We ran a heatwave experiment at two salinities under eutrophic conditions with 4 replicates of each treatment at [METU Mesocosm System](https://www.aquacosm.eu/mesocosms/metu-mesocosm-system). The experiment was conducted at two different localities, with contrasting climatic conditions: Ankara (Semi-arid, steppe and cold climate  (BSk), mean temperature of 12.6°C); and Mersin (Mediterranean, temperate climate with dry and hot summer (Csa), mean temperature of 20.1°C) (Figure 1).  

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![Figure 1. The geographical location (A) and an aerial view of the mesocosm facilities used for the heatwave experiment with two contrasting salinities in  Ankara  (B)  and  Mersin (C). Photos: B – Cihelio Amorim; C - Korhan Özkan. ](https://storage.googleapis.com/aq-cms-content/location_ank_mer_1_ae642fa535/location_ank_mer_1_ae642fa535.jpeg)

<div class="photo-credit">Figure 1. The geographical location (A) and an aerial view of the mesocosm facilities used for the heatwave experiment with two contrasting salinities in Ankara (B) and  Mersin (C). Photos: B – Cihelio Amorim; C - Korhan Özkan. </div>
</div>

During the first three weeks of the experiment, there was no heating in all mesocosms, followed by two weeks of a heatwave, with a 6ºC increase in half of the mesocosms. Then the mesocosms were monitored for the next three weeks during the recovery period with no heating in all mesocosms. The two salinities selected were: 4 ppt and 40 ppt. At lower salinities, fish (*Alburnus alburnus*) was added and survived during the entire experiment, whereas at higher salinity, Artemia was added but survived only in the first weeks. The mesocosms have 30cm of sediment and submerged macrophytes (Ruppia spp.). The salinity in all mesocosms was adjusted one month before the start of the experiment through the additions of NaCl and Na2SO4. After that, plankton and sediment inoculums from systems with different salinities were added in equal amounts to all mesocosms. 

The sampling of the mesocosms was conducted twice a week. Nutrient loading, water level adjustment, as well as salt dosing/adjustment were carried out weekly. The experiment started on 29th August and ended on 3rd November (Figure  2). Several other side experiments were conducted in Ankara Mesocosms facility by [AQUACOSM-plus TAs](https://www.aquacosm.eu/transnational-access). Those experiments aimed to understand the effects of zooplankton or Artemiagrazing on phytoplankton and the impacts of nutrient additions (nitrogen, phosphorus, and silica) on phytoplankton. The experiments were performed before, during and after the heatwave. 

The measured variables included standard physicochemical variables, major ions, phytoplankton, ciliates, HNF, zooplankton, diel-O2-metabolism, GHG release, metagenomic samples (bacteria/ eukaryotes), pigments, DOC/TOC, among others.

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![Figure  2. The general design of the mesocosms and temperature variation in the treatments with ambient temperature and heated mesocosms in Ankara and Mersin mesocosm facilities.](https://storage.googleapis.com/aq-cms-content/a207b161_e5d9_4417_9f47_4ea2f33b24c4_resized_b3d94cb4f6/a207b161_e5d9_4417_9f47_4ea2f33b24c4_resized_b3d94cb4f6.jpg)

<div class="photo-credit">Figure 2. The general design of the mesocosms and temperature variation in the treatments with ambient temperature and heated mesocosms in Ankara and Mersin mesocosm facilities.</div>
</div>



thumbnail_location ank mer news post featured image.jpeg

location ank mer news post featured image.jpeg

We ran a heatwave experiment at two salinities under eutrophic conditions with 4 replicates of each treatment at METU Mesocosm System. 

Heatwave experiment in mesocosm systems with contrasting salinities

Within AQUACOSM-plus, some of the Grand Challenges for aquatic ecosystems (e.g. eutrophication, global warming, salinisation, greenhouse gas emissions) will be investigated by mesocosm experimentation. Within WP 8.1 (Led by Ludwig-Maximilians-Universitaet Muenchen) we performed an experimental investigation of Grand Challenges using a mobile and lightweight mesocosm system (developed earlier in this project, in WP 7.1, by the same partner) and cost-efficient sensor system.

Within[ AQUACOSM-plus](https://www.aquacosm.eu/aquacosm-plus), some of the Grand Challenges for aquatic ecosystems (e.g. eutrophication, global warming, salinisation, greenhouse gas emissions) will be investigated by mesocosm experimentation. Within [WP 8.1](https://www.aquacosm.eu/aquacosm-plus/work-packages) (Lead by [Ludwig-Maximilians-Universitaet Muenchen](https://www.lmu.de/de/index.html)) we performed an experimental investigation of Grand Challenges using a mobile and lightweight mesocosm system (developed earlier in this project, in WP 7.1, by the same partner) and cost-efficient sensor system.

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![Mobile lightweight mesocosm system setup for pelagic mesocosms. In total 6 mesocosms, where 3 are covered with red foil. Yellow floaters can hold 500kg each and prevent higher waves.](https://storage.googleapis.com/aq-cms-content/Foto1_resized_23cb608919/Foto1_resized_23cb608919.jpeg)

<div class="photo-credit">Figure 1: Mobile lightweight mesocosm system setup for pelagic mesocosms. In total 6 mesocosms, where 3 are covered with red foil. Yellow floaters can hold 500kg each and prevent higher waves. Credit: Maria Stockenreiter</div>
</div>

Among many other effects, global warming often has a positive effect on the development of cyanobacterial blooms, especially in shallow lakes. Due to the faster warming of the water column in spring, a stronger and more shallow stratification can establish. Studies show that such changes in stratification can have a lasting effect on the composition of the phytoplankton community. Very often, an increased risk of cyanobacterial blooms is mentioned in connection with warming and simultaneous eutrophication. Our own studies, however, show that even the sole change in stratification can lead to increased cyanobacterial blooms. Phytoplankton at shallow mixing depth is confronted with an altered light climate compared to deeper mixing. Phytoplankton at shallow mixing depths is exposed to a broader light spectrum and, thus, more red light. The consequence, according to theoretical predictions and a previous mesocosm experiment, is that this leads to increased cyanobacterial abundance. The reason for this is the ability of cyanobacteria to use the red spectrum wavelengths of light much better for photosynthesis than other phytoplankton. Previous experiments tried to reveal this in mesocosm experiments with mesocosms of different depths. However, different depth mesocosms pose a problem of holding different water volumes, which might also strongly influence nutrient availability and temperature regimes and, therefore, biomass. One way to avoid this is to actively change the incident light spectrum into the mesocosms while maintaining the same experimental volume. For this purpose, we established a mesocosm setup that had constant experimental volume but manipulated the red-light distribution across experimental treatments. 

