Managing the Tensions of Essentialism: Purity and Impurity

This article proposes a new interpretation of Pierre Bourdieu, as a theorist of purity and impurity. Bourdieu’s writings indicate that through the adjudication of things or people as relatively impure or pure an image is constructed of their essential truth. Building from Bourdieu, we will show how themes of purity and impurity can be used to manage the tensions associated with attempts to impute an essence to human nature or to reality, ensuring that the moral and epistemological significance of complexity is masked. This is the reason why themes of purity and impurity so often attend polarized world views, and why they are frequently mobilized for justifying and operating biopolitical processes of social stratification and regulation

Holographic mensuration of suspended particles in aquatic systems

The distribution and dynamics of aggregates in the aquatic environment play an important role in the modelling of biogeochemical processes. Previous work on aggregates in the ocean (e.g. sedimentary 'marine snow' particles), which vary in size from tens of microns to several millimetres, has used electronic counting or conventional photography coupled with image analysis. Here we describe a non-destructive in situ approach by use of holographic mensuration, hologrammetry, that affords greater scope and higher accuracy for the enumeration, sizing, and spatial distribution determination of aggregate particles. By means of two complimentary techniques, in-line and offaxis transmission holography, we present the initial experiments conducted in our laboratory and discuss the preliminaiy results from real image analysis

In situ off-axis holography of marine plankton

We present an off-axis transmission holographic technique for recording marine plankton in situ within a test tank of 36,000 ml with a pulsed laser in a 40 ns interval. The holographic plate is located in air and is therefore unaffected by aquatic conditions that may cause emulsion degradation (e.g. non-uniform swelling and surface contamination). The reference beam traverses a path in air only, and thus remains unaffected by dense concentrations of plankton. Third order aberrations, notably spherical aberration and astigmatism, are suppressed to yield an experimental resolution of 7 lp/mm (70 micrometres) with a USAF 1951 target located 600 mm in water from the observation window. Plankton particle counts examined by real image reconstruction show a strong correlation with duplicate samples examined under a microscope

Off-axis transmission holographic system for recording aquatic particles

We describe a holographic system for recording particles suspended in water. The hologram plate is located in air, separated from the test tank by an air/glass/water boundary. The holographic emulsion is therefore unaffected by adverse aquatic conditions within the tank (i.e. surface contamination, non-uniform swelling). The design geometry is intended to minimise the aberrations that arise from recording subjects located in water and replaying their hologram image in air. Third order aberrations, most crucially spherical aberration and astigmatism, are suppressed to give an experimental resolution of 7 lp/mm using USAF 1951 target in water 600mm from the boundary. Particles (plankton species) in the sub-millimeter to several millimeters size range are observed at planar sections within the recording volume by visual inspection of the hologram replayed in real image mode

RRS James Cook Cruise 87, 31 May - 18 Jun 2013. The Twilight Cruise to the Porcupine Abyssal Plain Sustained Observatory

The Twilight Zone is that depth zone in the ocean between 100 and 1000m depth where a tremendous amount of activity takes place. Much of the material containing carbon which sinks out of the upper sunlit or "Euphotic" zone is broken down in the twilight zone and then mixes back up to the surface in the winter. If it manages to sink further, this carbon is lost for periods of centuries. The main factor that affects this sedimentation process and the rate of destruction of the sinking particles is the structure and function of the biological community living near the sea surface and in the twilight zone beneath. This is because the planktonic plants and animals living there both generate and destroy particles. The Porcupine Abyssal Plain sustained observatory (PAP) is a heavily instrumented area of the open ocean 350 miles southwest of Ireland and in a water depth of 4800m. The instruments measure a wide variety of properties of the environment above the water, within it and on the seabed and much of the data is transmitted in real time to land via satellite

RV Meteor Cruise 108, 06 - 24 Jul 2014. Cruise to the Porcupine Abyssal Plain sustained observatory

