64PE374 - Dagboek 7 (in het Engels)

Imagine that you could pick an O2 molecule, and just like you would do with a product on a supermarket shelf, turn it around and find a small label with the manufacturer’s details on its back. In the case of a dissolved O2 molecule sampled at sea, there would be two options: either this molecule was locally produced by photosynthetic organisms, or it was “imported” into the seawater from the atmosphere.

The isotopic composition of dissolved O2, serves as such label. By carefully measuring the relative abundance of O2 isotopes (16O, 17O and 18O) in a water sample, one can determine the fraction of the O2 that was produced in the water, and the fraction that was imported from the atmosphere. These unique characteristics of the isotopic composition have been used for more than a decade to estimate the rates photosynthetic O2 production in the mixed-layer in many regions of the oceans.

But that is not what brought me on-board of the Pelagia.
In the past couple of years, measurements that were conducted in various parts of the ocean have shown surprising amounts of photosynthetic O2, at great depths. In addition to that, my own measurements from the Gulf of Aqaba showed that physical boundary processes “inject” photosynthetic O2 into the deep waters of the gulf. These O2 “injections” are often surprisingly quick and intense.

Will photosynthetic O2 be found in the deep parts of the Mediterranean? Will the Adriatic, like its much smaller middle-eastern cousin, the Gulf of Aqaba, show signatures of rapid injections of photosynthetic O2? These questions are what brought me from The Hebrew University in Jerusalem, to board the Pelagia, about a week and a half ago. I have been learning a lot about many things since then. Unfortunately, I cannot analyze my samples on board, and therefore, I do not have answers to my questions yet. I will have to be patient with that. However, I did learn a lot about the careful process of sampling for trace metals and got to know about new proxies in seawater. I also learned how to say “thank you” and “you are welcome” in Dutch, and I now know the difference between “The Netherlands” and “Holland” (though I am still puzzled about why The Netherlands/Holland is inhabited by “The Dutch”). I have been enjoying the warm air of the Mediterranean, a priceless hour of swimming at the foot of the volcanic island of Stromboli, but mostly, I appreciate the friendly company of people from the Netherlands, the UK, Italy, France and New-Zealand, and the warm welcome, helpfulness and hospitality of the Pelagia crew.

I can only wish that the week ahead will be as interesting and enjoying as the one behind.

Eyal Wurgaft
RV Pelagia
August 5th, 2013