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![Installing sensor systems with solar panels.](https://storage.googleapis.com/aq-cms-content/Foto2_resized_2952d86680/Foto2_resized_2952d86680.jpg)

<div class="photo-credit">Figure 2: Installing sensor systems with solar panels. Credit: Eti Levi</div>
</div>

Another Grand Challenge is the emission of greenhouse gases from ponds and lakes. Experimental testing of the role of aquatic systems in greenhouse gas emissions and carbon uptake is critical to understand the driving mechanisms of gas fluxes between aquatic systems and the atmosphere. CO2 dynamics vary over short time scales and CH4 emissions in shallow waters are dominated by ebullition, which is episodic in nature and discrete in space and time. Reliable estimation requires near-continuous sampling. A prototype of a cost-effective sensor system consisting of a measuring chamber, a sensor package and a flushing mechanism capable of such near-continuous measurement of CO2, and CH4 gas fluxes in mesocosm experiments was developed in WP 7 (Lead by the [Aarhus Universitet](https://www.au.dk/en)). Recent research opened the question of how strong cyanobacteria are involved in the above-described gas fluxes. Hence, we combined the approach of inducing cyanobacterial blooms by light quality manipulations with high-frequency measurements of CO2 and CH4. For that, we installed 12 mesocosms and the necessary sensor units in the shallow Pike Lake (Romanian: Lacul Stiucilor), Transylvania, Romania and performed the experiment with researchers from the Institute of Biological Research Cluj ([ICBCN](https://english.icbcluj.ro/)), Romania. Six of the enclosures were pelagic mesocosms, six also enclosed the sediment (benthic-pelagic). The experiment lasted four weeks; stay tuned for the outcome.

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![One sensor system for each mesocosm. Lifting device for swimming chamber where sensors are attached. Each system has a control device connected to a solar panel. ](https://storage.googleapis.com/aq-cms-content/Foto3_resized_6e0b04cf79/Foto3_resized_6e0b04cf79.jpg)

<div class="photo-credit">Figure 3: One sensor system for each mesocosm. Lifting device for swimming chamber where sensors are attached. Each system has a control device connected to a solar panel. Credit: Eti Levi</div>
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Mobile light weight mesocosm system setup for pelagic mesocosms. In total 6 mesocosms, where 3 are covered with red foil. Yellow floaters can hold 500kg each and prevent for higher waves.

thumbnail_feature image aqplus news.jpeg

feature image aqplus news.jpeg

Grand Challenges for aquatic ecosystems (e.g. eutrophication, global warming, salinisation, greenhouse gas emissions) will be investigated by mesocosm experimentation.

MesoPike- experimentally testing 'Grand Challenges' with mobile light weight mesocosms and sensor systems

MesoPike- experimentally testing 'Grand Challenges'

It was the end of February 2022, I was at home with my daughter Maria (7 months old at the time), on a crazy day of insanity and laughter, when I read Vivi’s mail (Paraskevi Pitta) asking me to talk on the phone when I had some free time. She said, ‘I want to ask you something’. That’s how the discussion to submit a proposal to [JERICO-S3 Transnational Access](https://www.jerico-ri.eu/ta/) to participate in the upcoming mesocosm experiment at the [SYKE Marine Research Center facility](https://www.aquacosm.eu/mesocosm/syke-mrc-marine-research-centre-mesocosm-facility/) in Finland began.

It was the end of February 2022, I was at home with my daughter Maria (7 months old at the time), on a crazy day of insanity and laughter, when I read Vivi’s mail (Paraskevi Pitta) asking me to talk on the phone when I had some free time. She said, ‘I want to ask you something’. That’s how the discussion to submit a proposal to [JERICO-S3 Transnational Access](https://www.jerico-ri.eu/ta/) to participate in the upcoming mesocosm experiment at the [SYKE Marine Research Center facility](https://aquacosm.netlify.app/mesocosms/syke-mrc-marine-research-centre-mesocosm-facility) in Finland began. I remember listening carefully to Vivi as she explained the focus of the experiment (heat wave effects in the Baltic Sea plankton community), what we would be working on, when it would start and how long it would last (about 2 weeks), when the deadline for submitting the proposal was, who would go and so on. All good, with some questions (which were reasonable), but all good. Except for one thing that was running around in my mind and made everything doubtful – what about Maria?

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![small child playing in sand](https://storage.googleapis.com/aq-cms-content/Maria_at_the_playground_1_scaled_e1667404566644_a2c73bb783/Maria_at_the_playground_1_scaled_e1667404566644_a2c73bb783.jpg)

<div class="photo-credit">Photo credit: Anastasia Tsiola</div>
</div>

Vivi had read my mind from the beginning and before she had even finished the description, she eased my worries by simply saying, ‘I’ll do the babysitting!’. Things were starting to fall into place and I could make plans again. The truth is, it is one thing for Anastasia to become a ‘mother’, but it is another thing for the mother to become ‘Anastasia’ again. I imagine this is something that many female scientists have experienced, an otherwise normal process that may take time, with anxiety about the future, anxiety about the CV and its ups and downs, regret over a missed opportunity or other negative emotions, that are simultaneously mixed in a magical way with the overwhelming feelings of holding your baby in your arms.

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![man watching child play in field](https://storage.googleapis.com/aq-cms-content/Maria_and_Dimitris_at_the_meadows_1_1_e1667404629506_9fd970c866/Maria_and_Dimitris_at_the_meadows_1_1_e1667404629506_9fd970c866.jpg)

<div class="photo-credit">Photo credit: Anastasia Tsiola</div>
</div>

With the support of Vivi and Iordanis Magiopoulos from the [Hellenic Centre for Marine Research (HCMR)](https://www.hcmr.gr/en/), who from the first moment declared and really offered their best during our stay in Helsinki, and also with the enormous help from the [SYKE](https://www.syke.fi/en-US) staff (especially Katri Kuuppo, Jukka Seppälä, and Timo Tamminen), our participation in the experiment became a reality! Maria was there too, she not only explored parks, playgrounds, the zoo, and vast meadows, but also the university campus and the mesocosms facility! Our TA application was accepted by [JERICO-S3](https://www.jerico-ri.eu/) and we arrived in Helsinki on August 19th to prepare for the [‘In-door mesocosm experiment studying how heat wave affects the late summer Baltic Sea plankton community’](https://aquacosm.netlify.app/news/article/effects-of-consecutive-heat-waves-on-the-resistance-resilience-and-recovery-of-marine-plankton-communities-heat-waves) that would be carried out jointly by the [JERICO-S3](https://www.jerico-ri.eu/projects/jerico-s3/) and [AQUACOSM-plus](https://aquacosm.netlify.app/aquacosm-plus) projects. Vivi, Iordanis, and I undertook to collect samples for viral and bacterial cell enumeration by flow cytometry and microplankton by inverted microscopy back at [HCMR](https://www.hcmr.gr/en/). We also prepared 24-hour incubations for the estimation of viral production rates by the viral reduction method, working shifts until 22:00 at night to check whether the temperature increase affects the viral activity. Fifteen challenging days followed in a perfectly organised laboratory and a very friendly, cheerful, and helpful local team who bonded nicely with external participants. I met again dear colleagues from past experiments: Behzad Mostajir (I also met his wife Francesca Vidussi and they told stories about their daughters!) with familiar faces from their team at [CNRS-MARBEC MEDIMEER](https://aquacosm.netlify.app/mesocosms/medimeer-mediterranean-platform-for-marine-ecosystem-experimental-research) in Sète, and Jens Nejstgaard, Stella Berger, and their team from the [IGB LakeLab](https://aquacosm.netlify.app/mesocosms/igb-lakelab) in Lake Stechlin, Neuglobsow. In addition to Finnish, Maria heard English, Italian, German, and Spanish, walked around the whole building many times, learned to go downstairs with her butt, mopped and crawled many corridors at the university, ate special delicacies and cheeses, played the piano in a restaurant, saw a tiger at the zoo, she scribbled with markers on the board where the instructions for the experiment were written, always safely away from the labs where the chemical reagents were kept, and always away from work she might interfere with. She was covered at night with the bed sheets lent to us by Katri and Timo’s grandchildren and received all the love and care that any child deserves from people around her, thus leaving time for mom to run an experiment, read a paper, and participate in a meeting to discuss graphs!

