Role of plankton in the turnover of organic matter on the Great Barrier Reef,Australia

Number, biomass and production of phytoplankton, bacteria, micro- and mesozooplankton and turnover of labile and stable organic matter were measured in waters over some Capricornia round reefs, and over the reefs of Lizard Island. Primary production was 10 to 40 mg C m^–3 d^–1 but was lower over the living reefs. Microbial wet biomass in reef waters varied from 100 to 500 mg m^–3, and production from 4 to 68 mg C m^–3 d^–1, which was commensurable with primary production. The biomass of microzooplankton (ciliates, zooflagellates and larvae) in waters of Lizard Island reefs reached 100–300 mg m^–3. Mesozooplankton biomass at night in reef waters of Heron Island varied from 200 to 800 mg m^–3. Its composition depended upon the tide phase. PB coefficients in bacterioplankton were 0.3 to 1.2 per day. The food demand of bacterioplankton in waters over the reefs was 5 to 20 times higher than the primary phytoplankton production. Labile organic matter (LOM) doubled in waters after it stayed over living reef for several hours. The turnover time of LOM in reef waters was as short as 1–2 weeks.     

Trophic structure and productivity of the lagoonal communities of Tikehau atoll (Tuamotu Archipelago,French Polynesia)

Carbon standing stocks and fluxes were studied in the lagoon of Tikehau atoll (Tuamotu archipelago, French Polynesia), from 1983 to 1988.The average POC concentration (0.7–2000 µm) was 203 mg C m^–3. The suspended living carbon (31.6 mg C m^–3) was made up of bacteria (53%), phytoplankton < 5 µm (14.2%), phytoplankton > 5 µm (14.2%), nanozooplankton 5–35 µm (5.7%), microzooplankton 35–200 µm (4.7%) and mesozooplankton 200–2000 µm (7.9%). The microphytobenthos biomass was 480 mg C m^–2.Suspended detritus (84.4% of the total POC) did not originate from the reef flat but from lagoonal primary productions. Their sedimentation exceeded phytobenthos production.It was estimated that 50% of bacterial biomass was adsorbed on particles. the bacterial biomass dominance was explained by the utilisation of 1) DOC excreted by phytoplankton (44–175 mg C m^–2 day ^–1) and zooplankton (50 mg Cm^–2 day^–1)2) organic compounds produced by solar-induced photochemical reactions 3) coral mucus.50% of the phytoplankton biomass belongs to the < 5 µm fraction. This production (440 mg C m^–2 day^–1) exceeded phytobenthos production (250 mg C m^–2 day^–1) when the whole lagoon was considered.The zooplankton > 35 µm ingested 315 mg C m^–2 day^–1, made up of phytoplankton, nanozooplankton and detritus. Its production was 132 mg C m^–2 day^–1.     

Impact of in vitro Cultivation Conditions on Stress Responses and on Changes in Thylakoid Membrane Proteins and Pigments of Tobacco during ex vitro Acclimation

Four physiologically and phenotypically diversified tobacco (Nicotiana tabacum L. cv. Samsun) plantlet variants had been generated by cultivation on media either lacking or containing sucrose (0 and 3 %, m/v) under two different photon flux densities (PFD), 50 µmol m^–2 s^–1 (LL) and 200 µmol m^–2 s^–1 (HL). Plantlets were transferred into soil without any pre-acclimation and grown either under PFD of 200 µmol m^–2 s^–1 or 700 µmol m^–2 s^–1. Sucrose feeding in vitro resulted in reduced degree and duration of wilting after transfer. The highest readiness for ex vitro acclimation was found in 3 % HL plants, in which changes of photosynthetic apparatus and stress responses were the smallest. On the contrary, the steepest decline of Fv/Fm ratio on the first day after transplantation, doubled chlorophyll content and almost tripled D1/LHC 2 ratio after 7 d of ex vitro growth under 700 µmol m^–2 s^–1 characterized 0 % HL plants, which had suffered chronic photoinhibition in vitro. Remarkably high abscisic acid content at the end of in vitro cultivation and during acclimation as well as increased synthesis of both D1 and LHC 2 proteins even at the end of analyzed acclimation period were found only in 0 % LL plants. Increase of D1/LHC 2 ratio and chlorophyll contents demonstrate that in vitro developed leaves of all plant variants are able to acclimate to new environment. The most surprising result in the whole study is the drop of D1 protein synthesis in all plants on the 3^rd day. Five times decline of photoprotection level of xanthophylls in plants after ex vitro transfer into the same PFD showed stress character of in vitro cultures.     

