Gas-phase chemistry of benzyl alcohol: Reaction rate constants and products with OH radical and ozone

A bimolecular rate constant, k_{OH+Benzyl alcohol}, of (28 ± 7) × 10^?12 cm³ molecule^?1 s^?1 was measured using the relative rate technique for the reaction of the hydroxyl radical (OH) with benzyl alcohol, at (297 ± 3) K and 1 atm total pressure. Additionally, an upper limit of the bimolecular rate constant, k_{O3+Benzyl alcohol}, of approximately 6 × 10^?19 cm³ molecule^?1 s^?1 was determined by monitoring the decrease in benzyl alcohol concentration over time in an excess of ozone (O₃). To more clearly define part of benzyl alcohol's indoor environment degradation mechanism, the products of the benzyl alcohol + OH were also investigated. The derivatizing agents O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) and N,O-bis(trimethylsilyl) trifluoroacetamide (BSTFA) were used to positively identify benzaldehyde, glyoxal and 4-oxopentanal as benzyl alcohol/OH reaction products. The elucidation of other reaction products was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible benzyl alcohol/OH reaction mechanisms based on previously published volatile organic compound/OH gas-phase reaction mechanisms.     

Elevated levels of nitrogen and phosphorus reduce fertilisation success of gametes from scleractinian reef corals

Spawned gametes were collected from colonies of Acropora longicyathus at One Tree Island and Goniastrea aspera at Magnetic Island, Great Barrier Reef, Australia, for use in fertilisation trials. Mean fertilisation rates were significantly reduced compared with controls (P<0.003), when gametes from the branching coral A. longicyathus were exposed to elevated ammonium concentrations at 1 µM and above in one cross (60-64% reduction), and at 100 µM in another cross (16% reduction). Mean fertilisation success of A. longicyathus gametes was also significantly reduced compared with controls in both crosses (P=0.000) at concentrations of 1 µM phosphate and above (35-75% reduction), and at 1 µM ammonium plus 1 µM phosphate and all higher concentrations (68-74% reduction). Similarly, the mean percentage of regular embryos that were developing normally was significantly reduced in most nutrient treatments compared with controls (P=0.000). Fertilisation trials using gametes from the brain coral G. aspera resulted in a significantly lower percentage of regular embryos (P=0.001) and a significantly higher percentage of deformed embryos (P=0.001) developing after exposure to elevated nutrient treatments compared with controls. Mean fertilisation rates for this species were only significantly reduced (P=0.034) in the 50 µM ammonium plus phosphate treatment in one cross (8% reduction), compared with the control. Therefore, ammonium and phosphate enrichment significantly impairs fertilisation success and embryo development in scleractinian reef corals.     

Taxonomic revisions in the marine biflagellate fungi: The ultrastructural evidence

The ultrastructure of the genera Althornia, Aplanochytrium, Japonochytrium, Schizochytrium and Thraustochytrium is described, and all are regarded as members of the new order Thraustochytriales Sparrow. Species considered are Althornia crouchii, Aplanochytrium kerguelensis, Hyalochlorella marina, Japonochytrium sp., Schizochytrium aggregatum, Thraustochytrium kinnei and T. striatum. All but H. marina are, on ultrastructural evidence, related genera, and some speculative suggestions are made about possible interrelationships both between the species discussed, between the Thraustochytriales and Labyrinthulales, and between these two and other major taxa.     

Sinking-rate response of natural assemblages of temperate and subtropical phytoplankton to nutrient depletion

Phytoplankton assemblages were collected during spring blooms in 1982 in Washington State and in Hawaii. Sinking rate responses of these assemblages were examined under nitrate, phosphate, and silicate depletion. Ambient nutrient concentrations, chlorophyll concentrations, photosynthetic rates, sinking rates, and floristic compositions were determined. Under nutrient-replete conditions, the temperate assemblage, composed primarily of large centric diatoms, had a sinking rate of 0.96 m d^-1; sinking rates did not change appreciably over 4 d without nitrate. Without phosphate or silicate, the sinking rates remained constant for 3 d and then increased after biomass indices began to decline. These findings illustrate the potential importance of phosphate or silicate depletion to the sedimentation of spring-bloom diatom populations. The subtropical assemblage, composed primarily of diatoms, coccolithophorids, and dinoflagellates, had an initial sinking rate of 0.22 m d^-1 and did not display substantial sinking rate changes in the absence of nitrate, phosphate or silicate. Floristic data consistently showed a proliferation of pennate diatoms, which had lower settling rates than centric diatoms. Growth and sedimentation patterns indicated a competitive advantage for pennate diatom components of subtropical assemblages; this in turn may limit phytoplankton sedimentation losses in such ecosystems.     

