Nutrient Enhanced Biodegradation of Crude Oil in Tropical Salt Marshes

Tropical salt marshes in Louisiana are at risks ofaccidental oil spills and remediation of these ecosystemsis mainly limited to natural biodegradation due tophysical sensitivity of the ecosystems. This studyinvestigated both intrinsic and nutrient enhanced ratesof crude oil degradation in core studies. In addition,loading rates of nitrogen and optimal porewater nitrogenconcentrations were determined. Nitrogen additionsincreased biodegradation rates of some alkanes andpolycyclic aromatic hydrocarbons (PAHs). Addition ofNH₄ ⁺-N increased zero-order mineralizationconstants of labeled hexadecane and phenanthrene up to15.4–19.2% (Fourchon marsh) and 56.2% (Ugly Shack Bayoumarsh) and rates of total carbon dioxide production up to14.0–33.1% (Fourchon marsh) and 3.0% (Ugly Shack Bayoumarsh), respectively. Efficient biodegradation of crudeoil was achieved when NH₄ ⁺ was applied at theloading rate of 28.3–56.6 g N m^-2 producing porewaterconcentration at the level of 80–450 mg NH₄ ⁺-N L^-1. No significant lag time was observed indicating thatnitrogen application directly stimulates biodegradationof crude oil in tropical salt marshes in Louisiana.     

Human-predator-prey conflicts: ecological correlates, prey losses and patterns of management

Conflicts between humans and predators are the product of socio-economic and political landscapes and are particularly controversial because the resources concerned have economic value and the predators involved are high profile and often legally protected. We surveyed the current literature for information on ecological and social factors common to human-predator-prey conflicts. We used this information to examine whether losses to predators and patterns of investment in husbandry could be linked to these factors. We found that livestock losses to predators were low and were negatively associated with net primary productivity and predator home range sizes, but were not affected by predator density, methods of husbandry or human population density. While there was no effect of husbandry on losses, variation in husbandry was explained by net primary productivity, predator density and percentage of stock killed by predators. Inconsistent and sparse data across conflicts may have limited our ability to identify important factors and resolve patterns, and suggests that there is no reliable or consistent framework for assessing and managing human-predator conflicts that involve game and livestock species. Our approach highlights the type of data that could be very informative to management if collected across a range of cases and habitats.     

Conservation implications of the distribution of genetic diversity at different scales: a case study using the marsh fritillary butterfly (Euphydryas aurinia)

In the UK, Euphydryas aurinia exists in fragmented habitat patches, and undergoes population fluctuations as a result of a larval parasitoid. Its range is declining in the UK and conservation is thought to require a landscape approach since populations spread over large areas in some years and contract to core breeding patches in others. We examined populations at a range of geographic scales using allozyme electrophoresis to look for evidence of gene flow and differences in genetic diversity among populations. Nationally, our F_ST value was 0.1542 but between population groups within the suspected colonisation range of the butterfly (ca. 20 km), F_ST values were not significantly different from zero. Genetic diversity in terms of number of alleles and heterozygosity was reasonably high in natural populations (H_e=0.267) but low in an introduced, isolated population. We infer that migration between closely spaced subpopulations (in a metapopulation) maintains a high genetic effective population size (large number of individuals in a population that contribute genes to the next generation) which offsets any local reductions in population numbers due to stochastic extinctions or parasitoid effects. We therefore conclude that effective conservation of the species must seek to provide networks of suitable habitat for groups of subpopulations, rather than maintaining habitat for isolated populations.     

Monitoring chemical and physical changes during thermal flavor generation

On-line techniques were developed to monitor chemical and physical changes occurring during the heating of skim milk powder (SMP). Atmospheric pressure chemical ionization mass spectrometry (APCIMS) followed the generation and release of volatile compounds from SMP in a packed-bed reactor. Operating conditions were optimized to avoid condensation of high boiling compounds such as maltol, and the system was highly reproducible (CV < 7%). Differential scanning calorimetry (DSC) of SMP identified a potential glass transition at an onset temperature of 67.9 degrees C and a series of exothermic events that were related to different stages of the Maillard reaction. No lactose crystallization was found after heating. Using a heated stage reflectance FTIR device, spectra were obtained at different temperatures. Analysis of the data showed a correlation between the intensity ratio at wavenumbers 1017 and 1064 cm(-1) and the glass transition measured by DSC. This FTIR system was not sensitive enough to detect Maillard intermediates. Combining data from the three techniques provides a fuller picture of the physical changes during the Maillard reaction and their effects on the chemical reactions.     

