Direct Measurements of Air Distribution during in Situ Air Sparging

Direct observations on chemical micro-environment and microbial composition in biofilms are rare. The combination of microsensor and molecular techniques is highly useful for studies on the microbial ecology of biofilms. We shortly describe some applications of microsensors to study mass transfer phenomena and microbial processes in biofilms. It has recent been recognized that biofilms are not always flat layers of cells, but can consist of complex structures allowing liquid flow. Thus the classical view, that transport in biofilms is diffusional, is challenged. In laboratory grown biofilms the effect of convection on mass transfer was demonstrated. The microsensor technique has improved, so that direct in situ measurements in living biofilms are possible. By direct measurements of liquid flow with microsensors we show that in biofilms grown in bioreactors heterogeneity and convectional transport must also be taken into account. For the description of the microbial population we use molecular techniques, such as in situ hybridisation with 16S rRNA-targeted oligonucleotide probes. In a nitrifying-denitrifying biofilm we found a complex nitrifying community consisting of members of the genera Nitrosomonas, Nitrosospira, Nitrobacter and Nitrospira. Their occurrence was correlated with nitrification activity as determined by microsensor measurements.

Download Full-text

Remote Measurements of Horizontal Eddy Diffusivity

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech1794.1 ◽

2005 ◽

Vol 22 (9) ◽

pp. 1373-1380 ◽

Cited By ~ 9

Author(s):

Darek J. Bogucki ◽

Burton H. Jones ◽

Mary-Elena Carr

Keyword(s):

Numerical Models ◽

Measurement Techniques ◽

Rapid Assessment ◽

Digital Camera ◽

Eddy Diffusivity ◽

Direct Measurements ◽

Remote Measurements ◽

Rgb Images ◽

Speed Fluctuations

Abstract The rate of horizontal diffusivity or lateral dispersion is key to understanding the dispersion of tracers and contaminants in the ocean, and it is an elusive, yet crucial, parameter in numerical models of circulation. However, the difficulty of parameterizing horizontal mixing is exacerbated in the shallow coastal ocean, which points to the need for more direct measurements. Here, a novel and inexpensive approach to remotely measure the rate of horizontal diffusivity is proposed. Current shipboard measurement techniques require repeated surveys and are thus time consuming and labor intensive. Furthermore, intensive in situ sampling is generally impractical for routine coastal management or for rapid assessment in the case of emergencies. A remote approach is particularly useful in shallow coastal regions or those with complex bathymetry. A time series of images from a dye-release experiment was obtained with a standard three-megapixel digital camera from a helicopter that hovered over the study area. The red–green–blue (RGB) images were then 1) analyzed to distinguish the dye from the ambient color of the water and adjacent land features, 2) orthorectified, and 3) analyzed to obtain advection and diffusion rates of the thin subsurface dye layer. A horizontal current of the order of 6 cm s−1 was found. The estimated horizontal eddy diffusivity rate for scales of O(10 m) in the harbor was 0.1 m2 s−1. The dye diffusivity and advection rate that are calculated from the images are consistent with independent calculations based on in situ measurements of current speed fluctuations.

Download Full-text

The burden of proof in co-management and results-based management: the elephant on the deck!

ICES Journal of Marine Science ◽

10.1093/icesjms/fsr098 ◽

2011 ◽

Vol 68 (8) ◽

pp. 1656-1662 ◽

Cited By ~ 15

Author(s):

Mike Fitzpatrick ◽

Norman Graham ◽

Dominic J. Rihan ◽

Dave G. Reid

Keyword(s):

Burden Of Proof ◽

Ex Situ ◽

The Core ◽

Management Measures ◽

Direct Measurements ◽

Combined Use ◽

Ecosystem Level ◽

Core Questions ◽

Impact Models

Abstract Fitzpatrick, M., Graham, N., Rihan, D. J., and Reid, D. G. 2011. The burden of proof in co-management and results-based management: the elephant on the deck! – ICES Journal of Marine Science, 68: 1656–1662. Results-based management requires that outcomes can be demonstrated by industry and verified by managers on behalf of society. The core questions are: what outcomes, and how can they be proved? Existing fishery approaches to reversing the burden of proof are examined with focus on how proof is demonstrated. Outcomes can be measured in situ (on the vessel) or ex situ (at the stock or ecosystem level). In situ measures are preferable because they give direct measurements, although they can be invasive and costly. Ex situ results are only observable on scales that make it difficult to attribute them to specific management measures, or they may be influenced by external factors. Three main environmental impacts caused by fishing are assessed with respect to how industry can assume the burden of proof. The combined use of vessel-monitoring systems and benthic-impact models may offer a practical solution to the problem of managing fishery impacts on the benthos. Three Irish fisheries are assessed in terms of the feasibility of reversing the burden of proof. There are limits to the extent to which industry can assume the burden of proof, and the concept of sharing the burden of proof could be more realistic.

Download Full-text