Category Archives: Science

Messing up the mesocosms…all for zooplankton! (by Thanos)

Thanos processing samples after collecting the zooplakton

If you ever find yourself in the middle of a mesocosm experiment somewhere in the Mediterranean Sea and you decide to mess up with it, then you have only one choice. Call us. Call the ZMUT*.

We can do almost anything. We can do cubiing, pumping and sampling all free of charge ;). We collect copepods and their eggs and feed them with the soup from the mesocosms (each soup with different pH flavour), trying to understand how acidification of the seas affects those living creatures.

But the most important…

We are the only ones who can professionally mess up the mesocosms. The only thing that is needed is a net, just a common zooplankton sampling net.

And after that …

No microlayers, no samples, no filtration, no sediment traps.

Simple as that.

PS1: Our best wishes (double for those who are here from the beginning) for a safe return back home and for good results to all cubists of STARESO.

PS2: Thanks all of you for your help!

* Zooplankton Messing Up Team (ISO 2000)

Sediment traps, the best part !!! (by Amélie)

Mesocosms are like iceberg, the big part is underwater, the bottom is around 14m of depth and at the bottom of the bag there are the famous sediment traps.

Underwater view of the meso

I am in charged of sediment traps, they need to be changed everyday! It’s the best part of the mission, every afternoon I go with Sylvain to replace the sediment traps (which consiste in a plastic bottle screwed on the sediment particules manifold). We are totally independent, we go under water from the station to the mesocosms using underwater scooter, it’s so cool!!! It’s very fast around 20 minutes to go, change the nine traps and come back.

Sylvain and Amélie leaving the harbor to change the sediment traps

Under water it’s so calm (even when very windy at the surface), everyday we are welcomed by a multitude of curious fish.

We found a lot of swimmers in sediment traps and sometimes jellyfish!

The plastic bottles which are changed every day.
A jellyfish in the sediment trap!!

The sediment traps collection is done to measure the export of organic and inorganic carbon and see if there are differences between treatments.

I would like to sincerely thank Sylvain who come with me everyday and Alex (the Sunday afternoons) as well as Stephen who took a really nice pictures of mesocosms.

Nutrients sampling

The Mediterranean Sea in general, and the Calvi Bay in particular, are very oligotrophic areas. As a result, organisms living in their waters are adapted to low nutrient concentrations, and even small changes in these concentrations can cause big perturbations of natural communities.

Thanks to the mesocosm experiment, we (Sylvie Gobert from University of Liège, and Loïc Michel, from the Stareso research station) will try to understand if ocean acidification could modify nutrient concentrations in Calvi Bay. To do so, we take daily samples to monitor nitrates and nitrites, ammonium, phosphates and silicates concentrations in each of the mesocosms, as well as an “extra” sample out of the mesocosms. We look forward to seeing which trends emerge from the data, and we hope that they can be useful for other scientists taking part of the experiment too…

Once the water is sampled, we have to condition the samples. This is the most critical part of our jobs, because by this time, it is usually around 11 AM. Since labs are quite crowded, we work directly on the Stareso dock, under the burning Corsican sun. During this dangerous task, the only things that prevent us from baking are 1) our beloved straw hats (see fig. 1) and 2) a very good hydration plan based on refreshing Corsican beer. After conditioning, we place the samples in the freezer (for NO2- + NO3-, NH4+ and PO43-) or in the fridge (for SiO44-).

Nutrient conditioners hard at work under the Corsican sun.

Now the experiment is nearly finished, and nearly all samples are stored, patiently awaiting analysis. On Sunday (July 15th), our colleague Renzo Biondo (also from Lab of Oceanology, University of Liège) will join us, and we will start the analysis step. All nutrient concentrations will be determined at Stareso, using our Skalar automated continuous flow automated analyser. Methods differ for each compound, but all are based on colorimetric detection. When everything runs smoothly, this type of analysis is rather quick, and we hope to be done in about a week… However, the analyser is a whimsical machine, and a lot of things can go wrong. To ensure that the Nutrient God is with us, we consider sacrificing one of the station’s cats to him. Let’s hope it will be enough to please him!

