Gas phase hold up in gas-liquid cocurrent upflow packed bed reactors at low Reynold's number

Experimental measurements of gas phase hold up in two phase gas-liquid cocurrent upflow packed bed reactors have been made at very low gas ((N_Re)_g < 55) as well as liquid ((N_Re)_l < 8) velocities using air-water systems with two different types of packing materials. The gas hold up values thus obtained are correlated in terms of Re_g, Re_l and l, the voidage.     

Variation in propensity to defend by reproductive gall morphs in two species of gall-forming thrips

Summary.Six species of Australian phleaothripine gall forming thrips on Acacia have two morphs. One morph, referred to as a soldier, has reduced antennae and wings and greatly enlarged fore femora, which are thought to be adaptations for gall defence. For most species, female soldier morphs have reduced reproductive output relative to dispersing females and these species have been regarded as eusocial. We examine defensive behaviour of soldier morphs using in situ presentation of gall invading kleptoparasites. We show that the gall-morph of Oncothrips tepperi attack kleptoparasites more often (N=87 interactions, n = 11 attacks) than does the gall-morph of Oncothrips morrisi (N = 231, n = 1). This difference in proclivity for defence is coincident with a lower reproductive output by the gall-morph in O. tepperi compared to O. morrisi. Our results also show an almost complete absence of attack behaviour by the gal l-morph of O. morrisi. Lastly, we show that there is no difference in proclivity for defence between soldier and foundress morphs of O. tepperi. These observations taken together call into question the suitability of the term 'soldier' as applied to the gall-morph of the gall-forming thrips of Australia.     

Empirical correction for PM7 band gaps of transition-metal oxides

A post-calculation correction is established for PM7 band gaps of transition-metal oxides. The correction is based on the charge on the metal cation of interest, as obtained from MOPAC PM7 calculations. Application of the correction reduces the average error in the PM7 band gap from ~3 eV to ~1 eV. The residual error after correction is shown to be uncorrelated to the Hartree–Fock method upon which PM7 is based.

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Graphical Abstract Comparison between calculated band gaps and experimental band gaps for binary oxides. The orange crosses are for corrected PM7 band gaps. Blue squares are uncorrected values. The orange crosses fall closer to the diagonal dashed line, showing an overall improvement of the accuracy of calculated values

     

Photosynthetic induction in saplings of three shade-tolerant tree species: comparing understorey and gap habitats in a French Guiana rain forest

The photosynthetic induction response under constant and fluctuating light was examined in naturally occurring saplings (about 0.5-2 m in height) of three shade-tolerant tree species, Pourouma bicolor spp digitata, Dicorynia guianensis, and Vouacapoua americana, growing in bright gaps and in the shaded understorey in a Neotropical rain forest. Light availability to saplings was estimated by hemispherical photography. Photosynthetic induction was measured in the morning on leaves that had not yet experienced direct sunlight. In Dicorynia, the maximum net photosynthesis rate (A_max) was similar between forest environments (ca 4 µmol m^-2 s^-1), whereas for the two other species, it was twice as high in gaps (ca 7.5) as in the understorey (ca 4.5). However, the time required to reach 90% of A_max did not differ among species, and was short, 7-11 min. Biochemical induction was fast in leaves of Pourouma, as about 3 min were needed to reach 75% of maximum carboxylation capacity (V_cmax); the two other species needed 4-5 min. When induction continued after reaching 75% of V_cmax, stomatal conductance increased in Pourouma only (ca 80%), causing a further increase in its net photosynthesis rate. When fully induced leaves were shaded for 20 min, loss of induction was moderate in all species. However, gap saplings of Dicorynia had a rapid induction loss (ca 80%), which was mainly due to biochemical limitation as stomatal conductance decreased only slowly. When leaves were exposed to a series of lightflecks separated by short periods of low light, photosynthetic induction increased substantially and to a similar extent in all species. Although A_max was much lower in old than in young leaves as measured in Dicorynia and Vouacapoua, variables of the dynamic response of photosynthesis to a change in light tended to be similar between young and old leaves. Old leaves, therefore, might remain important for whole-plant carbon gain, especially in understorey environments. The three shade-tolerant species show that, particularly in low light, they are capable of efficient sunfleck utilization.     

