Growth and mortality rates of phytoplankton in the northwestern North Pacific estimated by the dilution method and HPLC pigment analysis

Pigment-based growth rates of phytoplankton and mortality rates due to microzooplankton grazing were estimated using a dilution method combined with high-performance liquid chromatography (HPLC) pigment analysis in the northwestern North Pacific in autumn 1998. The dilution experiments were conducted at different hydrographic stations in both colder and warmer water masses. No significant difference was found between the growth rate of the phytoplankton community (0.38–0.70 day⁻¹; estimated by chlorophyll a) at the colder and warmer water stations, while the mortality rate (0.15–0.88 day⁻¹; estimated by chlorophyll a) tended to be higher at warmer water stations. The combination of estimates of daily chlorophyll a production and particulate organic carbon (POC) production enabled us to assess the carbon to chlorophyll a ratio (C/chl a) of “new” organic matter produced by living phytoplankton. The method provided an implicit value of the C/chl a of in situ living phytoplankton. The rate estimates from taxon-specific pigments suggested a possibility that chlorophyll b-containing green algae were grazed preferentially by microzooplankton during their active growth, and the standing stock of green algae was more strictly controlled by micrograzer than other algal groups such as diatoms. This result is one possible explanation for the fact that blooms of green algae have not been reported in the open ocean, in contrast with diatoms.     

Applications of Satellite Ocean Color Sensors for Monitoring and Predicting Harmful Algal Blooms

The new satellite ocean color sensors offer a means of detecting and monitoring algal blooms in the ocean and coastal zone. Beginning with SeaWiFS (Sea Wide Field-of-view Sensor) in September 1997, these sensors provide coverage every 1 to 2 days with 1-km pixel view at nadir. Atmospheric correction algorithms designed for the coastal zone combined with regional chlorophyll algorithms can provide good and reproducible estimates of chlorophyll, providing the means of monitoring various algal blooms. Harmful algal blooms (HABs) caused by Karenia brevis in the Gulf of Mexico are particularly amenable to remote observation. The Gulf of Mexico has relatively clear water and K. brevis, in bloom conditions, tends to produce a major portion of the phytoplankton biomass. A monitoring program has begun in the Gulf of Mexico that integrates field data from state monitoring programs with satellite imagery, providing an improved capability for the monitoring of K. brevis blooms.     

From silk to satellite: half a century of ocean colour anomalies in the Northeast Atlantic

Changes in phytoplankton dynamics influence marine biogeochemical cycles, climate processes, and food webs, with substantial social and economic consequences. Large‐scale estimation of phytoplankton biomass was possible via ocean colour measurements from two remote sensing satellites – the Coastal Zone Colour Scanner (CZCS, 1979–1986) and the Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS, 1998–2010). Due to the large gap between the two satellite eras and differences in sensor characteristics, comparison of the absolute values retrieved from the two instruments remains challenging. Using a unique in situ ocean colour dataset that spans more than half a century, the two satellite‐derived chlorophyll‐a (Chl‐a) eras are linked to assess concurrent changes in phytoplankton variability and bloom timing over the Northeast Atlantic Ocean and North Sea. Results from this unique re‐analysis reflect a clear increasing pattern of Chl‐a, a merging of the two seasonal phytoplankton blooms producing a longer growing season and higher seasonal biomass, since the mid‐1980s. The broader climate plays a key role in Chl‐a variability as the ocean colour anomalies parallel the oscillations of the Northern Hemisphere Temperature (NHT) since 1948.     

Photosynthetic response of Myriophyllum salsugineum A.E. orchard to photon irradiance, temperature and external free CO2

