EU network of mesocosms facilities for research on marine and freshwater ecosystems open for global collaboration.

METU Mesocosm System

METU Mesocosm System participate in the Joint Mesocosm Experiments – JOMEX: Systems responses to recurrent pulses of dissolved organic carbon (DOC). Project lead: Meryem Beklioğlu, Gülce Saydam and Dilvin Yıldız. 01 May-31 July 2019.

Timing of the METU Mesocosm System experiment: The large-scale mesocosm experiment is planned for eight weeks between 1 May- 31- July. In month May preparation for experiment will be carried out. The experiment will be conducted during following 8 weeks and after-work, where all participants are expected to participate as an integral part of the application period.

We encourage a wide range of Transnational Access (TA) users to apply: Including public authorities, technological partners, and research or teaching institutions. As we plan to observe whole-ecosystem responses, everyone with expertise or interest in microbial (including bacteria, hetetrophic flagellates and ciliates) and plankton communities (including both phytoplankton and zooplankton) or pelagic processes is welcome to apply. We specifically invite researchers and trainees to work with in general microbial loop, phytoplankton, and zooplankton community as well as especially worked with bacterial and phytoplankton community structures (16SrRNA), pigment composition of phytoplankton (HPLC), phytoplankton nutrient limitation assays etc. A total of at ca. 220 person days will be allocated to external users through Transnational Access provided under AQUACOSM for 2019. It is anticipated that AQUACOSM will support stays of at least  8 to 10 persons.

If you are interested, please contact us (, and for further details)

Introduction to the project: The study aims at investigating the systems responses to dissolved organic carbon (DOC) pulses from terrestrial sources as a part of Joint mesocosm experiments of Aquacosm (- JOMEX), which will demonstrate the ability of the Aquacosm consortium to perform joint directed experiments along gradients from the Arctic to the Mediterranean and from freshwater to full marine systems. Such joint experiments will allow disentangling site-specific effects from general effects of experimental manipulations and thereby increase its predictive power. Through the changes in precipitation pattern in the eastern Mediterranean lately, winter snow packs have been largely replaced with early and late spring heavy rains and consequent of intensive flush floods.  Such conditions increase transport of matter from terrestrial environments into aquatic systems is a highly relevant aspect of global change even in Eastern Mediterranean in Turkey;

Consequences DOC pulses for ecosystem dynamics are still poorly understood. The response to the disturbance with a pulse nature should depend on the composition of plankton communities and their history to the exposure to terrestrial DOC pulses in terms of frequency and strength. It is therefore expected to have strong site-specific differences in the response to a defined DOC pulse especially in lakes where DOC pulse is not a regular type of disturbance. To investigate the effect sizes of site-specific and general responses we will have 12 mesocosms, 4 controls, 4 replicates including a highly standardized DOC source and 4 replicates including a local, more site-specific DOC source.  We will follow the responses of bacteria, phytoplankton and zooplankton to the DOC pulses twice. Once in the beginning of the experiment and then 3 weeks after second pulse of DOC will be given to analyse the resistance, resilience and recovery of the communities. The same mesocosm experiments will be carried out with only single pulse of DOC in European waters, from freshwater to marine systems and from Arctic to Mediterranean environments to evaluate general responses along the latitudinal gradient across the different aquatic domains.

We will investigate the response of different plankton communities to a two DOC pulses and will follow the reaction of the system after this strong disturbance in terms of resistance, resilience and recovery. We hypothesize that 1) systems, which experience regular disturbances by DOC pulses are more resistant to such a pulse and 2) second pulse may create a certain level of resistance capacity; 3) systems with high initial functional diversity will have a faster recovery towards initial conditions

Twelfe mesocosms with (2 meters height and 1.2 m diameter) will be filed by pumping water in an oligo-mesotrophic lake. Great care will be taken to fill control and treatment mesocosms with exactly the same method and at the same time to ensure a maximum initial community similarity between all mesocosm.  We will perform the experiment with twice pulses of DOC, the concentration will be 2 mg/L with a highly standardized DOC form (HuminFeed; HUMINTECH, Grevenbroich, Germany) and with a local DOC source. The first pulse of DOC will be followed for 3 weeks and then the second pulse will be added and followed again.