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![two people holding a small child at the zoo, looking at a tiger](https://storage.googleapis.com/aq-cms-content/Maria_Vivi_and_Dimitris_watching_the_tiger_1_scaled_e1667404710838_6bd6d95b87/Maria_Vivi_and_Dimitris_watching_the_tiger_1_scaled_e1667404710838_6bd6d95b87.jpg)

<div class="photo-credit">Photo credit: Anastasia Tsiola</div>
</div>

Finally, the answer to Vivi’s email (‘I want to ask you something’) was ‘Yes, I want to go to this experiment’, but it would not have come true without the support of the whole team and my husband Dimitris who was also there taking care of Maria during the first days. I wish that all women who are in science first and foremost ‘ask for’ and then ‘receive’ the help they need to make their dreams come true.

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![scientist with bread in his mouth playing with baby crawling on the floor](https://storage.googleapis.com/aq-cms-content/Maria_meets_Jens_1_310e972225/Maria_meets_Jens_1_310e972225.jpg)

<div class="photo-credit">Photo credit: Anastasia Tsiola</div>
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thumbnail_little maria zoo tiger resized featured image.jpg

little maria zoo tiger resized featured image.jpg

I wish that all women who are in science first and foremost ‘ask for’ and then ‘receive’ the help they need to make their dreams come true.

Participation in a mesocosm experiment at SYKE-Helsinki: HCMR team and little Maria

mesocosm experiment at SYKE-Helsinki: HCMR team and little Maria

Participation in a mesocosm experiment at SYKE-Helsinki: HCMR team and little Maria 

Many ecosystems, including lakes, are exposed to increasing intensities and frequencies of extreme weather events due to climate change, including heavier and flashier rainfalls and prolonged drought periods in summer. This results in more variable resource (nutrient and carbon) regimes that encompass stochastic to periodic fluctuations in environmental conditions, gradual environmental changes as well as pulse events, i.e. abrupt unpredictable changes in resources. How this affects plankton communities and ecosystem processes are currently still unclear.

The mesocosm experiments were conducted in two lakes in Sweden (Lake Erken and Lake Bolmen) in a fully synchronised way using the [SITES AquaNet infrastructure](https://aquacosm.netlify.app/mesocosms/sites-aquanet). We used exactly the same set-up, sampling design and autonomous sensor system in mesocosms installed in both lakes. This gives the unique possibility to compare the treatment effect on a variety of different response variables (see below) between the two lakes, which differ, for example, in water colour and nutrient concentrations.

More specifically we focused on the effects of different run-off scenarios focusing particularly on differences in resource pulse variability (including organic and inorganic nutrients) over a time period of 6 weeks in the summer of 2022. This was done by manipulating the intensity and frequency of DOC (peat extract) and inorganic nutrients (N, P) added to the mesocosms while keeping the total amount of added DOC and nutrients constant. We ‘simulated’ a rainfall period lasting for 3 weeks, followed by a recovery period of approx. 2 weeks to see if the effects of the runoff manipulations persisted beyond the simulated rainfall period. Changes in zoo-, phyto-, and bacterioplankton composition and biomass/abundance, DOM composition, metabolism, greenhouse gas emissions, and nutrient stoichiometry in response to the different run-off treatments are analysed by the project participants.

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![composite image of scientists working at mesocosm facility](https://storage.googleapis.com/aq-cms-content/aquacosm_post_composite_image_1_86b0c290e0/aquacosm_post_composite_image_1_86b0c290e0.png)

<div class="photo-credit">Filling of mesocosm in lakes Bolmen (left) and cleaning of sensor system in Lake Erken (right).</div>
</div>


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![composite image of scientists working at mesocosm facility](https://storage.googleapis.com/aq-cms-content/mesocosm_news_image_2_redo_e1665499612357_0635e5d403/mesocosm_news_image_2_redo_e1665499612357_0635e5d403.png)

<div class="photo-credit">DOC/nutrient additions (left) and mesocosm sampling (right) done during the experiment.</div>
</div>

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![composite image of scientists working at mesocosm facility](https://storage.googleapis.com/aq-cms-content/mesocosm_aquacosm_image_2_redo_try_3_e1665500905928_1_a5bddd8b8a/mesocosm_aquacosm_image_2_redo_try_3_e1665500905928_1_a5bddd8b8a.png)


<div class="photo-credit">Flux chambers used to measure fluxes of greenhouse gases and volatile organic substances from the mesocosms (top left), sample preparation (top right) and filtrations (bottom left) in the lab and sampling of the mesocosms for grazing experiments (bottom right).</div>
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The experiment brought together an international team of experts and students from Spain, Turkey, Ireland, Hungary and the Czech Republic funded by the [Transnational Access (TA)](https://aquacosm.netlify.app/transnational-access) program of[ AQUACOSM-plus](https://aquacosm.netlify.app/) and participants from AQUACOSM-plus partners at [IGB](https://www.igb-berlin.de/en) (Germany), [Oldenburg University](https://uol.de/) (Germany), and [Uppsala University](https://www.uu.se/en). Finally, researchers from [Lund University](https://www.lunduniversity.lu.se/) (Sweden) also joined the project.


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![group photo of scientists](https://storage.googleapis.com/aq-cms-content/group_picture_1_scaled_e1665134106999_ce98a05ebf/group_picture_1_scaled_e1665134106999_ce98a05ebf.jpg)

<div class="photo-credit">Group picture with the majority of project participants. Upper row from left to right: Kevin Jones, (<a href="https://www.lunduniversity.lu.se/" target="_blank" rel="noopener noreferrer">Lund University</a>, SE), Don Pierson (<a href="https://www.uu.se/en" target="_blank" rel="noopener noreferrer">Uppsala University</a>, SE), Emma Gray (<a href="https://www.atu.ie/" target="_blank" rel="noopener noreferrer">Atlantic Technological University</a>, IE, TA user), Nils Kreuter (Uppsala University, SE), Bence Buttyán (<a href="https://www.elte.hu/en/" target="_blank" rel="noopener noreferrer">Eötvös Loránd University</a>, HU, TA user), Bence Gergácz (Eötvös Loránd University, HU, TA user), Anika Happe (<a href="https://uol.de/" target="_blank" rel="noopener noreferrer">University of Oldenburg</a>, DE), Juha Rankinen (<a href="https://www.swedenwaterresearch.se/en/" target="_blank" rel="noopener noreferrer">Sweden Water Research</a>, SE), Gabriela Ágreda López (Uppsala University, SE), Stella Berger (<a href="https://www.igb-berlin.de/en" target="_blank" rel="noopener noreferrer">IGB Berlin</a>, DE), Eleni Charmpila Oppong (<a href="https://cuni.cz/uken-1.html" target="_blank" rel="noopener noreferrer">Charles University</a>, CZ, TA user), Jimmy Clifford Oppong (Charles University, CZ, TA user), Nusret Karakaya (<a href="http://www.ibu.edu.tr/en" target="_blank" rel="noopener noreferrer">Bolu Abant Izzet Baysal University</a>, TR, TA user), Pelin Ertürk Ari (Bolu Abant Izzet Baysal University, TR, TA user), Akif Ari (Bolu Abant Izzet Baysal University, TR, TA user). Lower row from left to right: Angela Pedregal (<a href="https://www.icra.cat/index.php?lang=3" target="_blank" rel="noopener noreferrer">ICRA Catalan Institute for Water Research</a>, TA user), Johanna Sjöstedt (Lund University, SE), Silke Langenheder (<a href="https://www.uu.se/en" target="_blank" rel="noopener">Uppsala University</a>, SE), Jens Nejstgaard (IGB Berlin, DE), William Colom (Uppsala University, SE).</div>
</div>


For more information contact Silke Langenheder (UU), <a href="mailto:silke.langenheder@ebc.uu.se">silke.langenheder@ebc.uu.se</a>. 

