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April 2008 - Seals as ocean observers

A/Prof Simon Goldsworthy and Dr Brad Page

SARDI scientists have recently recovered a state-of-the-art conductivity-temperature and depth logger that had been deployed on an Australian sea lion male on Kangaroo Island over a 42 day period.  In collaboration with Prof. Michael Fedak of the Sea Mammal Research Unit, University of St Andrews, Scotland, and following on from the successful deployment and recovery of a similar device in 2007, we have been further testing the application of satellite relay CTD data-loggers. Over the 42 days of deployment in March and April, the seal made 4 foraging trips providing 8 cross-shelf CTD profiles.  Since then, hundreds of cross-shelf temperature and salinity profiles have been collected and sent via satellite to the University of St Andrews, more will be recovered when the archived data are downloaded. The results have again proved very exciting; identifying 5+°C thermoclines associated with Bonney Upwelling (see figure below – a 3D cross-shelf temperature profile by the seal). The cross-shelf profiles document the breakdown of upwelling waters over the last 40 days to an essentially fully mixed water column, typical of winter continental shelf waters under the influence of a predominantly westerly air-stream.

Using seals as ocean observers provides new and exciting possibilities for collecting oceanographic data. As seals are autonomous, they can collect oceanographic data from areas away from fixed moorings, floats or vessels. Data can be accessed in real-time, and deployment and retrieval costs are negligible relative to vessel and mooring approaches.

Animal borne sensors presently provide the only research platforms that interact with both physical and biological oceanographic features. As such they provide a unique means to specifically target and collect oceanographic data from regions that are ecologically important in terms of production and biodiversity. Animal borne sensors can also act as oceanographic explorers and prospectors that will assist in the strategic placement of existing observing platforms such as fixed moorings or directed ship-based research.

SARDI and MISA supported scientists (A/Prof Goldsworthy - SARDI, A/Prof Middleton - SARDI, A/Prof Seuront - SARDI/Flinders University, A/Prof Bradshaw - SARDI/Adelaide University), have recently submitted an International Science Linkages Grant (DEST) ‘Biological sentinels to map change in the Australian ocean environment.’ This project aims to further develop the use of seals as ocean observers, ultimately integrating this program into the national Integrated Marine Observing System (IMOS).

Cross shelf

Example of cross-shelf temperature-depth profile data obtained using an instrumented Australian sea lion on Kangaroo Island in March-April.