Benchmarking of ONIOM method for the study of NH<Subscript>3</Subscript> dissociation at open ends of BNNTs

The reliability of ONIOM approach have been examined in calculations of adsorption energies, transition structures, change of HOMO-LUMO energy gaps and equilibrium geometries of the interaction between NH₃ and N-enriched (A) or B-enriched (B) open ended boron nitride nanotubes. To these ends, four models of the A or B, with different inner and outer layers have been studied. In addition, various low-levels including, AM1, PM3, MNDO and UFF have been examined, applying B3LYP/6-31 G* in all high-levels. It was shown, that in the case of A, (choosing two atom layers of the tube open-end as inner layer) the results of ONIOM approach are in best agreement with those of the pure density functional theory (DFT) calculations, while their results significantly differ from those of DFT in the case of B in same conditions. All above and population analysis demonstrate that the ONIOM may be a reliable scheme in the study of weak interactions while it is a controversial approach and should be applied cautiously in the case of strong interactions. We also probed the effect of tube length and diameter on the consistency between ONIOM and DFT results, showing that this consistency is independent of the mentioned parameters.     

Structural basis of stereoselectivity in Candida rugosa lipase-catalyzed hydrolysis of secondary alcohols

Lipases are widely used catalysts for highly enantioselective resolution of chiral secondary alcohols. While stereopreference is determined predominantly by the substrate structure, stereoselectivity (enantioselectivity and diastereoselectivity) depends on the atomic details of interactions between substrate and lipase. Experimentally obtained stereoselectivity and activity in the hydrolysis of butanoic acid esters of two secondary alcohols with two neighboring stereocenters by Candida rugosa lipase have been investigated by computer-aided molecular modeling of tetrahedral substrate intermediates in complex with the lipase. Breakdown of these intermediates is considered to be the rate-limiting step. Steric interactions of stereoisomers with the side chain of catalytic histidine led to different orientations of the imidazole. The distance d(H_N)-O_alc) between H_N) of the imidazole side chain of catalytic histidine and the alcohol oxygen of the substrate was identified to correlate with the experimentally determined reactivity order of the four stereoisomers. Modeled distances d(H_N)-O_alc) were short (=1.8 Å) for RR stereoisomers, which were also found to be hydrolyzed most rapidly experimentally; distances d(H_N)-O_alc) were about 2 Å for SS and SR stereoisomers, which were converted at similar rates but at a lower rate than RR stereoisomers; finally, distances d(H_N)-O_alc) for SR stereoisomers were greater than 4 Å, in accordance with very slow conversion of SR stereoisomers.     

Regional and local impact on species diversity – from pattern to processes

The impact of regional factors (such as speciation or dispersal) on the species richness in local communities (S_L) has received increasing attention. A prominent method to infer the impact of regional factors is the comparison of species richness in local assemblages (S_L) with the total number of species in the region (S_R). Linear relations between S_R and S_L have been interpreted as an indication of strong regional influence and weak influence of interactions within local communities. We propose that two aspects bias the outcome of such comparisons: (1) the spatial scale of local and regional sampling, and (2) the body size of the organisms. The impact of the local area reflects the scales of ecological interactions, whereas the ratio between local and regional area reflects the inherent moment of autocorrelation. A proposed impact of body size on the relation is based on the high dispersal and high abundance of small organisms. We predict strongest linearity between S_R and S_L for large organisms, for large local areas (less important ecological interactions) and for sampling designs where the local habitat area covers a high proportion of the regional area (more important autocorrelation). We conducted a meta-analysis on 63 relations obtained from the literature. As predicted, the linearity of the relationship between S_L and S_R increased with the proportion of local to regional sampling area. In contrast, neither the body size of the organisms nor the local area itself was significantly related to the relation between S_L and S_R. This indicated that ecological interactions played a minor role in the shape of local to regional richness plots, which instead was mainly influenced by the sampling design. We found that the studies published so far were highly biased towards larger organisms and towards high similarity between the local and regional area. The proposed prevalence of linear relationships may thus be an artefact and plots of S_L to S_R are not a suitable tool with which to infer the strength of local interactions.     

