Impact of elevated levels of CO2 on animal mediated ecosystem function: the modification of sediment nutrient fluxes by burrowing urchins.

A mesocosm experiment was conducted to quantify the relationships between the presence and body size of two burrowing heart urchins (Brissopsis lyrifera and Echinocardium cordatum) and rates of sediment nutrient flux. Furthermore, the impact of seawater acidification on these relationships was determined during this 40-day exposure experiment. Using carbon dioxide (CO2) gas, seawater was acidified to pHNBS 7.6, 7.2 or 6.8. Control treatments were maintained in natural seawater (pH≈8.0). Under normocapnic conditions, burrowing urchins were seen to reduce the sediment uptake of nitrite or nitrate whilst enhancing the release of silicate and phosphate. In acidified (hypercapnic) treatments, the biological control of biogeochemical cycles by urchins was significantly affected, probably through the combined impacts of high CO2 on nitrifying bacteria, benthic algae and urchin behaviour. This study highlights the importance of considering biological interactions when predicting the consequences of seawater acidification on ecosystem function.

Monitoring of organotin compounds in seawater using semipermeable membrane devices (SPMDs)--tentative results.

The impact of anthropogenic pollutants on the marine ecosystem is related to the concentrations experienced by the biota in the seawater and the resulting concentration in the organism. Results from monitoring of pollutants in water samples provide snapshots that can be high or low depending on a wide range of variables. To provide more integrated information, semipermeable membrane devices, SPMDs, have been used to monitor different organic pollutants. In this survey, SPMDs were used to monitor organotin compounds in the marine environment. Time-integrated sampling using SPMDs and direct water sampling was carried out at six stations in the inner Oslofjord, Norway. The sample work-up procedure for both water and SPMDs was based on direct derivatisation using NaBEt4 and simultaneous extraction with an organic solvent. Analysis was performed using a gas chromatograph equipped with an atomic emission detector. The results show that SPMDs do accumulate organotin compounds from the water phase. Both tributyl- (TBT) and dibutyltin were detected in all of the analysed membranes while no monobutyltin was found. Levels found in SPMDs range from < 1 to 220 ng Sn SPMD(-1). Water concentrations range from 0.4 to 10 ng Sn L(-1). An investigation of relative levels of TBT showed a similar concentration gradient in the inner Oslofjord using either direct water sampling or passive sampling by SPMDs. As the membranes are able to accumulate the organotins from the water it will be possible to locate lower concentrations than with direct analyses of water samples.

Quantification of organotin compounds and determination of imposex in populations of dogwhelks (Nucella lapillus) from Norway.

Unintentional effects of the antifouling agent tributyltin (TBT) have been discovered in marine gastropods as the induction of male sex characters in females, known as imposex. The occurrence of imposex in dogwhelks (Nucella lapillus) was investigated in 41 populations sampled in 1993-1995 along the Norwegian coast. A method for quantification of organotin species using gas chromatography and atomic emission detection (GC-AED) was developed. Some degree of imposex occurred in almost all populations of dogwhelks studied, except in four from Northern Norway. The concentration of organotin compounds in the gastropods from the unaffected populations was below the detection limit (7 ng Sn/g d.w.). The concentration of TBT in dogwhelks from affected populations was in the range 48-1096 ng Sn/g d.w. A positive relation between the concentration of TBT in dogwhelks and the degree of imposex was found.

A simplified concept for controlling oxygen mixtures in the anaesthetic machine--better, cheaper and more user-friendly?

Modern anaesthetic machines are equipped with several safety components to prevent delivery of hypoxic mixtures. However, such a technical development has increased the complexity of the equipment. We report a reconstructed anaesthetic machine in which a paramagnetic oxygen analyzer has provided the means to simplify the apparatus. The new machine is devoid of several components conventionally included to prevent hypoxic mixtures: oxygen failure protection device, reservoir O2 alarm, N2O/air selector, and proportioning system for oxygen/nitrous oxide delivery. These devices have been replaced by a simple safety system using a paramagnetic oxygen analyzer at the common gas outlet, which in a feed-back system cuts off the supply of nitrous oxide whenever the oxygen concentration falls below 25%. The simplified construction of the anaesthetic machine has important consequences for safety, cost and user-friendliness. Reducing the complexity of the construction also simplifies the pre-use checkout procedure, and an efficient 5-point check list is presented for the new machine.

An evaluation of a time-saving anaesthetic machine checkout procedure.

Although it is generally acknowledged that a pre-use checkout of the anaesthetic machine significantly improves patient safety, an evaluation of such procedures is uncommon. Previous studies have shown that anaesthetic personnel using different check routines are unable to detect the majority of pre-set technical malfunctions. We have shown that it is possible to develop an effective and time-saving check procedure by integrating seven simple steps into one continuous flow procedure, where the settings and results of one step are used in the following step to optimize step interaction. The method is a 'core' procedure adapted to machines sold after 1980 according to the current ISO standard (presently undergoing revision). A user inquiry demonstrated that this pre-use check has been easily adopted in departments of anaesthesia. Moreover, the inquiry showed that most departments would not accept a checkout procedure which required more than 5-6 min. A study on nurse anaesthetists performing this procedure in the operating suite showed an average checking time of approximately 3 min. A performance test was undertaken by activating four different malfunctions in an anaesthetic machine training simulator. Twelve of 17 nurse anaesthetists rapidly identified all faults, whereas five nurses missed one or two faults. Our study suggests that our check procedure (the seven point check) provides a time-saving method for effective pre-use control of the anaesthetic machine.

A training simulator for detecting equipment failure in the anaesthetic machine.

Simulation is often used for training personnel in activities where the consequences of inappropriate actions are serious. We report a realistic training simulator, which can reproduce practically all potential malfunctions in the anaesthetic machine. Using actual standard equipment (Dameca 10750), the interior of the anaesthetic machine has been profoundly modified, whereas the external appearance remains virtually unchanged. The concealed alterations allow 20 different pre-set technical faults to be activated selectively from a mobile control unit. While assisted by an instructor, the trainee performs hands-on interactive experimentation with the simulator, while being exposed to 'unexpected' machine faults, which prompt for interpretation of error symptoms. Alternatively, the trainee can personally activate the simulated symptoms of different component failures, to enhance learning of the functional principles of the apparatus. The latter approach also allows a systematic presentation of defects to be identified by each step in a formal safety checklist for anaesthetic machines.