The target of the experiment is to study the impact of the acidification on the physical and chemical speciation of the nutrient elements as phosphorus, nitrogen and iron. Since ten days, the typical day at Stareso begins by the sampling inside the nine mesocosmes and outside mesocosms thanks to the cubi platforms. Oooohh the cubi … it’s very funny … and again more with the wind like yesterday and today!! Fortunately, a yoga class have been installed in Stareso (appointment time: 6:00 pm !!) and I’m going to try it !
After sampling, we go to the lab to filter the samples at two different fractions (0.2 µm and 0.015 µm).
After analysis of Dissolved Inorganic Nitrogen (DIN), Dissolved Inorganic Phosphorus (DIP) and Dissolved Iron (DFe) by spectrophotometry at the lab (LOV), in cleaned and controlled conditions, these filtrations will allow us to quantify the nutrient elements on two forms: dissolved (0.015 µm) and colloidal (0.2 µm).
With Cecile, we use also the samples filtered at 0.2 µm to determine the organic nitrogen and organic phosphorus. For that, the samples are irradiated by UV during 1h30. We are very impatient to discover the relation between inorganic and organic phosphorus after to have seen the data of alkaline phosphatase of Mauro in the most perturbated mesocosmes (P4-P5-P6).
Other experience: thanks to Alina’s help the microlayer (=thin layer between the ocean and the atmosphere) is taken, and so we have decided to analyze its composition at nutrients on forms inorganic and organic.
After a month in this beautiful place, it is time for me to go back to the North (cold, rainy, as it is always in Nice ;-)). As Andy mentioned, these are mixed feelings, happy to go back home to my partner and my boys, and of course a bit sad of leaving before the end of the experiment. No need to say, I had a great time here, with a fantastic group of people, in this unique area ! Many thanks to Pierre, Alexandre, Nilou, Richard, Joseph, Sylvain, Aurélia, Corinne and many others for their warm welcome. A special thank to the LOV team, the divers, the engineers, they did a fantastic job preparing the mesocosms and setting up an optimal system for our scientific work.
I would like to share with you some results on how the acidification of the mesocosms went. We were planning on having 3 controls and 6 lower pH levels. It took us 3-4 days to add enough CO2 saturated seawater to this quite alkaline water to reach the desired levels. At the start of the experiment, the levels were: 540, 640, 730, 850, 1090, 1290 microatm, very close to the expected levels, while in the controls, seawater was over the atmospheric equilibrium (400 ppm in the atmosphere) at a value of 450 microatm. Now we are at day 8 of our experiment, and everything is going well, it almost became a routine. The chlorophyll a concentration is rather low but we knew we would face very oligotrophic conditions, that makes our analysis work just a bit harder.
In the last few days, we were so happy to have optimal weather conditions to sample our mesocosms, no wind, temperature of the water increasing to 24 °C allowing a fall from the sampling platform without even noticing it 🙂 but of course everything has to come to an end, the wind is back and actually pretty strong. The 2 samplings from this morning were quite a bit of a challenge and we will have to postpone the addition of 13C (Laure’s experiment) to at least tomorrow.
I would like to emphasise one aspect of our stay here: after a long day sampling, filtering, measuring, repairing, swearing :-), some fun never harms. Two days ago, after a nice Gin-Tonic aperitif offered by our british colleagues, we decided on taking some pictures of us all on the sampling platforms. So we brought 2 platforms in the Stareso harbor in which we were supposed to stand nicely without moving too much… of course, this lasted for only 2 mins, as it quickly turned into a “Cubi” fight! We ended up all wet, it was great fun, people living in the area wondered what happened, as apparently we were “a bit” noisy….
For all these aspects, I will miss you guys and the Stareso station.