Optimization of in vitro micropropagation and regeneration for Populus × interamericana and Populus × euramericana hybrids (P. deltoides, P. trichocarpa, and P. nigra)

A rapid and efficient micropropagation method has been established for six European poplar cultivars of economic interest - four Populus 2 interamericana and two Populus 2 euramericana. Using a three-step procedure, we were able to regenerate plantlets from callus and acclimate them within 4 months. In the first step, callogenesis was induced when explants were cultured for 25 days on culture medium supplemented with 10 µM !-naphthaleneacetic acid and 5 µM N⁶(2-isopentenyl)adenine. Bud regeneration followed by shoot elongation was then obtained from callus tissue by combining the cytokinin-like compound thidiazuron with the surfactant Pluronic F-68 at concentrations adjusted for each cultivar. The usefulness of this procedure in the area of genetic engineering is discussed.     

Limitations on photosynthesis of competing individuals in stands and the consequences for canopy structure

The canopy structure of a stand of vegetation is determined by the growth patterns of the individual plants within the stand and the competitive interactions among them. We analyzed the carbon gain of individuals in two dense monospecific stands of Xanthium canadense and evaluated the consequences for intra-specific competition and whole-stand canopy structure. The stands differed in productivity, and this was associated with differences in nitrogen availability. Canopy structure, aboveground mass, and nitrogen contents per unit leaf area (N_area) were determined for individuals, and leaf photosynthesis was measured as a function of N_area. These data were used to calculate the daily carbon gain of individuals. Within stands, photosynthesis per unit aboveground mass (P_mass) of individual plants increased with plant height, despite the lower leaf area ratios of taller plants. The differences in P_mass between the tallest most dominant and shortest most subordinate plants were greater in the high-nitrogen than in the low-nitrogen stand. This indicated that competition was asymmetric and that this asymmetry increased with nitrogen availability. In the high-nitrogen stand, taller plants had a higher P_mass than shorter ones, because they captured more light per unit mass and because they had higher photosynthesis per unit of absorbed light. Conversely, in the low-nitrogen stand, the differences in P_mass between plants of different heights resulted only from differences in their light capture per unit mass. Sensitivity analyses revealed that an increase in N_area, keeping leaf area of plants constant, increased whole-plant carbon gain for the taller more dominant plants but reduced carbon gain in the shorter more subordinate ones, which implies that the N_area values of shorter plants were greater than the optimal values for maximum photosynthesis. On the other hand, the carbon gain of all individual plants, keeping their total canopy N constant, was positively related to an increase in their individual leaf area. At the same time, however, increasing the leaf area for all plants simultaneously reduced the carbon gain of the whole stand. This result shows that the optimal leaf area index (LAI), which maximizes photosynthesis of a stand, is not evolutionarily stable because at this LAI, any individual can increase its carbon gain by increasing its leaf area.     

Electrostatic solvent effects on the conversion of substituted carbonyl oxides to dioxiranes

The effects of substituents (H, CH₃, CN, OCH₃, di-CH₃, and di-CN) on the conversion of carbonyl oxides to dioxiranes have been examined in the gas phase and in solution, with B3LYP/6-31G(d,p). The solvent has been modeled with the SCIPCM method. Optimizations in solution have shown that the geometry of carbonyl oxides and the reaction barriers for their conversion to dioxiranes depend on the characteristics of the substituents. The syn isomers of CH₃ and OCH₃ carbonyl oxides are more stable than their anti counterparts, whereas the conversion of anti substituted carbonyl oxides into dioxiranes is easier for all the substituents. Disubstitution favors the ring-opening reaction of dioxiranes.     

Considerations of correlated fertility between genders on genetic diversity: the Pinus densiflora seed orchard as a model

The correlation between 99 clone female and male fertilities in a first generation seed orchard of Pinus densiflora was studied over 6 years. The effective number of the parent (N_p) and the variance effective population number [N_e^(v)] were used to assess the impact of total (O_T), female (N_f) and male (N_m) fertility variation. A theoretical framework was developed to account for female and male fertility correlations as well as the impact of possible pollen contamination. Total fertility variation was described by the sibling coefficient (O_T: the probability that two genes randomly chosen from the gamete gene pool originate from the same parent), which was further subdivided into N_f and N_m. These parameters were compared under various conditions including the total seed harvest, imposing on equal seed harvest among the orchard's clones and two contamination scenarios (M = 0 and 20%). Fertility variations among females, males and clones were observed within and among years. Sibling coefficients (O_T) were lower, but the effective number of parent (N_p) and variance effective population number (N_e^(v)) were higher in years with moderate female and good male strobilus production. N_p for female and male reproductive outputs varied from 49 to 82 and from 57 to 93, respectively. N_p was higher for males than females. When the crop of the 6 years was pooled, N_p for female, male and the clone were 73, 87 and 85, respectively. The impact of female-male fertility correlation for conditions with no-, positive- and negative-correlations were assessed and their impact on O_T, N_p and N_e^(v) was also evaluated. It was demonstrated that the practice of equal seed harvesting from every clone, or the mixing of seeds from several years, would substantially improve the genetic diversity and the genetic representation of the seed orchard population when a positive correlation between gender fertilities was observed. The relevance of these results to supplemental-mass-pollination was discussed under two cases where equal- and un-equal amounts of pollen from clones were included in the pollen mixes.     

