Do ciliates feel the stress?

To answer this and other questions about the response of protistan microzooplankton (ciliates) to “stressed” phytoplankton we used the Flow-Cam and an inverted microscope to enumerate and monitor live ciliates from all 12 mesocosms. We explored whether the microzooplankton assemblage changes with their prey, i.e. the “stressed” phytoplankton or whether the ciliates themselves are directly stressed by trace metal depletion or increased CO2.

 

Ciliates are very sensitive. They do not like to be pumped in water masses, squeezed or touched too much. Thus, we sampled mesocosms and fjord water in a very smooth way to keep the ciliates live until inspection with the Flow Cam and the microscope.

…Nancy and Jose on the way to the raft….

…Stella and Jose are carefully performing the sampling practice…

 

Back in the lab: The Flow-Cam is a very useful instrument to analyze live plankton, especially ciliates which are pretty sensitive to any fixative. In the Flow-Cam the live organisms are photographed and counted while flowing through a thin cuvette.

…when Stella was tired to feed the Flow Cam with new live samples Tanya took over…

 

At the beginning of the experiment we filled the mesocosms with fjord water, that was full of diatoms and we found some ciliates (orange frame)…day 1

 

In the middle of the experiment, all kinds of ciliates and phytoplankton developed, depending on different conditions in the mesocosms. Here you can see for example the control-mesocosm and the low iron-mesocosm on day 11. Ciliates are surrounded by a red frame.
…control mesocosm, day 11…

…low iron mesocosm, day 11…

 

The phytoplankton composition at the end of the experiment differed distinctly between the mesocosms. While the the control-mesocosm was full of small flagellates and large dinoflagellates (Ceratium longipes), the low-iron mesocosm was dominated by Emiliania huxleyi.
… control mesocosm, day 21…

…low iron mesocosm, day 21…

 

Most of the ciliates were gone at the end…were they stressed?

We will find it out when we analyse all the data…!

Cheers,

Stella & Tanya

Meso-DINNER


Farewell dinner all-together. We had a delicious dinner (as always). No cooking teams this time. All of us cooked a special dish and we had a great time, laughing, joking, and enjoying a lot!



Experiment Over

The experimental part is now over. Today has been the day of taking the bags out of the raft and clean them. Last samples have been taken and a whole load of analyses awaiting to be performed in our labs.

There were mainly three tasks today: 1) take the last total zooplankton from the bags, 2) take the bags out, 3) clean the bags. Although we could add another one: start packing the scientific material.

Part of the team already left. We wish all the best to Tanya, Nancy and Jose Antonio. Some others are leaving  tomorrow, and the rest, few days later, although a small number of us have still one month more to go.

When lids were taken out, it was quite obvious our success in producing differences in E. huxleyii bloom performance.

The “milky” look of some bags was due to a really high concentration of E. huxleyii cells (over 100,000 per mL).

Others were not able to bloom as much, as you can clearly observe in the following picture!

This was what we see outside, but now look  how the huge bags are deployed underwater.

 

For taking the zooplankton out of the bags, after manual resuspension, a net was immersed and pulled out. The water in the bags were released to the fiord, producing a semi natural bloom that was readily diluted.

The final feeling was satisfaction for carrying out a large experiment with nice preliminary and promising results. Not only science but people, weather, food and all help from the University of Bergen has been much appreciated and enjoyed.

A Sea of Tranquility

So far we are about to end the experiments and we are glad the weather has been really good overall. The time out of the lab we could enjoy beautiful landscapes, and eternal sunsets. This time of the year it is difficult to know by when the sunset is over and the sunrise has just started.

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Tiny Inhabitants of the Fjord

The water from the fjord contains a great diversity of  phytoplankton species. When the experiment started, there were mostly diatoms, but representatives of many other groups could be observed as well. Once nutrients were added to the mesocosms (nitrate and phosphate), Skeletonema costatum became the dominant species for a few days, but they started to disappear as soon as Emiliania huxleyii was growing exponentially reaching high numbers in some of the treatments but not in all of them. Certainly, E. huxleyii performes very different depending on CO2 conditions!

The large dinoflagellate Ceratium was also present in big numbers during a good part of the experiment

Pictures below were taken by Tanya Tsagaraki at the Electron Microscopy Lab of the University of Bergen (Norway)

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Grazers in a bag

We are also interested in  investigating possible differences in copepod feeding due to difference in prey physiology.  We want to test whether different pH and different iron availability will affect the specific feeding of the copepod Calanus finmarchicus on coccolithophores Emiliania huxleyi. We will perform gut content analysis on copepods incubated inside the mesocosms using E. huxleyi  specific primers and real time quantitative PCR (qPCR).

Copepods are collected in the fjord in front of the marine Station using a 333µm plankton net with non-filtering cod end. Mature females of Calanus finmarchicus are sorted and transferred inside plastic cages filled with filtered sea water . These plastic cages will be then incubated inside each mesocosm for 24 hours to allow copepods to feed. After this incubation period, each cage is  removed from the mesocosm,and  copepods are anesthetized for further processing.

We plan to perform a minimum of three experiments. One before the E. huxleyi bloom, one during the bloom and one in the post-bloom phase.