Carbon flow into the end-products of photosynthesis in short and long incubations of a natural phytoplankton population

During a cruise to the eastern Canadian Arctic (Northern Baffin Bay) in the summer of 1980, we took advantage of the 24-h photoperiod to conduct a 32-h time course experiment of ¹⁴C accumulation under natural solar radiation. The degree of non-linearity in the time course was judged against a time-dependent curve of radioactivity constructed by cumulatively adding the amount of ¹⁴C taken up in sequential short (2 h) incubations of plankton held in a replicate bottle but left unlabelled until removed for assay. Departure from linearity was due first to decreasing rates of ¹⁴C incorporation into polysaccharides and then into lipids. There was a close correspondence between ¹⁴C incorporation into proteins in the 32-h incubation and in the sequence of short incubations. These observations are consistent with patterns in utilization of photosynthetic end-products established from laboratory studies of unicellular algal cultures. Based on parallel or independent control experiments, it was judged that complicating factors such as diel light changes, nitrogenous nutrient exhaustion, bottle size effects or inhibitory conterminants in NaH¹⁴CO₃ stock solutions would not seriously affect our interpretation that non-linearity resulted from catabolic loss of radiocarbon.     

Invasion in a diversity hotspot: exotic cover and native richness in the Californian serpentine flora

Exotic species have been observed to be more prevalent in sites where the richness of native species is highest, possibly reflecting variation among sites in resources, propagule supply, heterogeneity, or disturbance. However, such a pattern leaves unclear whether natives at species-rich sites are subject to especially severe impacts from exotics as a result. We considered this question using path models in which relationships between exotic cover and native richness were evaluated in the presence of correlated environmental factors. At 109 sites on serpentine soils across California, USA, exotic cover was positively correlated with total native herbaceous richness and was negatively correlated with the richness of both serpentine-endemic and rare native herbs. However, in path models that accounted for the influences of soil chemistry, disturbance, overstory cover, and regional rainfall and elevation, we found no indication that exotic cover reduced any component of native herb richness. Rather, our results indicated similarities and differences in the conditions favoring exotic, native, endemic, and rare species. Our results suggest that, in spite of some localized impacts, exotic species are not exerting a detectable overall effect on the community richness of the unique native flora of Californian serpentine.     

Saturated uptake kinetics: transient response of the marine diatom Thalassiosira pseudonana to ammonium,nitrate, silicate or phosphate starvation

Changes in the saturated uptake kinetics of the limiting nutrient were followed as Thalassiosira pseudonana (Clone 3 H) batch cultures entered ammonium, nitrate, silicate and phosphate starvation. Cultures starved of ammonium or phosphate developed very high specific uptake capacities over a 24 to 48 h starvation period, due to both decreases in cell quota and increases in uptake rates per cell. In particular, the cell phosphorus quota decreased ca. 8-fold during phosphate starvation and specific uptake rates exceeded 100 d^-1. In contrast, cultures entering nitrate or silicate starvation underwent little or no further cell division, and the uptake capacity declined during starvation. After 24 to 48 h starvation, an induction requirement for uptake of nitrate or silicate was apparent. These responses are consistent with adaptation to the pattern of supply of these nutrients in the field.     

A role forAmanita muscaria L. in the circulation of cadmium and vanadium in a non-polluted woodland

The sporophore of the fungusAmanita muscaria L. contains greatiy elevated levels of cadmium (29.9 g g^–1 dwt) and vanadium (344.9 g g^–1 dwt) in comparison with the soil in a birch woodland (total (HNO₃-extractabie Cd 0.4 g g^–1 dwt, V 11.7 g g^–1 dwt). The significance of this remarkable concentration of normally rare and dispersed elements in terms of their circulation in the woodland has been investigated. Both elements are released from sporophore tissue in a form which can be taken up by a test plant (lettuce), cultivated in the woodland soil amended with different quantities of sporophore tissue, Cadmium levels in all plant tissues were elevated in comparison to the non-amended controls; only root vanadium levels responded to the amendment of the soil. The results are discussed in terms of their significance for the natural cycling of both elements. It is calculated that an abundant population of sporophores could circulate 1.4% of the total cadmium and 0.65% of the total vanadium pool found in the litter layer and 0–5 cm soil horizon in the sampled woodland over a period of 14 days (mean life span of a sporophore).