Photosynthetic responses of tree seedlings in grass and under shrubs in early-successional tropical old fields, Costa Rica

Only recently have studies addressed the effect of early-colonizing vegetation on tree seedling survival and growth during secondary succession in tropical old fields, and few studies have elucidated the physiological responses of tree seedlings to different vegetational communities. We compared growth and various photosynthetic parameters for seedlings of four rain-forest tree species, Cedrela tonduzii, Inga punctata, Ocotea whitei, and Tapirira mexicana, growing in areas of pasture grass and shrubs in early-successional abandoned pasture in Costa Rica; in addition, we made measurements for two species in forest gaps. We tested the general hypothesis that early-colonizing shrubs facilitate growth of forest tree seedlings. Specifically, we measured microclimate, growth, CO₂ assimilation, stomatal conductance, photosystem II quantum yield (KPSII), and xanthophyll pigment pools for all seedlings. Photosynthetic flux density (PFD) was higher under grass than shrubs or forest gaps, but was highly variable in each growth environment. For three of the four species, height growth was greatest in the grass compared to the shrubs and forest gaps; growth was similar below grass and shrubs for O. whitei. Photosynthetic capacity, apparent quantum yield, and stomatal conductance did not vary across habitats, but light compensation point and PFD at light saturation tended to be higher in the grass compared to forest and shrub growth environments. Water use efficiency differed across growth environments for three of the species. For plants in ambient PFD and dark-adapted plants, the efficiency of excitation energy transfer through PSII was lowest for plants in the grass compared to shrubs and forest gaps and also differed across species. Measurement of steady-state responses of KPSII to increasing PFD indicated a significant effect of growth environment at low PFD for all species and significant effects at high PFD only for I. punctata. All species exhibited a high degree of midday xanthophyll de-epoxidation in the different growth environments. Xanthophyll pigment pool size on an area basis was highest in the grass compared to shrubs and forest gaps for all four species. The results suggest that shrubs do not provide a facilitative effect for growth or photosynthesis for ~1.5-year-old seedlings of these four species. We conclude that site differences in success of tree seedlings during succession are a result of complex interactions of facilitation and competition and are not simply based on physiological responses to PFD.     

Measurements of buoyancy for some Antarctic notothenioid fishes from the South Shetland Islands

Buoyancy was measured for 258 specimens representing 13 species of adult and sub-adult nototheniids, bathydraconids, and channichthyids from the South Shetland Islands. Measurements were expressed as percentage buoyancy (%B)=W_water/W_air᎒². There were no neutrally buoyant species and mean values for %B were 3.07-6.11%, with channichthyids at the low end and benthic nototheniids and bathydraconids at the high end. All species showed an ontogenetic decrease in %B with increasing body weight. With the exception of Champsocephalus gunnari, there was no sexual dimorphism in %B within this sample. With some exceptions, values for %B were consistent with life-history information. Sub-adult Dissostichus mawsoni were not neutrally buoyant, as are large adults. Notothenia rossii had a significantly lower %B than closely related N. coriiceps. Benthic Gobionotothen gibberifrons had a lower %B than semipelagic Lepidonotothen larseni. Although they exhibit some diversification in life history, the four channichthyids in the sample were similar in %B. Neutral buoyancy is rare in notothenioids and may be confined to a single nototheniid clade.     

