation and acclimation of growth and photosynthesis of five Antarctic red algae to low temperatures

Temperature requirements for growth, photosynthesis and dark respiration were determined for five Antarctic red algal species. After acclimation, the stenothermal species Gigartina skottsbergii and Ballia callitricha grew at 0 or up to 5 °C, respectively; the eurythermal species Kallymenia antarctica, Gymnogongrus antarcticus and Phyllophora ahnfeltioides grew up to 10 °C. The temperature optima of photosynthesis were between 10 and 15 °C in the stenothermal species and between 15 and 25 °C in the eurythermal species, irrespective of the growth temperature. This shows that the temperature optima for photosynthesis are located well below the optima from species of other biogeographical regions, even from the Arctic. Respiratory rates rose with increasing temperatures. In contrast to photosynthesis, no temperature optimum was evident between 0 and 25 °C. Partial acclimation of photosynthetic capacity to growth temperature was found in two species. B. callitricha and Gymnogongrus antarcticus acclimate to 0 °C, and 5 and 0 °C, respectively. But acclimation did in no case lead to an overall shift in the temperature optimum of photosynthesis. B. callitricha and Gymnogongrus antarcticus showed acclimation of respiration to 5 °C, and P. ahnfeltioides to 5 and 10 °C, resulting in a temperature independence of respiration when measured at growth temperature. With respect to the acclimation potential of the species, no distinction can be made between the stenothermal versus the eurythermal group. (Net)photosynthetic capacity:respiration (P:R) ratios showed in all species highest values at 0 °C and decreased continuously to values lower than 1.0 at 25 °C. In turn, the low P:R ratios at higher temperatures are assumed to determine the upper temperature growth limit of the studied species. Estimated daily carbon balance reached values between 4.1 and 30.7 mg C g⁻¹ FW day⁻¹ at 0 °C, 16:8 h light/dark cycle, 12–40 μmol m⁻² s⁻¹. Received: 4 November 1999 / Accepted: 7 March 2000     

Acclimation of the summer annual species, Lolium temulentum, to CO2 enrichment

Lolium temulentum L. Ba 3081 was grown hydroponically in air (350 μmol mol⁻¹ CO₂) and elevated CO₂ (700 μmol mol⁻¹ CO₂) at two irradiances (150 and 500 μmol m⁻² s⁻¹) for 35 days at which point the plants were harvested. Elevated CO₂ did not modify relative growth rate or biomass at either irradiance. Foliar carbon-to-nitrogen ratios were decreased at elevated CO₂ and plants had a greater number of shorter tillers, particularly at the lower growth irradiance. Both light-limited and light-saturated rates of photosynthesis were stimulated. The amount of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) protein was increased at elevated CO₂, but maximum extractable Rubisco activities were not significantly increased. A pronounced decrease in the Rubisco activation state was found with CO₂ enrichment, particularly at the higher growth irradiance. Elevated-CO₂-induced changes in leaf carbohydrate composition were small in comparison to those caused by changes in irradiance. No CO₂-dependent effects on fructan biosynthesis were observed. Leaf respiration rates were increased by 68% in plants grown with CO₂ enrichment and low light. We conclude that high CO₂ will only result in increased biomass if total light input favourably increases the photosynthesis-to-respiration ratio. At low irradiances, biomass is more limited by increased rates of respiration than by CO₂-induced enhancement of photosynthesis. Received: 23 February 1999 / Accepted: 15 June 1999     

Water stress impacts on respiratory rate, efficiency and substrates, in growing and mature foliage of Eucalyptus spp

In previous studies, water stress has induced variable and sometimes contradictory changes in respiration. We used isothermal calorimetry to measure the response of foliar respiration to water deficit in nine eucalypt genotypes. Specific growth rates (R _SG) of shoots and leaves of variable age were measured independently, and the data were applied to both the growth-maintenance and enthalpy balance models. We calculated the oxidation state of respiratory substrate and the enthalpy change for the conversion of substrate carbon to biomass (ΔH _B). Moderate water stress reduced the R _SG of shoots by 38% (P<0.01) and carbon conversion efficiency by 15% (P<0.05). The relationship between carbon conversion efficiency and R _SG was not affected by water deficit for shoots, but was significantly altered for leaves. Water deficit increased maintenance respiration by about 23% (P<0.001). The growth coefficient of respiration was not significantly altered. However, changes in oxidation states of substrate and biomass suggest that the energy requirements of biosynthesis were increased under water stress. Our results confirm that carbohydrates are the major respiratory substrates in growing tissues, though mature leaves utilized a substantial component of more reduced substrate. Mature leaves had variable oxidation states for respiration substrate, which indicates a variable relationship between CO₂ evolution and ATP production. Measured ΔH _B in shoots and leaves were too small for reliable estimation of R _SG by the enthalpy balance model. We also found significant effects of water stress on the oxidation state of substrate and ΔH _B.     