Denitrification and N2O emission from urine-affected grassland soil

Denitrification and N₂O emission rates were measured following two applications of artificial urine (40 g urine-N m^–2) to a perennial rye-grass sward on sandy soil. To distinguish between N₂O emission from denitrification or nitrification, urine was also applied with a nitrification inhibitor (dicyandiamide, DCD). During a 14 day period following each application, the soil was frequently sampled, and incubated with and without acetylene to measure denitrification and N₂O emission rates, respectively.Urine application significantly increased denitrification and N₂O emission rates up to 14 days after application, with rates amounting to 0.9 and 0.6 g N m^–2 day^–1 (9 and 6 kg N ha^–1 day^–1), respectively. When DCD was added to the urine, N₂O emission rates were significantly lower from 3 to 7 days after urine application onwards. Denitrification was the main source of N₂O immediately following each urine application. 14 days after the first application, when soil water contents dropped to 15% (v/v) N₂O mainly derived from nitrification.Total denitrification losses during the 14 day periods were 7 g N m^–2, or 18% of the urine-N applied. Total N₂O emission losses were 6.5 and 3 g N m^–2, or 16% and 8% of the urine-N applied for the two periods. The minimum estimations of denitrification and N₂O emission losses from urine-affected soil were 45 to 55 kg N ha^–1 year^–1, and 20 to 50 kg N ha^–1 year^–1, respectively.     

Ulva rigida (Ulvales,Chlorophyta) tank culture as biofilters for dissolved inorganic nitrogen from fishpond effluents

Ulva rigida was cultivated in 7501 tanks at different densities with direct and continuous inflow (at 2, 4, 8 and 12 volumes d^–1) of the effluents from a commercial marine fishpond (40 metric tonnes, Tm, of Sparus aurata, water exchange rate of 16 m³ Tm^–1) in order to assess the maximum and optimum dissolved inorganic nitrogen (DIN) uptake rate and the annual stability of the Ulva tank biofiltering system. Maximum yields (40 g DW m^–2 d^–1) were obtained at a density of 2.5 g FW 1^–1 and at a DIN inflow rate of 1.7 g DIN m^–2 d^–1. Maximum DIN uptake rates were obtained during summer (2.2 g DIN M^–2 d^–1), and minimum in winter (1.1 g DIN m^–2 d^–1) with a yearly average DIN uptake rate of 1.77 g DIN m^–2 d^–1 At yearly average DIN removal efficiency (2.0 g DIN m^–2 d^–1, if winter period is excluded), 153 m² of Ulva tank surface would be needed to recover 100% of the DIN produced by 1 Tm of fish.Abbreviations DIN= dissolved inorganic nitrogen (NH _inf4 ^sup+ + NO _inf3 ^sup– + NO _inf2 ^sup– ); - FW= fresh weight; - DW= dry weight; - PFD= photon flux density; - V= DIN uptake rate     

Benithic-pelagic coupling of nutrient metabolism along an estuarine eutrophication gradient