Pictures were provided by Matilda Andersson (<a href="https://www.slu.edu/" target="_blank" rel="noopener noreferrer">SLU</a>), Stella Berger (IGB), and Nusret Karakaya (<a href="http://www.ibu.edu.tr/en" target="_blank" rel="noopener noreferrer">Bolu Abant Izzet Baysal University</a>).






thumbnail_group picture feature image.JPG

group picture feature image.JPG

Synchronised experiment to investigate consequences of run-off variability on plankton communities in Swedish lakes

experiment - consequences of run-off on plankton in Swedish lakes 

If you go to the coastline and look far away at the open sea, you will notice the beautiful scene of the sky and the sea to be connected. Even from the early days of our planet, the atmosphere and the oceans were in constant and close connection, exchanging gases and particles, and we can now say that their current form is mainly due to their 4-billion-year relationship.

We know that the deposition of atmospheric particles is an important source of macro-nutrients and micro-trace elements in the ocean. Especially in low-nutrient low-chlorophyll (LNLC) areas, such as the Eastern Mediterranean Sea, the deposition of aerosols stimulates primary and secondary productivity. It affects ecosystem function and diversity up to the copepod level. Those effects can be more significant when Saharan dust, rich in phosphorus and nitrogen, is deposited in the sea, after strong southern winds. However, in most current studies, these observations have been attributed solely to nutrient addition, as if the atmosphere contains only nutrients. 

It is well known that aerosols also contain microbes that originated from the Earth’s surface. These microbes can travel globally via air currents and survive in the atmosphere, presenting metabolic activity and even replication. Eventually, airborne microbes return to the land surface or end up in the sea through the mechanisms of dry and (mainly) wet (precipitation of rain, snow, and hail) deposition. But we don’t know what is ‘happening’ to them upon their deposition into the ocean or how they could affect the marine ecosystem. 

In May 2022, two Research Infrastructure Networks, an experimental one – [AQUACOSM-plus](https://aquacosm.netlify.app/aquacosm-plus), and an observational one – [Jerico-S3](https://www.jerico-ri.eu/projects/jerico-s3/), closely collaborated to study the effects of various atmospheric deposition scenarios on an ultra-oligotrophic marine ecosystem. To this end, scientists from Switzerland, France, Italy, Finland, Spain, Austria, Norway, and Argentina gathered at the mesocosm facility [CretaCosmos](https://aquacosm.netlify.app/mesocosms/cretacosmos) of the [Hellenic Centre for Marine Research](https://www.hcmr.gr/en/) (HCMR), located on the north coast of Crete, Greece. Due to its location, CretaCosmos is the only place in Europe where truly oligotrophic waters can be studied in a mesocosm facility, combined with excellent laboratory access.

Water from the north coast of Crete was collected and distributed into 9 mesocosm bags of 3.5 m3 each. At the same time, aerosol collectors were installed by HCMR, the [University of Crete](https://en.uoc.gr/)-Greece, [EPFL-Switzerland](https://www.epfl.ch/en/), and the [University of Oslo](https://www.uio.no/english/)-Norway in two locations. One Urban and one Rural site; the first one was placed at the centre of Heraklion city (a 180,000 inhabitants coastal city), the second one placed at a remote village of South-East Crete (100 people, at 700 m altitude surrounded by olive groves and pine forests). The aerosol samples collected from the above sites were inoculated inside the mesocosms directly, without any further processing, and they were considered ‘live’, i.e. containing viable microbes.

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![aerosol samplers rural site image](https://storage.googleapis.com/aq-cms-content/Aerosol_Samplers_Rural_Site_1_scaled_e1664188223342_d3966ed6f1/Aerosol_Samplers_Rural_Site_1_scaled_e1664188223342_d3966ed6f1.jpg)

<div class="photo-credit">Figure 1. The installation of High-Vol and Coriolis aerosol samplers at the Rural Site (Orino Ierapetras, Crete, Greece). Credit: I. Magiopoulos.</div>
</div>

In addition, Saharan dust was collected from the Heraklion centre, immediately after a major dust event which occurred two weeks prior to the experiment, and was used to examine and compare the effects of these two different types of aerosols on the marine environment.

During this 2 week experiment, the full microbial and plankton communities, from viruses to copepods, were studied. Scientists from the [University of Vienna](https://www.univie.ac.at/en/) measured the viral production, a team from the [University of Vigo](https://www.uvigo.gal/en) focused on the primary and bacterial activity measurements, while the microplankton community was studied using both imaging flow cytometers, from the [Mediterranean Institute of Oceanology](https://www.mio.osupytheas.fr/en), Marseille, and HCMR, and conventional microscopy. Finally, metagenomic analysis, with special emphasis on potential pathogens and antibiotic-resistant genes, was undertaken by [MEG-IRSA](http://www.meg.irsa.cnr.it/) in Verbania. 

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![the mesocosm bags and in situ incubation for bacterial respiration ](https://storage.googleapis.com/aq-cms-content/The_mesocosm_bags_and_insitu_incubation_for_bacterials_respiration_1_scaled_e1664188438276_9214697574/The_mesocosm_bags_and_insitu_incubation_for_bacterials_respiration_1_scaled_e1664188438276_9214697574.jpg)

<div class="photo-credit">Figure 2. The mesocosm bags of the CretaCosmos facility and the in-situ incubation of glass bottles for the measurement of bacterial respiration. Credit: I. Magiopoulos</div>
</div>

Two additional smaller experiments took place, one studying the chemical composition, biological content, and cloud-forming potential of the aerosol emitted from the mesocosms, while, in the second one, a series of in-situ marine sensors developed by the [Jerico-S3](https://www.jerico-ri.eu/) project and [Chelsea Technologies Inc](https://chelsea.co.uk/). were tested in the challenging ultra-oligotrophic environment of the Eastern Mediterranean.

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![in situ marine sensors from Jerico](https://storage.googleapis.com/aq-cms-content/In_situ_Marine_sesonrs_from_Jerico_1_scaled_e1664188632181_ca9c80ae6a/In_situ_Marine_sesonrs_from_Jerico_1_scaled_e1664188632181_ca9c80ae6a.jpg)

<div class="photo-credit">Figure 3. Some of the in-situ marine sensors that were deployed by the Jerico-S3 project. Credit: I. Magiopoulos.</div>
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![group photo of the team outdoors](https://storage.googleapis.com/aq-cms-content/The_Team_1_scaled_e1664188885463_cb25484d64/The_Team_1_scaled_e1664188885463_cb25484d64.jpg)

<div class="photo-credit">Figure 4. The AEROSea experiment team. Credit: I. Magiopoulos.</div>
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For more information, please contact Iordanis Magiopoulos ([iordanis@hcmr.gr](mailto:iordanis@hcmr.gr)).












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We know that the deposition of atmospheric particles is an important source of macro-nutrients and micro-trace elements in the ocean.

Atmospheric deposition in the sea: is it manna from heaven?

Climate change is causing increasingly frequent heat waves, which not only hit land areas, but also coastal seas. An increase in the water temperature affects the life of plankton and the pathways of nutrients and carbon. Because of the sporadic nature of the heatwaves, their effects are hitherto poorly known. Studying their multifaceted and complex effects on coastal seas requires an interdisciplinary approach.