CTD (by Anastasia)

CTD (standing for: Concise and Terribly Distressful)
Date of birth: end of 2011
Place of birth: Washington, USA
Parents: Raquel, Angela, Grigor and Vincent
Siblings: The Radiometer


-Handle the CTD with immense care and don’t rush it!
-A good teacher (while on the cubi) will definitely help you take accurate measurements and will explain in depth the principals of its use, unless singing/listening Greek songs distracts him!
-Singing in general will help you a lot to concentrate and find the perfect – appropriate rhythm for lowering the CTD in the water
-Use an umbrella while using it and hide below it, in order to protect from light (and be fashionable!)
-Drift with the currents and trust the waves when “travelling” from one cluster to another, without being attached to any of the ropes. Oops! If the weather changes unexpectedly and floats you towards Calvi, jump in the water and save the CTD!
-Don’t panic! Instructions for correct handling are given on board the cubi. Try to keep calm
-Real time data will only come after a quite long processing day that requires patience and … knowledge of course
-Rinse the CTD with water (and affection…) immediately after each use and, if necessary, forget about your lunch

Vincent and his second baby

Principal(ok, let’s be a bit more serious now!)

The CTD (actually standing for Conductivity, Temperature, Depth) is an instrument that takes continuous measurements of several water characteristics (temperature, conductivity – from which salinity is derived -, pH, fluorescence of chlorophyll pigments, photosynthetically available radiation, and dissolved oxygen concentration), with the use of sensors that are placed whether in external or internal flows. It provides you with a detailed description of your water sample, with measurements taken four times per second. These measurements are then aligned to depth (by converting pressure to meters) and are saved in digital form in order to be processed later…

Do you think it is too hot? (By Eija)

We “atmospheric people” are working on that! Let me explain.

Ocean is a source of gases and tiny particles which help to make clouds and cool the atmosphere. Isn’t this great news during these super hot days at Stareso?

Bubble bursting aquarium

To be more exact: The goal of the atmospheric experiments here is to understand which type of particles and in which quantities are released into the atmosphere from Mediterranian Sea. We take samples from three mesocosms of different levels of acidification. Then we “bubble” the samples in an aquarium simulating the particle release process by winds and waves over the sea. For this, a bit noisy pump is needed.. When we have the particles in the air inside the aquarium, we study their ability to form clouds (to make the climate less hot). This depends, at most, on the particle chemical composition and size. In addition to this, several types of samples are taken of the aquarium air, in order to analyse the gas and particle phase compositions afterwards in the lab. Quantities and properties of organics are on top of our interest list. Thanks to Alina, we can also sometimes “enrich” our samples with the surface layer – this is important since surface is in direct contact with the atmosphere.

It is amazing how little we still know on the fluxes of particles (and gases which can condense on the particles) from the oceans. And even less on the possible effects of ocean acidification on these fluxes. So this can be really mind blowing science we’re doing (mind blowing not only because of the noise…)! Bear with us for couple of more days…

Ocean Acidification impact on trace elements (by Justine)

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).

Filtration device used in Stareso

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).

UV irradiation system

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.

back from the beautiful Corsica Island (by Patrizia Ziveri)

Working in the mesocosms and the mesocosms under water
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.

Coccolithophores from Stareso!

All the best to the mesocosm team for a successful sampling and great results!

… and the experiment started!

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.

Sample team is brought back by boat after drifting with the currents. On the platform they were probably just enjoying the little trip 😉

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!

Modified from Beaufort et al. 2011

Les radeaux de Stareso…

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!).

The zodiac with the broken board and motor nearly on the seawater!!

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.

The boats we use to go to the working area (=the mesocosms): the kayak; the zodiac and the Mini-Jeanne (and the biggest one is the Marie-Jeanne but we don’t use it).

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.

Winkler Method (by Walter)

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

Phases of the method

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.

Winkler Team