The shallow, brackish (11–18% salinity) Roskilde Fjord represents a eutrophication gradient with annual averages of chlorophyll, ranging from 3 to 25 mg chl a m^–3. Nutrient loadings in 1985 were 11.3–62.4 g N m^–2 yr^–1 and 0.4–7.3 g P m^–2 yr^–1. A simple one-layer advection-diffusion model was used to calculate mass balances for 7 boxes in the fjord. Net loss rates varied from –32.2 to 17.9 g P m^–2 yr^–1 and from –3.3 to 66.8 g N m^–2, corresponding to 74% of the external P-loading and 88% of the external N-loading to the entire estuary.Gross sedimentation rates measured by sediment traps were between 7 and 52 g p m^–2 yr^–1 and 50 and 426 g N M^–2 yr^–1, respectively. Exchangeable sediment phosphorus varied in annual average between 2.0 and 4.8 g P m^–2 and exchangeable sediment nitrogen varied from 1.9 to 33.1 g N m–1. Amplitudes in the exchangeable pools followed sedimentation peaks with delays corresponding to settling rates of 0.3 m d^–1. Short term nutrient exchange experiments performed in the laboratory with simultaneous measurements of sediment oxygen uptake showed a release pattern following the oxygen uptake, the changes in the exchangeable pools and the sedimentation peaks.The close benthic-pelagic coupling also exists for the denitrification with maxima during spring of 5 to 20 mmol N m^–2 d–1. Denitrification during the nitrogen-limited summer period suggests dependence on nitrification. Comparisons with denitrification from other shallow estuaries indicate a maximum for denitrification in estuaries of about 250 µmol N m^–2 h^–2 achieved at loading rates of about 25–125 g N m^–2 yr^–1.     

Application of N-15 dilution for simultaneous estimation of nitrification and nitrate reduction in soil-water columns

Nitrification and denitrification rates were estimated simultaneously in soil-floodwater columns of a Crowley silt loam (Typic Albaqualfs) rice soil by an¹⁵N isotopic dilution technique. Labeled NO ₃ ^– was added to the floodwater of soil-water columns, half were treated with urea fertilizer. The (NO ₃ ^– +NO ₂ ^– )–N and (NO ₃ ^– +NO ₂ ^– )–N concentrations in the floodwater were measured over time and production and reduction rates for NO ₃ ^– calculated. Nitrate reduction in the urea amended columns averaged 515 mol N m^–2h^–1 and nitrification averaged 395 mol N m^–2h^–1 over the 35–153 d incubation. The nitrification rate for 4–19 d sampling period (1,560 mol N m^–2h^–1) in the urea amended columns was almost 9 times greater than the reduction rate (175 mol N m^–2h^–1) over the same period. Without the addition of urea the NO ₃ ^– production rate averaged 32 mol N m^–2h^–1 and reduction 101 mol N m^–2h^–1.     

Production,Respiration, and Overall Carbon Balance in an Old-growth <Emphasis Type="Italic">Pseudotsuga</Emphasis>-<Emphasis Type="Italic">Tsuga</Emphasis> Forest Ecosystem

Ground-based measurements of stores, growth, mortality, litterfall, respiration, and decomposition were conducted in an old-growth forest at Wind River Experimental Forest, Washington, USA. These measurements were used to estimate gross primary production (GPP) and net primary production (NPP); autotrophic respiration (R_a) and heterotrophic (R_h) respiration; and net ecosystem production (NEP). Monte Carlo methods were used to calculate uncertainty (expressed as ± 2 standard deviations of 200–400 calculations). Live carbon (C) stores were 39,800 g C m^–2 (34,800–44,800 g C m^–2). The store of C in detritus and mineral soil was 22,092 g C m^–2 (20,600–23,600 g C m^–2), and the total C stores were 61,899 g C m^–2 (56,600–67,700 g C m^–2). Total NPP was 597 g C m^–2 y^–1 (453 to 741 g C m^–2 y^–1). R_a was 1309 g C m^–2 y^–1 (845–1773 g C m^–2 y^–1), indicating a GPP of 1906 g C m^–2 y^–1 (1444–2368 g C m^–2 y^–1). R_h, including the respiration of heart rots in tree boles, was 577 g C m^–2 y^–1 (479–675 g C m^–2 y^–1). Long-term NEP was estimated to be +20 g C m^–2 y^–1 (–116 to +156 g C m^–2 y^–1), indicating this stand might be a small sink. These estimates contrast with the larger sink estimated at the same site using eddy-flux methods. Several hypotheses to explain this discrepancy were explored, including (a) undetected biomass increases, (b) underestimates of NPP, (c) unmeasured losses, and (d) a temporal mismatch between the two sets of measurements. The last hypothesis appears the most likely.     

