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Feature Article

Cable-Free Automatic Profiling Buoy

By Monica S. Kolding ' Bård Sagstad

APB5 buoy with STD204/208 probe and wireless data transfer by the Internet via GPRS (general packet radio service) or EDGE (enhanced data rates for global evolution).
The underwater universe of the oceans has always been a challenge to observe and monitor, particularly with remotely operated fixed floating installations for vertical profiles. Most environmental parameters such as light, temperature, oxygen and salinity vary significantly and often abruptly with depth, making high-resolution depth curves one of the most important diagnostic indicators for hydrological dynamic processes and environmental conditions of the water column.

With the globally increased focus on the marine biosphere as a source of food and the physical role of the oceans in regulating climate, the need for such data is rapidly rising. Aquatic resource managers and the growing aquaculture industry use environmental data to understand the interactions between biotic communities and their abiotic surroundings, as well as routine monitoring of ambient water quality.

Marine and climate researchers use the same data to better map and understand the oceanographic circulation systems, and to calibrate dynamic models for future predictions and scenarios.

Standard hydrological data are normally acquired by CTD sensors, with auxiliary measuring instruments for dissolved oxygen, turbidity and fluorescence, for example. The data collection, however, is normally ship-dependent and manually operated, and, hence, expensive and time-consuming. Remotely controlled automatic profiling with real-time results has, therefore, long been an attractive goal in marine technology. There are, however, numerous obstacles in achieving practical solutions, and foremost among these are communication, energy demand and maintenance.

Cable Connections, Biofouling Challenges
Up until present, communication and data transfer between the sensor and the recipient, as well as energy supply, has been heavily dependent on electrical cable connections. All existing advanced scientific CTD probes require manual reading or cable-dependent data transfer between the instrument and the recipient. For automatic profiling, this results in relatively long and heavy cables and vulnerable, fatigue-prone connectors, such as slip rings. This is because an oscillating body hanging from a winch drum cannot have a fixed socket connection without twisting the cable. In addition, the weight and corresponding energy demand for hoisting become substantial.

An important but often overlooked problem of sensitive and reliable data collection from submerged instruments is biofouling, i.e., the settlement and growth of sessile aquatic organisms on exposed surfaces. In many marine environments, such biological processes are fast, and require frequent cleaning and maintenance. To continue this article please click here.

Monica S. Kolding is a marine biologist and manager at SAIV AS in Bergen, Norway. She has a master's degree in marine biology from the University of Bergen, with a focus on pollution effects from aquaculture sea cages.

Bård Sagstad works as an electronic engineer and product developer at SAIV AS in Bergen, Norway. He has a bachelor's degree in electronics from Bergen University College and a master's in information technology from Griffith University in Australia.

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