Hay strewing, brush harvesting of seed and soil disturbance as tools for the enhancement of botanical diversity in grasslands

Since the middle of the last century agricultural intensification within Europe has led to a drastic decline in the extent of botanically diverse grasslands. Whilst measures to enhance the diversity of agriculturally-improved grasslands are in place, success has often been limited. One of the primary factors limiting success is the paucity of sources of propagules of desirable species in the surrounding landscape. The restoration of two contrasting grassland types (lowland hay meadow and chalk grassland) was examined using a replicated block experiment to assess the effectiveness of two methods of seed application (hay strewing and brush harvesting) and two methods of pre-treatment disturbance (power harrowing and turf stripping). The resulting changes in botanical composition were monitored for 4 years. Seed addition by both methods resulted in significant temporal trends in plant species composition and increases in plant species richness, which were further enhanced by disturbance. Power harrowing increased the effectiveness of the seed addition treatments at the lowland hay meadow site. At the chalk grassland site a more severe disturbance created by turf stripping was used and shown to be preferable. Whilst both hay strewing and brush harvesting increased plant species richness, hay strewing was more effective at creating a sward similar to that of the donor site. Soil disturbance and seed application rate at the recipient site and timing of the hay cut at the donor site are all factors to be considered prior to the commencement of restoration management.     

Ferulic acid crosslinks in asparagus cell walls in relation to texture

Post-harvest toughening of asparagus spears is associated with a large increase in monomeric and diferulic acids in the cell walls of stem tissues. The purpose of this study has been to investigate the distribution of these phenolic components among cell wall polymers and the role they play in the formation of associated pectic-xylan-phenolic complexes in relation to post-harvest toughening. The phenolic esters are found in all the extractable polysaccharide fractions, particularly the 0.5 M KOH fraction, as well as the insoluble cellulose-rich residue. The storage-related increase occurs in all fractions but is most prominent in the 0.5 M KOH-soluble components. Degradation of 0.5 M KOH subfractions with pure polysaccharide degrading enzymes has confirmed the occurrence of pectic-xylan-phenolic complexes in which ferulic acid and its dehydrodimers are attached to the xylan component but not to the pectic component. Studies on cell separation show that the maturation- and storage-related increase in thermal stability of cell adhesion (and therefore texture) is probably due to an increase in phenolic cross linking of xylans mainly in the parenchyma tissues. This overcomes the thermal lability of the pectic polysaccharides that are responsible for cell adhesion in immature tissues. The storage-induced appearance of some of the diferulic acid moieties in a number of wall polymer fractions supports the hypothesis that the storage affect is a wound-induced response rather than a continuation of maturation-related activity.     

Evaluation of effects of transgenic Bt maize on microarthropods in a European multi-site experiment

The effects of maize expressing the Bacillus thuringiensis Cry1Ab protein (Bt maize) on soil microarthropods were assessed in the field at four European locations (two in Denmark and two in France) that differ in their climatic conditions or soil properties. Each site was considered as a separate experiment, with separate statistical comparison. Effects of farming practices using Bt maize were compared with conventional farming practices using near-isogenic non-Bt maize and also (at some of the sites) other conventional varieties. Furthermore, at one field site (Foulum, Denmark), the effects of Bt crops were studied in both conventional tillage and reduced tillage contexts. At another field site (Askov, Denmark), Bt maize effects were also compared to the effects of the chemical insecticide dimethoate. Moreover, at three of the field sites (all except Narbons, France), the possibility of a localised Bt effect around the rhizosphere compared to the bulk soil was assessed by sampling within and between maize rows. There were some significant negative effects of Bt maize on microarthropods in soils with a high clay content. Significant differences of the same magnitude also occurred between different conventional varieties of maize, but the effect of dimethoate appeared clearly greater than Bt effects. It is thus debatable if the Bt maize effect is an effect of the Bt toxin or just an effect of the maize variety. Based on the results, it can be concluded that the effect of Bt maize on soil microarthropods was small and within the normal variation expected in conventional agricultural systems.     

