Effect of salinity on natural community and production of Litopenaeus vannamei (Boone), within experimental zero-water exchange culture systems

Recent efforts have been made to culture marine shrimp in systems operating under low or zero‐water exchange and with decreased water salinity. The aim of this study was to investigate the impact of various salinity levels on qualitative and quantitative characteristics of the natural community and, more particularly, ciliated protozoa, and compare this information with shrimp growth and survival. Tanks with 9‰ salinity were characterized by a higher pH, but also by a significantly higher concentration of chlorophyll a (Chl a) per weight of suspended matter (1.93 ± 0.72 µg Chl a/mg TSS) than tanks with 18‰ (1.29 ± 0.68 µg Chl a/mg TSS) or 36‰ (1.37 ± 0.61 µg Chl a/mg TSS) salinity. Concentrations of ciliates (max 6000 cells mL^?1) showed considerable fluctuations over the sampling period, reflecting the impact of water salinity, dynamic interactions between ciliates and their diverse roles within the shrimp production system. There was no significant difference between survival rates of shrimp reared at 9‰, 18‰ or 36‰, but decreasing salinity from 36‰ to 9‰ led to a significant decrease in final shrimp body weight (from 13.40 ± 0.26 g to 10.23 ± 2.72 g). Future work should address the potential of ciliates as an indicator of aquaculture water quality, as is currently being done in the wastewater industry, and the contribution of ciliates as food sources.     

Growth rates of different populations of the edible mussel, Mytilus edulis, in north Norway

Populations of Mytilus edulis which were attached to the floats supporting the fish cages at the University of Tromsø's former experimental fish farm were found to have grown at a relatively high rate, and almost continuously. In contrast, mussels taken from other populations in the area which were not in the vicinity of any fish farm had grown more slowly and had marked growth-stoppage rings, probably laid down in winter. Mussels samples from a second fish farm in the area had grown at a rate similar to those from the University's fish farm. Possible reasons for the differences in growth rates among the populations sampled are discussed with reference to the possibilities of mussel farming in north Norway.     

Influence of fertilization and organic amendments on organic‐carbon fractions in Heilu soil on the loess plateau of China

The influence of fertilization on organic‐carbon fractions separated by density and particle size in Heilu soil (Calcic Kastanozems, FAO) was investigated in a 20‐year (1979–1999) long‐term experiment on the Loess Plateau of China. Compared to an unfertilized treatment, N application alone did not increase total organic carbon (TOC) and its fractions of density and particle size. However, the treatment of N + P fertilization significantly increased salty‐solution–soluble organic carbon (SSOC), microbial biomass C (MB‐C), and organic C associated with fine silt. When manure was applied alone and in combination with N and P fertilizer, the light fraction of organic C (LFOC), SSOC, and MB‐C were increased significantly, and the TOC was as high as that of a native Heilu soil. Organic C associated with different particle‐size fractions was also increased significantly, and the allocation of C among the fractions was altered: the proportions of C in sand (>50 μm), coarse‐silt (20–50 μm), and fine‐clay (<0.2 μm) fractions were increased whereas fine‐silt (2–20 μm) and coarse‐clay (0.2–2 μm) fractions were decreased. It is concluded that N fertilizer alone is not capable of restoring organic‐matter content in the Heilu soils of the Loess Plateau and that C‐containing material like manure and straw is necessary to produce significant increase in soil organic carbon in these soils.     

Effect of electrical stunning at slaughter on the quality of farmed turbot (Psetta maxima)

Food quality aspects of farmed turbot (Psetta maxima) were compared following two methods of slaughter: the current commercial method, by immersion in an ice slurry, which is then dewatered after approximately 20 min, or by first humanely, electrically stunning the fish using a prototype commercial stunner, before immersion in an ice slurry, which is dewatered after 20 min. Quality was assessed for up to 10 days of storage on ice following slaughter. No differences were found between the slaughter methods in terms of an overall carcass quality: overall appearance, haemorrhage, damage, burst gall bladder, staining of the body cavity by leakage from the gut or damage to the spine. No detectable difference was found between the treatments using the industry standard freshness scoring system, the Quality Index Method. Both groups of fish were classified as ‘Fresh’ after 10 days of storage on ice. Using objective measurements of colour, no differences between fish from either treatment were found in fillet colour. Changes in flesh pH were similar in electrically stunned and traditionally killed fish with a mean pH (±SE) at 2 h post‐mortem of 6.80±0.027 declining to 6.44±0.032 at 24 h post‐mortem. Humane electrical stunning of turbot at slaughter neither detectably improved nor decreased product quality as measured between 1 and 10 days of storage on ice.     

Managing outbreaks of invasive species: Eradication versus suppression

Abstract

A framework is developed to evaluate eradication as one of three alternative management responses to an outbreak of an invasive species: eradication, suppression or no action. This framework can be used to establish under what conditions an eradication option could provide an expected net economic benefit, and whether this net benefit exceeds that of the other two options. The eradication option is more likely to be preferred in situations where there is an immediate export benefit that is derived from eradication of the outbreak, and also the uncertainty associated with the likely success of eradication is low.     