Measurements: We will follow the transient dynamics of a plankton community after a DOC pulse. Bacterial, phytoplankton and zooplankton parameters in terms of community function and community composition will be measured. We will characterize the resistance of the different communities to the DOC pulses and hypothesize systematic differences. Measurements that are central to test the hypotheses will be performed at all sites in comparable ways; additional measurements (extended parameter list) will be performed (supported by other funds and cooperation between partners) and will allow site-specific further insights into experimental dynamics. All measurements will follow described SOP procedures assembled within AQUACOSM

Abiotic environment measurements

  • Temperature: daily
  • pH: daily
  • Oxygen: daily
  • Conductivity: daily
  • Light (µmol PAR): daily

Nutrients, total & particular organic carbon (TOC, POC), particular organic nitrogen (PON) measurements

  • Total phosphorus & dissolved inorganic phosphorus (TP, DIP): twice a week
  • Nitrate (NO3), nitrite (NO2), ammonium (NH4): twice a week
  • Particulate organic nitrogen (PON): twice a week
  • Silicate (Si): twice a week
  • Particulate organic carbon and total organic carbon (POC, TOC): twice a week

Bacterial parameter measurements

  • Bacterial abundance (fluorescence based methods: FlowCytometer/ fluorescence microscope): twice a week

Extended parameter list:

  • Bacterial community structure (16SrRNA)
  • Bacterial production

Phytoplankton parameter measurements

  • Phytoplankton chlorophyll a (extracted): daily
  • Phytoplankton community structure (Lugol fixed samples for microscopy): at start, middle and end day.

Extended parameter list:

  • FlowCytometry counts
  • Chlorophyll a fractionated (0.2, 2, 10 µm filter size)
  • Phytoplankton community structure (16SrRNA)
  • Pigment composition of phytoplankton (HPLC, Wright et al. 1991)
  • Size distribution (Cell counter)

Zooplankton measurements

  • Microscopic analyses of microzooplankton (Lugol samples):
  • Mesozooplankton samples (> 250µm), microscopic analyses of abundance and community composition:
  • (, for measurements were SOPs not necessarily exist relevant references are given.

Microplastics – Evaluate negative effects of microplastics in shallow freshwater lakes. Project lead: Meryem Beklioglu. 01/06-30/09

The planned mesocosm experiment at METU will start in June 2018 and run until September. We will start preparing the sediment acclimation to low P level in January with more intense preparatory work in April and May 2018. Users approved for AQUACOSM TA are welcome to participate in the proposed experiment as well as in the preparation phase. We offer at least 210 person-days to external users during year 2018 of the AQUACOSM Transnational Access provision. We aim for 6 persons staying for 35-40 days in 2018.

Introduction: Approximately 311 million metric tons (MT) of plastic were produced in 2014 alone, and production is steadily increasing each year. Up to 10 % of the plastic produced each year worldwide ends up in the aquatic environment, where it persists and accumulates. Plastic does not last forever, and the aquatic environment is suitable for plastic degradation. Physical, chemical, and biological processes are fragmenting the original plastic pieces of litter, turning the aquatic environment into a soup of microplastics. The mass of plastic in certain parts of the ocean is already surpassing the mass of plankton, and in the relatively near future, when the process of plastic degradation reaches its peak, the abundance of plastic micro and nanoparticles will be considerably greater than the count of plankton.

Current scientific research on microplastics is predominantly focused on marine environment and on individual species, while freshwater studies, including mesocosm studies, are lacking significantly. To the best of our knowledge, only 2 mesocosm studies were performed in the past in which aquatic organisms were exposed to microplastics. However, both of the studies were performed in the marine environment, and in fact can be characterized as an outdoor microcosm studies (10 L containers) rather than real mesocosm studies. Since freshwater systems also contain copious amount of microplastics which can interact with virtually all freshwater organisms that have shown in some of the laboratory experiments. There is an urgent need to perform world first freshwater, environmentally realistic, outdoor mesocosm microplastics study to understand the fate of microplastics.

Our underlying hypothesis is that the exposure to environmentally relevant concentration of microplastics in water and sediment will cause; decline in the biomass of organisms in the food chain (e.g. phytoplankton, zooplankton, invertebrates andfish); reduce the predatory evasion capabilities of zooplankton from fish; cause changes in the community structure of both the zooplankton and phytoplankton; and induce pathomorphological changes in the mentum apparatus of Chironomus spp. – a sentinel benthic macroinvertebrate.