Behavioral responses of bottlenose dolphins, Tursiops truncatus, to gillnets and acoustic alarms

Along the east coast of the United States, by-catches of bottlenose dolphins, Tursiops truncatus, in gillnet fisheries exceed removal levels set under the US Marine Mammal Protection Act. One measure proposed to reduce this mortality is the use of acoustic alarms, or pingers, which have proven effective in reducing by-catches of other small cetaceans, but have not been tested with bottlenose dolphins. We examined the responses of bottlenose dolphins to a commercial gillnet equipped with functional (active) and non-functional (control) Dukane NetMark® 1000 alarms near Fort Macon, NC. Between 5 April and 10 May 2001 we used a theodolite to track 59 groups of dolphins around the net. Choice of treatment was random each day and the two shore-based observers were unaware of whether alarms were active (13 days) or controls (9 days). There were no significant differences in the number of groups observed (P=0.315; 1−β=0.835) or in the closest observed approach to the net (P=0.307; 1−β=0.828) between treatments. However, dolphins entered a circular buffer approximately 100 m around the net more frequently with control than active alarms (P=0.015). We conclude that some dolphins responded to the alarms by avoiding the net, but caution that the potential efficacy of alarms is confounded by dolphin behavior. Most dolphins were aware of the net, regardless of the status of alarms, and some dolphins fed on fish in the net or discarded by the fishing vessel. We believe that it would be unwise to use pingers in these fisheries because of the limited behavioral responses we observed in our experiment. Furthermore, the responses we observed are likely to diminish or change over time as dolphins habituate or sensitize to these alarms. Further research is required to understand the behavior responsible for entanglement.     

Thermal stability of texture in Chinese water chestnut may be dependent on 8,8'-diferulic acid (aryltetralyn form)

Ferulic acid (FA) cross-links have been implicated in the thermal stability of texture in Chinese water chestnut (CWC) tissues. The aim of the current study has been to investigate this concept further. CWC tissue strips were measured for their mechanical properties before and after extraction in increasing strengths of alkali. The mechanical properties were related to the associated mode of fracture (cell separation or breakage) at the fracture surfaces and the phenolic composition of the cell walls. CWC tissue softened after prolonged extraction in cold alkali due to an increase in the ease of cell separation. Analysis of wall-bound phenolics demonstrated that most FA moieties, including five of the six dehydrodimers, were released before tissue strength was reduced. Loss of strength was, however, coincident with the loss of 8,8'-diferulic acid, aryltetralin (AT) form. It has been suggested that this dehydrodimer may be particularly concentrated at the edge of the cell faces. These results provide further evidence for the involvement of this dehydrodimer in conferring thermal stability of cell-cell adhesion and hence texture in CWC. However, they do not exclude the other diferulates from involvement in cell adhesion.     

The dynamics of lucerne (Medicago sativa L.) yield components in response to defoliation frequency

The productive life of lucerne (Medicago sativa L.) stands depends on the rate of mortality of individual plants. However, self-thinning of plant populations may be compensated for by increases in other yield components, namely shoots/plant and individual shoot mass. Frequent defoliation reduces lucerne yield but it is unclear whether this is caused by an acceleration of plant mortality or changes in these other yield components. To investigate this, crops with contrasting shoot yields were created using constant 28 or 42-day regrowth cycles applied to a ‘Kaituna’ lucerne crop in Canterbury, New Zealand during the 2002/2003 and 2003/2004 growth seasons. Two further treatments switched from 28 to 42 or 42 to 28 days grazing frequency in mid-summer (4th February) of each year. The annual yield of shoot dry matter (DM) ranged from 12 to 23 t/ha for the treatments defoliated consistently each 28 or 42 days, respectively. Plant population was unaffected by treatments and declined exponentially from 130 plants/m² in June 2002 to 60 plants/m² in September 2004. The dynamics of plant and shoot population were associated with the light environment at the base of the canopy. The slope of the size/density compensation (SDC) of plants was −1.67 for the treatment defoliated each 42 days, near the expected self-thinning slope of −1.5 for stands at constant leaf area index (LAI). Self-thinning of shoots resumed after each defoliation when the LAI reached 2.1 and the transmission of photosynthetically active radiation (PAR_t) was 0.20. At this point the proportion of aerial DM in the tallest (dominant) shoots increased non-linearly from 30 to >80%, due to the mortality of intermediary and suppressed shoots. The average maximum shoot population in each rotation was 780 shoots/m² and unaffected by the decline in plant population due to a compensatory increase from 6 to 13 shoots/plant as the stand thinned. A lower asymptote of 43 plants/m² was estimated as the minimum plant population at which yield component compensation would maintain the productive potential of these ‘Kaituna’ stands. Differences in shoot yield were explained (R² = 0.97) by changes in the individual shoot mass (ISM) that were consistently lowered by frequent defoliation treatments. Frequent defoliations reduced crop productivity by limiting the assimilation of biomass into each individual shoot with negligible impact on shoot appearance rate, the number of shoots per plant at an LAI of 2.1 or the rate of plant population decay. Inter-specific competition for light was proposed as the main factor controlling self-thinning of plants and shoots regardless of their individual C:N status.