AnaEE Science Conference 2026

Impacts of warming and seawater intrusion on microbial loop components and carbon dynamics in coastal ecosystems: a mesocosm study

30 Sept 2026, 09:15

15m

Palais de l'Europe

Oral Session 4: Experimental Approaches to Global Change Ecology Session 4: Experimental Approaches to Global Change Ecology

Speaker

Archana Manjunath (Middle East Technical University- Institute of Marine Sciences)

Description

Coastal lake ecosystems are vulnerable to climate warming and consequent salinity changes driven by seawater intrusions. Microbial loop is an important component of coastal food webs and plays a crucial role in carbon cycling within these lakes. However, little is known about how microbial communities respond to environmental stressors associated with climate change. Bacteria, heterotrophic nanoflagellates, and ciliates are key components of the microbial food web, transferring carbon and energy to higher trophic levels. Previous studies suggest that dissolved organic carbon (DOC) processing through the microbial loop may influence carbon sequestration which in turn regulates the global climate.

This study aims to assess the individual and combined effects of warming and salinization on microbial communities and their trophic interactions using mesocosm experiment, and to evaluate their effects on dissolved and particulate organic carbon fractions (DOC and POC). A factorial experiment was conducted at METU-IMS over a total period of 75 days, using six treatments comprising three seawater intrusion treatments (4, 7, and 10 ppt final salinities) and two temperature treatments (ambient and +2.5°C). Twenty-four high-density polyethylene mesocosm tanks (5 m³) were used, each equipped with a wavemaker, temperature and oxygen sensors, and an automated logging system. Half of the mesocosms were fitted with glass heaters controlled by a microprocessor-based system to maintain the warming treatment. Bacterial abundance was quantified using flow cytometry, while phytoplankton biomass was estimated from chlorophyll-a (Chl-a) concentrations measured spectrophotometrically on a fortnightly basis.

Preliminary results indicate that salinity is a strong driver of bacterial abundance, Chl-a, and POC (p < 0.001). Warming had a weaker but significant effect on bacterial abundance before salinization (p < 0.05), and significantly affected DOC following salinization (p < 0.05). A significant interaction between warming and salinity was detected only for DOC (p < 0.05). These findings contribute to our understanding of ecosystem responses to climate change and may help inform future management and conservation strategies for coastal lake ecosystems.