Ocean Sampling Day – Rothera’s delayed contribution!

This is a blog entry I wrote for the Ocean Sampling Day (please see http://www.microb3.eu/osd for more information). We sample twice a year for the OSD and the filtered samples are frozen and send back for analysis.

Myself and Amber taking water samples.
(Photo: Peter Webster)

Rothera is a British Antarctic Survey research station, located on Adelaide Island on the Antarctic Peninsula at 67° South (http://www.antarctica.ac.uk/living_and_working/research_stations/rothera). Like last year, we were planning to get out on the actual Ocean Sampling Day but where stopped by the weather and ice conditions. We had fast ice in Ryder Bay which prevented us from

Sampling by the ice edge with crabeater
seals paying a visit.

getting a boat in the water. However, as the ice was staying longer and longer, we were getting very excited about the possibility of doing a CTD and water sampling through the ice! When it was finally signed off, we were ready to go but the wind once more was in our way. Luckily, we were able to dive through the ice as it is closer to the shore and less dangerous. Then, we experienced why Antarctica is called the windiest continent on the planet. After a weekend of around 40-50 knots winds, half the sea ice in Ryder Bay had been blown out. Luckily, this meant we were able to get a boat into the water on the first calm day (just before the sea started freezing again).

North Cove is still covered in ice.

We got out to Site 2 (67°34.850 S, 68°09.340 W) on the 22^nd of July. Site 2 is one of three sites commonly used for the RaTS (Rothera Biological and Oceanographic Time Series) sampling (see Picture 3). We sampled just on the edge of the fast ice. The day started off very calm, but winds were picking up later on and finished just in time before we would have had to abort the sampling. The air temperature was only around -5°C. The water temperature was similar to last year -1.52°C. We deployed the CTD to 300m and winched it back up again by hand. Afterwards we collected water samples from 15m with our Niskin bottles.

Map of Ryder Bay showing the three CTD
sites (open circles): 1 is the main site (CTD1),
2 the secondary site (CTD2), and 3
is the fall-back site at Biscoe Wharf (WS3). 

Same as last year, we filtered 2l for each filter. However, on the ship last summer we finally got some Sterivex filters in which we used (4 replicates). They were frozen immediately with liquid nitrogen and are being stored in the -80°C freezer until the ship next March picks them up together with the samples from our Ocean Sampling Day in the summer.

The RaTS program includes various aspects of sampling. With our CTD we measure depth, salinity, temperature, PAR and fluorescence and the water samples we take back are mostly bottled up for analysis back in the UK by a number of different institutes. We analyse chlorophyll and ammonia in our lab here at Rothera. Whereas analysis for HPLC, nutrients, CO₂, salts, isotopes, DOC, viruses, Barium and metagenomics is conducted elsewhere.

Sabrina Heiser, Rothera Marine Assistant

Crew: Amber Annett (Marine Assistant for the Dutch collaboration), Peter Webster (Diving Officer)

(http://oceansamplingday.blogspot.co.uk/)