It is with mixed feelings that I leave Stareso. My partner is 8 months pregnant and our baby is due in mid-August and so I am very keen to be home with her, to help in the last few weeks preparation and just in case we have an early arrival. But I am also sad to be leaving a great bunch of people, in a fantastic research station on a very beautiful island. The MedSeA team here in Corsica have bonded well and most of the initial difficulties have been overcome so that the sampling effort is now a very smoothe operation and there is a great team spirit alive throughout the camp. My French speaking has not improved as well as I’d hoped (nor my Spanish, Italian, German) due to the multi-national group of people here – or that is my excuse, it could be my laziness that really prevented me from learning more!
I probably should not admit this, but when I arrived two weeks ago, I had great hopes of swimming daily and regular fishing trips and kayak expeditions, but all that ended on day 2 when a hungry moray eel came up to taste an English finger while I was washing bottles in seawater on the rocks close to the station.
Fortunately I was able to carry on with the most of my work here, although I have been unable to take part in the sampling on the cubi platforms, I have been able to help a little by driving the boat to the mesocosms and running an occasional water taxi for people going to Calvi – and can now add ferryman to my CV!
And so I travel back to rainy England with a scarred finger and an ever growing collection of samples in the freezer. I will be replaced by Denise who will work alongside Lisa, who has been here with me from the beginning and they will continue our investigations into the impact of ocean acidification on the Mediterranean nitrogen cycle.
We collect water from the mesocosms at 0400 , which is a fantastic time of the day despite what Martina and Walter say, and are making measurements of the rate of nitrogen fixation, nitrification and nitrate uptake. We also collect samples for the determination of the presence and activity of nifH, the gene responsible for nitrogen fixation, which will be analysed by our colleagues at the University of California Santa Cruz. In other areas of the world nitrogen fixation has been found to be stimulated at elevated levels of CO2, whereas nitrification has been inhibited and to our knowledge nitrate uptake has not been investigated directly. There is currently no information available for the impact of OA on these processes in the Mediterranean and so hopefully we can make a start in describing the impact of OA on the biogeochemistry of this area.
I would like to thank everybody here in Stareso for making this an exceptionally good two weeks, fieldwork is always the best part of this job, fieldwork in Corsica with the MedSeA crazy gang has been one of the best trips ever. I would like to thank the team from Villefranche who have performed a huge job in setting up of this experiment, each one of them has played a major part in the success of this project, but in particular my gratitude goes to my ambulance driver and medical translator – Samir.
I am back from the beautiful Corsica Island where I went during the preparation and starting of the MedSeA mesocosm experiments on acidification, off Stareso Laboratory near Calvi. This is an important event for the MedSeA project and for the theme dealing with the “Effects of ocean acidification and temperature on pelagic ecosystem function”. We are testing for the first time in the Mediterranean Sea, future acidification scenarios on microplanktonic organisms and key biogeochemical processes. This is very exciting and it was good to see that the testing went well and the actual experiment is started. There is a great group of people, all very motivated, excited and hard working. The people from LOV in Villefranche, led by Frederique Gazeau, are doing a great job in keeping everything under control and building a good and efficient sampling planning to make sure that the experiments will be successful.
I looked at same samples from the mesocosm by scanning electronic microscope and there are coccolithophores! (several species but all quite small and in different stages of their life cycle). These are very interesting samples for Angela’s PhD project.
All the best to the mesocosm team for a successful sampling and great results!
My last day today and feeling kind of sad that I am going, knowing that I leave work behind for my colleague Anastasia and good friends that I met during my stay. It was a pleasure. Somewhere between the hard work we had our moments…our moments of silliness. We managed even to laugh with our mistakes especially during the tests on how to sample, how to save the boxes when they fall in the water, how not to let go the rope because you start your journey to Genova…Oh we helped…we helped Villefrance team to realize almost anything that could go wrong on the cubi (platform). But as I said we laughed and I use the word kukurukoo for each silly action.