A comparison of oxygen,nitrate, and sulfate respiration in coastal marine sediments

Aerobic respiration with oxygen and anaerobic respiration with nitrate (denitrification) and sulfate (sulfate reduction) were measured during winter and summer in two coastal marine sediments (Denmark). Both aerobic respiration and denitrification took place in the oxidized surface layer, whereas sulfate reduction was most significant in the deeper, reduced sediment. The low availability of nitrate apparently limited the activity of denitrification during summer to less than 0.2 mmoles NO ₃ ^– m^–2 day^–1, whereas activities of 1.0–3.0 mmoles NO ₃ ^– m^–2 day^–1 were measured during winter. Sulfate reduction, on the contrary, increased from 2.6–7.6 mmoles SO ₄ ^2– m^–2 day^–1 during winter to 9.8–15.1 mmoles SO ₄ ^2– m^–2 day^–1 during summer. The aerobic respiration was high during summer, 135–140 mmoles O₂ m^–2 day^–1, as compared to estimated winter activities of about 30 mmoles O₂ m^–2 day^–1. The little importance of denitrification relative to aerobic respiration and sulfate reduction is discussed in relation to the availability and distribution of oxygen, nitrate, and sulfate in the sediments and to the detritus mineralization.     

Optimization of eicosapentaenoic acid production byPhaeodactylum tricornutumin the flat panel airlift (FPA) reactor

Biomass and eicosapentaenoic acid (EPA) productivities were investigated in a flat panel airlift loop reactor ideally mixed by static mixers. Growth with ammonium, urea and nitrate as nitrogen source were performed at different aeration rates. Cultures grew on ammonium but the decay of pH strongly inhibited biomass increase. On urea biomass productivity reached 2.35 g L^–1d^–1at an aeration rate of 0.66 vvm (24 h light per day, 1000 mol photon m^–2s^–1). Aeration rates between 0.33 vvm and 0.66 vvm and maximal productivities on urea were linearly dependent. Productivity on nitrate never exceeded 1.37 g L^–1d^–1. In the range of maximum productivity photosynthesis efficiency of 10.6% was reached at low irradiance (250 mol photon m^–2s^–1). Photosynthesis efficiency decreased to 4.8% at 1000 mol photon m^–2s^–1. At these high irradiances the flat panel airlift reactor showed a 35% higher volume productivity than the bubble column. At continuous culture conditions the influence of CO₂concentration in the supply air was tested. Highest productivities were reached at 1.25% (v/v) CO₂where the continuous culture yielded 1.04 g L^–1d^–1(16 h light per day, 1000 mol photon m^–2s^–1). The average EPA content amounted to 5.0% of cell dry weight, that resulted in EPA productivities of 52 mg L^–1d^–1(continuous culture, 16 h light per day) or 118 mg L^–1d^–1(batch culture, 24 h light per day).     

The influence of coastal upwelling on the distribution of Calanus chilensis in the Mejillones Peninsula (northern Chile): implications for its population dynamics

A field experiment was carried out in October 1998 during active upwelling in a coastal area off the Mejillones Peninsula (23° S). Zooplankton was sampled at day and night, during two subsequent days at 4 stations inside and outside of the upwelling plume. Three depth strata were sampled: 0–20 m, 20–80 m and 80–200 m. Oceanographic data were obtained in a grid of 23 stations using a CTDO, a fluorometer and a Doppler current meter. Calanus chilensis was mostly represented by late stages, i.e. copepodid C5 and adult males and females. There were no day/night effects on vertical distribution, and abundance was significantly higher inside the upwelling plume in the upper 20-m layer at nearly 14 ind. m^–3, compared to ca. 5 ind. m^–3 outside the upwelling plume. Temperature at 10 m depth and biomass, estimated from stage numbers and their mean dry weights, were used to estimate growth and daily production of Calanus at temperature-dependent rates. The potential loss of biomass from the upwelling center because of advection in the upwelling plume was estimated from current data in the Ekman layer and biomass density. The mean cross-shelf component of the current was estimated at 10.4 km d^–1 within the upwelling plume. This yielded a loss of biomass of 9.7 mg dry weight m^–2 . Production, estimated by a temperature-dependent approach, ranged between 44 and 35 mg dry weight m^–2 d^–1, at mean temperatures of 14.6 °C and 15.8 °C inside and outside of the upwelling plume respectively. Within the plume, as much as 22% of daily production may be advected offshore. However, a higher concentration of biomass in the upwelling plume allowed a greater production compared to surrounding areas. A mass balance approach suggests that advective losses may not have a major impact on the C. chilensis population, because of very high daily production at temperature-dependent rates.     