The main objective of this study is to evaluate negative effects of microplastics in shallow freshwater lakes by exposing water and sediment of mesocosms simultaneously to the environmentally relevant mixture of various microplastic polymers (cocktail of microplastics) and not to individual microplastic types (current trend in the single species laboratory experiments). Performing a mesocosm study with a mixture of microplastic is very important as in the nature we do not have freshwater systems that are contaminated only with a single plastic polymer. Different types of microplastic have different densities resulting in a different distribution patterns in the aquatic ecosystem while many aquatic organisms move/migrate throughout the day and may interact with different microplastic polymers from different compartments of the ecosystem. On the other hand, benthic burrowing organisms are able to interact only with the high-density microplastic polymers. Furthermore, different types of microplastic polymers may induce different toxicity. Thus, in order to truly understand the negative effects of plastic littering on freshwater ecosystem we have to test for those effects using the relevant littering mixture of plastic polymers.

Therefore, we propose a mesocosm experiment with an environmentally relevant concentration of microplastic in all of its compartments (surface, water column, and sediment) of 0.007 g microplastic per m2 of surface water; 2 g microplastic per m3 for water column; and 8 microplastic g per m2 of sediment all mixed in a single mesocosm container (in 4 replicates). An additional 10 X concentration exposure and 0 X (control) group will be setup as well. For this purpose, we will use a different buoyancy microplastics of 0.95; 1-1.01; and > 1.05 (pre-mixed with sediment) gcm-3 plastic polymers for surface, water column, and sediment, respectively. Based on the available freshwater literature on the composition of microplastics in various compartments we propose that the sediment layer of microplastics in the mesocosm exposure consist of: 45% polyethylene; 20 % polystyrene; 15% poplypropylene; 10% polyamide; and 10 % polyvinylchloride. On the other hand surface layer will be exposed to 50% polyethylene; 40% poplypropylene; and 10% polystyrene. For the water column there are really no reliable data for freshwater, however based on the required density of the plastic to maintain buoyancy in freshwater this should predominantly be polyethylene with 1-1.01 gcm-3 density, which we will use in the experiment for the water column.

Proposed methodology: We propose to use 12 cylindrical-shaped mesocosms (8 experimental + 4 control), maximum volume 1360 L each, on a floating platform in the middle of a lake. Microplastics will had to be added immediately to the sediment during the mesocosms setup, while the water surface and water column microplastics will have to be added later when turbidity levels return to normal and after the acclimation period of zooplankton. All measurements will be performed weekly for 4 weeks. The first measurement will be performed on day 0 of the experiment immediately after the addition of water column/ water surface microplastics. At each sampling event, turbidity, dissolved oxygen, water temperature, pH, total nitrogen, nitrite, nitrate, un-ionized ammonia, soluble reactive phosphorous, particulated reactive phosphorous, total phosphorus, photosynthetically active radiation (PAR light penetration), Chl-a, zooplankton biomass, phytoplankton biovolume and community structure, zooplankton: phytoplankton ratio, chironomids biomass and mentum deformations will be measured. After 4 weeks, fish will be added in order to determine the difference in predatory pressure of fish on zooplankton in microplastic contaminated mesocosms vs controls. After the addition of fish measurements will be taken again weekly for the next 4 weeks. At the end of experiments all fish will be collected alive from the mesocosms and transferred to the lab where they will be kept for an additional 24 hours allowing them to defecate any microplastic which they ate immediately before the collection. After 24 hours fish will be euthanized, organs dissected and checked for microplastics accumulation. Plastic accumulation will be routinely checked in zooplankton as well during each sampling. Furthermore, there will be serious of additional laboratory experiments have been planned to test predator evasion capacity of zooplankton and changes in the mentum apparatus of Chironomus spp at different concentrations of microplastic types.

