Parameter constraints in a stream ecosystem model: Incorporation of a priori information in Monte Carlo error analysis

Using a model of mass and nutrient dynamics in a stream, we evaluated the use of a priori information (e.g., mass balance constraints, limits for the state variables, etc.) to increase the accuracy and efficiency of Monte Carlo error analysis. The results indicated that a priori information can effectively eliminate physically unrealistic simulations and reduce uncertainty about the predicted values. Some types of a priori information proved more helpful than increased accuracy in measuring model parameters.     

PRICE BEHAVIOR IN THE WATER MARKET OF NORTHEASTERN COLORADO1

ABSTRACT Past prices of Colorado-Big Thompson water shares were analyzed using an asset pricing model which incorporated the growth rate in real returns to irrigation water and the value of potential urban water uses. A real growth rate in the returns to irrigation water was estimated at 5.3 percent. Nevertheless, market values for water shares have exceeded capitalized agricultural values since 1969. Historically, urban use potential was heavily discounted, but the implicit discount rate fell rapidly in the last decade. The expectation that water shares will eventually be sold to municipal or industrial consumers now appears to be reflected fully in water prices.     

Polycyclic aromatic hydrocarbons in sediments and associated benthos in Lake Erie

Polycyclic aromatic hydrocarbons (PAH) were analyzed in surficial sediments and benthic organisms in southwestern Lake Erie near a large coal fired power plant. Sediment concentrations (530–770 ppb PAH) were relatively homogenous throughout most of the 150 km² area, although river and nearshore concentrations reached nearly 4 ppm. Oligochaete worms and chironomid midges were near equilibrium with local sediments except for enhanced concentrations in nearshore midges.     

Survey of four marine antifoulant constituents (copper,zinc, diuron and Irgarol 1051) in two UK estuaries

A field survey of antifoulant concentrations was undertaken in two UK estuaries (Hamble and Orwell) in 1998 and 1999. The two locations offered variations in physical aspects (Orwell estuary being significantly larger than the Hamble) as well as differences in boat densities (Hamble having almost twice as many vessels moored in the estuary and marinas). Samples were analysed for copper, zinc, diuron and Irgarol 1051, and were collected in summer and winter in order to identify potential seasonal variations in concentrations. The effect that different marina types (e.g. locked marina, one located in a natural inlet and pontooned ones in the open estuary) had on antifoulant concentrations were also investigated. Concentrations of the organic booster biocides, diuron and Irgarol 1051 in the marinas and estuaries were mainly influenced by leaching from antifoulant paints applied to the hulls of leisure craft, and so levels reflected the number of vessels present in the water. As a consequence significantly higher concentrations were found in marinas (up to ca. 900 ng l(-1) for diuron and 240 ng l(-1) for Irgarol 1051) compared with estuaries (up to ca. 400 ng l(-1) for diuron and 100 ng l(-1) for Irgarol 1051) and in summer compared with winter. Sediment concentrations of Irgarol 1051 and diuron were rarely detectable other than in the marinas where high concentrations were detected near slipways assumed to be derived from washed off paint chips. Dissolved concentration profiles for copper and zinc in the estuaries and marinas were different from those for the organic booster biocides partly because other sources of these metals contributed to estuarine and marina loads. In particular, riverine loads and inputs from sacrificial anodes attached to leisure craft, exhibited a major influence of estuarine levels of zinc. Consequently, only in the Hamble estuary for copper was there a clear distinction between summer (typically 3-4 microg l(-1)) and winter dissolved values (typically 1-2 microg l(-1)) that could be largely attributable to the leaching of antifoulant paints. Sediment concentrations for both metals were similar for both estuaries, with little variation between winter and summer values (Zn ranging from 28 to 614 mg kg(-1) and Cu from 6 to 1016 mg kg(-1)) as with the organic booster biocides highest levels were measured at the base of slipways in marinas.     

How well should laboratories perform in proficiency tests

The long-term performance of laboratories is examined using results from three proficiency testing programmes in the water and environmental monitoring sector. A medium term proficiency test pass rate of greater than approximately 75% is suggested as a minimum target for routine analysis to demonstrate fitness for purpose. This pass rate is proposed as a practical yardstick to be used by QA managers and accreditation bodies. This recommendation is contingent on a laboratory's continued and largely uninterrupted participation in a PT programme.     

中国、印度和世界的新秩序《世界报告2006》第一章(续)

转向世界粮食市场 与严重依赖外国石油的状况形成鲜明对照的是,中国和印度如今在粮食方面处于自给自足的状态,并为它们的成就而自豪（图1-2）.这两个国家都经历过严重饥荒的困难历史,都不希望这一悲剧情况重演.自从1985年以来,中国进口的粮食从来没有超过其消费总量的6%,而印度进口的粮食也没有超过其消费总量的3%（表1-3）.但是,在未来的几十年内,这两个大国是否可以避免求助于全球粮食市场（主要指小麦、水稻、玉米和其他主要基本食品）,已成为这两个国家和全球的一个尚待解决的、重要的问题.这是由于：世界粮食市场与石油市场的状况一样,与20世纪比较,指望生产过剩已经远非那么可靠了.     

