The prokaryotic community of a flow regulated lagoon

Fabio De Pascale¹Greta Battaggia¹Riccardo Schiavon²Elisa Camatti³Florencia Mohamed¹Chiara Facca⁴Alessandro Vezzi^1*

• ¹Department of Biology, Universita degli Studi di Padova, Padua, Italy
• ²BMR Genomics, Padua, Italy
• ³Istituto di Scienze Marine Consiglio Nazionale delle Ricerche, Venice, Italy
• ⁴Universita Ca' Foscari Dipartimento di Scienze Ambientali Informatica e Statistica, Venice, Italy

Microorganisms play a fundamental role in all the environments in which they live, including coastal areas. Although they occupy a small portion of the Earth's surface, coasts support vital ecosystem services and host a wide variety of life forms, including humans. In the coming decades, these ecosystems will be subjected to intensifying pressures due to climate change, sea level rise and the mitigation measures implemented by coastal communities. In the Venice Lagoon, one such mitigation measure is the MOSE system, a large-scale infrastructure designed to protect the city of Venice from extreme tidal events which regulates water exchange with the sea. Although conceived before the current understanding of the climate crisis, MOSE is now expected to be activated frequently, potentially resulting in prolonged closures of the lagoon from the sea. There is a significant knowledge gap regarding the ecological consequences of this restricted seawater exchange, particularly on microorganisms that inhabit transitional environments such as lagoons. To address this gap, the present study analyzes prokaryotic communities in both benthic and pelagic compartments of the Venice Lagoon using 16S rRNA gene sequencing. Sampling was conducted every three months at five stations over a thirty-month period. The results provide a detailed characterization of the microbial communities associated with surface water and sediment, offering a valuable baseline for future studies assessing the impact of highly regulated coastal environments.