Ocean Sampling Day – Rothera

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). The plan was to sample on the Summer Solstice (21st of December) however our first resupply ship since March (the RRS James Clark Ross) arrived on that very day, suspending boating activities whilst the whole base was involved in unloading a year’s worth of cargo (including Sterivex filters!). We were able to sample on the 27th of December.

The Rothera Oceanographic and Biological Time Series (RaTS) has been running since 1997 and continues year round – collecting data through weekly water sampling and CTD events. We sampled for the Winter Solstice OSD earlier in the year (albeit 6 weeks late due to sea ice conditions!).

For this sampling event we were able to get to the primary RaTS sampling site (67°34.400’S 68°13.500’W). The weather was calm but overcast, and on the way to the site we were fortunate enough to have a pod of ~12 orca join us! They were very interested in the boat and were clearly seen ‘spyhopping’ icebergs in their search for seals. The air temperature was 3°c (18°c warmer than our winter sampling event) and the water temperature at 15m (the RaTS sampling depth) was -0.46°c (over a degree warmer than the winter sampling event). 

We first deployed the CTD to 500m (winching by hand!) and then collected water from 15m. In contrast to the last OSD sampling event there is an abundance of life in the water here as it is the Antarctic summer, so I collected 4 x 1l samples. It was not feasible to filter on site so the samples were transported back to the laboratory to be filtered and frozen at -80°c. I filtered 2 x 1l with the newly arrived Sterivex filters and 2 x 1l with the GFF filters I used for the last OSD event.

The routine sampling for the RaTS program also means we have data for chlorophyll and ammonium concentration, as well as samples preserved for HPLC, CO2, salts, isotopes and nutrient analysis. This along with the CTD cast (temperature, salinity, PAR and fluorescence) creates an excellent data set.

Mairi Fenton

Rothera Marine Assistant