| home | |
|
|
Marine Optics at Bangor
| Latest news: |
| 29.10.2002 Ulysses to assist in monitoring Irish Sea |
| 16.10.2002 New Centre for Satellite Observation Established in North Wales |
| THE MARINE OPTICS GROUP at Bangor formed in 1993, as a result of the award of a NERC special topic grant to develop recording bio-optical sensors. This followed a long tradition (going back to the early 1970's) of optical work at the University. Since forming, the group has grown rapidly and currently comprises 4 academic staff, 3 instrumentation specialists, 1 post-doctoral researcher and 5 Ph.D. students (appendix 1). The group has been successful in attracting research funding and in publishing results (appendix 2). |
Deploying Bangor University Colour Sensor off the RV Prince Madog |
The group's interests include in-situ measurements of apparent and inherent optical properties, including diffuse and beam attenuation, reflection (Bowers and Mitchelson-Jacob,1996), and natural and stimulated fluorescence. We also carry out laboratory measurements of absorption by natural dissolved and particulate material in sea water. The applications of our work are in the interdisciplinary fields of biological oceanography and remote sensing. The group has access to a wide range of in-situ optical instruments and image processing facilities. |
|
Fishing for data off St.Georges pier |
An early achievement
was the development and construction
of a number of 4-channel recording irradiance meters, and the deployment
of these on drifting buoys near the Canary Islands (Wild-Allen et.al.,1996)
and on moorings in the Irish Sea and loch Striven (Morrison et al., 1994).
These instruments provide a simple measurement of the "blue-green ratio"
(the ratio of upwelling blue and green irradiance at the sea surface), and
this shows a good correlation with chlorophyll concentration in water where
chlorophyll and water dominate the optical signal (Bowers and Tett,1995).
The instrument can therefore be used to monitor algal blooms in these waters,
and because it is a passive instrument, is less demanding on battery power
than recording fluorometers.
We also learned how to measure particle absorption on filters (Kratzer,1994) and how to use the results of this to explain, at least qualitatively, why the blue-green ratio does not work in turbid water containing inorganic particles (Bowers, Harker and Stephan,1996). Natural fluorescence is being used to measure chlorophyll profiles, and, together with laboratory measurements, is being interpreted in terms of fundamental properties of algal cells. |
|
| A number of challenges
lie ahead, and members of the group are starting to think about, and to
tackle these. On the remote sensing side, there is a renewed world-wide interest in ocean colour, and a number of ocean colour satellites are due for launch in the next few years. The major application of ocean colour imagery is in mapping pigment distribution associated with phytoplankton. Although this has been shown to work well in open ocean (optical case 1) water, there is a serious problem of interpretation in turbid coastal water (optical case 2), where non-algal particles and dissolved coloured material influence the colour of the water. The first problem is to unravel the optical signal so that algal concentrations in case 2 waters can be identified. A further problem is to use the information contained in the colour signal to try and distinguish different types of algae, particularly toxic ones. Group members are currently working on these problems, and we have established links with the NRA who routinely obtain remotely-sensed colour data using an aircraft-borne CASI instrument. |
Downloading data from the PRR-600 and INF-300 |
|
|
|
Solution to problems of in-water measurements occupy other members of the group. The interpretation of measurements in turbid water is again a problem here, although not such a difficult one, as a number of instruments can be deployed simultaneously in-situ to help unravel the different optical signatures. The 4-channel recording irradiance meters continue to be used, and form the basis for one Ph.D. topic (Suse Kratzer's). A major problem is establishing the inherent optical properties (absorption and scattering) of the non-algal particles, so that their contribution to the transparency and colour of the water can be assessed. Measurements on filters are not very good at separating absorption from scattering, and techniques developed for this purpose for phytoplankton cells need to be applied to these particles. |
|
|
|
|
|