Anaerobic bioconversion of cellulose by Ruminococcus albus, Methanobrevibacter smithii, and Methanosarcina barkeri

A system is described that combines the fermentation of cellulose to acetate, CH₄, and CO₂ by Ruminococcus albus and Methanobrevibacter smithii with the fermentation of acetate to CH₄ and CO₂ by Methanosarcina barkeri to convert cellulose to CH₄ and CO₂. A cellulose-containing medium was pumped into a co-culture of the cellulolytic R. albus and the H₂-using methanogen, Mb. smithii. The effluent was fed into a holding reservoir, adjusted to pH 4.5, and then pumped into a culture of Ms. barkeri maintained at constant volume by pumping out culture contents. Fermentation of 1% cellulose to CH₄ and CO₂ was accomplished during 132 days of operation with retention times (RTs) of the Ms. barkeri culture of 7.5–3.8 days. Rates of acetate utilization were 9.5–17.3 mmol l⁻¹ day⁻¹ and increased with decreasing RT. The K _s for acetate utilization was 6–8 mM. The two-stage system can be used as a model system for studying biological and physical parameters that influence the bioconversion process. Our results suggest that manipulating the different phases of cellulose fermentation separately can effectively balance the pH and ionic requirements of the acid-producing phase with the acid-using phase of the overall fermentation. Received: 7 December 1999 / Received revision: 28 April 2000 / Accepted: 19 May 2000     

Cometabolic biodegradation of methyl t-butyl ether by Pseudomonas aeruginosa grown on pentane

A bacterial strain identified as Pseudomonas aeruginosa was isolated from a soil consortium able to mineralize pentane. P. aeruginosa could metabolize methyl t-butyl ether (MTBE) in the presence of pentane as the sole carbon and energy source. The carbon balance for this strain, grown on pentane, was established in order to determine the fate of pentane and the growth yield (0.9 g biomass/g pentane). An inhibition model for P. aeruginosa grown on pentane was proposed. Pentane had an inhibitory effect on growth of P. aeruginosa, even at a concentration as low as 85 μg/l. This resulted in the calculation of the following kinetic parameters (μ_max = 0.19 h⁻¹, K _s = 2.9 μg/l, K _i = 3.5 mg/l). Finally a simple model of MTBE degradation was derived in order to predict the quantity of MTBE able to be degraded in batch culture in the presence of pentane. This model depends only on two parameters: the concentrations of pentane and MTBE. Received: 16 July 1998 / Received revision: 11 November 1998 / Accepted 31 November 1998     

Assimilate export by leaves of Ricinus communis L. growing under normal and elevated carbon dioxide concentrations: the same rate during the day, a different rate at night

Castor bean (Ricinus communis L.) plants were grown for 5–7 weeks in a controlled environment at 350 μl l⁻¹ or 700 μl l⁻¹ CO₂. Carbon assimilation, assimilate deposition, dark respiration and assimilate mobilization were measured in leaves 2, 3 and 4 (counted from the base of the plant), and a balance sheet of carbon input and export was elaborated for both CO₂ concentrations. Carbon dioxide assimilation was nearly constant over the illumination period, with only a slight depression occurring at the end of the day in mature source leaves, not in young source leaves. Assimilation was ca. 40% higher at 700 μl l⁻¹ than at 350 μl l⁻¹ CO₂. The source leaves increased steadily in weight per unit area during the first 3 weeks, more at 700 μl l⁻¹ than at 350 μl l⁻¹ CO₂. On top of an irreversible weight increase, there was a large gain in dry weight during the day, which was reversed during the night. This reversible weight gain was constant over the life time of the leaf and ca. 80% higher at 700 μl l⁻¹ than at 350 μl l⁻¹. Most of it was due to carbohydrates. The carbon content (as a percentage) was not altered by the CO₂ treatment. Respiration was 25% higher in high-CO₂ plants when based on leaf area, but the same when based on dry weight. The rate of carbon export via the phloem was the same during the daytime in plants grown at 350 μl l⁻¹ and 700 μl l⁻¹ CO₂. During the night the low-CO₂ plants had only 50% of the daytime export rate, in contrast to the high-CO₂ plants which maintained the high export rate. It was concluded that the phloem loading system is saturated during the daytime in both CO₂ regimes, whereas during the night the assimilate supply is reduced in plants in the normal CO₂ concentration. Two-thirds of the carbon exported from the leaves was permanently incorporated as plant dry matter in the residual plant parts. This “assimilation efficiency” was the same for both CO₂ regimes. It is speculated that under 350 μl l⁻¹ CO₂ the growing Ricinus plant operates at sink limitation during the day and at source limitation during the night. Received: 2 February 1999 / Accepted: 19 April 1999     