Mesozooplankton community structure in the Southern Ocean upstream of the Prince Edward Islands

A meso-scale oceanographic grid survey was conducted during the first cruise of the Marion Offshore Ecosystem Variability Study in the upstream region of the Prince Edward Islands in austral autumn (April/May) 2001. Mesozooplankton samples, collected using a Bongo net (fitted with 200-µm and 300-µm mesh nets), were separated into three size fractions, 200-500 µm, 500-1,000 µm, 1,000-2,000 µm, by reverse filtration. Total surface (depth<5 m) chlorophyll-a concentration during the study ranged between 0.11 and 0.34 µg l^-1 and was always dominated by picophytoplankton (0.45-2.0 µm). Total mesozooplankton abundance and biomass during the survey ranged between 49 and 1,512 ind. m^-3 and between 0.7 and 25 mg Dwt. m^-3, respectively. Throughout the survey, the 200 to 500 µm class numerically dominated the mesozooplankton community, with an average of ~69% (SD=ᆠ.3%). The dominant species in the 200- to 500-µm size fraction were the copepods, Oithona similis, Calanus simillimus and Metridia lucens, and the pteropod, Limacina retroversa. However, in terms of biomass, the 1,000- to 2,000-µm group was predominant, with dry weight values constituting an average of ~66% (SD=ᆞ.2%). The most well-represented species in this group were the carnivorous Euphausia vallentini, Thysanoessa vicina, Sagitta gazellae and Eukrohnia hamata. Three distinct groupings of stations were identified by numerical analysis. The different station groupings identified reflect changes in the relative contributions of the dominant species, as opposed to the presence/absence of species.     

Relations between efficiency of water transport and duration of leaf growth in some deciduous and evergreen trees

Shoot and leaf growth rate as well as shoot hydraulic conductance per unit leaf area (K_SL) were measured on three evergreen (Viburnum tinus L., Prunus laurocerasus L., Laurus nobilis L.) and three deciduous (Corylus avellana L., Juglans regia L., Castanea sativa L.) trees growing under the same environmental conditions. The times required to complete shoot growth (27 days for P. laurocerasus to 51 days for V. tinus) and leaf expansion (24 days for C. sativa to 42 days for C. avellana) were very different among the studied species. These species also differed in K_SL that ranged between 1.5 and 3.5 e-4 kg s^-1 m^-2 MPa^-1 in C. avellana and C. sativa, respectively, with intermediate values recorded in the other species. A strong, negative and statistically significant correlation was found to exist between K_SL and the time required for complete leaf expansion. This suggests that duration of leaf growth is shortened by the high hydraulic efficiency of the shoot. In contrast, no statistically significant relationship was found to exist between K_SL and shoot growth rate. Whether a high leaf growth rate can be interpreted as advantageous to plants or it is only an epiphenomenon of the high efficiency in the vertical water transport is discussed.     

An ab initio study of the formation of alkoxy radicals by reactions of simple alkenes with the OH radical

The formation of ethoxy, propoxy and butoxy radicals in the reactions of ethene, propene, cis- and trans-2-butene with the OH radical has been modeled in the gaseous phase at the MP2/6-31+G(d) level. All the possible reaction pathways have been investigated, and the structures as well as the energetics have been determined. The reactants, prereaction complexes, transition states and products located along the alkene-OH radical reaction coordinates have been discussed thoroughly. The rate determining step for these reactions is the conversion of hydroxyalkyl radicals to alkoxy radicals. The reaction barriers and exothermicities for these small alkenes are more or less identical for the compounds studied. Nevertheless, addition of OH to the central carbon atom of propene is slightly favored kinetically and thermodynamically (1 kcal mol^-1) over the others.     

Shoot δ15N and δ13C values of non-host Brassica rapa change when exposed to ±Glomus etunicatum inoculum and three levels of phosphorus and nitrogen

Glasshouse experiments were conducted to study the response of non-host Brassica rapa and host Sorghum bicolor to inoculation with the arbuscular mycorrhizal fungus (AMF) Glomus etunicatum when given different levels of N (0.9 mmol kg^-1 sand, 2.7 mmol kg^-1 sand, 8.1 mmol kg^-1 sand) and P (3.6 µmol kg^-1 sand, 10.7 µmol kg^-1 sand, 32.0 µmol kg^-1 sand) fertiliser. On both plant species, the presence of G. etunicatum inoculum (+AMF) was associated with significant changes of shoot '¹⁵N values, with +AMF plants having larger average '¹⁵N values than uninoculated plants (-AMF). These values are the largest average differences in shoot '¹⁵N yet recorded for AMF and nutrient effects. B. rapa shoot '¹⁵N average differences ranged from 1.67‰ to 2.70‰, while for S. bicolor they range between 2.07‰ and 4.40‰. For shoot '¹³C only the non-host B. rapa responded to -AMF and added N. Although the harvested dry weight biomass (-35.2% B. rapa; +39.8% S. bicolor) of both plant species responded to AMF inoculation, no direct relationship was observed between isotopic discrimination and growth inhibition for the non-host B. rapa. In this paper we discuss some implications regarding AMF inocula on the basis of our findings and current literature.     

