After one week on the ship we will soon sample our 29th underway sampling and our 12th CTD station at 7°20’ S 66° E. This week has been very busy and we hardly slept, but we are excited about the results of our first experiments on board. We – the “biologists” – try to get a better understanding on the biological processes in the ocean and especially those relevant for trace gases cycling. Therefore we process a lot of seawater, fixing, freezing, or filtering it, for further analysis back home in the labs at GEOMAR. We will determine the abundances of key phytoplankton groups and bacteria as well as the concentrations of dissolved organic matter in the water column.
We built up a nice little “theatre” for our seawater samples… that is what we call incubation experiments. Why do we do that? We want to estimate primary production and heterotrophic respiration via oxygen measurements. The samples are kept in glass bottles and incubated in water baths for 24h under the same temperature, light intensity and day-night cycle as in the ocean and every now and then, we check their performance measuring oxygen and sometimes also bromoform, dibromomethane and isoprene concentrations. So far, it seems that the experiments are running very well and we will hopefully come back home with some interesting results on the microbial activity here in the Indian Ocean.
These measurements, in combination with the CTD stations and the underway samplings, mess up our daily plan and we have to do strict time management so that each of us can have 5+x hours of sleep per day. Fortunately we have the support of all other scientists, the crew, and unexpectedly we get a helping hand (or better two helping hands) from Danishta, a marine biologist from Mauritius who joined our cruise to learn about all our methods and get some experience on the daily life on a research ship. We are very happy that she joined our “biologists team” and she really saves us a lot of time by helping with sample processing or preparations. Thanks to her help, we could even spend some moments in the sun reading or watching the amazing sky full of stars at night.
We are looking forward to another week on board of RV Sonne in tropical waters and – yeah – approximately 10 more CTD casts, 37 more underway samplings and five more incubation experiments – but also with nice people, delicious food and tropical sun.
by Sonja Endres and Luisa Galgani