The Porcupine Abyssal Plain Observatory is a sustained, multidisciplinary observatory in the North Atlantic coordinated by the National Oceanography Centre, Southampton. For over 20 years the observatory has provided key time-series datasets for analysing the effect of climate change on the open ocean and deep-sea ecosystems. As is normally the case during cruises which are needed to refurbish the observatory, a wide range of other activities were carried out during the cruise. The main mooring of the observatory broke in December 2013 during the horrendous winter storms which destroyed a number of Met Office moorings around the UK. However we were fortunate that the break occurred just below the main sensor frame and as a result we were able to recover it along with the massive Ocean Data Acquisition System (ODAS) buoy after it had drifted towards Ireland. We were therefore able to recover all of the sensors and, most importantly, the data stored in them. Prior to Meteor cruise 108 they were all refurbished and were deployed during M108 along with some additional sensors. In addition we recovered a set of sediment traps which had been collecting sinking material in the lower part of the water column for the previous 12 months and a new set was deployed. Furthermore some entirely novel research was carried out on the distribution and characteristics of marine snow particles in the top few hundred meters of the water column. These are inanimate particles which are the principle vehicles by which material sinks out of the upper sunlit zone down to the abyss, taking carbon down with them and out of contact with the atmosphere for centuries. We used optical methods to characterise their distribution and collected samples using the Marine Snow catcher thereby providing material for a variety of experiments with colleagues from Bremen. The Bathysnap time-lapse camera system which had been taking photos of the seabed at 4800m was recovered to give an assessment of the behaviour of the benthic animals and how the seabed appearance changes in response to deposition of material. A new module was deployed. Temporal variability of the water column and seabed fauna - a task which is difficult or impossible to do autonomously was assessed using nets and cores

RRS Discovery Cruise DY032, 20 Jun - 07 Jul 2014. Cruise to the Porcupine Abyssal Plain sustained observatory

The Porcupine Abyssal Plain Observatory is a sustained, multidisciplinary observatory in the North Atlantic coordinated by the National Oceanography Centre, Southampton. For over 20 years the observatory has provided key time-series datasets for analysing the effect of climate change on the open ocean and deep-sea ecosystems. As is normally the case during cruises which are needed to refurbish the observatory, a wide range of other activities were carried out during the cruise. The main mooring Ocean Data Acquisition System (ODAS) buoy had ceased transmitting data in March 2015, so a high priority was to recover the buoy and its stored data and this was successfully achieved. In addition, we recovered a set of sediment traps which had been collecting sinking material in the lower part of the water column for the previous 12 months and deployed a new set. These are the autonomous systems, but as is usually the case with our trips to PAP, we carried out various other activities and in this case we investigated the degradation of particles as they sink. Our colleagues from MIO in France carry out sophisticated interrogation using radiolabelling. The Bathysnap time-lapse camera system which had been taking photos of the seabed at 4800m was recovered to give an assessment of the behaviour of the benthic animals and how the seabed appearance changes in response to deposition of material. A new module was deployed. Temporal variability of the water column and seabed fauna - a task which is difficult or impossible to do autonomously was assessed using nets and cores

High concentrations of plastic hidden beneath the surface of the Atlantic Ocean

Concern over plastic pollution of the marine environment is severe. The mass-imbalance between the plastic litter supplied to and observed in the ocean currently suggests a missing sink. However, here we show that the ocean interior conceals high loads of small-sized plastic debris which can balance and even exceed the estimated plastic inputs into the ocean since 1950. The combined mass of just the three most-littered plastics (polyethylene, polypropylene, and polystyrene) of 32–651 µm size-class suspended in the top 200 m of the Atlantic Ocean is 11.6–21.1 Million Tonnes. Considering that plastics of other sizes and polymer types will be found in the deeper ocean and in the sediments, our results indicate that both inputs and stocks of ocean plastics are much higher than determined previously. It is thus critical to assess these terms across all size categories and polymer groups to determine the fate and danger of plastic contamination