Trying to explain this to our colleagues here was some kind of difficult. Thank fully Raquel helped me a lot. She did the best kukurukoo action of the experiment so far. This is how the story goes:
We were all having dinner as usual, all together with our trays and plates in order. That day was the days that Patricia Ziverri (MedSeA coordinator) had arrived and by coincidence she was sitting near us and she was making polite conversation with all. Out of a sudden, Raquel with her poor English but with a beautiful heart says to Patricia: ‘Hello, I am Raquelle, and you??’ Patricia replies politely: ‘I am Patricia, how are you doing’. Raquel replies: ‘I am well, thank you. Are you working with us???’……at that point we all froze and stared at each other…It was then that Francesca said to Raquel: ‘She is the coordinator’…..And after that awkward moment passed, we started laughing so hard because Raquelle had explained in a really good way what kukurukoo is…….
Since yesterday the wind weakened in Stareso area but that mean the sun is harder to support! For the early morning sampling it isn’t a problem but for the 8.30am, 10.30am and instruments samplings it’s hard to stay 2hours in the cubis without sun protection. As it became to hard for Vincent and Raquel they’ve decided to bring a sun umbrella on the cubis and here is the new cub is style (click on the picture to see the video made by Louisa during a sampling):
Today we also had to remove all our empty boxes stored outside: an helicopter had to land at the station 15min later! It was spectacular to see the landing and takeoff in a so small area!!
After a long preparation, mainly done by the Villefranche team, and some days of test samplings were we all learned how to deal with the ropes, the platforms, the hydrobios integrater sampler, pumps etc, each of us have already sampled for its own data. During this preparation we had some troubles (mainly in the windy days). For example, the pump used to acidify felt once in the water (luckily it was saved), one of the carrying boxes with all the empty bottles also felt in the water in a windy day, but after a refreshing swim it was saved as well. Some of the scientist also felt in the water but came back swimming and finally, one team was caught in pictures when, unlocked themselves from the mesocososm units and, taken by the currents, started to drift in the platforms… soon they were brought back by zodiac.
All these experiences made us stronger and ready for the real samplings and subsequent processing of the samples. In my case it meant filtering about 80 liters of water. These because I want to see coccolithophores, marine calcifying phytoplanktonic organisms that are at the base of the food web and particularly sensitive to the changing ocean carbonate chemistry. Coccolithophores produce plates (coccoliths) of calcium carbonate which they use to cover their bodies (single cells).
For these organisms, a decreasing pH of the ocean is expected to affect the production of calcium carbonate by coccolithophores (see Image from Beaufort et al. 2011 article where evidence from sediment samples seem to agree this hypothesis). From each of the nine mesocosms I will be filtering 9 liters of water to later observe the filters under the scanner electron microscope (SEM). I will check whether those coccolithophores living in the more acidic ambient have more malformed, incomplete or thinner coccoliths than those living under normal conditions (in the Mediterranean “normal” means high alkalinity and saturation state for calcite, impeding the dissolution of calcium carbonate). Half of the water will be used to measure Ca in the smaller than 40um fraction (if I manage to get sufficient material). First samples are in the oven!
After 5 days of delay, we finally really start the sampling!! To place the events, last week-end the mesocosms tangled in the ropes and water went out of the bags. We had to re-open the bags wait one night close them again and start the acidification step by step during 3 days. The last acidification was on Saturday and to be on time we had to work late the days before (till 11pm sometime!).
So, yesterday (Time 0) we had the first departure at 4am to sample the processes. Well, in theory was 4am but…Louisa, Anggeliki and Mauro didn’t wake up!! Hopefully they don’t sleep in the lighthouse so, we could wake them up and we left only 15min late. But the teams on the sampling platforms were efficient and we arrived at the quay at 6.30am which was more or less the time expected for this team. Not even the time for a coffee and we prepared the vials for the incubations and other.
Fred and myself (Laure) we had to fill 8 vials of 60mL per mesocosm, inject “heavy water” (it’s water with 18 oxygen) in 5 of them and fixe the 3 others for the initial values. Then we incubate the 5 vials during the light period, phytoplankton will split this marked water to O2 by photosynthesis. Later in the laboratory we’ll be able to quantify the production of marked O2 and the decrease of marked water and so, have the Gross Primary Production data. The incubations are done near the mesocosms at 6 meter depth (half of a mesocosm).
