Microbial and environmental interactions of the 2021 mucilage event in the Sea of Marmara

Date

2026-01-01

Author

Karahan, Arzu
Deliceırmak, Selin
Esti, Mertcan
Kalkan Tezcan, Evrim
Öztürk, Esra
Örek, Hasan

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This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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In 2021, the Sea of Marmara (SoM) experienced an extensive mucilage event that severely impacted marine ecosystems. While nutrient enrichment, temperature anomalies, and anthropogenic stressors are known contributors to such events, the microbial and environmental mechanisms remain unclear. Here we combined environmental DNA (eDNA) metabarcoding of 16S, 18S, and ITS regions with in situ physicochemical measurements and historical data to characterize microbial communities and environmental conditions across 39 samples from 24 stations during and after the mucilage event. Our results revealed that mucilage formation was associated with a distinct microbial community shift, including the dominance of Dinophyceae, diatoms, Chytridiomycota, and exopolymer-degrading bacteria such as Polaribacter and Lentimonas . Parasitic fungal genera like Cladosporium , Candida, and chytrids (phylum Chytridiomycota) likely contributed to bloom collapse and organic matter accumulation. In contrast, post-mucilage samples exhibited increased abundance of Synechococcus , Halteria , Actinobacteria, and Ilumatobacteraceae , indicating microbial recovery. Anomalous patterns at the Ergene discharge station, including the dominance of Cutaneotrichosporon debeurmannianum , underscored the influence of localized pollution on community structure and potential health risks. These findings highlight that microbial community imbalance—often linked to nutrient fluctuations—plays a key role alongside physicochemical factors in shaping mucilage dynamics, indicating the importance of integrated microbial and environmental monitoring in eutrophication-prone marine systems. Understanding microbial and environmental shifts during the 2021 outbreak will help prevent future outbreaks.

Subject Keywords

eDNA, Eutrophication, Marine fungi-protists, Microbial community dynamics, Mucilage, Sea of Marmara

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https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=105022472162&origin=inward
https://hdl.handle.net/11511/117488

Collections

Graduate School of Marine Sciences, Article