Climate change is causing increasingly frequent heat waves, which not only hit land areas, but also coastal seas. An increase in the water temperature affects the life of plankton and the pathways of nutrients and carbon. Because of the sporadic nature of the heatwaves, their effects are hitherto poorly known. Studying their multifaceted and complex effects on coastal seas requires an interdisciplinary approach.

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![IFCB plankton image](https://storage.googleapis.com/aq-cms-content/IFCB_image_e1662108278346_3_63296750df/IFCB_image_e1662108278346_3_63296750df.png)

<div class="photo-credit">IFCB plankton image</div>
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Long-term coastal observations and the use of novel sensors in the JERICO-RI are able to reveal the frequency and magnitude of heat waves and provide a basic understanding of bulk changes in plankton communities. A more in-depth understanding of the heatwaves on planktonic processes requires further targeted research, e.g., the experimental approach by AQUACOSM-plus, in which mesocosms studies with active manipulation of natural plankton communities are used.

In August 2022, we monitored a heatwave in the Gulf of Finland, by continuous measurements of several parameters at the [JERICO-S3 Pilot Supersite](https://www.jerico-ri.eu/projects/jerico-s3/pilot-supersites/gulf-of-finland-pilot-supersite/) ferries and fixed platforms.

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![IFCB Scientist, Kaisa](https://storage.googleapis.com/aq-cms-content/IFCB_Kaisa_on_the_floor2_683x1024_1_267f743c56/IFCB_Kaisa_on_the_floor2_683x1024_1_267f743c56.jpg)

<div class="photo-credit">IFCB Scientist, Kaisa</div>
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At the same time (22.8.-2.9. 2022), we conducted a mesocosm experiment using the [AQUACOSM-plus indoor mesocosm facility](https://www.aquacosm.eu/mesocosm/syke-mrc-marine-research-centre-mesocosm-facility/) at the [Finnish Environment Institute SYKE](https://www.syke.fi/en-US/Research__Development/Sea), Helsinki. In the experiment, we exposed natural plankton communities from the Gulf of Finland to elevated temperatures.

With the support of the Transnational Access of JERICO-S3, international groups from [Lake Lab](https://www.lake-lab.de/index.php/welcome-to-the-lake-laboratory.html) of the Leibniz Institute of Freshwater Ecology and Inland Fisheries IGB (Germany), the [Hellenic Centre for Marine Research HCMR](https://www.hcmr.gr/en/) (Greece) and the [National Centre for Scientific Research CNRS](https://www.cnrs.fr/en/cnrs) (France), participated in the experiment jointly with the scientists of SYKE.

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![Katerina Pasi with the Mesocosm](https://storage.googleapis.com/aq-cms-content/Katerina_Pasi_Mesocosm_1024x683_1_0b8eb36ef5/Katerina_Pasi_Mesocosm_1024x683_1_0b8eb36ef5.jpg)

<div class="photo-credit">Katerina Pasi with the Mesocosm</div>
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The mesocosm experiment, which was carried out indoors, involved high-frequency measurements of plankton ecosystem structure and functioning using the autonomous sampling and analysis instrument [AquaBox](https://www.youtube.com/watch?v=r9SqFst3Q-w), sensors and imaging systems, as well as the kinetics of planktonic organisms from viruses to zooplankton. The unique combination of collaborative observations and experimentation greatly facilitated the research of this complex environmental challenge.

The experiment is the third in the series of JERICO-S3-AQUACOSM-plus collaborations. The previous experiments were carried out in the NW Mediterranean and the Cretan Sea, where the effects of riverine loads and air-borne aerosols on plankton ecosystems were studied.

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![Group photo from the experiment](https://storage.googleapis.com/aq-cms-content/Group_picture_010922_1024x603_1_52eb43a9e5/Group_picture_010922_1024x603_1_52eb43a9e5.jpg)

<div class="photo-credit">Group photo from the experiment</div>
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Climate change is causing increasingly frequent heat waves, which not only hit land areas, but also coastal seas. 

Joint AQUACOSM-plus and JERICO-S3 study on Baltic Sea heatwaves

<p>The primary objective of <a href="/transnational-access">Transnational Access (TA)</a> is to provide access to more than 60 different leading and highly complementary mesocosm facilities located at 28 AQUACOSM-plus partners throughout Europe.</p>
<p>The AQUACOSM-plus mesocosm <a href="/mesocosms">facilities</a> represent a cross-section of European aquatic ecosystems ranging from Sub-Arctic to the Mediterranean, from mountains to lowlands, from freshwater to marine, and from ultra-oligotrophic to hyper-eutrophic conditions.</p>
<p>Between 2021 and 2023 AQUACOSM-plus will offer &gt; 13,000 person-days of (TA) to AQUACOSM-plus facilities. Successful TA applicants will be offered access to facilities including logistical, technological and scientific support, specific training as well as travel and accommodation free of charge.</p>
<p>The detailed procedures for the assessment rules, including application and evaluation guidelines, open calls, as well as previous and ongoing TA activities can be found on the AQUACOSM-plus websites.</p>

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AQUACOSM-plus explainer video: What is Transnational Access?

The depletion of oxygen from bottom waters (hypolimnion) of lakes and reservoirs is becoming more frequent because of climate change and eutrophication. Low dissolved oxygen (hypoxia) can release nutrients from sediments and degrade water quality, alter animal behaviour and food web dynamics, and ultimately, alter lake ecosystem function.

Zooplankton influence ecosystem processes, including nutrient cycling and trophic transfer. They also commonly exhibit diel vertical migration (DVM), where they remain in the deeper, darker waters of the hypolimnion during the day to avoid visual predators, and then migrate to near-surface waters (epilimnion) at night to feed on phytoplankton under the cover of darkness. However, loss of oxygen in the hypolimnion can alter DVM and increase diel horizontal migration (DHM), where zooplankton use littoral zones to avoid visual predators and hypolimnetic hypoxia during the day and migrate to open water at night to feed on pelagic phytoplankton.

If hypoxia forces a switch from DVM to DHM, food web interactions and biogeochemical processes may be greatly affected. Climate change and eutrophication are also expected to change zooplankton functional diversity, including traits related to migration (mobility), predation risk and growth/feeding capacity (body size), and ultimately, community- and ecosystem-level processes (e.g., ecosystem respiration, trophic transfer, carbon sequestration). Most research on zooplankton functional diversity has focused on macro space/time scales; fewer studies have evaluated zooplankton functional trait response to short-term environmental and community variability.

We had the privilege to work at “[PLANAQUA](/mesocosms/national-experimental-platform-in-aquatic-ecology-planaqua)” (PLAteforme expérimentale NAtionale en écologie AQUAtique) located at [CEREEP-Ecotron IleDeFrance in Saint Pierre lès Nemours](https://www.cereep.bio.ens.psl.eu/), France, in August 2021. PLANAQUA consists of 16 identical, human-made ponds that are 30 x 15 m, 3 m deep, and have a shallow vegetation zone on the long sides of the ponds. The ponds are arranged in a 2 x 2 factorial design with nutrients (added or not) and predator fish (added or removed) as experimental treatments, and provided an opportunity to test some of our ideas. We sampled the ponds during the day and at night to test whether daily zooplankton migration behaviour is a function of fish community composition and environmental conditions, and whether any observed differences in daily migration behaviour are related to zooplankton functional traits. We expected zooplankton DHM to be more prevalent than DVM under hypolimnetic hypoxic conditions, but behaviour to be mediated by fish community structure through trophic behavioural cascades (Fig 1). Ponds with piscivorous fish predators would enable zooplankton to occupy more open-water habitat because smaller, planktivorous fishes would seek shelter in littoral zones.