The day wasn’t finish and we had a last important step to do: the addition of few grams of heavy stable Carbon (Carbon 13) which will allow us to follow the Carbon in the community.
Stop for the “science” and back to the event of the day: le radeau de la méduse. Yesterday, as a big day we had our first problem with the zodiac. While Vincent and Raquel were coming to the mesocosms to run the CTD (instrument to measure many parameters at the same time directly) the board on which the motor is kept broke!! they managed to join the Mini-Jeanne (the boat of the station) but we can’t use the zodiac anymore! We’ll to do a more extensive use of the kayaks to compensate this lost.
The oxygen is a fundamental element for the live in earth. The his amount in air, and in oceanic superficial layer, is 21% in constant balance in gas exchange air-sea.
The Winkler method is a test to determinate the concentration of dissolved oxygen in water samples: the quantity of dissolved oxygen is one of the measures of biological activities in seawater or freshwater. It’s necessary also, for example, to study water masses in the ocean or to measure the redox potential in water column. This test was originally developed by Lajos Winkler, an Hungarian analytical chemist, in 1888, modifying a preceding test. Winkler discovered a safer and more precise method of dissolved oxygen analysis thanks to an iodometric titration.
Carpenter in 1965 modified the Winkler method for analysis of dissolved oxygen, because he found some particularities about accuracy and errors, like air oxidation of iodide and volatilization of iodine, oxygen contributed by the reagent solution, iodate contamination of the iodide solutions, consumption or production of iodine by reagent contaminants, difference between titration end point and the equivalence point.
Principles of analysis
The production and respiration rates of microbial community will be calculate by variation in amount of dissolved oxygen in a defined time and comprehensive of all organisms activities in samples (autotrophs and heterotrophs).
The samples taken from mesocosms, will be fixed with a sequence of MnCl2 and NaI, resulting in a brown precipitate, and will be preserve a part in shadow and a part in light at same sea temperature on 24 h. The difference on amount of dissolved oxygen between T24 and T0 in shadow gives an estimate of planktonic respiration, a biological process of all organisms (in our case planktonic) where it obtains energy from oxidation of reduced organic compounds, realising CO2. Instead, the difference on amount of dissolved oxygen between T24 and T0 in light gives an estimate of planktonic production, a biological process of organisms that produce, by photosynthesis, organic molecules from carbon inorganic, by a reduction reaction, realising O2 (the photosynthetic organisms, primary producers, are at lower trophic level, supporting the total ocean and terrestrial life forming biomass).
After the incubation, it will be necessary proceed with a iodometric titration, because one mole of O2 reacts with four moles of thiosulfate and, by calculation of amount of thiosulphate, it’s possible calculate how many dissolved oxygen is in samples. Here I will try to explain shortly how.
Prior to start the analysis, it’s necessary standardize the titrator with a standard solution of KIO3 (potassium iodate), to minimize the error of the machine and to know the right concentration of the titrant solution. Moreover the sample is acidified with H2SO4 (sulfuric acid) to dissolve the hydroxides precipitated (MnCl2 + NaI) , liberating elementary iodine (I2) that reacts with surplus iodide ions, forming a complex (I3-) that is titrated with sodium thiosulphate. The total reaction is this following:
2S2O32- ↔ I2 ↔ ½ O2
Calculation and expression of results
With the iodometric titration, the titrator by the Tiamo software calculates the amount (equivalent volume) of thiosulphate that is necessary in titration at equivalent point of our samples. The calculation will be done by Excel, in which considering the real volume of bottles (approximately 50-60 ml) and putting the equivalent volume, by a formula it’s possible know the right oxygen amount (μmol/L). Furthermore, calculating the mean and standard deviation, crossing the fingers, we can do some considerations about our results.