The photosynthetic capacity of Myriophyllum salsugineum A.E. Orchard was measured, using plants collected from Lake Wendouree, Ballarat, Victoria and grown subsequently in a glasshouse pond at Griffith, New South Wales. At pH 7.00, under conditions of constant total alkalinity of 1.0 meq dm⁻³ and saturating photon irradiance, the temperature optimum was found to be 30–35°C with rates of 140 μmol mg⁻¹ chlorophyll a h⁻¹ for oxygen production and 149 μmol mg⁻¹ chlorophyll a h⁻¹ for consumption of CO₂. These rates are generally higher than those measured by other workers for the noxious Eurasian water milfoil, Myriophyllum spicatum L., of which Myriophyllum salsugineum is a close relative. The light-compensation point and the photon irradiance required to saturate photosynthetic oxygen production were exponentially dependent on water temperature. Over the temperature range 15–35°C the light-compensation point increased from 2.4 to 16.9 μmol (PAR) m⁻² s⁻¹ for oxygen production while saturation photon irradiance increased from 41.5 to 138 μmol (PAR) m⁻² s⁻¹ for oxygen production and from 42.0 to 174 μmol (PAR) m⁻² s⁻¹ for CO₂ consumption. Respiration rates increased from 27.1 to 112.3 μmol (oxygen consumed) g⁻¹ dry weight h⁻¹ as temperature was increased from 15 to 35°C. The optimum temperature for productivity is 30°C.     

Annual biomass and production of epiphytes in three monospecific seagrass communities of Thalassia hemprichii (Ehrenb.) Aschers

The biomass of epiphytes and seagrasses has been measured in relation to leaf age in three monospecific seagrass stands of Thalassia hemprichii (Ehrenb.) Aschers. in Papua New Guinea. From June 1981 through August 1982, biomass values for epiphytes at the three sites ranged from 5 to 70 g ADW m⁻² sediment surface at site 1, from 5 to 14 g ADW m⁻² at site 2, and from 3.5 to 7.0 g ADW m⁻² at the site 3. Annual mean epiphyte biomass values for the different sites were 1.3 g ADW m⁻² leaf surface at site 1, 1.7 g ADW m⁻² leaf surface at site 2, and 1.5 g ADW m⁻² leaf surface at site 3.

The annual mean standing crop of T. hemprichii leaves was highest at site 1 (103 g ADW m⁻². Values for site 2 and site 3 were 60 g ADW m⁻² and 41 g ADW m⁻², respectively.

Production of epiphytes was calculated in three different ways: firstly, by using biomass values for each specific leaf-age group, with corrections for colonization; secondly, by fitting the biomass values with a specific growth curve; and thirdly, by estimated the rate of biomass accumulation. On an area basis, production of epiphytes on leaves of T. hemprichii ranged from 0.55 to 3.97 g ADW m⁻² day⁻¹ at site 1, from 0.17 to 0.73 g ADW m⁻² day⁻¹ at site 2, and from 0.24 to 0.68 g ADW m⁻² day⁻¹ at site 3.     

珠江口横琴岛海域春季海洋浮游生物的初步研究

根据2008年5月在珠江口横琴岛海域的调查采样,本文对该海域的叶绿素a、初级生产力(C)、浮游动、植物进行了初步的研究,分析了浮游动、植物的种类组成、群落结构、数量和生物量等.结果表明,叶绿素a浓度和初级生产力(C)均值分别为5.27 mg·m^-3和123.56 mg·m^-2·d^-1.浮游植物共有111种,以硅藻为主,绝对优势种为中肋骨条藻Skeletonema costatum,调查海域浮游植物平均细胞丰度为6832.75×10⁴cell·m^-3,以近海广布种为主要类群,多样性指数和均匀度均值分别为2.29和0.45.浮游动物共有41种,暖水种沿岸类群种类占大多数,以中华异水蚤Acartiella sinensis为绝对优势种,平均丰度和生物量分别742.25 ind·m^-3和131.12 mg·m^-3,多样性指数和均匀度均值分别为2.54和0.67.     

Morphological and physiological responses of canola (Brassica napus) siliquas and seeds to UVB and CO2 under controlled environment conditions