Biochemical genetic variation at a leucine aminopeptidase (LAP) locus in blue (Mytilus galloprovincialis) and greenshell (Perna canaliculus) mussel populations along a salinity gradient

In several marine bivalve species, biochemical genetic variation at a leucine aminopeptidase (LAP) locus is associated with environmental variability, primarily salinity fluctuation. Population genetic variation at a LAP locus was investigated here in two sympatric mussel species (Mytilus galloprovincialis and Perna canaliculus) from three locations along a salinity gradient in Wellington Harbour, New Zealand. The data for M. galloprovincialis and P. canaliculus do not support the hypothesis that the LAP polymorphism in either species is associated with salinity variation among adult mussels. Due to the absence of small mussels among the samples it is not possible to discount the hypothesis that selection acts primarily against juveniles, as it does for M. edulis in Long Island Sound, USA. Wellington Harbour populations of M. galloprovincialis exhibited large and often highly significant heterozygote excesses at the LAP locus, whereas populations of P. canaliculus from the same locations exhibited large and highly significant heterozygote deficiencies. The reason for this inter-specific difference in population structure is unknown. If it is the result of selection, this suggests that selection acts differentially upon the two species, because demographic attributes and reproductive biology are very similar in the two species. For both M. galloprovincialis and P. canaliculus, significant levels of population genetic heterogeneity were recorded among three locations separated by only 8 to 12 km. Neither species exhibited shell length-dependent genetic variation at the LAP locus, suggesting that for these two species the LAP polymorphism is not associated with variation in shell length. Received: 30 December 1996 / Accepted: 6 January 1997     

Genotype-dependent fecundity and temporal variation of spawning in hybrid mussel (Mytilus) populations

Mussel samples were collected at 4 to 6 wk intervals throughout 1987 from two hybridMytilus edulis/M. galloprovincialis populations, at Croyde Bay and Whitsand Bay, in southwest England. These were analyzed at two polymorphic loci which are diagnostic for allozyme differences which typifyM. edulis andM. galloprovincialis. Dry mantle weight as a function of shell length was determined for all individuals of each sample. Size-frequency data for the two populations was obtained in September 1987 and March 1988. For all genotypes at both sites, fecundity was a function of shell length, and in both populations the frequency ofM. galloprovincialis alleles was positively correlated with shell length. At both sites, allozyme genotype explained a significant amount of variation in mantle weight either when assessed as a main effect or when assessed as an interaction with shell length or time of collection. At Croyde,M. galloprovincialis mussels had greater estimated fecundity per unit length than theM. edulis mussels. Differences in the timing of spawning activity between theM. edulis and theM. galloprovincialis mussels were inferred, and these differences might act to reduce the amount of interbreeding at Croyde. At Whitsand, a reduced level of variability in the timing of spawning activity and fecundity between the genotypes was observed and explained by a higher degree of genetic mixing. Because theM. galloprovincialis mussels had (1) a greater estimated fecundity at any length, and (2) a greater mean length than theM. edulis mussels, the mean genotypic annual fecundity perM. galloprovincialis mussel was 2.8 times greater than an individualM. edulis mussel at Croyde, and 2.2 times greater than an individualM. edulis mussel at Whitsand. This evidence thatM. galloprovincialis mussels have an advantage in fecundity, and thus perhaps in fertility, taken together with the evidence thatM. galloprovincialis also has a higher viability, indicates directional selection in favour of theM. galloprovincialis phenotype. Because of the observed temporal stability of the population it seems likely that this selection is counterbalanced by a massive imigration ofM. edulis spat from neighbouring populations.     

Genetic counselling and ethical issues with chromosome microarray analysis in prenatal testing

Molecular karyotyping using chromosome microarray analysis (CMA) detects more pathogenic chromosomal anomalies than classical karyotyping, making CMA likely to become a first tier test for prenatal diagnosis. Detecting copy number variants of uncertain clinical significance raises ethical considerations. We consider the risk of harm to a woman or her fetus following the detection of a copy number variant of uncertain significance, whether it is ethically justifiable to withhold any test result information from a woman, what constitutes an ‘informed choice’ when women are offered CMA in pregnancy and whether clinicians are morally responsible for ‘unnecessary’ termination of pregnancy. Although we are cognisant of the distress associated with uncertain prenatal results, we argue in favour of the autonomy of women and their right to information from genome-wide CMA in order to make informed choices about their pregnancies. We propose that information material to a woman's decision-making process, including uncertain information, should not be withheld, and that it would be paternalistic for clinicians to try to take responsibility for women's decisions to terminate pregnancies. Non-directive pre-test and post-test genetic counselling is central to the delivery of these ethical objectives. © 2012 John Wiley & Sons, Ltd.