Ab Initio Calculations of Vibrational Frequencies,Potential Functions of Internal Rotations and Vibrational Infrared and Raman Spectra for 3,3,3-Trifluoropropanal

The conformational behavior and structure of 3,3,3,-trifluoropropal have been investigated by utilizing ab initio calculations with the 6-31G^** basis set (valence double zeta basis with polarization functions on all atoms) at the restricted Hartree Fock (RHF), second-order Møller-Plesset perturbation (MP2), and Density Functional (B3LYP) levels. The molecule is predicted to have a cis Û gauche conformational equilibrium. Full optimization of the transition states was performed and the rotational barriers of both the CHO and CF₃ rotors were calculated. Vibrational frequencies were computed at the three levels and the zero-point corrections were included into the calculated asymmetric CHO rotational barrier. Complete vibrational assignments were made on the basis of normal coordinate calculations for both stable conformers of the molecule.     

Plants feed ants: food bodies of myrmecophytic Piper and their significance for the interaction with Pheidole bicornis ants

Several species of Piper (Piperaceae) live in symbiosis with Pheidole bicornis (Formicidae-Myrmicinae) on the southern Pacific slope of Costa Rica. These plants produce small single-celled food bodies (FBs) in leaf domatia, formed by the petiole bases and roofing leaf sheaths. In the present study the dependency of ants on FBs of Piper fimbriulatum as a food source was analysed by comparing the natural abundance of ¹³C and ¹⁵N in ants and FBs. Both '¹³C and '¹⁵N values were very similar between FBs and Pheidole bicornis ants but differed substantially between the plant and other ant species. Therefore we suggest that FBs are a main food source for Pheidole bicornis ants. To strengthen this suggestion, the chemical composition of FBs of four myrmecophytic Piper species was analysed, with special emphasis on the nutritional requirements of inhabiting Pheidole bicornis ants. Standard chemical methods were modified and combined to a novel analysis scheme by which all major FB constituents could be quantified from minute [3-10 mg dry mass (DM)] quantities. Piper FBs mainly consisted of lipids (41-48% of DM) and proteins (17-24% of DM). Soluble carbohydrates and amino acids proved to be quantitatively unimportant. N was predominantly stored as soluble protein and, thus, was easily available to the ants. FBs proved to be a high-energy food source (up to 23 kJ g^-1 DM), with a chemical composition that meets well the nutritional needs of the inhabiting ants.     

Lipids and fatty acids in the copepod Jaschnovia brevis (Jaschnov) and in particulates from Arctic waters

The small, sub-ice copepod Jaschnovia brevis is rich in triacylglycerols, suggesting a feeding behaviour not constrained to the seasonal phytoplankton bloom. The copepod's triacylglycerol reserves contain: the diatom biomarkers 16:1n-7 (23.9%), 20:5n-3 (8.5%) and C16 PUFA (1.3%), the flagellate biomarkers 18:4n-3 (3.7%) and 22:6n-3 (3.3%), and the Calanus copepod biomarkers 20:1n-9 (7.7%) and 22:1n-11 (6.2%). Total lipid from particulates in the water column contained polar lipid (45.0%), wax esters (24.9%) and triacylglycerols (11.2%) as major components. The total lipids in the particulates were rich in 18:1n-9 (31.5%) and 16:0 (21.2%), and relatively rich in 18:0 (7.8%) and 18:2n-6 (9.2%). The triacylglycerols in the particulates contained 16:1n-7 (20.7%), C16 PUFA (4.1%), 18:4n-3 (1.9%), 20:5n-3 (3.6%), 22:6n-3 (1.9%), 20:1n-9 (5.2%) and 22:1n-11 (3.9%). The polar lipids in the particulates contained 16:1n-7 (17.3%), C16 PUFA (7.8%), 18:4n-3 (3.3%), 20:5n-3 (14.5%) and 22:6n-3 (9.6%). The fatty alcohols in the wax esters of the particulates were mainly 16:0 (11.3%), 20:1n-9 (21.1%) and 22:1n-11 (30.6%). The nature of the particulates, their possible origin in living and non-living material, and their role in the nutrition of J. brevis are discussed.