Combined effects of UVB radiation and CO₂ concentration on plant reproductive parts have received little attention. We studied morphological and physiological responses of siliquas and seeds of canola (Brassica napus L. cv. 46A65) to UVB and CO₂ under four controlled experimental conditions: UVB radiation (4.2 kJ m⁻² d⁻¹) with ambient level of CO₂ (370 μmol mol⁻¹) (control); UVB radiation (4.2 kJ m⁻² d⁻¹) with elevated level of CO₂ (740 μmol mol⁻¹); no UVB radiation (0 kJ m⁻² d⁻¹) with ambient level of CO₂ (370 μmol mol⁻¹); and no UVB radiation (0 kJ m⁻² d⁻¹) with elevated level of CO₂ (740 μmol mol⁻¹). UVB radiation affected the outer appearance of siliquas, such as colour, as well as their anatomical structures. At both CO₂ levels, the UVB radiation of 4.2 kJ m⁻² d⁻¹ reduced the size of seeds, which had different surface patterns than those from no UVB radiation. At both CO₂ levels, 4.2 kJ m⁻² d⁻¹ of UVB decreased net CO₂ assimilation (A_N) and water use efficiency (WUE), but had no effect on transpiration (E). Elevated CO₂ increased A_N and WUE, but decreased E, under both UVB conditions. At both CO₂ levels, the UVB radiation of 4.2 kJ m⁻² d⁻¹ decreased chlorophyll fluorescence, total chlorophyll (Chl), Chl a and Chl b, but had no effect on the ratio of Chl a/b and the concentration of UV-screening pigments. Elevated CO₂ increased total Chl and the concentration of UV-screening pigments under 4.2 kJ m⁻² d⁻¹ of UVB radiation. Neither UVB nor CO₂ affected wax content of siliqua surface. Many significant relationships were found between the above-mentioned parameters. This study revealed that UVB radiation exerts an adverse effect on canola siliquas and seeds, and some of the detrimental effects of UVB on these reproductive parts can partially be mitigated by CO₂.     

Growth, nodulation and nitrate reductase activity in the aquatic legume Neptunia plena (L.) benth. At different external nitrate concentrations

The effects of different external nitrate concentrations (0 (control), 1, 50, 100, 500, 1000 and 20 000 mmol m⁻³) on growth, nodulation and nitrate-reductase activity (NRA) of inoculated Neptunia plena (L.) Benth. were examined.

Plants given 500 and 1000 mmol m⁻³ nitrate had greater (P < 0.05) shoot length, leaf, stem and root dry mass, and carbon and nitrogen contents than the controls and plants given 20 000 mmol m⁻³ nitrate. Nodule number was not significantly affected by nitrate concentration up to 50 mmol m⁻³, but 100 mmol m⁻³ nitrate reduced nodulation by 68% and concentrations above 100 mmol m⁻³ completely inhibited nodule development. Plants given 100–20000 mmol m⁻³ nitrate had a greater nitrate content per g leaf, stem and root dry mass (DM) than controls. Nitrate per g root DM did not increase with external nitrate concentration above 500 mmol m⁻³, but levels in leaf and stem were greater at 20 000 mmol m⁻³ nitrate than at all other concentrations. NRA per g leaf, stem and root fresh mass (FM) was greater for plants given 500–20000 mmol m⁻³ than for controls, but there was no significant increase with nitrate concentration above 500 mmol m⁻³. Substantial proportions of total plant nitrate and NRA were found in both root and shoot over the entire range of external nitrate concentrations given.

Findings for N. plena are compared with data obtained previously for terrestrial legumes.     

A satellite and field portrait of a Karenia mikimotoi bloom off the south coast of Ireland,August 1998

An extensive surface bloom of the dinoflagellate Karenia mikimotoi occurred off southwestern Ireland during August, 1998. The bloom was evident both from remotely sensed satellite ocean colour data and as visibly discoloured water, from the mouth of Bantry Bay around towards Cork, extending some 60 km offshore. The timing of the bloom co-incided with a field survey in the area. This paper compares the surface distributions of chlorophyll and K. mikimotoi concentrations with satellite ocean colour and thermal infra-red sea surface temperature images, from which may be derived the origins of the bloom. It would appear that weak coastal upwelling transported a thermocline population of K. mikimotoi up to the surface in the region of the Fastnet Rock, where it was wind-dispersed eastwards across the northern Celtic Sea.     

Protein-based complex medium design for recombinant serine alkaline protease production