Microalgal growth enhancement by levoglucosan isolated from the green seaweed <Emphasis Type="Italic">Monostroma nitidum</Emphasis>

Microalgal growth was enhanced by the addition of levoglucosan to the culture medium. The growth-enhancing compound levoglucosan was isolated from the green seaweed Monostroma nitidum using water extraction, molecular fractionation, DEAE-cellulose column chromatography, and high-performance liquid chromatography. Yield of the compound from seaweed powder was 5 × 10⁻³% (w/w). At 10 mM concentration, levoglucosan enhanced cell growth and the specific growth rate of all feed microalgal species tested (Chaetoceros gracilis, Chlorella ellipsoidea, Dunaliella salina, Isochrysis galbana, Nannochloris oculata, Navicula incerta, Pavlova lutheri, Tetraselmis suecica) in most culture media by approximately 150%. Cellular fatty acid profiles and cell size differed marginally between cultures with and without levoglucosan.     

The ferrous iron oxidation kinetics of Thiobacillus ferrooxidans in batch cultures

The ferrous iron oxidation kinetics of Thiobacillus ferrooxidans in batch cultures was examined, using on-line off-gas analyses to measure the oxygen and carbon dioxide consumption rates continuously. A cell suspension from continuous cultures at steady state was used as the inoculum. It was observed that a dynamic phase occurred in the initial phase of the experiment. In this phase the bacterial ferrous iron oxidation and growth were uncoupled. After about 16 h the bacteria were adapted and achieved a pseudo-steady state, in which the specific growth rate and oxygen consumption rate were coupled and their relationship was described by the Pirt equation. In pseudo-steady state, the growth and oxidation kinetics were accurately described by the rate equation for competitive product inhibition. Bacterial substrate consumption is regarded as the primary process, which is described by the equation for competitive product inhibition. Subsequently the kinetic equation for the specific growth rate, μ, is derived by applying the Pirt equation for bacterial substrate consumption and growth. The maximum specific growth rate, μ _max, measured in the batch culture agrees with the dilution rate at which washout occurs in continuous cultures. The maximum oxygen consumption rate, q _O2,max, of the cell suspension in the batch culture was determined by respiration measurements in a biological oxygen monitor at excess ferrous iron, and showed changes of up to 20% during the course of the experiment. The kinetic constants determined in the batch culture slightly differ from those in continuous cultures, such that, at equal ferric to ferrous iron concentration ratios, biomass-specific rates are up to 1.3 times higher in continuous cultures. Received: 8 February 1999 / Accepted: 17 February 1999     

New insights on toluene biodegradation by Pseudomonas putida F1: influence of pollutant concentration and excreted metabolites

