Last Updated:
29/06/2020 - 08:49


Dissolved Organic Carbon(DOC)– Impacts of Pulsed DOC Disturbance in shallow freshwater lakes

Sampling at the Mesocosm System

Time and Location

The 2019 mesocosm experiment was conducted at METU Mesocosm System (aquatic) at METU Experimental Lake (Lake Golet) between 20 June – 26 July 2019.  


The primary objective of the experiment is to investigate the responses of the system to dissolved organic carbon (DOC) pulses from terrestrial sources as a part of Joint mesocosm experiments of Aquacosm (JOMEX). 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 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


We investigated the response of different plankton communities to a pulsed DOC disturbance and followed the reaction of the system after this strong disturbance in terms of resistance, resilience and recovery (i.e. ecosystem stability concept). We hypothesized that 1) DOC will cause compositional and/or functional shifts in the communities following resistance, resilience, recovery stages, 2) the effects of these shifts will be transferred throughout the food web, 3) systems with high initial functional diversity will have a faster recovery towards initial conditions

team discussing

Experimental Set-up

For this purpose, METU Mesocosm System at Lake Golet was used with 16 mesocosms with 4x4 design. In order to simulate the effects of terrestrial DOC, two different DOC source was tested: (i) Local DOC extracted from Local Alder Tree Leaves to test the nutrient effect of terrestrial DOC on freshwater systems (ii) Humin Feed (Humintech GmbH), which is a highly standardized product that is used to test light limitation effect of DOC on freshwater systems. Therefore, Mesocosm System included 16 mesocosms with 4 Controls, 4 replicates including a highly standardized DOC source (4 ppm HF) and 4 replicates including a local, more site-specific DOC source (8 ppm Local DOC) and 4 replicates including both sources (4 ppm HF and 8 ppm Local DOC).  

With the aim of understanding whole-ecosystem responses, we investigated physiochemical parameters, microbial community structure (16S-18S rRNA), microbial loop community dynamics (bacteria, HNF, ciliates), phytoplankton and zooplankton community structure, lake metabolism and lake stoichiometry. 

DOC preperation

International Cooperation

We had TA Access teams with projects MicroMESO, PperDOC, ECMMETU2019 and AlloEcoMetry, comprising scientists from Greece, Turkey, Brazil, Croatia and Ireland.

team dinner

Team MicroMESO:

Team Leader

Assist. Prof. Dr. Emmanuel (Manolis) LADOUKAKIS, Department of Biology, University of Crete, Greece

Team Members

Assoc. Prof. Dr.  Efe Sezgin, Department of Food Engineering , Izmir Institute of Technology 

PhD student Marilena Parakatselaki, Department of Biology, University of Crete, Greece

MSc student Hüseyin Yiğit Şahin, Ege University & Aegene Biotechnology Inc., Turkey

Team PperDOC

Team leader

Dr. Kemal Ali Ger, Universidade Federal do Rio Grande do Sul-UFRGS, Brazil 

Team members

Prof. Dr. Maria Spoljar, Department of Biology, University of Zagreb, Croatia

Prof. Dr. Sanja Gottstein, Department of Biology, University of Zagreb, Croatia

MSc Student Claudia Fiorentin, Department of Biology, University of Zagreb, Croatia 

Team ECMMETU2019

Team leader

Dr. Mikkel Rene Anderson, Dundalk Institute of Technology, Ireland 

Team members

Research Assistant Pınar Kavak Gulbeyaz, Department of Environmental Engineering, Hacettepe University, Turkey

Prof. Dr. Nusret Karakaya, Department of Environmental Engineering, Bolu Abant Izzet Baysal University, Turkey

Team AlloEcoMetry

Team leader/member

PhD student Maria Caldero Pascual, Dundalk Institute of Technology, Ireland