This work reports on the design of a complex medium based on simple and complex carbon sources, i.e. glucose, sucrose, molasses, and defatted-soybean, and simple and complex nitrogen sources, i.e. (NH₄)₂HPO₄, casein, and defatted-soybean, for serine alkaline protease (SAP) production by recombinant Bacillus subtilis carrying pHV1431::subC gene. SAP activity was obtained as 3050 U cm⁻³ with the initial defatted-soybean concentration C_soybean^o=20 kg m⁻³ and initial glucose concentration C_G^o=8 kg m⁻³; whereas, addition of the inorganic nitrogen source (NH₄)₂HPO₄ decreased SAP production considerably. Further increase in SAP production (3850 U cm⁻³) was obtained when sucrose was replaced with glucose at C_sucrose^o=15 kg m⁻³ and C_soybean^o=20 kg m⁻³. Nevertheless, when molasses was replaced with sucrose, the maximum activity was obtained with molasses having 10 kg m⁻³ initial sucrose concentration and C_soybean^o=15 kg m⁻³as 2130 U cm⁻³; moreover, when casein was replaced with defatted-soybean SAP production decreased considerably (ca. 250 U cm⁻³). Thereafter, the effects of inorganic ionic compounds were investigated; and except phosphate, inorganic compounds supplied from defatted-soybean were found to be sufficient for the bioprocess. The highest SAP activity was obtained as 5350 U cm⁻³ in the medium that contained (kg m⁻³): C_soybean^o=20, C_sucrose^o=15, C_Na2HPO4^o=0.021, and C_NaH2PO4^o=2.82, that was 6.5-fold higher than that of the SAP produced in the defined medium. By using the designed complex medium, oxygen transfer characteristics of the bioprocess were investigated; and, Damköhler number that is the oxygen transfer limitation increases with the cultivation time until t=14 h; and, at t>20 h both mass transfer and biochemical reaction resistances were effective. Overall oxygen transfer coefficient varied between 0.010 and 0.044 s⁻¹; volumetric oxygen uptake rate varied between 0.001 and 0.006 mol m⁻³ s⁻¹; and specific oxygen uptake rate varied between 0.0001 and 0.0022 mol kg⁻¹ DW s⁻¹ throughout the bioprocess.     

Carbon exchange and water use efficiency of a growing, irrigated olive orchard

We measured eddy covariance fluxes of CO₂ and H₂O over a flat irrigated olive orchard during growth, in different periods from Leaf Area Index (LAI) of 0.3–1.9; measurements of soil respiration were also collected. The daily net ecosystem exchange flux (F_NEE) was practically zero at LAI around 0.4 or when the orchard intercepted 11% of the incoming daily radiation; at the end of the experiment, with LAI of 1.9 (and the fraction of intercepted daily radiation close to 0.5), F_NEE was around 10 g CO₂ m⁻² day⁻¹. The night-time ecosystem respiration (R_eco), calculated from eddy fluxes in well-mixed night conditions, show a clear but non-linear dependence with LAI; it ranged from 0.05 to 0.15 mg CO₂ m⁻² s⁻¹ (in average), being the lower limit ideally close to the heterotrophic soil respiration at the site. The gross primary production flux (F_GPP) was linearly related to LAI within the LAI range of this experiment (with 11 g CO₂ m⁻² day⁻¹ increments per unit of LAI) and to the fraction of intercepted radiation. The maximum rates of F_GPP (0.75 mg CO₂ m⁻² s⁻¹) were obtained in the summer mornings of 2002, at LAI close to 1.9. F_GPP was strongly modulated by vapour pressure deficit (VPD) through the canopy conductance, even in absence of water stress. Hence, especially in the summer, the maximum rates of carbon assimilation are reached always before noon. The daily course of F_GPP shows a two-phase pattern, first related to irradiance and then to canopy conductance. The water use efficiency (WUE) was, in average, 3.8, 6.3 and 7 g CO₂ L⁻¹ in 1999, 2001 and 2002, respectively, with maxima always in the early morning. Hourly WUE was strongly related to VPD (WUE = −10.25 + 22.52 × VPD^−0.34). Our results suggest that drip irrigated orchards in general, and olive in particular, deserve specific carbon exchange and carbon budget studies and cannot be easily included in other biomes.     