The influence of toluene concentration on the specific growth rate, cellular yield, specific CO₂, and metabolite production by Pseudomonas putida F1 (PpF1) was investigated. Both cellular yield and specific CO₂ production remained constant at 1.0 ± 0.1 g biomass dry weight (DW) g⁻¹ toluene and 1.91 ± 0.31 g CO₂ g⁻¹ biomass, respectively, under the tested range of concentrations (2–250 mg toluene l⁻¹). The specific growth rate increased up to 70 mg toluene l⁻¹. Further increases in toluene concentration inhibited PpF1 growth, although inhibitory concentrations were far from the application range of biological treatment processes. The specific ATP content increased with toluene concentration up to toluene concentrations of 170 mg l⁻¹. 3-Methyl catechol (3-MC) was never detected in the cultivation medium despite being an intermediary in the TOD pathway. This suggested that the transformation from toluene to 3-MC was the limiting step in the biodegradation process. On the other hand, benzyl alcohol (BA) was produced from toluene in a side chain reaction. This is, to the best of our knowledge, the first reported case of methyl monoxygenation of toluene by PpF1 not harboring the pWW0 TOL plasmid. In addition, the influence of 3-MC, BA, and o-cresol on toluene degradation was investigated respirometrically, showing that toluene-associated respiration was not significantly inhibited in the presence of 10–100 mg l⁻¹ of the above-mentioned compounds.     

Effect of oxygen and carbon dioxide on germination and growth ofRhizopus oligosporus on model media and soya beans

 The microcolony technique enables the effects of several atmospheric conditions on fungal growth to be studied by measuring the radius of the colony, while excluding effects of those conditions on germination of the sporangiospores. Various concentrations of oxygen and carbon dioxide in the gas environment were found to influence growth of Rhizopus oligosporus on malt extract/soya peptone/agar. The maximum radial growth rate was 1.48 mm/h and the maximum specific growth rate was 0.109 h^-1 at 30 °C. Oxygen became limiting below 1% (v/v), but growth remained possible at levels of 0.001% oxygen. Carbon dioxide stimulated growth at limiting oxygen levels. The specific growth rate increased from 0.043 h^-1 at 0.5% (v/v) oxygen and 0% (v/v) carbon dioxide to 0.096 h^-1 at 0.5% (v/v) oxygen and 5% (v/v) carbon dioxide. A mixture of 0.5% (v/v) oxygen and 35% (v/v) carbon dioxide inhibited growth. Delay of sporangiospore germination due to low (less than 0.001%) amounts of oxygen was not observed with the techniques used. Fungal activity in a rotating drum fermentor was more strongly affected by low levels of oxygen than was biomass formation on model media. High concentrations of carbon dioxide inhibited growth in the rotating drum fermentor at non-limiting levels of oxygen. It is concluded that aeration and heat removal are both essential aspects of optimization of large-scale solid-substrate bioreactors with Rh. oligosporus. Received: 5 August 1994/Received revision: 14 November 1994/Accepted: 5 December 1994     

Bioenergetics and RNA/DNA ratios in the common carp (Cyprinus carpio ) under hypoxia

Hypoxia caused by eutrophication occurs over large areas in aquatic systems worldwide. Common carp (Cyprinus carpio) exposed to hypoxia (1 mg · O₂ · l⁻¹ and 2 mg · O₂ · l⁻¹) for 1 week showed a significant reduction in feeding rate, respiration rate, faecal production and nitrogenous excretion compared to those maintained at normoxia (7 mg · O₂ · l⁻¹). Fish exposed to hypoxia showed negative scope for growth (SfG), but no significant difference in the specific growth rate was revealed after 1 week in both hypoxic groups. A significant reduction in RNA/DNA ratio was, however, clearly evident in the white muscle of the 1 mg · O₂ · l⁻¹ treatment group, but not in the 2 mg · O₂ · l⁻¹ treatment group. Both specific growth rate and RNA/DNA ratio were significantly reduced when fish were exposed to severe hypoxia (0.5 mg · O₂ · l⁻¹) for 4 weeks. At all levels of hypoxia, growth reduction was accompanied by a significant decrease in RNA/DNA ratio in white muscle. Covariance analysis showed no significant difference between the slope of RNA/DNA ratio and growth rate under normoxic conditions and 0.5 mg · O₂ · l⁻¹ for 4 weeks (F=1.036, P > 0.326), as well as 1.0 mg · O₂ · l⁻¹ and 2.0 mg · O₂ · l⁻¹ for 1 week (F = 0.457, P > 0.5), indicating that the RNA/DNA ratio serves as a biomarker of growth under all oxygen levels, at least under controlled experimental conditions. SfG also appears to be more sensitive than the RNA/DNA ratio in responding to hypoxia in fish. Accepted: 15 September 2000     

Root production, turnover and respiration under two grassland types along an altitudinal gradient: influence of temperature and solar radiation