Simultaneous removal of benzene, toluene and xylenes mixture by a constructed microbial consortium during biofiltration

A bacterial consortium with complementary metabolic capabilities was formulated and specific removal rates were 0.14, 0.35, 0.04, and 0.39 h^–1 for benzene, toluene, o-xylene, and m,p-xylene, respectively. When immobilized on a porous peat moss biofilter, removal of all five (= BTX) components was observed with rates of 1.8–15.4 g m^–3 filter bed h^–1. Elimination capacities with respect to the inlet gas concentrations of BTX and airflow rates showed diffusive regimes in the tested concentration range of (0.1–5.3 g m^–3) and airflow (0.55–1.82 m³ m^–2 h^–1) except for o-xylene which reached its critical gas concentration at 0.3 g m^–3.     

Plankton and primary productivity of Lake Manzala,Egypt

Primary production and distribution and abundance of phyto- and zooplankton of lake Manzala were investigated from June 1985 to June 1986.Primary production varied from 4.1 to 28.7 g O₂ m^–2 d^–1 with the highest values 24.2 and 28.7 g O₂ m^–2 d^–1 recorded in the eastern and southern sectors and the lowest value 4.1 g O₂ m^–2 d^–1 recorded in the northern sector. The seasonal mean production for the lake was estimated at 13.3 g O₂ m^–2 d^–1.Mean phytoplankton abundance ranged from 32.7 10⁷ to 76.1 10⁷ cells m^–3 with a mean value of 48.10⁷ cells m^–3. Diatoms were the dominant phytoplankton group comprising 52 to 90 % by number. The greatest relative abundance (87 to 90%) was recorded in the southern sector.Mean zooplankton abundance ranged from 30.1 10³ to 44.4 10³ organisms m^–3 in the eastern sector to 5.5.10³ in the northern sector. In response of eutrophication, the species composition changed significantly over the last 20 years. Cladocerans represented less than 1% of zooplankton during 1959/60, but 75% in 1985/86. Rotifers constituted 40% in 1959/60, and only 1% in 1985/86. Cirriped larvae declined from 21% to 1%.     

Continuous vs slug loading of downflow stationary fixed film reactors digesting piggery waste

Downflow stationary fixed film reactors successfully digested piggery waste at retention times down to 2.6 days either loaded continuously or once-a-day. Daily methane production rates of up to 2.6 m³/m³ were recorded for both loading methods. The rate for the slug loaded reactor peaked within 2–6 hours after being loaded.     

Modelling the recovery of hypertrophic L. Glumsø (Denmark)

Diversion of sewage from L. Glumsø reduced phosphorus loading from 6.0 g P.m^–2.yr^–1 to 1.6 g P.m^–2.yr^–1. Chlorophyll levels during summer were reduced from 6–800 mg Chl.m^–3 to about 200 mg Chl.m^–3 mainly by extended periods with phosphorus limitation. Internal phosphorus loading was significant in the first 2 years after nutrient reduction. Predictions of the recovery were made by both simple, empirical models and with complex, dynamic model versions. The actual responses of L. Glumsø were compared with both previously published predictions and predictions made with improved model versions. Objective functions of 0.18 and global correlation coefficients of 0.89 could be achieved.     

The ecology of Lake Nakuru (Kenya)