The response of an emergent sedge Bolboschoenus medianus to salinity and nutrients

The potential for nutrient load (30, 100 and 350 g N m⁻² per year) to alter plant performance under saline conditions (control, 4.5, 9 and 13 dS m⁻¹) was examined in the sedge Bolboschoenus medianus. Relative growth rates (RGR) across nutrient loadings ranged from 30.2 to 41.8 mg g⁻¹ per day in controls and were reduced to 20.9–28.5 mg g⁻¹ per day by salinities of 13 dS m⁻¹. Whilst higher nutrient loads generally increased RGR, the response was smaller at higher salinities. Responses to salinity and nutrient load were specific. Nutrient load increased the RGR via increases in the leaf area ratio (LAR). The LAR ranged from 1.9 to 2.1 m² kg⁻¹ across salinity treatments at 30 g N m⁻² per year, and increased to 2.5–2.8 m² kg⁻¹ at 350 g N m⁻² per year. Salinity reduced the RGR via a reduction in the net assimilation rate (NAR). The NAR in control plants ranged from 14.7 to 16 g m⁻² per day across nutrient loadings and decreased to 11–12 g m⁻² per day at 13 dS m⁻¹. Carbon isotope discrimination of leaves decreased by 2–3‰ in response to 13 dS m⁻¹ at the lower nutrient loadings. A prominent response of B. medianus to salinity was a change in biomass allocation from culms to tubers. In contrast, the response to nutrient load was characterised by a shift in biomass allocation from roots to leaves.     

Phytoplankton biomass from continuous plankton recorder data: an assessment of the phytoplankton colour index

A 15 month time-series of simultaneous fluorometric measurementsof chlorophyll a, and phytoplankton cell abundance and a phytoplanktoncolour index (PCI) from continuous plankton recorder (CPR) samplesare compared for the Iberian margin, western Europe. The relationshipsbetween fluorometrically determined chlorophyll, cell abundanceand PCI are all significant, with PCI showing a better relationshipto chlorophyll than cell abundance. This supports previous researchwhich suggests that the PCI is a useful index of phytoplanktonstanding stock and, furthermore, may be a measure of cells thatare not preserved or counted in the routine microscopic processingof CPR samples. The relationship between PCI and chlorophyllappears to vary seasonally, although more extensive data areneeded to quantify this variability. The study also comparesthe PCI and fluorometer data with chlorophyll values obtainedfrom satellite imagery (SeaWiFS) for the Iberian margin. Significantcorrelations exist during the 15 month time-series between thesethree estimates of phytoplankton concentration. This resultdemonstrates that the ~50 year time-series of PCI for the NorthAtlantic can provide valuable information on changes in phytoplanktonstanding stock.     

Ocean color observations of a surface water transport event: Implications for Pseudo-nitzschia on the Washington coast

A persistent patch of high biomass water, associated with the Juan de Fuca Eddy, is often observed in surface chlorophyll a images off the southwest coast of Vancouver Island, Canada. Outbreaks of toxic Pseudo-nitzschia spp. along the Washington, USA, coast are believed to correlate with the transport of waters from Juan de Fuca Eddy southward to Washington beaches. A time series of Sea-viewing Wide Field-of-view Sensor (SeaWiFS) satellite ocean color images from late May 1999 of coastal waters off Washington and Vancouver Island, processed for surface chlorophyll a concentration and spectral remote sensing reflectance, captured a transport event where water from the Juan de Fuca Eddy was transported onto the Washington shelf. Strong upwelling-favorable winds appeared to deform the patch over an 8-day period and move it southward into Washington coastal waters with surface velocities of approximately 8–16 km d⁻¹. SeaWiFS and sea surface temperature imagery showed the local phytoplankton response to wind-driven coastal upwelling restricted to a narrow (10–15 km) region along the Washington coast. Although we did not observe transport of high biomass water originating in the Juan de Fuca Eddy to Washington beaches in May 1999, transport of Pseudo-nitzschia cells could occur following a rapid shift to downwelling-favorable conditions. Tracking the trajectory of surface waters from the Juan de Fuca Eddy by remote sensing could be used to trigger conditional sampling for domoic acid along the Washington coast.     

Characterising the 2002 toxic Karenia concordia (Dinophyceae) outbreak and its development using satellite imagery on the north-eastern coast of New Zealand