METU Mesocosm System
Legal name of organisation
Middle East Technical University (METU)
Organisation address

Orta Doğu Teknik Üniversitesi (ODTÜ), Middle East Technical University (METU), Üniversiteler Mahallesi, Dumlupınar Bulvarı No:1 06800 Çankaya Ankara/TURKEY, 06800

Primary contact information (PI)

Prof.Dr. Meryem Beklioğlu

Years of Mesocosm Experiments
2011, 2012
Description of Facility
Controlled Parameters

water depth and nutrients (both TP and TN)

Research Topics

Role of water level on ecosystem processes (e.g. C and  N) as well as impact of food additives (TiO2) on food web structure and ecosystem processes

Facility location(s)
Primary interests

Role of hydrological alteration on ecosystem structure and function of shallow lakes

Specialist areas
Source of Information
Photos of experiments/installations


Infrastructure (short name)
METU Mesocosm System
Installation (short name)

METU Campus in Ankara, Turkey

Coordinates / (routes, areas if non-static)

39°53’17.39″ N 32°47’2.99″ E (DMS)

Water / environmental conditions

freshwater, alkaline, both nutrient poor and rich

Depths / bottom / surface
1 and 2 m. 10 cm sediment which is composed of 90% washed sand and 10% natural sediment from a nearby oligotrophic lake. Largely artificial sediment is chosen to prevent sediment acting as either source or sink.

The mobile METU Mesocosm System is based at Middle East Technical University (METU) and is normally installed in a lake on campus close to the METU Limnology Laboratory (1 km), but can be moved to other locations. It consists of 16 cylindrical (1.2 m diameter) 4-mm thick, robust fibreglass tanks either 1.2 m or 2.2 m tall (Fig. 6.5.1). The upper ends of the tanks extend 20 cm above the water surface and are attached to a wooden free-floating pontoon carried by 8 large (120 L) plastic barrels. The tanks are arranged in 2 rows divided by a boardwalk. The pontoon is anchored at only one end and thus functions as a wave breaker and landing point for boats irrespective of the wind direction. The mesocosms were established in 2011 for a pan-European experiment within an EU-funded project (REFRESH) to investigate impacts of climate-driven changes on lake hydrology and eutrophication. Water in the mesocosms can be continuously circulated during experiments using electrically powered pumps to simulate a shallow, fully mixed lake. Sediments can be added. To standardise initial conditions and promote a diverse flora and fauna, inoculation with plankton, sediment, aquatic plants and fish is possible.

The Limnology Laboratory operating the METU Mesocosm System is equipped with sampling gear and analytical instruments (e.g. auto-analyser, various microscopes) and a walk-in climate room. Moreover, METU has a central laboratory facility equipped with an elemental analyzer to determine particulate C and N, an ICP-MS to analyse trace elements, a Fourier transform infrared spectrometer FTIR), modern molecular-biology laboratories, etc.

Fig. 6.5.1. The METU Mesocosms System with a wooden pontoon (left) and dimensions of mesocosms of 2 different heights and volumes (right).

Instruments / sensors / equipment
Modality of access

A total of at least 630 person-days will be allocated to external users during years 2-4 of the AQUACOSM Transnational Access provision. A minimum access for 9 persons is envisaged for 20 days each year. External users will be prioritised for using the mesocosms throughout the AQUACOSM TA activities. To maximise scientific output, efforts will be made to integrate the AQUACOSM TA activities into other projects at the facility. Access to the facility by international scientists has already been rewarded by a publication in a leading ecotoxicological journal.

Unit of access
What is available and when
What service and support facilities are available

Services currently offered by the infrastructure: Users will have access to the full range of laboratories and instrumentation at the METU Mesocosm System and Limnology Lab. The mescosm set-up provides an excellent opportunity to study effects of water-level changes of lakes, which are induced through evaporative water loss in two different water depths, simulating shallow lakes in warm climates. Such studies on the effects of drought can be combined in factorial experiments with eutrophication or toxic chemicals on trophic structure and dynamics, the fate of nutrients or toxic chemicals, organisms ranging from bacteria to fish, ecosystem metabolism, adaptation and microevolution. Users are encouraged to cooperate with local scientists to take advantage of specific expertise on the effects of hydrological changes in shallow lakes.

Support offered under AQUACOSM: Users will be given access to the mesocosm facility as well as the full range of laboratories and instrumentation available at the METU Mesocosm System and METU Limnology Lab. This includes physical, logistic, technical and scientific support. AQUACOSM scientific staff and the task leader will further assist users with supervising and training as well as providing assistance throughout the stay.

Special rules