Summary Abiotic factors, standing crop and photosynthetic production were studied in the equatorial alkaline-saline closed-basin Lake Nakuru (cond. 10,000–160,000 S). Meteorological conditions and abiotic factors offer suppositions for a high primary productivity: mean solar radiation is 450–550 kerg·cm^-2·s^-1, with little seasonal variation, regular winds circulate the lake every day and nutrient concentrations are usually high (>100 g P–PO₄·l^-1). Oxygen concentrations near sediments were <1 gO₂·m^-3 for at least 6 h·d^-1 in 1972/73, resulting in a release of 45 mg P–PO₄·m^-2·d^-1. Attenuation coefficients vary from 3.6–16.5 according to algal densities and mean depth from 0–400 cm. Algal biomass was 200 g·m^-3 (d.w.) in 1972/73, due to a lasting Spirulina platensis bloom (98.5% of algal biomass). In 1974 algal biomass suddenly dropped to 50 g·m^-3 (d.w.). Spirulina and several consumer organisms almost vanished, but coccoid cyanobacteria, Anabaenopsis and diatoms increased. Several causes for this change in ecosystem structure are discussed. The use of the light/dark bottle method to measure photosynthetic production in eutrophic alkaline lakes is discussed and relevant experiments were done. Oxygen tensions of 2–35 gO₂·m^-3 do not influence primary production rates. Net photosynthetic rates (mgO₂·m^-3·h^-1; photosynthetic quotient=1.18) reached 12–17.7 in 1972/73 and 2–3 in 1974, but vertically integrated rates were only 1–1.4 in 1972/73 and 0.8 in 1974, and daily net photosynthetic rates (gO₂·m^-3·24 h^-1) 3.5 in 1972/73 and 1 in 1974. 50% of areal rates were produced within the 10 most productive cm of the depth profile. The disproportion between high algal standing crops and relatively low production rates is due to self-shading of the algae, reducing the euphotic zone to 35 cm in 1972/73 and 77 cm in 1974. Efficiency of light utilization is 0.4–2%, varying with time of day and phytoplankton density. In situ efficiencies show an inverse relationship to light intensities. Photosynthetic rates of L. Nakuru remain within the range of other African lakes (0.1–3 gO₂·m^-2·h^-1). The relation of O₂ produced/Chl a of the euphotic zone is 50% lower then in tropical African freshwater lakes and conforms to lakes of temperate regions.     

Net primary productivity of two mangrove forest stands on the northwestern coast of Sri Lanka

Productivity studies were carried out from September, 1985 to August, 1987 in two mangrove stands, i.e. estuarine and island fringing, in Dutch bay, a lagoon situated on the northwestern coast of Sri Lanka. Net above-ground primary productivity was measured by monitoring litterfall and above-ground biomass increment. The average annual rate of litterfall in the estuarine and island-fringing mangrove stands are 588.14 g m^–2 (approximately 6 t ha^–1) and 407.33 g m^–2 (approximately 4 t ha^–1) respectively. The average annual rates of above ground woody growth are 614.74 g m^–2 (approximately 6 t ha^–1) in the estuarine stands and 286.8 g m^–2 (approximately 3 t ha^–1) in the island-fringing mangrove stands. Hence estuarine mangrove stands record a higher annual rate of above-ground net primary production (NPP; 1207.88 g m^–2 or approximately 12 t ha^–1) than the fringing mangrove stands (694.22 g m^–2); approximately 7 t ha^–1). The annual rate of NPP in the water front zones of the stands (1300.47 g m^–2 in the estuarine stands and 874.56 g m^–2 in the fringing stands) are greater than those in the back-mangrove zones (115.28 g m^–2 in the estuarine stands and 513.88 g m^–2 in the island-fringing stands). These variations may be attributed to the differences in tidal flushing and influence of freshwater in the two localities.     

Effects of aluminum,iron, oxygen and nitrate additions on phosphorus release from the sediment of a Danish softwater lake