 We have measured the rates of root production and death and of root respiration in situ under two grasslands along an altitudinal gradient in the northern Pennines, UK, represented by a lowland site at 171 m in an agricultural setting, and three upland sites between 480 and 845 m. One grassland was dominated by Festuca ovina and was on a brown earth soil; the other was dominated by Juncus squarrosus and Nardus stricta and occurred on a peaty gley. The natural altitudinal gradient was extended by transplantation. Although root biomass and root production (estimated using minirhizotrons) both showed pronounced seasonal peaks, there was no simple altitudinal gradient in either variable, and neither root production nor root death rate was a simple function of altitude. Increased root accumulation in summer was a function of change in the length of the growing season, not of soil temperature. Root populations in winter were similar at all sites, showing that increased production at some sites was accompanied by increased turnover, a conclusion confirmed by cohort analyses. Respiration rate, measured in the field by extracting roots and measuring respiration at field temperature in an incubator, was unrelated to temperature. The temperature sensitivity of respiration (expressed as the slope of a plot of log respiration rate against temperature) showed no simple seasonal or altitudinal pattern. Both root growth (under Festuca) and respiration rate were, however, closely related to radiation fluxes, averaged over the previous 10 days for growth and 2 days for respiration. The temperature sensitivity of respiration was a function of soil temperature at the time of measurement. These results show that root growth and the consequent input of carbon to soil in these communities is controlled by radiation flux not temperature, and that plants growing in these upland environments may acclimate strongly to low temperatures. Most carbon cycle models assume that carbon fluxes to soil are powerfully influenced by temperature, but that assumption is based largely on short-term studies and must be reassessed. Received: 11 August 1997 / Accepted: 25 October 1997     

Biodegradation of methyl t-butyl ether by pure bacterial cultures

Three pure bacterial cultures degrading methyl t-butyl ether (MTBE) were isolated from activated sludge and fruit of the Gingko tree. They have been classified as belonging to the genuses Methylobacterium, Rhodococcus, and Arthrobacter. These cultures degraded 60 ppm MTBE in 1–2 weeks of incubation at 23–25 °C. The growth of the isolates on MTBE as sole carbon source is very slow compared with growth on nutrient-rich medium. Uniformly-labeled [¹⁴C]MTBE was used to determine ¹⁴CO₂ evolution. Within 7 days of incubation, about 8% of the initial radioactivity was evolved as ¹⁴CO₂. These strains also grow on t-butanol, butyl formate, isopropanol, acetone and pyruvate as carbon sources. The presence of these compounds in combination with MTBE decreased the degradation of MTBE. The cultures pregrown on pyruvate resulted in a reduction in ¹⁴CO₂ evolution from [¹⁴C]MTBE. The availability of pure cultures will allow the determination of the pathway intermediates and the rate-limiting steps in the degradation of MTBE. Received: 8 December 1995 / Received last revision: 5 August 1996 / Accepted: 12 August 1996     

Feeding dynamics and respiration of the bottom-dwelling caridean shrimp Nauticaris marionis Bate, 1888 (Crustacea: Decapoda) in the vicinity of Marion Island (Southern Ocean)

The feeding dynamics and oxygen uptake of the bottom-dwelling caridean shrimp Nauticaris marionis were studied during the April/May 1984, 1996 and 1997 cruises to Marion Island (Prince Edward Islands, Southern Ocean). N. marionis is thought to have an opportunistic feeding mode. Prey composition varied considerably between the years and sites investigated. Overall, benthic (mainly hydrozoans and bottom-dwelling polychaetes) and, at times, pelagic (largely euphausiids and copepods) prey items dominated in the stomachs of N. marionis both by occurrence and by volume. Generally, pelagic prey contributed more to the diets of smaller shrimps, while benthic prey was a more important component in the guts of larger specimens. Wet, dry and ash-free dry weight were determined for specimens used in respiration experiments. The respiration rates of N. marionis females with carapace length 6.6–11.1 mm ranged from 80 to 250 μl O₂ individual⁻¹ · h⁻¹, or from 0.588 to 2.756 μl O₂ · mg⁻¹ dry weight h⁻¹. Regression analyses showed highly significant correlations between oxygen consumption and carapace length for N. marionis. Daily ingestion rates estimated using an in situ gut content analysis technique (4.4% of body dry weight) and an energy budget approach (average 4.7% of body dry weight, range 2.0–7.5%) showed good agreement with each other. Accepted: 29 July 1998     

