Combining eDNA and Image Analyses to determine the impacts of Warming and Dissolved Organic Carbon (DOC) Disturbance on Freshwater Communities

Shallow lake ecosystems are particularly prone to climate-driven disturbances, including warming and pulses of dissolved organic carbon (DOC) loading. Climate models predict a 1.1–6.4°C increase in temperature during the 21st century, alongside altered precipitation patterns and flush floods. In lakes receiving floodwaters, excessive DOC inputs stimulate heterotrophic bacterial production, shifting dominance from photosynthetic production to the microbial loop (ML). Warming may interact with DOC flux, potentially intensifying these effects. Given the limited understanding of these drivers on biodiversity and ecosystem functions, an in situ mesocosm experiment (4x4) was conducted at METU Mesocosm System I, Türkiye, from 05 July to 05 August 2021. Treatments included DOC (8 ppm), 4°C warming (H), combined warming and DOC (HD), and controls (C). Traditional microscopy, FlowCAM, and eDNA techniques were used to examine bacterial, ciliate, phytoplankton, and zooplankton communities. We hypothesized that elevated temperature and DOC (i) would synergistically increase bacterial biomass and shift community structure towards species adapted to high carbon and temperature, (ii) would influence ciliate biomass, composition, and size through “trophic interactions” with changing zooplankton dynamics, and (iii) would promote mixotrophs in the phytoplankton while reducing overall biomass due to DOC’s light-limiting effects. These three different methods provided complementary results  to be thoroughly discussed in the presentation.

Presentation Preference: Oral

Primary Presenter: Gülce Yalçın, Middle East Technical University; Ecosystem Implementation and Research Center (ygulce@metu.edu.tr)

Authors:

Gülce Yalçın, Ecosystem Research and Implementation Center, Middle East Technical University, 06800, Ankara, Ankara, Turkey  (ygulce@metu.edu.tr)

Dilvin Yıldız, Earth System Science, Graduate School of Natural and Applied Science, Middle East Technical University, Ankara, Turkey  (dilvinim@gmail.com)

Işılay Çelik, Biotechnology Institute, Ankara University, 06135 Ankara, Turkey  (isilaycelik12@gmail.com)

Joe Taylor, UK Centre for Ecology & Hydrology (UKCEH), Wallingford, Oxfordshire OX10 8BB, UK  (JoeTay@ceh.ac.uk)

Emre Keskin, Evolutionary Genetics Laboratory (eGL), Department of Fisheries and Aquaculture, Faculty of Agriculture, Ankara University, 06135, Ankara, Turkey  (amfibiksubstans@gmail.com)

Özge Eyice, School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK  (o.eyice@qmul.ac.uk)

Erik Jeppesen, Ecoscience, Aarhus University, 8000 Aarhus, Denmark  (ej@ecos.au.dk)

Meryem Beklioğlu, Limnology Laboratory, Biological Sciences Department, Middle East Technical University, 06800, Ankara, Turkey  (meryem@metu.edu.tr)