Investigation into the effect of high concentrations of volatile fatty acids in anaerobic digestion on methanogenic communities

A study was conducted to determine whether differences in the levels of volatile fatty acids (VFAs) in anaerobic digester plants could result in variations in the indigenous methanogenic communities. Two digesters (one operated under mesophilic conditions, the other under thermophilic conditions) were monitored, and sampled at points where VFA levels were high, as well as when VFA levels were low. Physical and chemical parameters were measured, and the methanogenic diversity was screened using the phylogenetic microarray ANAEROCHIP. In addition, real-time PCR was used to quantify the presence of the different methanogenic genera in the sludge samples. Array results indicated that the archaeal communities in the different reactors were stable, and that changes in the VFA levels of the anaerobic digesters did not greatly alter the dominating methanogenic organisms. In contrast, the two digesters were found to harbour different dominating methanogenic communities, which appeared to remain stable over time. Real-time PCR results were inline with those of microarray analysis indicating only minimal changes in methanogen numbers during periods of high VFAs, however, revealed a greater diversity in methanogens than found with the array.     

Effects of pH and microbial composition on odour in food waste composting

A major problem for composting plants is odour emission. Slow decomposition during prolonged low-pH conditions is a frequent process problem in food waste composting. The aim was to investigate correlations between low pH, odour and microbial composition during food waste composting. Samples from laboratory composting experiments and two large scale composting plants were analysed for odour by olfactometry, as well as physico-chemical and microbial composition. There was large variation in odour, and samples clustered in two groups, one with low odour and high pH (above 6.5), the other with high odour and low pH (below 6.0). The low-odour samples were significantly drier, had lower nitrate and TVOC concentrations and no detectable organic acids. Samples of both groups were dominated by Bacillales or Actinobacteria, organisms which are often indicative of well-functioning composting processes, but the high-odour group DNA sequences were similar to those of anaerobic or facultatively anaerobic species, not to typical thermophilic composting species. High-odour samples also contained Lactobacteria and Clostridia, known to produce odorous substances. A proposed odour reduction strategy is to rapidly overcome the low pH phase, through high initial aeration rates and the use of additives such as recycled compost.     

Crowding and Experience-Use History: A Study of the Moderating Effect of Place Attachment Among Water-Based Recreationists

Effective recreation resource management relies on understanding visitor perceptions and behaviors. Given current and increasing pressures on water resources, understanding crowding evaluations seems important. Beyond crowding, however, variables that possibly relate to or influence crowding are of interest and in particular, place attachment and experience-use history (EUH). As EUH is related to place attachment and likely affects crowding, this study explored the moderating effect of place attachment dimensions on the relationships between EUH and visitor crowding evaluations. Water based recreationists at a U.S. Army Corps of Engineers site were contacted onsite and asked questions related to experience-use history, crowding evaluations, place attachment, and activity participation. Anglers and campers at the site identified similar crowding perceptions and place attachments. Only one of eight models tested revealed a moderating effect. Specifically, place identity moderated the relationship between the total times visited in the past twelve months and expected crowding among anglers. As such, the quest continues to understand the relationship among these important variables.     

Improving the environmental performance of the fishing fleet by use of Quality Function Deployment (QFD)

This article introduces Quality Function Deployment (QFD) as a method for improving the environmental performance of the Norwegian fishing fleet. Systems engineering has been introduced as a feasible process for handling sustainability issues in the fisheries, because it contains methods for general system design, operation, and support in a life-cycle perspective. QFD is related to systems engineering as a method for translating stakeholder needs into detailed system requirements at each life-cycle stage. Eco-QFD extends the scope of QFD, and combines QFD, Life-Cycle Cost (LCC), and Life-Cycle Analysis (LCA) to evaluate environmental effects and costs in the system development process. The article assesses the usefulness of Eco-QFD in fisheries management decision-making regarding sustainability in the fishing fleet, and for shipyards in their design of fishing vessels. It is concluded that Eco-QFD may be difficult to use for fisheries management in its present form, due to the complexity of sustainability, and the time and efforts demanded to carry out the analyses. Nevertheless, the structuring of the stakeholder needs and requirements may contribute to improved understanding of the decision-situation.     

Daytime light intensity affects seasonal timing via changes in the nocturnal melatonin levels

Daytime light intensity can affect the photoperiodic regulation of the reproductive cycle in birds. The actual way by which light intensity information is transduced is, however, unknown. We postulate that transduction of the light intensity information is mediated by changes in the pattern of melatonin secretion. This study, therefore, investigated the effects of high and low daytime light intensities on the daily melatonin rhythm of Afro-tropical stonechats (Saxicola torquata axillaris) in which seasonal changes in daytime light intensity act as a zeitgeber of the circannual rhythms controlling annual reproduction and molt. Stonechats were subjected to light conditions simulated as closely as possible to native conditions near the equator. Photoperiod was held constant at 12.25 h of light and 11.75 h of darkness per day. At intervals of 2.5 to 3.5 weeks, daytime light intensity was changed from bright (12,000 lux at one and 2,000 lux at the other perch) to dim (1,600 lux at one and 250 lux at the other perch) and back to the original bright light. Daily plasma melatonin profiles showed that they were linked with changes in daytime light intensity: Nighttime peak and total nocturnal levels were altered when transitions between light conditions were made, and these changes were significant when light intensity was changed from dim to bright. We suggest that daytime light intensity could affect seasonal timing via changes in melatonin profiles. Professor Dr. E. Gwinner died on 07 September 2004.