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![Schematic representation of the ponds under the 4 treatments](https://storage.googleapis.com/aq-cms-content/aquacosm_news_post_image_1_8668ced15c/aquacosm_news_post_image_1_8668ced15c.png)

<div class="photo-credit">Figure 1. Schematic representation of the ponds under the 4 treatments: nutrients (added or not, rows) and fish (added or removed, columns). Arrows indicate diel horizontal or vertical migration. We expected DVM to be less prominent in the presence of piscivores (panel A) than in the absence of piscivores (panel B), and DHM to be more prominent under low oxygen conditions (panels C and D) than oxygenated conditions (panels A and B). Under low oxygen conditions, we expected DHM to be more prominent in the absence of piscivores (panel D) than in their presence (panel C).</div>
</div>
<p></p>
Each pond was sampled day and night – four ponds for each 24 hour cycle – in early August 2021. We measured environmental conditions by taking vertical profiles of temperature, oxygen, chlorophyll a fluorescence, and other variables in the centre and sides of each lake. We also used a fluoroprobe to evaluate the relative abundances of different phytoplankton groups. We sampled the zooplankton and rotifer communities in the epilimnion and hypolimnion in the centre of the lake, in the epilimnion just outside the littoral zone, and inside the vegetation. The comprehensive sampling will allow us to estimate both vertical and horizontal migration in each pond, and assess movements according to taxonomic and functional groups as related to fish community structure and environmental conditions based on the pond experimental treatments.
<p></p>
We are now processing the zooplankton and rotifer samples. We have a team of undergraduate and graduate students working in our microscope laboratory at the Rubenstein Ecosystem Science Laboratory (University of Vermont, Burlington, VT, USA). In each sample, at least 200 individuals are identified to establish the community composition for the pond at the specific pond location (4 potential locations) and time of the day (2 options, day and night). In parallel, the team meets regularly via zoom to discuss project progress and next steps.
<p></p>
We expect our results will point to future research that explores the consequences of the changes we observe for emergent ecosystem properties.
<p></p>
Our FOAMZ team, in the field and in the lab, includes trainees Antoine Rousseau and Jeanne Bosson, Heather Wander (Virginia Tech), Anna Schmidt (University of Vermont), Gérard Lacroix (PLANAQUA), Sadye Goldfarb (University of Vermont), Sarah Fiorini (PLANAQUA), Jon Doubek (Lake Superior State University), Rosie Chapina (University of Vermont), Rosalie Bruel (iEEES, Paris), and Jason Stockwell (team leader, University of Vermont).

Undergraduates that have processed samples and current students include:

Jack Knight – *Ceratium*

Carissa Finnerty – Rotifers

Althea Deschenes – Rotifers

Izzy Anderson – Rotifers

Elizabeth Beall – Rotifers

Savannah Zigic – Zooplankton

Spencer Mahne – Zooplankton


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![FOAMZ-II The-team-1](https://storage.googleapis.com/aq-cms-content/FOAMZ_II_Image_1_The_team_1_d6e438484e/FOAMZ_II_Image_1_The_team_1_d6e438484e.jpg)

<div class="photo-credit">The team. From the left: Jason Stockwell, Johnathan Dubek, Gérard Lacroix, Carissa Finnerty, Rosalie Bruel, Savannah Zigic</div>
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![FOAMZ-II Sampling-during-the-night](https://storage.googleapis.com/aq-cms-content/FOAMZ_II_Image_5_Sampling_during_the_night_9d1ce403f4/FOAMZ_II_Image_5_Sampling_during_the_night_9d1ce403f4.jpg)

<div class="photo-credit">Zooplankton sampling during the day/night field survey</div>
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![FOAMZ-II Data-processing](https://storage.googleapis.com/aq-cms-content/FOAMZ_II_Image_9_Data_processing_39ceddd39b/FOAMZ_II_Image_9_Data_processing_39ceddd39b.jpg)

<div class="photo-credit">Laboratory picture analysis of collected zooplankton</div>
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Fish and Oxygen-induced Alterations to the Migration of Zooplankton (FOAMZ)

<p>Marine systems are facing an increase in the frequency of extreme events and especially climate change scenarios foreshadow the increase of heat waves in the future. Increasing heat waves can alter planktonic diversity, interactions between different groups, and key processes. According to modelling forecasts for the future increase in the frequency of heat waves, an <em>in situ</em> mesocosm experiment is currently being conducted (end of April and May 2022) at the <a href="/mesocosms/medimeer-mediterranean-platform-for-marine-ecosystem-experimental-research" target="_blank" rel="noopener noreferrer">CNRS-MEDIMER</a> infrastructure (city of Sète in southern France). In this experiment, triplicate <em>in situ</em> mesocosms are heated to +5°C compared to the natural surrounding water temperature for five days and triplicate other <em>in situ</em> mesocosms act as a Control following the natural surrounding water temperature. After this first period of heat wave (HW1), all mesocosms are followed for a period of five days without heating (Post HW1). This experimental protocol is repeated once more with the periods called HW2 and Post HW2. In this way, the planktonic communities will be subjected to two consecutive periods of heat waves and post-heat waves, and the results will be compared with those of the Control mesocosms. In this experiment, two teams, of five and three researchers each, as well as a trainee participate, all supported by the AQUACOSM-plus Transnational Access (pictures below).</p>
<p><br />
<strong>The HEATS-ZOO team:</strong> Sultana Zervoudaki (team leader, GR), Jonna Engström-Öst (Expert, FI), Maria Protopapa (Post-doc, GR), Athanasia Sakavara (PhD, GR), Adriana Koutsandrea (MSc, GR), focusing on the composition, production and feeding of the zooplankton community and estimation of eco-physiological processes, such as oxidative stress and antioxidants in selected dominant zooplankton species. They also manipulate mesozooplankton from the lagoon, incubating them into bottles filled with water from the experimental mesocosms and expect that potential changes in the food quality and community under heat waves will affect the responses of different zooplankton.</p>
<p><br />
<strong>The Heat-VIRBAC team:</strong> Manuel Martinez Garcia (team leader, ES), Maria Alvarez Sanchez (PhD, SP) and Aitana Llorenç Vicedo (PhD, SP), studying viral and cellular metagenomics along with single-cell genomics, including 16S (prokaryotes) and 18S (protist) rRNA gene Illumina and Nanopore Sequence, vesicle abundance and <em>in situ</em> BONCAT-tagging community to monitor metabolically active microbes and viruses. In addition, Katrina Feliciano (FI) participates in this experiment as a trainee.</p>

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![ALL-Partcipants-1200-rotated.jpg](https://storage.googleapis.com/aq-cms-content/ALL_Partcipants_1200_rotated_74402462e3/ALL_Partcipants_1200_rotated_74402462e3.jpg)

<div class="photo-credit">All participants to Heat-Waves project.</div>
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![TA-participants](https://storage.googleapis.com/aq-cms-content/TA_participants_1200_86e5098a25/TA_participants_1200_86e5098a25.jpg)

<div class="photo-credit">TA participants of the Heat-Waves project, from left Jonna Engström-Öst (FI), Adriana Koutsandrea (GR), Athanasia Sakavara (GR), Soultana Zervoudaki (GR), Maria Alvarez Sanchez (ES), Aitana Llorenç Vicedo (ES), Manuel Martinez Garcia (ES), and Katrina Feliciano (FI).</div>
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<p>Project Leaders: Francesca Vidussi and Behzad Mostajir<br />
Pictures provided by @B. Mostajir</p>

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Effects of consecutive heat waves on the resistance, resilience and recovery of marine plankton communities (Heat Waves)

Effects of consecutive heat waves on marine plankton communities

In June 2021, an international mesocosm experiment (Codenamed “BrownMed”) took place at the CretaCosmos mesocosm facility of the Hellenic Centre for Marine Research in Crete, Greece.