CO2 exchange of the endolithic lichen Verrucaria baldensis from karst habitats in northern Italy

CO₂ exchange of the endolithic lichen Verrucaria baldensis was measured in the laboratory under different conditions of water content, temperature, light, and CO₂ concentration. The species had low CO₂ exchange rates (maximum net photosynthesis: c. 0.45 μmol CO₂ m⁻² s⁻¹; maximum dark respiration: c. 0.3 μmol CO₂ m⁻² s⁻¹) and a very low light compensation point (7 μmol photons m⁻² s⁻¹ at 8°C). The net photosynthesis/respiration quotient reached a maximum at 9–15°C. Photosynthetic activity was affected only after very severe desiccation, when high resaturation respiratory rates were measured. Microclimatic data were recorded under different weather conditions in an abyss of the Trieste Karst (northeast Italy), where the species was particularly abundant. Low photosynthetically active radiation (normally below 40 μmol photons m⁻² s⁻¹), very high humidities (over 80%), and low, constant temperatures were measured. Thallus water contents sufficient for CO₂ assimilation were often measured in the absence of condensation phenomena. Received: 22 September 1996 / Accepted: 26 April 1997     

Reduction of biomass in a bioscrubber for waste gas treatment by limited supply of phosphate and potassium ions

  Elimination of n-butanol from the gas phase was examined with a mixed culture in a compact bioscrubber. The extent of the cell concentration was limited by the supply of n-butanol, phosphate or potassium, and the growth rate was determined by the dilution rate. With n-butanol as the limiting substrate the cellular yield was 0.53 g dry cell weight/g n-butanol. Phosphate limitation decreased this yield to 0.34 g and potassium limitation to 0.31 g dry cell weight/g n-butanol at a dilution rate of 0.1/h. Under these conditions n-butanol was eliminated from the gas phase by 84%–100%. In the same order of limitations the specific degradation rate ranged from 0.19 g to 0.32 g n-butanol g dry cell weight⁻¹ h⁻¹. The fraction of n-butanol required to satisfy the needs for maintenance energy increased significantly depending on the limiting nutrient. Limitation by n-butanol, phosphate or potassium caused a maintenance requirement of 0.07, 0.16 and 0.34 g n-butanol g dry cell weight⁻¹ h⁻¹, thus showing a fivefold increase. This high demand for the carbon source demonstrated the feasibility of operating a bioscrubber under mineral limitation to reduce biomass formation significantly, and to maintain a high degree of substrate elimination from the gas phase. Received: 22 May 1996 / Received revision: 23 July 1996 / Accepted: 5 August 1996     

Length-based growth,maturity and natural mortality of the cockfish <Emphasis Type="Italic">Callorhinchus callorhynchus</Emphasis> (Linnaeus, 1758) off Coquimbo,Chile

The growth rate, reproductive aspects, and natural mortality of chimaeras and ratfish are poorly known. In this study, life-history parameters for cockfish Callorhinchus callorhynchus (Holocephali—Callorhinchidae) are estimated, which is an important fish resource exploited in Chile. Specimens were sampled from the artisanal fishery captures, from November 2006 to November 2007. The standard length (SL) of males fluctuated between 20 and 62 cm, and between 21 and 70 cm for females. Von Bertalanffy growth parameters were estimated through length-frequency data analysis using MULTIFAN. The length-weight relationship and von Bertalanffy growth parameters were significantly different for males and females, as well as the length at 50% maturity. For males a model with 5 age-classes was the best, with asymptotic length L _∞ = 52 cm SL, growth coefficient K = 0.473 yr⁻¹, and age at length zero t ₀ = −0.690 yrs. For females the best model was represented by 10 age-classes (L _∞ = 70.3 cm SL, K = 0.193 yr⁻¹, t ₀ = −1.158 yrs) in the length-frequency data sets. Length at 50% maturity of males was estimated in 43.7 cm SL, and in 50.2 cm SL for females. The natural mortality rate fluctuated between 0.42 and 0.82 yr⁻¹ for males and between 0.12 and 0.37 yr⁻¹ for females, depending upon the method used. It is concluded that C. callorhynchus is a species with life-history parameters significantly different between males and females, and such differences should be taken into account in future population dynamics analysis.