The effects of oxygen, aluminum, iron and nitrate additions on phosphate release from the sediment were evaluated in the softwater Lake Vedsted, Denmark, by a 34-day experiment with undisturbed sediment cores. Six treatments were applied: (1) Control - O₂ (0–20% saturation), (2) O₂ (100% saturation) (3) Al³⁺ – O₂, (4) Fe³⁺ + O₂, (5) Fe³⁺ – O₂, and (6) NO₃ ^– – O₂. Al₂(SO₄)₃*18 H₂O and FeCl₃*4H₂O were added in amounts that theoretically should immobilize the exchangeable P-pool in the top 5 cm of the sediment, while sodium nitrate concentrations were increased to 5 mg N l^–1. The four treatments with metals or NO₃ ^– reduced the P efflux from the sediment significantly as compared to the suboxic control treatment. Mean accumulated P-release rates for suboxic treatments with Al³⁺, Fe³⁺, and NO₃ ^– were: –0.27 mmol m^–2 (st. dev = 0.02 mmol m^–2, N = 5), 0.58 mmol m^–2 (st. dev = 0.30 mmol m^–2, N = 5) and 1.40 mmol m^–2 (st. dev = 0.14 mmol m^–2, N = 5), respectively. The oxic treatment with Fe³⁺ had a P efflux of 0.36 mmol m^–2 (st. dev = 0.08 mmol m^–2, N = 5). The two highest P-release rates were observed in the control treatment and the treatment with O₂ (14.50 mmol m^–2 (st. dev = 3.90 mmol m^–2, N = 5) and 2.31 mmol m^–2 (st. dev = 0.80 mmol m^–2, N = 5), respectively). In order to identify changes in the P and Fe binding sites in the sediment as caused by the treatments, a sequential P extraction procedure was applied on the sediment before and after the efflux experiment. Addition of O₂, Fe³⁺ and NO₃ ^– to the sediment increased the amounts of oxidized Fe³⁺ and P_BD. Al³⁺ addition resulted in a lower fraction of P_BD but a correspondingly higher fraction of Al-bound P. Addition of Al³⁺ decreased the Fe-efflux from the suboxic sediment as well as the amount of oxidized Fe³⁺ in the sediment. This questions the use of Al compounds that contain sulfate because of the possible formation of FeS, which will restrict upward migration of Fe²⁺ and the formation of new Fe-oxides in the surface sediment. Instead, we suggest the use of AlCl₃ for lake restoration purposes.     

Growth characteristics of Sanguinaria canadensis L. Cell suspensions and immobilized cultures for production of benzophenanthridine alkaloids

Summary Sanguinaria canadensis L. plants were harvested from a local forest and calli were initiated from leaf explants. The production of benzophenanthridine alkaloids (i.e. sanguinarine, sanguilutine, sanguirubine, chelerythrine, chelilutine and chelirubine) by S. canadensis cell grown in modified B5 and IM2 media was compared to the alkaloid content of rhizomes. Sanguinarine accounted for approximately 80% of the total alkaloid content of cultured cells (1.3%,g g^–1) while sanguinarine and sanguirubine accounted for 70% of rhizome alkaloids (9.0%, g g^–1). Sanguinarine, chelirubine and chererythrine were the only known alkaloids detected in cultured S. canadensis cells. Maximum alkaloid production of cultures performed using B5 medium, containing half the original nitrate concentration, was observed following extracellular nitrate and sugar depletion. The scale-up of this culture was successfully performed in a 2-1 immobilization bioreactor. The consumption of sugar and nitrate as well as the oxygen (OTR) and carbon dioxide (CTR) transfer rates of the immobilized cell culture were monitored for 15 days. The maximum sugar and nitrate consumption rates were 1.8 g l^–1 per day and 2.3 mm per day respectively. The maximum OTR and CTR of the immobilized cell culture were 0.8 mmol O₂ l^–1 h^–1 and 0.95 mmol CO₂ l^–1 h^–1 respectively. The sanguinarine yield of this culture reached 1.0% based on biomass dry weight (g g^–1 dw) by day 15.     

New cell recycle ethanol fermentation with periodic cleaning of filter with gas

High ethanol productivities were obtained by cell recycle cultures of yeast and bacterial strains at a dry cell concentration of 200 kg cells m^–3 using a new membrane bioreactor system. The filtration rates of the cultures were stabilized by removing the microbial cake on the filter with periodic back flows of the fermentation gas through the filter. For instance, the filtration flux of 0.023 m³m^–2h^–1 was maintained for 30 h with the periodic cleaning of the filter, whereas it decreased at a half time of 2 h without the cleaning. Ethanol productivity, ethanol concentration and filtration flux attained were: 68.7 kg/(m³ · h), 62.7 kg/m³ and 0.029 m³m^–2h^–1 for Saccharomyces carlsbergensis, LAM1068, the respective values for Zymomonas mobilis, ZM4, were: 93.7, 33 5 and 0.074.