The BrownMed experiment was part of the Joint Mesocosm Experiment (JOMEX) organised by the H2020 AQUACOSM project. In this experiment, the brownification of various aquatic ecosystem was studied. And when we say various, we mean various! From lakes in Central Europe to estuaries and coastal marine systems in the Baltic and the Mediterranean Seas.

<p>In June 2021, an international mesocosm experiment (Codenamed “BrownMed”) took place at the <a href="/mesocosms/cretacosmos" target="_blank" rel="noopener noreferrer">CretaCosmos mesocosm</a> facility of the <a href="https://www.hcmr.gr/en/" target="_blank" rel="noopener noreferrer">Hellenic Centre for Marine Research</a> in Crete, Greece.</p>
<p>The BrownMed experiment was part of the Joint Mesocosm Experiment (JOMEX) organised by the <a href="/aquacosm" target="_blank" rel="noopener noreferrer">H2020 AQUACOSM project</a>. In this experiment, the brownification of the various aquatic ecosystems was studied. And when we say various, we mean various! From lakes in Central Europe to estuaries and coastal marine systems in the Baltic and the Mediterranean Seas.</p>
<p><strong>What is brownification you may ask.</strong></p>
<p>By definition, brownification is the process whereby the brown colour of stream and lake water increases. This brown colour of the water is caused by strong absorption of short-wavelength visible solar radiation by dissolved organic matter (DOC), possibly in combination with iron, leached from soils in the catchment. This brown colour of the water causes shading affecting, by that, photosynthesis. Also, the excess of DOC has significant effects on the microbial communities and processes.</p>

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![A Brownification experiment in Crete, Greece](https://storage.googleapis.com/aq-cms-content/A_Brownification_experiment_in_Crete_Greece_image_1_e1649233113133_f74023f463/A_Brownification_experiment_in_Crete_Greece_image_1_e1649233113133_f74023f463.jpg)

<div class="photo-credit">Photo credit: Iordanis Magiopoulos</div>
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<p><strong>What are those effects?</strong></p>
<p>Well, this is what we are looking for!</p>
<p><strong>And how we did it?</strong></p>
<p>We used a common livestock feed, called HuminFeed, that is used in the farms of central Europe; it is full of DOC, inorganic nutrients and metals. This substance leaches to streams and rivers leading to lakes and also in the sea. So the idea was to add this HuminFeed inside the mesocosms and check how the whole microbial food web is affected. And since this substance can travel from freshwater to marine ecosystems, we did the very same experiment in many different mesocosm facilities around Europe in order to see the effects on various ecosystems, and by that to get the big picture of this phenomenon.</p>
<p><strong>But brownification in Crete?</strong></p>
<p>Whoever has visited Crete, a big island in the Eastern Mediterranean Sea, will have noticed that the sea is very transparent, almost colourless. This is because the Eastern Mediterranean Sea is one of the most oligotrophic marine systems of the planet, if not the most oligotrophic. However, there are times, especially in winter after heavy rainstorms, that brownification is formed in some very coastal areas. But still, this is almost nothing compared to the freshwater systems of Continental Europe and the North and Baltic Seas.</p>
<p>However, doing such an experiment in the Eastern Mediterranean Sea is very important for getting the “big picture” that we mentioned before. Since this sea is very poor in nutrients and DOC, by adding a massive amount of them, we can actually study what are the actual effects of this substance in the microbial food web. Therefore, Crete serves as a “Control” site for the JOMEX! Also, there are genuine ecological questions that can be answered, regarding the response of the microbes to such a pulse of “food” and, at the same time, to a reduction of the available light.</p>
<p>In order to answer those questions, the marine biologists in <a href="https://www.hcmr.gr/en/" target="_blank" rel="noopener noreferrer">HCMR</a> Crete, in collaboration with scientists from Italy, France, Denmark, Spain, Turkey and Netherlands applied many different assays. Cell counting (from viruses to copepods) and diversity (via metagenomics and phenotypic identification in the microscope), bacterial production, respiration, measurement of total, particulate and organic Carbon, inorganic nutrients, chlorophyll concentration, photosynthetic pigment analysis and so on.</p>

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![A-Brownification-experiment-in-Crete-Greece-image-3-scaled (1).jpg](https://storage.googleapis.com/aq-cms-content/A_Brownification_experiment_in_Crete_Greece_image_3_scaled_1_9adf63769c/A_Brownification_experiment_in_Crete_Greece_image_3_scaled_1_9adf63769c.jpg)

<div class="photo-credit">Photo credit: Iordanis Magiopoulos</div>
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<p><strong>So, did we find anything interesting?</strong></p>
<p>In fact, yes!</p>
<p>It seems that HuminFeed reduced light penetration (as someone could hypothesise by the term “brownification”) which affected negatively the strict autotrophic organisms (i.e. the organisms that need light to produce organic matter) such as cyanobacteria and diatoms. Also ciliates and copepods seem not to coup nicely with HuminFeed as their populations decreased significantly in numbers. On the other hand, bacteria were the happiest cells since they had enough organic and inorganic nutrients to consume. Also, dinoflagellates (which are known for their mixotrophic behaviour) seem to find a way to avoid this organic matter stressor.</p>
<p><strong>And why is this important?</strong></p>
<p>This data will help scientists of the AQUACOSM project to better evaluate the effects of episodic additions of DOC, nutrients and metals on the marine ecosystem. And also, since heavy rainstorms will become more and more common in the near future (“thanks” to Climate Change), scientists will try to get an idea of what may happen more and more often in the crystal-clear coastal waters of the Eastern Mediterranean.</p>
<p>For more information, you may contact Iordanis Magiopoulos <a href="mailto:iordanis@hcmr.gr">(iordanis@hcmr.gr)</a>.</p>

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![Brownmed dinner image](https://storage.googleapis.com/aq-cms-content/dinner_image_4_029a2784c4/dinner_image_4_029a2784c4.jpeg)

<div class="photo-credit">Credit: Iordanis Magiopoulos</div>
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A Brownification experiment in Crete, Greece

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An international mesocosm experiment (“BrownMed”) took place at the CretaCosmos mesocosm facility of the Hellenic Centre for Marine Research in Crete, Greece.

In the summer of 2021, in a respite from the restrictions of the pandemic, the team at the Aarhus University Lake Warming Mesocosm Experiment (LWME) managed to run a heatwave experiment with support from the EU H2020 project AQUACOSM-plus. The LWME has been running at the department of Ecoscience at Aarhus University since late 2013. The experiment was part of the AQUACOSM project and is now part of the AQUACOSM-plus network. It is also contributing data to a number of other national and international projects, not least PONDERFUL.