In spring 2002 there was a significant outbreak of harmful microalgal bloom (HAB) in Hauraki Gulf on the north-eastern coast of New Zealand. With the exception of only a few sites where there was also a build-up of Noctiluca scintillans, the outbreak was largely associated with an almost monospecific bloom of Karenia concordia. At the peak of this bloom, mortalities of fish and abalone were observed. In areas where Noctiluca cells were found dead they had consumed large numbers of K. concordia cells. Laboratory tests showed cell extracts of K. concordia to be haemolytic and cytotoxic and confirmed that this species was responsible for marine life mortality. Satellite sea surface temperature (SST) data, obtained prior to the mid-October 2002 toxic outbreaks in Hauraki Gulf, showed signs of strong, along-shelf upwelling and also cross-shelf advection of warm, offshore, subtropical water into the Gulf through Jellicoe Channel. Time-series ocean colour data retrieved from the same region showed build-up of very high chlorophyll a level in Hauraki Gulf, virtually in same areas where bloom proportions of K. concordia (up to 3.3 × 10⁷ cells l⁻¹) were recorded. The relationships of this massive bloom to contemporaneous, remotely sensed SST and ocean colour satellite data (SeaWiFS) during the cold phase of ENSO are discussed.     

Ocean annual phytoplankton carbon and new production,and annual export production estimated with empirical equations and CZCS data

Empirical equations are parameterized for use with chlorophyll a, derived from satellite ocean colour data, to calculate phytoplankton carbon production, phytoplankton new production, and export production. For environments in a high variance (HV) pigment statistical class, annual phytoplankton particulate organic carbon production (AIP) is linearly related to annual average in situ chlorophyll a within the near‐surface layer. Linear relations were also obtained between AIP and annual new nitrogen production, and between AIP and particulate organic carbon annually exported from the euphotic zone for environments in that class. We found no relation between AIP and C_SFC, or between the annual production variables, for oceanic environments characterized by low pigment variance (LV). Ratios of export production to AIP, called e, and new production to nitrogen annually used in phytoplankton production, called f, are widely used to express marine food web processes. The trends of these ratios with AIP differ between HV and LV environments. This is a result of differences in the coupling between nitrogen and carbon transfer in pelagic food webs, which contain different organism size classes in HV compared to LV environments. We applied the empirical equations to CZCS data to estimate global new and export production. The HV environments are responsible for about 40% of global ocean annual phytoplankton carbon production and 70% of global ocean annual new and export production.     

The contribution of the deep chlorophyll maximum to primary production in a seasonally stratified shelf sea, the North Sea

Results from extensive cruises in the years 2000 and 2001 throughout distinct ecohydrodynamic regions of the central and southern North Sea are presented and used to generate estimates of gross primary production and new production. An undulating CTD fitted with a fluorometer was towed over a distance of 12,000 kms. Fluorescence data were used to determine the chlorophyll distribution and derive estimates of phytoplankton biomass. These results were combined with estimates of primary production (new and regenerated) from experiments from one cruise in order to estimate gross production for a greater geographical extent. Results from repeat inter-annual transects showed that the strength of the thermocline and the associated deep chlorophyll maximum were variable. However, when the primary production was integrated over the 15–40 m depth, the variability between years was low. While the depth and strength of the deep chlorophyll maximum varied across the region, a deep chlorophyll maximum (DCM) is a consistent and widespread feature of this region at around 30 m depth. In 2001 the calculated average primary production rate in summer for the whole area surveyed was 0.91 g C m^?2 day^?1. This daily production equates to ~130 g C m^?2 for the summer stratified period. In the offshore stratified regions around the Dogger Bank and Eastern Central North Sea primary production of 64 g C m^?2 associated with the deep chlorophyll maximum (15–40 m) accounted for 60 % of total primary production during the summer stratified period (after the spring bloom). Approximately 66 % of new production in these areas occurred in the DCM. This study shows the extent of the DCM in the North Sea and demonstrates its importance in sustaining primary production after the spring bloom.     

Effects of sulfur dioxide on the development of powdery mildew of cucumber

Environment is a major factor that does influence host parasite relationships. Air pollution caused by SO₂ may directly alter the environment around the plant and pathogen. It is hypothesised that plants may respond differently to foliar pathogens in air polluted environments. To test this hypothesis, effects of intermittent exposures of SO₂ at 143, 286 and 571 μg m⁻³ were investigated on the development of powdery mildew of cucumber (Cucumis sativa) caused by Sphaerotheca fuliginea, using pre-, post- and concomitant-inoculation exposures in closed-top chambers. Sulfur dioxide (except 143 μg m⁻³) and the fungus acting alone caused chlorosis and/or necrosis, and mildew colonies on leaves, respectively and both reduced the plant growth and yield of cucumber. Fungus colonization was relatively greater on the plants exposed to 143 μg SO₂ m⁻³, but at the higher concentrations, the colonies were greatly suppressed. Gas injury on fungus-infected plants was also less in the other treatments. Conidia of S. fuliginea collected from exposed plants varied in size. Conidial germination was considerably greater at 143 μg SO₂ m⁻³. This concentration also promoted germination of the conidia exposed on glass slides. Higher concentrations (286 and 571 μg m⁻³), however, suppressed the germination of conidia from exposed plants or exposed on glass slides. The number of fibrosin bodies declined at all the concentrations. Synergistic effects of 143 μg SO₂ m⁻³ and S. fuliginea were recorded on plant growth and yield of cucumber. Sulfur dioxide at 571 μg m⁻³ and powdery mildew infection had an antagonistic effect on plant growth.     