Alterations in the bovine bronchoalveolar lavage proteome induced by dexamethasone

Stressors such as transportation, weaning and co-mingling increase susceptibility to bacterial pneumonia in cattle and are associated with elevated levels of endogenous glucocorticoids. To determine the effect of glucocorticoids on the proteins expressed in the fluid lining the respiratory tract, bronchoalveolar lavage (BAL) was performed on cattle treated with dexamethasone or saline and proteins were resolved by two-dimensional electrophoresis (2-DE). Significant changes in expression were observed for 9 of the 363 detected spots, and the identities of these proteins were determined by mass spectrometry. Consistent with the initiation of an acute phase response, the expression of alpha-1-acid glycoprotein (orosomucoid) and alpha-1-antitrypsin was increased and alpha-2-HS-glycoprotein (fetuin) was decreased in the BAL fluid of dexamethasone-treated cattle. In addition, dexamethasone induced the expression of two hydrophobic ligand-binding proteins, adipocyte-fatty acid binding protein and odorant binding protein (OBP), as well as the proteins alpha-enolase, cofilin-1 and immunoglobulin J chain. OBP mRNA expression in bronchial biopsies was quantified by real-time RT-PCR and the 6-fold higher levels of expression observed in dexamethasone- versus saline-treated animals correlated with the changes observed in OBP protein level. These findings demonstrate glucocorticoid-dependent changes in the protein composition of the epithelial lining fluid of the respiratory tract, identifying proteins potentially integral to respiratory disease susceptibility.     

Property Values in a Low Populated Area when Dual Noxious Facilities are Present

This paper examines how the presence of dual, disparate environmental disamenities located near each other impact property values in a semi‐rural area. A heavy metals manufacturing facility and a rubber‐compounding factory operate two and one half miles apart in a small community. The heavy metals manufacturing facility uses low‐level depleted uranium in its production. The level of production is small and the production process does not emit visible air pollution or odors that can be easily identified. Thus, if the surrounding community negatively perceives a potential risk, it is not through the channels of sight or smell. The rubber‐compounding factory emits foul odors and some visible air pollution. Thus, its negative externalities and potential risks are easily perceptible. Using the hedonic price technique, this paper examines the impact of the use of a non‐perceptible hazardous material in the production of a good on housing prices in a community when another more visible, noxious facility is present. The results show that noticeable disamenities are capitalized into housing values, while non‐visible ones are not.     

Wind-splash erosion of bare peat on UK upland moorlands

Peat is a common land surface material in many countries of the world and is particularly important in upland regions of the UK. Peat landscapes represent an important land use for hill farming, water management, and shooting, and are a globally scarce resource. Wind is a fundamental characteristic of upland environments in the UK and has long been recognised as a significant factor in peat erosion. This paper presents the first results of a project that aims to determine the significance of wind action in the erosion of upland peat. Wind erosion monitoring is being undertaken at Moor House in the North Pennines on a 3-ha area of relatively flat, sparsely vegetated peat. Measurements using arrays of passive horizontal mass flux gauges (fixed orientation vertical slot gauges), together with a vertical array of mass flux samplers (directional), provide estimates of sediment flux. A micrometeorological station records local wind speed (four heights), wind direction, rainfall, soil moisture, and temperature conditions. For 1999 and 2000, the annual horizontal net erosion flux is 0.46 and 0.48 t ha⁻¹, respectively. Results of detailed monitoring over a 10-month period demonstrate that the peat sediment flux collected in windward- and leeward-oriented sediment traps on 10 separate occasions is between 3 and 12 times greater in the windward-facing traps. The concentration of peat with height decays rapidly and the majority of the peat is transported close to the ground surface. Above 0.3 m, very little peat is found. Significant horizontal fluxes of peat occur in both wet and dry periods. This is evaluated using the local micrometeorological data to try and predict sediment yields. Correlations among time-averaged friction velocity measurements, surface conditions, and sediment flux are complex. Event-based measurements, as opposed to cumulative sediment yields, are required to resolve this. These results quantify for the first time the significance of wind action in the erosion of peat in a UK upland environment.     

离子交换树脂膜原位提取土壤有效性养分的探讨

连续3年在实验室内和利用盆栽及田间进行了利用离子交换树脂膜对土壤的原位测定,探讨影响树脂膜对土壤中养分离子吸收的因素;制定出一套包括树脂膜埋置方法,时间,洗脱土粒和解吸被树脂膜吸附的养分等的标准方法,称为植物根模拟法(Plant root simulator)。 通过400多个土壤样品测定结果表明,用树脂膜提取的土壤有效氮、磷、钾和硫与用常规化学法提出的量有显著相关。盆栽条件下,树脂膜原位埋置法对预测供试作物油菜吸取土壤有效养分的能力与常规化学法相当,而硫的效果更好。树脂膜在田间直接埋置能合理地表征土壤中硝态氮的分布,并具有同时提取土壤各种有效养分的能力。由于离子树脂交换膜不受地域影响,具有广泛的通用性,因而在土壤养分有效性的研究中应用前景广阔。