One tool PICCOLO has in its toolbox is a so-called seal tag. The real name is Satellite-Relay-Data-Logger or SRDL. We also have them in different versions on board, some have 'only' a miniature CTD (for temperature, salinity and depth), others also record fluorescence, oxygen or light levels. As the name suggests, these loggers or tags are deployed on seals.
Seal tagging
7 March
Yixi Zheng
The tags we attached to the heads of seals will continue measuring the ocean’s temperature and saltiness after we leave their territory for the UK. Seals will find their way in the Antarctic winter and obtain full water column data that no human being has ever obtained. Three years ago, we published a paper using measurements obtained by seals and reveal, for the first time, the wintertime glacial meltwater pathways in front of Pine Island Glacier, one of the most rapidly melting glaciers in the world. Early this year, we also submitted a manuscript using seal-tag data that captured the summer-autumn upper ocean evolution. We wouldn't have been able to achieve this without seals and the seal tags.
6 March
Lars Boehme (University of St Andrews) and Gui Bortolotto (University of Aberystwyth)
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An oceanographic measurement from the SDA can tell us a lot about that one specific location, but what does the ocean in Antarctica look like in the winter, when it is practically impossible for ships to sail in the area, and are our measurements really representative? The tagged seals spread out and provide data from places that we have not visited. The tags stay on until the next yearly moult, so we hope to get data until the end of this year.
Lars Boehme and Gui Bortolotto are the seal scientists onboard. They had to secure multiple permits and go through ethics reviews before they could tag any animals. Tagging these seals serves two purposes: the data collected paints a picture of the oceanographic conditions in the western Weddell Sea, but also records the seal’s behaviour to understand how these charismatic animals live in this harsh environment.
Lars and Gui tagged two Southern Elephant Seals, six Crabeater Seals and 11 Weddell Seals during the PICCOLO cruise. The spread across species helps us to look at the different behaviours of these top predators in this region as they find their own niches in the ecosystem.
What kind of data do we get?
We get two types of data using the tags. We get data which describes the physical environment like temperature, salinity and oxygen, and we get information about how the animals behave, like where they go and how long and deep they dive.
The environmental data can be treated like coming from a ship as we get the information along the seal’s track from the surface of the ocean to the depths they dive to. We can then analyse it and use it in conjunction with all the other data sources we have.
The behavioural data has many different forms. The first information we get are the seal locations. While this seems to be very rudimentary data, it is very important as it can help us to distinguish hotspots for the different species and how they find their own niches or how their living space overlaps.
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The future
While the PICCOLO cruise is coming to an end, the data collection will go on. The seals will send us daily updates on where they go and what they are up to. Most importantly, they will provide us with more environmental information about this interesting region of the western Weddell Sea that PICCOLO is so interested in.