Annual nitrogen budget of a temperate coastal barrier salt-marsh system along a productivity gradient at low and high marsh elevation

An annual nitrogen budget was established for a temperate back barrier salt-marsh system along a productivity gradient at low and high marsh elevation. We measured plant biomass and nitrogen content in three plant compartments to deduce plant N-allocation patterns. Measurements were done along a successional sequence in a salt-marsh system. In addition, N-mineralization, wet and dry atmospheric N-deposition and sediment N-deposition were measured.

Plant-species dominance changed along the successional sequence. In early stages, Elymus farctus and Spergularia media formed a large part of total plant biomass. Festuca rubra and Puccinellia maritima were dominant at intermediate stages, whereas Elymus pycnanthus and Limonium vulgare were dominant at late stages of succession. Shoot biomass was highest in June, whereas litter biomass was highest in September and December. Root biomass formed by far the largest fraction of total plant biomass, especially at a low-marsh elevation.

Wet deposition of nitrate and ammonium was 1.7 g N m⁻² yr⁻¹, whereas throughfall deposition (dry and wet deposition) amounted to 2.1–3.6 g N m⁻² yr⁻¹, and was positively related to the height of an artificial plant canopy. Sediment organic nitrogen deposition rate was 0.3–5.4 g N m⁻² yr⁻¹, and negatively related to marsh elevation. Nitrogen mineralization rate increased from 2.5–2.8 g N m⁻² yr⁻¹ in young marshes towards 8.0–12.7 g N m⁻² yr⁻¹ at older marshes, depending on marsh elevation.

At a low-marsh elevation, plant N-availability depended equally on tidal N, atmospheric N and mineralized N, especially in young marshes, whereas the decomposition pathway became more important in older marshes. Tidal N contributed most to ecoystem N-accumulation rate at early successional stages, whereas atmospheric N was more important at later stages. Tidal influence was low at high-marsh elevation sites. Here, atmospheric deposition was the dominant exogenous nitrogen source both in young and old marshes.     

Anaerobic digestion of solid slaughterhouse waste (SHW) at laboratory scale: Influence of co-digestion with the organic fraction of municipal solid waste (OFMSW)

Mesophilic anaerobic digestion of slaughterhouse waste (SHW) and its co-digestion with the organic fraction of municipal solid waste (OFMSW) have been evaluated. These processes were carried out in a laboratory plant semi-continuously operated and two set-ups were run. The first set-up, with a hydraulic retention time (HRT) of 25 days and organic loading rate (OLR) of 1.70 kg VS m⁻³ day⁻¹ for digestion, and 3.70 kg VS m⁻³ day⁻¹ for co-digestion, was not successful. The second set-up was initiated with an HRT of 50 days and an OLR of 0.9 kg VS m⁻³ day⁻¹ for digestion and 1.85 kg VS m⁻³ day⁻¹ for co-digestion. Under these conditions, once the sludge had been acclimated to a medium with a high fat and ammonia content, it was possible to decrease the HRT while progressively increasing the OLR to the values used in the first set-up until an HRT of 25 days and OLRs of 1.70 and 3.70 kg VS m⁻³ day⁻¹, for digestion and co-digestion, respectively (the same conditions of the digesters failures previously). These digesters showed a highly stable performance, volatile fatty acids (VFAs) were not detected and long chain fatty acids (LCFAs) were undetected or only trace levels were measured in the analyzed effluent. Fat removal reached values of up to 83%. Anaerobic digestion was thus found to be a suitable technology for efficiently treating lipid and protein waste.