<p>In the summer of 2021, in a respite from the restrictions of the pandemic, the team at the <a href="/mesocosms/au-lake-mesocosm-warming-experiment-lmwe " target="_blank" rel="noopener noreferrer">Aarhus University Lake Warming Mesocosm Experiment (LWME)</a> managed to run a heatwave experiment with support from the EU H2020 project AQUACOSM-plus. The LWME has been running at the department of Ecoscience at <a href="https://international.au.dk/" target="_blank" rel="noopener noreferrer">Aarhus University</a> since late 2013. The experiment was part of the AQUACOSM project and is now part of the <a href="/aquacosm-plus" target="_blank" rel="noopener noreferrer">AQUACOSM-plus network</a>. It is also contributing data to a number of other national and international projects, not least <a href="https://ponderful.eu/" target="_blank" rel="noopener noreferrer">PONDERFUL</a>.</p>
<p>The experiment consists of 24 land-based mesocosms with 6 treatments (Figure 1) with 2 different nutrient levels crossed with 3 different temperatures. The project is designed to investigate how nutrient enrichment interacts with the warming associated with climate change and it has proved very valuable in this respect. However, climate change does not only change average temperatures but also lead to more frequent and intense heatwaves. This in turn will lead to more temporary stratification of shallow lakes and ponds – something that a few years ago was considered rare but is maybe more common than we think.</p>

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![Figure-1.-Design-Set-up.jpg](https://storage.googleapis.com/aq-cms-content/Figure_1_Design_Set_up_ef3a6b9ab8/Figure_1_Design_Set_up_ef3a6b9ab8.jpg)

<div class="photo-credit">Figure 1. The Lake Warming Mesocosm Experiment and a layout of the tank codes and treatments. © Tom Davidson & Eti Levi.</div>
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<p>To investigate how these heatwaves will affect the ecology and biogeochemical processes in shallow lakes and ponds we carried out a two-month experiment at the LWME: Here we simulated a heat-wave induced stratification event lasting two weeks, followed by two weeks of mixing; this four-week cycle was carried out twice, meaning the whole experiment lasted eight weeks.</p>
<p>After collecting the last ‘before samples’ on July the 6th, we turned off the mixing paddles and raised the heating elements of the tanks and turned up the heat to induce stratification in the 24 mesocosms for two weeks. There followed an intensive sampling campaign as whilst we have sensors to measure temperature and dissolved oxygen (both in the surface and bottom waters), pH and chlorophyll, all other samples were collected by hand. There was an extra challenge, as we needed to sample both surface and bottom waters of each mesocosm during the stratified periods. For this we used a purpose-built ‘Audet’ sampler, allowing us to draw samples up from the bottom waters without disturbing the stratification. This doubled the number of samples to collect compared with our ‘normal’ sampling regime. In total, over the 8 weeks, we sampled 6 times in the stratified phases (288 sampling units) and 8 times in the mixed phases (192 sampling units). We sampled a range of parameters including water chemistry, chlorophyll-a, greenhouse gas concentrations, methane bubble fluxes, dissolved organic carbon and the quality of the dissolved organic matter (cDOM and fDOM), bacterial abundance and composition, Microcystis abundance, plant abundance and zooplankton and there were additional studies looking at process rates of denitrification and DOM degradation. So we were kept very busy which you can see <a href="https://twitter.com/LakeGroupAU/status/1461598418904797184" target="_blank" rel="noopener noreferrer">here</a>. Luckily, we had great guest researchers from Germany, Estonia, Turkey, Kazakhstan and the USA to help with the experiment, which was made possible by a total of 127 TA days of funding from the AQUACOSM-plus project. The intensive effort was only possible thanks to such a great team (Figure 2) but also thanks to an excellent if sometimes a bit tough, experiment boss. We at the lake group AU would like to thank you all for such great efforts but also for making the experiment a lot of fun.</p>

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<div class="photo-credit">Figure 2. The bottom sampling device and some members of the crack sampling team. © Tom Davidson</div>
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<p>The huge number of samples collected means we are still working on the data and still have some time until the results are ready for publication. We are, however, happy to show through the plots of temperature and oxygen (Figure 3) from selected tanks that thermal stratification occurred and in some cases resulted in total anoxia of the bottom waters. We should be able to show clearly how stratification interacts with ecological status, nutrient enrichment and background temperature.</p>

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<div class="photo-credit">Figure 3. Plot from two of the mesocosms (A1 and H3) showing the effects of the stratification on the temperature and oxygen concentrations in the surface and bottom waters over the eight weeks of the experiment. © Eti Levi</div>
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Aarhus University Lake Warming Mesocosm Experiment (LWME) managed to run a heatwave experiment with support from the EU H2020 project AQUACOSM-plus

Long-term lake warming experiment meets short-term heatwave

In AQUACOSM-plus, we develop a low-cost, low-weight, and easily-transportable version of a mesocosm platform, which will allow effective installation in freshwaters over Europe-wide geographical and environmental gradients. The new platform system allows using mesocosms with various diameters and of two different types.

<p><strong>In AQUACOSM-plus, we develop one...</strong></p>
<p>Many systems for mooring mesocosms are very rigid, immobile and/or usually very expensive. This limits the capacity to investigate ecological and socio-economical impacts on various aquatic systems on regional to international scales, especially if mesocosm infrastructures are not available at these sites. Hence, it is important to develop a flexible and cost-effective system for mobile use in different locations, in a way to allow testing a wide range of ecological hypotheses under a variety of conditions. Such a mobile platform system should be of low weight, inexpensive, easy to assemble, flexible, small in pack size and stable.</p>

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![Figure1-cropped-2.jpg](https://storage.googleapis.com/aq-cms-content/Figure1_cropped_2_506c336b8f/Figure1_cropped_2_506c336b8f.jpg#right)

<div class="photo-credit">Figure 1: Different types of mesocosms: Pelagic (right) benthic-pelagic (left) © Maria Stockenreiter</div>
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<p>In <a href="/aquacosm-plus" target="_blank" rel="noopener noreferrer">AQUACOSM-plus</a>, we develop a low-cost, low-weight, and easily-transportable version of a mesocosm platform, which will allow effective installation in freshwaters over Europe-wide geographical and environmental gradients. The new platform system allows using mesocosms with various diameters and of two different types.</p>
<p>One type of mesocosms, the <strong>“pelagic”</strong> ones, will enclose the pelagic water: the conical bottom of the bag will be heat-sealed and include a suspension attachment for weights (Fig. 1).</p>
<p>The other type of mesocosms, the <strong>“benthic-pelagic”</strong> ones, consists of the same materials but also encloses the sediment so that a benthic-pelagic exchange can be possible (Fig. 1).</p>
<p>The raft system, although already successfully tested (see Fig. 2), will be further developed so that sensor systems can be easily attached while at the same time regular sampling and access with different sampling equipment are also possible. This further extends the flexibility of the platform system and its potential use for testing broad ecological questions.</p>
<p>For further information, please check out our <a href="https://www.youtube.com/channel/UCUJUY-IsOKVVdR6lUGPG5sQ" target="_blank" rel="noopener noreferrer">AQUACOSM-plus YouTube channel</a> and the video: <a href="https://www.youtube.com/watch?v=9zvCKzVNIBs&amp;t=68s" target="_blank" rel="noopener noreferrer">how to construct low-cost mesocosms</a>.</p>

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![Figure2.jpg](https://storage.googleapis.com/aq-cms-content/Figure2_c11295b31d/Figure2_c11295b31d.jpg)

<div class="photo-credit">Figure 2: Test of the low-weight mesocosm platform construction ©Maria Stockenreiter</div>
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In AQUACOSM-plus, we develop a low-cost, low-weight, and easily-transportable version of a mesocosm platform.

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